A study on the value estimation of LNG cold heat with application to the liquefaction of various refrigerants

Refrigeration effects lower than − 20°C can be traditionally achieved using a vapor-recompression refrigeration cycle with various refrigerants having their own supply temperatures. In this study, the values contained in the liquefied natural gas (LNG) cold heat have been estimated when more than 30 pure refrigerants are liquefied by exchanging heat with LNG instead of using a vapor-recompression refrigeration cycle. There was a total of 35 selected refrigerants for evaluation of cold heat price contained in LNG, which includes n-butane, propane, propylene, ammonia (NH 3 ), 1,1,1,2-tetrafluoroethane (R-134a), hydrochlorofluorocarbon (R-22) etc. Simulation works have been carried out for each single refrigeration cycle using the Peng-Robinson equation of state in combination with TWU’s alpha function. PRO/II with PROVISION V2021, a steady-state simulation tool from Aveva Company, was used to model the refrigeration cycle and LNG cold heat value estimation. It was concluded that the estimated values of the LNG cold heat were inversely proportional to refrigerant supply temperature since the compressor power is proportionally increasing when the refrigerant supply temperature is lower and vice versa.