活化煤粉的氧化自燃特性及临界参数研究

During the process of coal chemical industries such as preparation of activated carbon in coal and others, it is necessary for coal to undergo an activation process, whereas, is has been revealed that a significant increase in the surface area of activated coal will inevitably lead to large amounts of intermediate metabolites and deposition in stacking, which is prone to cause spontaneous combustion, and pose a serious hazards for safety production, therefore, to reveal the oxidation and combustion mechanism of activated pulverized coal in low temperature has become an urgent focus for coal fire prevention and precaution. Activated pulverized coal produced in Xinjiang will be selected as the research object, 1) Dynamic characteristic changes for molecular structure of active functional groups on the surface of pulverized coal in chemical reaction process will be investigated experimentally, and oxidation properties of the active groups on the surface of activated pulverized coal are going to be revealed. 2) To simulate the oxidation reaction process for functional group on the surface of activated pulverized coal using quantum chemicalsimulation, as well as to determine the activity of active functional groups in activated pulverized coal. 3) To reveal the kinetic mechanism for combustion process of activated pulverized coal and investigate the abrupt characteristic temperature points and their corresponding kinetic characteristic parameters using TG/DSC-FTIR experiment system. 4) To construct an experimental platform of spontaneous combustion for studying activated coal, and to study the mathematical model of the macroscopic critical parameters of activated coal accumulation layer oxidation and spontaneous combustion, and to obtain the critical parameters of activated coal oxidation and spontaneous combustion under different conditions. The research results have scientific significance and application value for the prediction and early prevention of spontaneous combustion of pulverized coal.

在煤制活性炭等煤化工行业中，煤粉均要经过活化，活化后煤粉表面积大幅增加，生成大量中间活性产物，在堆放、沉积时极易氧化自燃，造成严重的安全隐患，活化煤粉自燃一直是煤化工安全领域亟待解决的关键科学问题。本课题以神华新疆活性炭生产过程中的活化煤粉为研究对象，1）实验研究活化煤粉表面活性官能团氧化反应过程中分子结构动态变化特征，揭示活化煤粉表面活性官能团氧化反应特征；2）采用量子化学软件，模拟活化煤粉表面官能团氧化反应过程，确定活化煤粉中活性官能团的活性大小；3）利用TG/DSC-FTIR联用实验系统，研究活化煤粉氧化过程中的突变特征温度点及其对应动力学特征参数，揭示活化煤粉氧化燃烧过程动力学机制；4）构建活化煤粉自燃模拟实验台，研究活化煤粉堆积层氧化自燃宏观临界参数确定的数学模型，得到不同条件下活化煤粉氧化自燃临界参数。研究结果可为活化煤粉自燃的早期预警奠定理论基础，具有重要的科学意义和应用价值

在煤制活性炭、煤粉制造等煤化工行业中，会将煤粉进行活化，形成活化煤粉，活化后煤粉表面积大幅增加，生成大量中间活性产物，在堆放、沉积时极易氧化自燃，造成严重的安全隐患。因此，本项目选择了三种活化煤粉为研究对象，研究得到了活化煤粉演化自热特性及自燃临界参数变化规律。采用原位红外光谱实验研究得到了活化煤粉氧化过程中活性官能团氧化变化规律，确定了影响活化煤粉氧化的主要官能团为脂肪烃及含氧官能团，采用Gaussian-16量化模拟了活化煤粉自燃活性官能团结构模型的氧化过程，并分步计算反应过程的中间体、过渡态、反应通道和生成产物，量化计算了反应过程中的活化能、焓变、吉布斯自由能等热反应动力学参数。通过活性基团氧化第一步反应的活化能对比，得出各活性官能团的反应活性次序为：-CHO-＞-HCOH-CH2-＞-CH3＞-HCOH-＞-HCOH-CH3＞-CHCH3-CH2-＞-CH2-＞-CH2O-。利用TG/DSC-FTIR联用实验系统，研究确定了活化煤粉氧化过程中的突变特征温度点，计算得到了不同氧气浓度下活化煤粉氧化热动力学参数和反应机理函数及变化特征，揭示了活化煤粉氧化燃烧过程动力学机制。采用活化煤粉自燃氧化实验测试系统，研究得到了不同氧气浓度下活化煤粉自燃过程中温度及标志性气体演化规律。活化煤粉自燃演化过程可分为被动升温、氧化升温、快速氧化和燃烧阶段。随氧气浓度降低煤粉临界自燃温度和着火延迟时间显著的增大，氧气浓度由21%降低至5%时RNM和QM煤粉在体积为21mL时临界自燃温度分别升高了25%和19%。构建了活化煤粉自燃多物理场耦合模型，采用COMSOL Multiphysics软件对活化煤粉自燃氧化反应、流场、温度场和气体浓度场进行了多场耦合求解，发现活化煤粉自燃出现明火后，堆积煤粉中心区域的氧浓度快速降低，同时CO和CO2气体表现出快速增长的趋势；建立了临界参数的lg(V/S)-1/MIT及lg(V/S)-lgti的线性拟合关系，可预测活化煤粉在不同环境条件下的自燃临界参数。项目研究成果，阐明了活化煤粉氧化自燃动力学机制，确定了活化煤粉堆积层自燃临界参数，揭示了活化煤粉自燃机理，为活化煤粉自燃火灾早期预警提供了理论依据。