Experimental And Theoretical Study Of Toxic Elements And Submicrometer Particle Formation And Capture Mechanisms During Coal Combustion

A systematic study on emissions and control of nitrogen oxide, toxic trace elements and submicrometer particles during coal combustion was conducted. The thermodynamic equilibrium distributions of trace elements during coal combustion was examined. The transformation and concentration of arsenic were conducted on an electrically heated drop tube furnace. Results show that the low of concentration and dispersion of As in different coals is very different, which is related to coal types and furnace temperature. Studies were carried out to examine the effectiveness of sorbents (TiO2, CaCO3 and Ca(OH)2) on As emission control during coal combustion. The results indicate that all three sorbents tested are capable of effectively capturing arsenic, whereas different sorbent has a different capture capacity and the capture mechanisms are different. A systematic study on submicrometer particles generation, evolution and capture in combustion processes was conducted. To better understand the capture characteristics of the submicrometer particles, experiments were carried out using TiO2 CaCO3 and Ca(OH)2 as sorbents. A circumfluent cyclone system was developed to capture submicrometer particles. The experimental study was carried out on the collection efficiency, pressure drop of the system which used air and molecule sieve as test material system. A reliable density functional theory (DFT) method at B3LYP/6-311++G** level was employed to investigate the reaction mechanism of organic nitrogen during coal pyrolysis. Experiments were carried out in a tubular quartz reactor at 400癈~1000癈. With different coal ranks, the concentrations and nitrogen types are different. The formation of HCN and NH3 during coal pyrolysis was studied to discussed in terms of some factors that affect the nitrogen distribution, including temperature, coal rank and petrographic composition of coal. It indicates that the concentrations of HCN and NH3 are increasing with increasing temperature. Coal rank and petrographic composition are important factors influencing the formation of HCN and NH3 during pyrolysis.