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Auto-Gasification of a Biofuel

机译:自动气化生物燃料

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摘要

A novel mechanism for gasifying a char is described. For thermally large particles (i.e., Bi > 0.1) the temperature distribution is non-uniform. Because different temperature regimes exist in the particle, the stages of drying, devolatilization (or pyrolysis), and reaction of the char may overlap. At some point the particle's surface is fully devolatilized, while the particle's interior is still undergoing drying and devolatilization. As H_2O and CO_2 flow out from the particle they pass through the hot surface layers of char. If the temperature is high enough, the char may be gasified. Black liquor was used here as a sample fuel. It has desirable properties for such auto-gasification; thermally large particles, a high initial water-content and a very porous and highly reactive char. Detailed numerical simulations suggest that 30 to 40% of the char may be converted simultaneously with devolatilization by auto-gasification. The larger the particle and the higher the temperature, the larger is the fraction of char gasified. For coal and peat, a typical particle size is too small for this mechanism to play any role when fired in pulverized fuel or fluidized bed furnaces. For burning wooden logs, the particle size is large and the pyrolysis time is ≈ 10 min., so then auto-gasification might be important.
机译:描述了一种用于气化焦炭的新颖机制。对于较大的热粒子(即Bi> 0.1),温度分布不均匀。由于颗粒中存在不同的温度范围,因此干燥,脱挥发分(或热解)和炭反应的阶段可能会重叠。在某个时刻,粒子的表面已完全脱挥发分,而粒子的内部仍在干燥和脱挥发分。当H_2O和CO_2从颗粒中流出时,它们穿过炭的热表面层。如果温度足够高,炭可能会气化。黑液在这里用作样本燃料。对于这种自动气化,它具有理想的性能。热大颗粒,高初始水含量和非常多孔且高反应性的炭。详细的数值模拟表明,通过自动气化可以在脱挥发分的同时将30%至40%的焦炭转化。颗粒越大,温度越高,炭化气的比例越大。对于煤和泥煤,当在粉状燃料或流化床炉中燃烧时,典型的粒径太小,以至于该机理无法发挥任何作用。对于燃烧木原木,其粒径较大且热解时间约为10分钟,因此自动气化可能很重要。

著录项

  • 来源
    《Combustion and Flame》 |2002年第4期|p.357-370|共14页
  • 作者单位

    Helsinki University of Technology, Laboratory of Energy Engineering and Environmental Protection, P.O. Box 4400, Saehkoemiehentie 4, FIN-02015 HUT, Finland;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 燃料与燃烧;
  • 关键词

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