World Fertilizer July/August 2021 issue by PalladianPublications

MAGAZINE | JULY/AUGUST 2021

CONTENTS 03 05 10

Comment World News Making A Mark In MENA

Let’s Get Digital Dr Katja Poschlad and Dietmar Wagner, thyssenkrupp Uhde, Germany, and Dr Stephan Körner and Dr Sophie Wei, thyssenkrupp Analytics & AI, Germany, explore the digital solutions available to fertilizer plants.

Gordon Cope, Contributing Editor, discusses the state of the fertilizer industry in various MENA countries, the challenges faced by the region and current efforts to tap into existing resources.

he Middle East and North Africa (MENA) region is home to hundreds of millions of people and a thriving agricultural sector. When it comes to domestic fertilizer production, however, it is underrepresented, despite possessing the natural resources to address this deﬁciency. Fortunately, many countries in the region are moving to tackle the issue with a variety of projects; a multi-country journey highlights home-grown initiatives.

Morocco

Gordon Cope, Contributing Editor, discusses the state of the fertilizer industry in various MENA countries, the challenges faced by the region and current efforts to tap into existing resources.

Africa holds the world’s largest phosphate deposits, with total reserves at approximately 50 billion t. Morocco has 70% of that total – approximately 35 billion t – and thanks to state-owned OCP, the country is the world’s second largest producer of phosphate, after China. As part of its goal to supply affordable fertilizer to other African nations, OCP is working with the Nigerian government and industry associations to develop the country’s fertilizer manufacturing. Part of the plan is to construct a 750 000 tpy ammonia plant in Nigeria; OCP will also supply up to 1 million tpy of phosphate to create blends for domestic farm consumption. The initial plan calls for ﬁrst production in 2025. Morocco also holds abundant deposits of potash. In March 2021, Emmerson PLC announced it was close to launching its Khemisset potash project in northern Morocco. The UK-based company is seeking to develop an estimated 537 million t of potash with an average grade of 9.24% potassium oxide (K2O). Output from the mine would average 735 000 tpy of K60 muriate of potash (MOP), and 1 million tpy of de-icing salt. The project has numerous

DIGITAL

ﬁnancial advantages: it is relatively shallow, at 450 m, and because it has no aquifer there is no cost to dewater shafts. It is the closest producer to major potash importer Brazil, as well as key European markets. Emmerson expects to break ground in late 2021, with ﬁrst production two years later.

Israel Israel is leveraging industrial uses for natural gas after the discovery of major offshore ﬁelds in the Mediterranean. In late 2020, Haifa Group chose Saipem to build an ammonia plant at its Mishor Rotem industrial site in the Negev desert. The US$200 million plant will produce approximately 100 000 tpy of ammonia using Haldor Topsoe technology, and the output will primarily be used to make potassium nitrate fertilizer. Construction is expected to take three years.

Dr Katja Poschlad and Dietmar Wagner, thyssenkrupp Uhde, Germany, and Dr Stephan Körner and Dr Sophie Wei, thyssenkrupp Analytics & AI, Germany, explore the digital solutions available to fertilizer plants.

ne key issue concerning the changing of the world that is under focus, apart from climate change, is the move towards a much more digitalised world. To help with this transition, thyssenkrupp Uhde (tk Uhde) has been developing several digital products. There are two major areas that these solutions address: handling of big data and using a digital copy of a real plant in order to help continuously improve the performance of the plant. The beneﬁts of such digital solutions for the performance of the plant are explained in this article.

Eritrea Danakali continues to advance its Colluli potash project in Eritrea. In late 2020, the Australian-based company announced it had successfully completed assessment work on the solar and wind energy potential of the proposed open pit mine, conﬁrming that these renewable energy resources could be incorporated into future generation power in order to achieve a zero-carbon footprint. The project is a 50:50 joint venture (JV) between Danakali and the Eritrean National Mining Co. (ENAMCO). Located 230 km southeast of Eritrea’s main port of Massawa, reserves have been estimated in excess of 1 billion t of 11% K2O. Colluli has been divided into two phases: Module I will have a capacity of 472 000 tpy of sulfate of potash (SOP), and Module II will double capacity to 944 000 tpy. The project is expected to be completed around 2023.

Data analysis Data analysis consists of four main steps, each of increasing complexity. The ﬁrst step is descriptive; it summarises the condition of the plant and events that occurred. To achieve this, data from various sources has to be integrated and processed. This includes operating data, e.g. from a distributed control

system (DCS), maintenance information and laboratory analysis. The company’s digital infrastructure allows for the integration and processing of data from these sources by transferring it into the thyssenkrupp Industrial Internet of Things (IIoT) cloud, using its data logger and a secure internet connection. Typical tools in the first step of data analysis are statistical analysis and applications for data visualisation. The second step is a diagnosis: why did a specific event happen in the plant? In this step, the company determines the root causes, finds hidden correlations or identifies characteristic patterns in the operating data. The objective of the next step is to predict what will happen in the plant in case no action is taken. Predictive models for forecasting and preemptive failure diagnosis are important for this step. Advanced data analysis tools and machine learning can also be applied.

Joan Riaza, Kao Chemicals Europe, Spain, shows that identifying the main reason for dust formation in each individual occurence is crucial to determining the best solution.

Process Improvement At The Steam Valve David C. Nelsen, REXA, Inc., USA, explains why plant engineers should upgrade steam turbine governor control valves to optimise control of turbomachinery.

Tackling Dust Formation, Case-By-Case

The Importance Of Housekeeping Philip J. Parsons, BakerRisk, USA, identifies common hazards that can contribute to catastrophic dust fire and explosion events, and emphasises the importance of a robust dust hazard analysis strategy.

The Evolution Of HTHA Detection Brian E. Shannon and Ronald T. Nisbet, HSI Group, Inc., USA, consider the work and conclusions of a Joint Industry Project established to improve HTHA detection methods.

Probing For HTHA Daly Souissi, Olympus, Canada, explores a new strategy for HTHA inspection.

Optimising The Sustainability Of Wastewater Treatment Alissa Pallagrosi, Andrea Carotti, David Lehmann and Joseph Lehmann, Saipem, look at the development of electrochemical technology designed to remove ammonia and urea contaminants from fertilizer plant process wastewater.

MAGAZINE | JULY/AUGUST 2021

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hen Belarus’s President Alexander Lukashenko made the decision in May this year to divert a passenger flight carrying regime critic Roman Protasevich to Minsk, it seems unlikely he was considering the effect his act of high-altitude piracy could have on the country’s potash industry. The diversion – on the grounds of a (fabricated) bomb threat – and subsequent arrest of Protasevich caused outrage in Western diplomatic circles. The initial rhetoric coming from EU leaders pointed towards heavy sanctions on Belarus’s potash industry, raising concerns that European customers would soon have to start sourcing supplies from elsewhere. On 24 June, the EU decided to ban imports of Belarusian potash that have a potassium content of less than 40%, or greater than 62% (keep these figures in mind). Industry analysts have concluded that the sanctions, as they stand, will have little impact. VTB Capital, a Russian investment bank, noted: “The measures do not cover the key Belarusian potash export, potassium chloride, which is 40 – 62% K2O by weight, and accounts for 80% of the country’s supplies to the EU.”1 Humphrey Knight, an analyst at CRU, called the sanctions a “huge reprieve” for Belaruskali, the state-owned producer, and its customers.2 There clearly seems to be some realpolitik at play; tougher measures from the EU could have inflicted punishingly high prices on the bloc’s agricultural industry and driven Belarus ever closer into the orbit of its neighbour Russia. So, for now at least, Lukashenko seems to have got away with it. Barring this bump in the road, established potash producers and budding market entrants are generally having a good year so far. Prices are recovering from 2020 and appear set fair for several years now – the oil industry and bitcoin investors would crave the predictability potash offers right now. Unlike oil, global demand for potash should grow steadily in step with the increasing need for food worldwide. Canadian giant Nutrien is confident it will set a sales record this year for potash, while at the other end of the scale multiple companies in Western Australia are edging ever closer to first production of sulfate of potash (SOP) fertilizer. In the Middle East and North Africa – as our Contributing Editor Gordon Cope reports from pg. 10 – major new projects are advancing in Morocco and Eritrea. The latter, managed by Danakali, is examining the feasibility of using solar, wind and geothermal energy to become a zero carbon SOP producer; hopefully this will become a feature of other projects. From potash to trees, and eagle-eyed readers will have noticed a World Land Trust logo adorning the contents page of this issue. World Fertilizer will now be printed on Carbon Balanced Paper, which means that the carbon emissions from the paper in the magazine will be offset through the preservation of ecologically important forests in Vietnam that are threatened with clearing. To find out more about this worthy initiative, please visit www.carbonbalancedpaper.com

References 1.

DEVITT, P., and SYTAS, A., ‘Most Belarus potash exports not affected by EU sanctions – analysts’, https://www.reuters.com/world/europe/most-belarus-potash-exports-not-affected-by-eu-sanctionsanalysts-2021-06-25/ (25 June 2021). KNIGHT, H., ‘Limited scope of latest EU sanctions deals BPC a reprieve’, https://www.crugroup.com/ knowledge-and-insights/insights/2021/limited-scope-of-latest-eu-sanctions-deals-bpc-a-reprieve/ (25 June 2021).

JULY/AUGUST 2021 | WORLD FERTILIZER | 3

Daily Fertilizer Price Assessments

Nitrogen

Ammonia

Phosphates

Sulphur

• Prilled: - China fob

• East Asia cfr

• Granular: - Egypt fob - Brazil cfr - Nola (US Gulf) fob $/st

• Middle East fob

• • • • •

• China cfr granular $/t • China domestic (ex works) Yn/t

(excluding Taiwan)

DAP fob China DAP cfr India MAP cfr Brazil DAP barges fob Nola MAP barges fob Nola

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Sharp price action captured earlier with daily assessment

Over the highlighted 4 week period (7 Jan to 4 Feb 2021) the price of DAP fob China grew from $397.50/t to $492.50/t, an increase of 24%. The blue line on the graph, marked by the 5 weekly prices over this period (orange) clearly highlights this price growth. However, the 21 daily prices over this same period (grey line) provide greater detail on how this price growth was achieved.

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Market Reporting Consulting Events

WORLD NEWS GERMANY South Harz Potash selects Angers to drill at Ohmgebirge

outh Harz Potash (SHP) has selected H. Angers Söhne Bohr - und Brunnenbaugesellschaft (Angers) to drill the ﬁrst of two planned twin holes at its Ohmgebirge project in Germany. Drilling of the first hole is expected to commence in 4Q21. SHP is already in possession of a large database of drillhole information for its licence areas, including Ohmgebirge, and requires only a minimum of confirmatory drilling in order to elevate the JORC status of each. The drill hole is planned to a depth of 665 m, which will fully penetrate the known potash seam. The drill rig will recover potash and salt core with an ultimate diameter of 63.5 mm. As part of the development programme at Ohmgebirge, SHP is conducting negotiations with landowners and tenants for second drill site options. SHP has a total inferred resource of 5.3 billion t; within that, Ohmgebirge represents 325 million t grading 13.1% K2O. SHP expects the two Ohmgebirge confirmatory holes to lead to a revised mineral

resource estimate (MRE), with the inferred resource on that property upgraded to the Indicated category. The company has negotiated with providers of the various components of the scoping study and work is poised to commence once formal drilling permission is received. The scoping study will include a detailed resource assessment by Micon International Co. Ltd., and the inclusion of the results from the twin drill holes, leading to a revised MRE. Once complete, K-Utec Salt Technologies GmbH will then revise the mining and processing sections and update both capital and operating costs. The study will also include an appraisal of the potash and industrial salt markets and will provide guidance price forecasts for a financial model. As a result of the delays experienced in procuring landowner and tenant approved drill sites and the competition for drill rig availability, the company now expects drilling of the second confirmatory twin hole and completion of the scoping study in 1Q22.

