NITRIC ACID PLANT (63% wt. HNO3) Ammonia-Based Fertilizers

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NITRIC ACID PLANT (63 wt. HNO3)Ammonia-Based
Fertilizers

• University of Illinois at Chicago
• Department of Chemical Engineering
• CHE 397 Senior Design II
• January 24, 2012
• Thomas Calabrese (Team Leader)
• Cory Listner
• Hakan Somuncu (Scribe)
• David Sonna
• Kelly Zenger

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Todays Agenda

• Big Picture Fertilizer Plant
• Supplier
• Customers
• Nitric Acid Plant Design Basis
• Starting Reagents
• Products
• Environmental Concerns
• Process Block Flow Diagram
• General Process Overview
• Catalysts
• Useful Energy Recovery
• Pressure and Temperature Effects
• NOx Emission Control

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BIG PICTURE-FERTILIZER PLANT
Ammonia (Liquid) Supplier (603.5 TPD)
INTERNAL CUSTOMER
AIR (10820 TPD)
2571.2 TPD HNO3 (63 wt)
OUTSIDE CUSTOMERS 717.8 TPD HNO3 (63 wt)
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Design Basis

• Produce 3,289 TPD of 63 wt. nitric acid solution
  (14M)
• Starting Reagents
• Ammonia (NH3) - 603.5 TPD
• Excess Air 10,819.5 TPD
• Excess Oxygen (O2) from Air 2,272.0 TPD
• Products
• 63 wt. Nitric Acid Solution (HNO3) - 3,289.0
  TPD
• Water (H2O) 1,216.9 TPD
• Useful Heat
• Environmental Concerns
• Oxides of Nitrogen (NOx) (lt200 ppm)
• Nitrous Oxide (N2O) (lt200 ppm)

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Catalytic Reactor (Oxidation of NH3)
Ammonia Filtration
Mixing
572 TPD NH3 (g)from Ammonia Plant
NO (g)
1,843 TPDSteamto CHP
Air Filtration
Air Compression
Heat Recovery (Oxidation of NO)
10,322 TPD Air
Atmosphere
Gas Expander
Hot Tail Gas
NO2 (g)
Absorption Column (Formation of HNO3)
Bleacher Column (Strip Dissolved NOx)
Nox Compressor
NOx (g)
607 TPD Process Water
Cold Tail Gas
3,289 TPD 63 wt. HNO3
718 TPD to Market
2,571 TPD to Ammonium Nitrate
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General Process Overview

• Primary Chemical Reactions (Ostwald Process)
• Oxidation of Ammonia to Nitrogen Monoxide4NH3
  (g) 5O2 (g) ? 4NO (g) 6H2O (g)
• Oxidation of Nitric Oxide to Nitrogen Dioxide2NO
  (g) O2 (g) ?? 2NO2 (g)
• Reaction of Nitrogen Dioxide to Nitric Acid3NO2
  (g) H2O (l) ?? 2HNO3 (aq) NO (g)
• Side Chemical Reactions
• Simultaneous to Oxidation of Ammonia 4NH3 (g)
  3O2 (g) ? 2N2 (g) 6H2O (g) 4NH3 (g) 4O2 (g)
  ? 2N2O (g) 6H2O (g)

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Materials of Construction
Material Pros Cons
Steel and aluminum Cheap, can be used at low temperatures At elevated temperatures forms oxides and nitride films on surface of metal.
Stainless Steel Operating performance, less maintenance. Required for elevated temperatures. Corrosion resistant. Higher capital cost compared to basic metals
Hastelloy (Nickel alloy) Highly corrosion resistant. Can be operated at high temperature and high stress More expensive than stainless steel. Degradation due to handling.
Monel (Nickel Alloy) Can be operated at high temperatures. Corrosion resistant Much more expensive than stainless steel
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Energy Recovery Methods

• Heat from Oxidation in Catalytic Reactor
• Heat from Absorption
• Mechanical Energy from Tail Gas Expansion

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Energy Recovery Methods

• Net Energy Exporter
• Oxidation reaction 1,600 Btu/lb of pure nitric
  acid
• Absorption process 370 Btu/lb
• Tail gas turbine 325 Btu/lb (80 of mechanical
  energy used)
• Total 1,955 Btu/lb (967-1,217 Btu/lb at 50-65
  efficiency)
• Little effect from single/dual-pressure and other
  considerations
• Steam (standard)
• Augmented with natural gas at startup
• Combined Heat Power (CHP)
• Generate high pressure steam and run through
  turbine
• Offsets power purchase from the grid

