Study Of Vapor-liquid Equilibrium For Synthetic Natural Gas And Its Liquefaction And Hydrogen Separation Process

It is very necessary to improve the efficiency of coal utilization withless pollution under the energy-saving and emission-reduction policy. Ofall the technologies in clean using of coal, synthetic natural gas (SNG)technology has the advantages of comparably simple equipment, maturetechnology, low investment according to unit heat value and lesspollution during producing process. Cryogenic liquefaction is an efficientway of transmitting SNG. The SNG after pretreatment usually containsunconventional contents as nitrogen and hydrogen (0.7-9.8%), despite ofthe main content as methane. And hydrogen differs most in thermalproperty and brings remarkable influences on the liquefaction process forSNG.This paper mainly focuses on the following aspects:1. Modifications have been done to the vapor-liquid equilibrium(VLE) experimental measurement equipment and VLE data for H2+CH4system at100.1-120.5K,0.1-3MPa have been experimentally measured.The reliability of the experimental equipment in measuring the VLE forhydrogen-containing SNG has been verified. And then the VLE data forH2+CH4+N2ternary system at100.0-125.0K,0.1-5MPa have beenexperimentally measured.2. ZJ EoS and GERG EoS have been applied in the calculation ofVLE data for CH4+H2+N2ternary system at the experimentalmeasurement conditions and results are compared with the correspondingdata. Generally, both ZJ EoS and GERG EoS have good accuracy and reliability.3. Based on the experimentally measured equilibrium pressure,temperature and liquid phase compositions (p-T-xi) for CH4+H2binarysystem, a new binary interaction coefficient kijhas been correlated for PREoS, which remarkably improve the accuracy of applying PR EoS incalculating the VLE data for hydrogen-containing SNG at cryogenictemperatures and low pressures.4. By studying the reliability of PR, ZJ and GERG EoSs, GERG EoShas been recommended as the most suitable property package for processsimulation on hydrogen-containing SNG. Moreover, applied the GERGEoS as the property package, the nitrogen expansion intergrated withdifferent dehydrogenization methods have been simulated and optimizedfor SNG with various hydrogen contents (<10%).