Study On The Combustion And Pollutant Emission Characteristics Of Coal Blent With Biomass In O₂/CO₂Atmosphere

As the increasing seriousness of environmental pollution and energey crisis, the O2/CO2combustion technology and the co-combustion of biomass and coal technology have been highly respected. O2/CO2combustion technology enriches CO2concentration up to95%for easily CO2capture, it can also reduce the emission of NOx and SO2, so it is a promising advanced combustion technology and friendly to environment. The co-combustion of biomass and coal technology can reduce the emission of SO2、NOx and CO2, which is very useful to ease environmental pollution and energy crisis. In this work, O2/CO2combustion technology and co-combustion of biomass and coal technology are combined, which is meaningful to energy conservation and environmental protection.Based on these background, with bituminous coal, three kinds of biomass (including rice straw, wheat straw, corn stalk) and their blending as the research object, the combustion and pollutant emission characteristics of coal blent with biomass in O2/CO2atmosphere were studied using thermogravimetric analysis techniques, tube heating furnace test and theoretical calculation.TGA/SDTA851e comprehensive thermal analyzer was utilized to study the combustion characteristics of bituminous coal, biomass and their blending, the impacts of oxygen concentration, biomass types, blending ratio and heating rate were researched. The results show that the ignition temperature and burnout temperature of biomass were lower compared with coal, the burning rate was faster and the combustion characteristic was better in O2/CO2atmosphere. With the increase of the blending ratio of biomass, the ignition temperature and burnout temperature both lowered, the burnout time was shortened, the comprehensive combustion characteristic index increased. With the increase of the heating rate, the combustion rate increased, the burnout time was significantly shortened, the burnout temperature rised, the index S increased. In O2/CO2and O2/N2atmosphere, with the increase of the oxygen concentration, the burnout temperature was lowered, the index S increased. Compared with O2/N2atmosphere, the TG, DTG curves of each sample in O2/CO2atmosphere changed slightly, and without a certain rule.The Coats-Redfern integral method was used to study the influence of mechanism function selection on solving dynamic parameters. The results show that the three-dimensional diffusion (ball symmetric) function is the optimum reaction mechanism of coal blent with biomass. In O2/CO2and O2/N2atmosphere, the co-combustion of coal and biomass was transition combustion, the oxygen partial pressure indexes of high temperature period was greater than low temperature period. The activation energy E and the frequency factor A did not change when oxygen concentration changed. Compared with O2/N2atmosphere, the activation energy E and frequency factor A of each sample in O2/CO2atmosphere changed silightly.The tube heating furnace was utilized to reserch the sulfur and nitrogen emission characteristics of biomass, coal and their blending, and influence laws of factors such as oxygen concentration, biomass type, blending ratio and furnace tem-perature were investigated. The results show that the SO2yields and conversion rate of biomass were much lower than coal in O2/CO2atmosphere. With the increase of the blending ratio of biomass, the SO2yields and conversion rate both reduced. With the rise of furnace temperature or oxygen concentration, the SO2yields and conversion rate both increased. When the oxygen concentration was equal, the SO2yields in O2/CO2atmosphere were always lower about5%than that in O2/N2atmosphere. The NO yields and conversion rate of biomass were lower than coal in O2/CO2atmosphere. With the increase of the blending ratio of biomass, the NO yields and conversion rate both reduced. With the rise of furnace temperature or oxygen concentration, the NO yields and conversion rate both increased. When the oxygen concentration was equal, the NO yields of each sample in O2/CO2atmosphere were always lower about10%-20%than that in O2/N2atmosphere.