|18.2.1 Cost Effective Boost of Plant Performance with LEAP5 Catalyst|
Cost Effective Boost of Plant Performance with LEAP5 Catalyst
Mårten Granroth, Haldor Topsoe
The profitability of sulfuric acid production is closely related to the production rates achievable within SO2 emission limits. The optimal operating conditions of a plant depend strongly on the plant configuration, catalyst volumes and catalyst activities, and as SO2 emission limits are tightened, more active sulfuric acid catalysts are required to maintain the desired production rates.
In 2010, Haldor Topsoe launched a completely new and groundbreaking catalyst type, the VK-701 LEAP5™. The further development of the LEAP5™ series for improved activity or for other applications builds on detailed knowledge gained through fundamental studies of the working sulfuric acid catalyst. New results from our advanced in-situ studies will be presented as an example of how fundamental knowledge, such as the dynamics and chemistry of the active melt on the carrier, has enabled us to develop the new VK-711 LEAP5™ catalyst which was launched late 2017. This new catalyst, based on the proven LEAP5™ technology, has been optimized for higher activity at lower temperatures to bring the unprecedented LEAP5™ performance to even more plants. The new catalyst has the potential to help acid plant operators to reduce operational cost, cope with new emission demands, improve productivity and avoid expensive capex projects. In addition to these advantages, the excellent low-temperature activity of the catalyst provides additional plant flexibility and helps to reduce start-up emission peaks.
In this paper, it will also be presented how the new catalyst, as well as existing catalyst technologies, can be applied together with the right strategies to counter more stringent SO2 emission demands, both during steady state and start-up conditions. In addition to meeting stricter SO2 emission demands, the right catalyst and strategies can also be used as a cost effective way to shorten downtime. Finally, industrial data will be included to exemplify how acid plant operators have already utilized catalyst to meet new demands at real life conditions.
|18.2.2 Effective Management and Utilization of Lime Sludge Ponds|
Effective Management and Utilization of Lime Sludge Ponds
Phong Vo - Mosaic Fertilizer, LLC and Rob Werner, P.E. - Ardaman & Associates Inc.
More than one billion tons of phosphogypsum have already been stockpiled in some 40 phosphogypsum stacks” in the United States and, at current production levels, about 40 million tons are added each year. Active phosphogypsum stacks are almost entirely saturated with acidic process water (pH typically between 1.5 and 2.0). As a phosphogypsum stack system reaches its maximum gypsum storage life and transitions into terminal closure phases, hundreds of million gallons of process water must be removed from the system to facilitate closure as required by the Rules. Approximately half of the acidic pore water entrained within gypsum stacks, or 30 billion gallons, is in “temporary storage” as it will eventually drain once the stacks are closed, and the seepage water will then have to be treated prior to discharge. Lime treatment is the most common method employed by the industry.
Conventional lime treatment typically employs a two-stage neutralization process. Stage I treatment consists of lime, CaO, or slaked lime, Ca(OH)2 with process water to elevate the pH to about 5 which results in precipitation of fluoride and other dissolved solids (i.e., metals, radionuclides and some of the phosphate) that settle and form a Stage I sludge. During Stage II treatment, clarified Stage I supernatant is mixed with lime once again to further raise the pH to precipitate phosphorus. Underflow from the Stage II treatment reactor is then routed into a clarifier or settling pond for sedimentation of the Stage II sludge. Stage I treatment generates between 100 and 400 pounds of sludge on a dry weight basis for every 1,000 gallons of process water treated, depending on the TDS of the process water. Stage II treatment normally generates between 100 and 200 pounds of sludge per 1,000 gallons treated.
Lime treatment systems will typically need to be operated at high rates during the stack system closure period and at gradually declining rates throughout the 50-year post closure maintenance period. For a stack system requiring treatment of one billion gallons of process water, approximately 200,000 tons of lime sludge will be generated. In-situ solids contents of 25% and 15% are typical for Stage I sludge and Stage II sludge, respectively. These soft by-product waste materials are typically disposed of in large settling areas which will ultimately have to be closed. Considering the large volumes of acidic process water eventually requiring treatment as part of gypsum stack closures and the associated lime sludge disposal requirements, conventional on-land disposal methodologies need to be optimized the reduce the land area needed for sedimentation ponds and their capping or closure costs. Construction and operation costs associated with building and operating the sludge settling areas, and reclamation costs during abandonment need to be factored in when evaluating sludge management strategies.
Underflow from Stage I and Stage II clarifiers used in the lime treatment process normally contain about 10% and 5% solids, respectively. Typically, lime sludge slurry is pumped and discharged on one side of the pond. Through the clarification process, fine lime sludge particles settle out at the bottom of the pond, and clear water is decant at the opposite end of the pond. Lime sludge ponds are often constructed with multiple compartments and large surface areas large enough to promote effective clarification. In order to maximize storage of lime sludge ponds, operators typically use mechanical equipment such as airboats and/or floating curtains to promote clarification process. The surface area for clarification process is reduced and no longer function, storage capacity of the lime sludge pond is depleted and replaced with a new lime sludge pond.
