{"title":"Statistical Modeling of Constituents in Ash Evolved From Pulverized Coal Combustion","authors":"Esam Jassim ","volume":86,"journal":"International Journal of Mechanical and Mechatronics Engineering","pagesStart":348,"pagesEnd":353,"ISSN":"1307-6892","URL":"https:\/\/publications.waset.org\/pdf\/9997509","abstract":"
Industries using conventional fossil fuels have an
\r\ninterest in better understanding the mechanism of particulate
\r\nformation during combustion since such is responsible for emission
\r\nof undesired inorganic elements that directly impact the atmospheric
\r\npollution level. Fine and ultrafine particulates have tendency to
\r\nescape the flue gas cleaning devices to the atmosphere. They also
\r\npreferentially collect on surfaces in power systems resulting in
\r\nascending in corrosion inclination, descending in the heat transfer
\r\nthermal unit, and severe impact on human health. This adverseness
\r\nmanifests particularly in the regions of world where coal is the
\r\ndominated source of energy for consumption.
\r\nThis study highlights the behavior of calcium transformation as
\r\nmineral grains verses organically associated inorganic components
\r\nduring pulverized coal combustion. The influence of existing type of
\r\ncalcium on the coarse, fine and ultrafine mode formation mechanisms
\r\nis also presented. The impact of two sub-bituminous coals on particle
\r\nsize and calcium composition evolution during combustion is to be
\r\nassessed. Three mixed blends named Blends 1, 2, and 3 are selected
\r\naccording to the ration of coal A to coal B by weight. Calcium
\r\npercentage in original coal increases as going from Blend 1 to 3.
\r\nA mathematical model and a new approach of describing
\r\nconstituent distribution are proposed. Analysis of experiments of
\r\ncalcium distribution in ash is also modeled using Poisson distribution.
\r\nA novel parameter, called elemental index λ, is introduced as a
\r\nmeasuring factor of element distribution.
\r\nResults show that calcium in ash that originally in coal as mineral
\r\ngrains has index of 17, whereas organically associated calcium
\r\ntransformed to fly ash shown to be best described when elemental
\r\nindex λ is 7.
\r\nAs an alkaline-earth element, calcium is considered the
\r\nfundamental element responsible for boiler deficiency since it is the
\r\nmajor player in the mechanism of ash slagging process. The
\r\nmechanism of particle size distribution and mineral species of ash
\r\nparticles are presented using CCSEM and size-segregated ash
\r\ncharacteristics. Conclusions are drawn from the analysis of
\r\npulverized coal ash generated from a utility-scale boiler.<\/p>\r\n\r\n
<\/p>\r\n","references":"[1]\tQiu, F. Li, C.G. Zheng, \"Mineral Transformation during Combustion of Coal Blends,\u201d Int. J. Energy Res., vol.23, 1999, pp. 453-463.\r\n[2]\tL.L Baxter, \"The evolution of mineral particles size distributions during early stages of coal combustion,\u201d Prog. Energy Combust Sci., vol. 16, 1990, pp. 261\u2013266.\r\n[3]\tWP Linak, CA Miller, WS Seames et al. Proc. Combust. Inst., 29 (2002), pp. 441\u2013447.\r\n[4]\tW. Seames, \"An initial study of the fine fragmentation fly ash particle mode generated during pulverized coal combustion,\u201d Fuel process Technology, vol. 81, pp.109-125, 2003.\r\n[5]\tR.P. Gupta, L. Yan, S.K. Gupta, T.F. Wall, T. Kiga, and S. Watanabe, \"CCSEM analysis of minerals in coal and thermal performance of PC-Fired boilers,\u201d Clean Air, vol. 6, 2005, pp. 157-170.\r\n[6]\tZ. Ma, F. Iman, P. Lu, R. Sears, L. Kong, A.S. Rokanuzzaman, D.P. McCollor, and S.A. Benson, \"A comprehensive slagging and fouling prediction tool for coal-fired boilers and its validation\/application,\u201d Fuel Processing Technology, vol. 88, pp.1035\u20131043, 2007.\r\n[7]\tE. Raask, \"Mineral impurities in coal combustion\u201d. Hemisphere Publishing, Washington, 1985, pp 484.\r\n[8]\tC. Sheng, and Y. Li, \"Experimental study of ash formation during pulverized coal combustion in O2\/CO2 mixtures,\u201d Fuel 87, 2008, pp.1297\u20131305.\r\n[9]\tL. Yan, \"CCSEM analysis of minerals in pulverized coal and ash formation modelling,\u201d PhD thesis, The University of Newcastle, Australia, 2000.\r\n[10]\tT. Zeng, A.F. Sarofim, and C.L. Senior, \"Vaporization of Arsenic, Selenium and Antimony during Coal Combustion,\u201d Combustion and Flame, vol. 126, 2001, pp.1714-1724.","publisher":"World Academy of Science, Engineering and Technology","index":"Open Science Index 86, 2014"}