RUSSIA Acron Group to increase urea capacity at Veliky Novgorod facility

cron Group has launched preparations for a large-scale overhaul of four urea units at its facility in Veliky Novgorod, at a total cost of US$92 million. With completion scheduled for 2024, the project will increase the total capacity of urea units 1 – 4 by 55%, from 2000 tpd to 3100 tpd, boosting annual output by 390 000 t. Stamicarbon has been selected as the basic design and technology licensor. The investment project will also include installing a new urea synthesis shop. The facility currently has six urea units in operation. The first four units, with a total design capacity of 360 000 tpy, were put on-stream in 1969 – 1972 and subsequently upgraded to 730 000 tpy. In 2012, the company commissioned the 350 000 tpy Urea-5 unit, which was later upgraded to 515 000 tpy. The Urea-6 unit, with a capacity of 210 000 tpy, was put into operation at the end of 2018. The company is currently completing its Urea-6+ project, which will increase the unit’s capacity to 730 000 tpy. Once all these upgrades are complete, the Novgorod facility will be able to produce over 2.3 million tpy of urea, making Acron the largest urea producer in Europe. Acron has also launched preparations for a large-scale modernisation of the Ammonia-2 unit at the Novgorod facility, at a total cost of US$95 million. With completion scheduled for 2023, the project will

increase the unit’s operating capacity by more than 25%, from 1800 to 2300 tpd, ramping up ammonia annual output by 175 000 t. The project’s general designer is Acron Engineering. KBR will provide the process licence and core equipment, among the largest of which is a 40 m-high ammonia synthesis column weighing over 1300 t, a waste heat boiler and an additional KRES reactor. A similar expansion of production capacity is underway at the company’s Ammonia-3 unit. Once both projects are complete, ammonia output will increase by 375 000 tpy. The company signed a series of agreements at the St Petersburg Economic Forum held in June, including a memorandum with Ultramar by which the companies plan to increase transshipments of Acron’s mineral fertilizers through Ultramar’s terminal at the Ust-Luga Commercial Seaport in Leningrad Oblast. Using new storage capacity, Ultramar will provide up to an additional 10 million t of transshipment capacity between 2022 – 2030 for mineral fertilizers produced by Acron. Acron and Gazprombank also signed a cooperation agreement on investments that will allow Acron to obtain financing on favourable terms for ESG investment projects that reduce greenhouse gas emissions and other pollutants.

JULY/AUGUST 2021 | WORLD FERTILIZER | 5

WORLD NEWS NEWS HIGHLIGHTS

IN BRIEF

SPAIN Mining concessions granted for Muga project

the construction agreement with its preferred contractor, a request to initiate the construction of the bolter miner, finalising pending procurement of equipment and managing the local town hall construction licences. In parallel with these activities, and together with Endeavour Financial, the company is reviewing its financing options, for both debt and equity. The Muga project and the company’s other potash tenements in Pintanos and Sierra del Perdón are located in the Ebro potash-producing basin in Northern Spain.

Planned high-speed railway will not affect potash mining in Germany’s Werra region

ighﬁeld Resources has announced that the mining concessions for the Muga potash project, namely Fronterizo, Muga and Goyo, have been approved and signed by the administrations in Madrid, Aragón and Navarra. Following the award of the concessions, the company’s priorities will focus on the preparation of construction at Muga. While this preparation has been advanced in the last few months, the company will expedite key pre-construction activities including: completion of

Lake Disappointment SOP project awarded Major Project Status

CANADA Northern Nutrients to build urea fertilizer manufacturing facility in Saskatchewan

Dangote urea plant set to begin exporting to US and Brazil

Jansen potash project FID delayed Itafos completes plant turnaround at Conda phosphate business Environmental approval process for Khemisset reaching completion

he Government of Saskatchewan has welcomed the decision by Northern Nutrients to build a sulfur-enhanced urea fertilizer manufacturing facility near Saskatoon. The facility will be the first in Canada to utilise Shell Thiogro technology to make sulfur/urea prills. It will be the first non-potash fertilizer manufacturing plant built in Saskatchewan since 1992.

Construction of the new CAN$25 million facility will begin in July 2021, with expected completion in early 2022, producing at an initial annual capacity of 28 000 t for domestic and export markets. 30 new employees will be hired when the plant is operational, and at full capacity it should supply 15 to 20% of Western Canada’s sulfur fertilizer needs.

USA CF Industries seeks countervailing duty

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6 | WORLD FERTILIZER | JULY/AUGUST 2021

investigations into UAN imports

F Industries has ﬁled petitions with the US Department of Commerce and the US International Trade Commission requesting antidumping and countervailing duty investigations into urea ammonium nitrate solutions (UAN) imports from Russia and Trinidad and Tobago. CF Industries, the largest producer of UAN in the US, requested the

investigations due to the harm it argues the domestic UAN industry has experienced from the imports. The Department of Commerce will decide whether to initiate investigations, and the International Trade Commission will initiate a concurrent investigation to determine whether such imports materially injure the US UAN industry.

WORLD NEWS DIARY DATES 65th Annual Safety in Ammonia Plants and Related Facilities Symposium 29 August – 02 September 2021 Online aiche.org/conferences/annualsafety-ammonia-plants-andrelated-facilities-symposium/2021

Ammonia 2021 15 September 2021 Online worldfertilizer.com/ammonia2021/

Sustainable Fertilizer Production Technology Forum 2021 20 – 23 September 2021 Online events.crugroup.com/ sustainableferttech/

Sulphur + Sulphuric Acid 2021 01 – 04 November 2021 Online

CANADA Nutrien announces increase in potash production

utrien has increased its 1H21 earnings guidance, given the strength in global fertilizer markets and strong operational results. 1H21 adjusted net earnings per share (EPS) are expected to be US$2.30 to US$2.50, up signiﬁcantly from the previous guidance of US$2.00 to US$2.20 (1Q21 adjusted net earnings per share was US$0.29). In response to continued tightening in global potash market conditions, the company is planning to produce a further 1 million t of incremental potash in 2021 compared to expectations earlier this year. The majority of the increased production is expected to occur in 4Q21, with some of these additional tonnes expected to be sold in early 2022. Updated guidance for potash sales volumes in 2021 is between

USA FEED work completed at Koch Fertilizer’s Beatrice

events.crugroup.com/sulphur/ home

nitrogen plant

15th Annual GPCA Forum 07 – 09 December 2021 Dubai, UAE

gpca.org.ae/events/15th-annualgpca-forum-2/

Turbomachinery & Pump Symposia 2021 14 – 16 December 2021 Houston, Texas, US tps.tamu.edu

To stay informed about the status of industry events and any potential postponements or cancellations of events due to COVID-19, visit World Fertilizer’s events page: www.worldfertilizer.com/events

13.3 to 13.8 million t, which would exceed the company’s previous record high for annual sales volumes of 13 million t set in 2018. Domestic and offshore potash sales volumes are currently fully committed through September, based on the company’s original production profile for 2021. Nutrien will be hiring additional employees and adapting its resources to increase production across most of its six potash mines with available capacity, ramping up its Vanscoy facility in Saskatchewan, Canada, in particular. Nutrien expects these actions to result in upward revisions to potash-related guidance for the second half of 2021 from both a volume and EBITDA perspective, which will be addressed in 2Q21 results.

ith Black & Veatch having completed key front-end engineering design (FEED) work and cost guidance, Koch Fertilizer is undertaking a US$90 million upgrade of its Beatrice nitrogen plant in Nebraska, US, looking to boost output while improving its reliability and environmental and safety performance. As part of the push to increase production capacity of urea ammonium nitrate (UAN) by 75 000 tpy, Black & Veatch worked closely with Koch Fertilizer and the technology provider in performing the necessary up-front design. Black & Veatch also provided total direct cost insights and developed the integrated, detailed engineering and procurement schedule for the project, which includes a vent scrubber system. The improvements at the plant, which produces ammonia and liquid UAN fertilizer, are to be completed in

8 | WORLD FERTILIZER | JULY/AUGUST 2021

autumn 2021, and build on other recent enhancements, including increasing ammonia loading capacity. Beginning in March 2020, detailed engineering and procurement services were provided by Black & Veatch for the primary, non-proprietary equipment and other supporting components and commodities. Black & Veatch completed the primary engineering work at the end of last year – despite COVID-19 restrictions and challenges – and will provide Koch Fertilizer with engineering support during construction, commissioning and start-up. In the past few years, Koch Fertilizer has invested more than US$7 million to substantially increase ammonia loading capacity at the site and reduce customer wait time. The company also added new loading racks, which more than doubled the plant’s peak loading capacity.

Designing our future together Stamicarbon: Pioneers in developing and licensing state-of-the-art fertilizer plants For more information visit: www.stamicarbon.com

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Gordon Cope, Contributing Editor, discusses the state of the fertilizer industry in various MENA countries, the challenges faced by the region and current efforts to tap into existing resources.

Morocco Africa holds the world’s largest phosphate deposits, with total reserves at approximately 50 billion t. Morocco has 70% of that total – approximately 35 billion t – and thanks to state-owned OCP, the country is the world’s second largest producer of phosphate, after China. As part of its goal to supply affordable fertilizer to other African nations, OCP is working with the Nigerian government and industry associations to develop the country’s fertilizer manufacturing. Part of the plan is to construct a 750 000 tpy ammonia plant in Nigeria; OCP will also supply up to 1 million tpy of phosphate to create blends for domestic farm consumption. The initial plan calls for ﬁrst production in 2025. Morocco also holds abundant deposits of potash. In March 2021, Emmerson PLC announced it was close to launching its Khemisset potash project in northern Morocco. The UK-based company is seeking to develop an estimated 537 million t of potash with an average grade of 9.24% potassium oxide (K2O). Output from the mine would average 735 000 tpy of K60 muriate of potash (MOP), and 1 million tpy of de-icing salt. The project has numerous

Eritrea Danakali continues to advance its Colluli potash project in Eritrea. In late 2020, the Australian-based company announced it had successfully completed assessment work on the solar and wind energy potential of the proposed open pit mine, conﬁrming that these renewable energy resources could be incorporated into future generation power in order to achieve a zero carbon footprint. The project is a 50:50 joint venture (JV) between Danakali and the Eritrean National Mining Co. (ENAMCO). Located 230 km southeast of Eritrea’s main port of Massawa, reserves have been estimated in excess of 1 billion t of 11% K2O. Colluli has been divided into two phases: Module I will have a capacity of 472 000 tpy of sulfate of potash (SOP), and Module II will double capacity to 944 000 tpy. The project is expected to be completed around 2023.

Jordan Jordan is a major producer of potash, using mineral-laden water from the Dead Sea to produce carnallite. The potash salt is obtained by pumping water into artiﬁcial basins and allowing it to evaporate (there is over 100 km2 dedicated to salt production in the region). In 2020, the Arab Potash Co. (APC) alone produced 2.4 million t using the evaporation method. Because the dyke that isolates APC’s artiﬁcial basin becomes porous over time, it has to be periodically reinforced. In early 2021, German-based Bauer International completed a 4.2 km cut-off wall to maintain impermeability at APC’s facility.

Egypt Egypt, with its recent discovery of offshore gas (including the 30 trillion ft3 Zohr ﬁeld), is both a leading manufacturer of nitrogen (with 17 domestic plants), and an important consumer along the fertile Nile valley and Nile Delta. In June 2020, Austrian-based SBN completed construction of a 1050 tpd high-pressure stripper for NCIC’s ammonia plant at its Ain El Sokhana complex, 100 km southeast of Cairo. The new plant is expected to enter operation in 2022 and will have the capacity to produce 440 000 tpy of ammonia, 380 000 tpy of urea and 300 000 tpy of calcium ammonium nitrate. Egypt’s Misr Phosphate Co. has begun construction of a new 1 million tpy phosphoric acid plant in Abu Tartur in the New Valley Governorate. Construction of the US$1 billion facility will be undertaken by a Chinese consortium; China’s Wengfu Group, one of the largest phosphate producers in the world, has signed a long-term contract to take approximately 500 000 tpy of output.

of cheap natural gas. Capacity is expected to grow to 7.7 million tpy by 2030; the majority of growth will occur at the FALAT RCF GSFC JV ammonia plant in the industrial port of Chabahar, located in the Gulf of Oman.

Qatar Qatar, with its vast reserves of natural gas, is the world’s largest exporter of LNG, but it is also a signiﬁcant nitrogen fertilizer manufacturer. The Qatar Fertiliser Co. (QAFCO) produces approximately 3.8 million tpy of ammonia and up to 5.8 million tpy of urea. The majority of urea is exported to 20 countries around the world to be used in fertilizer. In 2020, Industries Qatar purchased Qatar Petroleum’s 25% stake in QAFCO for US$1 billion, and Yara’s 25% stake for a further US$1 billion, making it 100% owner.

United Arab Emirates In 2019, OCI and Abu Dhabi National Oil Co. (ADNOC) merged the companies’ fertilizer businesses in Egypt, Algeria and the United Arab Emirates to create the JV Fertiglobe. The new company has a production capacity of 5 million tpy of urea and 1.5 million tpy of ammonia, and a strong presence in both MENA and export markets, allowing it to economically promote agricultural growth in East Africa, Asia and Brazil. In April 2021, OCI and ADNOC conﬁrmed that the companies were considering an IPO in order to leverage cost advantages and opportunities for growth. As the JV noted, “Fertiglobe is underpinned by a young asset base and a robust storage and distribution infrastructure with access to key ports on the Mediterranean, Red Sea and Arabian Gulf.”

