期刊
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
卷 48, 期 9, 页码 6975-6985出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.ijhydene.2022.03.205
关键词
Hydrogen; Pyrolysis; Gasification; Two-step gasification; Oxygen-steam
Research on hydrogen production from coal gasification focuses on the formation of CO and H2 from coal and water vapor. Pure oxygen-steam gasification is used to improve gasification efficiency. The two-step gasification process involving coal pyrolysis and char gasification is an efficient method for hydrogen production.
Research on hydrogen production from coal gasification is mainly focused on the forma-tion of CO and H2 from coal and water vapor in high-temperature environments. However, in the process of underground coal gasification, the water gas shift reaction of low -temperature steam will absorb a lot of heat, which makes it difficult to maintain the combustion of coal seams in the process of underground coal gasification. In order to obtain high-quality hydrogen, a pure oxygen-steam gasification process is used to improve the gasification efficiency. And as the gasification surface continues to recede, the drying, pyrolysis, gasification and combustion reactions of underground coal seams gradually occur. Direct coal gasification can't truly reflect the process of underground coal gasifica-tion. In order to simulate the hydrogen production laws of different coal types in the un-derground gasification process realistically, a two-step gasification process (pyrolysis of coal followed by gasification of the char) was proposed to process coal to produce hydrogen-rich gas. First, the effects of temperature and coal rank on product distribution were studied in the pyrolysis process. Then, the coal char at the final pyrolysis temperature of 900 degrees C was gasified with pure oxygen-steam. The results showed that, the hydrogen production of the three coal chars increased with the increase of temperature during the pyrolysis process, the hydrogen release from Inner Mongolia lignite and Xinjiang long flame coal have the same trend, and the bimodality is obvious. The hydrogen release in the first stage mainly comes from the dehydrogenation of the fat side chain, and the hydrogen release in the second stage mainly comes from the polycondensation reaction in the later stage of pyrolysis, and the pyrolysis process of coal contributes 15.81%-43.33% of hydrogen, as the coal rank increases, the hydrogen production rate gradually decreases. In the gasification process, the release of hydrogen mainly comes from the water gas shift reaction, the hydrogen output is mainly affected by the quality and carbon content of coal char. With the increase of coal rank, the hydrogen output gradually increases, mainly due to the increasing of coal coke yield and carbon content, The gasification process of coal char contributes 56.67-84.19% of hydrogen, in contrast, coal char gasification provides more hydrogen. The total effective gas output of the three coal chars is 0.53-0.81 m3/kg, the hydrogen output is 0.3-0.43 m3/kg, and the percentage of hydrogen is 53.08-56.60%. This study shows that two-step gasification under the condition of pure oxygen-steam gasification agent is an efficient energy process for hydrogen production from under-ground coal gasification.(c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
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