Discussion on coupling process of decarbonization and hydrogen extraction for underground coal gasification syngas
In response to the characteristics of high synthesis gas temperature(＞200℃),high pressure(3.35 MPa),high saturated water content and complex components(including CH4,H2,CO2,CO,etc.)prepared by underground coal gasification(UCG)technology,a membrane separation + solvent absorption coupling treatment method was designed to achieve CO2 removal and H2 purification from underground coal gasification syngas.The underground coal gasification syngas was treated by a secondary membrane separation unit to achieve the separation of CO2/H2 and CH4,and the decarbonized purified gas is obtained,where the CO2 content(mole fraction)is less than 3%.The energy consumption required for this membrane separation process is 0.297 kW·h/m3.The CO2/H2 mixture was treated by amine absorption method,and the research was conducted by the methods of formula solution screening,process optimization and check analysis.Finally,the product with H2 purity(mole fraction)≥99%is obtained.The energy consumption of the amine absorption method is 0.341 kW·h/m3.Using membrane separation + solvent absorption coupling treatment method to treat underground coal synthesis gas under complex working conditions,decarbonized purified gas,pure CO2 and industrial grade H2 can be obtained,greatly improving the economic value of the project and having great application potential.
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