Study on spontaneous combustion characteristics of coking coal with different pre-oxidation degrees after CO2 cooling
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摘要: 针对利用惰性气体降低煤氧化性来解决煤自燃、复燃的问题，现有研究大多是对煤低温氧化过程及煤复燃过程进行相关实验，对惰性气体降温后煤二次氧化的自燃特性涉及较少。针对上述问题，以焦煤为例，通过低温氧化实验，探究不同温度氧化的焦煤经过CO2冷却二次氧化的自燃特性。采用GC−4000A程序升温装置对焦煤进行预氧化（预氧化温度分别设为70，110，150 ℃），并对分别通入CO2气体和干空气冷却至30 ℃后焦煤二次氧化过程中的耗氧速率、CO产生率、CO2浓度和表观活化能进行分析。实验结果表明：预氧化温度相同时，与干空气冷却相比，通入CO2冷却后的焦煤相关参数的变化规律基本一致，二次氧化初期，因预氧化焦煤吸附大量CO2，阻碍了煤与O2接触，耗氧速率和CO产生率减小，表观活化能增大，焦煤的氧化性减弱；随着CO2解析，CO2冷却也影响预氧化焦煤的后期反应，使得预氧化焦煤整个反应过程自燃危险性降低。预氧化温度不同时，70 ℃和110 ℃预氧化焦煤前期CO2吸附量小，导致耗氧速率、CO产生率和表观活化能未发生变化，150 ℃预氧化焦煤冷却至30 ℃时，CO2吸附量增多，导致耗氧速率、CO产生率减小，表观活化能增大，需要的能量更多，煤氧反应更难进行，自燃危险性有所降低。因此，当煤矿井下发生煤氧化自燃危险时，需长时间通入CO2来降低矿区启封复采时发生二次氧化复燃的可能性。Abstract: In view of the problem of coal spontaneous combustion and re-ignition by reducing the oxidation of coal with inert gas, most of the existing studies are related to the coal low-temperature oxidation process and the coal re-ignition process. The spontaneous combustion characteristics of coal secondary oxidation after reducing inert gas temperature are less covered. In order to solve the above problems, taking coking coal as an example, the spontaneous combustion characteristics of coking coal oxidized at different temperatures after CO2 cooling and secondary oxidation are explored through the low-temperature oxidation experiment. The coking coal is pre-oxidized by GC-4000A temperature-programmed equipment at 70, 110, 150 ℃ respectively. The oxygen consumption rate, CO production rate, CO2 concentration and apparent activation energy of coking coal during the secondary oxidation process are analyzed after cooling to 30 ℃ with CO2 gas and dry air respectively. The experimental results show that at the same pre-oxidation temperature, compared with the dry air cooling, the change rule of related parameters of coking coal cooled by CO2 is basically the same. In the early stage of secondary oxidation, because of coking coal absorbs a lot of CO2, CO2 hinders the contact between coal and O2, the oxygen consumption rate and CO production rate decrease. The apparent activation energy increases, and the oxidation of coking coal decreases. As the CO2 resolves, CO2 cooling also affects the later reaction of pre-oxidized coking coal, which reduces the spontaneous combustion risk of pre-oxidized coking coal during the whole reaction process. When the pre-oxidation temperature is different, the pre-oxidation coking coal at 70 ℃ and 110 ℃ has a small amount of CO2 adsorption in the early stage. This leads to no change in oxygen consumption rate, CO production rate and apparent activation energy. When the pre-oxidized coking coal at 150 ℃ is cooled to 30 ℃, the coking coal has more CO2 adsorption, resulting lower the oxygen consumption rate and CO production rate. With the increase of activation energy, more energy is required. The coal oxygen reaction is more difficult. The risk of spontaneous combustion is also reduced. Therefore, when there is a danger of oxidation and spontaneous combustion of coal in the coal mine, it is necessary to inject CO2 for a long time to reduce the possibility of secondary oxidation and re-ignition when the mining area is reopened.
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图 2 耗氧速率随温度变化的规律
Figure 2. The variation law of oxygen consumption rate with temperature
图 3 CO2体积分数随温度变化的规律
Figure 3. The variation law of CO2 volume fraction with temperature
图 5
$\ln \varphi^{}_{\mathrm{CO}} $ 与1/T的关系Figure 5. The relationship between
$\ln \varphi^{} _{\mathrm{CO}} $ and 1/T表 1 焦煤工业分析
Table 1. Industrial analysis of coking coal
% 样品 水分 灰分 挥发分 固定碳含量 焦煤 0.60 7.88 21.67 69.85 
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