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Mei L.,Chongqing University | Lu X.,Chongqing University | Wang Q.,Chongqing University | Pan Z.,Chongqing University | And 5 more authors.
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2014

Because of the huge difference between original boiler operating conditions and fly ash ideal combustion state, the decarbonization effect is disappointed. Consequently, fly ash decarbonization experiments were carried out on a lab-scale CFB combustor designed base on fluidization properties of fly ash and the decarbonization characteristics were presented. Results show that fly ash requires a minimum sectional thermal load of 0.4MW/m2 for continuous and stable combustion in test combustor, the corresponding critical carbon content in the fly ash is 18%. The carbon content in the fly ash is clearly affected by the dense-bed temperature and bed pressure drop during the combustion process. In addition, the fly ash mass fraction in bottom ash does not exceed 15%. The maximum decarbonization efficiency of the test CFB combustor is approximately 75%, which is much higher than that of FARC. © 2014 Chinese Society for Electrical Engineering Source


Mei L.,Chongqing University | Wang Q.,Chongqing University | Lu X.,Chongqing University | Yang Y.,Chongqing University | And 5 more authors.
Energy and Fuels | Year: 2014

Previous studies had indicated that the thermal load of pure fly ash combustion was limited by the small superficial velocity of the furnace. Hence, the combustion characteristics of residual carbon in fly ash at high concentration of oxygen were studied on a modified CFB test rig in an attempt to increase the combustion thermal load and improve the burnout behavior of the char particles. The effect of initial O2 concentration (or excess oxygen coefficient) on thermal load, combustion performance of the test rig, and the ash behavior after burning were investigated. Results showed that the fly ash with high carbon content could be used as a low heat value fuel in high oxygen concentration combustion condition. The thermal load under pure-oxygen combustion condition was equivalent to that of the coal-fired circulating fluidized bed boilers. Furthermore, the burnout rate of char particles in fly ash and combustion efficiency of the test rig were greatly promoted as the excess oxygen coefficient increased. The quick and smooth transition behavior from air mode to oxy mode was observed, and a good fluidization condition during the transition process was achieved. In addition, fly ash mass distributions in the test rig and particle size distributions of fly ash resulting from air combustion and oxy-enriched combustion conditions were similar. © 2014 American Chemical Society. Source


Mei L.,Chongqing University | Lu X.,Chongqing University | Wang Q.,Chongqing University | Pan Z.,Chongqing University | And 5 more authors.
Applied Thermal Engineering | Year: 2014

Fly ash is a by-product of coal-fired power plants, whose production is huge. As the coal resources are in short supply in recent years, most circulating fluidized bed (CFB) boilers in China burn hard coals, thus, the carbon content in the fly ash is much higher than expected. The high carbon content in the fly ash limits the potential utilization as building materials. At present, the decarbonization method of high carbon content CFB fly ash is mainly fly ash recirculation combustion (FARC). Because of the huge difference between original boiler operating conditions and fly ash ideal combustion state, the decarbonization effect is disappointed. Therefore, a series of fly ash decarbonization experiments were carried out on a bench-scale CFB combustor designed on fluidization properties of fly ash, and the decarbonization characteristics were discussed. Results show that fly ash requires a minimum sectional thermal load of 0.42 MW/m2 for continuous and stable combustion in test combustor, corresponding to the critical carbon content in the fly ash is 18%. The maximum decarbonization efficiency of the test CFB combustor is approximately 75%, which is much higher than that of FARC. © 2013 Elsevier Ltd. All rights reserved. Source

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