Sulphur Recovery Unit-SRU

Sulphur Recovery Unit-SRU

Instructions


  1. This article contains a series of steps to feed the data to the flowsheet, run the simulation, interpret the results

  2. User can either follow the series of steps mentioned in the article or download the ProTreat file attached to this article, review the inputs and run the simulation  

Simulation Set Up

Objective

  1. Target is  > 97% Sulphur Recovery

Flowsheet

Inputs

  1. Components>> Carbon dioxide, Hydrogen Sulphide, Sulphur dioxide, Sulphur - S₂ , Sulphur - S₆ , Sulphur - S₈, Argon,  Ammonia, Methane, Ethane, Propane, n-Butane, n-Pentane, n-Hexane, Carbonyl Sulphide, Carbonyl disulphide, Hydrogen, Carbon monoxide, Nitrogen, Oxygen, Nitric oxide, Nitrogen dioxide,  Water

TGU Recycle 

  1. Temperature>> 120°F
  2. Pressure>> 11.4 psig
  3. Component flowrates >> (Water>> 2.56, Carbon dioxide>> 10.03 Hydrogen Sulfide>> 30.1, All in lbmol/hr)

Amine AG

  1. Temperature>> 104°F
  2. Pressure>> 12.8 psig
  3. Component flowrates>> (Water>> 8.66, Ammonia>> 0.24, methane>> 0.11, ethane>> 0.07, propane>> 0.04, Hydrogen Sulfide>> 224.45, hydrogen>> 0.9, All in lbmol/hr)

Mixer-1 

  1. Mix the streams from Amine AG and TGU Recycle 
  2. Thermodynamic Package
    1. OGT Gas Treating
  3. Outlet stream 4 specified as
    1. Pressure drop "0" psi
  4. Outlet of Mixer-1 is connecte d  to ARU KO drum

ARU KO drum

  1. Outlet stream number 6 "Is Vapor"
  2. Flash type
    1. Flash type>>QP(Enthalpy and pressure)
    2. Heat duty " 0 " watts
  3. Sizing
    1. Liquid residence time>>300 seconds
  4. Thermo + Iteration
    1. Thermodynamic package>> OGT Gas Treating
  5. Pressure
    1. Pressure drop>>0 psi
  6. Vapor outlet of ARU KO drum is sent to Mixer-2

SWS Gas Input 

  1. Temperature>> 185 °F
  2. Pressure>> 11.4 psig
  3. Component flowrates>> (Water>> 19.25, Hydrogen Sulfide>> 24.01, Ammonia>> 23.15, All in lbmol/hr)
  4. SWS Gas Input stream is connected to the SWS KO drum

SWS KO drum

  1. Outlet stream number 10 "Is Vapor"
  2. Flash type
    1. Flash type>>QP(Enthalpy and pressure)
    2. Heat duty " 0 " watts
  3. Sizing
    1. Liquid residence time>>300 seconds
  4. Thermo + Iteration
    1. Thermodynamic package>> OGT Gas Treating
  5. Pressure
    1. Pressure drop>>0 psi
  6. The vapor stream from SWS KO drum is connected to Mixer-2

Air

  1. Temperature>> 252°F
  2. Pressure>> 11.1 psig
  3. Stream Total flow rate>> 1151.563 lbmol/hr
  4. Component composition>> (Water>> 4.76, Nitrogen>> 75.28, Oxygen>> 19.9 All in mol%)

Mixer-2

  1. Mix the streams from SWS KO (vapor stream) and Air stream
  2. Thermodynam ic Package
    1. Sulphur
  3. Outlet stream 1 specified as
    1. Pressure drop "0" psi
  4. The Outlet of mixer-2 is connected to Reaction Furnace

Thermo transfer blocks

  1. After the ARU KO drum, SWS KO drum, and the Air stream there are thermo package transfer blocks to transfer stream properties to Sulphur thermo

Reaction Furnace

  1. Enable "Display Flames", "Temperature sets flame colour", Flame colour>>yellow
  2. Performance
    1. Temperature
      1. Heat Input>>0 watts
    2. Pressure
      1. Pressure drop>>0 psi
  3. Thermo/calcs
    1. Thermodynamic package>>Sulphur
  4. Reaction model
    1. Kinetic model
      1. NH3 destruction
        1. burner mixing characteristic "Hi-Intensity burner"
      2. BTEX/Hydrocarbon destruction/ CS₂ formation
    2. Reactor sizing/rating
      1. Primary specification
        1. Residence time>>1.3 seconds
    3. Reactor dimensions (inside refractory)
      1. Enable "Use/calculate layout dimensions (1 required)"
      2. Inside diameter 2000 mm

WHB (Waste Heat boiler)

