MAGAZINE | MARCH 2024
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CONTENTS 03 05 10
Malika Nait Oukhedou, Rahul Patil, and Nikolay Ketov, Stamicarbon, the Netherlands, explore how digital solutions are facilitating the fertilizer industry’s transition to a more sustainable future.
14
Hanh Nguyen, OCI Global, considers how the fertilizer industry is tackling emissions at both ends of the fertilizer chain.
21
Matt Dixon, Swagelok Company, USA, explains how modern equipment in fertilizer production facilitates faster ammonia sampling, reduces costs, and ensures employee safety.
Matt Dixon, Swagelok Company, USA, explains how modern equipment in fertilizer production facilitates faster ammonia sampling, reduces costs, and ensures employee safety.
F
ertilizer production is critical to secure adequate food supplies, but the process itself is not easy. It uses anhydrous ammonia, which must have low water content, usually between 0.2 – 0.5% to avoid significant corrosion in system components and possibly tainted end products. Consistent testing ensures there is enough water in the system to avoid corrosion and maintain product quality (Figure 1). The necessity of such testing does not make the testing itself simple for some key reasons:
Hanh Nguyen, OCI Global, considers how the fertilizer industry is tackling emissions at both ends of the fertilizer chain.
F
ood system transformation is critical in addressing the twin challenges of food security and climate change. The urgent need to drive change was recently acknowledged by the launch of the ‘COP28 UAE Declaration on Sustainable Agriculture, Resilient Food Systems, and Climate Action’, which was signed by 134 world leaders on the first day of COP to include emissions from agriculture and farming into their national plans to tackle climate change by 2025. The fertilizer industry will be central to this transformation. Each day, billions of people rely on nitrogen fertilizers, which support nearly half of the world’s food supply. They are also responsible for around 5% of total global greenhouse gas emissions (more than global aviation and shipping combined) or more than the emissions of all but the three highest emitting countries.
n It is potentially hazardous. An operator must wear the proper personal protective equipment (PPE) since ammonia has the potential to cause significant harm to workers, including burns, eye irritation, and potential death if inhaled. PPE includes goggles, gloves, respirators, and chemical suits. n It is delicate. Precision is essential in ammonia sampling and testing, and even a small procedural error can lead to inaccuracies that could put workers and product quality at risk. n It is time-consuming. The entire process of traditional ammonia testing can take up to eight hours, which can slow the production line and reduce overall production at a facility.
Decarbonising production
More than half of the world’s fertilizers are made using ammonia. Given that 99% of ammonia production is dependent on fossil fuels, the first opportunity to reduce fertilizer emissions is by switching to lower carbon and renewable ammonia production.1 The decarbonisation technological pathways focus on decarbonising hydrogen production, which accounts for the majority of emissions from ammonia production. They include: n Replacing fossil natural gas with renewable and circular natural gas from waste. n Replacing fossil hydrogen with renewable hydrogen produced from renewable electricity-powered electrolysis. n Capturing and sequestering emissions from natural gas-based hydrogen production. These technologies are
14 15
14
A New Start For Ammonia Sampling
A New Start For Ammonia Sampling
From Factory To Field
From Factory To Field
18
26
Comment News Reflected In Data
Traditional testing methods not only reduce fertilizer plant efficiency, but also expose workers to higher risks of accidental exposure. Fortunately, more modern equipment exists that can streamline testing, improve accuracy, and promote efficiency during ammonia sampling and testing.
New Possibilities
35
Corrosion Damage Control On Urea Equipment
41
Taking Action
45
Preventing Electronic Corrosion With GPF Systems
Optimising Graphite Evaporator Efficiency
Gregory C. Becherer and Joan A. Bova, CG Thermal, USA, outline the best practices for optimising graphite evaporator efficiency and reliability in phosphoric acid streams.
27
31
Raising The Bar On Production Efficiency
Maggie Rendulich, Nutrien, Canada, considers the importance of leveraging technology in order to help optimise nitrogen operations.
26
26
Tim Haugen, Quest Integrity, USA, outlines the benefits of ultrasonic-based smart pigging inspections and cleaning on steam reformer convection coils in the ammonia, methanol and hydrogen industries. Daniel J. Benac, Dorothy Shaffer, and Johan Thoelen, BakerRisk, USA and Belgium, discuss the dangers of carbamate corrosion damage and the different mitigation methodologies available for urea equipment. Julie Holmquist, Cortec, USA, explains how vapour phase corrosion inhibitor technology can help mitigate corrosion damage in fertilizer plants. Manoj Gupta and Prashant Pasale, Bry-Air, India, outline how gas phase filtration systems are preventing electronic corrosion in the control rooms of fertilizer plants.
MAGAZINE | MARCH 2024
ON THE COVER
As a leading licensor of nitrogen fertilizer technology, Stamicarbon understands that digitalisation helps increase production efficiency while reducing energy consumption, emissions, and downtime. Stamicarbon’s digital solutions turn real-time process data into meaningful information, providing plant owners and staff with insights that help take plants to new heights.
Copyright© Palladian Publications Ltd 2024. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior permission of the copyright owner. All views expressed in this journal are those of the respective contributors and are not necessarily the opinions of the publisher, neither does the publisher endorse any of the claims made in the advertisements. Printed in the UK.
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COMMENT
EMILY THOMAS, DEPUTY EDITOR
I
magine living in the world’s most sustainable city. While this might seem like a pipe dream to most of us, inhabitants of Gothenburg, Sweden, don’t have to imagine, with the city having earned this very title from the Global Destination Sustainability Index for seven consecutive years.1 Sweden appears to have been far ahead of the trend towards sustainability for many years, with the country’s government having advocated for green initiatives from as early as the 1990s. Once a humble and gritty industrial port, politicians and business leaders took it upon themselves to develop Gothenburg into the trailblazer of sustainability that it is today. The southern islands of the Gothenburg archipelago are car free, connecting people via ferries and bicycles, not to mention the fact that the city became the first in the world to issue green bonds as an incentive to invest in climate solutions.2 Whilst it might feel like the rest of the world is playing catch up, there is no doubt that the global fertilizer industry has begun to prioritise more sustainable operations, from production to distribution, in an effort to decarbonise the food value chain. A diverse cross section of producers have recently shared a flurry of updates on projects designed to reduce the sector’s environmental footprint. For instance, earlier this month, it was announced that Tecnimont would develop a green hydrogen and ammonia plant in Portugal, as part of a FEED contract by MadoquaPower2X.3 Stamicarbon is also set to deploy a low-energy design for a urea melt plant in China; the technology is based upon a reduced use of high-pressure steam, resulting in a more energy efficient operation.4 In terms of powering more sustainable fertilizer ventures, ATOME’s Central America company, National Ammonia Corporation S.A., has shared its plans to evaluate the feasibility of securing renewable electricity for the country’s first industrial scale green ammonia project.5 Set to showcase the sector’s innovations and best practices targeted towards a greener future is CRU’s 37th Nitrogen + Syngas conference, held this year in none other than the sustainable hub of Gothenburg, Sweden. The show’s agenda is packed full of technical presentations, discussing topics such as sustainable urea production processes, and revisiting heat exchange applications amidst the push for decarbonisation. With workshops dedicated to low carbon projects, the conference promises to be an exciting and inspiring experience. If you’re heading to Gothenburg for the occasion from 04 – 06 March, have a fantastic time, and don’t forget to pick up a copy of World Fertilizer while you’re there. 1. 2. 3. 4. 5.
https://goteborgco.se/en/sustainability/the-worlds-most-sustainable-destination/ www.forbes.com/sites/davidnikel/2022/09/19/7-fascinating-facts-about-gothenburg-swedenssecond-city/?sh=709d0bac1559 www.mairetecnimont.com/en/newsroom/press-releases/detail/tecnimont-maire-awarded-a-frontend-engineering-design-for-an-integrated-green-hydrogen-and-ammonia-plant-in-portugal/ www.stamicarbon.com/press-release/stamicarbon-maire-group-awarded-licensing-and-equipmentsupply-contracts-jiangsu https://polaris.brighterir.com/public/atome/news/rns_widget/story/x2vl6zw
MARCH 2024 | WORLD FERTILIZER | 3
WORLD NEWS USA OCI and Linde partner to supply clean hydrogen to blue ammonia project in the
US Gulf Coast
O
CI N.V. and Linde plc have announced a partnership in which Linde will supply clean hydrogen and nitrogen to OCI’s new blue ammonia facility under development in Beaumont, Texas. Linde will build, own and operate an on-site complex which will include autothermal reforming with carbon capture, plus a large air separation plant. The new complex will be integrated into Linde’s extensive Gulf Coast industrial gas infrastructure. It will supply clean hydrogen and nitrogen to OCI’s 1.1 million tpy blue ammonia plant, the first greenfield blue ammonia facility of this scale to come onstream in the United States. Linde will supply OCI with clean hydrogen, by sequestering more than 1.7 million tpy of carbon dioxide emissions. OCI will upgrade the hydrogen to produce blue ammonia, which allows OCI to materially reduce the carbon footprint of its downstream customers along the value chain across a wide range of industries. Linde’s total investment will be approximately US$1.8 billion, and OCI’s total investment cost is expected to be below US$1 billion, including spending on upsized utilities and available land to allow for doubling to 2.2 million tpy capacity in the future. The project is expected to start up in 2025. “The Beaumont facility will allow us to build and strengthen our world-leading blue ammonia and clean fuels platform, supplying both the US and export market with blue ammonia, an ideal solution to decarbonise hard-to-abate sectors such as agriculture, power and marine fuels at a competitive cost,” said Ahmed El-Hoshy, Chief Executive Officer of OCI N.V. “Linde’s expertise in managing large-scale and complex engineering projects, and safely and reliably delivering industrial gases, made the company a solid choice as a partner for this project.” “Linde’s capabilities are already enabling the transition to a low carbon intensity economy,” said Sanjiv Lamba, Chief Executive Officer, Linde. “Our strategy is to support decarbonisation by working with off-takers, like OCI, to safely and reliably supply low-carbon industrial gases at scale. With Linde’s track record in successfully executing complex projects, its extensive pipeline network, and support from the US Inflation Reduction Act, the company is well positioned to secure many more clean energy projects.”
