Multi-technique integration separation frameworks after steam reforming for coal-based hydrogen generation

Coal-based H-2 generation has abruptly increased in recent years. The PSA-VPSA-SC process is the matured and standard framework for H-2 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 H-2 recovery ratio and high purification cost. In this work, H-2-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 H-2 recovery from the decarbonized stream, i.e., the PSA-VPSA-SC/HM process. As a result, H-2 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.(10(3) m(3) H-2)(-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 H-2 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 H-2 generation can be ameliorated significantly through high efficient H-2-selective and CO2-selective membrane units. (C) 2021 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd. All rights reserved.

Automated summary

The study successfully improved the low H-2 recovery ratio and high purification cost issues in coal-based H-2 generation by utilizing H-2-selective and CO2-selective membrane units. Through the combination and replacement of different units, costs can be significantly reduced and hydrogen production efficiency can be increased.