  1. Outlet stream from Reaction furnace is connected to waste heat boiler
  2. Basic data
    1. Process side pressure 
      1. Pressure drop>>0.3 psi
    2. Calculation mode
      1. Heat transfer rate>>sizing
    3. Segmentation
      1. Number of segments (max 100)>>100
      2. Segment by increments of >>Temperature
    4. Enable "Sulfidation Corrosion"
    5. Liquid entrainment>> 7 lb/100 lbmol gas
    6. Process-side outlet stream number 8 " Is Liquid"
  3. Heat transfer
    1. Inside convective coefficient
      1. Let ProTreat calculate coefficient
    2. Optional heat transfer terms
      1. Outside convective heat transfer coefficient>>150 Btu/hr-sqft-F
      2. Radiative heat transfer coefficient
        1. Let ProTreat calculate coefficient
          1. Inside tube wal l emissivity>>0.9
      3. Inside fouling resistance>>0.004 hr-sqft-F/Btu
      4. Outside fouling resistance>>2.16E-04 hr-sqft-F/Btu
      5. Tube wall heat transfer resistance
        1. Material of construction >> Carbon steel
        2. Tube wall thickness>> 1.042E-02 feet (3.17 millimeter)
  4. Equipment data
    1. Tube specifications
      1. Inlet tube velocity>> 2 lb/ft ² -s
      2. Tube ID>> 1.982 in
    2. Exchanger specifications
      1. Sizing mode
        1. Process vapor outlet temperature>>1100°F
  5. Cooling medium
    1. Include simplified cooling medium
      1. Saturated steam pressure>> 614.504 psia
  6. WHB Reactions
    1. Enable "Report reaction details"
    2. Enable "Kinetic Model for Reaction 1" and "Kinetic Model for Reaction 2"
  7. Sulfidation
    1. Enable "Couper Gorman"
      1. Carbon Steel
    2. Enable "Modified couper gorman (Martens et al.) - carbon steel"
    3. Enable "ASRL - carbon s teel"

Sulphur condenser-1 

  1. Basic data
    1. Process side pressure
      1. Pressure drop>>0 psi
    2. Calculation mode
      1. Simple energy balance
    3. Segmentation
      1. Divide into segments
        1. Number of segments (max 100) >> 10
        2. Segment by increments of Temperature
    4. Liquid entrainment >>7 lb/100 lbmol gas
    5. Process-side outlet stream number 19 " Is Vapor"
  2. Heat Transfer
    1. Process outlet tem perature>>300°F
  3. Cooling Medium
    1. Enable "Include simplified cooling medium"
      1. Saturated steam pressure>>64.69psia

Reheater-1

  1. Duty
    1. Outlet temperature>>450°F
  2. Pressure
    1. Pressure drop>>0 psi
  3. Thermo
    1. Thermodynamic package>> Sulphur

Converter-1

  1. Reactor data
    1. Thermal specs
      1. Thermal mode>> Heat duty
      2. Heat duty>>0 Btu/hr
    2. Pressure
      1. Select " Specify by overall block"
        1. Pressure drop>>0.5 psi
    3. Reactions
      1. Specify by overall block
        1. Reaction mode>> Kinetic
        2. Select all reactions>> Kinetic factor>>1
    4. Vessel
      1. Volume mode>>Select calculated volume
      2. Flow direction>>Select Perpendicular (Horizontal vessel)
  2. Section data
    1. Basic data
      1. Name>>section
      2. Type>>Alumina catalyst
      3. Shape
        1. Activity parameter>>Set by catalyst age>>Set Fresh
    2. Size
      1. Bed size
        1. Average space velocity>>3 lbmol/hr/ft^3
      2. Loaded density
        1. Use specified
        2. Loaded density>>42 lb/cuft
      3. Numerical integration
        1. Number of segments>>15
        2. Segment distribution>>Uniform

Reheater-2

  1. Configuration
    1. Flow type>>Countercurrent flow
    2. Shell side outlet>>Stream number 25
  2. Heat transfer
    1. Calculation mode>> Simple energy balance
    2. Thermal spec
      1. Tube temperature change>> -70°F
    3. Apply LMTD correction factor(Ft factor)
      1. Let ProTreat calculate
  3. Pressure
    1. Shell side
      1. Pressure drop>>0.2 psi
    2. Tube side
      1. Pressure drop>>0.4 psi
  4. Thermo and convergence
    1. Thermodynamic package
      1. Shell side>>Sulphur
      2. Tube side>> Sulphur

Sulphur condenser-2

  1. Basic data
    1. Process side pressure
      1. Pressure drop>>0.5 psi
    2. Calculation mode
      1. Simple energy balance
    3. Segmentation
      1. Divide into segments
        1. Number of segments (max 100) >> 10
        2. Segment by increments of Temperature
    4. Liquid entrainment >>7 lb/100 lbmol gas
    5. Process-side outlet stream number 24 " Is Vapor"
  2. Heat Transfer
    1. Process outlet tem perature>>362°F
  3. Cooling Medium
    1. Select "Ignore Cooling medium"