EUROPE Fertilizers Europe: EU 2040 climate target is make or break for a competitive
low-carbon fertilizer industry
T
he European fertilizer industry is uniquely placed to enhance both the sustainable food systems with low-carbon fertilizers and the EU hydrogen economy, with clean ammonia acting as hydrogen facilitator. It is paramount that the EU puts its industrial strategy at the forefront, providing fertile ground for green investments in Europe. A successful transition to renewable and low-carbon fertilizer production can only materialise if European producers remain globally competitive. “Today, our industry faces one of the most severe economic downturns in years, with volatile and high gas prices and surging carbon intensive imports negatively impacting our competitiveness. Halted production, job losses and investment leakage are among the consequences the European fertilizer industry is already facing. Ensuring a compelling business case for decarbonising sectors vital to Europe’s Strategic Autonomy has never been more important,” said Antoine Hoxha, Director General of Fertilizers Europe. Hoxha underlined, “European fertilizer producers have the ambition and the plans to deliver high emission reduction to continue producing, investing and thriving in Europe. In this regard, we call on the European Commission to recognise the scale of this challenge and the necessity to unlock funding towards decarbonisation of existing assets, ensure access to affordable low-carbon and renewable energy and develop a supportive regulatory framework. He added, “It is good news that CCS/U has been recognised as an important decarbonisation pathway, vital for hard-to-abate sectors such as fertilizers”. “The cost of decarbonising our sector exceeds €80 billion. This transition will simply not materialise without a substantial and targeted financial support for our sector and a close collaboration across the value chain to create a booming market for low-carbon food and fertilizers,” said Hoxha. “Our industry is committed to support farmers in implementing sustainable nutrient management practices. To this end, EU and national policies must incentivise an uptake of digital tools, new products and advisory services. This will ensure that EU farmers have access to cutting-edge technologies, enabling them to maximise the efficiency of nutrient application while mitigating scope 3 emissions from agriculture,” he concluded. MARCH 2024| WORLD FERTILIZER | 5
WORLD NEWS NEWS HIGHLIGHTS
Tecnimont (MAIRE) awarded front-end-engineering design for integrated green hydrogen and ammonia plant in Portugal EPA approves construction of underground injection wells to store carbon from fertilizer production Pivot Bio appoints Jim Collins to its Board of Directors
Visit our website for more news: www.worldfertilizer.com
6 | WORLD FERTILIZER | MARCH 2024
COSTA RICA ATOME announces progress on Costa Rica
green fertilizer project
A
TOME’s Central America company, National Ammonia Corporation S.A., has entered into a framework collaboration agreement with Instituto Costarricense de Electricidad, the Costa Rican state power company, to evaluate feasibility for the power supply to a green ammonia and fertilizer project. The agreement is a necessary and significant first step in securing 100% renewable baseload electricity for the country’s first industrial scale green ammonia and fertilizer project. The endorsement from the President of Costa Rica, Mr Rodrigo Chaves, along with key members of his cabinet, demonstrates the commitment to attracting foreign direct investments and a recognition of ATOME’s proven strategy of developing fertilizer projects with significant local impact. Costa Rica is an optimal location for green fertilizer production with its existing renewable power, premium agricultural industry, and strategic regional position combined with access to both Pacific and Atlantic Ocean ports. The project will be of a similar size to ATOME’s Villeta Project, leveraging the key learnings to date, and further validating the company’s strategy for replicating and deploying green fertilizer production at scale. Olivier Mussat, ATOME’s CEO, commented: “Within a year since the creation of NAC, thanks to the significant progress on our Villeta project and our strong local team led by Cavendish SA, we have been able to establish an excellent working relationship with ICE with the aim of building Costa Rica’s first green fertilizer facility.” “There is a substantial local market for the fertilizer we intend to produce as well as being strategically located to access global markets. Costa Rica is viewed as a prime investment destination with significant existing foreign investors such as Intel, Microsoft, and Amazon.”
USA Nano-Yield introduces nanotechnology-based
fertilizer coatings
N
ano-Yield has introduced its product NanoCote™, a nanotechnology-based granular fertilizer coating. The product is engineered to complement existing fertilizers, elevating the performance of the granular fertilizer industry. Nano-Yield CEO and CoFounder, Clark Bell, said: “We are thrilled with the development of NanoCote over the past several years. Through extensive lab and field trials, we have harnessed the incredible potential of nanotechnology to enhance every aspect of the farming experience when added to granular fertilizers.” Nano-Yield President and COO Mark Slavens, said: “Our team is proud to have engineered this technology in a way that is seamless for blending operations. You can spray it on any type of dry granular fertilizer. It dries very quickly without heat or any other specialised equipment.” Director of Research and Development, Garrett Olsen, commented: “Our goal was to create a user-friendly formulation that maximises plant nutrition. Every component in NanoCote products serves a purpose and drives the entire formulation.”
WORLD NEWS DIARY DATES Nitrogen + Syngas 2024 Conference & Exhibition 04 – 06 March 2024 Gothenburg, Sweden events.crugroup.com/ nitrogenandsyngas/home
Nitrogen + Syngas USA 2024 15 – 17 April 2024 Oklahoma, USA
events.crugroup.com/nitrogenusa/ home
ACHEMA 2024 10 – 14 June 2024 Frankfurt, Germany achema.de/en
Turbomachinery and Pump Symposia 2024 20 – 22 August 2024 Texas, USA tps.tamu.edu
ANNA 2024 29 September – 04 October 2024 Montréal, Canada annawebsite.squarespace.com
Sulphur + Sulphuric Acid Conference & Exhibition 2024 04 – 06 November 2024 Barcelona, Spain events.crugroup.com/sulphur/ home
CHINA Stamicarbon awarded licensing and equipment
supply contracts for urea plant
J
iangsu Huachang Chemical Company has awarded Stamicarbon licensing and equipment supply contracts for a urea melt plant in China. This urea melt plant will serve as a replacement for an outdated facility of similar capacity and will utilise the existing prilling unit. Stamicarbon will provide the license, proprietary equipment, including high-pressure equipment made of super duplex stainless steel, and associated professional services. The main advantage of Stamicarbon’s low energy design, which will be utilised in this plant, is that the high-pressure steam is being used three times instead of two, making the process more energy-efficient than the conventional CO2 stripping. This heat recovery scheme results in a 35% reduction in steam consumption and a 16% decrease in cooling water use. With two plants currently in operation, the low energy design is demonstrating energy savings in the market. “Sustainability is at the core of our company, and when looking to replace our outdated urea plant, we were specifically seeking the most energy-efficient solution to help us reduce emissions and energy consumption. With ultra-low energy technology, we expect to achieve a substantial reduction in steam and water consumption, contributing significantly to our sustainability goals. We look forward to a successful and mutually beneficial partnership with Stamicarbon as we work together on this project,” said Mr. Hu Bo, the Chairman of Jiangsu Huachang Chemical Company. “At Stamicarbon, we are committed to pioneering sustainable solutions, and the ultra-low energy design stands out as a testament to our dedication. We believe that this project marks a significant milestone in Jiangsu Huachang’s journey towards a more sustainable and efficient future. This project marks the ninth worldwide implementation of our groundbreaking technology, a testament to its global recognition as the industry’s benchmark for energy consumption and efficiency,” said Pejman Djavdan, Stamicarbon CEO.
USA Ecolab ranks on CDP ‘A list’ for water and climate leadership
E
colab Inc. has announced that it has been recognised for leadership in corporate transparency and performance on climate change and water security by global environmental non-profit CDP, securing a place on its annual ‘A List’. Having achieved an A-rating for both climate change and water security, Ecolab is in the top 1% of more than 23 000 companies assessed using data from CDP’s 2023 Climate Change and Water Security questionnaires. “Ecolab grows both our business and impact on the world by doing the right things the right way,” said Christophe Beck, Chairman and CEO, Ecolab. “Our continued leadership on climate change and water security, as evidenced by our double ‘A’ ratings by CDP, goes to show how Ecolab’s more than 48 000 associates are fulfilling our mission to protect the world’s most vital resources, together with our customers.” The company helps nitrogen producers minimise water risk, maximise performance and optimise safety, reliability and profitability.
8 | WORLD FERTILIZER | MARCH 2024
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Malika Nait Oukhedou, Rahul Patil, and Nikolay Ketov, Stamicarbon, the Netherlands, explore how digital solutions are facilitating the fertilizer industry's transition to a more sustainable future.
A
s chemical plants grow, not only in size but in complexity, the concept of the 'digital plant' is emerging as a game changer, reshaping how technology empowers a connected workforce, driving efficiency, and fostering innovation.
Embracing change
Historically, the chemical industry has continually strived to enhance productivity through intelligent and innovative approaches. The goal has always been to increase outcomes with optimal effort and cost, a principle that remains unchanged in the digital age. However, when it comes to the digital evolution rapidly transforming our world, fertilizer producers have been more conservative compared to other heavy industries. One of the reasons behind that is the complexity of the underlying chemical reactions 10
and mechanisms, which make creating a plant model a complex task requiring a fundamental understanding of the process thermodynamics and reactions phenomenon, including the kinetics and equilibria. Despite this conservative approach and its challenges, it is quite evident that digital solutions are capable of not only creating additional revenue streams, but also making strides toward minimising environmental impact and improving safety. Both considerations are crucial in today’s quest for a sustainable future. This evolution mirrors the core principles of Industry 4.0, where the synergy of people, processes, and technology plays a pivotal role. The transparency of information, coupled with the necessity for real-time insights, is reshaping the way decisions are made – favouring a data-driven approach.
11
Types of plant models
To gain comprehensive process insights, fertilizer producers are increasingly turning to virtual plant models, both in offline and online applications. These models can be knowledge-driven (first principle models), requiring a thorough understanding of underlying mechanisms. Alternatively, these models can be data-driven and rely on experimental data for situations with a limited understanding of the physical process. The grey-box model merges simplified first principles with data-driven elements for an efficient balance. The Stami Digital Process Monitor's plant model is knowledge-driven with predictive accuracy. It encompasses a mathematical framework including mass and heat transfer equations, and reaction kinetics, encapsulating the plant’s entirety with over 5000 equations. A developed equation-oriented flow sheeting programme tackles these large-scale calculations.
data is securely transmitted to the process monitor engine in the cloud. The process monitor feeds real-time data into the plant model, calculating key performance indicators (KPI) such as plant load, energy use, and emissions, along with soft sensor key variables that are displayed on a dashboard, making them accessible to plant operators and stakeholders. As illustrated in the Figure 1 where arrows indicate the direction of information flow, there is no closed-loop system-to-system communication. Under no circumstances does the process monitor directly intervene in the DCS; the plant's DCS system is exclusively controlled by plant operators and serves solely as a data source for the plant model. This concept adheres to the highest information security standards, in compliance with Stamicarbon's ISO 27001 certification, a global standard for information security management.
Digital plant architecture
Designing the process model
n
Plant Model
27001
Process Monitor Engine
C e r tifi e d
Unidirectional
OR Plant Historian
Plant
Creating the plant model involves a consulting phase and a data reconciliation phase. Initial steps include interviewing plant experts to harness operational insights and historical data. This phase yields valuable insights, including sensor evaluations, plant constraints, and operation assessments. In the data reconciliation phase, historical DCS data is collected and used to refine the model, ensuring its accuracy in representing the process. This stage involves correcting deviations and updating model parameters, akin to a feedback process in control engineering. An example of model validation is depicted in Figure 2, showcasing the correlation between model-predicted and actual DCS readings of reactor temperatures, a crucial variable in urea synthesis. Post-validation, the process monitor offers real-time insights on KPIs and soft sensor key variables, aiding in maximising efficiency and boosting production.
urity M Sec a en gem t na
Informat io
The monitor offers features such as real-time monitoring of key variables, reliable emissions tracking, sensor duplication, and dynamic graphical interfaces, collectively leading to significant savings and enhanced efficiency, reliability, and safety. The architecture of the monitor is tailored to customer needs, offering functionalities like real-time optimisation, predictive control, data reconciliation, and comprehensive monitoring systems. The real-time plant
DCS
Plant Historian
Plant Historian
Enterprise Historian
Connectivity Software
Process Monitor
Operators
Figure 1. Stami digital process monitor architecture. Reactor temperature degr.C
Key variables
Here’s an oversight of all key variables.