Saudi Arabia

Oman

Saudi Arabia’s SAFCO is a major fertilizer producer in the Gulf region. In 2020, it produced almost 6 million t of fertilizer (mostly urea and NPK blends), up from 5.55 million tpy in 2019. Most of the fertilizer is for the export market to major consumers, including North America, Europe and Asia. In early 2021, SAFCO formally changed its name to SABIC Agri-Nutrients Co. as part of a consolidation of fertilizer assets. In late 2020, Saudi Arabia exported the world’s ﬁrst shipment of blue ammonia. The ammonia was produced by Saudi Aramco using conventional steam reforming, but the CO2 was captured and sequestered. Japan, which was the recipient of the 40 t shipment, will use it as carbon-free fuel in its utilities. The country has also announced plans to build a multi-billion dollar megalopolis in the northwest tip of its sun-drenched environs. Among the many initiatives powered by sun and wind, NEOM will have a US$5 billion plant dedicated to producing green ammonia. Helios Green Fuels is a JV between the government-supported ACWA Power and US-based Air Products and Chemicals. The plan is to produce 650 tpd of hydrogen through hydrolysis, using 5 GW of renewable power, and then converting it to ammonia. Air Products will purchase the ammonia and ship it to customers around the world to be used in a variety of products. Analysts believe that the large-scale plant will be able to produce the ammonia for approximately US$1.50/kg by 2030.

In 2005, the Oman Oil Co. entered into a JV with India’s Krishak Bharati Cooperative Ltd. (KRIBHCO) and Indian Farmers Fertilizer Cooperative (IFFCO) to supply urea to India. The JV, known as Oman India Fertilizer Co. (OMIFCO), built two urea trains in Qalhat, Sur, with a total capacity of 2 million tpy of urea for export to India at US$140/t, signiﬁcantly below market prices. In August 2020, OMIFCO entered into a three-year agreement with Swiss-based Ameropa to supply 1 million tpy of urea for export to South America, China and Southeast Asia. “OMIFCO has positioned itself strategically in the urea and ammonia market globally, and we are quite proud of that,” noted the company. “Now we have a great opportunity ahead of us; targeting new markets for the Omani urea.” OMIFCO has plans to build a third train with an additional capacity of 1.3 million tpy.

Iran According to GlobalData, a consultancy, Iran has an ammonia capacity exceeding 6.5 million tpy, thanks to abundant supplies 12 | WORLD FERTILIZER | JULY/AUGUST 2021

Challenges In 2018, Algeria’s Sonatrach signed a US$6 billion contract with China’s CITIC Group to expand phosphate production in the Tebessa province by 9 million tpy of phosphate ore, up from current levels of approximately 1 million tpy. The country has since been rocked by civil unrest, however, placing increasing pressure on embattled President Abdelmadjid Tebboune. Weekly demonstrations by the Hirak mass protest movement have gripped major cities since April 2021, when the COVID-19 lockdown was lifted. Disenchanted citizens are seeking government reforms, democratic representation and an increase in living standards. International companies are increasingly reluctant to invest billions in the North African nation until issues are resolved.

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Poor infrastructure in many MENA jurisdictions hampers the movement of raw materials and finished products from ports and manufacturing plants to food-growing regions. This raises the price of fertilizers for farmers and blunts the incentive to increase yields. Change is arriving slowly; since the end of a decades-long conflict, Eritrea and Ethiopia are once again opening up and upgrading ports and roads. The 70 km road that connects the Eritrean port of Assab on the Red Sea to landlocked Ethiopia is being expanded to a four-lane highway. Eritrea has also hired DP World to manage its ports. The Dubai-based company is upgrading equipment and infrastructure at Assab and Massawa, which will facilitate the export of output from the Colluli potash mine to neighbouring countries. The lack of agronomic support throughout the region is a significant impediment to farming and fertilizer usage. Farmers lack knowledge regarding the specific needs of their soils, as well as an understanding of what types of fertilizers will benefit their crops. Governments are partnering with international producers to help alleviate these issues. For example, Russian-based URALCHEM and Uralkali are working with the Sudanese government to build infrastructure in order to import and deliver fertilizer mixes, as well as address the country’s specific needs for knowledge and training.

Future Much is being made of the move to use organic fertilizers to augment crops. It is currently a multi-billion dollar industry globally, and is growing in leaps and bounds. In Africa, plans are underway to leverage herd sources of manure for the beneﬁt of

local farmers. However, in order to make a significant impact, organic fertilizer has to be scalable. Paulee CleanTec, a technology company based in Tel Aviv, Israel, has patented a process that turns farm waste into organic, potash-rich fertilizer. The company notes that, in the US alone, farms generate 100 times more organic waste than humans, which can enter streams, groundwater and farmland if not treated. The oxidising process, which can be performed on farms, takes just one hour, and can turn manure into odourless, disease-free powder that can be stored for later use. This process is currently being tested at a farm in Israel and, should it prove to be efficacious, in regions where it is difficult or expensive to access conventional fertilizers farmers can leverage organic sources to increase yields.

Conclusion Throughout the MENA region, major projects are underway to build and operate domestic sources of nitrogen, potash and phosphate. This will allow farmers to access cheaper supplies of fertilizers, enhancing their ability to feed the burgeoning populations of their respective countries. Although the initiatives are encouraging, the region is urgently in need of signiﬁcant investment in infrastructure to complement the growth in home-grown supplies, as well as government initiatives to support agriculture through research, agronomics and ﬁnancial aid. In light of all of the above, international fertilizer companies have a critical role in augmenting fertilizer usage through imports and bespoke-blending of NPK to meet local crop and soil needs.

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COVER STORY

PR OC ESS IM PR OVEMENT AT THE STEAM VALVE David C. Nelsen, REXA, Inc., USA, explains why plant engineers should upgrade steam turbine governor control valves to optimise control of turbomachinery.

t the corporate level of operating a plant a standard business model is to reduce costs and increase revenue. Achieving these high-level business objectives starts with execution at the plant level. Typical areas for improvement include increasing yield and throughput while reducing downtime, energy usage and maintenance costs – all while keeping an eye on improving safety.

At most fertilizer plants, achieving optimised control of turbomachinery trains is crucial to maximising production. An effective plant level modernisation package ensures that all the critical turbomachinery control elements are working together seamlessly. This is achieved through advanced control algorithms, accurate measurement and precision actuation. Together these technologies help a company to execute their priorities at a plant.

Just like any control system, turbomachinery control consists of: Measurement. A control system. A control element. A good turbomachinery control system keeps the process steady, and provides protection to the machinery

Figure 1. Every element is important to achieving reliable and efficient turbomachinery control.

as well as the upstream and downstream processes in the event of an upset condition. To understand the importance of these elements working together, think of the following analogy: in a car driving down a road, the driver is the one taking in the measurements of their car between the lanes, the levels of petrol and oil and the response of the tyres on the road. The control system would be similar to the driver’s brain making the decisions about what to do next – do they need to accelerate or slow down? The actuation responds just like the pedals in a car, and they have to work well so that the driver can stay safe and reach their destination on time. The response of the car is the feedback from the process – did the tyres maintain traction, did the speed increase when needed? Ultimately, did the car stay on the road when the deer jumped in front of it, or did the driver have to pull over? These elements are all working together so quickly that the driver does not even think about it most of the time. The same is true for turbomachinery control: knowing where to go is the blueprint for how to design a system to work the way that it is required to. Plant engineers often focus on upgrading the electronic controls systems; many times this does not extend to the actual control actuators operating in the field. As an example, most plants may have upgraded and are using the most advanced control platforms with the most defined algorithms that are tuned and calibrated to modulate the steam turbine governor control valve actuator. Despite this, the steam turbine governor control valve actuators in the field are often overlooked as far as technology upgrades and operational effectiveness are concerned.

Oil supply

Figure 2. Traditional pilot and power piston arrangement. 16 | WORLD FERTILIZER | JULY/AUGUST 2021

Many traditional hydraulic systems are open-loop systems using a hydraulic power unit (HPU), a gravity-fed reservoir and a series of servo and/or proportional valves for control. These systems have a large quantity of oil and essentially all utilise the same principle of operation. Hydraulic fluid is drawn from the reservoir by motors and pumps to facilitate movement of the actuator cylinder, and is then drained back to the reservoir when the cylinder moves to position. The oil is continually circulated at high frequency to accomplish the high-resolution control performance required for the application. Since the system is not sealed and is open to the atmosphere at the reservoir the oil is subject to breakdown. It should be kept in mind that the control oil is from the same HPU that supplies turbine/compressor bearing lube oil. If turbine or compressor shaft seals leak, they can also contaminate the oil in the lube oil reservoir. Exposure to the atmosphere adds moisture, which causes degradation to the oil system due to moisture ingress, oxidation and corresponding acid build-up. The continuous circulation of hydraulic fluid adds heat to the oil, which accelerates and exacerbates the breakdown of the hydraulic fluid.

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In order to combat the effects of oil breakdown, plant operators are required to perform a high level of maintenance on these systems. Extensive filtration systems are used, demanding high maintenance intervals coupled with flushing and replacement of hydraulic fluid. Ultimately, the hydraulic fluid degrades to the point where the servo and proportional valve actuation systems become stuck, resulting in loss of control and system downtime. One way to address these oil issues is to consider REXA, Inc.’s ElectraulicTM actuation technology. To alleviate all the oil problems linked with traditional hydraulic systems, companies are replacing the steam turbine original equipment manufacturer (OEM) governor valve actuation with self-contained actuation systems

produced by REXA. The savings in maintenance costs and reduction in downtime make the system a suitable replacement. The actuator’s hydraulic oil is self-contained and therefore does not use the existing turbine control oil. Both the frequent maintenance needs of the OEM power cylinder and the issues resulting from contaminated or dirty control oil are eliminated. Installation costs are also lower, since new hydraulic piping is not required. In fact, in many cases the installation and calibration of the actuator takes less than half a day. It is worth noting that existing OEM servomotors (actuators) are exposed to turbine control oil, which can contaminate and affect servomotor performance. Furthermore, internal parts can start to stick due to exposure to contaminated turbine control oil. Many mechanical feedback linkage are wear points, requiring high maintenance. Finally, it can also be less expensive to retrofit an existing servomotor to a REXA actuator than to continue with the high maintenance costs of an existing OEM servomotor. Common problems experienced by turbomachinery due to traditional oil-based mechanical technology include: Frequent unit trips. Dirty oil, leading to frequent servo valve maintenance or failure. Sticky mechanical actuators. Oil leaks (fire hazard). HPU operation and maintenance for the governor control oil system. Lack of OEM actuator spare parts. Electraulic actuators are designed for a continuous modulating service with an adjustable dead-band as tight as 0.05% of stroke. The inherent incompressibility of the hydraulics provides repeatable, stiff and accurate control performance, as is required in this demanding application. The drawbacks associated with HPU-based hydraulics are eliminated by design. The system utilises a patented flow match valve (FMV) technology. The FMVs are used in conjunction with a bi-directional gear pump in a positive pressure sealed hydraulic system, removing the need for a hydraulic reservoir and the problematic servo and proportional valves. The hydraulic circuit design means there is no need for governor valve control oil filtration, and it requires no oil maintenance as part of a preventive maintenance plan. Electraulic actuators are also simple to make fail-safe, without any detriment to the control precision. With both spring and accumulator-based fail-safe technology, the actuator can achieve trip speeds as fast as 300 msec., meeting the requirements for turbine control. Redundancy options are another benefit of using the technology.

Case study

Figure 3. REXA before and after on a De Laval steam turbine. 18 | WORLD FERTILIZER | JULY/AUGUST 2021

Decades-old low-tech mechanical and hydro-mechanical governor equipment continue to be operated with many turbines in reﬁneries and process plants. This equipment can present maintenance and operational challenges. It can lead to reduced efﬁciency and reliability in the production process. The job of the turbine speed governor is to

provide accurate speed control, thus preventing process oscillations and unplanned shutdowns, and improve process throughput. To achieve this goal precisely and dependably, it is advisable to perform a governor valve actuation retroﬁt. The advantages of doing so include stabilisation of equipment speed with tighter revolutions per minute (rpm) control, and avoiding nuisance process and equipment trips. This enables the turbine to operate at its maximum potential without interruption. Compressor Controls Corp. (CCC) recently implemented a mechanical retroﬁt for a North America process plant experiencing large swings (100 – 200 rpm) in the speed control of a steam turbine. The speed instability was caused by an inadequate governor valve actuation system. The sticking actuator could not maintain the setpoint target and had recently caused a process trip of the main air blower.