Converter-2 

  1. Reactor data
    1. Thermal specs
      1. Thermal mode>> Heat duty
      2. Heat duty>>0 Btu/hr
    2. Pressure
      1. Select " Specify by overall block"
        1. Pressure drop>>0.5 psi
    3. Reactions
      1. Specify by overall block
        1. Reaction mode>> Kinetic
        2. Select all reactions>> Kinetic factor>>1
    4. Vessel
      1. Volume mode>>Calculated volume
      2. Flow direction>>Perpendicular (Horizontal vessel)
  2. Section data
    1. Basic data
      1. Name>>section
      2. Type>>Alumina catalyst
      3. Shape
        1. Activity parameter>>Set by catalyst age>>Set Fresh
    2. Size
      1. Bed size
        1. Average space velocity>>3 lbmol/hr/ft^3
      2. Loaded density
        1. Use specified
        2. Loaded density>>42 lb/cuft
      3. Numerical integration
        1. Number of segments>>15
        2. Segment distribution>>Uniform

Sulphur condenser-3 

  1. Basic data
    1. Process side pressure
      1. Pressure drop>>0.5 psi
    2. Calculation mode
      1. Simple energy balance
    3. Segmentation
      1. Divide into segments
        1. Number of segments (max 100) >> 10
        2. Segment by increments of Temperature
    4. Liquid entrainment >>7 lb/100 lbmol gas
    5. Process-side outlet stream number 28 " Is Vapor"
  2. Heat Transfer
    1. Process outlet tem perature>>335°F
  3. Cooling Medium
    1. Select "Ignore Cooling medium"

Reheater-3

  1. Basic data
    1. Process side pressure
      1. Pressure drop>>0.4 psi
    2. Calculation mode
      1. Select "Simple energy balance"
    3. Segmentation
      1. Divide into segments
        1. Number of segments (max 100) >> 10
        2. Segment by increments of Temperature
  2. Heat Transfer
    1. Process outlet tem perature>>408°F
  3. Heating Medium
    1. Sel ect "Include simplified heating medium"
      1. Saturated steam pressure>>614.69 psia
      2. Enable "Create steam stream"
        1. Select "Inlet steam superheat>>20°F"

Converter-3 

  1. Reactor data
    1. Thermal specs
      1. Thermal mode>> Heat duty
      2. Heat duty>>0 Btu/hr
    2. Pressure
      1. Select " Specify by overall block"
        1. Pressure drop>>0.5 psi
    3. Reactions
      1. Specify by overall block
        1. Reaction mode>> Kinetic
        2. Select all reactions>> Kinetic factor>>1
    4. Vessel
      1. Volume mode>>Calculated volume
      2. Flow direction>>Perpendicular (Horizontal vessel)
  2. Section data
    1. Basic data
      1. Name>>section
      2. Type>>Alumina catalyst
      3. Shape
        1. Activity parameter>>Set by catalyst age>>Set Fresh
    2. Size
      1. Bed size
        1. Average space velocity>>3 lbmol/hr/ft^3
      2. Loaded density
        1. Use specified
        2. Loaded density>>42 lb/cuft
      3. Numerical integration
        1. Number of segments>>15
        2. Segment distribution>>Uniform

Sulphur condenser-4 

  1. Basic data
    1. Process side pressure
      1. Pressure drop>>0.6 psi
    2. Calculation mode
      1. Simple energy balance
    3. Segmentation
      1. Divide into segments
        1. Number of segments (max 100) >> 10
        2. Segment by increments of Temperature
    4. Liquid entrainment >>2 lb/100 lbmol gas
    5. Process-side outlet stream number 16 " Is Vapor"
  2. Heat Transfer
    1. Process outlet tem perature>>280°F
  3. Cooling Medium
    1. Select "Ignore Cooling medium"

Mixer-4

  1. Liquid Sulphur streams from Sulphur condenser-1 and WHB-1 are connected to inlet of Mixer-4

Mixer-3

  1. All the liquid Sulphur streams and outlet of mixer-4 are mixed and fed to Sulphur pit/storage

ADA

  1. Solution method
    1. Method>> Quadratic search(optional limits)
    2. Max Iterations>>30
    3. Enable "Restart from previous solution"
  2. Adjustment variable
    1. Adjust variable
      1. Block name>> Air
      2. Adjust variable>>Total flow , in "lbmol/hr"
  3. Target variable
    1. Target (Spec) variable
      1. Stream ID>> Material stream 16
      2. Target variable>>Component mole flow ratio
      3. Target value>>(Hydrogen sulfide/Sulphur dioxide)>>2
      4. Absolute tolerance>>0.05

Run Simulation

  1. Review all the inputs and run the simulation
  2. What is the total amount of recovered Sulphur in long tons per day, and concentration of different species of Sulphur in the final product from mixer-3?

Results & Discussion

Output-1

  1. Total recovered Sulphur is 91.1 long tons/day
  2. Concentrations of different species of Sulphur are as follows>>( S₂>>5.02E-05 mol%, S₆>>2.663 mol%,  S₈>>97.23 mol%, Hydrogen Sulfide>>9.7E-02 mol%)

Something to think about

  1. Can we achieve 99 % Sulphur recovery or higher? Is it possible to do this using the Claus SRU section or do we need additional sections?
  2. What is the extent of recovery in the thermal stage and the catalytic stage(s)? Is it possible to increase the recovery of the thermal stage further? What limits the recovery in each stage whether it is thermal or catalytic?
  3. For more detailed information about SRU visit ___________________
















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