煤热解过程挥发分-焦交互作用的自由基反应机理

Free Radical Reaction Mechanism of Volatile-Char Interactions During Coal Pyrolysis

摘要

煤作为我国重要的一次能源，其热解特性对于煤粉高效热转化利用具有重要意义。煤热解过程中挥发分-焦间交互作用会显著影响焦炭的化学结构从而进一步改变反应特性及热解产物。煤中的持久性自由基作为煤化学结构的重要组成之一，其在热解过程中受焦-挥发分交互作用的影响机理值得进一步明晰。本文采用 EPR 原位检测方法，并结合 FT-IR，Raman 实验结果，研究了煤热解过程焦炭中自由基受挥发分-焦交互作用的影响机理。结果表明，挥发分-焦交互作用使煤热解焦中自由基含量（物质的量）显著降低 5.3%∼19.7%，且挥发分-焦交互作用主要影响了热解过程中简单芳香自由基与含脂肪侧链的芳香自由基的演化特性；煤焦含氧官能团、烃基、羟基官能团数量显著降低；热解温度由 500 ^∘C 升高到 700 ^∘C 时，挥发分-焦交互作用使煤热解焦大环/小环比升高了 3.3%∼11.1% 。

Abstract

As a crucial primary energy source in China，the pyrolysis characteristics of coal are of significant im-portance for its efficient thermal conversion and utilization.The volatile-char（V-C）interactions substantially influ-ence the chemical structure of char，thereby further altering the reaction characteristics and pyrolysis products.Per-sistent free radicals in coal are one of the essential components of its chemical structure，and the mechanism by which they are affected by V-C interactions during pyrolysis deserves further clarification.This study employs in-situ EPR，combined with FT-IR and Raman results，to investigate the influence mechanism.The results indicate that V-C interactions significantly reduce the free radical content in char by 5.3% to 19.7%.Furthermore，these interac-tions primarily affect the evolution characteristics of simple aromatic free radicals and aromatic free radicals with aliphatic side chains during pyrolysis.The quantities of oxygen-containing functional groups，hydrocarbon groups， and hydroxyl functional groups in coal char are notably reduced.When the pyrolysis temperature increases from 500^∘C to 700^∘C，V-C interactions cause the macrocyclic/microcyclic ratio in char to increase by 3.3% to 11.1%.

关键词

煤热解 / 自由基 / 交互作用

Key words

coal pyrolysis / free radicals / volatile-char interactions

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基金资助

国家重点研发计划资助项目(2022YFB4100600)