煤自然降温过程氧化特性及“滞后”效应实验研究

发布时间：2018-03-09 01:17

  本文选题：煤　切入点：降温过程　出处：《西安科技大学》2017年硕士论文　论文类型：学位论文

【摘要】：煤自燃的发展是一个复杂的物理和化学的动态过程。当煤发生自燃后,应及时采取适当的防灭火措施,抑制煤自燃的发展。在降温过程中需实时监测火区的温度以及气体浓度等参数,因此,对煤自然降温过程的研究显得尤为重要。为了研究煤自然降温过程的自燃特性,本文通过程序实验研究不同煤种在不同粒径以及不同降温方式下的自燃特性,分析粒径和降温方式对降温过程气体产物浓度的影响,根据CO浓度将降温过程划分为不同的阶段,并进行动力学的分析,同时将升温过程和不同降温过程进行对比和分析。结果表明:煤自然降温过程属于一个非线性的动态过程。降温过程中,实验载气中氧气浓度越大,煤样粒径越小,煤样生成的气体产物浓度越大,生成C2H4气体的最低温度越低;通过CO浓度将不同降温过程分成不同温度阶段,并计算出其活化能,表现为实验煤样变质程度越高,活化能值越大;在相同实验载气的情况下,升温过程相比于降温过程中生成相同的气体浓度(CO、C2H4和1/3焦煤CO2)时的温度发生了一定的“滞后”;实验煤样为褐煤和无烟煤时,升温过程相比于降温过程中生成相同的CO2浓度时的温度发生了一定的“提前”;褐煤和1/3焦煤的空气降温过程的耗氧速率大于空气升温过程的耗氧速率,无烟煤空气升温过程与空气降温过程的耗氧速率存在两个交点。同时,通过自然发火实验研究煤样升温过程和绝氧降温过程中高温点移动规律、气体产物浓度以及自燃特性参数和极限参数,并进行对比分析。结果表明:升温过程和降温过程高温点的位置变化不完全重合;为消除降温过程中漏风量无法测量的因素,得到了单位流量耗氧速率、单位流量CO、CO2产生率以及单位流量最大、最小放热强度的计算方法,其结果与程序升温结果相同,证明了方法的可行性以及增加了升温过程与降温过程的可比性;自然发火升温过程中,煤温在50℃时,下限氧浓度、最小浮煤厚度和上限漏风强度均达到最值,当浮煤厚度小于0.648m时,浮煤不会发生自燃现象;自然发火降温过程中,煤温在80℃时,下限氧浓度、最小浮煤厚度和上限漏风强度均达到最值,当浮煤厚度小于0.384m时,浮煤不会发生复燃现象。因此,研究煤自然降温过程特性在煤矿采空区煤自燃、封闭火区等实施灭火后,对指导煤降温过程中煤温以及气体浓度的变化具有非常重要的意义。
[Abstract]:The development of coal spontaneous combustion is a complex physical and chemical dynamic process. In order to study the spontaneous combustion characteristics of coal, it is necessary to monitor the parameters of temperature and gas concentration in real time during the cooling process, so it is very important to study the natural cooling process of coal. In this paper, the spontaneous combustion characteristics of different coal types under different particle sizes and different cooling modes are studied by program experiments. The effects of particle size and cooling mode on the concentration of gas products in the process of cooling are analyzed. According to the concentration of CO, the cooling process is divided into different stages. The results show that the natural cooling process of coal is a nonlinear dynamic process. The higher the oxygen concentration in the experimental gas is, the higher the oxygen concentration is during the cooling process. The smaller the particle size of coal sample is, the greater the concentration of gas product is, and the lower the minimum temperature of C _ 2H _ 4 gas is, and the activation energy is calculated by dividing the different cooling process into different temperature stages by CO concentration. The higher the metamorphic degree of experimental coal is, the greater the activation energy is. The temperature of the heating process is lagged when the same gas concentration is produced during the cooling process, and the experimental coal samples are lignite and anthracite, while the temperature of the coking coal is lower than that of the coking coal with the same concentration of CO _ (2) H _ (4) and 1/3 coking coal (CO _ (2)). The oxygen consumption rate of the air cooling process of lignite and 1/3 coking coal is higher than that of the air temperature rising process, and the oxygen consumption rate of the air cooling process of lignite and 1/3 coking coal is higher than that of the air heating process. There are two intersections between the oxygen consumption rate of anthracite air heating process and the air cooling process. At the same time, the moving law of high temperature points in the process of coal sample heating and adiabatic cooling is studied by natural combustion experiment. The gas product concentration, spontaneous combustion characteristic parameters and limit parameters are compared and analyzed. The results show that the change of the position of the high temperature points in the heating process and the cooling process is not completely coincident, and in order to eliminate the factors that the air leakage can not be measured during the cooling process, The calculation methods of oxygen consumption rate per unit flow rate, CO _ 2 production rate per unit flow rate and maximum and minimum exothermic intensity per unit flow rate are obtained. The results are the same as those of programmed heating. It is proved that the method is feasible and the comparability between the heating process and the cooling process is increased, the lower oxygen concentration, the minimum floating coal thickness and the upper wind leakage intensity can reach the maximum value when the coal temperature is 50 鈩，

本文编号：1586372