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 without wash section

Objective

Inputs

1. Components:  Carbon dioxide, Nitrogen, Oxygen, MEA, Water

Stream Information (Feed Gas)

1. Set up a conventional absorber & regenerator loop in ProTreat as shown in the flowsheet
2. Inputs taken for the exercise 
1. Gas flow rate: 25,000 kmol/hr
2. Temperature : 40 °C
3. Pressure : 1.03 kg/cm²(g)
4. Component composition: (CO₂: 9%, N₂: 86.8%, O₂: 4.2%, Saturation: 100%, All in mol%) 
   
5. Connect the feed stream to the bottom of section: 2 packing of the absorber
   

Absorber Inputs (section-1)

1. Packing type: Mellapak plus
2. Packing depth: 5 feet
3. Packing material: Metal
4. Packing size: M252.Y
5. Number of segments: 100
6. Hydraulics: Sulzer Proprietary 
7. Mass Transfer: Billet-Schultes
8. Size>>Calculated: 50% capacity
9. Pressure>>calculate pressure drop

Absorber Inputs (section-2)

1. Packing type: Mellapak plus
2. Packing depth: 45 feet
3. Packing material: Metal
4. Packing size: M252.Y
5. Number of segments: 100
6. Hydraulics: Sulzer Proprietary 
7. Mass Transfer: Billet-Schultes
8. Size>>Calculated: 75% capacity
9. Pressure>>set pressure by feed stream 27
   
10. Calculate pressure drop
    

Rich pump Input

1. Pump>> Outlet Pressure>>3.5 kg/cm²(g)
   
2. Efficiency>>75%

HeatX-1 Inputs

1. HeatX-1>>Heat Transfer>>Thermal Spec>>Tube outlet Temperature>>90 °C
2. Apply LMTD Correction Factor>>Let ProTreat Calculate
   

Regenerator Inputs

1. Check the column “has condenser”, “has reboiler”, “has reflux to column % return-100%
2. Connect feed stream above the tray number 3 in regenerator
3. Tray Type: Generic valve trays 
4. Number of Trays: 20
5. Tray Spacing: 0.6 meters
6. Number of passes: 4
7. Weir height: 0.05 meters
8. Foam Derating Factor: 0.8 
9. % Vapor flood: 70 % ,Downcomer Flood: 35%
10. Pressure>>Set pressure by feed stream 33
11. Condenser/Reboiler>> Condenser >> Temperature>> 40 °C
12. Condenser>> Pressure Drop >>0 kg/cm²(g)
13. Reboiler>> Vapor return line pressure drop >> 0 kg/cm²(g)
14. Reboiler Steam Flow Ratio>> 100 kg steam /std m³
15. Basis liquid stream for calculation >>Pump inlet stream
16. Pressure >> 3.5 kg/cm²(g)
    

Lean Pump Input

1. Pump>> Outlet Pressure>>3.5 kg/cm²(g)
   
2. Efficiency>>75%
   

Cooler Input

1. Cooler >> Duty >>Outlet Temperature>> 35 °C
   

Amine Inputs in Control Block-1

1. Stream Flow rate: 4,000 m³/hr
   
2. MEA Composition: 30 wt. %
   
3. Select method for calculating make up as “Control Block In/ Out Streams”
   

Stream Information (Recycle block)

1. Recycle block stream is a tear stream. An educated guess values must be given for the initial calculations to proceed
2. Select the preferred components and feed the input data in the respective recycle block
3. Recycle flow rate: 1,750 m³/hr
4. Temperature: 40 °C
5. Pressure: 3 kg/cm²(g)
6. Composition: (CO₂ : 0.2 Loading, MEA: 30 wt. %)
7. Select water specification as “is remainder (solvent streams only)”

Run Simulation - without wash section

1. Run simulation without wash section and note the results
   

Simulation Set Up with wash section

Flowsheet with wash section

Inputs

1. Add a wash section to the existing flowsheet without changing any previous inputs
   

Stream Information (wash recycle)

1. Recycle block stream is a tear stream. An educated guess values must be given for the initial calculations to proceed
2. Select the preferred components and feed the input data in the respective recycle block
   
3. Draw 90 percent of the flow to stream 21 from the bottom of section-1 packing in the absorber
   
4. Recycle flow rate: 200 m³/hr
5. Temperature : 60 °C
6. Pressure : 1.03 kg/cm²(g)
7. Composition: (CO₂ : 0.0001 Loading, MEA: 1 wt.%)
8. Water Specification “Is Remainder(Solvent streams only)”
   

Cooler-2 Input

1. Cooler >>Duty >> Outlet Temperature>>40 °C
   

Makeup water

1. Makeup water flow rate: 1,500 kg/hr
2. Temperature : 37 °C
3. Pressure : 1.03 kg/cm²(g)
4. Water specification “ Is Remainder(Solvent streams only)”

Mixer

1. Mix the outlet stream from cooler and make up water in a mixer as shown in the flowsheet 
   
2. Connect the outlet stream of mixer to the top of the section-1 packing

Run Simulation with wash section

1. Run the simulation with the wash section and note the results
   

Results & Discussion

Output

Interpretation

1. From the results we can observe that using wash section probably helps in decreasing the amine losses thereby saving capital to the plant
   
2. In the current example, wash section saved about 80% of the amine that got lost in the case of absorption without wash section.
   

Something to think about

1. If you can observe the CO₂ concentrations in both the cases, case without wash section results in a slight more treating compared to wash section. What can be the reason?