Fall/Winter 2021

Covering Best Practices for the Industry

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Nyrstar’s Port Pirie tackles NOx at sulfuric acid plant Page 7

IN THIS ISSUE > > > > Sulfuric acid prices riding high into 4Q21 page 10

Acid plant debottlenecking strategies page 24

The latest in sulfuric acid plant process gas dewpoint/moisture leak detection Page 28

Clean Technologies

Making everyday life better, safer, cleaner For 100 years, we have partnered sulfuric acid producers with innovative technology and expert trouble-shooting technical support. And our tradition of designing advanced solutions to solve site-specific challenges continues – so we can together deliver cleaner air productively, efficiently and reliably.

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MECS® Sulphuric acid & environmental technologies Copyright © 2019 DuPont. The DuPont Oval Logo, DuPont™, is registered trademarks or trademarks of E.I. du Pont de Nemours and Company or its affiliates. All rights reserved.

Sulfuric Acid

Covering Best PraCtiCes for the industry

Sulfuric Acid T

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www.H 2S0 4Today.com

Fall/Winter 2021

Nyrstar’s Port Pirie tackles NOx at sulfuric acid plant Page 7

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Vol. 27 No. 2

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Covering Best Practices for the Industry

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Fall/Winter 2021

IN THIS ISSUE > > > > sulfuric acid prices riding high into 4Q21 page 10

FROM THE PUBLISHER

acid plant debottlenecking strategies page 24

the latest in sulfuric acid plant process gas dewpoint/moisture leak detection page 28

On the Cover…

7 Nyrstar’s Port Pirie tackles NOx at sulfuric acid plant Departments…

4 Industry Insights News items about the sulfuric acid and related industries 16 Lessons Learned

Case histories from the sulfuric acid industry

26 Product News

Latest developments in technology

Dear Friends,

Welcome to the Fall/Winter 2021 issue of Sulfuric Acid Today magazine. We have dedicated ourselves to covering the latest products and technology for those in the industry, and hope you find this issue both helpful and informative.

With the development and wide distribution of vaccinations, as well as the United States opening the Canadian and Mexican borders to vaccinated travelers, we have decided to host our 2022 Sulfuric Acid Roundtable (SAR) in person, April 4-7, 2022 in The Woodlands, near Houston, Texas. SAR 2022 will follow CDC recommendations for proper social distancing protocols during the course of the two-and-a-half day meeting and we are looking forward to hosting another successful conference. The event will consist of informative technical presentations, panel discussions, networking events, and a plant tour of Eco Services’ Houston acid plant. Please see our article on page 34 for more information.

In the Spring/Summer 2021 issue of Sulfuric Acid Today, Acuity Commodities discussed the recovery of the sulfuric acid market from the Covid-19 pandemic.

Now several months later, key impacts include the permanent loss of sulfur production because of the pandemic and a sustained rally in commodity prices. Please see Acuity Commodities’ informative article ‘Sulfuric acid prices riding high into 4Q21’ on page 10 for further details.

Also in this issue, we have several informative articles regarding state-of-the-art technology and projects. Our cover story, on page 7, focuses on a recently completed NOx abatement project at Nyrstar’s Port Pirie complex’s sulfuric acid plant. Abating nitrogen oxides created from metals processing was part of a continuous improvement plan aimed at increasing sulfuric acid quality. Sulphurnet introduces a new process that analyzes the quantity of sulfur flour as well as provides a valid end-of-pipe-solution in the sulfur melting section

EDITOR April Kabbash EDITOR April Smith Marketing ASSISTANT Tim Bowers DESIGN & LAYOUT 281-545-8053 Mailing Address: P.O. Box 3502 Covington, LA 70434 Phone: (985) 807-3868 E-Mail: kathy@h2so4today.com www.h2so4today.com SUBSCRIPTIONS U.S. Plant Personnel —‑Complimentary U.S. Subscription —‑ $39 per year (2 issues) Internat’l Subscription —‑$59 per year (2 issues) Subscribe Online: www.h2so4today.com

Sincerely, Kathy Hayward

FEATURES & GUEST COLUMNS

PUBLISHED BY Keystone Publishing L.L.C. PUBLISHER Kathy Hayward

(page 12); Weir Minerals reevaluates customer service during the Covid-19 pandemic with innovative online video training (page 14); DuPont shares some lessons learned regarding hydrogen generation and ignition in sulfuric acid plants (page 16); Ecorobotics performed a project for a fertilizer producer utilizing their robotic cleaning system (page 18); VIP International shares the proper steps for outage ventilation to ensure the safety of workers, keep equipment in operation, and minimize disruption to turnaround schedules (page 20); Beltran Technologies explains how wet electrostatic precipitators can vary greatly in design, materials, gas flow rates, durability, and collection efficiency, and the importance of engineers being able to recognize the key differences among these various systems (page 22); NORAM Engineering & Constructors delves into some strategies to increase the capacity of an acid plant (page 24); Breen shares the latest in sulfuric acid plant process gas dewpoint/moisture leak detection (page 28); and Clark Solutions reflects on 30 years of their sulfuric acid innovations (page 32).

I would like to welcome our new and returning Sulfuric Acid Today advertisers and contributors, including: Acid Piping Technology Inc., Acuity Commodities, Alphatherm Inc., BASF, Beltran Technologies, Breen Energy Solutions, Central Maintenance & Welding, Chemetics Inc., Clark Solutions, DuPont MECS, Ecorobotics, Koch Knight LLC, Mercad Equipment Inc., NORAM Engineering & Constructors, Optimus, STEULER-KCH GmbH, Southwest Refractory of Texas, Spraying Systems Co., Sulphurnet, VIP International, and Weir Minerals Lewis Pumps.

We are currently compiling information for our Spring/ Summer 2022 issue. If you have any suggestions for articles or other information you would like included, please feel free to contact me via email at kathy@h2so4today.com. I look forward to hearing from you.

10

Sulfuric acid prices riding high into 4Q21

12 Gas treatment in sulfur melting plants

14

14 Providing customer support for sulfuric acid plants during the pandemic 18

Remote controlled robots clean tanks safely and efficiently

20 Planning for outage ventilation 22

24

Wet electrostatic precipitators for superior sulfuric acid gas and mist cleaning

24 Acid plant debottlenecking strategies 28

The latest in sulfuric acid plant process gas dewpoint/moisture leak detection

32

Clark Solutions: 30 years of continuous innovation

34

Sulfuric Acid Today to host 2022 Sulfuric Acid Roundtable in Texas

28

Department

Industry Insights ANDRITZ to supply the world’s first sulfuric acid plant in a pulp mill, producing commercial-grade, concentrated sulfuric acid for Klabin’s Ortigueira facility GRAZ, Australia—International technology group ANDRITZ has received an order to supply a sulfuric acid plant for Klabin’s Ortigueira mill in Brazil. The plant will be the first of its kind worldwide and is designed to produce 150 tons of commercial-grade (>98%) sulfuric acid per day from concentrated odorous gases and elemental sulfur. Once completed, the plant will serve Klabin’s Puma I and Puma II pulp lines at Ortigueira and make Klabin’s Ortigueira site completely self-sufficient in sulfuric acid.

ANDRITZ will supply technologies on EPCC basis for elemental sulfur handling, sulfur, and concentrated non-condensable gases (CNCG) combustion to form sulfur dioxide (SO2), sulfur dioxide conversion into concentrated (98% by wt.) sulfuric acid, and a flue gas handling system. The sulfuric acid plant uses wet-gas sulfuric acid (WSA) technology developed by Haldor Topsoe. The WSA technology has been proven in more than 150 references in many industries.

Once the sulfuric acid plant has been started up, it will help Klabin to control the sodium and sulfur balance and the sulfidity of the mill. Also, the resource efficiency of

the Ortigueira site will be improved because less sulfate needs to be discharged due to the optimized Na/S balance, there is less truck traffic to the mill due to the chemical savings, and there is also less hazardous truck traffic because sulfur is transported in solid form and not as an acid. The sulfuric acid plant meets very strict air emission limits and does not produce any waste streams.

The technology used for this plant is based on ANDRITZ’s self-developed A-Recovery+ concept that enables pulp mills to extract side streams from the pulping process and turn them into commercial-grade products/commodities. ANDRITZ recently completed a successful start-up of the world’s first methanol purification plant based on the A-Recovery+ concept. A-Recovery+ now also offers solutions for the treatment of odorous gases in the pulp and paper industry as well as for production of sulfuric acid from these gases.

For more information, please visit www.andritz.com.

The sulfuric acid plant producing commercialgrade, concentrated sulfuric acid for Klabin’s Ortigueira facility will be first of its kind worldwide.

For the past 30 years VIP International has led the industry in innovative equipment and procedures in maintaining sulfuric acid plants. As the industry demands longer run times between catalyst screening, VIP’s patented catalyst handling system ensures the longest run time with lowest pressure drops to ensure maximum performance of your converter. Contact VIP International to learn how to reduce your downtime and increase your production and on stream factor.

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PAGE 4

Metso Outotec signs order for design and engineering of a copper smelter for Freeport Indonesia Manyar project

HELSINKI, Finland—Metso Outotec has signed a major engineering and technology contract as well as license agreements for the delivery of a landmark copper smelter complex to be built in Gresik, East Java, in Indonesia.

The project owner is PT Freeport Indonesia, and PT Chiyoda International Indonesia is the EPC contractor.

Metso Outotec’s scope of delivery is based on the licensed, well-proven Metso Outotec Flash Smelting, Flash Converting, and Lurec® technology. It includes the design and supply of key process equipment and process control systems for the main areas of the smelter complex, the copper electrolytic refinery, the gas cleaning and sulfuric acid plant, the slag concentrator, and the effluent treatment plant.

Metso Outotec has previously provided certain front-end engineering design (FEED) and other advanced engineering services for this 1.7 mtpa copper concentrate smelter complex. This complex is expected to be commissioned in 2024.

“Our joint efforts with Freeport Indonesia and Chiyoda will set a new standard for the copper smelter industry in fulfilling the strictest international environmental standards and efficiency requirements. We are very happy to work together to implement this game changing copper smelter,” said Pekka Vauramo, President & CEO, Metso Outotec.

“We have worked with Freeport Indonesia and Chiyoda for several years to ensure and select the best available process design and technologies for the Manyar project,” said Jari Ålgars, President, Metals business area at Metso Outotec.

Metso Outotec has delivered 51 copper flash smelters around the world. Metso Outotec copper flash smelting is the most widely applied technology for copper smelting in the world and one of the company’s Planet Positive solutions. Using this technology, Metso Outotec’s customers avoided more than 1.6 million tons of CO2 emissions in 2020.

For more information, please visit www.mogroup.com.

Ecovyst launches as a high growth, pure-play catalysts and services company; Performance Chemicals sale completed

MALVERN, Pa.—PQ Group Holdings Inc., a leading integrated and innovative global provider of specialty catalysts and services, announced recently that it has completed the sale of its Performance Chemicals business to a partnership established by Cerberus Capital Management, L.P. and Koch Minerals & Trading LLC for a purchase price of $1.1 billion.

The company plans to use the net cash proceeds from the sale to reduce its debt by approximately $525 million and return cash to shareholders through a special dividend of $3.20 per share, subject to final Board approval and declaration.

Citi is serving as lead financial advisor with BMO Capital Markets Corp. as coadvisor, and Ropes & Gray LLP is serving as legal counsel to PQ in the sale of Performance Chemicals. Jefferies, LLC served as financial advisor, and Kirkland & Ellis LLP served as legal advisor to Cerberus and Koch. Jones Day served as legal advisor to Koch.

