A choke plant (sometimes referred to as a J-T plant or auto-refrigeration plant)is a gas plant that utilizes the pressure of the inlet gas stream (sufficiently high due to compression or high wellhead pressures) and the Joule-Thomson effect (an expansion valve in the system)to create the necessary cooling to remove liquids from the gas stream.
I won't get into the details about process economics and when you would or wouldn't use this type of technology, but there is a helpful article in Vol 2 of the John M Campebell Gas Conditioning and Processing handbooks.
1) Perform adiabatic flash but you can put 80% isentropic for the real life ( never constant enthalpy in real life)
2) Application shall not over cricondense bar , normally when gas plant 40 bar<Pressure<90 bar system
3) After JT valve you may need LTCS pressure vesel due to that area always link to blow down system ( low temperatur carbon steel) since the temperature is low after J-T effect.
4)piping carbon steel can stand -29 C so no problem. below that medium alloy/stainless shall be use up to -45 C.
5) Chock plant/J-T can work if gas before chock has pre-cooling system use the maulti stream heat exchanger by use its F/E (fee/effluent) and after JT the LTS ( low temperature separator will reject liquid.
6) Normall J-T reject only rough composition/heavy end such as C5+ 90% but not easy to reject C3+ expect 20-30% ( which should use other means such as mechanica C3 refrigeartion)
