Research On The Oxidized Spontaneous Combustion Characteristics Of Oxidation And Carbonization Powders

In the production process of coal-based activated carbon,the raw coal is processed by oxidation and carbonization process after being broken.A large number of by-products are produced in this process:oxidation powder,carbonization powder.Oxidation powder and carbonization powder are prone to spontaneous combustion of heat storage,and more dangerous.In order to study the oxidized spontaneous combustion of oxidation powder and carbonization powder,the raw coal used in coal activated carbon production and the oxidation powder and carbonization powder produced in the preparation process were selected.The physical and chemical characteristics,thermal effect,thermal kinetics and gas release rule in oxidation process of selected samples were studied by experiments,which provided a basis for the prevention and comprehensive utilization and spontaneous combustion of oxidation powder and carbonization powder.(1)Nitrogen adsorption experiment,scanning electron microscope experiment and fourier infrared change experiment were used to test the microstructure parameters,pore size structure and active functional group of the samples.The results domonstrated that the pore structure parameters of oxidation powder and carbonization powder increased compared with raw coal.The mesoporous proportion of raw coal and oxidation powder was the largest,and the macropore proportion of carbonization powder was the largest.The surface of raw coal is smooth,whereas,the oxidation powder and carbonization powder have rough surface,loose texture and developed pore structure.The relative content of aromatic hydrocarbon structure,oxygen-containing functional group and aliphatic hydrocarbon structure in oxidization powder and carbonization powder is higher than raw coal.(2)C80 microcalorimeter and differential calorimeter were used to measure the exothermic characteristics of low temperature oxidation and high temperature oxidation respectively,and the change of the characteristic temperature of heat release and heat flow were obtained.The results domonstrated that the heat absorption of oxidation powder and carbonization powder is weakened compared with raw coal in the process of oxidation,the heat release accounted for more than 50%of the heat release in the stage of oxidation growth,and the ratio of the heat release in the stage of thermal decomposition of high temperature oxidation.Compared with raw coal,the ratio of the heat release of oxidation powder and carbonization powder in the stage of high temperature oxidation combustion increased,and the degree of oxidation reaction was more violent.(3)The thermogrgravity analyzer was used to measure and analyze the thermal weight rule and characteristic temperature of the sample during the oxidation process,and the oxidation stage was divided.Combined with the thermal kinetics study of oxidation,the apparent activation energy and thermal kinetic parameters of the sample were calculated in quantitative terms.The results showed that the characteristic temperature points of the oxidation powder and carbonization powder,ignition temperature(T5),maximum point temperature for combustion rate(T6)and burnout temperature(T7),all appeared earlier than raw coal,while the temperature points of critical temperature(T1),dryness temperature(T2),reactive temperature(T3)and growth temperature(T4)appeared different degrees of lag.The maximum and minimum apparent activation energies of oxidation powder and carbonization powder are smaller than raw coal.Sample refers to the pre-exponential factor between 1012?1021,the pre-exponential factor value interval of oxidation powder and carbonized powder were wider than raw coal,and reach maximum heat enthalpy value point and the value of the corresponding conversion are also smaller than raw coal.(4)Using high temperature process heating system for the selected samples in 30?500? temperature range oxidation gases and gas ratio to measure and analyzed,the optimum selection of index gases during combustion.The results showed that the oxidation powder and carbonization powder gas emission and gas production rate were greater than raw coal.In addition,the heat release strength of the oxidized powder and the carbonized powder is greater than raw coal,and heat release amount of oxidation is significantly greater than raw coal,the tendency of spontaneous combustion of oxidized powder and carbonized powder were increased.