“I am extremely proud of the team achieving a timely and efficient close of this transaction. Further, we are pleased to provide another meaningful return of capital to shareholders through a special dividend,” said Belgacem Chariag, PQ’s Chairman, President and Chief Executive Officer. “While our name is changing to Ecovyst, our culture and focus on innovation and customer collaboration will remain one of our greatest strengths. We are excited to move forward with Ecovyst’s strategic growth plans, prioritizing and accelerating our Growing and Greening initiatives, and putting sustainability for a safer, cleaner, healthier world at the forefront of our strategy.”

After the purchase, PQ Group Holdings Inc. became Ecovyst Inc., a pure-play catalysts and services company with a sustainability focus and industry leading growth outlook.

The new company will comprise two highgrowth, high-margin businesses, Eco Services and Catalyst Technologies, formerly Refining Services and Catalysts, respectively.

Eco Services Operations Corp. provides sulfuric acid recycling to the North American refining industry for the production of alkylate and provides on-purpose virgin sulfuric acid for water treatment, mining, and industrial applications. Catalyst Technologies provides finished silica catalysts and catalyst supports necessary to produce high strength and high stiffness plastics and, through its Zeolyst joint venture, supplies zeolites used for catalysts that remove nitric oxide from diesel engine emissions as well as sulfur from fuels during the refining process.

For more information, please visit Ecovyst’s new website at www.ecovyst.com.

INEOS Enterprises completes sale of its sulfur chemicals business to International Chemical Investors Group

HEFEI, China—INEOS Enterprises recently announced the completion of the sale of its sulfur chemicals business to International Chemical Investors Group. INEOS Sulfur Chemicals business is Spain’s largest dedicated manufacturer of sulfuric acid and oleum serving end-applications ranging from agriculture to chemical intermediates. Its 400,000 tonne state of the art manufacturing facility with an excellent sustainability footprint is located in Bilbao, Northern Spain.

The business will become part of WeylChem’s advanced intermediates and reagents portfolio which includes an existing sulfuric acid and oleum plant located in Lamotte, Northern France. WeylChem is wholly owned by the International Chemical Investors Group. The agreement is an important step in the continued development of both businesses and presents new opportunities to the 50 employees based in Bilbao as they join what will be one of the leading European Sulfur Chemicals companies.

“I am very pleased to have completed Sulfuric Acid Today • Fall/Winter 2021

the sale of the INEOS Sulfur Chemicals business, which now becomes part of a strategic business unit within International Chemical Investors Group,” said Ashley Reed CEO INEOS Enterprises. “The business is an attractive addition to WeylChem’s advanced intermediates and reagents portfolio that will help secure future development and growth, to meet customer needs in Europe.”

Dr. Uwe Brunk CEO WeylChem Group of Companies stated, “This acquisition underlines our commitment to bolstering our position as a strategic partner in advanced intermediates and reagents. INEOS Sulfur Chemicals and our French operations at WeylChem Lamotte complement each other perfectly.

This combined business will be an agile, customer-focused player with superior services and supply certainty provided to demanding customers across Europe.”

For more information, please visit www.ic-investors.com.

ioneer awards sulfuric scid plant contract to DuPont Clean Technologies

NORTH SYDNEY, New South Wales— ioneer Ltd, an emerging lithium-boron supplier, recently announced it has awarded DuPont Clean Technologies (DuPont) a contract for the license, engineering, and supply of proprietary equipment for the planned sulfuric acid plant at the company’s Rhyolite Ridge Lithium-Boron Project in Nevada.

Specialty technology provider DuPont will work with engineering partner SNCLavalin on the plant design, providing best-inclass MECS® sulfuric acid production technology for a plant with a capacity of 3,500 tonnes per day, and controls that limit emissions to among the lowest in the world for this type of facility. The DuPont contract is conditional on a final investment decision by the ioneer Board of Directors.

Employing advanced technologies, the plant will meet stringent NV Class II air quality standards and water pollution control.

DuPont will also supply its latest generation MECS® Super GEAR™ catalyst and other critical proprietary equipment.

The plant will convert sulfur into commercial grade sulfuric acid, used to leach lithium and boron from the crushed rock. The heat released in the process will be recovered to produce steam for electricity. The plant will generate an initial 35 MW of electricity, which is sufficient to power the entire Rhyolite Ridge operation and means ioneer will not draw electricity from the grid. Rhyolite Ridge will be an energy-independent operation, using primarily co-generated, zero-carbon power. The heat generated will also be used for evaporation and crystallization processes required to produce lithium carbonate and boric acid.

The plant’s capability was an instrumental part of ioneer’s receipt of a Class II Air Quality Permit in June 2021 by the State of Nevada Division of Environmental Protection Bureau of Air Pollution Control, which is a requirement to begin construction. It is the first sulfuric acid plant permitted in Nevada.

Once operational, Rhyolite Ridge is expected to produce 20,600 tonnes per annum (tpa) of lithium carbonate, converting in year four to 22,000 tpa of battery-grade Sulfuric Acid Today • Fall/Winter 2021

WASTE HEAT RECOVERY BOILERS SUPERHEATERS ECONOMIZERS

lithium hydroxide, and 174,400 tpa of boric acid. Pending final federal US Department of the Interior (DOI) approval of the Plan of Operation, the project is expected to begin production in the second half of 2024.

Commenting on the contract, ioneer Managing Director, Bernard Rowe, said: “Development of the Rhyolite Ridge lithiumboron project is a critical strategic step to enable US production of lithium-ion batteries for electric vehicles (EV) and renewable energy storage. ioneer’s core commitment is to produce essential materials in an environmentally and socially responsible and sustainable manner through lowered emissions, reduced water usage, and a minimal surface footprint.

We are delighted to welcome MECS-DuPont to our team. It is a world-leader in clean technology and emissions control and will work alongside ioneer to deliver this tier-1 project in the US.”

Global business leader of DuPont Clean Technologies, Eli Ben-Shoshan, said: “We have worked in close partnership with ioneer and SNC-Lavalin to be able to guarantee the precise performance and emissions control ioneer needs for its Rhyolite Ridge project to meet stringent environmental standards and production objectives. We are excited to be part of a project that helps ioneer cleanly produce lithium essential to advancement of electric energy markets and to be able to support it with our many decades of expertise in sulfuric acid plant technology.”

DuPont Clean Technologies brings over 90 years of expertise to best-in-class sulfuric acid plant engineering, processes, energy recovery and environmental technologies, and also provides a range of specialty products and services to numerous other industries. The company has designed more than a thousand customized plants worldwide to enable producers to run efficient, competitive plants with low CAPEX and OPEX costs tailored to suit their feedstock, location, local environmental regulations, energy requirements, and industry.

For more information, please visit www.ioneer.com.

Chemetics awarded Bodal Chemicals Ltd. new sulfuric acid plant contract

VANCOUVER, Canada – Chemetics Inc. has been awarded a contract by Bodal Chemicals Ltd., India for a new 1050 MTPD sulfuric acid plant using solid sulfur as feedstock. The plant will produce both 32-33% oleum and 98.5% sulfuric acid as products which will be used

by Bodal Chemicals Ltd. for the production of dye intermediates. Based on vision and desire of Bodal Chemicals Ltd. for conservation of water and maximization energy recovery, the new sulfuric acid plant will be designed using an air-cooled cooling water system and an enhanced boiler feed water preheating system with SARAMET® acid coolers.

This project continues Chemetics success in serving the Indian sulfuric acid market. In the last three years Chemetics has signed contracts for three new sulfuric acid plants and several sulfuric acid concentration plants in India.

For more information, please visit, www. worley.com/chemetics. q

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Cover Story

Nyrstar’s Port Pirie tackles NOx at sulfuric acid plant

Nyrstar’s Port Pirie multi-metal smelting facility in South Australia recently upgraded its sulfuric acid unit to mitigate nitrogen oxides.

By: April Smith, Editor, Sulfuric Acid Today

O

n the heels of a major redo of Nyrstar’s Port Pirie operation in South Australia, the metals producer recently completed a NOx abatement project at the

ies in South Australia. The smelter is one of the area’s major

greater proportion of value contained in a wider range of

the smelter are intrinsically linked and Nyrstar has a strong

residues and concentrates. The key aspects of the redevel-

from metals processing was part of a continuous improve-

with the community to reduce exposure and improve com-

facility’s sulfuric acid plant. Abating nitrogen oxides created ment plan aimed at increasing sulfuric acid quality.

About Port Pirie

Port Pirie is an integrated multi-metals recovery plant

capable of processing a wide range of lead-rich concentrates and smelting industry by-products. As one of the world’s

largest primary lead smelting facilities and the third largest

businesses, employing over 700 people. The community and focus on reducing emissions from the site and has worked munity health.

Nyrstar Port Pirie is part of Nyrstar, a global multi-

metals business with a market leading position in zinc and lead, and growing markets in other metals. Employing over 4,000 people, Nyrstar has mining, smelting, and other operations in Europe, the United States, and Australia.

silver producer, Port Pirie generates significant economies of

Redeveloping the facility

copper cathode, silver dore, and sulfuric acid.

project at Port Pirie, converting the operation into an

scale. The facility’s end products are commodity-grade lead,

In continuous operation for over 130 years, the smelter

is located in the city of Port Pirie, one of the key regional citSulfuric Acid Today • Fall/Winter 2021

In 2018, Nyrstar completed a major redevelopment

advanced metal recovery and refining facility with greater operating flexibility. This enabled the site to capture a

high-margin feed materials, including internal zinc smelter opment included replacing the existing sinter plant with an

oxygen enriched bath smelting furnace and replacing the

existing sulfuric acid plant with a new plant with greater capacity and upgraded technology.

Implementing NOx abatement

A combination of factors in Port Pirie’s furnace opera-

tion was generating NOx levels in product acid above cus-

tomer requirements, which is less than 30 g/t.

Port Pirie uses an Outotec Ausmelt top submerged lance

(TSL) furnace to produce lead bullion and a high lead slag.

The sulfuric acid plant converts the sulfur dioxide contained in the furnace’s off gas to produce concentrated sulfuric acid.

A combination of the TSL furnace’s operating temperature, PAGE 7

Cover Story

Major redevelopment of Port Pirie’s metal operation underway in 2017.

Port Pirie in 2018 after complete redevelopment of the facility.

Nyrstar’s Port Pirie operation in South Australia is home to one of the world’s largest lead smelters.

feed stock, and fuel type was creating the high NOx levels.

Quick Facts

The NOx generated in the TSL furnace enters the acid

plant where it reacts with sulfuric acid to form nitrosylsul-

furic acid (HNOSO4). While NO is essentially insoluble in H2SO4, NO2 dissolves to create nitrosylsulfuric acid, which

Port Pirie sulfuric acid plant • Metallurgical double-contact doubleabsorption.

• Converter with four catalyst beds.

• Treats TSL furnace off gas containing 7-12% SO2.

• Feed gas is conditioned in a wet gas cleaning plant using GEA Bischoff technology— the most robust and efficient system for removing impurities from metallurgical off gas containing SO2.

• Impurities removed include: metallic oxide dusts (PbO, ZnO), condensable vapors (arsenic, selenium, mercury), acid mist, water vapor, and hydrogen fluoride.

forms fine droplets that are carried to the candle filters of

both the Intermediate Absorption Tower (IAT) and Final Absorption Tower (FAT). The nitrosylsulfuric acid then drips

into the candle filter seal pots, overflows into the towers, and enters the product acid stream.

Fig. 1: Percentage NOx reduction in sulfuric acid at Port Pirie.