Equipment: stripper Stripper efficiency
186
Stripper tube load 0.78 mol/mol
06-06-2019 21:05:09
06-06-2019 21:05:09
73.97 kg/h/tube
185 Equipment: LPCC
184
LPCC N/C ratio 06-06-2019 21:05:09
183
LPCC crystallization temperature 1.912 mol/mol
06-06-2019 21:05:09
79.3673 degC
Equipment: reactor
182
Reactor H/C ratio 06-06-2019 21:05:09
181
180
Reactor inert pressure 0.4610 mol/mol
06-06-2019 21:05:09
633671.113 bara
Reactor yield 06-06-2019 21:05:09
Soft sensor key variables
Key variables (KVs) define the technical and economic performance of the urea process. Traditionally determined by offline laboratory analysis, process modelling aims to provide operators with real-time, accurate estimates of these KVs. The soft sensors can be developed and adjusted to specific customers' needs and constraints. ‘Soft’ refers to the software (the process model) that generates the N/C value (Figure 3). 100.59 t/h
Troubleshooting with knowledge
LPCC N/C ratio (mol/mol)
time DCS MODEL
2.0 1.5
Oct 17, 2019, 1:04:00 PM LPCC N/C ratio (mol/mol): 1.727
1.0
Figures 2 & 3. Reactor temperature validation (left) and soft sensor key variables (right). 12 | WORLD FERTILIZER | MARCH 2024
After the introduction of process monitoring on-site and the data having been
kg/h
Compressor load
60000 made available, Stamicarbon will have virtual meetings with the 50000 customer on a regular basis. In these 40000 meetings, as a part of the ADVANCE ConsultTM service 30000 portfolio, the process data of the past Operator forgot to close period will be evaluated and discussed 20000 flush valve with the customer’s operational 10000 specialists (operators, supervisors, process and process control 0 0 200 400 600 800 1000 1200 1400 engineers etc.). hours These sessions help operational Root cause: Wrong density compensation for orifice DCS Benefit: Revamp possibilities MODEL specialists understand the meaning of the KVs and how to use them to Figure 4. Troubleshooting examples. the benefit of the customer in model calculations (Figure 4). This comparison helps in promptly optimising plant performance. In the discussions, suggestions identifying and rectifying operational issues, thereby preventing for improvement of the operations in terms of capacity production losses. increase, emission reduction and energy efficiency are given. This data will provide operational insights, e.g., identifying unwanted operations that may affect the Conclusion lifetime of equipment. Stamicarbon, together with sister companies from MAIRE Group These sessions have been effective in detecting – KT and Tecnimont – is working on developing a digital toolbox measurement errors, equipment bottlenecks, and inefficiencies. for the process industry to optimise plant Additionally, operating strategies developed based on operations. The Stami Digital portfolio, comprising a suite of operational insights from the model data have proven efficient digital services, can improve plant load and reduce in practice. energy consumption. With training, operational specialists are equipped to In the face of tightening regulations and evolving market identify unwanted operations that may affect the lifetime of demands, digital solutions have proven themselves to be crucial equipment and troubleshoot. This can, for instance, be done by for optimising plant efficiency, minimising environmental impacts, comparing plant DCS (distributed control system) values with and facilitating the industry's transition to a sustainable future. t/h 50
45 40 35 30
25 20 15 10
5
1 19 37 55 73 91 109 138 156 174 194 212 230 271 289 307 325 343 361 379 397 415 433 451 469 487
0
time DCS
MODEL
PART OF YOUR PROCESS Exceptional Energy Recovery & Process Solutions by SCHMIDTSCHE SCHACK For processes with high temperatures and high pressures to ensure maximum reliability and efficiency. Discover our share by scanning the QR-Code or meet us at the ACHEMA 2024 in Hall 4.0 at booth F23 !
From Factory To Field
14
Hanh Nguyen, OCI Global, considers how the fertilizer industry is tackling emissions at both ends of the fertilizer chain.
F
ood system transformation is critical in addressing the twin challenges of food security and climate change. The urgent need to drive change was recently acknowledged by the launch of the ‘COP28 UAE Declaration on Sustainable Agriculture, Resilient Food Systems, and Climate Action’, which was signed by 134 world leaders on the first day of COP to include emissions from agriculture and farming into their national plans to tackle climate change by 2025. The fertilizer industry will be central to this transformation. Each day, billions of people rely on nitrogen fertilizers, which support nearly half of the world’s food supply. They are also responsible for around 5% of total global greenhouse gas emissions (more than global aviation and shipping combined) or more than the emissions of all but the three highest emitting countries.
Decarbonising production
More than half of the world’s fertilizers are made using ammonia. Given that 99% of ammonia production is dependent on fossil fuels, the first opportunity to reduce fertilizer emissions is by switching to lower carbon and renewable ammonia production.1 The decarbonisation technological pathways focus on decarbonising hydrogen production, which accounts for the majority of emissions from ammonia production. They include: n Replacing fossil natural gas with renewable and circular natural gas from waste. n Replacing fossil hydrogen with renewable hydrogen produced from renewable electricity-powered electrolysis. n Capturing and sequestering emissions from natural gas-based hydrogen production. These technologies are
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all available today but are at various stages of deployment and have higher costs compared to conventional fossil production. Therefore, to catalyse ammonia production, decarbonisation in innovative approaches that will bridge 'green premiums' are needed, while technology is scaled and infrastructure is developed that will ultimately bring the cost down. Europe and the US have set examples by providing demand and supply incentives, respectively, for low carbon and renewable ammonia production. Pioneers are needed to take the first steps in proving its feasibility and set an example for others to follow. OCI Global produces renewable ammonia from renewable electricity, and bio-ammonia from waste, and is building a 1.1 million tpy low carbon ammonia facility in Texas, which will begin production in 2025. This renewable and low carbon ammonia can be used to make lower carbon fertilizers. Renewably produced CAN and urea/UAN both achieve a carbon intensity reduction of between 50 – 70% compared to conventional production. 2023 was significant in terms of partnerships and pilots that have provided proof of concept for the industry in its decarbonisation journey. These include partnerships to pioneer the production of lower carbon wheat flour for use in everyday essential products, like bread.
Minimising emissions on application
Tackling the production end of the value chain will not be enough. One of the key objectives of the declaration is to contain and reduce the harmful impacts of agriculture, and given that two thirds of ammonia-based fertilizer emissions are generated after the fertilizer has been applied to the field, tackling emissions upon application will be key.2 Reducing emissions requires correct stewardship of fertilizer use to improve nitrogen use efficiency (NUE) and reduce both
nitrous oxide emissions and nitrate leaching. The correct use of fertilizers can also protect soil health, as misuse can contribute towards acidification, degradation or leaching into water supplies. Companies are now working with industry associations to educate farmers on fertilizer application and storage, provide digital resources, and encourage sustainable farming. This includes supporting the 4R Nutrient Stewardship programme, which includes the right fertilizer source applied at the right rate, the right time, and the right place for a crop. Another way the fertilizer industry can support climate efforts is through the development of more advanced products. The use of urease and nitrification inhibitors can slow the conversion of nitrogen fertilizers to other nitrogen compounds in the soil, reducing the risk of loss through leaching or denitrification and thereby increasing the NUE of fertilizers. Many studies over the years have shown that inhibitors consistently reduce nutrient losses, nitrate leaching and nitrous oxide emissions.
Regulation can support a sustainable future for agriculture
At both ends of the value chain, the missing piece is regulatory support. Transitioning to lower carbon and renewable alternatives will cost more initially as the industry scales infrastructure, uses more expensive feedstocks, incorporates new technologies, and adjusts to new ways of working. The responsibility for shouldering that initial cost cannot fall on a single part of the ecosystem, and change will not be seen soon enough to face the twin challenges of climate change and food security if action relies on the voluntary efforts of a handful of pioneers. This is why it is encouraging to see the declaration highlight the need for specific regulation that spreads the cost across the whole value chain in a clear and simple way that incentivises the industry to switch to low carbon and renewable alternatives and supports increased use of advanced, more efficient fertilizers.
Innovating together for impact
Figure 1. OCI team members on site in the US.
With the world’s population expected to grow by another fifth to just under 10 billion around 2050 and increasing pressure on arable land, fertilizers will only become more significant. At the same time, the need to reduce emissions is urgent, and while agriculture has a responsibility to play its part, regulators need to provide the supporting frameworks to make that happen in a way that protects farming communities and global food security. The launch of the 'COP28 UAE Declaration on Sustainable Agriculture, Resilient Food Systems, and Climate Action’ and the support of 134 country leaders is a positive sign, but more is still required. At the point of writing, the Global Stocktake of COP28 does not include actions on food systems transformation. Only by acting together across the public and private sectors – and at both ends of the fertilizer value chain to reduce emissions from production and in application – can the impact of these interventions be maximised to ensure the sustainable use of nitrogen fertilizers as they play a crucial role in growing food for future generations.
References Figure 2. Decarbonising the production of ammonia via lower carbon feedstocks.
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1. 2.
BloombergNEF ammonia whitepaper. www.cam.ac.uk/research/news/carbon-emissions-from-fertiliserscould-be-reduced-by-as-much-as-80-by-2050
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Raising the bar on production efficiency efficienc y T
he Nitrogen Real-time Operations Center (NROC) in Loveland, Colorado, has been set up to troubleshoot and optimise major nitrogen production facilities across North America and Trinidad. Established by Nutrien, the NROC uses technology to bring together data in a new way to help support its nitrogen sites. Data is collected from all of the sites and is made accessible to the NROC. This allows the NROC team to collaborate with the sites, thereby increasing 18
their knowledge and visibility and, in turn, reducing downtime, increasing performance and minimising the time it takes to complete day-to-day tasks. The team of specialists who work at the NROC remotely support the nitrogen sites by connecting to engineering systems, processing data and leveraging specialised knowledge and technologies at a multi-site scale. Each day, they review operational data to identify opportunities for process optimisation, and their ability to view all sites simultaneously allows them to share best
Maggie Rendulich, Nutrien, Canada, considers the importance of leveraging technology in order to help optimise nitrogen operations.
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practices and lessons learned across the network. If the specialists notice an issue impacting only one of the facilities, they can work directly with the site team to identify and implement a solution. The team of experts working at the NROC includes a data scientist and a technology support team, who have helped delevop the tools and technology that the NROC utilises, and they continue to support the daily maintenance of all NROC systems. The centre also provides an extra set of eyes that is familiar with site equipment and current operations status, which is helpful to site operations during key moments. Real-time support has been especially beneficial during startup monitoring, root cause analysis of process abnormalities, and post startup optimisations. The NROC’s technology platform is accessible via multi-screen workstations, and has the ability to monitor all sites outside of the NROC control room via a laptop and secure
MFA connection. This system provides access to all relevant sensors and measurements across the company, equipment information and metadata, and simulation information. Artificial intelligence (AI) and machine learning are also being used for advanced analysis and predictive failure detection. The technology and systems in place enable fast access to this by a centralised domain expert. This virtual environment serves as a digital twin to all information available at each of the sites. Creating a secure and reliable pipeline to access the large volume of data was a huge challenge, and developing the custom-built systems and interface to enable the experts to quickly access and effectively process and analyse this data was a significant lift – requiring collaboration from operations, engineering and digital technology teams. Now, with the proper infrastructure in place, the NROC is helping to raise the bar for monitoring and data analysis. As the world changes, Nutrien has placed importance upon creating a centralised place where data can be accessed, viewed, and transmitted across its nitrogen facilities. The NROC is helping to enable early collaboration and decision making, thereby creating substantial value for the business.
Optimising the ammonia process
Figure 1. The team of specialists at the NROC are stationed in a high-tech operations hub that allows them to remotely support Nutrien’s nitrogen sites. 20 | WORLD FERTILIZER | MARCH 2024
One of the focus areas of the NROC is the optimisation of the ammonia process. There is a suite of software applications that are fully integrated within the centre, which creates a smooth transition for the NROC subject matter experts to manage data efficiently between applications at different stages of monitoring. The NROC is designed to reduce the time facilities spend not producing, or producing less than their full capability, by detecting failing equipment sooner, identifying root causes of failures more quickly, and enhancing the monitoring of equipment so sites can run closer to optimum operating points. An example of the NROC in action is when an AI machine learning algorithm detected process abnormalities in real-time. An alert in the NROC dashboard indicated an abnormality at Nutrien's Nitrogen facility in Fort Saskatchewan, Alberta. The custom application, developed specifically for the NROC engineers, is designed to display all data associated with the equipment that the alert stemmed from. The issue was able to be viewed and the next steps were quickly determined. The data pinpointed a water leak on a heat exchanger at the site. The leak was not in a critical state, and was able to be resolved easily because it was in the early stages. This allowed the site to make the necessary repairs on the heat exchanger, conveniently during a scheduled turnaround. Turnarounds are planned activities that occur every few years to replace equipment, complete preventative maintenance, conduct regulatory inspections and implement safety or operations improvements. The team at Fort Saskatchewan was also recently discussing ideas for plant optimisation. A review of the site was performed remotely from the operations centre, where detailed, real-time observations and recommendations for the team were made to improve operational performance, efficiency and safety, and helped them achieve production improvements at the site. This highlights the connection between technology and collaborative teamwork.
