Experimental Investigation On Combustion Characteristics Of Coal Gangue And Coal Gangue Blended With Sawdust

Coal gangue is one of the largest solid wastes in China,as the low comprehensive utilization,coal gangue which has already been mined out takes over much land resources directly and gradually accumulates to form coal gangue mountains,these coal gangue mountains could cause great harm to soil,groundwater and surface water after leaching by rain,what’s more,the spontaneous of coal gangue endangers the environment by producing too much toxic gas pollutions.The way to achieve huge consumption of coal gangue is combustion for power generation and heating supply,and it will improve the comprehensive utilization efficiency of coal gangue.This article aims to investigate the combustion characteristics of coal gangue and sawdust,pulverized coal gangue and coal gangue blended with 10%and 20%sawdust were shaped to large cylindrical pellets,respectively,by a metal shaping model.The ignition characteristics(ignition mode,ignition delay,and internal ignition temperature)and volatile combustion behaviors(burnout time and combustion process)of coal gangue pellet were studied in an electric heating vertical tube furnace,the background gas atmosphere was set to be CO2/O2 and the flow temperature,flow rate and oxygen concentration were the main control parameters.When the background gas atmosphere was changed to be air condition,coal gangue and coal gangue blended with 10%and 20%sawdust biomass pellet combustion experiment were also carried out with the same gas flow temperature and flow rate.Besides,thermalgravimetrics analysis of such three samples were also added with three different heating rates,the characteristics temperature,mass loss rate and activation energy were also discussed.The research results showed that there were three different ignition modes(homogeneous ignition of volatile,and heterogeneous ignition of char or coal,and hetero-homogeneous ignition of volatile and coal)of coal gangue pellet under CO2/O2 atmosphere.Once the gas temperature,oxygen concentration or the gas flow rate increased,the ignition delay decreased,and the change of internal ignition temperature was similar to that of ignition delay.When sawdust was added in coal gangue,the ignition temperature and burnout temperature during thermalgravimetric combustion decreased greatly,with the increase of sawdust content,the comprehensive combustion characteristics index increased exponentially,but the average activation energy decreased,which meant that the promoting effect of the addition of sawdust on the combustion of coal gangue.The ignition delay and internal ignition temperature of the blended pellet were also decreased obviously with the increased of sawdust content.Compared with pure coal gangue pellet,the volatile combustion flame was full around the pellet,and when the flow temperature and rate were high enough,there could be flame injection phenomena,while the volatile existed only above the pellet for coal gangue pellet.