Sour Water Stripping-(Single stage)

Sour Water Stripping-(Single stage)

Instructions



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

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

Simulation Set Up


Objective

  1. Target is  < 30 ppmw NH₃ in the stripped water

Flowsheet

 

Inputs

  1. Components:  Carbon dioxide, Hydrogen Sulphide, Ammonia, Water

Sour Water

  1. Sour water flow rate>> 150,000 lb/hr
  2. Temperature>> 135°F
  3. Pressure>> 70 psig
  4. Component composition>> (CO₂>> 0.1%, Ammonia>> 2%, H₂S>> 1.5%, Water>> 96.4%,  All in mol%) 

Feed/Btms

  1. Configuration
    1. Flow Type
      1. Countercurrent flow
    2. Shell side outlet
      1. Select "Stream number 7"
  2. Heat Transfer
    1. Calculation mode
      1. Select " Simple energy balance"
        1. Thermal Spec>>Tube outlet temperature>> 235°F
    2. Enable "Apply LMTD Correction factor (Ft factor)
      1. Select "Let ProTreat calculate"
  3. Pressure
    1. Shell side
      1. Select Pressure drop >>5 psi
    2. Tube side
      1. Outlet pressure>> 70 psia
  4. Thermo & Convergence
    1. Thermodynamic package
      1. Shell side>>Tube side>> OGT Gas Treating

SWS

  1. Configuration
    1. Select the check boxes that the column has reboiler and condenser, and has reflux to column (% return is 100%)
    2. Section
      1. 1 - Generic Value Trays
        1. Data 
          1. Tray data
            1. Number of trays>>40
            2. Tray spacing>> 2 feet
            3. Number of passes>> 1
            4. Weir height>> 2 inch
            5. Foam derating factor>> 0.7
        2. Size
          1. Diameter calculated
            1. %Vapor flood>> Downcomer flood>> 70%
        3. Pressure
          1. Enable "Specify pressure>> 15 psig >> Tray number 1"
          2. Enable "Calculate pressure drop"
  2. Cond/Reboil
    1. Condenser
      1. Temperature>> 180°F
      2. Select pressure drop>>0 psi
    2. Reboiler
      1. Select vapor return line pressure drop>>0 psi
    3. Select "Reboiler steam flow ratio"
      1. Reboiler steam flow ratio>> 1.3 lb steam /std US gallon
        1. Basis liquid stream for calc>> 1
        2. Pressure>> 50 psig
  3. Models
    1. Thermodynamic package>> OGT Gas Treating
    2. Reaction kinetic model for CO₂ and COS
      1. Select " ProTreat default (most columns)"
  4. Streams
    1. Feed & Draw streams
      1. Streams
        1. Stream 2>> connect>> above tray no. 6
        2. Stream 12>> connect >> above tray no. 35
      2. Top vapor stream
        1. Select " Rate stream"
      3. Bottom liquid stream
        1. Select "Rate Stream"

Pump-1 

  1. Pump>>Pressure rise>>50 psi  
  2. Efficiency>>75%

Cooler

  1. Cooler>>Duty>>Outlet temperature>>120°F
  2. Pressure
    1. Pressure drop>>10 psi
  3. Thermo
    1. Thermodynamic Package>> OGT Gas Treating

Run Simulation

  1. Review all the inputs and run the simulation
  2. What is the concentration of Ammonia in the stripped water in ppmw?
  3. Is the concentration of NH3 maintained below 30 ppmw?

Results & Discussion

Output-1

  1. Concentration of Ammonia in the stripped water is 39.66 ppmw
  2. Will increasing reboiler duty decrease the NH3 concentration in the stripped water?
    1. At increased reboiler steam flow ratio of 1.4 lb steam/ std US gallon, concentration of Ammonia in the stripped water is 10.54 ppmw

Something to think about

  1. Which one is most judicious to use, single stage or two stage sour water stripper? What considerations will you use to determine which of the two methods to use?
  2. For more detailed information about SWS visit ___________________












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