Optimising graphite evaporator efficiency
Gregory C. Becherer and Joan A. Bova, CG Thermal, USA, outline the best practices for optimising graphite evaporator efficiency and reliability in phosphoric acid streams.
I
n the concentration of phosphoric acid, the evaporator is a critical controlling component for the production rate. Optimising its efficiency and operating procedures helps ensure maximum productivity within the evaporator and avoid unnecessary downtime and unanticipated plant shutdowns. Regardless of which material is used in the construction of an evaporator, the overall performance is dictated by the following basic heat transfer equation:
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Q = A x U x LMTD
n n n n
Where, Q = Amount of heat transferred. A = Heat transfer area of the evaporator. U = Overall heat transfer coefficient. LMTD = Log mean temperature difference.
In the case of the phosphoric acid shell and tube evaporator, the objective is to optimise the amount of heat transferred from steam flowing through the shell, to the acid flowing counterflow through the tubes, using fixed heat transfer area, 'A'. To accomplish this, one must consider practical ways to maximise the overall heat transfer coefficient, 'U', and the temperature difference, 'LMTD'. The U-value is defined as the reciprocal of the overall resistance to heat transfer from the shell or steam side of
Figure 1. U-value vs tube velocity.
Figure 2. Tubes on this graphite heat exchanger are replaced
in-house after excessive fouling resulted in tube breakage during service at a phosphoric acid plant. 22 | WORLD FERTILIZER | MARCH 2024
the unit, across the tube and into the process side acid stream. It has four components and is defined by the following formula: 1 U= L/K + 1/hi + 1/ho + F n n n n n
Where, L = Tube wall thickness. K = Thermal conductivity of tube material. hi = Tube inside film coefficient. ho = Tube outside film coefficient. F = Fouling factor.
In order to maximise the U-value, the tube thermal conductivity and tube outside and inside film coefficients should be maximised, while the process fouling should be minimised. Though tube thermal conductivity does have an important role in a tube's ability to resist thermal stress damage and fatigue failure, it plays a minor role in the overall heat transfer efficiency, in that it typically only accounts for about 3% of the overall resistance. Even a significant increase in the tube’s thermal conductivity will have only a minor effect on the overall U-value. Therefore, the other three components (outside and inside film coefficients and fouling) will be the focus. In a properly designed steam system where saturated steam is utilised, the outside film coefficient is relatively high, typically four to six times greater than the inside film coefficient. This results in the outside film coefficient being a smaller component to the overall resistance. However, there are commonly found practices in steam operating systems that can reduce the outside film coefficient drastically. Included in these practices is the use of superheated steam and poor condensate removal. Not only do these two practices have a dramatic effect on evaporator performance, but they can also cause severe mechanical damage in the evaporator based on creating either high mechanical and thermal stresses or dangerous vibration loading. Superheated steam is normally a result of poor control of the desuperheater. Desuperheating is the process in which superheated steam is restored to its saturated state. There are at least two issues with using superheated steam vs saturated steam that need to be considered. First, in the superheated state, steam has an extremely low film coefficient. Until the saturated steam temperature is met within the tubes, the portion of tube subjected to the superheated steam is basically lost heat transfer area. Depending upon the degree of superheating, this could result in a 20% lost heat transfer area. Secondly, the specific volume of superheated steam is much greater than saturated steam. This results in much higher velocity in the shell than what it was designed for, and this can lead to a dangerous vibration situation. Lastly, the higher steam temperature leads to higher tube wall temperature.
www.zwick-armaturen.de
tube wall. The higher velocity does not erode the graphite tube and results in reduced fouling rates and higher heat transfer efficiency. An increase in fluid velocity from 2 – 10 fps increases the U-value by more than 50% (Figure 1). It is recommended that the tube side velocity is increased to a practical limit, based on installed pumps and acceptable system pressure drop limitations, keeping in mind that pressure drop is a squared function of the velocity. Maintaining the proper pressure level on the process side of the evaporator is a critical aspect of ensuring the overall effectiveness of the heat transfer process. The importance of preventing the acid within the system from vaporising within the tube cannot be overstated. Vaporisation is detrimental to the inside film coefficient for several reasons. Firstly, when acid vaporises, it introduces a phase change within the tube, leading to a significant reduction in heat transfer efficiency. The latent heat associated with vaporisation consumes energy without contributing to the desired heat transfer processes. Secondly, vaporisation disrupts the flow patterns and turbulence near the tube wall, hindering the convective heat transfer that is crucial for achieving a high inside film Film coefficient coefficient. The formation of vapour pockets can create In properly operating steam evaporator systems, the tube insulating layers, impeding thermal contact between the fluid inside the film coefficient can account for as much as 50% of and the tube wall. This results in reduced overall heat transfer the total heat transfer resistance. Maximising this value can rates and compromises the efficiency of the system. have a positive effect on the overall heat transfer coefficient. The LMTD is a direct function of the steam temperature. It is a function of the tube dimensions, fluid physical The higher the steam pressure, the higher the LMTD, or properties, and the flow rate or velocity, with velocity being driving force behind the heat transfer. This relationship is the most controllable, and having the greatest influence. important to consider, as it relates to fouling since higher Historically, up until about 30 years ago, the maximum steam pressure also increases the wall temperature, resulting tube side design was in graphite evaporators in the 3 fps in increased fouling rates. (feet per second) range. The thought was that anything higher Given the propensity for fouling in phosphoric acid would cause erosion in the tube. The current practice is to evaporators, consideration must be given to methods of design for 10 fps velocity, enhancing the turbulent flow at the minimising the potential and managing the unavoidable. By increasing the acid recirculation rate, the fouling rate is decreased. Higher recirculation rates prevent stagnant zones within the system that facilitate fouling. Continuous flow and agitation also facilitate efficient heat transfer, helping to prevent the accumulation of heat-induced deposits. It is common to monitor steam pressure as a method of estimating the degree to which the tubes have fouled. As the tubes foul, higher steam pressure is needed to compensate for the reduction in the overall heat transfer rate. Referring back to the equations discussed earlier, the LMTD must increase proportionally to the decrease in U caused by fouling. As an increase in steam pressure is identified, fouling is assumed, and the unit is taken out of service for cleaning. If fouling progresses too far it will either cause the tube to fail or it will become impractical to clean, resulting in costly repairs and loss of production. Although scheduled maintenance downtime also means lost production time, a cost-benefit analysis would strongly support building realistic maintenance downtime into the production schedule. Given the significant impact of fouling on productivity and production costs, proper control logic, which provides more insight on the degree of fouling, should be Figure 3. An installed 68 in. diameter graphite shell and tube heat employed. This will allow for scheduled shutdowns at appropriate intervals to avoid detrimental loss of heat exchanger remains in successful operation at a fertilizer plant. The higher tube wall temperature can increase fouling rates, change the nature of the fouling, and increase thermal stresses across the tube wall. Condensate build up in the shell is normally a result of poor condensate removal or the use of the incorrect trap. From a thermal performance perspective, the accumulation of condensate in the unit reduces the film coefficient for the portion of tube length subjected to the condensate by a factor of three to four times. Poor condensate removal not only has an effect on the heat transfer rate, but also creates a dangerous situation where severe water damage can occur, as live steam is fed into the unit. In this situation, there is a strong possibility of violent tube vibration during system start-up. Proper connection sizes and pipe arrangements are important to avoid conditions that will promote condensate entrainment. Additionally, a pumped steam trap should be employed to ensure proper removal. It is very important to avoid condensate buildup on the shell side of the unit at all times.
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transfer capacity and material failure, while allowing for easier cleaning. The control is simple and utilises data that is frequently gathered for the DCS. The control logic requires the use of a reliable flow meter on the steam inlet and outlet, magnetic flowmeters on the process inlet and outlet, and temperature and pressure sensors at the inlet and outlet of both shell and tube side streams. This collected data can be used to calculate the overall heat transfer rate, U, at a point in time based on the actual heat load, LMTD, and known surface area. The degree of fouling can then be determined by comparing the calculated U-value to the design U-value. A review of this information will allow the operator to see a trend and advise production of an upcoming need for maintenance shutdown. If the cleaning stage is planned and routine, rather than an unplanned shutdown, the net loss of production time will certainly be minimised. For graphite tubed evaporators, a fully graphitised tube is recommended since it is more resistant to thermal and mechanical shock, and fatigue failure, and typically offers longer operational life than carbon-bonded or resin-bonded graphite tubes. Although the fully graphitised tube uses the same basic raw materials as the carbon-bonded or resin bonded graphite tube, the significant difference is that after forming the tube, it is subjected to very high graphitising temperatures. This step eliminates amorphous carbon. The presence of carbon within the material composite will lower thermal conductivity and increase the coefficient of thermal expansion.
There has been some recent innovation in the design of graphite shell and tube heat exchangers, both in material and construction. A newer graphite composite tube, 68% graphite with PPS binder, has a lower roughness coefficient than a fully graphite tube. This property reduces the propensity to foul and allows for cleaning at much lower hydro blasting pressures, resulting in less tube breakage during the cleaning process. The unit construction utilises a self-contained elastomeric tube to tubesheet seal, that allows an individual tube to be easily removed and replaced if needed, while greatly reducing tensile and compressive loads on the tube. Although more in-process evaluation is required, early results indicate that this design shows great promise in reducing OPEX and downtime.
Conclusion
The optimisation of graphite evaporator efficiency and reliability is paramount in phosphoric acid production. By delving into fundamental heat transfer principles and emphasising critical factors that affect the overall thermal efficiency, a better understanding can be gained on how to maximise the heat transfer capacity of the evaporator. Better understanding of the effects of improper and poor operating practices, and the need to properly control the process, not only maximises heat transfer capacity but reduces downtime, decreases OPEX, and increases production rates. Implementing these best practices not only enhances efficiency and reliability, but also contributes to sustained productivity and cost-effectiveness in the long run.
Award-Winning Innovation for
Phosphoric Acid Evaporators Low Fouling • Corrosion Resistant • Less Downtime • Easy Maintenance
A New Start For Ammonia Sampling Matt Dixon, Swagelok Company, USA, explains how modern equipment in fertilizer production facilitates faster ammonia sampling, reduces costs, and ensures employee safety.
F
ertilizer production is critical to secure adequate food supplies, but the process itself is not easy. It uses anhydrous ammonia, which must have low water content, usually between 0.2 – 0.5% to avoid significant corrosion in system components and possibly tainted end products. Consistent testing ensures there is enough water in the system to avoid corrosion and maintain product quality (Figure 1).
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The necessity of such testing does not make the testing itself simple for some key reasons: n It is potentially hazardous. An operator must wear the proper personal protective equipment (PPE) since ammonia has the potential to cause significant harm to workers, including burns, eye irritation, and
potential death if inhaled. PPE includes goggles, gloves, respirators, and chemical suits. n It is delicate. Precision is essential in ammonia sampling and testing, and even a small procedural error can lead to inaccuracies that could put workers and product quality at risk. n It is time-consuming. The entire process of traditional ammonia testing can take up to eight hours, which can slow the production line and reduce overall production at a facility. Traditional testing methods not only reduce fertilizer plant efficiency, but also expose workers to higher risks of accidental exposure. Fortunately, more modern equipment exists that can streamline testing, improve accuracy, and promote efficiency during ammonia sampling and testing.
