Research On Microwave Induced Coke Discharge And The Enhancement Of Anthracite Ignition

Popularizing plasma ignition technology is an urgent need to reduce the construction and operation cost of thermal power units and ensure national energy security.The low volatile content and slow release rate of anthracite lead to that its plasma ignition have not been achieved.Because the existing plasma ignition technology relies on the strong thermal effect of arcing,the chemical dynamic effect of enhanced discharge is expected to realize the anthracite plasma ignition.Microwave induced coke discharge technology is able to realize field controlling,multi-point source,dispersion produce active species at low microwave power.However,the mechanism of microwave induced coke discharge,the mechanism of cracking the carbon anthracite structure by the discharge and the influence of the discharge on the anthracite ignition and combustion are still not clear.In this paper,the effects of microwave induced coke discharge cracking the structure of Jincheng anthracite and Xinhua activated coke was investigated.The differences of the influence of discharge and pyrolysis on coal structure were investigated through microwave fixed bed experiments and pyrolysis experiments.The electronic excited state nitrogen generated by discharge was detected by spectrum analysis.The effects of discharge and pyrolysis on coal and coke structures were proved to be different by gas phase product analysis,molecular weight detection and pore structure analysis.In this paper,the discharge chemical effects were decoupled by microwave induced coal and coke pyrolysis products discharge experiments.Therefore,the active species produced by the discharge have inverse graphitization effects on coal structure.The influences of microwave induced coke discharge in air conditions on the ignition of Jincheng anthracite were studied.The results showed that the proportion of carbon dioxide in the combustion products of anthracite caused by microwave induced coke discharge is higher than that of coke and anthracite caused by microwave alone.The temperature reached the ignition point of anthracite in the microwave induced coke discharge process,and increase of the temperature is rose faster than that in microwave irradiateing anthracite process,which proved that microwave induced coke discharge can strengthen anthracite ignition.Finally,the mechanism of microwave induced discharge of carbon particles is revealed by frequency domain electromagnetic field simulation and plasma fluid simulation.The results showed that during the the millimeter carbon particles scattering microwave process,the shape of particle and the gap between particles enhance the microwave electric field.Particles with refractive index n>4 or k>2 is able to strengthen the microwave electric field more than 10 times by the small gap between them,while particles with refractive index n<4 and k<2 are more likely to enhance the microwave electric field by their shape.In addition,if the gap is too small,electrons will be attached to the wall and discharge will be hindered.In addition,Townsend ionization coefficient will be increased if the gas contains low ionization energy component.