同位素示踪法研究富氢气体调控煤热解产物组成的机制

The coal pyrolysis-based staged conversion technology is an effective method to realize clean and efficient utilization of low rank coal. The composition of coal pyrolysis products can be regulated by hydrogen-rich atmosphere. Understanding regulatory mechanism of products can promote process optimization and industrialization. To this end, this proposal intends to study the mechanism of composition of coal pyrolysis products regulated by hydrogen-rich atmosphere (coke oven gas and hydrogen-rich atmosphere produced from methane catalytic activation) using isotope tracer method. Firstly, the structure of raw coal, coal macerals and macromolecular clusters in coal will be studied, to reveal coal composition and structural characteristics. Secondly, coal pyrolysis behaviors at different simulated coke oven gas atmospheres, and the distribution of deuterium in coal pyrolysis products when D2 and CD4 as tracer will be studied, to understand the role of methane in coal pyrolysis at low-medium pyrolysis temperature (400~700℃), and to clarify synergism between coke oven gas components. Finally, the effect of process parameters on tar yield and quality, and the distribution of deuterium and carbon-13 in tar when CD4 and 13CH4 as tracer will be investigated during the integrated process of coal pyrolysis with methane catalytic activation, to clarify formation regularity and regulatory mechanism of tar formation, and to build the relationship between the amount of CH3 radical involved in tar formation and tar yield and quality. It can be expected that the results of the project will provide theoretical guidance for development of coal pyrolysis technology with high tar yield and quality.

以煤热解为基础的煤炭分级转化利用技术是实现低阶煤清洁高效利用的有效手段。富氢气体可调控煤热解产物组成，深入认识这一过程中产物的调控机制可有效促进工艺的优化及其产业化。为此本项目提出利用同位素示踪法研究富氢气体（焦炉气和甲烷催化活化产生的富氢气体）调控煤热解产物组成的机制。通过对原煤、显微组分和煤中大分子团簇的结构解析，认识煤的组成和结构特征。通过研究煤在不同模拟焦炉气气氛下的热解特性及D2和CD4为示踪剂时氘在产物中的分布，认识CH4在煤中低温热解阶段（400~700℃）的作用，并阐明焦炉气组分之间的协同作用机制。通过研究甲烷催化活化与煤热解耦合过程工艺参数对焦油收率和品质的影响及CD4和13CH4为示踪剂时氘和碳-13在焦油中的分布，阐明焦油的形成规律和调控机制，并构建CHx自由基对焦油的贡献与焦油收率和品质之间的定量关系。项目成果可为发展具有高焦油收率和品质的煤热解工艺提供理论指导。

在我国“双碳”目标的大背景下，煤热解要走向工业化运行的关键目标是要提高能源的转化效率，增加焦油产率，降低能耗成本。在煤热解过程中引入•CHx、•H等自由基是增加焦油产率的有效途径，但加氢热解技术成本高昂，因此，为了寻找更为廉价氢源，认识富氢气体在煤热解过程中富氢气体调控热解产物组成的机制是十分必要的。本项目首先研究了煤的组成结构特征。其次研究了甲烷在煤中低温阶段的作用发现，当温度高于600℃时，甲烷可以为煤热解自由基提供氢和CHx 自由基，参与到煤热解自由基的稳定和初级挥发分的二次反应。利用同位素示踪法研究了氢气在煤热解过程中的作用发现，煤在被加热至200℃时，H2便能与煤中的稳定自由基发生反应；在煤加氢热解过程中，能够诱导氢气离解的活性自由基促进了焦油的形成，一些非挥发性自由基可以从H2中夺取氢原子。同时利用同位素示踪法研究了焦炉气组分之间的协同作用发现，氢气和甲烷之间存在协同作用，甲烷促进了氢气与煤的反应。最后研究富氢气体催化活化过程调控煤热解产物组成的机制发现，活化的氢气更容易与煤热解自由基反应。项目实施可为发展具有高焦油收率和品质的煤热解工艺提供理论指导。