sulfamicacid purification process development using...
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Sulfamic Acid PurificationProcess Developmentusing OLI Flowsheet: ESP
(One reason we model)
Steven GriseThe Chemours Company
OLI Simulation Conference25-26 October, 2016
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We are Chemours and we unleash the power of chemistry, working hand-in-hand with our customers
• Created from DuPont’s Performance Chemicals businesses
• More than two centuries of experience in the chemical industry making us a 200-year-old start-up
• A rich history of innovation and industry firsts
• A market leader in safety and responsible handling of chemicals
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Our Businesses
Market LeaderIn safe production & manufacture of performance chemicals. Combining leading products, applications expertise, and market-shaping chemistryFluoroproducts
TitaniumTechnologies
ChemicalSolutions
#1in market share of fluoropolymers
in global supply capacity of low global warming potential products
#1
brand of TiO2 in the market#1
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Our 2014 Sales
$6.4 Billion
in combined Revenues in
2014 By Region
43%
15%
18%
24%
North America
EMEA
Latin America
Asia Pacific
By Business
36%
46%
18%
Fluoroproducts
Titanium Technologies
Chemical Solutions
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What is Sulfamic Acid ?
• Crystalline, aqueous inorganic strong acid– NH3SO3 or HSO3NH2
• Produced exclusively in Japan and Taiwan– US and Europe plants shut down due to decrease in demand,
production difficulties and problems with disposal of byproducts.
• Primary use as cleaning agent– Excellent for boiler scale.
– Relatively low corrosivity.
• Not specifically toxic– Physiological properties typical of a strong mineral acid.
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How is Sulfamic Acid produced ?
• Strongly exothermic reaction
• Urea + SO3 + H2SO4
• Two step process– Step 1
• NH2CONH2 + SO3 NH2CONHSO3H
• Solvent is Oleum
• Keep temperature low to manage heat and keep conversion low.
– Step 2
• NH2CONHSO3H + H2SO4 2 HSO3NH2 + CO2
• Keep temperature below about 80oC in excess SO3 to minimize impurity formation
• Remove unreacted SO3
• Typical product is ~95% pure (impurities are H2SO4 & NH4HSO4)
– Higher purity obtained via recrystallization
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Why is Chemours Interested ?
• We (as DuPont) were producers in the past
• Chemours was a major manufacturer of H2SO4 and Oleum prior to September 2016.– Business sold to Veolia.
• Is there an opportunity for manufacture of Sulfamic Acid to supply US fracking industry?– Fracking uses Sulfamic as de-scaler and well regenerator.
• Crude 95% product purity is not adequate for application– Some purification would be necessary.
– Look at recrystallization.
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Process Development
• This seemed like a great fit for OLI Flowsheet: ESP
• Fortunate to have been chosen as a Beta tester
• MSE Chemistry model
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OLI Flowsheet: ESP screenshot
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Comparison versus 1958 Patent Example
• US Patent 2,862,790
• Crude feed impurities not quantified in patent. Composition varied to roughly equal NH3/SO4 ratio below.
• Water feed not explicitly defined.
• Crystallizer feed and purge rate fixed.
• Impurity composition agrees well.
• Ratios and production rate agree well– Assumes no product loss through purge (oops)
• All told, agreement is very good !!
Expt'l Model
Crude feed lb/hr 388
NH3SO3 wt% 90 90
H2SO4 wt%10
3.5
NH4HSO4 wt% 6.5
Water feed lb/hr ? 62.9
Crystallizer feed lb/hr 20,800
Crystallizer feed T oC 50
Crystallizer T oC 40
Purge lb/hr 112
Purge H2SO4 conc wt% 12 12.1
Purge NH4HSO4 conc wt% 21.6 22.4
Purge NH4SO3NH2 conc wt% 0 0
Purge NH3SO3 conc wt% 0 (?) 9.2
NH3SO3 Product (Pure) lb/hr 350 339.1
NH3/SO4 ratio mol 0.60 0.61
NH3SO3 Productionlb pure NH3SO3 / 100 Crys Feed
1.68 1.63
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Sulfamic SLE
• Patent is for improved recovery by addition of a base.
• Sulfamic solubility decreases with the addition of NH3.
• Patent claims this addition helps production.
• Note that sulfamic acid solubility changes from about 19 wt% to about 15 wt% with a significant addition of NH3.
• Graph shows results of OLI regression fit.
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OLI Flowsheet: ESP with NH3
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Comparison
• Water feed stated as “unchanged”.
• Crystallizer feed increased slightly with larger crude feed and more recycle.
• Purge rate fixed, but recycle flow did not converge. Fixed recycle ML instead.
• Impurity composition not given in patent; significantly different than previous case.
• Ratios and production rate agree less well
– Assumes no product loss through purge (oops)
• Note patent claim of 60% improvement.– Cannot be explained by solubility graph.
Expt'l Model
Crude feed lb/hr 620
NH3SO3 wt% 90 90
H2SO4 wt%10
3.5
NH4HSO4 wt% 6.5
Water feed lb/hr Same 51.4
Crystallizer feed lb/hr 21039
Crystallizer feed T oC 50
Crystallizer T oC 40
Purge lb/hr 112 210.1
Purge H2SO4 conc wt% ? 0
Purge NH4HSO4 conc wt% ? 31.2
Purge NH4SO3NH2 conc wt% ? 12.2
Purge NH3SO3 conc wt% ? 26.5
NH3SO3 Product (Pure) lb/hr 560 480.3
NH3 feed lb/hr 7.6
NH3/SO4 ratio mol 1.5 1.39
NH3SO3 Productionlb pure NH3SO3 / 100 Crys Feed
2.66 2.28
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What is actually happening ?
• The claim in the patent is that the crystallization is improved with the base.– Presumably through a salting-out effect.
• What actually is happening is that the ammonia complexes with the sulfamate (NH4SO3NH2(aq)) and builds to a new saturation point.
There is very limited dissolution of sulfamic acid in the dissolving tank (~14% dissolves; roughly 79 lb/hr)
• Approximately 2 lb/hr additional sulfamic acid is precipitated in the crystallizer.
• This is a glorified wash step !
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Conclusions and Comments
1. OLI Flowsheet: ESP is a winner ! • Easy to use.
• Very stable.
• Kudos to the development team !
2. We model to gain insight. Sometimes we are surprised.
3. Understanding the chemistry is critical.• Model the process focusing on the electrolytes (using OLI)
• OLI Flowsheet: ESP will be a strong tool in the future
4. By using this modeling approach we have identified a significant opportunity for process simplification and reduced capital investment.
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Chemistry changes life.
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