In late 2018, the project team at Port Pirie made some

process adjustments, which reduced the NOx levels in prod-

uct acid by 20-50 percent, but further changes were needed

adjust to varying NOx inputs,” Wright said.

to reach the target specifications.

sulted with engineering firms to come up with the best solu-

that is vented via the existing suction system through the

ered multiple reagents (including hydrazine addition, urea or

project (including scrubbing, Selective Catalytic Reduction,

being added, ensuring 98.5 percent acid strength could be

assessment, they chose sulfamic acid and hydrogen peroxide

“So we conducted a thorough literature review and con-

The addition of sulfamic acid and hydrogen peroxide

destroys the nitrosylsulfuric acid by making nitrous oxide

tion,” explained project engineer, Amy Wright. They consid-

acid plant stack. Table 1 shows the reactions.

ammonia) and longer term processes as a second stage to the

tower circulating tanks to offset the dilution water that was

and Selective Non-Catalytic Reduction). After a complete

maintained during periods of high dosing requirements.

dosing as the next step on the NOx abatement journey. “This

its challenges, the largest one being navigating a global

was the quickest to install and offered the most flexibility to

The team decided to add the reagents to the absorption

Like every project team, the NOx abatement team had

pandemic. “Because of Covid-19, we had to switch our

intended supplier of hydrogen peroxide; and it also affected

PAGE 8

By late 2020, the team further optimized the plant,

improving operational performance and reducing costs. “It has been a great success story for the plant,” Wright said.

With the NOx abatement project complete, Port Pirie is

lead times on some equipment,” Wright said. But strong

focused on other continuous improvement projects—some

team achieved a consistent 92-98 percent NOx reduction in

to improve our process whilst also enhancing our environ-

team dynamics and tenacity ultimately prevailed, and the

280 of them—currently underway. “We are highly motivated

product acid (see Fig. 1).

mental performance across the site,” Wright said. q

Oxidation

NOHSO4 (l) Nitrosylsulfuric acid

+

H2O2 (l) Hydrogen peroxide

→

NO2HSO4(l) Nitronium hydrogen sulfate

+

H2O (l) Water

Reduction

NO2HSO4 (l) Nitronium hydrogen sulfate

+

H2NSO3H (l) Sulfamic acid

→

N2O (g) Nitrous oxide

+

2H2SO4(l) Sulfuric acid

H2O2

+

H2NSO3H

→

N2O

+

H2O

Overall Project champion, Amy Wright, in front of the TSL furnace.

NOHSO4

+

+

2H2SO4

Table 1: The chemical reactions of nitrosylsulfuric acid with hydrogen peroxide and sulfamic acid.

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Feature

market outlook

Sulfuric acid prices riding high into 4Q21

Fiona Boyd, Acuity Commodities

Freda Gordon, Acuity Commodities

By: Fiona Boyd and Freda Gordon, Directors of Acuity Commodities

In the Spring/Summer 2021 issue of Sulfuric Acid

Today, we discussed the recovery of the sulfuric acid market from the Covid-19 pandemic. Now several

months later, key impacts remain the permanent loss of sulfur production because of the pandemic and a sustained rally in commodity prices.

In terms of the loss of sulfur production, it contin-

ues to constrain availability of the raw material for sulfuric acid producers. We previously noted around 2.4m t of lost production between Europe and the United States alone just last year compared with 2019.

While on a longer-term basis we still expect overall

in the accompanying graph.

have adjusted operational rates due to acid pricing and/

and firm demand for fertilizer production was apparent

In the sulfur market, the impact of lower production

when the Tampa molten sulfur quarterly contract price

was agreed at an increase of $96/lt, resulting in the raw

material benchmark price doubling to $192/lt DEL, the highest level in almost 10 years (4Q11).

In the spot sulfur market and resulting quarterly

settlements, prices have remained firm due to the snug

availability. This is despite a lack of notable import buying liquidity in the key import market of China since 2Q.

Despite reduced sulfur supply, there is a notable

growth in sulfur production as new refining and natural

amount of sulfur-based acid moving to meet demand in

impact on trade flows. This is because new sources of

tion. In some cases, it is from atypical sources because

helping offset the overall decline in the west of Suez.

term shift towards lower carbon emissions and electric

challenging sulfur sourcing post Covid-19 a contribut-

ing sector, which has historically represented around

yr is adding to reduced smelter acid spot exports from

the EV trend continues to bode well for sulfur and

markets.

of raw materials such as copper and lithium for key

even labor disputes reducing sulfuric acid production,

Shifting back to the present, many commodity

lent in North America (for example) where a smelter in

article we discussed how copper pricing hit a 10-year

strike action. A restart of the acid plant was expected

metal has firmed even further. We have also continued

unplanned operational issues have been seen in part due

supporting consumption for both sulfur and sulfuric

The firm demand as well as tight supply availabil-

supply available out of its traditional supply source of

in pricing accordingly. But with pricing for most down-

deliveries to the domestic market that saw a shortage

tion of higher raw material costs.

prioritizing product to contractual buyer in Morocco–

gas processing capacity comes online, we anticipate an

the merchant market rather than for captive consump-

production will be mainly concentrated east of Suez,

of the favorable economics.

There is also increasing interest in how the long-

supply in the UK with a closure at Runcorn with more

vehicles (EVs) will effect sulfur produced by the refin-

ing factor. The loss of this supply of around 200,000 t/

50% of elemental sulfur output globally. Meanwhile,

Europe as buyers seek alternative supply from nearby

sulfuric acid demand, including to support production

components.

squeezing an already tight market. This has been preva-

prices have remained firm in recent months. In our last

Canada (Vale – Sudbury) was idled back in June due to

high in February 2021. Since then, pricing for the red

around mid-September. In the United States, notable

to see firm phosphate fertilizer pricing. This is in turn

to weather events.

acid at peak levels.

disruptions has been limited with essentially no spot

ity for both products has of course resulted in a tick up

Europe. European smelters have been focusing on acid

stream products firm, it has allowed for easier absorp-

of molten sulfur in 1H21. Smelters here have also been

In the acid market for example, we have seen the

average Chilean spot sulfuric acid price climb in tan-

dem with copper pricing in recent months as reflected

Meanwhile, we have seen a loss of sulfur-based

We have also seen several operational issues and

In the meantime, supply options to cover these

fertilizer producer OCP.

In the world’s largest acid import market of Chile,

we saw strike action averted in June that would have

had a notable impact on consumption. Since then, acid prices have risen steadily with a notable amount of spot demand to cover in 2H.

Globally some buyers have tried to show resistance

to the price growth. For example, we have seen a few buyers scrap purchase tenders citing high price offers.

In the end, however, business is usually concluded due

to lack of other options, and we have seen re-tenders attracting even higher price offers. And while some PAGE 10

or its availability, this has been relatively limited.

Also of note is the amount of forward buying to

cover consumption requirements amid a tight market.

Rather than looking for cargoes for prompt shipment, buyers were in the market as early as July to secure cargoes for November arrival. We also saw sales from

the Far East back in May being made as far forward as for 4Q shipment with demand firm in the west of Suez while nearby markets such as India were not paying up.

Over the past few months, the growth rate in CFR val-

ues in India and southeast Asia have been much slower than most other markets.

In addition to low prompt availability contributing

to higher prices, market participants have been dealing with higher freight rates. As an example, freight from

Japan/South Korea to Chile was within the range of $57-68/t CFR in 1Q21 before climbing to the $80s/t in

May where it remained as of late 3Q. Drivers for higher

freight rates include constrained cargo availability and Covid-19 impacts.

As we look to 2022 and market participants deter-

mine their strategies in a bullish market, freight will be a key component of the thought process.

We also note the ongoing gap in sulfuric acid pric-

ing in the east of Suez versus the west of Suez with the

former lagging behind in terms of pricing. This makes

preparing for longer-term price discussions rather difficult for both the buy and sell sides. The gap between

prices in the east and the west will likely have to close, or at least narrow, before formal price discussions can

progress meaningfully. This begs the question: Will CFR prices in the east rise further, or will CFR prices in the west soften?

Looking to next year, we also continue to focus on

the unpredictability of the Chinese market. This year

there has been a notable amount of sulfur-based sulfuric acid moved offshore due to favorable economics. But at

the same time, exports of smelter acid have been limited in part because domestic acid prices in China remain

firm. For 2022, key factors will be the health of the domestic market as well as copper market fundamentals that will influence smelter performance accordingly.

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Feature

Gas treatment in sulfur melting plants By: Jan Hermans, Director, Sulphurnet

The majority of the sulfur present in the market is produced from refinery waste, where hydrogen sulfide (H2S) is converted to sulfur by the Claus process. The sulfur is degassed and then prilled, pelletised, and distributed all over the globe. This solid sulfur contains low concentrations of H2S and during transport water will accumulate (mainly depending on the method of storage).

When remelting solid sulfur, gaseous emissions are constantly being produced. From the evaporated water, H2S will partially release and a lesser known, invisible, and corrosive product called sulfur flour is formed.

Due to environmental regulations, the levels of H2S emission have to be minimized. This can be done by installing a conventional gas scrubbing system like a spray tower. In a spraying tower, H2S is removed from the gas by bringing it into contact with a solution of sodium hydroxide (NaOH) or hydrogen peroxide (H2O2). The H2S reacts with these chemicals and is neutralized.

However, the amount of sulfur flour formed during sulfur melting disturbs the scrubbing process. A conventional scrubber will work only 2-3 days and then an intensive cleaning process has to be performed.

The formation of sulfur flour is a complex process; it depends on various parameters such as the humidity of the vapor, gas volume, and gas-temperature, as well as the temperature of the liquid sulfur.

The vapor exiting the melting tank consists of an aerosol.

The sulfur that nucleates on these particles can be either solid or liquid as mentioned in the research literature. The particle size distribution varies widely and can range from sub-micron

to micron size particles.

Sulfurnet performed some practical tests in a sulfur plant that melted 20 m ton sulfur per hour. We measured the sulfur flour produced and then compared the experimental data with the results obtained from a semi-empirical model that was developed in house. The results found during testing came within a deviation as close as 10% of the established model.

Based on that outcome a new process was developed that combines the removal of sulfur flour Sulfur flour deposit in with a H2S neutralization step. piping.

In the initial step, the vapor from the sulfur melter is intensively mixed with a caustic solution. During this step, a large amount of sulfur flour is knocked out of the gas stream with the liquid solution. The second step consists of spraying the gas stream, now almost free of particles, with the NaOH solution to neutralize the H2S. This results in sodium bisulfide (NaHS) and water (H2O). The NaHS reacts further in the presence of the basic environment to form sodium sulphide (Na2S) as seen in reactions 1 and 2.

Reaction 1: H2S + NaOH  NaHS + H2O Reaction 2: NaHS + NaOH  Na2S + H2O

These reactions happen under basic conditions and may

reverse when the pH get neutralized or slightly acidic. The water that contains the product of the reaction is thus brought to a treatment tank where sodium hypochlorite (NaOCl) is added to form sodium chloride (NaCl) and sodium sulfate (Na2SO4), as seen in reaction 3. The treated water is then sent to a water cleaning facility for further processing.

Reaction 3:

Na2S + 4 NaOCl  4 NaCl + Na2SO4

The non-reacted sodium hydrogen solution is recycled in the system, preventing losses of the water solution.

Fig. 1: Gas treatment sulfur melting tank.

With this new process, Sulphurnet is in the position to analyze the quantity of sulfur flour formed in the process as well as provide a valid end-of-pipe-solution in the sulfur melting section.

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Sulfuric Acid Today • Fall/Winter 2021

Feature

Providing customer support for sulfuric acid plants during the pandemic By: Martha Villasenor, Regional Sales Manager, Weir Minerals

The Covid-19 pandemic has changed what customer support looks like for nearly all businesses and organizations worldwide.

Sales and customer service teams are discovering new ways to provide help as social distancing and working remotely become the standard. What has not changed, however, is the need for customers to feel connected and know that they are supported.

These fundamental aspects of caring for the customer remain essential in 2021.

Prior to the pandemic, we had the opportunity to visit acid plants around the globe.

