Novel integrated energy-efficient dual-effect single mixed refrigerant and NGLs recovery process for small-scale natural gas processing plant

Abstract

The design of natural gas liquefaction process operated at offshore regards space as a design variable and requests an integrated and compact process due to space limitation. This study proposes an integrated process for natural gas liquefaction and NGLs recovery based on single mixed refrigerant (SMR) cycle. The considered SMR refrigeration cycle functions as dual mixed refrigerant (DMR) to provide two separate refrigeration levels for natural gas precooling and subcooling. NGLs recovery section includes a conventional column and a heat integrated distillation column in indirect sequence to produce lean gas, ethane liquid, LPG and gasoline. Liquefaction operating parameters were optimized using genetic algorithm in search of optimal values for profitable process with optimal energy consumption. NGLs recovery section of the proposed process is flexible, operable in both ethane recovery and ethane rejection modes. Based on base case process, the proposed process lowers energy consumption by 14%. The key features of the proposed process are cold utility recovery through self-refrigeration and ethane liquid recovery.