生物质气化制备燃气过程的[火用]分析

Exergy Analysis on Gas Production from Biomass Gasification

采用单一流化床两步气化方法,以煤作为热载体与发热体,水蒸气作为气化介质,在流化床热态装置上对生物质气化制取燃气进行了研究,探讨了反应温度和水蒸气与生物质的质量比u对燃气分布、化学、物理、效率和未反应碳剩余率等的影响。在测试条件下,燃气化学为10 832.13~16 510.54 kJ/kg,物理为685.05~1 146.71 kJ/kg,化学/物理比为13.5~17.7,效率为35.52%~60.78%。结果表明,H2和CO是对燃气贡献最大的两种气体,H2和CO值之和随温度升高而增加,随u的增加先增加,后呈现下降趋势。随着反应温度升高,燃气化学、物理和效率均增加,而化学/物理比、未反应碳效率及剩余率减小。适量水蒸气的加入,有利于燃气及效率的增加,但是较高的u会导致未反应碳剩余率的增加。一个最佳的u应该在1.2与1.6之间被选取。

Biomass gasification was performed on a fluidized bed reactor with steam as gasifying agent.Two-stage gasification processes in a fluidized bed were adopted.This research aimed to determine the effects of reaction temperature and steam-to-biomass ratio( u) on exergy distribution,chemical exergy,physical exergy and exergy efficiency of the product gas,and residual ratio and exergy efficiency of the unreacted carbon,etc.Over the ranges of the test conditions used,chemical exergy varied from10 832.13 kJ/kg to 16 510.54 kJ/kg,physical exergy ranged between 685.05 kJ/kg and 1 146.71 kJ/kg chemical exergy/physical exergy ratio varied from 13.5 to 17.7,and exergy efficiency of product gas ranged between 35.52% and 60.78%.The results showed that the top two contributions of gas component to exergy value were H2and CO.With the increase of reaction temperature,chemical exergy,physical exergy and exergy efficiency of the product gas increased,whilst chemical exergy/physical exergy ratio,and residual ratio and exergy efficiency of the unreacted carbon decreased correspondingly.The exergy value and efficiency of the product gas first increased and then decreased with the increase in u.An optimal value of u should be chosen between 1.2 and 1.6.