An Experimental Study of Temperature of Burning Coal Particle in Fluidized Bed Mirko Komatina, † Vasilije Manovic,* ,†,‡ and Dragoljub Dakic § Faculty of Mechanical Engineering, UniVersity of Belgrade, 27 marta 80, 11000 Belgrade, Serbia and Montenegro, UniVersity of Belgrade, Djusina 7, 11000 Belgrade, Serbia and Montenegro, and Institute for Nuclear Sciences, Vinca, P.O. Box 522, 11001 Belgrade, Serbia and Montenegro ReceiVed July 20, 2005. ReVised Manuscript ReceiVed September 28, 2005 The purpose of this study was to investigate the temperature of coal particle during combustion in fluidized bed (FB). It is necessary to know the coal particle temperature in order to predict kinetics of chemical reactions within and at the surface of coal particle, accurate NO x and SO 2 emission, fragmentation, attrition, the possibility of ash melting, etc. The experimental investigations were conducted in order to obtain the reliable data on the temperature of particle burning in the FB. A method using thermocouple was developed and applied for measurements. Thermocouple was inserted in the center of the particle shaped into spherical form with various diameters: 5, 7, 8, and 10 mm. Two characteristic types of low-rank Serbian coals were investigated. Experiments were done at the FB temperature in the range of 590-710 °C. Two types of experiments were performed: (i) combustion using air as fluidization gas and (ii) devolatilization with N 2 followed by combustion of obtained char in air. The temperature histories of particles during all stages after introducing in the FB were analyzed. Temperature difference between the burning particle and the FB was defined as a criterion, for comparison. It was shown that the temperature profile depends on the type of the coal and the particle size. The higher temperature difference between the burning particle and the FB was obtained for smaller particles and for lignite (130-180 °C) in comparison to the brown coal (70-130 °C). The obtained results indicated that a primary role in the temperature history of coal particle have the mass and heat transfer through combusting particle. Introduction Fluidized bed (FB) combustion is one of the advanced technologies for coal combustion. It has been developed as a promising technology, which can ensure in situ emission control of gaseous pollutants (NO x and SO 2 ) and fuel flexibility. FB has an inert fluidizing medium, which contains only a few percent by weight of coal enabling each coal particle to burn surrounded by the moving inert particles. Understanding the behavior of the coal particle in the hot FB is the basis for investigation of the processes occurring in the FB combustor. 1,2 Temperature history of single coal particle in the hot FB determines the processes and phenomena like devolatilization and char combustion, fragmentation and attrition, sulfur self- retention by coal ash, and ash agglomeration. Combustion of coal particle in the FB is a complex process, which, from the aspect of coal particle temperature, may be studied in three main stages: drying, devolatilization, and char combustion. After entering the coal particle into the combustion device, the rapid release of moisture (drying) and volatile substances (devolatilization) into the surroundings occurs as a result of high temperature of the surrounding medium. Tem- perature of the coal particle as well as heat and mass transfer during these processes are different from those during combus- tion of the char particle. Heat transferred from the FB media to a coal particle is consumed by heating and drying of the particle and endothermic reactions of forming volatiles. Exothermic reaction of char combustion causes increase of the particle temperature and heat transfer from particle to surrounding medium. 3,4 Measurement of coal particle temperature in the hot FB can be conducted by different methods: photographic method, 5 fusible wire ring, 6 thermocouple technique, 3,7-10 and optical probe. 11,12 The experimental investigations were performed with coal or char particles. It was noticed that photographic and * To whom correspodence should be addressed. Fax: +381-11-3235 539. E-mail: vmanovic@rgf.bg.ac.yu. † Faculty of Mechanical Engineering, University of Belgrade. ‡ University of Belgrade. § Institute for Nuclear Sciences. (1) Grubor, B.; Manovic, V.; Oka, S. Chem. Eng. J. 2003, 96, 157- 169. (2) Oka, S.; Ilic, M.; Dakic, D.; Grubor, B.; Komatina, M.; Barisic, V.; Arsic, B.; Manovic, V. Single Coal Particle Behavior in Fluidized Bed Combustion: Recent Results Achieved in Vinca Institute. Proceedings of the ASME-ZSITS International Thermal Science Seminar, June 11-14 (Bled, Slovenia) 2000, 83-92. (3) Komatina, M. Temperature of Coal Particle during Combustion in Fluidized Bed. Ph.D. Thesis, University of Belgrade, Faculty of Mechanical Engineering, Belgrade, Serbia and Montenegro, 1997. (4) Komatina, M.; Oka, S.; Grubor, B.; Voronjec, D. Experimental Investigation of Heat Transfer a Bubbling Fluidized Bed and Large Particle, Proceedings of the 10th International Heat Transfer Conference. (Brighton, England) 1994, 215-220. (5) Ross, I. B.; Patel, M. S.; Davidson. J. F. Trans. Inst.Chem. Eng. 1981, 59, 83-88. (6) Yates, G.; Walker, R. Partical Temperature in Fluidized Bed Combustor, Fluidization; Cambridge University Press: 1978; pp 241-245. (7) Stubington, J. F. Chem. Eng. Res. Des. 1985, 63, 241-249. (8) Prins, W. Fluidized Bed Combustion of a Single Carbon Particle. Ph.D. Thesis, University of Twente, Enschede, The Netherlands, 1987. 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