Sticky actuators Difficulties with speed control meant the steam turbine had to be operated manually and at a higher target speed than desired. In addition, load sharing with a secondary process compressor could not be implemented and the operator had to use the blow-off valve to adjust the air flow. Additionally, the steam turbine could not use the existing CCC automatic start-up sequence because of the sticking actuator. The new actuation system specified was a REXA Electraulic self-contained unit. It uses a position-controlled power module, driven by a 4 – 20 mA signal, to turn an internal oil gear pump that displaces hydraulic fluid from one side of a cylinder piston to the other. A rod extending from the cylinder is mechanically connected to the steam turbine governor valve rack and is able to position the rack from the closed to open position. The system has no need for an external oil supply source. The actuation retrofit was executed during an unscheduled outage. As a result, the turbomachinery train could more accurately match its performance with the desired process setpoint. This also allowed use of the automatic start-up sequencing and load sharing features of the CCC control system. Controlling compressor efficiency starts with precision control of the steam turbine driver, in order to regulate the speed of the compressor. Actuator upgrades depend on turbine design. For turbines with shell-mounted control valves, the actuators may individually drive multiple control valves or there may be a single power piston arrangement that drives a bar or rack, allowing multiple steam valves that are mechanically coupled together to be opened sequentially. For turbines with chest-mounted control valves, it may be a globe-style valve external to the turbine that is providing the control. In some configurations, a pilot valve assembly with a small stroke and a low thrust requirement may be used to port lube oil to the power piston.

Conclusion Optimisation of actuation is a key contributor to maximising the precision control ability, availability and safety of turbomachinery – doing so helps to minimise process upsets and quickly return the operation back to normal in a safe and controlled manner.

Figure 4. Example of a less effective pneumatic actuation system dependent on customer supplied oil on pilot retrofit versus fully self-contained REXA Electraulic actuator. JULY/AUGUST 2021 | WORLD FERTILIZER | 19

DIGITAL Dr Katja Poschlad and Dietmar Wagner, thyssenkrupp Uhde, Germany, and Dr Stephan Körner and Dr Sophie Wei, thyssenkrupp Analytics & AI, Germany, explore the digital solutions available to fertilizer plants.

Figure 1. Anonymised example of a report of an ammonia plant.

What happens may be something that requires a response. Therefore, the fourth and final step is prescriptive: what to do about the situation? Optimisation models and simulations are required. The aim is to improve plant operation and performance, which can be achieved using applications, methods, algorithms and tools to cover all these four steps of data analysis. The results of this analysis by the company are summarised in regular reports, including recommendations for operation and maintenance. Report content will be explained to the client in regular meetings or calls. As an example, Figure 1 shows one page of a report for an ammonia plant that visualises key performance indicators determined in cooperation with the client. Additional performance indicators are given in more detail on the next pages of the report. The client will receive full process transparency through remote monitoring and analysis of performance and operation. Deep process insights will be given by pinpointing influential processes. Potentially inefficient process areas, otherwise hidden, will be uncovered. The client will be alerted to critical conditions, while root causes of issues will be pinpointed and recommendations for corrective action will be given. The next section shows how cluster analysis is one example of digital analysis that offers greater detail.

Cluster analysis

Figure 2. Plant operational states identified by the condition monitoring model for an ammonia plant.

22 | WORLD FERTILIZER | JULY/AUGUST 2021

Condition monitoring of plant operational states is a powerful tool for identifying signiﬁcant changes that are indicative of an unexpected plant behaviour or an operating error that would lead to failure of equipment and unplanned shutdowns if not addressed. The huge number of sensors in a chemical plant and the complex relationships in chemical processes means it is unfeasible to solely rely on supervision by plant operators. Data-driven condition monitoring applies machine learning algorithms to learn the complex multivariate correlations from historic plant data. They can either be applied in real-time to detect anomalies and deviations from stable plant operation (and hence prevent trips in a timely manner), or they can be employed for root cause analysis of unexpected plant behaviour by identifying patterns usually obscured from the plant operator. Figure 2 shows an exemplary dataset of plant parameters and setpoints for an ammonia plant equipped with more than 1500 pressure, ﬂow, temperature and

Digital twin A digital twin is a virtual representation of a real-world object. It is used to understand and predict the physical counterpart’s performance characteristics. The benefits for the user are an increase in the transparency of the plant, a reduction in unwanted fluctuation, an increase in process stability or flexibility and the enhancement of operation in a dynamic and adaptive way. Accurate information about actual plant performance is provided in near real-time, at any

time, from all the processes. There is a reduction in variability in process outcomes – including product quality and product throughput – through the identification of the process conditions for the best output and making timely adjustments to the process. The digital twin assists the operator to identify different operational conditions, even with multi-dimensional interdependencies. Additionally, the digital twin may provide virtual sensors for data that is not measured and the possibility to improve the preparation of future revamp studies. Digital twins can be based on first principle models (white box), statistical (black box) approaches or a combination thereof. They require plant information as input variables and calculate process sensory data, which may have been measured or which are unknown. The digital twin consists of multiple elements that are virtual representations of various plant sub-units or single devices comprising, for example, ammonia, urea, ammonium nitrate, calcium ammonium nitrate and nitric acid processes and utilities. The extent of implementation of the digital twin for each sub-unit or device is determined according to the level of importance and complexity of the unit or device. It will be continuously updated with measured data from the plant. The digital twin will process this data in near real-time and run in parallel to the actual plant, providing virtual monitoring, prediction and optimisation functions. Typical results are the continuous reporting and visualisation of performance-related sensor information (real or virtual), such as flows, concentration/analysers, pressures, temperature levels, etc. Additionally, description and

Helping improve your fertilizer quality

Kao Chemicals Europe

chemical sensors. In total, the dataset comprises measurements from over 250 days, of which a period of approximately 30 days has been examined more closely. During this period, the plant experienced an unplanned shutdown that has been studied by thyssenkrupp’s condition monitoring model. By grouping similar patterns of sensor correlations into clusters, the model can identify distinct plant operational states. Three such characteristic states are identified around the time period of the shutdown event, indicated by the coloured background. The blue state corresponds to normal plant operation, whereas the red state represents the shutdown. Interestingly, the data-driven condition monitoring model automatically detects a distinctively different third state (orange), days in advance of the shutdown. This state is characterised by sudden fluctuations in various sensors. Furthermore, the operating mode becomes unstable, switching between the blue and orange state. These indications render the orange state suspicious and potentially connected to the subsequent shutdown, which justifies further analysis.

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visualisation of operation monitoring ﬂuctuations – using statistics, derivatives and integrals for information such as averages, minimum and maximum ranges, internal proﬁles, short variance and long-term trends – can be given. Finally, key performance indicators are calculated and displayed. This enables staff to receive timely warnings of abnormal plant behaviour and to make data-based decisions, enriched by calculated process parameters that cannot be measured directly.

Operator training system One notable example of a digital twin application is its use as a training tool. As operators and staff can be trained with it, it is called an operator training system (OTS). The OTS used by tk Uhde describes the plant with physical equations dynamically, and has both monetary and safety benefits. Managing a plant is always a challenge; conditions must be optimal in order to achieve a good performance. Although there are many factors that affect safety and profitability, the human element is critical. A plant running within optimal conditions and without deviations is the perfect scenario. The fact is, however, that high annual losses are due to employee misunderstanding in various types of business. They are in general caused by actions (or lack thereof) taken due to misunderstandings, misinterpretations and a lack of confidence or understanding. Therefore, tk Uhde trains its employees and clients’ staff prior to commissioning. This increases the safety of staff, as well as the safety of everyone on-site. To help the operator to react correctly with greater confidence and knowledge, training of staff is indispensable. The OTS offers an up-to-date way of educating all employees to the desired standard. The benefits of trained staff for the operating company can be divided into two parts: economic advantages and safety advantages. As trained staff can keep the plant closer to the optimal condition and human mistakes are reduced, the plant will be more efficient and will have a higher on-stream factor. As risky and unfamiliar scenarios have been trained for in advance, the operator can react faster and the frequency of dangerous situations can be reduced. The training sessions offered by tk Uhde have different levels of complexity, starting with an easy level for beginners and progressing to highly complex sessions for veterans. With the training simulator several scenarios can be simulated, such as: Start-up (cold and hot). Normal operation.

Load change. Shutdown (planned and unplanned). Various failure scenarios. After signing in, a trainee can interact with the simulated plant in a similar way to a real plant. Any change will lead to a time-dependent behaviour from the plant, including changes in operating parameters such as temperature or pressure. The trainee can switch between two different views. In the DCS view, the trainee works like a control room operator. Setpoints or valve positions can be changed and the alarm list and trip schedule can be shown. The second possible view is the so-called ‘field view’. By switching to the field view, the trainee can see all field instruments and operate all hand valves. These two different visualisations are shown in Figure 3, using an ammonia synthesis loop as an example. As only DCS connected valves are visible in the DCS view, there are fewer valves shown in the left-hand side picture, whereas all valves can be seen in the field view. The training can be performed individually or several trainees can connect with their electronic device to one plant simulation. Consequently, tasks can be split among the group of trainees and communication between the field operator and the operator in the control room can be practiced as well.1

Conclusion Digital products and services, such as those provided by tk Uhde, combine the engineering and process expertise gathered as an EPC contractor during commissioning of process plants worldwide with data-driven methods and artiﬁcial intelligence. Such digital services help companies to analyse, stabilise and optimise a plant during its lifetime and support a safe operation. Avoiding an emergency shutdown of one day can save hundred of thousands of dollars; conversely, the cost of not operating under the optimal conditions quickly rises above several million dollars per year. Avoiding these situations will quickly pay off the initial expense of installing digital solutions. Ecological and safety parameters can also be optimised, allowing operators to fulﬁll their purpose to create a liveable planet.

Reference 1.

POSCHLAD, K., and WAGNER, D., ‘Digital Solutions For Fertilizer Plants’, Nitrogen + Syngas Virtual Conference 2021.

Figure 3. Surface of training simulator for ammonia synthesis loop for DCS view (left) and field view (right). 24 | WORLD FERTILIZER | JULY/AUGUST 2021

CASE-BY-CASE Joan Riaza, Kao Chemicals Europe, Spain, shows that identifying the main reason for dust formation in each individual occurence is crucial to determining the best solution.

ust formation is one of the biggest problems associated with solid fertilizers, particularly for granular types that are stored in bulk in large warehouses. Handling them in such an setting can affect workers’ health and the environment. There are several reasons, which will be covered in this article, that explain dust generation in granular fertilizers: granule morphology, climatic conditions, post-reactions and caking formation. Different technical solutions to this issue have been proposed over time, considering the origin of the problem, the fertilizer composition and the ﬁnal usage.

Present and future environmental demands call for a review of current anti-dusting technologies and the proposal of new ones, as will be discussed.

Main reasons for dust formation Granule morphology The granulation process can produce more or less spherical granules, with more or less smooth surfaces. The appearance of the final product will depend on the raw materials and the specific granulation mechanism.1 If a homogeneous slurry that contains all components of the fertilizer is being used and the granulation process involves layering one or several solid components over a seed, the granules finally obtained present a low abrasion capacity. However, if a significant quantity of solid components is added to the granulation process by means of an agglomeration process, where only a part is a homogeneous liquid mass, the granules obtained will present a high abrasion capacity (Figure 1).

temperature change can alter the crystal state, promoting density changes that cause degradation of the granules.

Post-reactions In many granulation processes, especially when the mass of granules is heterogeneous, reactions continue in the granules and on the surface. New salts can Figure 1. NPK 15-15-15, low abrasion capacity (left), and NPK 15-15-15, high abrasion capacity be generated, while (right). degradation and dust formation can occur as well. Water content plays an important role in this process. A typical example of this phenomenon is the post-reaction of NPK granules based on either ammonium nitrate and potassium chloride or ammonium sulfate and potassium chloride. Figure 3 shows XR mapping of an NPK based mainly on ammonium sulfate, mono/diammonium phosphate and potassium chloride. Because of these post-reactions some new crystals are formed on the surface of the granules. If these crystals are fragile, dust formation occurs easily when granules are manipulated. Figure 4 shows fragile crystals on granule surfaces.

Caking formation Figure 2. Detail of ammonium nitrate moisture absorption at laboratory scale in a climatic chamber.

Caking occurs due to several possible reasons, some (but not all) of which are the same as the causes of dust formation: climatic conditions and post-reactions. Another possible cause, however, is the deformation of the granules when submitted to high pressures. When a caked fertilizer mass is forced to be separated again, dust formation occurs from the areas of intersection. Figure 5 shows instances where post-reactions were the main cause of caking.

Effect of anti-caking additives

Figure 3. XR mapping – potassium (left). NPK with heterogeneous mass. More post-reactions. XR mapping – sulfur (right). NPK with heterogeneous mass. More post-reactions.

