This unit was designed to optimize the current gas processing unit (GPU) operating. The current propane refrigeration unit had a simple one-loop cycle with two series reciprocating compressors (K-1240 A/B) and two propane flash evaporators with different duties (E-1221, E-1202). Each compressor (K-1240A/B) had a capacity of 564 cub. m/h.
According to the technical revamping of the GPU, the mass flow of refrigerant was increased. Compressors K-1240A/B were replaced for series to parallel in the first stage of compression because the capacity of one of them was not enough for the new refrigerant flow. On the second stage was installed a new compressor K-1240C.
To optimize the operating of the propane refrigeration unit was made a decision to recycle a part of the refrigerant to the second compression stage. Refrigerant is precooled in E-1211, then subcooled in flash sub-cooler E-1230. This allows reducing the temperature of the refrigerant and enough cooling in the flash evaporators E-1221, E-1202.
This flow diagram is flexible to reduce refrigerant flow by switch off one of the compressors K-1240A/B. The recycling flow allows operating the unit without an intercooler between compression stages. Also, the recycling flow allows reducing actual volume flow in front of the second compression stage.