Multi-technique integration separation frameworks after steam reforming for coal-based hydrogen generation
Xuehua Ruan, Wenbo Huo, Jiaming Wang, Minggang Guo, Wenji Zheng, Yun Zou, Aibin Huang, Jianxiang Shou, Gaohong He
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Coal-based H2 generation has abruptly increased in recent years. The PSA-VPSA-SC process is the matured and standard framework for H2 purification and CO2 capture in many existing plants, including normal and vacuum pressure swing adsorption units in series (PSA-VPSA), and shallow condensation unit (SC). However, this standard process is frequently subjected to low H2 recovery ratio and high purification cost. In this work, H2-selective and CO2-selective membrane units, i.e., HM and CO2M, are attempted to support the standard process and ameliorate constraints. In the beginning, HM unit is arranged after VPSA to enhance H2 recovery from the decarbonized stream, i.e., the PSA-VPSA-SC/HM process. As a result, H2 recovery ratio can be enhanced significantly from 83% to 98%. In the following, VPSA is replaced with CO2M unit to reduce investment and operation cost, i.e., the PSA-CO2M-SC/HM process. Accordingly, the specific purification cost is diminished from 33.46 to 32.02 USD·(103m3 H2)-1, saved by 4.3%, meanwhile the construction cost is falling back and just a little higher than that for the standard process. In the end, another CO2M unit is launched before PSA, i.e., the CO2M-PSA-CO2M-SC/HM process, which could unbundle CO2 enrichment partially from H2 purification, and then save more investment and operation cost. In comparison with the standard process, this ultimate retrofitted process can be superior in all the three crucial indices, i.e., recovery ratio, investment, and specific purification cost. On the whole, coal-based H2 generation can be ameliorated significantly through high efficient H2-selective and CO2-selective membrane units.