Indirect coal combustion can solve some problems such as low efficiency and air pollution during traditional coal combustion, this research investigates energy release characteristics of indirect combustion and aims to achieve maximum energy utilisation. Firstly, Energy Utilization Diagrams Methodology was used to explore exergy cascade release pathways and exergy losses for typical indirect combustion such as supercritical water gasification re-combustion, steam reforming re-combustion, and chemical-looping combustion, which are compared with direct combustion. It is pointed out that indirect combustion has changed release pathways of chemical exergy, and decreased energy level difference between chemical exergy in fuel and thermal energy in combustion, then exergy losses is reduced and exergy in fuel is released step by step. Secondly, to prove that indirect combustion can indeed reduce exergy losses and improve exergy efficiency in the combustion process, supercritical water gasification re-combustion with least exergy losses was selected and exergy analysis model was established by energy quality coefficient. Results show that thermal efficiency and exergy efficiency of supercritical water gasification re-combustion reaches as high as 94.8% and 79.5%, respectively, 2.23% and 19.61% higher than those of traditional coal-fired boilers. As a result, energy matching and conversion are more reasonable in indirect coal combustion processes.

中文翻译：

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典型间接煤燃烧过程的火用级联释放途径和火用效率分析

煤炭间接燃烧可以解决传统煤炭燃烧效率低、空气污染等问题，本研究研究了间接燃烧的能量释放特性，旨在实现能源的最大利用。首先，利用能量利用图法，探索了超临界水气化再燃烧、蒸汽重整再燃烧、化学循环燃烧等典型间接燃烧与直接燃烧相比的火用级联释放途径和火用损失。指出间接燃烧改变了化学火用的释放途径，减小了燃料中化学火用与燃烧热能之间的能级差，从而减少了火用损失，逐步释放了燃料中的火用。第二，为证明间接燃烧确实能减少燃烧过程中的火用损失，提高火用效率，选择了火用损失最小的超临界水气化再燃烧，并利用能质系数建立了火用分析模型。结果表明，超临界水气化再燃烧的热效率和火用效率分别高达94.8%和79.5%，比传统燃煤锅炉高2.23%和19.61%。因此，在间接煤燃烧过程中，能量匹配和转换更加合理。选择火用损失最小的超临界水气化再燃烧，利用能量质量系数建立火用分析模型。结果表明，超临界水气化再燃烧的热效率和火用效率分别高达94.8%和79.5%，比传统燃煤锅炉高2.23%和19.61%。因此，在间接煤燃烧过程中，能量匹配和转换更加合理。选择火用损失最小的超临界水气化再燃烧，利用能量质量系数建立火用分析模型。结果表明，超临界水气化再燃烧的热效率和火用效率分别高达94.8%和79.5%，比传统燃煤锅炉高2.23%和19.61%。因此，在间接煤燃烧过程中，能量匹配和转换更加合理。