The traditional approach Figure 1. Consistent ammonia testing provides useful insights into potentially hazardous conditions that must be remediated immediately.
Figure 2. Putting a cap on the residue tube makes filling the tube much easier.
Figure 3. Having a touch screen operator interface with step-by-step instructions reduces the possibility of human error during sampling and testing procedures. 28 | WORLD FERTILIZER | MARCH 2024
Operators commonly perform traditional ammonia sampling using the CGA G-2.2 method, dispensing a 100 ml sample of liquid ammonia and allowing it to evaporate. What is left after evaporation is water, which is then measured to determine whether its presence in the ammonia was within the 0.2% – 0.5% range. If so, operations can continue normally. If not, operators must adjust the water content immediately to avoid potential dangers to workers and the environment. Ammonia with water levels below 0.2% could damage other equipment in the plant like storage tanks or other fluid system components through which the ammonia flows. Ammonia stress corrosion cracking, the most common type of damage, can lead to the destruction of components as alloys weaken under the strain and fail unexpectedly. Conversely, having water content above the 0.5% threshold is generally unnecessary. While testing accuracy is essential, traditional methods may not always produce accurate results. The variables that can affect the testing accuracy include the following: n As cold ammonia fills warm glass containers, it immediately begins to boil and evaporate, making it difficult to fill residue tubes to the graduation line. n Inconsistent rates of heating can lead to inconsistency in sample results.
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n
Inadequate flushing of residual water and old samples from the transport line can lead to samples that are not representative.
different functions. In addition, some systems may feature an easy touchscreen interface to control heater operations.
Traditional ammonia sampling and testing also takes significant time to do properly. Accuracy is crucial as the task of filling a warm residue tube precisely as the ammonia evaporates is a complex procedure. Since traditional testing can take up to eight hours, it costs facilities time and money, which affects profitability in an increasingly competitive market. The most important aspect, considering anhydrous ammonia’s highly toxic nature, is to keep employees safe. Accidental exposure may lead to prompt irritation of the eyes, nasal passages, throat, and respiratory system, potentially causing blindness, lung impairment, or fatality. Breathing in lesser amounts may induce coughing, as well as irritation of the nose and throat. Additionally, ammonia escaping into the air poses environmental hazards that could lead to enforcement actions from regulatory agencies. It is key to always use the right PPE when ammonia sampling and testing occurs and remind employees to avoid spilling ammonia into the environment.
Finding a supplier who can be a guide through the acquisition of these grab sampling systems is key. They can help identify which features are critical to specific applications and which are not. Reliable suppliers may also offer design advice, so the system is properly constructed to avoid unnecessary worker exposure. It is important to make the system as intuitive as possible for the operator, while automating as much of the sampling process as possible to reduce possible human error. Finally, grab sampling systems reduce sampling time, keeping the fluid system working throughout the process. Modernising ammonia sampling systems allows the process to be streamlined for operators and keep employees safe, allowing for focus on what is best: making fertilizer that keeps the food production industry in business.
The updated ammonia sampling process
Many fertilizer plants are transitioning to pre-engineered grab sampling systems, designed specifically for ammonia sampling. These systems enhance safety, sample quality, and overall efficiency. It is important to find systems specifically designed for ammonia sampling, so operators are not exposed to either liquid or vaporised ammonia unnecessarily. Pre-engineered grab sampling systems also improve consistency and turn sampling and testing around much more quickly. To find the right system for fertilizer facilities, it is important to consider the following features: n Closed-sample fixtures: such fixtures can help improve safety by limiting operator exposure and environmental impact. A closed-sample design reduces the need for significant amounts of PPE. Closed fixtures may also be made of glass, allowing the operator to monitor conditions inside the system. n Effective chilling mechanisms: because ammonia boils off quite easily and can threaten fill accuracy, a sampling system designed with effective chilling mechanisms can help minimise the potential for excessive boiling. n Semiautomated sample dispensing: a cap assembly can be fitted to the residue tube to assist with the filling process (Figure 2). When dispensing the sample, ammonia fills the residue tube until the level reaches the bottom of the overflow tube. This feature helps ensure consistent sample sizes during each use. n User-friendly operation: sampling systems that enable clear and simplified operation can help prevent errors and improve the user experience (Figure 3). For example, a geared mechanism may enable the operator to easily choose between 30 | WORLD FERTILIZER | MARCH 2024
Building an ideal ammonia sampler
When specifying an ammonia sampling system for a fertilizer plant, there are several considerations that are helpful to keep in mind: n The ideal ammonia sampler should put employee safety at the top of its list of advantages. Using glass fixtures to hold the sample would allow operators to confirm the process is taking place without unnecessary exposure to the ammonia. The closed fixtures would also keep ammonia from leaking into the environment. n Ideal samplers could be installed directly at the sample point, which eliminates the need to transport hazardous materials throughout the plant. n There should be documentation that the sampler will not leak and is rated for use in hazardous areas. n The sampler should reduce the reliance on the skills and judgement of the operator by semiautomating the process. n Suppliers should be able to demonstrate that their equipment delivers consistent results. For example, a sampler with single-handle valve operation and pre-chilled residue tubes would help operators avoid sampling errors. n The sampler should also have a filling cold bath feature, which removes older ammonia from the transport line to prevent inaccurate samples from being collected. n A touchscreen user interface and step-by-step operating instructions will enable operators to easily see how to make the sampling and testing process as seamless as possible. Materials matter, so particularly in today’s business environment, suppliers should provide raw material traceability throughout their supply chain to make sure the systems received are what has been ordered.
Faster results, faster reactions
Finally, the ideal ammonia sampler should take less time to produce results. Quicker results mean faster reactions if something in the system is off. This can save companies time because they can fix problems before they become major repairs.
NEW POSSIBILITIES Tim Haugen, Quest Integrity, USA, outlines the benefits of ultrasonic-based smart pigging inspections and cleaning on steam reformer convection coils in the ammonia, methanol and hydrogen industries.
U
ltrasonic-based smart pig inspections have become a mainstay for maintaining fired heater and furnace tube integrity. However, many steam reformer owner-operators across the ammonia, methanol and hydrogen industries are unfamiliar with the technology or are not aware it can be utilised for the inspection of convection sections including coil configurations connected to common headers (manifolds). 31
Although it is a widely accepted practice to inspect the radiant tubes in steam reformers, inspection plans or any other means to help determine the condition of convection coils are almost non-existent. As such, little to no inspection data has been collected on these coils. This is due to the lack of an entry point into the convection box, accessibility to the inside of tubes connected to common headers, space restrictions, and the challenges associated with conducting external inspections on tubes with raised surfaces (e.g., fins and studs). When considering all these accessibility issues, internal and external inspection technologies such as smart pigs, external crawlers and handheld UT solutions,
cannot be utilised without major modifications to the furnace or sacrifices in the amount and quality of inspection data readings. As a result, many convection sections are not inspected and are instead maintained using conservative lifecycle predictions based on tube age, operating conditions, tube metallurgy and feedstock quality. Although steam reformer convection sections typically operate in less harsh environments (e.g., lower temperatures, and less corrosive feedstocks) as compared to some other fired furnaces and heaters, tube failures do occur from wall loss and creep growth. To mitigate possible future tube failures and obtain much needed integrity data, a methanol plant located in the Middle East performed an automated in-line 'smart pigging' inspection and fitness-for-service screening assessment on 100 natural gas preheater coils (Figures 1 and 2). The coils had never been cleaned before and some internal fouling was suspected given the number of years in operation. As such, the solution provider selected to perform the inspection and assessment was also asked to clean the coils using an advanced mechanical cleaning and pumping technology in addition to pumping the smart pigging inspection tool through the coils.
Project services and execution Figure 1. Natural gas preheater section.
Figure 2. Smart pigging inspection tool.
Figure 3. HDS inside a common header. 32 | WORLD FERTILIZER | MARCH 2024
Quest Integrity was chosen as the solution provider to carry out all three of the services for this project. The cleaning service selected used pumping trucks and mechanical cleaning pigs to effectively remove internal fouling from tube walls, restoring proper heat transfer and thermal efficiencies. For the inspection, a high-resolution ultrasonic in-line inspection technology was utilised. This detects and measures damage such as internal and external corrosion, erosion, pitting and fretting as well as deformations such as bulging, swelling, denting and ovality in numerous coil configurations. The technique provides owner-operators with a comprehensive and quantitative mapping of a coil’s wall thickness and geometry. The inspection data from this service can then be used along with heater design and operating parameters to conduct a fitness-for-service screening assessment following the API 579-1 Standard. The assessment provides owner-operators with the confidence that a furnace can be returned to service and safely and reliably operated until the next planned shutdown. As with many steam reformers, common headers were attached to the inlet and outlet of each coil. This added to the complexity of the project, since the cleaning pigs and inspection tools would need to travel through the header first for entry into the coils. Cutting 200 tubes welded to the inlet and outlet headers (or even a portion of the total tubes) and installing temporary flanges and launcher barrels was not an option given the time and cost associated with such modifications. To overcome these hurdles, a header delivery system was installed inside the inlet and outlet common headers and attached to each coil. The delivery system effectively connected the coils via hoses to the water pumps installed on the cleaning truck (Figures 3 and 4). This created a closed loop system, allowing water to enter
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the coils while keeping the headers dry. The water inside the coils provided a couplant for the ultrasonic inspection, while also propelling cleaning pigs and the inspection tool through the coil via the cleaning truck pumps. Significant internal fouling was encountered during the cleaning process, which was not expected, with some coils completely blocked. The solution provider managed to clean all of the unblocked coils and assist the plant in unblocking a portion of the remaining coils. Removing the fouling greatly improved thermal efficiency and heat transfer and allowed for the highest quality ultrasonic inspection. The inspection was performed successfully, and a comprehensive high-resolution ultrasonic data set was collected. All of the on-site work was completed within the expected timeframe and without disrupting or delaying the turnaround schedule.
Figure 4. Set up for coil cleaning and inspection (typical process heater).
Inspection and assessment results
The high-resolution inspection revealed internal and external localised wall loss upwards of 40% in numerous pipes (Figure 5). General internal wall loss up to 26% was also present in the 180° return bends. The result of the engineering screening assessment showed that the coils were fit for service for the next four-year operating period. A remaining life assessment was also performed on each coil as part of the screening assessment, showing an estimated remaining life of 15 years with a recommendation to re-inspect in four years to monitor corrosion rates and detect any other localised damage that may affect coil integrity.
Fertilizer plants
The same techniques discussed in the case study have been successfully applied on steam reformer coils located in fertilizer plants. For one plant, smart pigging inspections on flue gas cooler coils are conducted on an almost annual basis to monitor and troubleshoot localised areas of internal wall loss experiencing high rates of corrosion. This is in response to a tube failure several years ago. The root cause of the corrosion damage from metallurgical testing was departure from nucleate boiling caused by intermittent loss or reduced water flow. Periodic inspection monitoring will most likely occur for the foreseeable future in order to validate or confirm the effectiveness of the corrective actions. In another instance, unexpected internal wall loss was found on the inside radius of 1D return bends in a feed gas coil (Figure 6). Although the straight pipes were in good condition with minimal wall loss, moderate thinning upwards of 32% wall loss was found in the return bends. This discovery prompted an investigation and root cause analysis.
Conclusion
Figure 5. Tube thickness plot showing localised wall loss.