Climatic conditions Depending on the components present in the fertilizer, the critical relative humidity will be higher or lower. For instance, NPK fertilizers based on ammonium nitrate or urea can start to absorb moisture at a quite low relative humidity. Moisture can enter into the granules; later, when the granules are subjected to conditions of low humidity, moisture will be released, encouraging recrystallisation of salts on the surface of the granules as well as dust formation (Figure 2). Changes in storage temperatures can also promote crystal phase transitions – for instance, in ammonium nitrate a 26 | WORLD FERTILIZER | JULY/AUGUST 2021

In many cases, granular fertilizers are coated with a double treatment of an anti-caking additive mainly based on hydrocarbons, surfactants and an inorganic powder (talcum being the most common). Talcum is very useful for minimising the likelihood of caking, but the selection of a good-quality talcum and anti-caking formulation is essential to obtaining a satisfactory talcum adhesion on the granular surface. A bad selection, on the other hand, can promote the release of dust. In addition, depending on the compositions of the fertilizer and anti-caking formulation, some extra dust formation can be generated. In summary, anti-caking additives must be selected carefully.

Dust evaluation at laboratory scale Different methods have been proposed to measure dust formation. One of the most popular is the Dedusting Tower (Method IFDC S-122, International Fertilizer Development

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Center [IFDC]), where a sample of fertilizers is poured on the top of the tower while an air ﬂow passes from the bottom to the top.2 This process can be applied several times. The difference in weight between the beginning and the end determines the quantity of dust. Another method is to sieve the fertilizer sample, generally within the range of 0.5 – 1 mm. Prior to sieving, abrasion can be applied in a rotary drum, with the possibility of using Figure 4. SEM images of two examples of crystal formation on a granule’s surface, where metal balls depending on the type of the crystals have a needle shape that promotes dust formation. fertilizer (Method IFDC S-116).2 The quantity of dust formation is determined by the weight difference before and after the process. Figure 6 shows one of Kao Chemicals Europe’s rotary drums being used to carry out this test. This method can be applied to the same coated fertilizer sample at different times following treatment, in order to measure the performance of the coating agent over time. In addition to dust quantity, another important parameter is dust particle size distribution. Small particles remain suspended in the air, creating clouds that can travel kilometres away and affect urban areas, for instance. The company performs particle size measurement using laser diffraction equipment (Mastersizer 2000 from Malvern) in a cell where powder is dispersed in a solvent (Figure 7).

Dust control additives Depending on the main reason for dust generation – morphology of the granules (high abrasion); climatic conditions (moisture absorption or phase transition changes); post-reactions; caking tendency; or the effect of anti-caking additives – the company can propose different approaches to solve or at least minimise the problem.

Abrasion mitigation When an irregular surface is the main problem, additives with binding properties are needed in order to minimise the impact of the abrasion caused by handling the granules, as well as additives with a solid coating layer with high ﬂexibility or a liquid coating layer with high viscosity at room temperature. Figure 8 shows different anti-dusting additives that minimise the abrasion impact in granular monoammonium phosphate (MAP). Protection increases with a higher melting point and viscosity as well as a higher binder content. Results from a 0.5 mm sieving process followed by an abrasion test are shown.

Moisture absorption mitigation Figure 5. SEM images of two caked NPK granules. A general view and a detail of the intersection between both granules. 28 | WORLD FERTILIZER | JULY/AUGUST 2021

When moisture absorption is the main reason for dust generation, additives must be highly hydrophobic so as to avoid water penetration into the granule. Figure 9 shows the results from the treatment of an NPK fertilizer

with different additives, with and without the addition of talcum. Treated samples were placed in Petri capsules and subjected to conditions of 20˚C and 70% relative humidity for 15 hours. Moisture absorption was measured by the difference in weight. Later on, the samples were placed in a chamber at 40˚C and low humidity for 24 hours. Afterwards, a 0.5 mm sieving test was performed to measure dust formation. The most hydrophobic additive that had been developed (S-100) had the lowest dust generation. In fact, there is a correlation between moisture absorption and dust formation.

Post-reactions mitigation If there is a high mobility of salts within the granules due to a high water content, this promotes a greater number of post-reactions and more dust formation in turn. When post-reactions are one of the main issues, Kao proposes the use of internal additives that catch free water content, resulting in a reduction of the salts’ mobility within the granules and reducing the progression of post-reactions. These internal additives simultaneously increase granule cohesion as well. This solution is particularly recommended for NPK fertilizers with serious post-reaction problems. This treatment is generally combined with a suitable external coating treatment. The company advocates an integrated treatment using two coating drums. In the ﬁrst coating drum, the anti-dusting additive is applied and, later, an anti-caking additive is applied in the second drum; talcum can be also added in the second drum. Figure 10 shows a process scheme of the integrated treatment.

Figure 6. Rotary drum for abrasion test.

Caking tendency and anti-caking additive effects mitigation Dust formation generated by caking can be easily reduced through the use of suitable anti-caking additives. A wide range of additives can be offered, depending on the fertilizers’ composition. Additive selection is very important for minimising the caking tendency and the possible formation of dust due to lump crushing. Furthermore, anti-caking formulations can promote dust formation if the surfactants in the formulations are not suitable. A deep knowledge of surfactants and fertilizers’ compatibility with salt is required to avoid dust generation.

New additives for a more environmentally-friendly world At present, standard coating additives generally contain some components that are not biodegradable – such as mineral oils – and some other ecotoxic ones, such as fatty amines. However, more sustainable additives, such as Kao’s eco-friendly dust control additives, can become an efﬁcient alternative to regular coating agents by offering a vegetable origin, high biodegradability and low eco-toxicity in all the components present in the formulations.

Figure 7. Mastersizer 2000 used to measure particle size distribution of the dust released from fertilizers.

Figure 8. Dust evaluation by sieving at 0.5 mm and abrasion in a rotary drum of a monoammonium phosphate treated with different Kao additives.

JULY/AUGUST 2021 | WORLD FERTILIZER | 29

To demonstrate the applications of these new additives the remainder of the article will focus on some of the issues that have been previously discussed: abrasion and moisture absorption. Performance levels will be compared to standard additives.

Abrasion mitigation

Figure 9. Moisture absorption evaluation in climatic chamber of an NPK treated with different additives, with and without talcum.

Figure 11 shows the formation of dust from an ammonium sulfonitrate treated with several eco-friendly prototypes based on vegetable derivatives (blue bars) versus a standard anti-dusting treatment, SK Fert AD-110 (orange bar). Some formulations can be seen to have a good performance, although it is not easy to reach standard anti-dusting treatments levels. The Eco-1 prototype presents a dust formation value similar to the standard reference. Kao is engaged in a continuous process of developing better anti-dusting treatments in the context of abrasion mitigation.

Moisture absorption mitigation

Figure 10. Scheme of double treatment process.

Figure 12 shows the moisture absorption values of one fertilizer (NPK 25-3-0) treated with several eco-friendly prototypes based on vegetable derivatives (blue bars) versus a standard anti-dusting treatment, SK Fert AD-110 (orange bar). The fertilizer was submitted to high humidity conditions in a climatic chamber. The test was similar to the test discussed earlier in the article, in which treated samples were placed in Petri capsules and subjected to conditions of varying temperature and humidity. Again, there is a correlation between moisture absorption and dust formation. In this case the values closer to SK Fert AD-110 were obtained with the Eco-9 prototype.

Additives for organic farming fertilizers An emerging technology in eco-friendly additives are anti-caking and anti-dusting agents for organic farming fertilizers that require special components in their formulations. Kao is also working to incorporate these kinds of additives into its portfolio. The preliminary results are promising.

Figure 11. Dust evaluation by sieving at 0.5 mm of an ammonium sulfonitrate treated with different eco-friendly prototypes.

Conclusions In summary, it can be concluded that dust control is not an easily solvable problem in the context of granular fertilizers. As has been explained in this article, several factors can lead to its formation. But if the main reasons for each case can be understood, then it becomes possible to minimise the impact with speciﬁc solutions. Due to the fact that some of the solutions are based on surface treatment of organic additives on the granules’ surface, the environmental impact needs to be minimised and sustainable alternative solutions need to be proposed – this is the main challenge for the coming years.

References 1.

Figure 12. Moisture absorption evaluation in climatic chamber of a NPK treated with different eco-friendly prototypes. 30 | WORLD FERTILIZER | JULY/AUGUST 2021

United Nations Industrial Development Organization and International Fertilizer Development Center, Fertilizer Manual (1998). RUTLAND, D.W., Manual for Determining Physical Properties of Fertilizers (1993).

Philip J. Parsons, BakerRisk, USA, identifies common hazards that can contribute to catastrophic dust fire and explosion events, and emphasises the importance of a robust dust hazard analysis strategy.

The importance OF HOUSEKEEPING

dust hazard analysis (DHA) is a valuable tool for identifying and preventing or mitigating combustible dust fire and explosion hazards. For facilities in the US that process or handle combustible particulate solids, a DHA is required under National Fire Protection Association (NFPA) Standard 652.1 Similarly, ATEX Directives 1999/92/EC and 2014/34/EU require dust hazards to be evaluated at facilities throughout Europe.2 This article summarises the elements of a DHA and identifies common hazards observed across

a range of industries handling a variety of combustible particulate solids that are also relevant to the fertilizer industry. The identified common hazards have all been causal factors in actual combustible dust fire or explosion incidents that resulted in the loss of life or severe injury, in addition to the loss of capital assets and business interruption. A robust DHA will identify such hazards and, using the guidance provided in relevant NFPA standards, identify prevention and mitigation strategies that can be implemented to manage the associated risks.

Background Particle size is a critical factor in the performance of fertilizer products, as it influences the rate of active ingredient delivery. In general, the larger the particle size, the longer the product will take to break down, releasing the nutrients within. Powders offer the fastest nutrient delivery; however, they also are subject to being windblown. Most fertilizer final products typically have a particle size in the order of 1 to 2 mm, but processing and handling the materials (e.g. through pneumatic conveying, milling, sieving, granulating, etc.) can generate much finer particulates. In the US, NFPA 652 defines a combustible dust as a “finely divided combustible particulate solid that presents a flash-fire hazard or explosion hazard when suspended in air or the process-specific oxidising medium over a range of concentrations,” and further indicates that the particulate solid characteristic dimension must be less than 500 μm. It is an obligation of the owner/operator of the facility to determine if the fine particulates are combustible; once the presence of fine particulates is identified, a determination should be made if they present a fire or explosion hazard (e.g. through laboratory testing). Many particulate solids handled in the fertilizer industry are inert

(e.g. phosphate rock). Urea, a common nitrogen-release fertilizer, has been shown to be non-combustible even though in some cases testing the material can suggest urea is a combustible dust.3 One of the most hazardous particulate solids handled in the fertilizer industry is sulfur, which in bulk form is liable to spontaneous combustion and, if dispersed in the air, can present explosion hazards, particularly since sulfur dust is sensitive to ignition (e.g. electrostatic discharge, sparks). A requirement of all international standards for facilities processing or handling combustible particulate solids is to perform a DHA. For example, in the US (and other jurisdictions that follow guidance provided in NFPA standards), a DHA is required for new and existing installations, as well as for upgrades to existing installations. The standard, effective on 7 September 2015, allowed affected facilities a grace period of five years to complete a DHA (i.e. by September 2020). The Center for Chemical Process Safety’s ‘Guidelines for Combustible Dust Hazard Analysis’ provides perhaps the most current and comprehensive overview of the different DHA approaches available to a facility.4 To put the importance of a DHA in perspective with regards to regulatory compliance, many US Occupational Safety and Health Administration (OSHA) citations regarding combustible dust hazards list the lack of a DHA at the top of the citation.5 In 2018, for example, a US jury awarded US$39.7 million to a man who was injured in a fire and an explosion that occurred at a wood processing facility in 2014. Many of the issues identified in the investigation of this incident were the same issues that would likely have been captured in a DHA, and hence could have been prevented. The remainder of this article discusses the four most common issues identified by the author in performing numerous DHAs over the last several years.

Lack of dust explosibility data

Figure 1. Example of concerning dust accumulations in building rafters.

Figure 2. Firefighter caught in a vented dust deflagration fireball (photo courtesy of OSHA.gov).

