Amine Unit

In this skid sour gas enters in to amine absorber through inlet separator we separate CO2 with absorption technique. Firstly discuss the types of absorption. There are 9 types of absorption.

 

® Gas Liquid Solid
Gas Gas-Gas Gas-Liquid Gas-Solid
Liquid Liquid-Gas Liquid- Liquid Liquid-Solid
Solid Solid-Gas Solid-Liquid Solid-Solid

 

In our process Gas-liquid absorption is taking place.

 

Nature of absorbent:

In this absorption 50% solution of methyl di ethanol amine (MDEA) with reverse osmosis water (RO water) is prepared to remove CO2 from natural gas. Now we discuss the main vessels and equipments used in the amine unit.

 

  • Amine absorber:

Amine absorber is a vertical column having a height of 45 foots and the internal diameter of 48 inches. This column is used for the absorption purpose. In this section lean amine is showered in a vertical vessel from top, so it absorbed CO2 from natural gas and gas goes to next processing area.

 

  • Internal structure of amine absorber

The internal structure of amine absorber consists of:

  1. Bubble cap trays
  2. Demister pad

 

  1. Bubble cap trays

Bubble cap trays are the perforated trays having the caps on them. In our amine absorption column the main purpose of the caps is to increase the contact time between the two phases (MDEA solution and sour gas). There are 16 trays in the absorber and each tray acts as a distributor. By installing these trays in the absorber, the main function is to increase the time of contact between MDEA and sour gas. As the time increases the maximum amount of CO2 is extracted by the MDEA solution leaving behind gas with a very low amount of CO2.

 

  1. Demister pad

The main purpose of the demister pad is to remove the mist particles from the sour gas. When the gas passes from the demister pad then much of the moisture is removed from it.

 

  • Amine Re-boiler

In this section amine rich with CO2 is re-boiled with Heat transfer medium (HTM) to remove CO2 from amine and become lean amine.

  • Heat Exchanger

It is a plate and frame type heat exchanger. This lean amine passes from heat exchanger where it loses some of the temperature by having a heat transfer with rich amine (amine with CO2). The temperature decreases up to approximately 180°F after passing through exchangers.

  • Lean Booster Pump

 

Lean amine solution then goes to buffer tank. The booster pump takes the suction and discharges it to the lean amine cooler. The booster pump develops the pressure of 40 psi to throw the amine into lean amine cooler.

  • Lean Amin Cooler

 

The amine cooler decreases the temperature of lean amine to 140°F. This lean amine then goes to the plunger pump.

  • Plunger Pump

 

This lean amine then goes to the plunger pump. Plunger pump takes the suction and discharges it at approximately 420 psi.

Power of Plunger Pump: 90KW

  • Reflux Cooler

The steam comes from re-boiler to the stripper separate the CO2 from rich amine and this steam feeds into the reflux cooler. This reflux cooler cools the steam into the liquid form and decreases its temperature.

  • Reflux Accumulator

This liquid water comes from reflux cooler send to the reflux accumulator. Reflux accumulator store the water and send it to the top of the stripper. In this way this process continues.

 

  • Instruments Used at This Skid

 

  • Instruments Used at Amine Absorber

 

  • Pressure Gauge.
  • Temperature Gauge.
  • Level Controller.
  • Level Gauge Glass.
  • Level Control Valve.
  • Shut Off Valve.
  • Pressure Safety Valve.Pressure Gauge PI 201:Sensor Type: Bourdon Type.Manufacturer: Ashcroft

     

    Temperature Gauge TI201:

    Manufacturer: Ashcroft

    Type: Bimetallic.

  • Level Controller: Displacer type pneumatic operated controller to maintain the level. If level increased it will operate the LCV 202 to maintain the level. If amine level increased then it might be possible level goes to gas line.Manufacturer: Fisher.Type: Displacer

    LC-202

     

    Level Control Valve: It controls the level of amine. Controlled with level controller LC202 to control the level.

    Manufacturer: Fisher.

    Type: D3

    LCV-202

     

    Level Switch: Its gives alarm in DCS about the level of amine in absorber. It controls the opening and closing of PSDV-200.

    Manufacturer: PRANK W.MURFHY.

    Sensor Type: Float Type (Micro Switch)

    LSH-201

    LSH-200 interlocked with ESD-3.

    LSL-200

     

    Pressure safety Valve 202: It installed at amine absorber.

    Manufacturer: REETS.

    Set Point: 850 PSIG

     

    Chemical Injection Pump:

    Manufacturer: SIDE WINDER

    Model: 40

    Tag no. P-600

     

    Amine circulates from boiler to boiler after completing purification of CO2 from Natural gas. It goes through different purification areas. There are three main routes.

  • Amine Circulation Routes:
    1. Lean Amine Route
    2. Rich Amine Route
    3. Steam RouteNow discuss separately.
      1. Lean Amine Route:

       

      Amine Re-boiler                Heat Exchange               Amine booster pump              Lean amine Cooler       Plunger Pump                           Amine Absorber.

        

      Instruments Used at This Cycle:

       

      • Temperature Gauge.
      • Level Gauge Glass.
      • Level Switch
      • Pressure Gauge.
      • PSV
      • FTI

       

      Instruments Used at Amin Re-boiler:


      Pressure Gauge P211:

      Indicate the pressure of the vessel.

