| From the current situation of Chinese energy development,coal will be regarded as the main raw material for primary energy consumption for a long time in the future.However,the utilization efficiency of Chinese coal is always low.Compared with developed countries,the gap is huge,which has caused a lot of waste of resources and brought adverse effects to Chinese sustainable development.Therefore,it is a great of practical significance to study how to improve the combustion efficiency of pulverized coal so as to reduce the waste of coal resources.In this paper,orthogonal experiments and thermogravimetric analysis were carried out to determine the optimal experimental conditions for alkali metal loading to improve the combustion performance of pulverized coal after microwave treatment.At the same time,the effects of alkali metal on the combustion properties and functional groups of pulverized coal after microwave modification were analyzed by thermogravimetric analysis,Fourier transforms infrared spectroscopy and Raman spectroscopy.And the kinetic analysis of the combustion process of raw coal and alkali metal loaded after microwave modified pulverized coal was carried out.The following conclusions are drawn:(1)The order of influence on activation energy under different treatment conditions is microwave power>K:Na>microwave treatment time>volatile matter,and the order of influence on the ignition temperature is K:Na>microwave treatment time>microwave power>volatile matter It can be seen that the main factors affecting the combustion performance of pulverized coal are K:Na and microwave.Comprehensive equilibrium method was selected to take both activation energy and ignition temperature into consideration to obtain the optimal conditions for the orthogonal experiment.After verification,the optimal experimental conditions were determined to be A3B3C2D2(K:Na=2:1,microwave 300W40s,and volatile matter 21%).(2)The changes of pulverized coal combustion characteristic parameters under different conditions were compared,it was found that the influence law was microwave 300W40s,K:Na=2:1>microwave 300W40s>K:Na=2:1.After 300W40s,K:Na=2:1 treatment,the pulverized coal ignition temperature dropped to 369.73?,which was 55.13? lower than the raw coal.The burnout temperature drops to 559.11 0 C,which was 50.04 0 C lower than the raw coal.The peak temperature of DTG was reduced by 50.2?,the maximum reaction rate was increased by 0.0869 mg-min"1,the final weight loss rate was increased by 8.99%,and the flammability index and comprehensive combustion characteristic index were also significantly improved.(3)The coal kinetic parameters were calculated by Coats-Redfern method.It was found that the activation energy of pulverized coal decreased to 50.370kJ·mol-1 after treatment with 300W40s and K:Na=2:1.Which was 22.596%lower than the raw coal,14.704kJ·mol-1.And found the coal sample has kinetic compensation effect.The compensation effect equation of the coal powder sample was lnA=0.12731E-0.05254,and the isokinetic temperature Tiso was 944.77?.(4)According to the most feasible mechanism function,the kinetic model of the raw coal combustion section is:d?/dT/3.65573×10/?e21889.42363/T.(2/5)(1-?)[-ln(1-?)]3/2The kinetic model of the pulverized coal combustion section after 300W40s and K:Na=2:1 treatment is:d?/dT=5.24457×109/?17415.0063.(2/5)(1-?)[-1-?)]3/2... |
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