32 | WORLD FERTILIZER | JULY/AUGUST 2021

It should be clearly recognised that most materials that can combust (i.e. burn) will present a combustible dust fire and explosion hazard if dust is created from the processing of such materials. In other words, dusts generated from combustible material should be assumed to pose a combustible dust fire and explosion hazard unless proven otherwise (i.e. through testing). However, beyond identifying that a combustible dust hazard exists, facilities often do not have sufficient information on the combustibility characteristics of their dusts. Performing a simple ‘Go/No-go’ test is fundamental to confirming that a hazard exists.6 Once the determination is made that the dust is combustible, then additional explosivity parameters may be useful for quantifying the hazard and developing effective mitigation options. For example, the minimum explosible concentration (MEC) can be used to determine if the process is capable of generating sufficient quantities of airborne dust to present an explosion hazard. Likewise, the minimum ignition energy (MIE) is needed to assess the potential for static ignition

Relax, hazards, which may require operators to be bonded/grounded when performing certain operations. Kst (rate of pressure rise in a closed vessel) and Pmax (maximum pressure developed in a closed vessel) values for the dust must be determined in order to design explosion protection systems (e.g. deﬂagration venting, chemical suppression) to protect against credible explosion hazards identiﬁed in the DHA. The noted parameters vary depending upon the material involved (composition, particle size, etc.) and its concentration, so that the hazard associated with feed materials may be very different than in a dust collection system. Having the correct data is essential in order to appropriately evaluate the hazards and develop prevention and mitigation strategies.

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Lack of defined inspection and cleaning plan to meet housekeeping requirements Dust explosions may be classified as either primary or secondary in nature. Primary dust explosions typically occur within individual pieces of equipment or enclosures (baghouse, cyclone, grinder, etc.), and are generally controlled by explosion venting or chemical suppression. Secondary dust explosions are the result of dust accumulations (outside of equipment) within the facility, which are disturbed, suspended and ignited by the primary explosion, resulting in a more dangerous uncontrolled explosion inside the workplace. Loss history shows that the majority of injuries and fatalities from dust explosions are the result of secondary dust explosions (Figure 1). Control of fugitive combustible dust emissions and housekeeping outside of equipment is therefore a focus of all combustible dust-related standards, and is the key to reducing the potential for a catastrophic event. For example, in the US, NFPA 654 (the general standard that covers fertilizer processes) defines a hazardous location as an area where the accumulation of combustible dust exceeds 1/32 in. (0.8 mm) – which is the thickness of a paperclip – based on a bulk density of 75 lb/ft3 (1200 kg/m3) with a correction factor to allow for increased accumulation of lower bulk density materials. A hazardous location is deemed to exist if either the total area of combustible dust accumulations exceeding the layer depth criterion is greater than 5% of the enclosure footprint area, or the area of any single dust accumulation exceeding the layer depth criterion is greater than 1000 ft2 (approximately 90 m2). European regulations provide different but similar guidance regarding unacceptable combustible dust accumulations outside of equipment. Surprisingly, very few facilities actually create an auditable system of inspection and cleaning to meet this requirement. Some facilities periodically inspect (e.g. quarterly) and react accordingly, although local accumulations may already have significantly exceeded the identified threshold thickness within this timeframe. Other facilities simply clean on a defined frequency (e.g. annually), regardless of the amount of dust that has accumulated within this timeframe. Regrettably, some facilities neither inspect for nor clean accumulated dust on any defined schedule. Although relevant standards do not define an approach to achieve compliance, it is BakerRisk’s opinion that the most effective method is to segment the process areas into zones that can be easily inspected by a workgroup or operator, ensuring that there are no gaps between zones. An initial inspection frequency should be established (e.g. every two weeks) and the

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additional safety distance should therefore be considered.7,8 Restricted access zone warning signs and barriers should be established to prevent unauthorised personnel access. Permits should be used to evaluate potential hazards encountered by personnel working within the restricted zone, to specify appropriate PPE (e.g. ﬁre retardant clothing) and to limit the time to which personnel are exposed to this hazard.

Lack of design basis information to support explosion protection design When designing and implementing explosion protection systems (e.g. venting or chemical suppression), it is imperative that the strength of the protected equipment (e.g. dust collector) is known. The maximum explosion pressure in equipment fitted with explosion vents can significantly exceed the pressure at which the vents open, and the equipment may fail catastrophically if not designed to Figure 3. Failure of dust collector roof-to-shell seam under suppression withstand the maximum pressure. Similarly, if injection pressure. chemical suppression is implemented, the zone (including elevated surfaces) cleaned as needed when the activated suppression system pressurises the equipment as it threshold thickness is approached. For zones that generate dust injects the suppressant, and hence the equipment will fail if accumulations at a steady rate, the inspection frequency can be not designed appropriately. In one instance, BakerRisk assessed adjusted after a number of inspections have established the the capacity of a rectangular dust collector with an explosion accumulation rate. The keys to success are to maintain external suppression system and determined that the dust collector dust accumulation levels below threshold levels, develop a would fail at the roof-to-shell seam without additional reasonable inspection frequency, document the inspections and structural reinforcement, as illustrated in Figure 3; activation of cleanings and make the process work intuitively without creating the suppression system, even inadvertently, posed a significant an undue burden. An additional benefit to this zoned approach is hazard to the operators. that the responsible workgroup will likely begin to identify key Summary equipment that is contributing to fugitive dust emissions and will The identified common hazards have all been causal factors in seek methods to eliminate the source of the release (i.e. so as to actual combustible dust fire or explosion incidents that allow a decrease in the required inspection and cleaning resulted in the loss of life or severe injury, in addition to the frequencies). loss of capital assets and business interruption. A robust DHA Lack of restricted access zones around will identify such hazards and, using the guidance provided in equipment equipped with deflagration relevant governing standards, identify prevention and vents mitigation strategies that can be implemented to manage the Where a combustible dust explosion hazard has been identified associated risks. (e.g. combustible dust captured in a dust collector), a common References solution is to protect the equipment using explosion venting. 1. NFPA 652 – Standard on the Fundamentals of Combustible Dust Explosion venting mitigates the explosion pressure within the (2019 Edition). equipment so that the equipment does not fail catastrophically. 2. EX 137 ‘workplace’ Directive 1999/92/EC – Minimum requirements However, a fireball, hot gases and potentially damaging for improving the safety and health protection of workers potentially at risk from explosive atmospheres, ATEX 114 ‘equipment’ overpressures can be released through the vent (Figure 2). Directive 2014/34/EU – Equipment and protective systems Restricted occupancy zones should therefore be established intended for use in potentially explosive atmospheres. around deflagration vents to reduce the likelihood that 3. THOMAS, J.K., KIRBY, D.C., et al., Urea Dust Explosibility Testing personnel are present in the vicinity if a deflagration were to BakerRisk White Paper (2010). 4. Center for Chemical Process Safety (CCPS), Guidelines for occur in the vented equipment. A number of incidents have Combustible Dust Hazard Analysis (2017). (The author of this article resulted in injury to personnel located in close proximity to worked with CCPS to draft this guideline). explosion vents, due to exposure to the flame and burning 5. US Department of Labor Citation and Notification of Penalty, debris from the vented deflagration. Equipment controls, such as Inspection Number: 1236533, Issued 11/17/2017. 6. ASTM E1226 – 12 Standard Test Method for Explosibility of Dust E-stops, should be located outside of these zones. US and Clouds. European standards provide guidance on fireball distances from 7. NFPA 68 – Standard on Explosion Protection by Deflagration Venting vented enclosures that can be used as a basis for establishing (2018 Edition). restricted access zones, noting that locations at the edge of the 8. EN 14491:2012 Dust explosion venting protective systems (2012 Edition). fireball are not necessarily safe due to the high thermal flux; an 34 | WORLD FERTILIZER | JULY/AUGUST 2021

The evolution

OF HTHA DETECTION Brian E. Shannon and Ronald T. Nisbet, HSI Group, Inc., USA, consider the work and conclusions of a Joint Industry Project established to improve HTHA detection methods.

igh-temperature hydrogen attack (HTHA) of C and C-1/2 Mo has been a problem since the 1970s. In practically all cases it occurs after long-term service. This long incubation period poses a serious threat to plants operating with C-1/2 Mo process equipment. The degradation of the metal occurs in such a fashion that detection is difficult, and failure can occur in a short time after long-term service. Hydrogen attack is due to an internal reaction between atomic hydrogen and carbon to form methane: Fe 3C + 2H 2 → CH4 + 3Fe

At high temperatures and pressures, atomic hydrogen diffuses rapidly into the walls of pressure vessels. The pressure of the methane formed by these reactions is a function of temperatures, hydrogen partial pressure (PH2) and the activity of the controlling, most unstable carbide. Methane pressure causes cavity growth from nucleation sites along the grain boundaries. When methane forms in steel it reduces strength and ductility. The rate of material property degradation depends on the methane pressure, creep rate of the material and the fraction of cavitated grain boundaries. At high temperatures and stress, hydrogen attack and creep may well interact, as both involve formation and growth of cavities at the grain boundaries.

At a given temperature and hydrogen partial pressure, hydrogen attack will ﬁrst occur in the areas with the most unstable carbides. This is generally in or near welds. The type of carbides (Mo, Fe3C) and the carbide activity will depend on whether the welds were adequately

post-weld heat-treated (PWHT). If C-1/2 Mo is not properly heat-treated, unstable carbon steel cementite carbides (Fe3C) may also exist locally at random in the base material. Cold working also promotes hydrogen attack by increasing the number of potential cavity nucleation sites. In some cases, the progress of hydrogen partial pressure will be high enough to cause hydrogen attack through much of the wall thickness. This means that, for homogeneous C-1/2 Mo, the time between hydrogen attack at the exposed inside surface and hydrogen attack at the mid-wall thickness is comparatively short. The effect will be a general reduction in the material properties (e.g. embrittlement, increased creep rate); failure through rapid ductile tearing of the remaining unaffected material due to overload is a possibility. If unstable carbides exist inside the wall, initial hydrogen attack may occur in such locations before it occurs at the surface directly exposed to the hydrogen. Hydrogen attack normally produces intergranular ﬁssures. It is these ﬁssures that the combination of ultrasonic techniques is designed to detect. Detection is based primarily upon pattern recognition, ratios of longitudinal-to-shearwaves and attenuation measurement in the frequency domain (not the time domain). Well-developed procedures are essential to differentiate hydrogen attack from material/fabrication discontinuities.

Development of detection techniques

Figure 1. Ultrasonic displays showing level of damage.

Figure 2. Ultrasonic spectrum display. 36 | WORLD FERTILIZER | JULY/AUGUST 2021

The primary change to the Nelson Curves in the late 1980s was the lowering of the Carbon Moly (C-1/2 Mo) Nelson Curve to the carbon steel level. Prior to this change, C-1/2 Mo was considered more resistant to HTHA than carbon steel. This prompted Shell Oil Co. to research more reliable non-destructive testing methods, so as to accurately and reliably determine the condition of its equipment and monitor existing assets while upgrading the metallurgy from the existing C-1/2 Mo pressure equipment. The non-destructive evaluation (NDE) research, under the supervision of Dr David Wang at the Westhollow Technical Center, culminated in the development of the advanced ultrasonic backscattering techniques (AUBT) methodology. Scanning is performed on the external surface to detect early fissuring stages during plant outages. Prior to the introduction of these techniques, detection methods were limited to field metallography and replication (FMR). Other methods included evaluation of signal attenuation, velocity ratio and backscattering methods, all of which have difficulty distinguishing between actual attack and steel with ‘inclusions’. Shell started applying these AUBT methods in 1991. The key steps in the AUBT procedure are as follows: a pattern-based back-scattering technique is used as the initial

screening method on the external surface. Depending on the pattern observed (Figure 1), a follow-up technique is indicated to determine the cause of the backscattering signals. Velocity ratio is used only when backscatter shows uniform microstructure. Spectrum analysis uses Fast Fourier Transfer (FFT) to convert signal from amplitude to time versus amplitude versus frequency. This compares the spectrum from a suspect location with a reference spectrum (Figure 2) obtained from an undamaged area. Spatial averaging techniques may be utilised where velocity ratio and spectrum analysis have difficulty confirming through wall HTHA.

HTHA case study: Tesoro refinery In April 2010, a fatal explosion and fire occurred at the Tesoro refinery in Anacortes, Washington, US (Figures 3 and 4). The explosion was caused by damage to a heat exchanger from HTHA, which severely cracked and weakened the carbon steel exchanger shell, leading to a rupture, according to a draft report by the US Chemical Safety and Hazard Investigation Board (CSB) released in 2016.1 HSI was provided access to the damaged exchanger and applied all of the evaluation methods available, including ultrasonic phased array (UTPA) examination. The results were compared with the metallurgical and chemical analyses, and the analysis from the AUBT and UTPA examination did not correspond to the analytical results. This was a comparable result from many of the company’s previous examinations where the AUBT results were not confirmed by the laboratory findings.

Develop and validate HTHA models for FFS assessments and RBI implementations. Using this repository of samples, set up performance-based qualification of inspection technicians. A representative number of current practitioners of HTHA examination were invited to examine a diverse and representative number of HTHA damage samples gathered from refineries and ammonia plants. These NDT technicians were invited to apply all of the current NDT methods available up to this period. The conduct of these inspectors and the evaluation of their examination findings was observed and evaluated by Lavender International in Houston, Texas, US. The results provided the following conclusions: The JIP Phase 1 results highlighted unreliability across all currently known methods of detecting HTHA. The UT techniques as referenced in API 941 (8th edition) are unreliable. Doubt exists about the viability of NDT to detect HTHA. The techniques that are referenced in the current edition of API 941 missed major defects. These techniques produced a high rate of false positive results.

