活性比表面积和灰成分对半焦在混合气氛中气化竞争和抑制机理的影响

Coal gasification is the core technology of clean and efficient coal utilization, and has already been widely applied to industrial production. Char gasification is the main process of coal gasification. However, reaction mechanisms of char gasification are not yet clear. Especially, when char is gasified in the mixture of H2O, CO2, H2 and CO, the competition mechanisms of char gasification and the inhibition effects between char-H2O and char-CO2 reactions are still controversial. Char properties are considered as the main reason leading to controversial experimental results. This proposal will focus on the char properties which are most related to gasification reaction process. The char samples have different specific active surface area and ash composition will be prepared. The experimental gasification reaction rates will be compared with those calculated from controversial kinetic models to validate the reaction mechanism, and the gasification reaction rates of different H2O and CO2 ratio will also be compared to validate the inhibition reaction. By these means, the influences of active surface area, alkali, alkaline earth and transition metal on competition mechanisms of char gasification and inhibition effects between char-H2O and char-CO2 reactions will be deeply investigated. And the controversies on char gasification mechanisms and inhibition effects will also be clarified. Besides, a general reaction rate model which is suitable for char gasification in complex atmosphere will be established. The research results will provide help for design and optimization of gasifier, development of new gasification technology, and simulation of coal gasification.

煤气化作为煤炭高效清洁利用的核心技术已实现工业规模化应用。而半焦气化作为煤气化的主要反应过程，其反应机理仍不清楚。尤其是半焦在H2O，CO2，H2和CO多元混合气氛下的气化机理以及半焦-H2O和半焦-CO2反应间的相互抑制效应尚存在较大争议。而半焦性质被认为是引起争议的主要原因。本课题将从与气化反应关系最紧密的半焦性质入手，通过制备具有不同活性比表面积和灰成分的半焦，采用实验与争议模型气化速率对比，以及抑制反应气化速率对比的方法，深入研究半焦活性比表面积、灰分和灰成分中碱金属、碱土金属、过渡金属对半焦在多元混合气氛下气化机理及气化反应间相互抑制效应的影响，澄清现存的半焦在多元混合气氛下气化机理及气化反应间相互抑制效应的争议。通过找出影响半焦气化机理的本质因素，建立半焦在多元混合气氛下的通用气化速率模型。本课题的研究成果将为气化炉的设计与优化、新气化工艺的开发和煤气化过程的模拟提供理论依据。

半焦在多元混合气氛下气化机理研究的滞后直接限制了气化技术的进步，导致无法建立通用的半焦在多元混合气氛下的气化速率模型，进而导致无法针对气化过程开展精确的数值模拟。目前，半焦在H2O、CO2、H2、CO混合气氛下的气化机理尚存在很大的争议，而半焦性质被认为是产生争议的主要原因。本项目重点研究了半焦的活性比表面积和灰成分对半焦在H2O、CO2、H2、CO混合气氛下气化机理的影响。研究结果表明，半焦的气化机理与半焦表面反应活性位的饱和度有关，而半焦的反应活性位数量又与活性比表面积、灰分和灰成分有关。活性比表面积较大、催化灰成分含量较多的半焦的活性反应位也较多。随着半焦活性位数量的增加，半焦的气化机理会从共用活性位机理逐步转化为不共用活性位机理。因此，共用活性位机理和不共用活性位机理在本质上是统一的，只是活性位饱和和空余时的两种极端情况。根据这一理论，提出了统一气化机理，并根据吸附-脱附理论推导出了相应的统一气化机理模型，实验验证结果表明统一气化机理模型准确度更好。本项目的研究成果对煤气化或半焦气化的数值模拟提供了理论指导，以提高模拟的精度。

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