Abstract:
                                      Objective The aim is to remove the acid-to-gas, separate and liquefy CH4 and H2 in underground coal-to-gas.
Methods Comparing the common separation methods, the low temperature rectification method is determined to use for removing acid gas, separating and liquefying CH4 and H2. According to the principle of cryogenic rectification, a new process is designed for underground coal-to-gas to remove acid gas and separate and liquefy CH4 and H2. This process mainly consists of two rectification towers, a two-phase separator and three-stage helium expansion refrigeration system. Simultaneously, HYSYS software is used to simulate and analyze the process for determination of its optimal parameters.
Results This process can remove the molar fraction of CO2 to 0 and H2S to 3.65×10-14, meeting the processing requirements. At the same time, the recovery rate of CH4 is 99.97%, the molar fraction of pressurized liquefied natural gas (PLNG) is 99.97%, the recovery rate of H2 is 98.30%, and the molar fraction of liquid hydrogen (LH2) is 99.99%.
Conclusions This process can effectively use underground coal-to-gas to produce PLNG and LH2, and the required energy consumption is 11.64% lower than that of traditional processes, which has high economic benefits.