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HTHA Joint Industry Project Equity Engineering Group and the Materials Properties Council jointly announced a proposed Joint Industry Project (JIP) on HTHA at the American Petroleum Institute’s (API) Refining and Standards meeting in Dallas, Texas, US, in 2017. The goal of this JIP was to improve HTHA detection quantitatively, establish detection levels for HTHA and develop protocols for sizing of HTHA damage. The project was timely in light of the shortcomings of the then current technology, operator expertise and approach to the detection and assessment of HTHA – in many cases they may not provide the necessary certainty to make decisions with the level of confidence desired. The project would have the following objectives: Obtain and characterise HTHA damage in CS and C-1/2 Mo samples: pipe, plate and forgings including welds. Compare latest commercial and unique NDE methods for field detection and characterisation of HTHA damage. Determine mechanical properties of affected HTHA material from samples that are needed for fitness-for-service (FFS) and risk-based inspection (RBI) evaluations.

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PAUT secondary inspection with specific applications Careful selection of focusing. 32 or 64 element excitation. Caution: high power focus = small depth of field. TFM for verification Still in process of investigation. Encouraging initial findings. ATFM for verification Flexible conformable membranes or captive water focus. Adaptable to curved surfaces. Encouraging initial findings. AUBT (verification) Generally efficient as a simple verification method. Subtle pattern recognition necessary. Use in conjunction with one or more of the previous methods.

Figure 3. HTHA failure of exchanger vessel.

Figure 4. Vessel failure due to HTHA. Further work has been carried out under Phase 2 of the JIP and concludes that: No one method is appropriate for all applications. Advanced stage HTHA in welds is most likely to be found by a combination of time-of-flight diffraction (TOFD) and phased array ultrasonic testing (PAUT). TOFD is a vital supplement to PAUT, especially when colonies of fine HTHA may attenuate the PAUT. PAUT requires a minimum of 32 element array excitation to locate HTHA damage. PAUT is more effective when using 64 elements, but used with due caution for sensitivity and resolution. Velocity ratio is highly unstable. Attenuation can be broadly effective, but is time-consuming and often unreliable. Frequency-based analysis can be a good indicator but is not foolproof. Total focusing PAUT (TFM) and adaptive total focusing PAUT (ATFM) are available for confirmation of corrosion. With regards to specific conclusions for damage assessment, from the Phase 2 study the following techniques were found to be more reliable: TOFD initial screening Very effective when applied by an expert technician. Requires careful selection of parameters. Experience in this technology required for data analysis. 38 | WORLD FERTILIZER | JULY/AUGUST 2021

The results of the JIP were provided to the API RP 941 committee, which resulted in the Annex E that incorporates the evaluation of the traditional examination methods and the validation of those which have been determined to be effective and will be included in API RP 941 9th Edition. API RP 941 states: “Selection of optimum inspection methods and frequencies for HTHA in specific equipment or applications is the responsibility of the “Owner-User.” ” An intensive course in the NDT methods evaluated and endorsed in the JIP, with an exit examination providing proof of successful completion of the training, is provided by Lavender International. While it is not mandated that technicians who have successfully negotiated the Lavender Training Course be required for HTHA examinations, an owner-user would be wise to entrust their examination to technicians trained and certified in the operation of the recommended NDT methods. The work of improving the early detection of HTHA continues, as does the modelling of damage using various engineering approaches. This work is being carried out with various energy and scientific organisations in conjunction with the API 941 Task Group.

Reference 1.

Chemical Safety Board, ‘CSB Safety Alert: Preventing High Temperature Hydrogen Attack (HTHA)’, (August 2016).

Bibliography 1. 2. 3.

American Petroleum Institute RP 941, 9th Edition. API RBI Recommended Practice 581, 3rd Edition. NUGENT, M., SILFIES, T., DOBIS, J.D., and ARMITT, T., ‘High Temperature Hydrogen Attack (HTHA) Modeling Prediction and Non-Intrusive Inspection Review’, paper presented at 2017 NACE Conference + Expo, Las Vegas, Nevada, US (June 2017). PILLOT, S., and COUDREUSE, L., ‘Hydrogen-induced disbonding and embrittlement of steels used in petrochemical refining’ in Gaseous hydrogen embrittlement of materials in energy technologies: The problem, its characterisation and effects on particular alloy classes, edited by GANGLOFF, R.P., and SOMERDAY, B.P. (2012), pp. 51 – 93.

PROBING FOR HTHA Daly Souissi, Olympus, Canada, explores a new strategy for HTHA inspection.

he high-temperature hydrogen attack (HTHA) damage mechanism is a critical concern in ammonia plants, refineries and other petrochemical facilities. The operating conditions (e.g. temperature, hydrogen partial pressure [HPP], stress, in-service duration, etc.) of processing equipment in these types of facilities increase the risk of HTHA occurring. Monitoring the integrity of the equipment components for HTHA is necessary to avoid failures

and accidents; however, inspecting for such damage is challenging and requires a specific strategy using a range of techniques in accordance with API RP 941. In this article, the focus will be primarily on HTHA inspection using advanced ultrasonic testing (UT) techniques, including focused phased array UT (PAUT), full matrix capture (FMC)/total focusing method (TFM) and Dual Linear ArrayTM (DLA). A specific case study will be discussed.

HTHA definition and mechanism HTHA is the result of hydrogen diffusing through steel over an extended time period. This, in conjunction with high HPP and elevated temperatures above 200˚C (400˚F), often leads to a decarburisation process that consists of a reaction between the precipitating carbon and the hydrogen that forms methane (CH4) around material grain boundaries. Methane bubbles (voids) progressively form in solid steel over time, creating stresses and fatigue that lead to microfissures and, ultimately, to cracks. In the early stages, HTHA voids typically initiate near the internal diameter (ID) and evolve, at first, to micro (50 – 100 μm) then macro (>100 μm) fissures that steadily connect and grow into larger cracks that may extend to the outer diameter (OD). The HTHA cracking stage is the most severe, as it may result in the component’s failure. It is hard to predict the HTHA evolving mechanism as it depends on several environmental factors, including HPP,

the operating temperature and the duration of the exposure, in addition to the composition of both the base metal and the weld metal.

Inspection challenges

In the non-destructive testing (NDT) industry, inspecting for HTHA is considered to be one of the most challenging UT applications due to the complexity of the damage. Detection: early stages of HTHA are very difficult to detect because of the small size of the voids, especially in thick material. Characterisation: generally, suspected indications are not easily identified as HTHA. They could be confused with base-material imperfections, other weld defects – such as porosities and inclusions – and even with noise from the material grain. Sizing: when reporting indications as HTHA, the inspector needs size information to determine the current damage stage and assess whether the component is fit for continued service. Accurately sizing micro and macro voids continues to be a challenging task, even though sizing techniques have evolved. Accessibility: when inspecting a weld for HTHA, an additional difficulty may be faced when the component’s design allows only one-sided access (e.g. weld to elbow, weld to cone, transition of thickness, etc.). A single-sided access weld eliminates the use of time-of-flight diffraction (TOFD), which is an important Figure 1. AIM wave set simulation and sensitivity index for the TFM transverse-transverse (T-T) model, using a 10L64 A31 probe mounted on a SA31 N55S wedge. technique, and leads to more signal attenuation when Table 1. Test strategy details inspecting the far side of the weld. Technique Probe Wedge No. elements/ Angle˚ FD focal law range PAUT: SW

10L64 A31

SA31 N55S

40 – 72

TFM: T-T

10L64 A31

SA31 N55S

N/A

DLA

10DL32-9.6X5-A28

SA28 N65L - FD25

0 – 80

To tackle all these challenges, it is recommended to combine several UT techniques and select adequate equipment and tools in accordance with a specific inspection strategy.

Inspection strategy

Figure 2. Location 1 – indication colonies as observed in the DLA inspection results. B-scan (side view) shows the extent to be 110 mm along the weld axis, while the S-scan shows that indications are in the near-side zone.

40 | WORLD FERTILIZER | JULY/AUGUST 2021

Generally, for a given inspection, the strategy is part of the inspection procedure and includes these technical details: inspection equipment, scan plans and patterns, calibration process, etc. An HTHA inspection strategy should be based on the latest API RP 941 guidance. API RP 941 past editions recommended several UT techniques developed in the 1980s and 1990s, including velocity ratio, frequency and spectral analysis and conventional backscattering.

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Annex E of the latest revised edition, however, recommends a new inspection approach based on TOFD, PAUT and FMC/TFM techniques using the highest practical frequencies (7.5 MHz – 10 MHz). TOFD: TOFD is the first and primary screening tool, as it is faster and more sensitive compared with other methods. Although TOFD detection can easily provide the location of indications, it does not offer a conclusive distinction between HTHA and inherent inclusions or porosities.

Highly focused PAUT Pulse-Echo (P/E): suspected indications found using TOFD are assessed using the PAUT P/E technique. Configurations should be carefully set up with adequate probes and focal laws (voltage, focus, number of elements etc.). Based on TOFD findings, the generated beams should be focused at the targeted depth to improve detection and resolution capabilities. FMC/TFM: FMC/TFM can be used as an additional confirmation method. The probe and configurations should be selected carefully to ensure the full imaging benefits of these advanced techniques. In TFM, it is important to use a modelling tool, such as the Acoustic Influence Map (AIM), to help ensure the optimal choice of probes. Transmit-Receive-Longitudinal (TRL) technique: the TRL technique, using DLA and Dual Matrix ArrayTM (DMA) probes, is a strong alternative to PAUT P/E. TRL configurations offer an improved signal-to-noise (SNR) ratio, better lateral sizing capabilities, higher depth focusing capabilities and no subsurface dead zone.

Case study: inspection for HTHA in a single-sided access weld Context Figure 3. Location 1 indications as observed in PAUT, TFM and DLA acquired data.

In this case study, tests were conducted on a carbon steel sample cut from the shell-to-head joint of an aged pressure vessel. The 50 mm thick sample contained a double V weld with non-grinded top cap. Only one side was accessible, so TOFD was used to assess the base material near the weld but could not be used to inspect the weld. Only PAUT, FMC/TFM and DLA techniques were carried out from the accessible side of the weld.

Inspection strategy

Figure 4. DLA technique data showing low-amplitude and low-density indications near the bottom cap of the weld’s far side.

Figure 5. DLA sectorial scan showing geometric indications interfering with suspected indications. 42 | WORLD FERTILIZER | JULY/AUGUST 2021

As a replacement for TOFD, an unfocused PAUT configuration was used as a primary screening tool on the weld. The resulting scans showed that suspected indications were located at depths between 30 mm and 45 mm. The focal depth (FD) was adjusted accordingly for all subsequent deployed techniques. After preliminary tests showed poor detection capabilities with longitudinal waves (LW), the PAUT P/E and TFM were set to shear wave (SW) mode. The same 10 MHz 64-element A31 probe was used for both techniques. The wave set selected for the TFM was transverse-transverse (T-T). The selection of the optimal probe and mode in TFM was based on the AIM and the sensitivity index (SI), as shown in Figure 1. An angular DLA technique was used to improve coverage and detection on the weld

far-side area. The deployed probe was the 10 MHz dual 32-element A28 probe. Its small footprint adapts to areas with restricted accessibility while maintaining a high acoustic performance and improved coverage of the weld and heat-affected zone (HAZ). The PAUT unit used was the Olympus OmniScanTM X3 32:128PR model. Table 1 summarises the probes and configurations that were used. The sensitivity level was set using a 1 mm side-drilled hole (SDH). The gain was obtained by adding 12 to 18 dB during the scan.

be electronically focused. Due to its pivoting housing, the probe has a longer focal range, which can increase the probability of detection in the far range compared with PAUT, TFM and other DLA probes. A photo of the A28 probe is displayed in Figure 7.

Conclusion The results of this study demonstrate that the DLA technique should be considered as part of HTHA inspection strategies as an additional beneficial tool in combination with TOFD, PAUT and TFM.

Results The TOFD examination of the base material revealed no relevant indications, whereas the weld inspection identified two locations containing indications with HTHA-like patterns. In the first location, indications were detected between the double V root and the HAZ of the weld in the near-side zone (accessible side). In the second location, indications were detected near the ID surface in the weld’s far-side zone and could not be confirmed as HTHA.

