含碳基质高温气化过程固体结构演变及反应机理的原位研究

The evolution of solid physicochemical structures in coal and other carbonaceous matrix gasification process seriously affects gasification reaction mechanism and operation efficiency of gasification units. However, in-situ studies on solid structure evolution during gasification have been rarely conducted, and there was no consistent conclusion about the key structural influence factor of gasification. Hence, this project is aimed at carrying out in-situ analysis of particle fragmentation behaviors inside entrained flow gasifier using visualization technologies and revealing particle fragmentation mechanism inside gasifier by characterizing solid physicochemical structures. Moreover, the distribution characteristics of gasified semi-char with different conversions inside gasifier will be explored. This project will also in-situ study the influence of pyrolysis/gasification conditions and raw material properties on char-ash/slag transition, carbon structure evolution and mineral matter transformation during different stages of high-temperature gasification of coal and other carbonaceous matrix. Additionally, this project will focus on correlating solid structure evolution during gasification and gasification reactivity so as to explore the key structural influence factor of gasification, reveal high-temperature gasification mechanism and establish high-temperature gasification kinetic model with structural parameters. This project will be conducive to deepening the basic understanding of high-temperature gasification process of coal and other carbonaceous matrix, and providing theoretical support for the optimization design and high-efficiency operation of industrial entrained flow gasifiers.

煤等含碳基质气化过程固体物理化学结构演变深刻影响气化反应机理和气化装置运行效率，但目前关于气化过程中固体结构演变的原位研究极少，且对气化反应关键结构影响因素尚无统一结论。因此本项目拟基于可视化技术原位研究气流床气化炉内颗粒破碎行为，通过固体物化结构表征揭示气化炉内颗粒破碎机理，并考察不同转化率气化半焦颗粒的炉内分布特性；基于原位技术考察热解/气化条件和原料性质对煤等含碳基质高温气化过程不同反应阶段焦-灰/渣转变、碳结构演变和矿物质转化的影响；基于对气化过程固体结构演变和气化反应性的关联，探讨高温气化过程关键结构影响因素，揭示高温气化反应机理，建立带结构参数的高温气化反应动力学模型。本项目有助于加深对煤等固体含碳基质高温气化反应过程的基础认识，为工业气流床气化炉的优化设计和高效运行提供理论支撑。

本项目基于原位技术开展了气化炉内颗粒群热态行为和气化过程固体结构演变实验研究，阐明了气化炉内颗粒破碎机理和气化过程固体结构原位演变规律，揭示了原位结构演变对煤气化反应机理的影响机制。(1) 开展了撞击流气流床水煤浆气化炉内颗粒群热态行为原位研究。射流回流区和撞击流股区不同轴向区域中颗粒粒径主要分布于225-475μm区间范围，撞击流股区中颗粒平均直径和颗粒浓度更小，射流回流区中颗粒空间分布更加均匀。随颗粒沿气化炉轴向向下运动过程中，撞击流股区中颗粒出现频率增加。(2) 开展了煤热解过程固体结构演变的原位研究。水溶性和离子交换性碱及碱土金属(AAEMs)促进煤热解过程烷基取代基和芳环系统之间键的断裂和成键。固有的AAEMs促进碳晶体结构的小型化从而形成碳结构无序的煤焦。(3) 开展了煤焦气化过程固体结构演变的原位研究。煤焦的石墨化程度随碳转化率增大而逐渐增加。水溶性和离子交换性AAEMs均抑制了碳结构的有序演化而加速煤焦气化。钠-钙复合催化剂催化煤焦气化过程，钙优先与煤中的硅物质发生反应，该过程抑制了钠的失活从而提高整体催化效率。(4) 开展了煤焦气化反应特性与固体结构演变的原位耦合研究。煤焦气化反应性指数R0.5与原位碳结构参数ID1/IG呈正相关，热重气化的R0.5和高温热台气化的R0.5与原位ID1/IG值线性拟合的相关系数R2分别为0.82和0.98，原位ID1/IG值可以很好地预测单颗粒煤焦的气化反应性。(5) 开展了煤热解及焦气化反应动力学模型化研究。根据分布活化能模型(DAEM)，SF煤热解活化能Ea呈现双峰分布，酸洗脱矿使Ea分布更集中。分布活化能模型(DAEM)和随机孔模型(RPM)可分别描述原煤焦和脱矿煤焦的气化特性。