煤与生物质共热解过程中的交互作用及机制研究

Co-pyrolysis of coal and biomass is one of the clean and effective utilization routes of coal and biomass. However, the information lack of initial in-situ pyrolysis products (tar plus gases) and insufficient understanding on the interaction mechanism during the co-pyrolysis process restrict their industrial application. To detect and analyze the initial pyrolysis products, in this project, a self-designed novel in-situ pyrolysis time-of-flight mass spectrometry coupled with electron impact/vacuum ultraviolet photoionization (Py-EI/VUVPI-TOFMS) is employed to systematically investigate the co-pyrolysis characteristics of coal and biomass. The kinds and contents of the initial pyrolysis products from the individual pyrolysis or co-pyrolysis of low-rank with different biomass, the constituents of biomass (cellulose, hemicellulose and lignin) and model compounds are studied and the effects of co-pyrolysis conditions on the formation of the initial volatiles are examined. By this way, we can acquire the production behaviors of the initial pyrolysis products and co-pyrolysis characteristics. Through the control of the secondary reaction of the initial pyrolysis products and the combination of the stable pyrolysis products obtained on the fixed-bed reactor with the initial co-pyrolysis products from the Py-EI/VUVPI-TOFMS, the formation and evolution processes of the initial products and their interaction mechanism during the co-pyrolysis of coal and biomass are obtained. The prospective results of this project will provide a novel method to analyze and detect the in-situ initial pyrolysis products of co-pyrolysis of coal and biomass, and give a guide to regulate the pyrolysis products distribution as well as the control of the co-pyrolysis process, which is helpful for industrial co-utilization of coal and biomass.

煤与生物质共热解是实现两者清洁高效利用的重要途径之一。本项目针对目前共热解过程交互作用机制认识不足的现状，从分析认识热解初级产物（气体和焦油）入手，利用自行设计建立的新型原位热解-电子轰击/真空紫外单光子双电离与飞行时间质谱，系统研究中低阶煤与生物质、生物质主要组分及模型化合物的单独热解、共热解过程初级产物种类和含量的变化规律，考察不同共热解过程参数对热解挥发物的影响，获得热解过程初级产物的逸出行为和共热解特性；通过对热解初级产物的二次反应调控并结合固定床热解稳态产物分析，认识共热解过程中初级产物的演化规律，获得煤与生物质共热解过程中的交互作用及机制。该项目的开展，不仅提供了一种原位分析煤与生物质共热解初级产物的方法，也为煤与生物质共利用过程调控产物分布和过程控制提供理论基础，推动煤和生物质共利用技术的发展。

针对煤与生物质共热解过程交互作用机制认识不足问题，利用建立的新型原位热解-真空紫外单光子/电子轰击双电离与飞行时间质谱（Py-VUVPI/EI-TOFMS）研究煤、生物质及其基本组分（纤维素、半纤维素和木质素）单独热解及共热解初级产物产生行为和交互作用，揭示了木质素及煤热解过程初级产物的逸出特征和二次演化行为及共热解过程中的交互作用。利用红外快速加热固定床反应器获得过程参数和原料中碱/碱土金属（AAEM）对共热解影响规律，阐述了共热解过程的作用规律和交互机制。.热重结果显示，共热解存在协同作用，但协同效应与生物质和煤种类有关。建立的Py-EI/VUVPI-TOFMS可实现热解初级产物及活性自由基的原位检测。柏木热解初级挥发物在石英砂作用下发生二次反应，愈创木酚类物质发生脱甲基、脱甲氧基或缩聚反应等，而脂肪类自由基经历重组、环化等反应生成呋喃类物质，揭示了木质素随热解温度发生R-O-R醚键断裂、愈创木酚类物质脱甲基/脱甲氧基、脱羟基重组反应及缩聚生成大分子芳香自由基机理。生物质各组分共热解过程发生交互作用，其中木质素的存在促使大分子多环物质生成，而木聚糖与纤维素共热解则促进长链脂肪类、呋喃类物质及含脂肪类自由基半焦生成。淖毛湖煤热解初级挥发物在石英砂作用下发生C-C键断裂、环化、缩聚反应等。共热解初级热解产物的种类较单独热解变化较小，但部分物质含量变化证实共热解过程的交互作用。.过程参数（升温速率、热解温度、混合比例和混合方式）和原料中固有AAEM显著影响煤与生物质共热解交互作用。与机械混合相比，煤/生物质分层放置为热解挥发物间交互作用提供有效反应空间，生物质热解生成的富氢组分发挥供氢作用，提高共热解焦油产率和焦油中3-4环芳香化合物含量。共热解过程促进柏木热解生成的小分子自由基与淖毛湖煤热解生成的双环芳香化合物交互作用。淖毛湖煤和柏木中固有AAEM脱除进一步提升共热解过程的交互作用，提高焦油产率和焦油中单环和双环芳香化合物含量增加。这为生物质/煤共热解协同作用发挥、产物的有效调控及反应器设计等提供重要的理论指导。