Location 1 As seen in Figure 2, the suspected indications have void-like shapes and are present as dense colonies along a 110 mm distance in the weld axis. No cracking is observed, and the indications were assessed to be smaller than 1 mm, which suggests that the damage is still in the early stages. As shown in Figure 3, these indications were detected by all three deployed techniques; however, a better SNR ratio and a higher resolution were obtained with the DLA acquired data.

Location 2 Figure 4 shows low-amplitude and low-density indications in the inferior area of the weld’s far side. In this area, several geometric indications are observed due to the weld’s ID surface geometric reflections, which interfere with the suspected indications, as displayed in Figure 5. Better SNR and improved detection and resolution were observed in the DLA acquired data in comparison with the PAUT and TFM data (Figure 6). The indications are smaller than 1 mm and could not be characterised as HTHA with certainty. Metallographic testing should be conducted to verify the UT interpretations.

Figure 6. Location 2 indications as observed in PAUT, TFM and DLA data.

Discussion For this inspection of a single-sided access weld with a non-grinded cap for HTHA, in addition to the inability to use TOFD, standard PAUT and TFM techniques showed detection and resolution limitations in the far-range zone (opposite side). Better results were obtained with the DLA TRL technique using the A28 probe. The angle-beam A28 probe features a pivoting hinge system that enables the transmitting and receiving elements to be as close as possible. The proximity of the arrays expands the thickness range at which the beam can

Figure 7. Photo of DLA A28 probe during manual scanning for HTHA detection.

JULY/AUGUST 2021 | WORLD FERTILIZER | 43

OPTIMISING THE SUSTAINABILITY OF

wastewater treatment

Alissa Pallagrosi, Andrea Carotti, David Lehmann and Joseph Lehmann, Saipem, look at the development of electrochemical technology designed to remove ammonia and urea contaminants from fertilizer plant process wastewater.

he abatement of emissions and implementation of sustainable processes are key targets in redefining the world economy, and are significant drivers of continuous innovation. Wastewater generated at large-scale complexes should ideally be recycled and re-used or, when that is not feasible, treated so that it has a near-zero environmental impact. One area of particular concern is wastewater that is rich in nitrogen eluates. This is typical of effluent from many industrial and municipal plants, with nitrogenous fertilizer plants being a prime example. Such wastewater is associated with severe environmental impacts, including eutrophication of surface waters, toxic phenomena and decline in biodiversity. Ammonia is the main contaminant of concern, being extremely widespread and toxic at even low concentrations. The treatment technologies that are currently available are complex, costly and unreliable; as a result nitrogen-rich wastewater remains a major ‘pain point’ of the fertilizer and similar industries. In response to the sustainability challenge and to the increasingly urgent need for effective and economically feasible solutions, Saipem S.p.A. sought to find a solution to the issue of nitrogen-rich wastewater. Particular attention was paid to novel electrochemical technologies, in line with the ‘Emerging wastewater treatment techniques’ defined in the 2016 BAT review.1 In 2017, following a rigorous evaluation process, the company established a collaboration with Purammon Ltd., a technology start-up specialising in electrochemical technologies and processes, to commercialise a new electrochemical technology for the combined removal of ammonia and urea contaminants from process wastewater: SPELL. The technology quickly and cost-effectively transforms ammonia and/or urea into their harmless elemental components (e.g. gaseous nitrogen) with no sludge or other byproducts. The technology has been commercially implemented (Figure 1) and further engineered up to a full-scale package application, capable of satisfying all applicable international industrial standards and the most stringent environmental requirements. It is simple, modular, robust and stable under volatile operating conditions. The SPELL technology is based on an electrolytic reactor packed with electrodes coated with special catalysts that selectively react with nitrogen molecules when an electrical current is applied. These reactions continuously remove the contaminants as the wastewater flows through the reactor. An illustration of a typical application of the system for direct removal of ammonia from the wastewater of fertilizer plants is presented in Figure 2.

The treatment unit consists of the reactor and a degassing tank for separation and discharge of generated gases, complete with blower unit and pumps. A ﬁltration unit can be installed upstream, if required, to reduce suspended solids. Chemical dosing packages can be included, if necessary, to balance water conductivity and alkalinity. Figure 3 represents a typical process scheme for the technology deployment. The untreated wastewater coming from the production process feeds the electrochemical reactor, where ammonia and urea contaminants are oxidised into inert nitrogen, carbon dioxide and hydrogen (Equations 1 and 2); these can be safely emitted into the atmosphere according to the following formula: 2 NH4+ → N2 + 4H2

(Equation 1)

CO(NH2)2 + H2O → N2 + 3H2 + CO2

(Equation 2)

Figure 1. Installed module on industrial scale.

Since the exposure of the wastewater to the electrolytic cells is controllable in a precise manner, the process results in efﬂuent values that are within the pollution limits imposed by environmental regulations. The following sections provide a short comparison of the electrochemical system, in terms of efﬁciency, operations and costs, with currently available technologies.

Efficiency The most commonly used treatment technology today is biological treatment. This has been used in wastewater recovery for many years and is generally accepted as covering the widest variety of application cases and combining reasonable efficiency and deployment costs. However, biological treatments are prone to the intrinsic weakness of bacteria-based processes: occasional failures due to toxic shocks, low/high temperatures, fluctuation in inflow nitrogen concentrations that inhibit bacteria, high operational complexity, potential formation of the dangerous greenhouse gas nitrous oxide and demand for higher quality of the effluent. Biological treatment is inherently inefficient, as it oxidises ammonia in two complex and sensitive steps, namely nitrification and denitrification. The first step, ammoniacal nitrogen nitrification, is performed by autotrophic specific microorganisms, which extract energy (for their life functions) from ammonia oxidation (i.e. from inorganic compounds) and not from organic pollutants. They use carbon dioxide as their source for carbon instead of organic compounds. Nitrification is an aerobic process (Equation 3). NH4+ → NO3- / 8e- per N (Equation 3) The second step, denitrification, is performed by heterotrophic common microorganisms (e.g. Pseudomonas, Micrococcus, Archromobacter, Bacillus, Spirillum) that are often present in activated sludges and operate in anoxic conditions (i.e. with low dissolved oxygen concentration <0.4 mg/l). They can use nitrate instead of oxygen for a catabolic reaction, which produces free nitrogen as a gaseous product instead of CO2 and H2O (Equation 4). 2NO3- → N2 / 5e- per N (Equation 4)

Figure 2. 15(m)X16(m) 3D plant model for a flow of wastewater of 40 m3/hr and effluent ammonia of below 1.5 mg/L, based on new electrochemical technology.

Figure 3. Process scheme. 46 | WORLD FERTILIZER | JULY/AUGUST 2021

In both industrial and municipal wastewater treatment plants (WWTPs) the eight electrons needed for nitrification (nitrogen oxidation state goes from -3 to +5) come from aeration (Equation 3), which requires energy (electricity) for its operation. The case is different for the five electrons needed for denitrification (nitrogen oxidation state goes from +5 to 0: Equation 4). While these electrons are available in municipal water that is rich with carbon, in the case of an inorganic industrial stream there is no such carbon source, and a supplement dosage is required (e.g. acetic acid or methanol) to maintain a balanced ratio between carbon and nitrogen. This is especially the case in fertilizer WWTPs, where additional carbonic compounds increase costs: for example, the acetic acid requirement for denitrification is usually higher than 3.5 kg/kgN and may produce additional pollutants that, in turn, require additional treatment steps.

By contrast, the distinctive characteristic of the SPELL technology is its simple one step reaction, which is more efﬁcient than the standard biological treatment (Figure 4). This can be observed through comparison of the oxidation reactions occurring within the electrochemical and biological treatments respectively, as follows. The electrochemical process directly oxidises ammonia through the reaction (Equation 5), which consumes three electrons per one atom of nitrogen:

The system can treat a wide range of contaminants and concentrations, from tens to hundreds and thousands ppm of speciﬁc/nitrogenous contaminants, and can be designed for the different thresholds required for different production processes and applications (Table 1).

2NH4+ → N2 / 3e- per N (Equation 5) The driving force is electrical current and, consequently, the energy consumption and associated cost is directly proportional to the contaminant load. The system does not use bacteria and therefore there is no need for external carbon inputs and no production of sludge. The ammonia and the urea are removed through a zero-order reaction that is insensitive to the ammonia and urea concentrations, including their potential fluctuations in the incoming wastewater. The reactor selectively promotes only the intended reaction. This extreme selectivity is a key differentiation of Saipem’s electrochemical technology and is achieved by the composition of the catalyst with which the electrodes are coated. The selectivity results in a high efficiency process and, by excluding unwanted reactions, avoids both unnecessary power consumption and the inadvertent generation of potentially hazardous or costly byproducts. While space does not allow for a detailed comparison with the various non-biological technologies that are available today – such as breakpoint chlorination, ion exchange, air stripping and adsorption process using activated carbon – they are also complex and the inherent efficiency advantages of the new technology over these alternatives are quite similar.

Operations In addition to the efficiency advantages described, the electrochemical system is also more stable and reliable than the biological treatment systems currently in use. Biological nitrification/denitrification occasionally fails due to toxic shocks, high organic loads or temperatures outside the range tolerable by the bacteria. By contrast, the electrochemical system is not affected by any of these issues and therefore has no associated risk of disruption.

Figure 4. Total ammonium nitrogen removal in a fertilizer application.

Table 1. Wastewater parameters required at electrochemical reactor inlet Parameter

Unit

Design Maximum Maximum basis recommended allowable

Total suspended solids

mg/l

<30

≤50

≤80

Particle size

micron

<100

≤150

≤200

Biological oxygen demand (soluble)

mg(O2)/l

<50

≤100

Hardness

mg/l as CaCO3

<2000

≤5000

Oil and grease

mg/l

<0.5

≤1

≤2

≥7

≥6

Temperature

˚C

10 – 45 10 – 50

Feed pressure

bar(g)

0.5 – 3

0.5 – 6

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Additionally, the system can accommodate virtually any level of pollutant load and is flexible in the face of pollutant load fluctuations. It automatically recirculates the effluent through the electrochemical reactor until the target outlet concentration is achieved. The electrochemical process is controllable to a precise degree, and can be automated and integrated with the production facility’s other control systems and procedures. Moreover, the system has a modular structure that can be extended to cover additional nitrogen load and/or volumetric flow to meet different plant capacities. The system has few components, meaning the footprint is typically small and minimal site preparation is required. Importantly, it can be directly integrated within industrial process trains, rather than requiring a separate post-process discharge and treatment area. It requires control of few parameters and ensures stable and constant effluent quality.

Costs As an electrochemical process, the operational expenses are primarily derived from the consumption of electricity. This is directly proportional to the actual amount of ammonia and urea present in the wastewater. The system’s typical consumption is, on average, approximately 17 kWh/kg of total contaminating nitrogen. The economics of biological and other conventional technologies are also undermined by the costs of disposing of the resulting sludge and other byproducts. By contrast, the electrochemical process is zero-discharge – it generates no sludge or other liquid or solid byproducts and therefore has no associated disposal costs. In addition, whereas biological systems require specialised operation and maintenance personnel, the electrochemical process does not. Its operation is automatable and readily

integrated into the duties of general process management resources. As a result, the overall operational cost of the electrochemical process is 40 – 70% lower than alternative solutions. Cost savings may be even higher in scenarios where signiﬁcant load ﬂuctuations or other abrupt shifts in operating conditions (e.g. after paved road drainage) would often require rebalancing with other technologies but would not have any impact on the electrochemical process. In addition to its OPEX advantages, the new technology can have major cost advantages when it comes to commissioning. It is constructed off-site and delivered turnkey within shipping containers. It is typically operating on-site within a few days of delivery, avoiding the civil engineering, permitting and extensive construction timetables typically associated with conventional systems.

Conclusion In summary, the new SPELL technology is well-suited to treating the wastewater of fertilizer plants. It is flexible with a wide variety of design constraints and implementation configurations, and can serve as either the main treatment or as polishing treatment for ammonia removal, or for removal of ammonia and urea for both greenfield and brownfield applications. From the second half of 2021 a 40 ft transportable plug-and-play unit will be available from stock for customers to test, experience and use the system at their premises. Applying electrochemical technology is an important step within the overall objective of zero industrial pollution.

Reference 1.

BRINKMANN, T., GINER SANTONJA, G., YÜKSELER, H., ROUDIER, S., and DELGADO SANCHO, L., ‘Best Available Techniques (BAT) Reference Document for Common Waste Water and Waste Gas Treatment/Management Systems in the Chemical Sector’, https://publications.jrc.ec.europa.eu/repository/handle/JRC103096 (2016).

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World Fertilizer July/August 2021 issue

Articles inside

Tackling Dust Formation, Case-By-Case

Probing For HTHA

Optimising The Sustainability Of Wastewater Treatment

Process Improvement At The Steam Valve

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