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Which Catalyst?
Platinum-Rhodium Cobalt Oxide (Co3O4)
Cost (/short ton of HNO3 produced) 3 - 4 0.50 - 0.75
Lifespan 3-4 months 12 months
Downtime 4 hours to replace gauze at end of lifespan Remove Rhodium Oxide buildup (every 3-4 weeks) None
Conversion Efficiency 93 - 96 95 - 98
Operating Parameters 24-95 psi, 1490-1724 F 0-95 psi, 1549 F
Use Very common, industry standard New, commercial use
Drawbacks Cost, lifespan, and greater N2O formation Minimal data available, new reactor design, deactivation to CoO
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Why are Pressure and Temperature Important?
Cost Catalyst Life NH3 Oxidation NO Oxidation Absorption of NO2
Low Pressure (0-25 psig) Lowest Cost Shorter than Dual Increased Oxidation Rate Decreased Yield Less Absorption
High Pressure (90-120 psig) Increased Cost Shorter than Dual Reduced Oxidation Rate Increased Yield Improved Absorption
Dual Pressure Highest Capital and Materials Cost Longest Catalyst Life Increased Oxidation Rate, Best Conversion Increased Yield Improved Absorption
Increased Temperature - - Increased Yield Decreased Yield Improved Absorption
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Controlling NOx Release

• Primary Methods-reduce N2O formed during ammonia
  oxidation
• 70-85 efficiency
• Add an empty reaction chamber between the
  catalyst bed and the first heat exchanger
  (increase residence time)
• Modify the catalyst used during the ammonia
  oxidation
• Secondary Methods-reduce N2O formed immediately
  after ammonia oxidation (Selective Catalytic
  Reduction)
• Up to 90 efficiency
• Secondary catalyst is used to promote N2O
  decomposition by increasing the residence time in
  the ammonia burner
• 2N2O (g) ? 2N2 (g) O2 (g)

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Controlling NOx Release

• Tertiary Methods-reduce N2O from or to the tail
  gas (Non-Selective Catalytic Reduction)
• 80-98 efficiency
• A reagent fuel (e.g. H2 from an ammonia plant
  purge) is used over a catalyst to produce N2 and
  water
• Alternatively, following SCR the tail gas is
  mixed with ammonia and reacts over a second
  catalyst bed to give N2 and water

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Thermodynamic Models for HNO3 (63 wt) Plant

• Up-stream of HNO3 (63 wt) Plant
  Soave-Redlich-Kwong (SRK)
• The SRK property method uses the
  Soave-Redlich-Kwong (SRK) cubic equation of state
  for all thermodynamic properties with option to
  improve liquid molar volume
• Mixture Types
• Use the SRK property method for non-polar or
  mildly polar mixtures.
• This property method is particularly suitable in
  the high temperature and high pressure regions
• Range
• It can be expected reasonable results at all
  temperatures and pressures.
• The SRK property method is consistent in the
  critical region.
• Therefore, unlike the activity coefficient
  property methods, it does not exhibit anomalous
  behavior. Results are least accurate in the
  region near the mixture critical point.

• Down-stream of HNO3 (63 wt) Plant - ELECNRTL
• It can handle very low and very high
  concentrations
• It can handle aqueous and mixed solvent systems
• The solubility of supercritical gases can be
  modeled using Henry s Law
• The Redlich-Kwong equation of state is used for
  all vapor phase properties
• Mixture Types
• Any liquid electrolyte solution unless there is
  association in the vapor phase
• Range
• Vapor phase properties are described accurately
  up to medium pressures.

Aspen Database
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Summary

• Produce 3,289 TPD of 63 wt. Nitric Acid
• Key Equipment
• Ammonia Evaporator, Air Compressor, Catalytic
  Reactor, and Absorption Column
• Competing Processes
• Platinum-Rhodium Alloy or Cobalt Oxide
• Single or Dual Pressure System
• Energy Recovery
• Materials of Construction

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Looking Ahead

• Problem areas to be addressed
• Catalyst decision
• Single or dual pressure plant decision
• Material balance
• Thermodynamic model
• Method of pollution control
• Equipment material
• Finalized Material and Energy Balances
• Rough Economics
• Hand Calculations
• Additions to Report

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References

• ASPEN Thermodynamic Database.
• Available and Emerging Technologies for Reducing
  Greenhouse Gas Emissions from the Nitric Acid
  Production Industry. U.S. Environmental
  Protection Agency. 2010. lthttp//www.epa.gov/nsr/
  ghgdocs/nitricacid.pdfgt.
• Bell, B. Platinum Catalysts in Ammonia Oxidation.
  Platinum Metals Rev. 4. 1960.
• Best Available Techniques for Pollution
  Prevention and Control in the European Fertilizer
  Industry, Production of Nitric Acid. EFMA. 2000.
  lthttp//www.efma.org/PRODUCT-STEWARDSHIP- PROGRAM-
  10/images/EFMABATNIT.pdfgt.
• Cobalt Oxide Catalyst. Catalyst Development
  Corporation. 2003. lthttp//www.cobaltoxide.com/gt.
• Pratt, Christopher, and Robert Noyes. Nitrogen
  Fertilizer Chemical Processes. Pearl River 1965.
• Ullmans Encyclopedia of Industrial Chemistry.
  Volume A17. VCH.

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Questions?