煤自燃氧化过程气体温度非线性特征及预测研究

    Nonlinear characteristics and prediction of gas and temperature in coal spontaneous combustion oxidation process

    • 摘要: 为了研究煤自燃氧化过程中气体和温度的变化规律,实现煤自燃高温点的准确预测,采集大佛寺煤矿煤样开展了煤自然发火试验研究。分析了煤氧化过程中高温点迁移、气体体积分数变化、耗氧速率与气体产生率等特征指标,建立了煤温非线性预测的随机森林(RF)模型,并通过现场监测数据进行了应用验证。结果表明:煤体升温呈现阶段性变化特征和贫氧氧化特性,即使氧气体积分数在4%~5%之间依然会出现持续温升现象,在保持供风稳定的情况下,氧化反应依然能够急剧发生;耗氧速率和气体产生率整体呈指数增长趋势,临界温度之前增长缓慢,超过干裂温度后急剧增大;在煤氧化升温过程中,炉内高温点呈现出向进风口动态迁移的规律,由试验初期的45 cm位置逐渐移动到进风口处的5 cm位置;RF模型预测性能远高于同等条件下的支持向量回归(SVR)和多元线性回归(MLR)模型,预测结果的平均绝对百分误差(MAPE)小于2.39%,决定系数(R2)大于0.99;而SVR和MLR模型预测结果的MAPE则均大于5%,MLR模型预测效果最差,测试阶段预测结果的MAPE达9.53%,说明线性模型不适宜挖掘煤自燃气体产物与温度之间的非线性关系;进一步采用现场监测数据进行验证,RF模型依旧体现出优越的性能,测试阶段预测结果的MAPE仅为1.796%,而SVR和MLR模型的MAPE则分别为3.825%和5.169%。

       

      Abstract: To investigate the gas and temperature variation laws during coal spontaneous combustion oxidation and achieve accurate prediction of high-temperature points in coal spontaneous combustion, coal samples from Dafosi Coal Mine were collected for experimental research on coal spontaneous combustion. The characteristic indicators during coal oxidation were analyzed, including high-temperature point migration, gas volume fraction changes, oxygen consumption rate, and gas production rate. A random forest (RF) model for nonlinear prediction of coal temperature was established and validated using on-site monitoring data. The results showed that coal temperature rise exhibits staged variation characteristics and oxygen-deficient oxidation properties, with continuous temperature increases observed even when oxygen volume fraction remains between 4% and 5%, and rapid oxidation reactions still occurred under stable airflow conditions. Both oxygen consumption rate and gas production rates generally follow exponential growth trends, showing slow increases before reaching critical temperature and rapid acceleration after exceeding the dry cracking temperature. During coal oxidation heating, high-temperature points within the furnace demonstrate dynamic migration towards the air inlet, gradually shifting from the initial 45 cm position at the beginning of the experiment to the 5 cm position near the air inlet. The RF model demonstrated significantly superior predictive performance compared to support vector regression (SVR) and multiple linear regression (MLR) models under equivalent conditions, with prediction results showing mean absolute rercentage error (MAPE) <2.39% and coefficient of determination (R2) >0.99, while SVR and MLR models exhibited MAPE values exceeding 5%. Notably, the MLR model performed the worst, with a MAPE of 9.53% during the testing stage, highlighting the inadequacy of linear models in capturing the nonlinear relationships between gas products and temperature in coal spontaneous combustion. Further validation using on-site monitoring data confirmed the superior performance of RF model, achieving MAPE of merely 1.796% during testing stage, compared to 3.825% and 5.169% for SVR and MLR models, respectively.

       

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