We went onsite and talked to the process, maintenance, purchasing, and engineering teams to learn about their needs, upcoming turnarounds, and new projects or expansions. These visits also allowed us to become acquainted with new hires, understand customer challenges, and offer advice on how to improve operational uptime based on examining wear patterns and specific scenarios.

As we entered the pandemic, all plants started to adapt to social distancing and enhanced safety protocols. Operation managers started coordinating teleconferences for internal meetings and it became very difficult to be on site physically. All matters were limited to phone conversations and online meetings. Roundtable events were also cancelled, which decreased the amount of information shared, resulting in a lack of understanding of new challenges in the customer’s operation. All of these changes are good and are essential to slowing the spread of Covid-19, but how do we still provide support without being onsite to discuss operational concerns face-to-face?

In addition, sulfuric acid plants suddenly faced a decrease in production due to a limited number of onsite staff and a decrease in demand as the global economy slowed.

As the world realized that the Covid-19 pandemic was not going away soon, we had to reevaluate what it looked like to provide service and care to our customers.

We understood that we had to adapt to the new landscape of people working remotely and figure out how to remain consistent, and even excel in providing support to our customers in this new normal.

One of the first items on our agenda was to reconnect with our customers.

We held video conferences with our users and representatives providing training and seminars. We exchanged video recordings with our customers regarding onsite pump operations to learn about any new issues and monitor the existing equipment to ensure it was running properly. To accommodate the customer’s social distancing guidelines, we repeated several online sessions due to the limited number of people physically allowed in the conference room at the customer’s location. As supply chains required longer lead times, we were able to keep customers updated about delays quickly so they could react and plan ahead. While many companies were using these communication PAGE 14

Cristian Gonzalez, Weir Minerals product manager, suited up to inspect pump in absorption tower.

tools prior to Covid-19, they had not been exploited to the extent that was used during the peak of the pandemic.

As the pandemic continued and some restrictions were being lifted, it became possible to visit customers onsite for specific problems and needs by obtaining special approval and Covid-19 antigen tests. Some countries, like Chile, required us to be quarantined prior to our site visit. Cristian Gonzalez, a Weir Minerals product manager in Chile, talked about how he and his team had to follow strict guidelines provided by the Chilean government before visiting a customer’s operation to inspect one of their pumps when its performance decreased.

“In order to make the visit possible, we followed legal procedures to quarantine prior to the visit on site; applying for the permit and submitting all the requirements,” Cristian says. “The maintenance and process staff at this customer site were very grateful that we agreed to visit them and went through the government process to comply with Covid prevention regulations. In this particular case, the Superintendent went through all the steps to make sure we could get permission to be on site. We inspected the pumps that they were able to get out of the towers and bring to the workshop.”

During this visit, Cristian and his team found other pumps in the towers that the

Absorption tower pump shows no evidence of high acid corrosion from blocked suction strainer.

staff at the customer’s site could not bring to the workshop for inspection. The team suited up with appropriate PPE, went inside the tower, and realized that the suction strainer was blocked with ceramic fragments, resulting in starvation for one of the pumps. The team advised how this problem could be solved without buying unnecessary parts by focusing on the root cause. The customer was very thankful that Weir Minerals was willing to accommodate their request and provide a solution.

The maintenance superintendent at the site said, “Oftentimes, salespeople from other suppliers come and try to sell us their product even if there is no true need and we are misguided. We have to allocate our budget carefully and your honesty proves to us that your company has ethical professionals genuinely interested in helping us be cost effective and solve our problems.”

As employees started visiting customer sites under special requirements, it was refreshing that we could get to the customers who we struggled to reach via video conference. A smelter in Mexico has a policy that restricted the use of computers and cell phones except for a few key personnel. When we met with the Maintenance Manager at the site, we discussed 13 maintenance and process challenges and a solution for each one. We discovered why one of the pumps was drawing more amperage that eventually caused a process disruption when the motor breakers turned off. We were able to identify the pump and while it was almost identical to one of the pumps on another line (only ¼” difference on the impeller trim), we advised the customer not to use those pumps as the slightly smaller impeller would overload the pump’s motor.

The pumps were not identical as the operator had assumed.

On another visit, we went to a sulfur chemicals plant in Mexico and met the newly hired Maintenance Superintendent. After the site visit, our Weir Minerals product manager in Mexico coordinated an online training in Spanish to familiarize the customer with the sulfuric acid nuances when using vertical pumps. The Maintenance Superintendent was very pleased to learn the capabilities Weir Minerals could provide for Lewis® pumps per the factory protocol.

“This plant used to have people that had decades of experience with Lewis pumps and they have all retired,” the Maintenance Superintendent said. “We find ourselves in a situation where the knowledge was not passed on and this reaching out from the Lewis representative and factory is of extreme relevance to our team and very much appreciated.”

The General Director expressed his satisfaction with the reliability of the pumps; the role they play in maximizing uptime for their operation; and why this knowledge is of extreme importance for the recently hired maintenance staff.

Shield was removed from roller bearing in a failed maintenance attempt from third-party shop.

A recent inquiry was sent to one of the Weir Minerals sales engineers in Mexico for a plant that had been experiencing short life for the roller bearing. The Weir Minerals team had a video conference with the customer and discovered that the repair shop removed the shields from the roller bearing in an attempt to grease the bearings. This is not standard practice and is the main reason for the shortened life of the bearings.

Weir Minerals also found that the customer obtained the bearing lock nut and washer from a third-party and did not use OEM spares. We were able to provide the solution and offer repairs and other services through one of our local service centers.

As the world evolves and acid plant knowledge diminishes with staff retiring, we need to use technology even more to exchange information, communicate, and solve problems for our customers. The Covid-19 pandemic has pushed us all to become more creative in working around physical limitations. The world will keep getting smaller as we bridge the physical and knowledge gaps with technology. Our business, like many others, has embraced this form of conducting business so we can be available anytime, anywhere.

Founded in 1871, The Weir Group PLC is a premium mining technology business whose purpose is to make customers’ operations more sustainable and efficient.

The Group is ideally positioned to benefit from structural trends that support longterm demand for its technology including the need for more essential metals to support economic development and carbon transition. Weir’s highly engineered technology enables these critical resources to be produced with less energy, water, and waste - reducing customers’ total cost of ownership. The Group has 13,000 employees in over 60 countries.

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Department

lessons learned: Case histories from the sulfuric acid industry

Hydrogen-generation and ignition in sulfuric acid plants By: Chris Salgado & Walter Weiss, DuPont Clean Technologies

Hydrogen generation and ignition in sulfuric acid plants is an old and well discussed topic, but as we turn over industry personnel, it is advisable to keep it in front of experienced plant operators as well as fresh faces for whom it may be new material. This article offers a good general overview.

Hydrogen formation

Hydrogen forms by way of the following overall chemical reaction:

Fe + H2SO4  FeSO4 + H2

This reaction involves the exchange of electrons which the iron loses and the hydrogen gains. This type of reaction is called an electrochemical reaction and can be described in part by its two half-cell reactions involving the electron transfer as follows: Fe  Fe++ + 2e− 2H+ + 2e−  H2 These equations balance both in terms of mass and electric charge. Neither mass nor energy is being created nor destroyed.

The iron oxidation reaction (loss of electrons) occurs at the metal surface, the anode, i.e. where the acid comes into contact with iron, nickel, or chromium equipment. The hydrogen reduction reaction occurs at the cathode, which, in the case of a sulfuric acid plant, is in the bulk solution.

It can be shown in simple form using the classical electrochemical cell sketch in Fig. 1. The conductivity of the solution allows the transfer of electrons to occur more willingly.

The higher the acid conductivity (i.e. the weaker the acid strength) the more rapidly this reaction can proceed.

Sulfuric acid plants are comprised primarily of various steels in the strong acid system, so iron is a necessity. Acid

anode (positive) oxidation electron loss X- X+e

cathode (negative)

anions (negative) cations (positive)

reduction electron gain M++ e M

electrolyte Fig. 1: Simplified sketch of electron exchange involved in hydrogen formation in a sulfuric acid plant.

condensation or maintenance of the right acid concentration in the sulfuric acid plant environment is governed by the plant design and controlled during operation to minimize the risk of iron (or nickel or chromium) corrosion and resulting hydrogen evolution. Yet there are certain baseline levels of corrosion and hence baseline levels of hydrogen evolution that occur on a continuous basis. With good concentration control, this level of hydrogen generaPAGE 16

tion vis-a-vis the gas flowrate is almost undetectable. Most plant operators are not aware that it is present.

The impact of process technology changes

The relative surface area of steel within an acid plant has increased over time with advances in the process technology. Introduction of new flow schemes and new equipment designs has provided high points where the hydrogen may collect if not continuously removed. These changes over the last fifty years have generated a relatively new set of risk concerns and requirements for operator attention.

As noted, corrosion in sulfuric acid plants generates hydrogen. Contact of metal surfaces with weak acid can increase corrosion rates of these metals by several orders of magnitude. As corrosion rates rise, hydrogen generation rates also increase. Over time, hydrogen forms gas bubbles in the acid. The movement of gas bubbles flowing through the acid can disturb the passive oxide or sulfate film that builds up on surfaces containing sulfuric acid, in turn further increasing corrosion rates.

Limiting corrosion

Many common materials used in acid plants cause only acceptable corrosion rates within relatively small concentration ranges and temperature ranges. Acid velocity may also have an effect. Equipment and piping must be kept within their prescribed operating windows to keep corrosion rates low. It is critical to monitor and maintain appropriate instrumentation for leak detection around equipment such as acid coolers that have water and acid on opposing sides of metal tubes. Response to acid cooler leaks must be swift to minimize equipment damage and hydrogen generation. Not only will the water rapidly dilute acid outside of the desired concentration range for the acid cooler materials, but additional heat will also be generated.

Acid dilution produces heat, and corrosion rates increase with rises in acid temperature. Corrosion rates therefore intensify dramatically during an acid cooler leak.

The same can be said for loss of acid system concentration control–via control loop failure or from an upstream steam system leak. As in the cooler leak example described earlier, the correct response includes quick detection and (1) rapid separation of the water source from the acid as well as (2) a quick de-inventory of the acid plant equipment. Once the weaker acid is removed from the system, and the system is re-inventoried with circulating strong acid, the corrosion rate subsides, and the amount of hydrogen generation returns to more normal levels.

Preventing hydrogen ignition

The elements needed for a fire are fuel, an oxidant, and an ignition source. The elements needed for an explosion are the same as those needed for a fire, but the fuel and oxidant must be mixed and located in a confined space. For hydrogen to ignite at its lower explosive limit (LEL), the energy required is very low–almost undetectable.

Hydrogen is a very effective fuel and is extremely buoyant and diffusive. Hydrogen will normally flow through an acid plant with the bulk gas and be carried out

of the stack in low concentration levels. But in a stagnant plant, or a plant with low air movement, hydrogen can accumulate in high points, such as in the tops of acid towers. Because hydrogen is diffusive, it mixes well with process gas which contains oxygen. Even normal process gases such as NO2, NO, and SO2 can participate in the reaction–reducing the LEL and increasing the energy release.

Once hydrogen builds up to a value exceeding its lower explosive limit of 4% (or less), an ignition source will start a fire. If these elements are located within a confined space, an ignition source will cause an explosion. There are many confined spaces within an acid plant.

The key point is worth repeating: operation of the acid plant’s main compressor will help to reduce hydrogen concentrations and minimize the confined space risk factor.

However, if the main compressor is shut down by either intent or by interlock, the risk of fire and explosion can increase dramatically. It should be stressed once again that maintaining the air flow to purge the plant is key–bypassing and overriding interlocks if necessary.

It is also worth noting that in the last decade or so, there have been an average of one or two hydrogen explosion incidents per year, mostly or almost entirely once the plant has been shut down. The energy release even at LEL concentrations is adequate to significantly damage equipment, cause extensive down time, and incur hefty repair costs. And, most importantly, these incidents can put personnel in harm’s way.

