Sour Water Stripping-(Two stage)

Sour Water Stripping-(Two stage)

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  > 90 wt.% H₂S in the H₂S Product stream

Flowsheet


Inputs
  1. Components:  Carbon dioxide, Hydrogen Sulphide, Phenol, Ammonia, Ethane, Propane, n-Butane, n-Pentane, Benzene, n-Hexane, Water

Stream Information (Sour Water)

  1. Set up a conventional regenerator in ProTreat as shown in the flowsheet
  2. Inputs taken for the exercise 
    1. Sour water flow rate: 90226 lb/hr
    2. Temperature : 103 °F
    3. Pressure : 90 psig
    4. Component composition: (water: 98.08 wt.%, CO₂: 0.04 wt.%, H₂S: 0.9 wt.%, Phenol: 0.0005 gmol/L, Ammonia: 0.97 wt.%, Ethane: 0.000133 wt.%, Propane: 0.000632 wt. %, n- Butane: 0.00102 wt.%, n- Pentane: 0.00186 wt.%, Benzene: 0.00223 wt.%, n- Hexane: 0.00225 wt.%)

Divider

  1. Divide 0.0001% stream of the feed and connect it to cooler-1 as shown in the flowsheet
  2. The divided stream is fed to pH meter

Cooler-1 Input

  1. Cooler-1>>Duty>>Outlet temperature>>77 °F

Heat X-1 Input

  1. HeatX-1>> Heat transfer>> Thermal spec>> Shell outlet temperature >>190 °F
  2. Apply LMTD correction factor>>Let ProTreat calculate

H₂S Stripper Inputs

  1. Select the check boxes that the column has reboiler and condenser, and has reflux to column (% return is 100%)
  2. Section-1>>Ballast Ring
  3. Packing depth:10 feet
  4. Packing material: metal
  5. Packing size: 1 inch
  6. Select default numerical segments in segmentation
  7. Hydraulics>> Billet-Schultes
  8. Mass Transfer>> Billet–Schultes
  9. Size>>calculated>>25% flood
  10. Select calculate pressure drop
  11. Connect streams appropriately to absorber based on the flowsheet
  12. Connect feed stream below the bottom of packing
  13. Section-2>>Generic valve trays
  14. Number of trays: 50
  15. Tray spacing: 2 feet
  16. Number of passes: 1
  17. Weir height: 2 inch
  18. Foam derating factor: 0.9 
  19. Vapor flood & Downcomer flood: 70%
  20. Pressure >>Specify pressure below bottom>>60 psig
  21. Select calculate pressure drop
  22. Condenser/Reboiler>>Condenser>>Temperature>>90 °F
  23. Condenser>>Pressure drop>>0 psi
  24. Reboiler>>Vapor return line pressure drop>>0 psi
  25. Reboiler steam flow>>13000 lb/hr
  26. Pressure>>245 psig

Pump-1 Input

  1. Pump>>Outlet Pressure>>175 psi  
  2. Efficiency>>75%

Ammonia Stripper Inputs

  1. Select the check boxes that the column has reboiler and condenser, and has reflux to column (% return is 100%)
  2. Section-1>>Generic valve trays
  3. Number of Trays: 30
  4. Tray spacing: 2 feet
  5. Number of passes: 1
  6. Weir height: 2 inch
  7. Foam derating factor: 0.7 
  8. Vapor flood & downcomer flood: 70%
  9. Pressure>>Specify pressure below bottom>>18 psig
  10. Select calculate pressure drop
  11. Connect streams appropriately to absorber based on the flowsheet
  12. Connect feed stream above tray no 6
  13. Condenser/Reboiler>>Condenser>>Temperature>>160 °F
  14. Condenser>>Pressure Drop>> 0 psi
  15. Reboiler>>Vapor return line pressure drop>> 0 psi
  16. Reboiler steam flow>> 11900 lb/hr
  17. Pressure>>259.7 psia

Pump-2 Input

  1. Pump>>Outlet Pressure>>100 psi  
  2. Efficiency>>75%

Cooler-2 Input

  1. Cooler>>Duty>>Outlet temperature>>90 °F

Run Simulation

  1. Review all the inputs and run the simulation
  2. What is the concentration of Ammonia in top product of H₂S stripper?

Results & Discussion

Output-1

  1. Concentration of Ammonia in the top product of H₂S stripper is 3.322 wt.%
  2. Concentration of H₂S in the top product of H₂S stripper is 90.99 wt.%
  3. Therefore, treating objective met for H₂S
  4. H₂S is recovered in high percentage and is probably used as a feed for SRU
  5. Ammonia from Ammonia stripper can be further purified and sold
  6. H₂S Stripper require high pressure steam source, whereas NH3 stripper can be operated using low pressure steam source

Something to think about

  1. Which one is most economical to use, single stage or two stage sour water stripper considering all the constraints and obtained product value ?
  2. For more detailed information about SWS visit ___________________











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