Enhancement of Biochar Gasification in Alkali Hydrothermal Medium by Passivation of Inorganic Components Using Ca(OH)2
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- 作者：Hema Ramsurn ; Sandeep Kumar ; Ram B. Gupta
- 刊名：Energy & Fuels
- 出版年：2011
- 出版时间：May 19, 2011
- 年：2011
- 卷：25
- 期：5
- 页码：2389-2398
- 全文大小：1038K
- 年卷期：v.25,no.5(May 19, 2011)
- ISSN：1520-5029
文摘
The challenges with thermal gasification of biomass to produce syngas include high transportation and drying costs of biomass and the need for high-temperature (700鈥?000 掳C) gasifiers and conditioning of the produced gases. Some of these challenges can be addressed by first converting biomass into high-energy-density biochar before transportation and then hydrothermal gasification of biochar at the site of the Fischer鈥揟ropsch plant for liquid fuel synthesis. In this work, a high-energy-density (>27 MJ/kg) biochar is first produced via hydrothermal carbonization of switchgrass at 300 掳C, and then the biochar is gasified in hydrothermal medium at 400鈥?50 掳C. The carbon gasification efficiency in hydrothermal medium is much better than that in the thermal medium. For example, at 550 掳C, only 5.9% carbon gasification was achieved in the thermal medium, as compared to 23.8% in hydrothermal medium. The addition of 25 wt % K2CO3 catalyst enhances the hydrothermal gasification to 43.8%. The gasification can be further enhanced if the biochar is passivated with a small amount of Ca(OH)2 when producing from biomass. With the use of Ca(OH)2 passivation during hydrothermal carbonization and the use of K2CO3 catalysis during hydrothermal gasification, a high carbon gasification efficiency of 75% is achieved at 600 掳C, using short reaction times of 5 and 30 min, respectively. With the recycle of the alkali catalyst and passivation agent, the hydrothermal process can provide an attractive alternative to thermal gasification.