Figure 6. 2D thickness plot showing localised wall loss in return bend. 34 | WORLD FERTILIZER | MARCH 2024
Periodic in-line inspection and mechanical cleaning are a sensible strategy for managing the long-term reliability and performance of steam reformer convection sections. The benefits realised by performing an advanced mechanical cleaning and smart pigging inspection are numerous. Utilising custom engineered header delivery systems on assets that were previously deemed as un-inspectable with smart pigging technology opens up the opportunity for a cleaning and a comprehensive assessment of the coils’ conditions. As seen in the first case study, the advanced mechanical cleaning of the natural gas preheater coils revealed significant fouling and flow restrictions that were previously unknown. As a result of the cleaning, the heat transfer efficiency increased over 60% and the product rate increased significantly as well, enabling the plant to produce an additional US$1 million of methanol a year. The smart pigging inspection technology provided valuable insights on the actual condition of the coils, and the fitness-for-service screening assessment provided assurances that the coils could be safely operated for the next operating period. The three services, combined with a purpose-built header delivery system, provides plants with a highly effective approach to optimising the performance and reliability of its steam reformer, minimising downtime and maximising production and profitability.
Corrosion Damage Control On Urea Equipment Daniel J. Benac, Dorothy Shaffer, and Johan Thoelen, BakerRisk, USA and Belgium, discuss the dangers of carbamate corrosion damage and the different mitigation methodologies available for urea equipment.
U
rea plant equipment operates at elevated temperatures and is exposed to corrosive environments that can potentially limit its life. Awareness of the corrosion-related mechanisms that can damage the equipment used in urea plants is essential in developing an appropriate solution for proper equipment inspection, damage mitigation, and failure prevention. The pertinent damage mechanisms can also provide input for fitness-for-service evaluations, as the specific mechanism and the rate of attack need to be understood in order to determine the remaining life expectancy of the equipment. For a proper risk-based inspection (RBI) programme or hazards analysis to be conducted, the appropriate 35
damage mechanisms must be identified so that the probability of failure can be determined in addressing reliability issues. 1,2,3 This article provides examples and discussion regarding the carbamate corrosion damage mechanisms related to urea process parameters, materials of construction and process equipment, and inspection methods and characterisation techniques to identify each form of damage. Additionally, useful tips for considering potential mitigation methods are provided.
Figure 1. Failure of a urea reactor and release of the vessel head.
The urea process
To begin the urea production process, feeds are mixed either before or within the reactor where urea is formed. The CO2 and NH3 are individually brought to a high pressure and are combined. The feeds then quickly react and generate carbamate and a large amount of heat.
CO2 + 2NH3 → NH2COONH4 Feeds
Carbamate Intermediate
For most processes, a small amount of oxygen, usually in the form of air, is added to the CO2 feed for material passivation. A significant excess of NH3 is used to ensure near complete conversion of the CO2 in the temperature range of 135°C – 200°C (275°F – 392°F), for example in a 3.6:1 ratio. The ratio can vary from four for older designs to three for more modern designs. Higher ratios tend to be less aggressive. Excess ammonia also assists in the conversion of carbamate into urea. The carbamate dehydrates (i.e., sheds a water molecule) to slowly form urea while it absorbs a small amount of the heat in the process. High pressure is required to keep the reactants in solution, as it mitigates decomposition of carbamate back to its components and increases yield. The high-pressure reaction section can range from 126 – 562 kg/cm2g (1800 – 8000 psig). The slow reaction time for the urea formation reaction requires a large reactor volume to increase the yield, which does not go to completion.
NH2COONH4 → NH2COONH2 + H2O The effluent from reactors will be a mixture of urea, carbamate, ammonia, and water. It can also include a lesser amount of ammonium carbonates – (NH4)2CO3.
Urea equipment materials of construction
Figure 2. Crevice corrosion attack on a 25-22-22 high pressure stripper gasket surface.
Figure 3. Rupture of a deadleg in a carbamate line. 36 | WORLD FERTILIZER | MARCH 2024
In an ideal world, the materials chosen for urea equipment would be impervious to deterioration effects from process conditions. In the real world, however, this is either impossible or cost prohibitive, so various types of equipment damage continue to occur. Most process equipment used in urea production is comprised of pressure vessels, piping, and storage tanks whose pressure boundaries are constructed from metallic materials. All materials of construction used in the urea industry are susceptible to degradation and various types of damage mechanisms.4,5 The carbamate intermediate is similar to a strong acid in its impact on materials and requires specialised metals to mitigate damage. Due to the harsh corrosion environments, stainless steels and specialty stainless steels are the most commonly used materials of construction for process equipment in the urea industry. These materials offer a suitable combination of strength and ductility and are capable of safely operating in the temperature ranges employed in the urea industry. Through the years, urea development work with austenitic and duplex stainless steels has improved the resistance to carbamate corrosion, along with the use of special materials such as zirconium. Additionally, to control costs on the thick walls of pressure shells, cladding is typically used. Zirconium and titanium are materials that react strongly with oxygen to form a corrosion protection layer, so they do not need the assistance of passivation air. They are also
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resistant to chloride SCC. However, titanium is relatively soft and is currently reserved for special situations; both of these specialty metals are expensive.
Typical materials of construction Carbon steels are used in feed supplies and utilities but not in direct contact with carbamate, because of the extremely high carbamate corrosion rates. Often on vessels and multi-layered vessels, a corrosion protective liner is used over a carbon steel pressure boundary with high tensile steels, at times used in monowall high pressure equipment. This is often effective unless a situation develops where the liner is breached, and the carbon steel is exposed to corrosive conditions. Figure 1 shows a urea reactor that failed in 1992. It was determined that the weep holes had plugged and the corrosive attack of the multi-layer was unknown. After the stainless steel corroded through, urea entered and attacked the carbon steel layers. The 14 layers were compromised and could not withstand the pressure.6,7 Therefore, it is important that the weep holes are monitored, and a leak detection system is in place in case the liner fails. Carbamate corrosion materials start with 316L up to the more carbamate tolerant 316L urea grade UG, X2CrNiMo25-22-2, zirconium, titanium, and more specialised urea specific materials (Uremium 29, Safurex™, and others).5
Figure 4. Carbamate condensate corrosion in type 316
UG plates.
Figure 5. Carbamate corrosion failure of a high-pressure scrubber. 38 | WORLD FERTILIZER | MARCH 2024
Materials for urea production vary from those suitable for non-corrosive and utility services to those exposed to the rigors of the highly corrosive synthesis section. Materials include 316L to 316L urea grade UG, X2CrNiMo25-22-2, zirconium, titanium, and more specialised urea specific materials (Uremium 29, Safurex™, and others).8 Type 316L-urea grade, or 316L modified (MOD), is the historical urea workhorse material with improved corrosion resistance. It is suitable for many areas, including most carbamate equipment in conventional plants. The low carbon content, combined with a well-balanced chemistry (low silicon and nickel content close to 14%) makes the alloy fully austenitic, and free of intermetallic phase precipitations. The ferrite level is kept under 0.5% in the solution annealing and water quenched conditions. Some designations include 1.4435, X2CrNi Mo18-14-3, 1.4404, and BC.01. According to one supplier, the alloy typically has low carbon (<0.03% C), 18% Cr, ~14% Ni, and 2.5% min Mo, with Si <0.5% and Mn between 1 – 2%. Stainless materials typically require a passivation step upon startup to secure a corrosion resistant chromium-oxide layer. If the oxide layer is maintained by oxygen feed, the stainless steel corrodes passively at low rates. Passive corrosion rates of 316L-UG are typically between 0.01 – 0.15 mm/y (0.4 – 4 mpy (mils per year)) on stream. If the passive layer is damaged (by erosion/corrosion, by surface contamination, or lack of oxygen to passivate the surface) active corrosion will set in and can reach values of 100 mm/y (300 mpy). Active corrosion cannot be reversed online once started; once detected, the plant must be shut down and passivated. The development of the austenitic 25-22-2 opened the doors for more severe but typically more efficient service conditions. This material is a higher-alloyed austenitic stainless steel and is designed to provide better corrosion resistance to the stripper conditions than 316L-UG stainless steel. Likewise, under less severe service conditions, 25-22-2 shows better corrosion performance and less susceptibility to some of the typical damage mechanisms than standard 316L-UG.9 However, Figure 2 shows that crevice corrosion can occur at a gasket surface. Other urea specific materials considered are SafurexTM 29Cr7Ni2MoN (UNS S32906) developed by Sandvik and preferred by Stamicarbon licensors, and DP28W (28Cr8Ni1Mo2W) UNS32280810 paper preferred by Toyo. Other alloys such as Uremium 29 (29Cr7Ni1MoN) UNS32906 are being utilised. Toyo Engineering Corporation (TEC) and Sumitomo Metal Ind., Ltd. (SMI) have jointly developed new duplex stainless steel DP28WTM for urea plants. While these alloys are resistant to carbamate corrosion and need minimal passivation, improper welding or handling can still introduce areas vulnerable to attack, and damage mechanisms other than carbamate corrosion can apply, such as flow-assisted corrosion. The biggest advantage of duplex stainless steel is its excellent passivation property in urea-carbamate solution, which enhances the reliability of the equipment and enables a reduction in the injection of passivation air. However, duplex stainless steel has some weakness in corrosion resistance in the heat affected zone (HAZ), which shows up in long-term operation. Although nickel-based alloys are resistant to many corrosives in alkaline solutions, when subjected to oxidising environments, nickel-based alloys are not suitable because of the formation in ammonia solutions of soluble Ni (NH3)6 which can result in
accelerated corrosion. For example, the corrosion rate of one high nickel-based alloy (nearly 60%) in carbamate solutions has shown to be 86 mpy.
n EA: activation energy. n T: temperature. n R: universal gas constant ( = 8.314 J/mol-K).
Carbamate corrosion
In older plants with a reactor, this is followed by a pressure letdown valve; the most severe corrosion conditions are in the reactor and valve. The drop in pressure helps in decomposing the carbamate and lowers the temperature in the medium pressure section of the plant. In more modern plants, energy is saved by decomposing the carbamate, condensing it, and recycling to the reactors, all in the high-pressure section but at higher temperatures that have led to more resistant alloys. The high acidity can result in general wall thinning of carbon steel. For example, carbamate on carbon steel can have corrosion rates of more than 1000 mm/yr. In the urea synthesis section, points at which stronger carbamate concentrations can occur include mixers for ammonia and carbon dioxide. In the urea reactor, in recycle solutions, in the HP stripper/decomposer feeds, and in carbamate condensers.10 Figure 3 shows that deadlegs can be particularly susceptible to accelerated attack, creating a risk for rupture of equipment. Some of the ways carbamate corrosion can occur are described in this article. Higher flow rates and velocities can remove protective passivation layers which will accelerate corrosion and result in flow-assisted attack (erosion corrosion) and carbamate corrosion. Even on more resistant materials, crosscut corrosion can occur where the tubes or bar stock are cut across the grain. In extruded materials, the variability of the microstructure can allow for attack on the elongated grain boundaries deep into the metal, creating
A damage mechanism unique to urea plants is carbamate corrosion. Carbamate (short for ammonium carbamate) is produced in the urea process by a reaction of ammonia and carbon dioxide at high pressures. A carbamate is a category of organic compounds that is formally derived from carbamic acid (NH2COOH) with highly aggressive corrosive properties for susceptible materials. Carbamate is an ammoniated form of carbamic acid with aggressively acidic corrosion properties that can result in general wall thinning of carbon steel and stainless-steel alloys, as well as other damage characteristics. Carbamate on carbon steel can have corrosion rates of more than 1000 mm/y. Higher temperatures and higher carbamate concentration increase the corrosion rates: the Arrhenius equation predicts that the corrosion rate doubles for every 10°C (18°F) increase in temperature. Higher tempertaures and a low activation energy result in accelerated corrosion rates. Process licensors, company experience, or industry recommendations may set process limits to avoid aggressive carbamate corrosion conditions for the design materials. The Arrehenius equation is:
K = A exp (-EA/RT) Where: n K : rate constant. n A: pre-exponential factor.
