惰气常压动态置换煤体吸附态氧气的阻燃机制研究

Fire prevention by inert gas injection is more widely used in coal mine, which is a promising technology from the experiences of past field trials, however, its mechanism still needs to be further understood. The previous studies were focusing on heat exchange and original environmental gas composition change during gas injection, while the dynamic displacement process and its flame retardant mechanism have been overlooked and related investigations are rare. Based on the self-designed ‘inert gas dynamic displacement and flame retardant test system’, this program will use experimental and theoretical study methods to investigate the following topics: CO2/N2 and absorbed O2 dynamic displacement process during gas injection to coal sample with pre-adsorbed O2; effect of inert gas injection to different of coal self-ignition at atmospheric pressure; quantitative analysis of the relationship between the change of the characteristic indexes of oxidation and the adsorbed oxygen replacement; flame retardant mechanism of coal absorbed oxygen replacement by dynamic inert gas at atmospheric pressure. Since the dynamic displacement process decides the change ratio and extent of oxygen in coal after inert gas injection, fundamentally reflects the flame retardant mechanism of inert gas, which will provide theoretical foundations to accurately predict the application prospect in different field conditions, and optimize the key parameters of inert gas injection design.

注惰防灭火技术在煤矿火灾防治中应用愈加广泛，是一种前景广阔、值得深入研究的科学高效防灭火技术。以往研究主要集中在惰化过程的降温和改变原有环境气体组分等问题上，而对惰化过程中注入常压气体“动态置换吸附态氧气的阻燃机制”研究很少。本项目拟利用自行设计的“惰气动态置换和阻燃效能测试装置”，通过实验研究与理论分析相结合的研究方法，考察注惰防灭火中最常用气体，即二氧化碳和氮气常压动态置换煤体吸附态氧气的作用规律，研究松散煤自热升温过程不同阶段常压动态注惰的作用特征，量化分析氧化升温特征指标的变化与惰气置换煤体吸附态氧气的相关性，并进一步探讨常压下惰气动态置换煤体吸附态氧气的阻燃机制。由于惰气置换煤体吸附态氧气决定了注惰后煤体内氧气含量的变化速率及变化程度，从更深层次体现了惰气对煤火的阻燃机理，预期研究成果可以为准确评估不同现场条件下注惰防灭火技术应用效果及工程设计中的关键参数优化等工作提供理论指导。

煤炭自燃是煤矿井下的五大自然灾害之一，严重威胁着矿井生产安全，注惰防灭火技术作为广泛被用来防治内因火灾的技术，探究其内在的阻燃机制以提高防灭火效果十分有必要。本项目首先采用惰气等温动态置换煤体中氧气的实验装置，以粒径和流量为变量，分别进行N2和CO2置换煤体中吸附态氧气的实验，得到了氧气的置换量、置换效率和平均置换速率等表征惰气常温置换能力的参数，量化了N2和CO2在常温下的防火能力；然后，采用绝热氧化装置开展了煤自热不同阶段注惰阻燃实验，改变不同气流流量，得到了氧气置换量、相对置换率和阻燃时间等煤自燃不同阶段阻燃能力的表征参数，量化了N2和CO2在高温下的灭火能力；最后，结合煤的孔隙结构测试、官能团分析以及前述实验，分析了注惰惰化涉及的气体吸附、扩散和氧化等环节在内的惰气置换煤体中吸附态氧气的过程，在此基础上，依据煤体由裂隙和基质孔隙构成的双重孔隙假设，构建了惰气动态置换煤体吸附态氧气的数学模型，进一步揭示了惰气在煤体不同自热阶段的惰化阻燃机制。研究成果补充和发展了注惰过程吸附阻氧的惰化煤体自燃的内在机理，为注惰防灭火技术现场应用过程中惰气选择和注惰关键参数优化等重要工作提供了理论指导。