Study On The Co-combustion Kinetics Of Wheat Straw And Coal Gangue And Mineral Transformation

Coal gangue is an associated mineral of coal.With the extensive use of coal,the output of coal gangue is increasing day by day.Coal gangue is a kind of low calorific value fuel,which is often used as industrial solid waste.A large number of coal gangue mines are prone to spontaneous combustion and release sulfur-containing gas,which brings great harm to the natural environment and human health.In this paper,coal gangue and wheat straw are mixed for combustion,which not only uses the solid waste coal gangue,but also effectively uses the agricultural biomass wheat straw,in order to achieve the purpose of energy saving and consumption reduction,which has important research significance.Guizhou Huopu coal gangue and Henan Gongyi wheat straw were mixed in different proportions to study the combustion characteristics and kinetics of coal gangue and wheat straw.By means of Fourier transform infrared spectroscopy(FT-IR),X-ray diffraction(XRD)and particle size analysis,the transformation law of minerals and particle size distribution of ash samples during the mixed combustion of coal gangue and wheat straw were studied.The thermogravimetric results of coal gangue and wheat straw combustion at different heating rates(10,20 and 30 K/min)show that wheat straw has two weight loss stages,corresponding to volatile combustion(215-360℃)and fixed carbon combustion(400-510℃),while coal gangue has only one weight loss peak,mainly the superposition combustion stage of volatile and fixed carbon(460-610℃),and the mixed sample has two weight loss peaks.With the increase of the mixing proportion of wheat straw,the ignition temperature,burnout temperature,activation energy and frequency factor will decrease,the maximum combustion rate and conversion rate will increase,and the comprehensive combustion characteristic index will increase,indicating that coal gangue mixed with wheat straw can improve the combustion characteristics.Coal gangue and wheat straw with different mixing ratios were burned in a tubular furnace(200-1000℃)and the ash samples were prepared.The ash samples were analyzed by FT-IR,XRD and particle size analysis.FT-IR results showed that the spectrum of pure coal gangue was almost occupied by the absorption peak of kaolinite.When the mixing proportion of wheat straw exceeded 50%,the mineral absorption peak of wheat straw appeared.XRD results showed that potassium salt,glauberite and quartz were mainly found in wheat straw,and quartz,illite,kaolinite,calcite and anatase were mainly found in coal gangue.Kaolinite is transformed into mullite after 400℃.Alkali minerals in wheat straw can inhibit the formation of mullite.When 20%wheat straw is mixed in coal gangue,mullite does not appear at the combustion temperature of 1000℃.Wheat straw can promote the formation of hematite.The results of particle size analysis show that the maximum particle size of coal gangue decreases with the increase of temperature.When wheat straw is mixed,the maximum particle size of the mixed sample at 1000℃ decreases with the increase of wheat straw mixing ratio.