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rough surfaces and tube end pitting (which interferes with tube plugging). Materials in special services (such as tight shutoff valves) benefit from ‘isotropic’ fine grain boundaries which are consistent regardless of the face or cut. SafurexTM HIP is the tradename for a specialty material that is designed for resistance to crosscut corrosion.3 Where carbamate condenses in the vapour space due to cold spots, carbamate condensate corrosion (also known as carbamate condensation corrosion), will occur, as this process interferes with normal passivation and has higher corrosion rates. Figure 4 and Figure 5 show an example of carbamate condensate corrosion. In highly stressed regions with a carbamate solution condensing out a vapour phase, strain (or stress) induced intergranular racking (SIIC) may occur.11
For prevention of flow-assisted attack
Key carbamate corrosion parameters
Aggressive corrosion-related damage mechanisms are present in urea producing equipment. Understanding these damage mechanisms and how operations or process conditions can affect equipment will help mitigate the occurrence of these damage mechanisms. Selecting the proper material and implementing the mitigation options mentioned in this article can help reduce the effects of carbamate corrosion.
n Lack of oxygen – reduces formation of passive film. n Presence of carbamate. n High flow rates and velocities potentially remove protective films. n High acidity – causes general wall thinning. n Crevice formation, concentrates in cells with oxygen depletion. n High stresses (strains) will promote stress corrosion cracking. n Increased temperature increases corrosion. n Iron or copper contamination. n Excessive ferrite in alloy or welds. n Cut ends.
Equipment concerns Vapour areas in the high and medium pressure sections of the urea plant are at a risk of carbamate condensate corrosion: n Vapour pipelines or piping or high spots that can trap vapours where steam tracing is inadequate or not in service. n Areas where insulation is inadequate or may be damaged. n Locations where attachments act as a heat sink such as lifting lugs, thermowells in vapour areas, or large flanges, for example at the top of the reactor. n Most of the urea feed and high and medium process equipment, particularly where passivation is not maintained. n Stripper exchanger tubes and ferrules. n Decomposers. n Condenser exchangers. n Drain lines.
Mitigation options
n Maintain oxygen levels for passivation: to maintain stainless steels in a passive state, it is necessary and recommended to add oxygen to the process (usually 0.4 - 0.6 volume percentage) in the CO2 feed. n Use higher-alloyed austenitic or duplex stainless steel (such as 25-22-2) or more resistant materials designed to provide better corrosion resistance to the stripper conditions than historical 316L-UG stainless steel. Zirconium bonded tubes are used in certain designs, but the material is expensive. n To minimise corrosion after repairs, it is recommended to select an electrode that will control the weldment to contain ferrite contents under 3%, even as low as <0.6 % ferrite. Special electrodes for welding 316L UG for urea service are available.12 n Evaluation of contaminants: online monitoring of nickel. 40 | WORLD FERTILIZER | MARCH 2024
n Reduce velocity by changing the design – use multiple restriction orifices, increase the pipe diameter, or reduce the flow rate. n Ensure control valves are properly designed where flashing conditions may create problems. n Where possible, improve the design to avoid turbulent flow (for instance, consider flow in baffles and impingement plates in heat exchangers). n Change to a more resistant material with increased hardness or one that is alloyed with increased corrosion resistance. Add hard facings on surfaces such as those used in valves and pumps.
Conclusion
Acknowledgements
A portion of this paper was presented at 67th 2023 AICHE Ammonia and Related Facilities Safety Symposium.11 The shared information from the 2021 Ammonia and Fertilizer Joint Industry Program (JIP) facilitated by BakerRisk has contributed to the content of this paper.13
References 1.
BENAC, D. .J. , SHAFFER, D. , “Damage Mechanism Assessment and Methodology for Ammonia Equipment, Vessels, and Piping,” 64th AIChE, Safety in Ammonia Plants & Related Facilities Symposium, 2019, Vol. 60, pp 165-176. 2. BAKER, J. BENAC, D. .J, and SHAFFER, D., “Ammonia and Fertilizer Industry Joint Industry Program – A Resource to Manage Damage Mechanisms and Mitigation Options,” World Fertilizer, 2020. 3. NUGENT, M., BENAC, D. .J, BERG, S., “Systematic Approach Towards Damage Mechanism Reviews and Mechanical Integrity Improvements for Ammonia Synthesis and Fertilizer Facilities,” 2023 AMPP Annual Conference Paper No. 19349. 4. CONNOCK, L., “Corrosion Control in Urea plants,” Nitrogen, Issue 223, BCInsight LTD, September 1996. 5. SUKUMARAN NAIR, MP., “Control Corrosion Factors in Ammonia and Urea Plants,” Hydrocarbon Processing, January 2001. 6. Occupational Safety and Health Review Commission Docket 93-0628, 2004, last accessed on April 28, 2014, URL: http://www.oshrc.gov/ decisions/html_2004/93-0628.html. 7. EIJENKENBOOM J, BROWER M, “A Blocked Leak Detection System,” 2021 UreaKnowHow resource. 8. TERSMEDEN K, “Successful Use of Stainless Steels in Nitrogen-Based Fertilizer Plants,” 1996 AICHE Ammonia and Related Facilities Safety Symposium 9. GULLBERG, D., EIDHAGEN, J., MATTSON, R., , “New Duplex Stainless Steel Optimized for the Urea Process,” NACE International, Corrosion 2018, 15-19. 10. NAGASHIMA E, IDEGUCHI Y, KITA Y, YAMADERA, Y., “New Duplex Stainless Steel DP28W Contributes to Safe and Reliable Operation of Urea Plant,” 2004 AICHE Ammonia and Related Facilities Safety Symposium. 11. BENAC, D. .J. , SHAFFER, D. THOELEN, J., “Corrosion Damage Mechanism Review and Mitigation Methodology for Urea Equipment,” 2023 AICHE Ammonia and Related Facilities Safety Symposium. 12. M.F. DE ROMERO, J.P. GALBAN, “Corrosion and Repairs of Ammonium Carbamate Decomposers,” Materials Performance, Vol. 35, May 1996. 13. 2021-2022 Ammonia & Fertilizer JIP Baker-Risk Project No. 01-07250-003-20, “Identification of Damage Mechanisms and Mitigation Options for the Urea Process,” October 14, 2022.
Julie Holmquist, Cortec, USA, explains how vapour phase corrosion inhibitor technology can help mitigate corrosion damage in fertilizer plants.
TAkING ACTION B
oilers, storage tanks, and insulated piping are familiar sights at fertilizer plants, and corrosion is their all-too-common enemy. Often, replacement of parts due to corrosion damage is a routine activity. While this is better than a full-scale emergency shutdown, preventing corrosion can make some of those repairs and replacements fewer and farther between. In contrast to many standard methods of protection that can be cumbersome or inadequate, vapour phase corrosion inhibitor technology changes the face of corrosion prevention by simplifying efforts in corrosion control.
A glimpse of corrosion costs in the fertilizer industry Before examining the workings and potential applications of vapour-phase technology, it is helpful to get a perspective on
some of the industry’s corrosion costs and issues. A 2004 study of a fertilizer factory in India offers numerous examples. The review found that more than half of direct corrosion costs were attributed to equipment replacement, while 23% went towards maintenance painting, 15% to maintenance and repairs, and 10% to structural corrosion. Looking at sulfuric acid plant expenditures (all numbers rounded to the nearest hundred), researchers found it was common to regularly replace steam coils (US$65 200) and do patch welding on the boiler shell due to corrosion (US$3800). The acid drying tower, intermediate absorption tower, and final absorption tower tubes had to be replaced annually (US$9800). Patch repairs had to be done every year on an acid storage tank (US$6000), and in-plant pipelines had to be replaced once every three years (US$7600).1 Together, these costs easily add up to almost US$100 000, even though they do not represent every direct and indirect 41
corrosion problem that did or could occur. Many other corrosion variables exist that could drive up costs by, for example, causing unexpected equipment failures and outages that lead to dramatic monetary losses from suspended production. Robust inflation over the last two decades would make those losses significantly higher today. Targeted corrosion prevention campaigns on key assets could therefore significantly reduce costs while also making life easier for maintenance personnel because of fewer corrosion-related repairs. While not applicable to every possible corrosion concern, vapour phase corrosion inhibitor technology offers inherent advantages for several key areas that are otherwise difficult to protect.
Vapour phase corrosion inhibitor technology
Vapour phase corrosion inhibitors (VpCI®/VCI) are chemical compounds that have an affinity to metal and an aversion to moisture. These inhibitors can be applied in many forms, both as solids (e.g. powder) and liquids (e.g. fogging fluid). The chemicals volatilise or vaporise, diffusing until they reach a state of equilibrium in an enclosed space. As these molecules disperse, they are attracted to metal surfaces where they adsorb and create a molecular layer that protects the metal from direct interaction with moisture and other corrosives. Under normal conditions, a
corrosion cell would form in the presence of metal, oxygen, and an electrolyte; however, a VCI layer creates a barrier to this interaction, interrupting the typical electrochemical cycle that leads to rust and corrosion. Since VCIs can work in both the vapour phase and the liquid phase, they can be used to protect both empty void spaces and areas that are wet or filled with water (e.g. above and below the water level in a boiler). Unlike some technologies (e.g. nitrogen blanketing), VCIs do not require a constant airtight seal to be effective. While the space being protected should remain closed as much as possible to keep the VCIs from escaping, an adequate dose of VCIs will allow the molecular protective layer to replenish itself after the area is briefly opened and reclosed. These characteristics make VCI ideal for protecting hard-to-reach surfaces inside boilers, under storage tanks, and under insulation.
Steam boiler layup
Steam boilers are among the core drivers of fertilizer plant production processes because they create steam to heat chemicals and stimulate reactions. These multi-story boilers may need to be shut down periodically for inspection or maintenance. While suspended operation may be ok during scheduled plant turnaround, it is unacceptable when a boiler unexpectedly malfunctions and upsets the productivity of the whole plant. Having a backup boiler for redundancy is therefore ideal, since production will stop otherwise. In either case, it is important that the offline boilers remain rust-free so they can start up on short notice without any corrosion-related complications. Shutdown and layup are sensitive times for boilers because the normal chemical water treatment programme is no longer in circulation. Furthermore, any residual moisture in a drained boiler makes a prime corrosion starting point. Boilers in wet layup, while sometimes protected below the water level, must battle moisture and condensation at the top of the boiler where the treated water cannot reach. Resulting corrosion products can clog the system, and, worse, lead to leakage and premature failures and repairs as the boiler tubes and walls experience thinning or pitting, ultimately shortening the service life of these high-dollar assets. Common methods of corrosion protection include nitrogen blanketing for drained boilers and high pH and sulfite treatment for boilers in wet layup. The former is intended to ensure the absence of all oxygen inside the boiler, but nitrogen purge is expensive and must be redone if pressure is lost. The latter requires frequent monitoring to maintain the proper balance of chemicals; otherwise, protection is null. Furthermore, these wet layup chemicals do not protect in the vapour-phase. Figure 1. VCI conceptual illustration shows how VCI An easier, more cost effective, and more reliable method of molecules (represented by yellow dots) diffuse throughout an dry layup is to apply vapour phase corrosion inhibitors when enclosed space and form a protective molecular layer on the boilers are shut down and drained for a turnaround, a process that surface of the metal. Image courtesy of Cortec. may last a few days or many weeks. A VCI fogging fluid is ideal for boilers larger than 10 000 gal. (38 000 l). The vapour-phase action allows the corrosion inhibitors to travel part way through the void space on their own inertia. To complete the application, a fan can be placed at the opposite end of the system to create an air current that pulls the inhibitors through the rest of the void. These VCIs typically do not need to be removed before refilling and starting the boiler. For wet layup, a VCI liquid can be added to the Figure 2. A schematic showing how a VCI CUI inhibitor can be injected feedwater and pumped through the system. The main into insulated piping at regular intervals for protection of the metal surface below the insulation. Image courtesy of Cortec. advantages of this method over sulfites or high pH 42 | WORLD FERTILIZER | MARCH 2024
levels are that much less monitoring is required and the VCIs protect the vulnerable areas of the boiler above the water level, as well as those in direct contact with it. If the boiler needs to be kept on low fire for standby, a VCI water treatment that remains effective up to 302°F (150°C) can be used. This way, the water does not have to be completely reheated before the boiler can be restarted, saving time when unexpected emergencies arise. VCIs are compatible with most water treatment chemicals and typically do not need to be flushed before returning the system to service.