Purging the plant prior to entering a shutdown will help flush hydrogen out of the plant. Installing high point vents in accessible locations and opening those vents after purging the plant will help release hydrogen that can continue to form. Use of automated valves is recommended to speed response time and to separate workers opening the valves from the explosion potential. Isolating equipment, draining acid and water from equipment, and rapidly reacting to concentration or temperature upsets can help minimize hydrogen generation. In addition, ensuring there are effective concentration controls, dilution water interlocks, and process alarms will help reduce risk of a hydrogen incident.

Conclusion

Facilities need to take steps to prevent hydrogen incidents: develop and drill emergency procedures, conduct operator training focusing on hydrogen awareness, and consider hydrogen for general work or hot work permitting to minimize hydrogen risks.

Other steps plants can take include preventing equipment failures by implementing a mechanical integrity program, conducting routine turnaround inspections and equipment repairs, replacing equipment prior to failures, and carefully monitoring process conditions. In other words, the aim is to prevent leaks from occurring in the first place.

Safely starting up, operating, shutting down, and maintaining sulfuric acid plants are thus the keys to minimizing the risk of an incident caused by the presence of hydrogen.

For more information, visit cleantechnologies.dupont. com or email Chris Salgado at Christopher.Salgado@ dupont.com. q Sulfuric Acid Today • Fall/Winter 2021

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Remote controlled robots clean tanks safely and efficiently

For decades, traditional industrial tank cleaning methods often included 100% confined space entry that was unsafe, very inefficient, and often had unpredictable results. Even within the past five years, tank cleaning in the Gulf Coast region would have involved personnel in orange jump suits and helmets with lights and bulky PPE waiting for the atmosphere of the tank to be tested and approved prior to entry. However, with new robotic technology, that approach has changed allowing the oil and gas industry to reduce, or, in most cases, completely eliminate human entry while providing superior cleaning in less time at lower cost.

Driven to improve safety, quality, and efficiency, Ecorobotics developed a Robotic Cleaning System (RCS). The system was designed, engineered, and built in-house after 10 years of research and development. Ecorobotics RCS systems can safely and remotely remove hazardous and non-hazardous materials from indus-

Robot crawlers fitted with vacuum or articulating arm sub for conventional labor inside closed spaces.

trial containment such as above ground storage tanks, piping, sumps, ponds, and culvert/ditches. The RCS requires fewer

people on site and virtually eliminates the

need for confined space entry or additional equipment for the bulk removal process.

The Ecorobotics RCS maneuvers by

using a hydraulically driven track system

and can be equipped with either a vacuum

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attachment or an articulating robotic arm that can spray high pressure water or other cleaning fluids as dictated by the project.

The crawler employs an all-hydraulic system for operation, allowing for the cleaning process to proceed in an elevated LEL environment.

Recently, Ecorobotics performed a project for a fertilizer producer located in the Southeast United States. The project scope was to remove phosphoric acid sludge safely and efficiently. Initially, a manway cannon robot, also known as the Viper Cannon, was affixed to the tank manway flange on the roof so that the walls of the tank could be washed without confined space entry. This technology utilized a

“ “Ecorobotics RCS

systems can safely and remotely remove hazardous and nonhazardous materials from industrial containment such as above ground storage tanks, piping, sumps, ponds, and culvert/ ditches.”

”

Manually pushing material to vacuum (above) takes longer than vacuuming material directly.

remotely-operated high-pressure directed flow for cleaning. This portion of the project took approximately 3 days. Next, an H Series robotic crawler with an articulating arm attachment was inserted through the ground level manway to clean and remove the majority of the extremely hard phosphoric acid solids and liquids from the tank. A 20,000 psi pump and nozzle were used to break up the material. The bulk removal process took approximately 41 days. At the request of the client, on the last shift of the project, confined space entry was made to perform a final rinse.

The entire project was concluded in only 44 days with a total of 3,813 bbl (26 bbl/ hr) of material removed.

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Feature

Planning for outage ventilation

By: Patrick Ferguson, Technical Project Manager, VIP International Inc.

“Let’s get an air mover on it.” This is a phrase we have all heard time and again during outages. Process-related gases have always presented challenges to operators and maintenance teams alike. They can wreak havoc on outage schedules or worse, put workers and equipment at risk.

Many factors contribute to the successful ventilation of a work area, particularly when working in confined spaces.

The unique configurations of plant interiors can turn what seems like an easy solution into a complex undertaking. It is important that the proper steps are taken to ensure the safety of workers, keep equipment in operation, and minimize disruption to outage schedules.

When planning for outage ventilation, potential process gasses must be identified and communicated to affected work groups. Sulfur dioxide and sulfur trioxide are the obvious offenders in the process, but gases such as NOx may be present due to operating conditions or byproducts of sulfur, ore, spent sulfuric acid, or weak sulfuric acid. Gases that could be introduced to the space should be analyzed as well. When hot work is performed within a confined space, toxic gases from fluxes or rod coatings can affect the air quality. Hexavalent chromium can also become a hazard depending on the hot work being performed. Recently, industry emphasis has been put on hydrogen gas formation and its risks throughout the shutdown and outage. Knowing the characteristics of these gases will assist in the creation of a ventilation plan and the implementation of respiratory protection for potentially affected workers.

Properly ventilating a work area requires a detailed assessment with calculations. Some confined spaces present challenges due to their size, shape, and internal configuration. Initially, the volume of the space needs to be calculated. Prints or drawings of vessels can provide a basis to get some initial measurements, but they need to be verified.

Although the size of the space does not dictate the types of ventilation needed, it is necessary to calculate the air changes per hour (ACH). ACH is how many times per hour the air is completely replaced in the confined space. ACH numbers vary based on national, state, and local requirements. If the ACH is not a requirement, it should still be established based on the severity of toxics present. Once the volume and ACH are determined, they can be multiplied then divided by 60 minutes to calculate the velocity needed to replace the air.

Ventilation plans are not necessarily interchangeable when moving from one vessel to another. Oddly shaped or configured spaces may require additional airflow capacity or duct work to get the proper exchange rate. A standard vertical vessel without internals can be ventilated easily using the decontamination method where air is pushed in through the bottom and out of the top. If a top entry is required to perform work, the tunneling method can be used where a blower is installed on a bottom manway and ambient air is naturally brought in through a top manway. Horizontal vessels such as certain pump tank designs are more likely to require the use of ducting for proper air flow. The internals of towers, exchangers, economizers, and converters will greatly influence the air flow needed for ACH numbers. If additional manways are open to atmosphere, a short circuit can occur and reduce air flow. The angles of ducts PAGE 20

Decontamination: Blowing air in from a bottom manway and out through a top manway can maximize air changes.

Tunneling: Tunneling allows for unimpeded access to a top entry where only one manway is available.

Short Circuit: Depending on the location, opening additional manways can cause diminished air changes and potentially trap gases.

must also be considered as multiple bends can lower effective blower capacities. Additional blowers can be used in unison to provide the increased capacity if needed. An important point to remember is that any equipment used at the manway should not impede access to and egress from the confined space in the event a rescue is required.

Tailoring equipment needs for the duration of an outage is essential to preventing delays. Establishing a plot plan of power sources and blowers needed will increase efficiency and ensure that no tasks are overlooked. If an electrical source is unavailable, the use of portable generators may be necessary as long as they are positioned where engine exhaust cannot affect the work area. Pneumatic blowers are also an option when power sources are limited.

Electrically powered AC units are an effective way to keep temperatures low in the confined space while still providing the proper air flow. However, if the entry point is elevated or space is limited, portable fans may be more practical.

Radial fans are compact and can move more air in a circular motion before pushing it outward. Ducts should match the blower application and should be limited in length so as not to reduce the required air flow.

There are additional considerations that can assist in the proper ventilation of process vessels during outages. Allowing operations enough time to properly blow through the system during cooldown can greatly reduce or eliminate the presence of sulfur dioxide and sulfur trioxide gases. Assessing high points and ensuring that any engineered relief valves are in the open position can prevent hydrogen gas pockets from forming due to weak acid or iron oxide formation. Quickly removing sulfates can reduce the presence of NOx under certain conditions. Isolation and blinding procedures can also contribute if there is a known contamination source that can be separated from the work area.

Even with the preparation and execution of a ventilation plan, confined space air monitoring and proper respiratory protection must be assessed and implemented. Air monitoring is a requirement that confirms the ventilation plan is working. If ventilation equipment or power fails during confined space entry, air monitoring can provide a warning to the affected workers to exit the confined space safely. Potential toxics and their concentrations will dictate respiratory protection requirements. Workers must be trained on the potential effects of gases, certified to don the required respirator, and understand the procedures to follow should levels become elevated. Ultimately, respiratory protection is a redundancy needed to protect workers from the unknowns of gas formation.

Ventilation remains a vital component to the safety of outage work. Developing and implementing ventilation plans will reduce or eliminate risks associated with process gases. Arranging for reliable equipment and power sources ensures that work can continue safely and uninterrupted.

Air monitoring confirms that ventilation plans are successful and alerts workers of any changes to the atmospheres within confined spaces. While these steps are not as simple as “getting an air mover on it,” they serve as a fundamental reminder that we must follow through on our responsibility to protect workers.

For more information, please visit www.vipinc.com. q Sulfuric Acid Today • Fall/Winter 2021

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Feature

Wet electrostatic precipitators for superior sulfuric acid gas and mist cleaning

By: Gary Siegel, Marketing Director, Beltran Technologies Inc.

A sulfuric acid plant that is downstream from any one of a number of operations, such as metallurigical smelters and refineries, petrochemical operations, natural gas processing facilities, spent acid regenerating plants, electric generating units, municipal waste incinerators, and ore mining is not only practicable but also highly profitable.

This versatile mineral acid is both the world’s most widely used chemical, and the one with the highest production volume. Its use as both a primary and intermediate raw material spans hundreds of industrial processes, especially agricultural fertilizer manufacturing, which consumes 70 percent of H2SO4 production.

This application alone may continue to fuel a vigorous global trade in this chemical.

Sulfur provides both a direct nutritive value for plants, as well as an indirect value as a soil amendment. It also facilitates a plant’s use of the three other major nutrients: nitrogen, phosphorus, and potassium. Growth in the fertilizer industry, and consequently in the global sulfuric acid trade, is expected to be driven due to the need for more farm land for developing countries as their populations expand.

As global trade in sulfuric acid accelerates, acid plant operators will be under increasingly intense competition to supply the purest, highest quality product. At the same time, operators must remain price competitive by achieving maximum cost efficiency as they maintain these high levels of purity.

To remain competitive in price and quality, an efficient sulfuric acid manufacturing process requires the maximum possible removal from input gas streams of fine particulates, acid mists, condens-

Doe Run’s Peru operation equipped with Beltran’s WESP.

In Zambia, Mopani Copper Mines’ WESP unit from Beltran Technologies.

able organic compounds, and other contaminants. This is necessary for protecting downstream components such as catalyst beds from corrosion, fouling, and plugging, as well as for preventing the formation of a “black” or contaminated acid endproduct. Proper gas cleaning also results in lower costs for maintenance, operations, and equipment replacement.

Wet electrostatic precipitators (WESPs) can vary greatly in design, materials, gas flow rates, durability, and collection efficiency. It is thus important for engineers to recognize the key differences among these various systems.

Beltran Technologies’ advanced WESPs are designed around a multistage system of ionizing rods with star-shaped discharge points, enclosed within square or hexagonal tubes which are lined with grounded collection surfaces. The unique electrode geometry generates a corona field 4-5 times stronger than that of ordinary wet or dry ESPs. The multistage charging configuration also avoids corona quenching due to high particle densities, and assures maximum corona field strength with a minimum of energy load.

