用于煤制天然气的气化-热解耦合系统模拟研究及能量分析(英文)

Modelling and energy analysis of an integrated coal gasification and pyrolysis system for synthetic natural gas

大规模煤制天然气系统中气流床气化是一种重要且富吸引力的技术。对一种气流床气化-热解耦合系统进行了研究。该系统中气化炉分为两段：主要进行煤焦气化的气化段以及主要发生煤热解的热解段。采用流程模拟方法建立了耦合系统模型并与煤气化废锅系统进行了比较。同时,考察了操作条件对耦合系统气化性能的影响,提出了优化的操作条件。结果显示,气化温度1400℃时,耦合系统优化的蒸汽煤比为250~300 kg（steam）·t-1（dry coal）。耦合系统的冷煤气效率为88.18%,高于气化废锅系统（84.14%）,且其消耗指标均有所降低。但耦合系统的气化性能受到热解段焦油和CH4产率很大的影响。耦合系统总体能量利用效率为92.26%,略低于气化废锅系统（93.39%）,但其火用效率比气化废锅系统高2.2%。这说明通过热解-气化的耦合方式能够有效回收气化高温合成气中的显热并提高其能量品位。

The entrained-flow coal gasification is an important and attractive technology in large scale coal-based synthetic natural gas （SNG） process. In this study, an integrated entrained-flow coal gasification and pyrolysis system is proposed and investigated. The gasifier is divided into two stages in this system： one is mainly for the gasification of char and the other is mainly for the coal pyrolysis. The integrated system is studied by using a process simulation model and compared with a coal gasification system with the radiant and convective coolers. The effects of the operating conditions on the gasification performance are studied and the optimized operating conditions are obtained. It is found that the optimized steam coal ratio of the integrated system is about 250 - 300 kg（ steam）/t （dry coal） while the gasification temperature is 1 400 ~C. The cold gas efficiency of 88. 18% of the integrated system is higher than that of 84.14% of the gasification and radiant＋conductive cooler system. The coal and O2 consumptions are relative low in the integrated system. The performance of the integrated system is highly related to the yield of tar and CH4 in the pyrolysis stage. The overall energy conversion efficiency of the integrated system （92.26%） is slightly lower than that of the gasification and radiant＋conductive cooler system （93.39%）. However, the exergy efficiency is enhanced by more than 2.2% in the integrated system. The integration of the gasification and pyrolysis can effectively recover and promote energy grade of the sensitive heat in the hot syngas.