AST bottom protection
Aboveground storage tanks (ASTs) are another common sight at fertilizer plants. With ASTs in general, a natural disadvantage for maintenance and inspection is the inability to see what is going on underneath the tank, i.e., if corrosion is occurring. Moreover, the tank bottom can be a natural place to trap moisture, and, in some regions, high chloride conditions in the air and soil make the environment extra corrosive. It is also difficult to conduct tank bottom repairs once a tank is in service because the tank must be drained and, even then, the area underneath the tank is relatively inaccessible. Historically, AST bottoms have been protected using cathodic protection (CP) systems, which usually require a continuous supply of power. However, sometimes the power is turned off or the tank needs to be retrofitted. Another problem is that tank bottoms can be uneven and may not be in full contact with the sand pad carrying the CP current, leaving patches of the floor that are unprotected.
VCIs provide an excellent supplement to CP. They can be injected underneath the tank as a powder or a slurry whether or not the tank is in service and filled. This eliminates costly bills to empty and raise the tank. Furthermore, the vapour-phase action allows corrosion inhibitors to diffuse into hard-to-reach pockets that may go unprotected by CP. After many years of field trial, the use of VCIs under ASTs has become an industry standard. This is evidenced by its prominence in two recent documents: API Technical Report 655, 'Volatile Corrosion Inhibitors for Storage Tanks,' released in 2021, and AMPP SP21474-2023, 'External Corrosion Control of On-Grade Carbon Steel Storage Tank Bottoms,' 2 3 released in 2023 with a section on VCIs. As time goes on and more long-term data unfolds, this method is only expected to become more established due to its practicality and effectiveness.
Corrosion under insulation (CUI)
One of the most recent advancements in applied VCI technology targets CUI prevention. CUI is insidious because insulation not only traps moisture to breed corrosion but also hides corrosion once it starts beneath the insulation. The seriousness of the damage or danger ranges from minor to life threatening depending on what the vessels or piping contain and how far corrosion progresses. According to a review in the oil and gas industry, CUI is blamed for approximately 40 – 60% of piping maintenance costs.4 If costs are this high in the petroleum sector, it would not be surprising to find similar results in fertilizer production, a related chemical industry.
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In addition to being difficult to detect, CUI is hard to counteract. While coatings and inhibitors exist that may slow the inception and propagation of CUI, they usually need to be applied at the same time as the insulation. This makes it difficult to mitigate corrosion on pipe, tank, and equipment surfaces that are already covered with insulation. Removal and replacement of insulation is neither practical nor cost-effective unless the risk is serious enough to warrant such an operation. Cortec has considered the CUI problem for many years and found VCIs to be a promising technology for protection of surfaces that are already insulated. Conceptually, the vapour-phase action of VCIs allows them to be injected into insulated material, enabling them to travel through the insulation or along the interface where the metal and insulation meet, leaving behind a protective molecular layer. The obstacle is the high temperature cycling on some piping and equipment that is difficult for most organic VCI chemistries to survive. Cortec therefore set out to find an injectable VCI formulation that could withstand relatively higher temperatures than the company’s first iteration. The result was an injectable VCI with temperature stability above 600°F (316°C), nearly twice as high as the previous injectable corrosion inhibitor. The inhibitor was laboratory tested for its ability to migrate through vapour space and form a protective, corrosion inhibiting film on a metal surface. In addition to showing migration and corrosion inhibition, the chemistry exhibited extremely hydrophobic properties, which, although not the chief mechanism for corrosion protection, are definitely advantageous for inhibiting the effects of moisture ingress and condensation.5 A further
advantage was that the product used renewable feedstock, allowing it to receive the USDA certified biobased product label.6
Turning the promise of vapour-phase protection into a reality
While it is impossible to eliminate the presence of all rust, many technologies exist to help mitigate the problem in critically significant areas. Vapour phase corrosion inhibitor technology is one of those chemistries that offers important advantages for those who own and maintain fertilizer production facilities. Directing this technology towards boiler layup, AST bottom protection, and CUI, fertilizer plants can protect themselves from several potentially serious losses of production time and asset value.
References 1.
2. 3. 4.
5. 6.
BHASKARAN, R., et al., ‘Cost of corrosion in fertilizer industry – A case study,’ Materials and Corrosion, Vol. 55, No. 1, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, 2004. Accessed 25 Sep 2023 at https:// krc.cecri.res.in/ro_2004/72-2004.pdf. www.apiwebstore.org/standards/655. https://store.ampp.org/ampp-sp21474-2023-external-corrosioncontrol-of-on-grade-carbon-steel-storage-tank-bottoms. CAO, Q., et al. ‘A Review of Corrosion under Insulation: A Critical Issue in the Oil and Gas Industry.’ Metals Journal, Issue 12, MDPI, 25 March 2022. Accessed 22 Sep 2023 at https://www.mdpi.com/20754701/12/4/561. A demonstration of hydrophobicity at https://www.youtube.com/ watch?v=ciyasehf6xk. Commercial name: CorroLogic® CUI Inhibitor Injection.
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Preventing Electronic Corrosion with GPF Systems
Manoj Gupta and Prashant Pasale, Bry-Air, India, outline how gas phase filtration systems are preventing electronic corrosion in the control rooms of fertilizer plants.
T
he growth of the fertilizer industry and its uses are closely tied to global agricultural needs and food production. Fertilizers play a critical role in enhancing soil fertility and crop yields, which is essential to meeting the demands of a growing population. Even the Indian fertilizer market is expanding at a robust rate owing to the growing population and rapid urbanisation, which is incessantly giving impetus to the surge in food consumption. In turn, it is contributing to the rising demand for fertilizers. As per the IMARC report, the market is poised to reach INR 1188.3 billion by 2028. Therefore, this underscores the need for a resilient fertilizer production plant that works without any interruption to continuously meet the rising demand in the market and, at the same time, propel its growth. Deciphering that fertilizers make up an essential element to drive the mass production of agricultural products, the fertilizer industry has improved 45
production processes and included new technologies to speed up the production cycle. The industry utilises advanced automatic machines run by critical electronic equipment secured in control rooms or servers. The control room equipment plays a crucial role in the automation system. Failure of equipment not only increases downtime but also causes huge economic losses for facilities.
What causes failure in control rooms?
In fertilizer plants, corrosive substances such as naphtha, sulfur, fuel oil, sulfuric acid, coal, nitric acid, rock phosphate, phosphoric acid, urea, nitrogen, ammonium dihydrogen phosphate, sodium nitrate, ammonium nitrate, potassium chloride, etc., are heavily used as raw materials. The processing of these volatile chemicals to produce fertilizer generates various corrosive gases in the premises of the fertilizer plant. These corrosive gases typically enter control/server rooms and equipment through leakages with wind direction and even as a result of human activities. When these corrosive gases, along with moisture, come into contact with metal, a part of the electronic equipment results in metal damage and/or the build-up of various corrosion by-products on the metal surface. When left uncontrolled, corrosion adversely affects electronic equipment and systems that run the facilities.
Figure 1. Atmospheric corrosivity monitor.
Figure 2. Gas phase filtration system test laboratory. 46 | WORLD FERTILIZER | MARCH 2024
As a result, fertilizer plants are prone to very high downtime-related expenses and revenue loss due to infrastructure corrosion.
The challenge
Nitrogen is a major component of fertilizer and is also the primary source of corrosion. The compounds/ byproducts of nitrogen, phosphorous, and potassium are the major elements responsible for triggering corrosion in electronic cards and electrical components. Interfering with smooth functioning, it has the potential to bring the entire plant to a halt. Even the slightest trace of contaminants can lead to malfunctioning of the devices which can result in the breakdown of equipment. Therefore, if left unattended, it can consequently cause the shutdown of the plant. Contaminants can jeopardise the complete productivity of the company, as the huge maintenance cost incurred due to damage can lead to acute revenue loss for the company. In addition to this, the gaseous compounds released during the production of fertilizer have a damaging effect not just on the machines but also on the health of the occupants. Being exposed to gases for a prolonged period of time can give rise to vomiting and nausea, and can even lead to decreased efficiency and an increase in absenteeism.
Precautionary steps
Looking at the loss it can incur on the company while inducing serious health issues, it is the need of the hour that industry players monitor and control the concentration level of the harmful gaseous compounds within the space with sheer agility. To achieve this, it is a prerequisite to check the overall corrosive environment before implementing control measures in an enclosed room. Industry players can implement measures such as installing an atmospheric corrosivity monitor (ACM) or corrosion classification coupon (CCC) to help identify corrosive gases. At the same time, this can give detailed insights into the corrosivity level of the space with the categorisation into G1, G2, G3, and Gx, levels. The monitor comes with the ability to provide information about the percentage of gases, giving an idea about the criticality. Here, the ACM or CCC measures the corrosivity environment following the ANSI/ISA-71.04-2013 guidelines. ACM by Bry-Air monitors corrosion potential in real time. It assesses and tracks room temperature, relative humidity, and, if desired, differential pressure. Using copper and silver sensors, it offers qualitative and quantitative information about the overall corrosion risk within an environment or room. The ACM relies on quartz crystal microbalance (QCM) technology to gauge the rate at which the mass of corroded metal sensors increases. These measurements are then extrapolated over a 24-hour period for 30 days to determine the severity level in accordance with the ISA standard.
CCC does not require any electrical connection or calibration and is very simple to use. It allows the customer to assess control room/server room air quality as well as evaluate the performance of the gas phase filtration (GPF) systems in post installation tests. CCC is placed at one or multiple locations for a period of 1 – 30 days where the environmental corrosivity rate is to be measured. The coupon is then tested in GPF laboratories.
Quality air solutions
Media testing plays an imperative role in controlling corrosion. Being proficient at identifying corrosion with the help of corrosion coupons, it can detect the influx of gases in the process. Following the information on the corrosivity level, adopting quality air solutions aids in eliminating the airborne contaminants present within the premises of the control room. Here, installing gas phase filtration (GPF) systems effectively eliminates corrosive gases from the enclosed space. It is essential to address corrosive gas within control rooms of fertilizer facilities. The GPF units eliminate corrosive gases effectively and optimise operational efficiency and profitability. The successful installation serves as a valuable reference for similar industries seeking to create a secure and productive working environment.
Application of technology
Looking at the crucial role fertilizers play in the food industry, GPF technology finds application in a wide range
of control rooms to protect sensitive electronic equipment from corrosive gases. Below is the list of control rooms where technology is required extensively: n Ammonia plant control rooms. n Urea plant control rooms. n DAP plant control rooms. n Phosphoric plant control rooms. n Sulfuric plant control rooms. n Ammonium sulfate plant control rooms. n Substation control rooms. n Critical VFD rooms. n Server rooms.
Benefits of GPF technology
The technology is extremely efficient at removing airborne contaminants from space. Being well equipped with a certified honeycomb chemical media filter, it is adept at meeting the standard of air quality outlined by ANSI/ISA-71.04-2013.
Conclusion
To suit the diverse needs of the industry and the users, GDF technology can be adapted for a range of sizes and corrosivity levels. For example, the number of chemical filters and their composition can vary on the basis of the corrosivity level and type of corrosive gases present in the environment. These filters are easy to replace. Also, the technology comes with the in-house capacity to check media life to ensure complete usage of chemical filters.
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