Oxy-coal combustion kinetics and formation characteristics of pollutants based on TG-MS analysis

doi:10.11949/j.issn.0438-1157.20171038

Abstract

Abstract:

Oxy-fuel combustion is one of the most promising CO₂ capture technologies. The oxygen-enriched combustion of pulverized coal was simulated in a thermogravimetric analyzer coupled with a mass spectrometry (TG-MS) in order to understand the ignition model and the generation characteristics of pollutants during combustion. Bituminous and anthracite standard coals were selected as the samples. The tests were done with oxygen volume fractions of 21%, 30% and 50% with two kinds of atmospheres (O₂/Ar and O₂/CO₂). In the O₂/CO₂ atmosphere, both of the ignition temperature and burnout temperature were lower, the combustion rate was improved, the combustion time was shortened, and the combustion performance was much better. Based on the TG/DTG curves, the ignition models of pulverized coal were judged. It was showed that the heterogeneous ignition of pulverized coal happened in O₂/Ar atmosphere, while the homogeneous ignition occurred in O₂/CO₂ atmosphere. Also, the activation energy and pre-exponential factor of coal combustion were calculated by Coats-Redfern method. When the oxygen volume fraction was above 30%, the apparent activation energy of the anthracite coal combustion in O₂/CO₂ atmosphere was significantly lower than that in O₂/Ar atmosphere, indicating an obvious improvement in reactivity. In the same reaction conditions, the activation energy of bituminous coal was lower than that of anthracite coal, and the former was more prone to ignition and combustion, showing better combustion performance. In the atmosphere of O₂/CO₂, the generation of CO and volatile-NO was promoted, and the formation temperature was lower than in O₂/Ar atmosphere. Meanwhile, the abundant CO would lead to NO reduction reaction.

Key words: coal combustion, oxy-fuel combustion, kinetics, pollutants, TG-MS

摘要：

富氧燃烧是最具工业化前景的燃烧中碳捕集技术之一，为更深入掌握煤粉富氧燃烧的着火模式和污染物生成特性，本文构建了热重-质谱联用实验系统，以烟煤和无烟煤标准煤样为对象，针对3个不同的氧气体积分数：21%、30%和50%，研究了O₂/Ar和O₂/CO₂气氛下煤粉的富氧燃烧特性。结果表明，O₂/CO₂气氛下煤粉着火温度和燃尽温度均降低，燃烧速率提高，燃烧时间缩短；两种煤粉在O₂/Ar气氛下的燃烧都属于非均相着火，而富氧燃烧都属于均相着火模式；氧气体积分数在30%以上时，无烟煤O₂/CO₂燃烧的表观活化能明显低于O₂/Ar气氛，在相同工况下烟煤的表观活化能均低于无烟煤；O₂/CO₂气氛促进了CO和挥发分NO的逸出，生成温度均低于O₂/Ar气氛，CO会对NO起到还原作用。

关键词: 煤燃烧, 富氧燃烧, 动力学, 污染物, 热重-质谱联用

CLC Number:

TK16

LIU Qian, ZHONG Wenqi, SU Wei, BEN Haoxi. Oxy-coal combustion kinetics and formation characteristics of pollutants based on TG-MS analysis[J]. CIESC Journal, 2018, 69(1): 523-530.

刘倩, 钟文琪, 苏伟, 贲昊玺. 基于热重-质谱联用的煤粉富氧燃烧动力学及污染物生成特性[J]. 化工学报, 2018, 69(1): 523-530.

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