J-T Plants are typically used when the Customer wishes to maintain high recovery of propane (C3) and heavier products, but not add the extra expense or time to the schedule by adding an expander. In the case where the Inlet Gas is “rich” in hydrocarbon liquids, mechanical refrigeration may be incorporated into the plant design. Using integrated heat exchange, separation and pressure expansion through the Joule-Thompson (J-T) valve, the hydrocarbon components are fractionated in the Demethanizer/Deethanizer to deliver a Y-Grade NGL Product and a Residue Gas stream.
Mechanical Refrigeration/Dewpoint Control Plant
The advantage of a Dewpoint Control Plants is that outlet pressure is equal to inlet pressure, which lessens the pressure drop through the plant. This advantage reduces the need for residue gas compression. The hydrocarbon dewpoint of the natural gas is controlled via cross heat exchange and mechanical refrigeration (typically propane). NGL recovery levels are generally much lower than either the Expander or J-T Plants and are typically utilized only to make a salable gas product.