Experimental Study On Spontaneous Combustion Of Coal-based Activated Carbon Based On Thermal Analysis

Coal-based activated carbon is an excellent adsorbent and is widely used in the pharmaceutical factory,chemical industry,food,environmental protection,and defense industries.However,activated carbon accumulates heat.When accumulated heat exceeds the amount of lost heat,coal-based activated carbon will spontaneously ignite.Therefore,the thermodynamic properties and the law of the exothermic process were studied to reveal the oxidation characteristics of coal-based activated carbon and provide support for the spontaneous combustion of coal-based activated carbon.This paper selected four coal-based activated carbon in different stages of production and determined their compositional elements,pore structure characteristics,and changes in major functional groups.Thermogravimetric TG-DSC experiment was used to test the characteristic temperature and thermal effects of the oxidation process,and the activated carbon is combined with a theoretical and experimental approach.The oxidation kinetics were studied.(1)Through tested elemental analysis and industrial analysis,it was found that the carbon content of coal-based activated carbon in different stages of production gradually increased,the contents of hydrogen,oxygen,and nitrogen gradually decreased,the volatile matter decreased,and the moisture and ash first decreased and then increased.The specific surface area,average pore diameter and total pore volume of coal-based activated carbon were obtained by low-temperature nitrogen adsorption.The results showed that the specific surface area and total pore volume of the activated material were the largest and the average pore size was the smallest.The Fourier transform infrared spectrometer was used to obtain the infrared spectrum of the coal-based activated carbon,and it was found that both the carbonization and activation processes reduced the number of oxygen-containing functional groups.Scanning electron microscopy experiments revealed that the surface of the activated material particles were uneven and there were a lot of pores.(2)Synchronous thermal analysis experiment was used to test the thermal analysis curves of coal-based activated carbon at different heating rates of 5?/min,10?/min,and 20?/min.The characteristic temperature was analyzed and calculated and the change was analyzed.According to the law,the six characteristic temperature divisions were analyzed separately.It was found that the characteristic temperature increased from the briquette to the carbonized material.The characteristic temperatures of the carbonized material and the carbonized powder were similar except that the critical temperature and the cracking temperature decreased.Because the activated material has no stage of oxygen absorption and weight gain,it does not divide the active temperature and the accelerating temperature,and the critical temperature of the activated material is the smallest and the temperature of the ignition point is the maximum.The characteristic temperature changing rule indicates that the carbonization and activation processes have a greater impact on the coal-based activated carbon.(3)The KAS non-isothermal kinetics analysis method was used to analyze and compare the kinetic parameters of its oxidation reaction,summarize the changes,and discuss the spontaneous oxidation of coal-based activated carbon in different production stages.Finally,based on the basic physicochemical structural characteristics of coal-based activated carbon,combined with the oxidation kinetic parameters,the correlations between moisture and pore structure characteristics and the absorption heat,volatile matter and heat release of coal-based activated carbon were analyzed.