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论文类型：期刊论文

发表时间：2011-11-01

发表刊物：ENERGY & FUELS

收录刊物：Scopus、SCIE、EI

卷号：25

期号：11

页面范围：5242-5249

ISSN号：0887-0624

摘要：A new two-stage gasification process, consisting of a fluidized-bed (FB) pyrolyzer and a downdraft fixed-bed (DFB) gasifier, has been proposed to gasify powder coal for fuel gas production with low tar generation. Aiming at developing the new technology, this paper investigated the means for coal pyrolysis gas upgrading, with the focus on tar removal by both thermal cracking with or without the presence of oxygen and catalytic cracking or reforming over a char bed in a fixed-bed reactor downstream of a FB coal pyrolyzer. The presence of oxygen and the adoption of a char bed evidently facilitated the tar removal performance and also improved the produced fuel gas quality. Analyzing the tar sample collected at the outlet of the tar removal reactor with gas chromatography-mass spectrometry (GC-MS) clarified that the oxidation by O(2) and the char-catalyzed reforming both exhibited certain selectivity to the tar-containing chemical species. In addition, the property of char played an important role on its catalytic activity. The higher the specific surface area, the better the activity of char for removing tar. The spent char showed a much reduced specific surface area of micropores but evidently elevated the specific surface area of mesopores, even by up to 3 times. The tests with the metal oxides impregnated onto the demineralized char demonstrated that both Ca and Fe oxides enabled better catalytic activity for tar removal than Na and Mg oxides. This study clarified as well that the viable operating conditions for tar removal in a char bed were at 1100 degrees C with an excessive air ratio (ER) of 0.04 and gas residence time above 1.3 s.