      Sensor Type: Bourdon Type.

      Manufacturer: Ashcroft.

       

      Temperature Gauge TI212, TI213, TI214:

      Indicate the temperature of the vessel.

      Manufacturer: Ashcroft

      Type: Bimetallic.

       

      Level Gauge:

      It shows the level of Amine in re-boiler.

      Manufacturer: PENBERTHLY.

      Type: Transparent Glass Type.

      LG-205

       

      Level Switch:

      Its gives alarm in DCS about the low level of amine in re-boiler.

      Manufacturer: PRANK W.MURFHY.

      Sensor Type: Float Type (Micro Switch)

      Alarm: LAL 202

       

       

      Instruments Used at Heat Exchanger

       

      Temperature Gauge TI203, TI205:

      Manufacturer: Ashcroft

      Type: Bimetallic.

       

      Pressure Gauge PI 206:

      Sensor Type: Bourdon Type.

      Manufacturer: Ashcroft

       

      Lean Booster pump                           Lean amine Cooler                                     Plunger Pump

       

       

       

      Instruments Used at Lean Booster Pump, Lean Amine Cooler and Plunger Pump

       

      • Pressure Gauge.
      • Temperature Gauge.
      • Vibration Switch.
      • Pressure Safety Valve.
      • Flow transmitter.

       

      Temperature Gauge TI203, TI205:

      Manufacturer: Ashcroft

      Type: Bimetallic.

       

      Pressure Gauge PI 206:

      Sensor Type: Bourdon Type.

      Manufacturer: Ashcroft

       

      Vibration Switch:

      It installed on line after plunger pump. If vibration increases beyond the limit then this switch will operate and shut down the train on this is installed.

      Sensor Type: Snap Switch.

      Manufacturer: Murphy

       

      Pressure safety Valve 202:

      It installed at discharge line to avoid accident. If any valve is close or any hurdle in the way out from plunger then it will releases the amine pressure and save the line from rupturing.

      Manufacturer: REETS.

      Set Point: 850 PSIG

       

       

      1. Rich Amine Route:

       

      In this section amine from amine absorber comes into amine flash tank because amine must consist of hydrocarbon. This rich amine goes to the flash drum after passing from emergency

      shutdown valve (ESDV) and level control valve (LCV). Rich amine containing CO2 enters from top of flash vessel & as it is hollow so the gas in the amine expends. From the center of vessel we will also skim condensate (HC). If some hydrocarbons remain then these removed here by charcoal and sock filters. Charcoal filter removes moister and sock filter removes solid hydrocarbons. Then this rich amine goes to the heat exchanger. Here lean amine and rich amine exchange their temperatures. After that rich amine goes to next process area which is amine stripper. Rich amine enters into the amine stripper vessel. We divide this vessel into two parts that are “amine stripper” & “reflux accumulator”. Here steam is coming from re-boiler. Steam removes CO2 from rich amine in stripper and remaining lean amine goes to the Amine re-boiler.

       

      Amine Absorber                      Flash Tank                              Sock, Charcoal (Filters)             Heat Exchanger                      Amine Stripper                     Amine Re-boiler.

       

      Filters

      We use two filters after flash tank that are Sock filter (Amine filter) & Charcoal filter (HC filter). Sock filter remove solid particles & charcoal filter remove hydrocarbons from the stream.

       

      Instruments Used at This Process Area

       

      • Pressure Gauge.
      • Temperature Gauge.
      • Level Controller.
      • Level Gauge Glass.
      • Level Control Valve.
      • Pressure Safety Valve.
      • Back Pressure Control Valve.
      • Differential pressure Gauge.

       

      Pressure Gauge PI 205:

      Sensor Type: Bourdon Type.

      Manufacturer: Ashcroft

       

      Temperature Gauge TI202:

      Manufacturer: Ashcroft

      Type: Bimetallic.

       

      Level Gauge: 

       Manufacturer: PENBERTHLY.

      Type: Transparent Glass Type.

      LG-203, LG-202

      Level Switch:

      Manufacturer: PRANK W.MURFHY.

      Sensor Type: Float Type (Micro Switch)

      LSH-202

       

      Level Controller: 

      Manufacturer: Fisher.

      Type: Displacer

      LC-203

       

      Back Pressure Control Valve 201:

      Manufacturer: CASHCO

      Type: Globe

      Set point 65psig

       

      Pressure safety Valve 205:

      Manufacturer: REETS.

      Set Point: 150 PSIG

       

       

      1. Steam Route

       

      Amine Re-boiler                    Amine Stripper                              Reflux Cooler                 Reflux Accumulator               Amine Stripper

       

      Steam comes from re-boiler and feed at amine stripper. The main function of amine stripper is to remove carbon dioxide to regenerate the amine solution for reuse. After Amine getting hot due to stream of re-boiler, moisture and CO2 leave at high temperature. So CO2 vented into atmosphere.

      Instruments:

       

      • Pressure Gauge.
      • Temperature Gauge.
      • Level Controller.
      • Level Gauge Glass.
      • Level Control Valve.
      • Pressure Safety Valve.

       

       

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