Study On Alkali Metal Migration And Reaction Kinetics In Mixed Coal Combustion Of Corn Straw

The TG-DTG thermal analysis technology is applied to simulate the combustion characteristics of corn stover and pulverized coal in boiler atmosphere at different heating rates.The Flynn-Wall-Ozawa method used to establish a dynamic model,researched the combustion characteristics and kinetics of corn stover and its blended coal combustion under the mixed atmosphere.The combustion conditions under the same experimental conditions were compared with the air condition.The results show that the comprehensive combustion characteristic index S_N doubles with the heating rate,and is halved as the proportion of pulverized coal is doubled.As the proportion of blended coal increases,the fixed carbon combustion stage on the DTG curve gradually splts into two weight loss peaks,and the degree of division in the mixed atmosphere is more obvious.The incorporation of pulverized coal will increase the apparent activation energy fluctuation required in the combustion process.The alkali metal migration of corn straw and its mixed coal under different conditions was analyzed by FactSage.The results showed that the melting products of pure corn straw in the simulated combustion process contained more K2O,Na2O and other low melting point crystals,about 36%of the mole fraction containing K residue was K2O,and more than 99%of the mole fraction containing Na residue was Na2O.After mixing with coal,a large number of silica-alumina salt and other high melting point crystals are generated in the solid products,leaving the alkali metals in the residues,which greatly reduces the alkali metals precipitated into the gas phase.The alkali metal precipitation rate in the mixd atmosphere is slightly higher than that in the air atmosphere,indicating that oxygen-rich combustion can reduce the alkali metal precipitation.The morphology of ash and the content of alkali metal were observed and measured by burning corn straw and its mixed coal in horizontal tubular furnace system under different conditions.The results showed that the coking property of ash slag was improved,the density was higher and the mineral content in the product was greatly increased.The K element exhalation rate of corn straw in the medium temperature range was about 40%~45%,and the Na element exhalation rate was about 70%.The exhalation rate of mixed atmosphere is slightly higher than that of air atmosphere.Thermodynamic simulation results show that the precipitation rate is smaller than the experimental results.