MDEA Sweetening
Introduction
Sour gas from inlet separation and filtration is now divided into two equal flows for the two MDEA contactors. Flow to the contactors is controlled by individual flow control valves (FCVs). Gas enters the bottom of the contactor and flows upwards through 28 stainless steel trays coming into contact with lean amine (MDEA) flowing downwards. The lean MDEA absorbs the H2S and C02 from the gas flowing upwards through contactor through physical and chemical attraction. The MDEA leaves the contactor as rich amine to the regeneration section and the gas leaves sweet (no H2S or C02) to the TEG dehydration section. Lean amine is supplied by high pressure charge pumps described in module 8. Figure 1 block flow diagram highlights the amine location of the amine sweetening processes described in this module.
Amine Sweetening in A+B Contactors
- Raw Gas Flow to Amine Contactors (FI-1105A/B)
After the raw gas flow leaves the Inlet Gas Filter (FI-1105), the raw gas flow branches to feed the two, parallel Amine (PV-1101A/B) contactors (see Figure 2). The equipment numbering described below is for contactor A but contactor B is exactly the same.
The flow to the Amine contactor (PV-1101A) passes through a meter run that monitors and controls the raw gas flow to each Contactor. The meter run consists of the following equipment to monitor and control the raw gas flow to each contactor.
- Ultrasonic flow transmitter: this flow transmitter calculates the basic raw gas flow rate from the gas flow.
- Temperature transmitter (TI-1023) and a pressure transmitter (PI-1023): these pressure/temperature transmitters provide data which allows the basic flowrate to be converted to the compensated raw gas flow rate.
- Raw Gas Flow Control Valve: The feed gas flow rate for each amine contactor is controlled by a pre set flow control valve. The flow control valve (FV-1021) maintains the calculated set point that is used from the Ultrasonic flow transmitter and respective temperature and pressure transmitters.
Both compensated raw gas flow rates are adjusted based on the inlet raw gas flow transmitter (FT-8006) located in the inlet/outlet building. The Raw gas flow control valves for each contactor will automatically adjust their position to equally share the inlet raw gas flow measured at FT-8006.
