生物质主要组分对共热解焦理化结构与气化特性的影响机制

Co-pyrolysis of coal and biomass is the initial step of thermal chemical conversion, and the features of co-pyrolysis products have a significant influence on the subsequent reaction, such as the gasification or combustion of co-pyrolysis char. Due to the diversification of biomass, conflicting conclusions on physicochemical structure and gasification performance are obtained, which make it difficult to control the products quality of co-pyrolysis directly. Thus, in this proposal, we propose that based on the perspective of main components, and explore the influencing mechanism of cellulose, hemicellulose, lignin and typical biomass on physicochemical structure and gasification performance of the co-pyrolysis char. Firstly, from the statistical self-similarity and scaling invariance of the co-pyrolysis char surface morphology, based on the fractal theory, the effects of biomass and its components on the physical complexity and irregular degree, such as pore characteristics, surface morphology are to be investigated. The generation mechanism of co-pyrolysis char crystalline structure is to be analyzed through spectrum fitting analysis. Thus, the evolution mechanism of complex surface morphology and irregular space structure is to be obtained. Secondly, the influence mechanism of oxygen center free radical and aromatic free radical on the distribution of surface functional groups is to be investigated, and the changing rule of co-pyrolysis char chemical structure is to be obtained. Then the gasification performance of co-pyrolysis char is to be investigated. And we focus on the interaction between organic and inorganic alkali-metal in biomass with alum inosilicate in coal, and the correlation between physicochemical structure parameters (fractal dimension, etc.) and gasification parameters. This proposal will provide new ideas on the prediction of physicochemical structure and gasification performance of co-pyrolysis char, also provide theoretical support for product quality control from cooperative utilization of coal and biomass.

共热解是煤与生物质热化学转化的关键步骤，其产物特性显著影响共热解焦气化或燃烧等后续反应的进行。生物质多样化带来共热解焦理化结构变化各异，致使产物品质难以定向调控。为此，本项目提出从生物质主要组分出发，探索纤维素、半纤维素、木质素及典型生物质对共热解焦理化结构与气化特性的影响机制。首先，从共热解焦表面统计自相似性和标度不变性出发，采用分形理论研究表面形貌及孔隙特性的定量变化规律；通过谱图拟合阐释微晶结构生成机制，进而揭示共热解焦的复杂表面及不规则空间结构演变机理；其次，从自由基视角出发，探讨以氧原子为中心的自由基及芳烃自由基对共热解焦的表面官能团分布影响规律，阐明其化学结构变化机理；研究共热解焦气化特性，揭示生物质中碱金属与煤中硅铝酸盐的交互作用及分形维数等理化结构参数与气化特性的内在联系。本课题将为共热解焦理化结构及气化特性预测提供新思路，为煤与生物质协同利用的产物品质调控提供基础理论。

煤与生物质共热解是其他热化学转化（如共燃烧、共气化）的关键初始步骤，其产物特性显著影响共热解焦的燃烧或气化等后续反应的进行。生物质的加入会改变共热解焦的理化结构（如表面形貌、孔隙特性、微晶结构及表面官能团分布等），进而影响其反应特性。生物质多样化带来共热解焦理化结构变化各异，致使产物品质难以定向调控。为此，本项目提出从生物质主要组分出发，探索纤维素、半纤维素、木质素及典型生物质对共热解焦理化结构与气化特性的影响机制。从共热解焦表面统计自相似性和标度不变性出发，基于分形理论通过分形维数得到了表面形貌及孔隙特性的定量变化规律，共热解焦比表面积与孔隙表面分形维数呈指数关系；通过谱图拟合阐释纤维素、半纤维素及木质素对共热解焦微晶结构生成影响机制；纤维素促进了共热解焦微晶结构的有序性，而有机钠盐则降低了共热解焦样的有序性，典型生物质小麦秸秆与烟煤共热解焦微晶结构的有序性与生物质掺混比例呈二次曲线关系。初步明确共热解焦持久稳定自由基变化规律，得到共热解焦气化特性并揭示理化结构参数与气化特性的内在联系，共热解焦的气化反应行为特性参数与焦样微晶结构特性参数存在指数关系。揭示生物质对共热解焦理化结构与反应特性的影响机制有助于指导煤与生物质共热解产物品质调控，对煤炭分质转化及产物梯级利用的过程设计和优化意义重大。