Double-lime treatment of process water has been ongoing at Mosaic’s Faustina facility in St. James, Louisiana for many years, particularly since termination of phosphoric acid production in 1999. Since that time, about 8 billion gallons of process water has been double-lime treated and the resulting treatment sludge has been stored in the former cooling pond.
Through years of experience, innovations, and team work, a new method of lime sludge management was created by a supervisor employee at Mosaic (Mr. Larry LaBorde). The new method of lime sludge management has been successfully tested and monitored by a team of civil engineers. Following the monitoring and testing periods, the new method of lime sludge management was fully implemented at the Mosaic’s Faustina Gypsum Stack System in Louisiana. As of today, this new method of lime sludge management has allowed Mosaic to continue extending the storage life of the lime sludge pond at Faustina for many years beyond its original 2011 forecasted storage depletion date, and avoided spending over $4 million dollars for construction of additional lime sludge ponds. This method is currently being tested other Mosaic’s facilities in Florida.
The authors will describe the new lime sludge management technique which has been commonly named after the employee as the LaBorde Method of lime sludge management. The authors will also describe testing procedures and engineering analysis to validate the method prior to full application.
|18.2.3 Fuming Acids Storage Tank Cleaning/Decontamination/Inspection Best Practices|
Fuming Acids Storage Tank Cleaning/Decontamination/Inspection Best Practices
Mark Salzbrenner, Veolia
Fuming sulfur-based acids are essential chemicals for today¡¦s society. Hundreds of thousands of tons of these products are safely manufactured, stored and transported each year. If handled properly, they are relatively easy chemicals to transport and store. If not, and they are released to the environment, they can create very visible fumes (white clouds) at low concentrations, resulting in Health, Safety and Environmental issues.
Veolia NA and its predecessor companies have been making sulfuric acid products since 1865. Over these years we have developed processes and procedures to safely clean, decontaminate and inspect sulfuric acid storage tanks and vessels with no or minimal damage to the tanks/vessels. The fuming sulfuric acid grades (sulfur trioxide (SO3), oleums and chlorosulfonic acid) present additional difficulties. These grades can create dense white clouds released to the atmosphere if not handled properly during the storage tank cleaning, decontamination and inspection processes. Improper techniques will also result in increased corrosion, requiring possible repairs to the storage tank.
This session will describe the different techniques that can be used to clean, decontaminate and inspect fuming sulfuric acid storage tanks and vessels. Techniques for each individual tank will differ depending on a number of variables ¡V including, but not limited to: age of tank, tank materials of construction, type of tank, grade of fuming sulfuric acid, time limits for the cleaning/decontamination/inspection process, etc.
The primary techniques for cleaning and decontaminating fuming acid storage tanks and vessels are:
„h Acid Dilution
„h Water Dilution
The advantages and disadvantages of each technique will be reviewed in detail to help attendees select the best techniques for their situation.
Various inspection procedures can also be employed. This talk will concentrate on inspection procedures that meet the NACE (National Association of Corrosion Engineers) SP-029406 standard. SP029406 is the RAGAGEP (Recognized And Generally Accepted Good Engineering Practice) standard observed by OSHA for sulfuric acid storage tank design and inspection.
|18.2.4 Advancements in Modern Sulphuric Acid|
Advancements in Modern Sulphuric Acid
Dirk Scheckrieter, ThyssenKrupp
Sulphur burning sulphuric acid plants and blast furnace coke plants have much in common. New solutions in sulphuric acid plant design have been adopted from coke plant technology.
The link between coke plants and sulphuric acid plants was derived from the production of a very important by-product of coke plants: Ammonium sulphate fertilizer. Ammonium sulphate is produced from ammonia and sulphuric acid. The latter is produced from hydrogen sulphide. Ammonia and hydrogen sulphide are both components of the crude coke oven gas processed in the by-product plant of a coke making plant. tkIS is well known for its coke plant technology and has many references for the dry and wet catalysis of hydrogen sulphide based sulphuric acid plants in the field of coke plant technologies. In the last few years tkIS has adapted its sulphuric acid technology to also address sulphur burning operations.
This modified technology is based on the same design criteria valid for coke plants:
a) Plant operations: 24/7, 365 days per year.
b) High environmental standards to be complied to strictly.