As flue gas travels through the tubular array, these intense corona fields induce

Beltran WESP installation at Anglo Gold’s facility in Brazil.

PAGE 22

a negative charge, propelling even submicron-size particulates and acid mists toward the collection surfaces, where they adhere as cleaned gas is passed through.

The surfaces are cleansed of residues by recirculating water sprays. A heated purgeair stream should be used to keep the high-voltage insulators dry, reducing maintenance costs. Since fine particles have little significant mass, they generally pass through scrubbers and other devices, but are captured with remarkable efficiency by advanced Beltran WESP equipment.

The cool, saturated environment in the WESP is highly effective on condensable or oily compounds, which can elude conventional equipment. The continuous aqueous flushing process prevents re-entrainment of particles, sticky residue buildups, and particle resistivity. By eliminating the need for mechanical or acoustical rappers, the cleansing system also minimizes energy costs.

With very little pressure drop through the WESP, gas velocities can be extremely high, boosting efficiency. Plant engineers can use smaller-scale, less costly equipment and still achieve superior collection efficiencies. Other critical features to look for in WESP equipment are sophisticated electronic controls linked to a close-coupled gas flow management system. These components can squeeze even more efficiency out of the system by optimizing such operating parameters as gas velocity, saturation, temperature, corona intensity, etc.

Forward-thinking industrial plant operators around the world constantly seek out and deploy more advanced gas cleaning technologies throughout their enterprises, not only to stay ahead of the regulatory compliance curve, but also to achieve superior operating performance and to control maintenance and other costs in a competitive marketplace. In this context, the role of wet electrostatic precipitators should continue to grow as an essential primary or adjunct gas treatment option.

For more information, contact Beltran Technologies, Inc., at (718) 338-3311 or info@ beltrantechnologies.com;or visit the company website at www.beltrantechnologies.com. q Sulfuric Acid Today • Fall/Winter 2021

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Feature

Acid plant debottlenecking strategies By: Guy Cooper, P. Eng.; Dr. Andres Mahecha-Botero, P. Eng.; Dr. Werner Vorster, P. Eng.; Neal Londry, E.I.T.; NORAM Engineering and Constructors Ltd., Vancouver, Canada.

Take advantage of your assets

NORAM receives many requests for strategies to increase the capacity of an acid plant. Each plant has a unique set of debottlenecking solutions which can result in capacity increases between 10-30% or even higher. Compared to the cost of a new acid plant, a plant upgrade taking maximum advantage of existing assets is a much more economical approach. And if equipment needs to be replaced for maintenance reasons, so much the better, because the new equipment can be sized for the target capacity.

Play to your (SO2) strengths

One of the first things we ask of a client who is looking for more capacity is to provide us with the current operating data, including SO2 concentrations. A plant operating with an SO2 strength to the first converter pass of, say, 10%, could achieve a 15% increase in capacity by increasing the gas strength to 11.5% SO2.

Of course, emissions and heat exchange equipment will need to be assessed and may need upgrades/replacement. Cesiumpromoted and recently introduced highactivity vanadium catalysts make it possible to accommodate increased SO2 loadings within the existing converter.

Heat removal from the sulfuric acid loop can be handled with acid side upgrades.

More on that later.

Checking the pressure (drops)

We also ask for recent pressure surveys. Routine pressure surveys (say, monthly) are one of the best ways to track plant performance and equipment condition. Typically, measurements are taken across all gas-side equipment with a digital manometer and recorded with the production rate, blower rate/rpm, and the SO2 strength. In one plant, we found an extremely high pressure drop across a cold gas exchanger due to fouling and the design. A replacement cold exchanger with a hot sweep feature (see Fig. 1) designed for low pressure drop contributed to that plant achieving and maintaining a 20% increase in capacity. In another plant, we identified high pressure drops in the towers and addressed this by upgrading to a low-pressure drop packing (see Fig. 2).

Replacing high pressure drop equipment, even if more capacity is not immediately required, will often improve overall plant performance and lower blower energy costs.

PAGE 24

Fig. 2: NORAM HP™ Low Pressure Drop Saddle.

Metallurgical acid plant opportunities

Temperature limits for catalysts restrict SO2 concentration to the first pass to a maximum of about 12% with standard catalyst, and 13-14% with cesiumpromoted catalyst operating at a lower inlet gas temperature. Smelters with oxygen enrichment may produce an SO2 gas with up to 30% strength prior to air dilution upstream of the acid plant. NORAM has designed pre-converter systems for such plants, which take a portion of the high strength gas flow, dilute it, then convert two thirds of the SO2 to SO3 which is then removed as acid. The low-concentration SO2 residue gas is mixed with the highstrength gas upstream of the existing acid plant. The preconverter system uses standard processing steps found in every acid plant, including a converter, a gasto-gas heat exchanger, and an absorbing tower. NORAM has designed pre-converter systems to increase capacity by 20-35%.

Fig. 1: NORAM Cold Exchanger with Hot Sweep.

Blower enhancements

One may be tempted to go out and purchase a bigger blower to increase gas flow through the plant. A word of caution here: pressure drop increases with the square of the flow. So a 20% increase in flow results in a 44% increase in pressure drop corresponding to much larger energy requirements. A large pressure increase may cause mechanical challenges with downstream equipment, in addition to the significant price tag for a full-flow, highhead 200” W.C. (5,000 mm) blower and drivers.

However, there are some blower techniques that we use for modest increases in flow and capacity. For a sulfur burning plant with the blower taking suction on the dry tower, rerouting some ducting can allow the blower to take suction on the air filter and then discharge the air into the dry tower. This arrangement has the advantage of cooler air going into the blower, allowing more air flow for the same horsepower and an increased compression ratio (discharge/

suction pressure), which also improves performance. Flow and corresponding capacity increase of 3-7% are possible for this ducting reconfiguration. There is a slight loss of energy efficiency per ton of sulfur burned because the blower’s heat of compression now is removed by the dry tower acid cooler instead of the waste heat boiler, but the increased production actually results in a net increase in steam produced compared to that produced before the upgrade.

Booster blowers designed for full gas flow and low head, less than 50” W.C. (1250 mm), are sometimes used for increased capacity by supplementing a main blower.

They can be located either downstream of an interpass tower (stiffening of the candle housing shell may be necessary) or take suction on the air filter and supplement a blower taking suction on the dry tower. The increased capacity offsets the increased energy operating cost of a second blower.

High pressure drop sulfur furnace and boiler?

For plants where the sulfur furnace and boiler experience a high pressure drop, we have the solution for you: A furnace and boiler bypass system. With this ducting arrangement, a slip stream of cold air bypasses the sulfur furnace (increasing the gas strength and furnace temperature), mixes with the hot furnace gas that bypasses the waste heat boiler, and combines with the main process stream downstream of the boiler. A schematic is shown in Fig. 3.

This simple arrangement gives several benefits. First off, there is a reduced pressure drop which varies to the second power with flow. For example, a 10% bypass results in a 21% reduction in the total furnace/blower pressure drop. If you have a total furnace and boiler pressure drop of 20” W.C. (500 mm), there would be a pressure reduction of 4.2” W.C. (105 mm) for the 10% bypass. For a 2,400 TPD acid plant, this could add 35 TPD of production.

The reduced flow to the sulfur furnaces increases the residence time, which improves sulfur combustion and reduces the chances of uncombusted sulfur. The higher temperature improves the thermal driving force (LMTD) of the boiler, resulting in better heat transfer. The furnace refractory needs to be checked that it can accommodate the higher furnace temperatures.

And as a final benefit, this arrangement may permit replacement of the maintenance-prone jug valve controlling the hot furnace gas split with a stainlessSulfuric Acid Today • Fall/Winter 2021

Feature

steel damper controlling a much cooler air/furnace gas stream.

Upgrades to the acid system

With an increase in gas flow to the acid towers, more acid flow will often be required, especially for the interpass tower. An increased flow will keep the acid concentration and the acid temperature at the bottom of the tower in the proper range. The good news is that acid side upgrades are relatively inexpensive compared to replacing gas side equipment. Changes here depend on the amount of capacity increase, but can range from simply installing a larger pump impeller to replacing an acid cooler, acid pump, and acid piping.

A new acid distributor may be required for the higher acid flow and if there are blanks on the candle tubesheet, a few more candles may be added to limit pressure drop increase with the higher gas flow. Fortunately, Brownian diffusion candles operate in the laminar flow range and pressure drop only increases linearly with flow. As mentioned earlier, consider low-pressure drop packing so that increases in gas flow do not result in higher tower pressure drops.

Your mileage may vary

How much of a capacity increase makes sense for your plant? That raises another question: How much do you plan to spend? For a plant study, we rank the cost of each upgrade option versus the incremental capacity increase,

Fig. 3: Schematic of NORAM Furnace Bypass System.

and we compare that to the unit cost of acid produced for a new acid plant.

Your mileage may vary, but we have seen plants increase in capacity by 20-30% economically compared to the capital cost/acid production ($/ton) for a new acid plant.

Older plants may have older high-pressure drop equipment which provides more opportunities for easier savings.

Newer acid plants often have less maintenance downtime and may require less peripheral equipment to be replaced as part of the upgrade.

And if your plant has frequent shutdowns due to ducting leaks, acid piping leaks, and fouled equipment, improving reliability with new equipment can be a simple

way to increase annual acid and steam production. But that is a topic for another day!

NORAM Engineering and Constructors Limited

designs and supplies sulfuric acid plant equipment for improving reliability and capacity. Over the past 30 years,

they have performed over 250 acid plant engineering studies. They offer low-pressure drop cold exchangers with

hot sweep, low-pressure drop packing, and proprietary furnace bypass systems.

For more information, email sulfuric@noram-eng.com;

or contact C. Guy Cooper at gcooper@noram-eng.com or (604) 696-6910. q

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Product News SensoTech’s LiquiSonic® simultaneously monitors gas scrubber liquid and salt in real time

Environmentally harmful, corrosive, or toxic gases are used in many industrial processes. To protect people and the environment, the treatment of these gases is subject to strict regulations, in particular the specific purification criteria a gas scrubber must achieve. Ensuring the complete conversion of toxic components while using scrubbing liquid efficiently is often a challenge for process engineers.

The effectiveness of a gas scrubber depends on the exact dosage of the scrubbing liquid, for example, caustic soda.

To enable an exact determination of the concentration of the scrubbing liquid and the salts, two physical measurands have to be combined. Conventional measuring methods often map only one measurand and neglect the influence of the resulting salts. In addition, in many cases the process is monitored in a very time-consuming manner by sampling and titration. The LiquiSonic® process measuring system analyzes concentrations of both the washing

The controller reliably displays concentrations of both scrubbing liquid and salt content.

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The maintenance-free measuring devices from SensoTech GmbH are very durable and can be easily integrated into the process control system. Automated documentation and various diagnostic tools provide a comprehensive analysis of the process and can be used for further improvements. LiquiSonic® reduces hazards for the environment and employees and ensures efficient, time-saving process analysis.

For three decades, SensoTech GmbH has been involved in the development, manufacture, and sale of inline analysis systems for processes in liquids. Installed worldwide, SensoTech’s high-precision and innovative measuring systems monitor concentrations, compositions, property changes or substance transformations directly in the process. Special calculation methods and highly developed sensor technologies enable reliable and fast measurement results even under difficult process conditions. For more information, visit www. sensotech.com. q

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Sulfuric Acid Today • Fall/Winter 2021

Feature

The latest in sulfuric acid plant process gas dewpoint/moisture leak detection By: Daniel T. Menniti, Director of Business Development, Mississippi Lime/Breen

Since the mid-1980s the sulfuric acid manufacturing industry has desired a maintenance-free, early indication of moisture ingress (most likely from boiler or economizer tube leaks) into their sulfuric acid manufacturing process.

