烟煤升温氧化的影响因素及其低温热解动力学
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摘要
为探讨烟煤升温氧化反应特性及其影响因素,利用热重法研究了不同含水率及不同粒度烟煤在10℃/min加热速率下的热失重过程,并应用Coats-Redfern积分法进行低温热解动力学分析。结果表明,水分蒸发和气体解吸附、增重与结构氧化分别主导其2步氧化机制。第1阶段温度阈值随含水率的增加先减少后增加,且含水率为9.16%的煤样S3温度阈值最小,含水率在第1阶段反应过程中影响显著;第1阶段温度阈值及自燃阈值随粒度增大而升高。选用一级反应模型和二级反应模型分别用于计算2个反应段的表观活化能,所得相关系数R2>0.98,活化能与频率因子之间存在动力学补偿效应,且发现煤样S3及粒度最小的煤样L5(19.21μm)较同组其它煤样相比,需要较少的活化能以克服反应壁垒,表明其具有较高的自燃危险性。
In order to research the characteristics of the thermal oxidation reaction of coal by using thermogravimetric technique,the thermal mass loss and oxidation of bituminous coal with different moisture and different particle size were investigated under a heating rate of 10 ℃/min. Low-temperature pyrolysis kinetics model is developed by using Coats-Redfern integral method. Results show that the two-step oxidation process of bituminous coal was mainly affected by water evaporation and gas desorption, mass-gaining and structural oxidation. With the increase of moisture, the temperature thresholds lying in the first step fist decrease and then increase, and the temperature thresholds of sample S3 with moisture of 9.16 % are minimum, therefore, moisture has a significant effect on the first stage reaction process; however, the temperature thresholds lying in the first step and the spontaneous combustion threshold increase with the increasing particle size. A first-order and second-order reaction models are proposed respectively for describing the two-step reaction process with the correlation coefficient R2 greater than 0.98, thus, kinetic compensation relationship exists between oxidation activation energy and frequency factor. Compared with the other coal samples in the same group, lower apparent activation energy was required by the sample S3 with 9.16 % moisture content and the sample L5 with the smallest particle size(19.21 μm) to overcome the reaction barrier, which indicated that it has a high risk of spontaneous combustion.
In order to research the characteristics of the thermal oxidation reaction of coal by using thermogravimetric technique,the thermal mass loss and oxidation of bituminous coal with different moisture and different particle size were investigated under a heating rate of 10 ℃/min. Low-temperature pyrolysis kinetics model is developed by using Coats-Redfern integral method. Results show that the two-step oxidation process of bituminous coal was mainly affected by water evaporation and gas desorption, mass-gaining and structural oxidation. With the increase of moisture, the temperature thresholds lying in the first step fist decrease and then increase, and the temperature thresholds of sample S3 with moisture of 9.16 % are minimum, therefore, moisture has a significant effect on the first stage reaction process; however, the temperature thresholds lying in the first step and the spontaneous combustion threshold increase with the increasing particle size. A first-order and second-order reaction models are proposed respectively for describing the two-step reaction process with the correlation coefficient R2 greater than 0.98, thus, kinetic compensation relationship exists between oxidation activation energy and frequency factor. Compared with the other coal samples in the same group, lower apparent activation energy was required by the sample S3 with 9.16 % moisture content and the sample L5 with the smallest particle size(19.21 μm) to overcome the reaction barrier, which indicated that it has a high risk of spontaneous combustion.
引文
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[15] Arenillas A, Rubiera F, Pis J J. Simultaneous thermogravimetric-mass spectrometric study on the pyrolysis behavior of different rank coals[J]. Journal of Analytical and Applied Pyrolysis, 1999, 50(1):31.
[16]胡源,宋磊,尤飞,等.火灾化学导论[M].北京:化学工业出版社,2007.
[2]金永飞,闫旭斌,岳宁芳,等.恒温解吸附煤样低温氧化特性试验研究[J].煤矿安全,2017,48(5):41-45.
[3]陈鹏,张弛,张浪,等.煤自燃倾向性测试方法研究进展与展望[J].煤矿安全,2016,47(3):164-168.
[4] Slyusarskiy K V, Larionov K B, Osipov V I, et al. Nonisothermal kinetic study of bituminous coal and lignite conversion in air and in argon/air mixtures[J]. Fuel,2017, 191:383-392.
[5]朱红青,郭艾东,屈丽娜.煤热动力学参数、特征温度与挥发分关系的试验研究[J].中国安全科学学报,2012,22(3):55-60.
[6]邵玥,尤飞,尤明伟,等.升温速率及氧浓度对长焰煤煤氧复合过程特性的影响[J].安全与环境学报,2016,16(5):176-181.
[7] Avila C, Wu T, Lester E. Estimating the spontaneous combustion potential of coals using thermogravimetric analysis[J]. Energy&Fuels, 2014, 28(3):1765-1773.
[8]张辛亥,白亚娥,李青蔚,等.基于活化能指标研究不同变质程度烟煤的自燃倾向性[J].矿业安全与环保,2016,43(1):5-7.
[9]唐一博,李云飞,薛生,等.长期水浸对不同烟煤自燃参数与微观特性影响的实验研究[J].煤炭学报,2017,42(10):2642-2648.
[10]王文达.特征因素对煤热解及自燃特性影响分析[D].南京:南京工业大学,2017.
[11] Wang H H, Dlugogorski B Z, Kennedy E M. Coal oxidation at low temperatures:oxygen consumption, oxidation products, reaction mechanism and kinetic modelling[J]. Cheminform, 2004, 29(6):487-513.
[12]郝朝瑜,王继仁,马念杰,等.水分润湿煤体对煤自燃影响的热平衡研究[J].中国安全科学学报,2014,24(10):54-59.
[13] Saurabh B, Pradeep K. The effect of moisture condensation on the spontaneous combustibility of coal[J].Fuel, 1996, 75(13):1523-1532.
[14] Huangfu Wen-hao, You Fei, Shao Yue, et al. Effects of oxygen concentrations and heating rates on nonisothermal combustion properties of jet coal in East China[J]. Procedia Engineering, 2018, 211:262-270.
[15] Arenillas A, Rubiera F, Pis J J. Simultaneous thermogravimetric-mass spectrometric study on the pyrolysis behavior of different rank coals[J]. Journal of Analytical and Applied Pyrolysis, 1999, 50(1):31.
[16]胡源,宋磊,尤飞,等.火灾化学导论[M].北京:化学工业出版社,2007.