Advantages from this technology include an emission free start-up of as well as a maximized heat recovery ratio for a sulphuric acid plant.
|18.2.5 The Seven Deadly Sins of Mist Eliminator Operation and Maintenance|
The Seven Deadly Sins of Mist Eliminator Operation and Maintenance
Evan Uchaker , MECS/DuPont
Is it an equipment issue? An installation / maintenance issue? An operational issue? When a tower has mist carryover, these are common questions. Is the problem with the mist eliminators themselves? Or is there some other process anomaly or “tower gremlin” that has caused performance to deteriorate?
This paper will examine these questions in depth by exposing and deciphering some of the more common root causes (“sins”) of poor mist eliminator performance, how these conditions can be assessed and tested, and what potential solutions exist. Often the causes of the poor mist eliminator performance can be attributed to one of the “seven deadly sins of mist eliminator operation and maintenance.” Real case studies are presented and reviewed focusing on proper installation, inspection, maintenance, operation, and testing so that mist eliminators achieve satisfactory performance, long service life, and minimum plant downtime with low maintenance costs.
|18.2.6 Mosaic/CanSolv: 5 Years Later|
Mosaic/CanSolv: 5 Years Later
Paolo Olis, The Mosaic Company and Nicolas Edkins Shell Cansolv
As requirements across the world have become more stringent for sulfur dioxide emissions, sulfuric acid plants are faced with increasingly expensive solutions to keep their license to operate. Most additions to aging acid plants over the years have included new catalytic beds with an absorption tower or a tail gas scrubber. With reduced emission targets, additional revamps have become more difficult and expensive to install or more cost intensive in terms of operation. The addition of a regenerable SO2 tail gas scrubbing solution like the Cansolv SO2 Scrubbing System to the portfolio of technologies offers plant managers a solution that can be easily tailored and added on to existing facilities while future proofing emissions at the same time.
The Cansolv SO2 Scrubbing System has been successfully applied to treating sulfuric acid plant tail gas from fertilizer and spent acid recovery applications starting in 2002 and has been proven to be a cost-effective reliable solution with over 15 years of commercialization worldwide in various applications. With performance exceeding expectations, plant operators have controlled SO2 emissions to less than 10 ppmv or roughly 0.3 kg/ton of acid produced. The recovered SO2 is recycled back into the acid plant to maximize sulfuric acid production. With the possibility to easily bolt-on the solution to existing acid plants, the Cansolv SO2 Scrubbing System can provide the answer to both current and possible future environmental specifications while simultaneously decoupling emissions from the upstream unit performance.
This paper discusses a case study at a sulfuric acid production site for a fertilizer plant in Louisiana. The Mosaic Uncle Sam site successfully commissioned and started up the Cansolv unit in 2011and have been operating it ever since. The unit treats upwards of 130,000 N/m3 of tailgas from a single absorption acid plant containing 2,000-3,500 ppmv SO2. The case compares real operating data from a Cansolv unit treating tail gas from the single absorption acid plant versus a conventional double absorption acid plant on the same site. The comparison looks at highlighting the advantages of applying re-generable tail gas solutions and the benefits it can bring to an existing operation.
|18.2.7 Water Dilution Systems for Silicon Alloy Pump Tanks|
Water Dilution Systems for Silicon Alloy Pump Tanks
Henrik Vekselius, Noram
The objectives of this paper are to describe the challenges of using silicon alloy pump tanks in combination with water dilutions systems and discuss solutions to deal with these challenges. Different types of pump tanks as well different configurations of water dilution systems will be described.
Almost all Sulphuric acid plants require water addition to control acid strength. As Sulphuric acid and water do not mix as easily as one might expect. Measures to ensure proper mixing are necessary to avoid generation of weak acid which can rapidly give corrosion damages. The highly exothermic nature of the dilution reaction also needs to be taken into account. Acid concentration and temperature limitations for silicon alloy pump tanks must be observed to ensure a long service life. The process control systems must be designed to keep the conditions in the tank within the required boundaries.
|18.2.8 A Phosphate Pioneer’s Experiences, Contributions, and Good Advice|
A Phosphate Pioneer’s Experiences, Contributions, and Good Advice
Sam Houghtaling offers to present a paper at Clearwater relating decades of pioneering service to the phosphate industry. Sam was a founding member of Central Florida AIChE and helped start the Clearwater Conference – even when it was at Daytona Beach, before it moved to Clearwater.
Sam is always an amusing speaker. He will relate hilarious experiences while serving our industry at home and abroad. He’ll describe trouble-shooting successes that earned bravos from clients and even a tip of the hat from the last Shah of Iran.
Sam will relate his invention of:
• · Wet rock grinding – now common worldwide
• · Conical strainers for phos acid evaporators – now standard worldwide
• · Dual-diameter DAP pre-neutralizer – now standard in most DAP plants
Sam will offer valuable advice on how to treat employees, how to trouble-shoot problems and improve operation in phosphate plants, and how to get along with clients. This will be a presentation to remember!