Simulation and Analysis of Pulverized Coal and Straw Oxy-Co-Firing

• Main Authors: Po-ShenLin, 林柏伸
• Other Authors: Ming-Hsun Wu
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/51692874840862656225

碩士 === 國立成功大學 === 機械工程學系碩博士班 === 100 === The characteristics of oxy-coal combustion and oxy-co-firing of pulverized coal and straw are studied using chemical equilibrium calculation and three-dimensional computational fluid dynamic simulations. The chemical equilibrium analysis shows that the temperature of oxy-firing is comparable to air-firing by enhancing O2 concentration to 30 %. Over 65% of flue gas has to be recirculated under this operating condition. With the higher O2 concentration in the oxidizer, the overall flow rate is reduced. The concentration of CO2 is increased from 15.7 % for air-firing to 94.4 % for oxy-firing, and the flue gas contains much lower NOx concentration due to the reduction of thermal NOx. Furthermore, oxy-co-firing of pulverized coal can result in higher NOx and lower SOx emission due to the variation of the composition of fuel blends. Three-dimensional reacting flow simulations have been further carried out in this study. The results shows that the coal burnout out and vorticity in the vicinity of burner is lower for oxy-firing than that for air-firing. Lower excess oxygen and swirl ratio will result in worse coal burnout and higher CO concentration. For pulverized coal/straw oxy-co-firing, larger mean particle size leads to the devolatilization of straw dust in much slower rate. Increasing straw content in the fuel blends would result in higher NO and lower SO2 concentrations in the flue gas.