生物质气化合成二甲醚系统的火用分析

Exergy analysis of dimethyl ether synthesis via biomass gasification

基于生物质串行流化床气化合成二甲醚（DME）系统的Aspen Plus模拟，对系统进行热力学火用分析，研究了气化反应参数与合成反应参数对各子系统和总系统的火用效率影响．研究结果显示：火用损失主要发生在气化子系统中；气化产物氢碳摩尔比在2左右时，系统火用效率可达到最大；液化子系统提高气化合成二甲醚一步反应的有效转化率，降低循环气份额，可有效提高系统火用效率；全系统的火用损失主要是由过程的不可逆性引起的，内部火用损率近80％．对于稻秸气化一步法合成二甲醚系统，适宜的气化温度为750～800℃，水蒸气生物质质量比为0．3；在合成温度为260～280℃，合成压力为4．0～4．5 MPa的条件下，系统的二甲醚产率可达到6．20 mol/kg，火用效率达到51．66％．

Based on the simulation of dimethyl ether （DME）synthesis from biomass gasification in interconnected fluidized beds using Aspen Plus,the exergy analysis of the DME synthesis system is performed.And the effects of operation parameters on the exergy efficiencies are studied.The re-sults show that the most exergy loss occurs in the gasification subsystem,and the system can reach the maximum exergy efficiency when the H2/CO molar ratio is about 2 .It is beneficial for the exer-gy efficiency of the liquefaction subsystem to improve conversion of syngas to DME by one-step and reduce the recycle gas ratio.In addition,the exergy loss of the whole system is mainly caused by the process irreversibility,and the internal exergy loss accounts for nearly 80% of all exergy loss.It is suggested that for the purpose of DME production,the operation parameters be controlled at a gasifica-tion temperature of 750 to 800 ℃,a steam and biomass ratio of 0.3,the liquefaction temperature of 260 to 280℃,and the liquefaction pressure of 4.0 to 4.5 MPa.And with the above-mentioned condi-tions,the yield of DME can reach 6.20 mol/kg and the total exergy efficiency can reach 51.66%.