Experimental study on the effect of pre-oxidation regulation on coal devolatilization and NOx emission during char combustion in O2/CO2/H2O atmosphere under pressurized conditions

IF 7.5 1区 工程技术 Q2 ENERGY & FUELS
Fuel Pub Date : 2025-10-08 DOI:10.1016/j.fuel.2025.136873
Chenxi Bai, Wenda Zhang, Kun Chen, Sicong Xu, Yukai Li, Yijun Zhao, Shaozeng Sun, Dongdong Feng
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Abstract

Pressurized oxy-fuel combustion is a potential carbon capture technology in coal-fired power generation. Pre-oxidation is an effective means to reduce NOx emissions during coal combustion. In this study, a pressurized horizontal furnace experimental system was used to explore the effects of pre-oxidation temperature (750–1000 °C), O2 concentration (0.5–10 %), gasifying agent and residence time (1–7 min) on the generation of CO, CO2, CH4 and NOx in the devolatilization stage of pulverized coal and the generation of NOx when char was burned in an O2/CO2/H2O atmosphere at 1.3 MPa. The contribution of the devolatilization the char combustion stage to NOx generation was comprehensively analyzed, and a pre-oxidation strategy suitable for pressurized oxy-fuel combustion NOx reduction was proposed. The results showed that pre-oxidation of pulverized coal at low oxygen concentration in the devolatilization stage can promote the generation of reductive CO and inhibit the generation of NOx. The NOx generation was the lowest at 2 % O2 concentration at 1.3 MPa pressure and 800 °C. In the combustion stage of the char obtained by pre-oxidation, the modified char obtained by 2 % O2 concentration has the least NOx generation. The NOx emission level in the whole combustion process can be controlled by increasing the reaction temperature in the pre-oxidation stage, extending the residence time as much as possible within the devolatilization degree of 80 %, and reasonably regulating the O2 in a low concentration range to increase the devolatilization degree in the pre-oxidation stage. This work provided evidence that targeted pre-oxidation under pressurized conditions synergistically suppresses NOx formation across both devolatilization and char combustion stages, advancing the design of low-NOx pressurized oxy-fuel systems.

Abstract Image

加压条件下O2/CO2/H2O气氛下预氧化调控对煤焦燃烧脱挥发及NOx排放影响的实验研究
加压全氧燃烧是一种很有潜力的燃煤发电碳捕集技术。预氧化是煤燃烧过程中减少NOx排放的有效手段。本研究采用加压卧式炉实验系统,研究了预氧化温度(750 ~ 1000℃)、O2浓度(0.5 ~ 10%)、气化剂和停留时间(1 ~ 7 min)对煤粉脱挥发阶段CO、CO2、CH4和NOx生成的影响,以及煤焦在1.3 MPa O2/CO2/H2O气氛下燃烧时NOx生成的影响。综合分析了煤焦燃烧阶段脱挥发对NOx生成的贡献,提出了适用于加压氧燃料燃烧的预氧化策略。结果表明,在脱挥发阶段对煤粉进行低氧预氧化可促进还原性CO的生成,抑制NOx的生成。当O2浓度为2%、压力为1.3 MPa、温度为800℃时,NOx的生成量最低。在预氧化得到的炭的燃烧阶段,O2浓度为2%得到的改性炭的NOx生成最少。通过提高预氧化阶段的反应温度,在80%脱挥发度范围内尽可能延长停留时间,合理调节低浓度范围内的O2,提高预氧化阶段的脱挥发度,可以控制整个燃烧过程中的NOx排放水平。这项工作提供了证据,证明在加压条件下有针对性的预氧化可以协同抑制脱挥发和炭燃烧阶段的氮氧化物形成,从而推进了低氮氧化物加压含氧燃料系统的设计。
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来源期刊
Fuel
Fuel 工程技术-工程:化工
CiteScore
12.80
自引率
20.30%
发文量
3506
审稿时长
64 days
期刊介绍: The exploration of energy sources remains a critical matter of study. For the past nine decades, fuel has consistently held the forefront in primary research efforts within the field of energy science. This area of investigation encompasses a wide range of subjects, with a particular emphasis on emerging concerns like environmental factors and pollution.
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