Energy, exergy and pinch analyses of an integrated cryogenic natural gas process based on coupling of absorption–compression refrigeration system, organic Rankine cycle and solar parabolic trough collectors

Abstract

The natural gas entering the liquefaction cycle usually consists of nitrogen, ethane, propane and also heavier hydrocarbons which are economically explainable to be separated from methane, considering that their heating values are higher than methane. In this paper, a hybrid system is developed and analyzed for liquefied natural gas, natural gas liquids and power tri-generation using LNG/NGLs recovery system, absorption–compression combined refrigeration, organic Rankine cycle and solar parabolic trough collectors. This integrated structure produces 54.12 kg s−1 NGLs, 66.52 kg s−1 LNG and 278.5 MW net power output. Specific power consumption, thermal and exergy efficiencies of the hybrid system are 0.3771 kWh kg−1 LNG, 78.38% and 84.47%, respectively. The pinch method is used to extract the heat exchanger network related to the multi-stream heat exchanger of the hybrid system. To simulate the integrated structure, MATLAB programming, HYSYS and TRNSYS software with the weather conditions of Bandar Abbas city in Iran are used. The effect of natural gas composition entering the cycle on system parameters is studied and reported. Results show that with the reduction in methane percentage in natural gas to 55 mol%, specific power consumption increases to 0.6004 kWh kg−1 LNG, and thermal efficiency decreases to 71.61%. The integrated structural behavior at different operating conditions is used to investigate the sensitivity analysis.