It was understood that if there was moisture present in the process gas, that the acid dew point temperature of the gas would increase. So, it was decided that if one could measure the acid dew point continuously, producers could monitor the trends and an increase of acid dew point would indicate a leak, or moisture ingress into the process gas.

This desire brought about decades of frustration, while the industry trial and errored an acid dew point meter technology through various phases of commercial design.

Finally, after multiple attempts, the industry gave up and the acid dew point meter manufacturer discontinued their product.

In 2016, the industry discovered that there was a second manufacturer of acid dew point technology who had designed a robust system for permanent installation in traditional combustion applications. Breen, part of Mississippi Lime Company, was approached for a solution.

The criteria given were “simple”—survive in a standard acid plant process gas condition, without maintenance or failures for a year, and the industry would regard the product suitable for use in their applications. Responding to the request from the industry, Breen and the sulfuric acid industry collaborated to develop a commercially available permanently installed sulfuric “acid dew point” monitor.

point with the Breen probe had similar short term operating life and considerable maintenance requirements that made the use of traditional continuous acid dew point monitoring a failure in the first three months of development.

After discussion with industry experts, Breen determined that to keep the sensor free of process condensables for the long term and provide moisture leak detection, the probe would have to operate “above dew point cycle.” The above dew point cycle would allow the probe to operate in the duct at a temperature higher than the process gas dew point, but low enough to detect an increase, or step change, in process gas dew point. The commercial design for the Breen-SA Probe can be seen in Fig. 1.

The problem

Fig. 1: Breen-SA Probe for sulfuric acid manufacturing plants.

The gas laden with SO3 in the process is kept moisture free and the only time moisture gets introduced in the gas is when there is a process upset.

Moisture in the process gas combines with the SO3 which will condense on the process equipment surfaces, and is generally indicative of one of the following conditions, among others: • Drying tower malfunction • Contamination in sulfur feed • Waste heat boiler tube leaks • Economizer tube leaks • Superheater tube leaks • Sulfur gun steam jacket leaks The presence of moisture, and therefore weak acid vapor, in the gas stream is detrimental to equipment health and can cause extreme corrosion. This is a highly undesirable condition and can be potentially hazardous.

A secondary impact of moisture in the process gas can be the formation of hydrogen gas, which can create an explosion hazard [1].

• SO3+H2O  H2SO4 • Fe+H2SO4  FeSO4+H2 The H2 formed in the previous equations can create an explosion hazard in the presence of O2 and an ignition source.

The solution

Since the industry had coined the term “acid dew point” monitor for a leak detection instrument, Breen attempted a probe with the same design criteria as the prior attempt. In short, the continuous measurement of acid dew PAGE 28

Fig. 3: Breen-SA Probe normal cycle and check cycle.

Fig. 4: Leak detection simulation.

Moisture leak detection commercial design

In the Fall of 2018, Breen installed the commercial design into a sulfuric acid plant in California (Fig. 2).

The probe system was allowed to run at the above dew

assumed that the air pressure was not powerful enough to push sufficient air into the duct.

Subsequently, the process engineer put water into the pressure point line and used instrument air to push that water into the duct. The amount of water added was approximately a gallon. At 13:15 we can see the probe immediately responded to the event. It was concluded, with a fairly strong certainty, that the probe is very responsive to even small amounts of moisture.

There were also other minor responses in the previous weeks which were believed to have been caused when other pressure point lines were cleaned out.

Further evidence of response to moisture ingress and leaks

In July 2019, a second and third system were installed in another acid plant in the Western United States. One SA-Probe was installed at the waste heat boiler outlet and one probe at the final economizer exit (Fig. 5).

Fig. 2: Breen SA Probe installation at J.R. Simplot Lathrop plant.

Fig. 5: Breen-SA Probe installation points.

point mode, with weekly “Check Cycle” cooling the sensor to the process gas dew point. The probe cycle and check cycles are shown in Fig. 3.

On January 23, 2019, the plant performed a test to verify that the system would indeed detect a moisture leak. At approximately 10:45 (Fig. 4) we can see a probe response when a pressure point line was cleared out with instrument air. A compressor was then hooked up to the line to pump ambient air into the duct; no response was seen, and it was

During start-up operations, this plant experienced a small leak. In Fig. 6, we can see that the Breen-SA Probe detected the leak when it was still very small at about 05:00 on June 27th. The first plant DCS indication that there was an issue was much later, at about 13:30 on the 27th, when the dilution water flow starts to drop indicating the leak is large enough that less water is needed to maintain the acid concentration balance in the plant.

Clearly, the probe provided almost eight hours advance notice compared to the traditional method of leak detection at the plant.

Continued on page 30

Sulfuric Acid Today • Fall/Winter 2021

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Continued from page 28

the plant hesitated to bring the unit offline until the following traditional methods indicated a leak: 1 Increase in economizer temperature.

2 Condensate in the economizer drains.

3 Indication from the dilution water flow.

detection test with successful results (Fig. 11).

Quoting the customer: “By injecting some small volumes of water into the duct upstream, the probe responded with a spike in conductivity, whereas none of our existing methods picked up such a small ‘slug’ of moisture. This was a great achievement in validating early detection in our plant with the Breen probe, so our next steps would be to look at making the probe a permanent install and integration to our DCS.”

Summary Fig. 6: Leak detection from Breen-SA Probe vs. dilution water flow.

Advanced detection of “undetectable” leaks

In our previous Sulfuric Acid Today editorials, one can view the leak detection capabilities of the system. The early detection of tube leaks was well documented and confirmed by site operations. The same plant referenced earlier had run leak free for almost a year, when, subsequently in June 2020, the Breen SA-Probe system indicated a high process dew point at the waste heat boiler outlet and the economizer outlet systems beginning on June 16th. Multiple dew point measurements were taken to verify the higher dew points.

(See Fig. 7, June 14-June 30)

Fig. 9: Economizer temperature and dilution water flow.

Root cause analysis showed that there was a very small leak in the waste heat boiler shell close to the tube sheet/shell weld. This small leak was most likely the source of the original moisture ingress and all indications show that the SA-Probe responded to the leak as expected. The leak then propagated into the tube sheet, causing the further rise in dew points and conductivity and ultimately (30 days later) condensate was detected in the economizer drain.

The latest data available test results

From May-July, 2021, a new customer had been running their system continuously, first measuring dew point weekly and subsequently shifting to daily measurements, with no sign of probe fouling (Fig. 10).

Subsequently this same plant performed a moisture

Footnotes

[1] Information developed and presented by the Hydrogen Safety Workgroup.

[2] “The Latest in Sulfuric Acid Plant Process Gas Dew Point/Moisture Leak Detection,” Sulfuric Acid Today, Fall/ Winter 2020, Vol. 27, p. 30-32.

Fig. 7: Progressive increase in dew point.

As Fig. 7 shows, from June 16th through July 14th, the dew point temperatures progressed upwards over time.

Finally, around July 16th, the evaporation temperature of the condensate rose above the process gas temperatures and the condensate could not be evaporated from the sensors (Fig. 8).

Having little experience with the Breen technology,

To further support the commercialization of the Breen SA-Probe, the measurement philosophy has been proven effective to detect both large and small moisture leaks, consistently responding to moisture ingress into the process in real-time and demonstrably quicker than traditional methods.

The dew point measurement provides solid trending of the process gas dew point over time as well as in situ verification of sensor function through the automatic and periodic system “check cycle” (dew point measurement).

As of the date of this publication, the Breen SA-Probe, “acid dew point” monitor, has logged over 100,000 hours of operation, with zero failures of the measurement system.

Equally important, there has been zero maintenance hours on any permanently installed system, outside of probe cleaning and re-installation during a scheduled production train turnaround.

Breen attributes this success to the cooperation of the engineers and staff at our various commercial beta sites and the industry acceptance of the “above dew point” measurement logic, which provides for continuous detection of moisture ingress, and periodic measurement of process gas dew point measurement.

For more information, visit www.breenes.com. q

References Fig. 10: Weekly and daily dew point trends.

Daniel T. Menniti, 2020 “Detecting Real-Time Moisture Leaks in Acid Plant Process Gas,” Sulfuric Acid Today, 32-33, Spring/Summer 2020, Vol. 26 No. 1.

Daniel T. Menniti, 2019 “Detecting Moisture Leaks,” Hydrocarbon Engineering, 65-67, January, 2020.

Daniel T. Menniti, 2019 “The Real-Time Measurement of Sulfur Bearing Vaporous Compounds (SO3, Sulfuric Acid, Ammonium Bisulfate) and its Application for Use for Process and Environmental Control,” World Pollution Control Association, 1-2, Summer 2019.

Daniel T. Menniti, 2019 “Process Gas Dew Point/Moisture Leak Detection Measurement System,” Sulfuric Acid Today, 28-29, Fall/Winter, 2019.

Fig. 8: Moisture ingress causing high temperature condensation without evaporation.

PAGE 30

Fig. 11: Small volume water injection into the process gas duct.

Daniel T. Menniti, 2017 “Acid Dew Point Measurement,” Hydrocarbon Engineering, 72-74, October, 2017.

Sulfuric Acid Today • Fall/Winter 2021

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Feature

Clark Solutions: 30 years of continuous innovation By: Bruno Ferraro, Victor Machida, and Nelson Clark

This year Clark Solutions celebrated its 30th anniversary. For three decades, the company has been solving complex problems for our industry, developing new technologies and bringing state-of-the-art solutions to customers.

This article is a retrospective of what we accomplished and contributed, especially for the sulfuric acid market.

Thirty years of continuous innovation

Nelson Clark Engenharia (NC) was founded in 1991 as the exclusive representative in Brazil and Chile of the former Monsanto Enviro-Chem Systems (MECS) for Sulfuric Acid Products and Technologies.

Early in 1992, the company started a successful business relationship with Otto H. York Company Inc., which culminated in 1995 with the licensing to NC of the rights and technology for the manufacture of Otto H. York’s wire mesh mist eliminators. At that time, Clark Solutions was, and still is, one of the very few wire mesh mist eliminator manufacturers in the

Fig. 1: Co-knitted MaxiMesh® model shows the increased surface area.

Fig. 2: MaxiSaddle® (top) and novel MaxiSaddle® BPC ceramic packing.

PAGE 32

Southern hemisphere.

Wire mesh mist eliminators, invented 1959 by Dr. Otto H. York, consist of a mesh formed by extremely fine-knitted metal fabric that is woven, corrugated, and layered in such a way as to provide a very high surface area and high void fraction. This construction enhances mist elimination by inertial impaction and direct interception of droplets, while the gas easily bypasses the wire obstacles imposing low pressure drop.

By the time NC started this manufacture, high-capacity eliminator models were improved by employing geometric changes and multilayer designs with different wire characteristics.

Also, co-knitting wires with extremely fine multi-filaments of fiberglass, PTFE, PET, and other thermoplastic or thermoset polymers radically increased particle collection surface area, which, in turn, provided a similar increase in mist elimination efficiency.

Wire mesh 100% capture efficiency improved from 10-micron particles to 2-micron particles due to these developments.

Today, Clark Solution’s MaxiMesh® is widely used in the sulfuric acid, petroleum, and chemical industries, where its application has provided important lessons learned and technological enhancements to the product’s development.

By 1999, NC Engenharia developed the capacity to manufacture ceramic saddles for absorption and drying towers. Mass transfer media also progressed toward more effective contact area and lower pressure drops, two often competing factors. Due to acid concentrations and temperatures in the process, acid-resistant ceramic packing was most commonly used.

The packing’s geometric complexity was limited to what is mechanically robust and manufacturable in large-scale.

One of the first widely known packing is the cylindric Pall Rings, a geometrical design dating back to 1907. It has seen surface area improvements Lessing Rings and Cross Partition Rings. Other popular ceramic packing is the Berl Saddle from the 1930s, which in the 1950s evolved to saddles, a very successful geometry that became the industry standard for sulfuric acid tower applications. Of course, there were also many improvements to the geometry and ceramic techniques that increased the packed bed efficiency and/or lowered pressure drop.

Using a quality controlled automated process, Clark Solutions produces its standard MaxiSaddles® and its very successful MaxiSaddle® BPC line, which is a more open, low pressure drop ceramic packing.

Developed in 2016 and continually optimized since, this model lowers pressure drop by 35-50% compared to standard saddles used to enhance tower capacity.

In 1997, Koch Industries acquired Otto H. York Company and its mother company Koch-Glitsch and, in 2003, NC formed a joint venture with Koch-Glitsch to manufacture and improve the line of solutions in mist elimination and mass transfer, creating the company Clark-Koch.

At that time, the almost 25 year business relationship with MECS came to an end.

The production of fiberglass Brownian diffusion mist eliminators started in 2005.

These candle-type filters are mostly applied in drying, absorption, and heat recovery towers, due to the massive presence of fine (<1 µm) mist generated by condensation chemical reaction.

To efficiently collect such fine droplets, mechanisms that take advantage of Brownian diffusion phenomena are required. When particles are this small, they follow a random pattern generated by the fluid in which they are suspended.

They follow their path until they collide with the glass fibers from the mist eliminators. The grid that holds the fibers can be made of different materials depending on the application.

Clark’s candle filter manufacturing started with vast accumulated experience

Fig. 5: Largest sulfuric acid towers in Brazil, by Clark Solutions.

and many improvement ideas that have been implemented over the years.

Today, Clark Solutions FiberBed® fully automated manufacturing allows a wide variety of arrangements with unique capabilities such as fiber variable traction (density) control, continuous pressure drop monitoring, and different winding patterns (parallel or angled), along with multiple diameters, heights, and bed thicknesses.

In 2018, Clark Solutions introduced an innovative DrySeal™ device that seals the

Fig. 6: Testing high efficiency trough-type acid distributors.

Fig. 3: FiberBed® products can be customized to meet specific requirements.

Fig. 4: Clark Solutions’ innovative DrySeal™

Fig. 7: SAFEHR BFW® heat recovery system.

Sulfuric Acid Today • Fall/Winter 2021

water allows control over any eventual instrumentation leakage in the closed circuit. The closed circuit also prevents contamination of the steam lines with acid and can be applied to heat not only boiler feed water, but also other plant utilities.

Clark Solutions SAFEHR® technology was also created and developed by 2017.

The system principle shares similar configuration philosophy to SAHFER BFW®, introducing an intermediate cooling system for the hot acid. However, the process takes a different approach, to recover SO3 absorption energy from sulfuric acid to generate steam.

The complete system is basically composed of a two-stage absorbing tower with integrated pump booth, an acid pump, and the SAFEHR® system. The circulating absorption acid is concentrated above 99% and SO3 is admitted in the lower packing deck where the reaction heats the acid to 200-225°C. The gases leaving the lower absorption stage pass through a collector tray and goes to an upper packing deck, reducing gas temperature, absorbing residual SO3, and collecting mist.

The hot concentrated acid in the bottom of the tower is pumped to a heat exchanger in the SAFEHR® circuit which has a refrigerating inert CS fluid in closed loop. The inert fluid circulating in the enclosed system heats boiler feed water or other fluids in this circuit with capacity to generate mid-pressure steam.

Thus, SAFEHR® technology is a new approach to sulfuric acid heat recovery processes that addresses its major concern, which is safety. Hydrogen incident risks may render conventional heat recovery systems unattractive. However, in SAFEHR® operation, any leakage scenario is covered

by the presence of the intermediate inert CS fluid. This operation is considerably safer due to the following fluid characteristics: Inert to acid and water: the fluid is totally inert to acid (in any concentrations) and to water. Also, the fluid is noncorrosive, non-toxic, non-flammable and non-oxidant (so it can be used and stored in non-blanketed environments). In addition, it is non-miscible in water and in acid, allowing proper separation through coalescers with fluid density staying in between water and acid operating temperatures.

With heat recovery safety issues addressed, the plant can provide its best specific steam generation. To illustrate, conventional simple absorption plants have approximately 1.6 ton steam/ton sulphuric acid yield, while a simple absorption with SAFEHR® has a 1.8 ton steam/ton sulphuric acid yield. The first SAFEHR plant has been in service for two years and, despite an occasional hot heat recovery acid leak, the plant has remained in service until the scheduled maintenance turn-round, as promised by the technology.

In recent years, Clark Solutions developed a concept of small modular plants to cater to small sulfuric acid demands.

This required reducing equipment size and quantity. The solution is a simple absorption/scrubbing plant since it eliminates both the gas-gas heat exchangers and the intermediate absorption tower. These are huge and costly equipment, representing a significant portion of the CAPEX and OPEX. The reason being the pressure drop that the gas stream needs to overcome when having both present.

To replace the gas-gas heat exchang-

Conclusion

Fig. 8: This SAFEHR® schematic shows how the heat recovery system performs.

Fig. 9: A SAFEHR system ready to go. ®

Sulfuric Acid Today • Fall/Winter 2021

ers, thermal equipment such as boilers, economizers, and superheaters can be used.

This enables more control and capacity for the steam system.

Considering that there is no intermediate absorption tower, the SO2 oxidation reaction is less favorable to the SO3 side.

Thus, the overall conversion on the catalytic reactor is lower. To compensate for the excess SO2, a tail gas scrubbing system is placed upstream from the stack. The scrubbing solution is selected according to the client’s needs, as it can yield a high value co-product. Here are some examples: • Using ammonia (NH3) to retrieve ammonium sulfate (NH4)2SO4 • Using caustic soda (NaOH) to retrieve sodium sulfite (Na2SO3) and/or bisulfite (NaHSO3) • Using hydrogen peroxide (H2O2) to retrieve diluted sulfuric acid The option of hydrogen peroxide is normally used when no co-product is desired, and the diluted sulfuric acid is sent to the sulfuric acid circulation tank as dilution water. Regenerative SO2 technologies can also be employed when no co-product is needed.

In 2020, Clark Solutions created its first plant with such concepts. This plant is designed as a single absorption plant with an oxygen peroxide tail gas scrubbing system. The plant uses sulfuric acid to extract high value minerals from raw material, and the plant can use calcination exhaust gases as a SO2 source as well as elemental sulfur. It has a max capacity of 135 MTPD for pure sulfur burning and 150 MTPD capacity for sulfur and calcination gas combination. The sulfuric acid plant is equipped with SAFEHR® technology system, validating Clark Solutions patented process in industrial scale.

Fig. 10: Clark Solutions’ first sulfuric acid SAFEHR® plant at Kalium Mining in Dores do Indaiá, Brazil.

As our clients’ requirements and environmental needs increased, we increased efficiency and safety for our previous and new products and projects. Over time, Clark added more products to its portfolio and accumulated more knowledge, to offer better and more innovative solutions to its clients. This close relationship built strong ties with the sulfuric acid market, especially in Brazil. Today, Clark Solutions is known not only for internals, but also for delivering entire towers, piping, and all sorts of engineering projects and services.

Our job is far from over, as investments in research and development are still very strong. All efforts are made to better understand where the process can be optimized and find creative ways to implement these ideas.

For more information, visit www. clarksolutions.com. q PAGE 33

Feature

Fiberbed® without the need for the dangerous and unsafe filling of seal cups.

In 2006, a major step was taken when the first Clark Solutions complete absorption tower was manufactured in Brazil, with all the internals, for application in sulfuric acid plants. Since then, dozens of sulfuric acid process towers and several tower internals were designed, manufactured, and installed, with continuous improvement in materials and design for mist eliminator, liquid distributor, ceramic packing and packing support, corrosion protection, and brick lining technologies.

In 2007, Clark Solutions developed and installed its first trough and downcomer distributor for sulfuric acid. This product was born from vast company experience in mass transfer in large refinery operations where distributions need to be extremely homogeneous. Metal work know-how has evolved within the company, and the benefits of high silicon and other sulfuric acid resistant alloys are present in our products.

In 2015 the joint venture was terminated, and the company name changed to Clark Solutions. In the same year, Clark Solutions worked on a new technology called SAFEHR BFW®. It focused on heat recovery in absorption towers, where normally the SO3 absorption heat reaction is wasted on cooling water. Designed to partially recover this lost heat, SAFEHR BFW® consists of two plate heat exchangers in between a closed water loop, transferring heat from the hot absorption acid in one heat exchanger and heating boiler feedwater in the other heat exchanger, using the closed loop water as medium.

The design increases energy efficiency with limited risk to boiler feed water, which can debottleneck and improve steam generation capacity.

This indirect heating of boiler feed

Department

CONFERENCE PREVIEW

Sulfuric Acid Today to host 2022 Sulfuric Acid Roundtable in Texas COVINGTON, La.—Plans are underway to resume Sulfuric Acid Today magazine’s Sulfuric Acid Roundtable (SAR) technology conference, which will take place April 4-7, 2022 in The Woodlands, near Houston, Texas. The event will be the first in-person roundtable in three years, since SAR 2019 in Orlando. Traditionally held every other year, the 2021 roundtable was cancelled because of the Covid-19 pandemic. For everyone’s safety, SAR 2022 will follow CDC recommendations for proper social distancing during the course of the two-and-a-half day meeting.

As in past years, the roundtable brings sulfuric acid producers and leading technology companies together to discuss the best practices for maintenance, operations, pro-

duction, and safety. The event includes: • A keynote address, “Sulfuric acid market review and outlook for 2022,” presented by Fiona Boyd of Acuity Commodities.

• Informative technical papers from the industry’s top technology and service companies.

• Several panel discussions for plant personnel to share knowledge or lessons learned about many important topics, including: Acid Towers, Acid Resistant Linings/Bricks/ Mortars/Refractory, Converters, Heat Exchangers, Process Gas Monitoring/Analayzers, Sulfur Handling/Storage/Pit Maintenance, and Safety Issues and Incident Reviews.

Participants can also enjoy some rejuvenation time with

two scheduled friendly competitions: a Golf Tournament at The Woodlands Resort and a Shooting Range Tournament at the Saddle River Range in Conroe, Texas. The fun will kick off on Monday, April 4.

As always, there will be plenty of networking opportunities with hospitality receptions and group dinners each evening. The event will wrap up with a bus plant tour of Eco Services’ Houston acid plant.

For plant personnel interested in registering for the event, please visit www.acidroundtable.com. For vendors and technology providers interested in participating, please contact Kathy Hayward at kathy@h2so4today.com or (985) 807-3868. q

Fiona Boyd of Acuity Commodities will kick off the 2022 Sulfuric Acid Roundtable with a keynote address that will focus on the review of the sulfuric acid market and outlook for 2022.

The 2022 Sulfuric Acid Roundtable will consist of several panel discussions for plant personnel to share knowledge or lessons learned with the participants.

The 2022 Sulfuric Acid Roundtable will wrap up with a bus plant tour of Eco Services’ Houston acid plant.

Save the Date!

2022

Sulfuric Acid

R O U N D T A B L E

The 20 Acid R22 Sulfuric oundta ble will of fer :

— Keyno te Addre ss Globa l Sulfuric on the Acid Mark — Produ cin et Discus g Plant Panel sions & Presenta — New T tions ech — Safety nology Develop ments Issues & Incident Reviews

April 4-7, 2022

The Woodlands, Texas (Houston) Sponsored By:

Sulfuric Acid T

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Industry’s Premier Event for Networking & Sharing Best Practices™ Register On-Line Today! www.acidroundtable.com PAGE 34

Sulfuric Acid Today • Fall/Winter 2021