The purpose of this work is to find a correlation for heat transfer to walls in a 1296 t/h supercritical circulating fluidised bed (CFB) boiler. The effect of bed-to-wall heat transfer coefficient in a long active heat transfer surface was discussed, excluding the radiation component. Experiments for four different unit loads (i.e. 100% MCR, 80% MCR, 60% MCR and 40% MCR) were conducted at a constant excess air ratio and high level of bed pressure (ca. 6 kPa) in each test run. The empirical correlation of the heat transfer coefficient in a large-scale CFB boiler was mainly determined by two key operating parameters, suspension density and bed temperature. Furthermore, data processing was used in order to develop empirical correlation ranges between 3.05 to 5.35 m·s-1 for gas superficial velocity, 0.25 to 0.51 for the ratio of the secondary to the primary air, 1028 to 1137K for bed temperature inside the furnace chamber of a commercial CFB boiler, and 1.20 to 553 kg·m-3 for suspension density. The suspension density was specified on the base of pressure measurements inside the boiler’s combustion chamber using pressure sensors. Pressure measurements were collected at the measuring ports situated on the front wall of the combustion chamber. The obtained correlation of the heat transfer coefficient is in agreement with the data obtained from typical industrial CFB boilers.
Andersson B.-Å., 1996. Effects of bed particle size on heat transfer in circulating fluidized bed boilers. Powder Technol., 87, 239-248. DOI: 10.1016/0032-5910(96)03092-6.
Basu P., Cheng L., 2000. An experimental and theoretical investigation into the heat transfer of a finned water tube in a circulating fluidized bed boiler. Int. J. Energy Res., 24, 291-308. DOI: 10.1002/(SICI)1099-114X(20000325)24:4<291::AID-ER582>3.0.CO;2-I.
Basu P., 2006. Combustion and gasification in fluidized beds. Taylor & Francis Group, 193.
Bis Z., 2010. Fluidized Bed Boilers. Theory and Practice. Czestochowa University of Technology Press, Czestochowa, 215-227 (in Polish).
Blaszczuk A., Leszczynski J., Nowak W., 2013. Simulation model of the mass balance in a supercritical circulating fluidized bed combustor. Powder Technol., 246, 313-326. DOI: 10.1016/j.powtec.2013.05.039.
Błaszczuk A., Komorowski M., Nowak W., 2012. Distribution of solids concentration and temperature within combustion chamber of SC-OTU CFB boiler. J. Power Technol., 92, 27-33.
Breitholz C., Leckner B., Baskakov A.P., 2001. Wall average heat transfer in CFB boilers. Powder Technol., 120, 41-48. DOI: 10.1016/S0032-5910(01)00345-X.
Cheng L., Wang Q., Shi z., Luo Z., Ni M., Cen K., 2007. Heat transfer in a large-scale circulating fluidized bed boiler. Front. Energy Power Eng., 1 477-482. DOI: 10.1007/s11708-007-0071-5.
Dutta A., Basu P., 2002. Overall heat transfer to water walls and wing walls of commercial circulating fluidized bed boilers. Journal of the Institute of Energy, 75 (504), 85-90.
Dutta, A., Basu, P. 2004. An improved cluster-renewal model for the estimation of heat transfer coefficients on the furnace walls of commercial circulating fluidized bed boilers. J. Heat Trans., 126, 1040-1043. DOI: 10.1115/1.1833360.
Feugier A., Gaulier C., Martin G., 1987. Some aspects of hydrodynamic, heat transfer and gas combustion in circulating fluidized beds. Proceedings of the Eighth International Conference on Fluidized Bed Combustion, Morgantown, USA, 613-618.
Goidich S.J., 2007. Supercritical boiler options to match fuel combustion characteristic. Power-Gen Europe, Madrid, 26-28 June 2007, 9-20.
Gorliz M.R., Grace J.R., 2002. Predicting heat transfer in large-scale CFB boilers, In: Grace J.R., Zhu J.X., de Lasa H (Eds.), Circulating Fluidized Bed Technology VII. Canadian Society for Chemical Engineering, Gilmore Printing Services Inc., 121-128.
Gungor A., 2009. A study on the effects of operational parameters on bed-to-wall heat transfer. App. Therm. Eng., 29, 2280-2288. DOI: 10.1016/j.applthermaleng.2008.11.008.
Kobyłecki R., 2011. The possibility to co-fire lignite with hard coal and biomass - Operational experiences from a large-scale CFBC. Rynek Energii, 6, 151-155.
Koksal M., Gorliz M.R., Hamdullahpur F., 2008. Effect of staged air on heat transfer in circulating fluidized beds. App. Therm. Eng., 28, 1008-1014. DOI: 10.1016/j.applthermaleng.2007.06.028
Lints M.C., Glicksman L.R. 1994. Parameters governing particle to wall heat transfer in a circulating fluidized bed, In: Avidan A.A. (Ed.), Circulating Fluidized Bed Technology - IV. AIChE, New York, 297-304.
Nirmal Vijay G., Reddy B.V., 2005. Effect of dilute and dense phase operating conditions on bed-to-wall heat transfer mechanism in a circulating fluidized bed combustor. Int. J. Heat Mass Tran., 48, 3275-3283. DOI: 10.1016/j.ijheatmasstransfer.2005.03.013.
Noymer, P.D., Glicksman, L.R. 2000. Descent velocities of particle clusters at the wall of a circulating fluidized bed. Chem. Eng. Sci., 55, 5283-5289. DOI: 10.1016/S0009-2509(00)00171-8.
Pagliuso J.D., Lombardi G., Goldstein Jr. L., 2000. Experiments on the local heat transfer characteristics of circulating fluidized bed. Exp. Therm. Fluid Sci., 20, 170-179. DOI: 10.1016/S0894-1777(99)00042-4.
Reddy B.V., 2003. Fundamental heat transfer mechanism between bed -to membrane water-walls in circulating fluidized bed combustors. Int. J. Energy Res., 27, 813-824. DOI: 10.1002/er.911.
Shi D., Nicolai R., Reh L., 1998. Wall-to-bed heat transfer in circulating fluidized bed boilers. Chem. Eng. Process., 37, 287-293. DOI: 10.1016/S0255-2701(98)00039-7.
Tian Y., Peng X.F., 2004. Analysis of particle motion and heat transfer in circulating fluidized beds. Int. J. Energy Research, 28, 287-297. DOI: 10.1002/er.965.
Werther J., 2005. Fluid dynamics, temperature and concentration fields in large-scale CFB combustors, In: Cen K. (Ed.), Circulating Fluidized Bed Technology - VIII. International Academic Publishers, Beijing, 10-13 May 2005, 1-25.
Wu R.L., Lim C.J., Grace J.R., Brereton C.M.H., 1991. Instantaneous local heat transfer and hydrodynamics in a circulating fluidized bed. Int. J. Heat Mass Trans., 34, 2019-2027. DOI: 10.1016/0017-9310(91)90213-X.
Xie D., Bowen B.D., Grace J.R., Lim C.J., 2003. Two-dimensional model of heat transfer in circulating fluidized beds. Part II: Heat transfer in a high density CFB and sensitivity analysis. Int. J. Heat Mass Tran., 46, 2193-2205. DOI: 10.1016/S0017-9310(02)00528-8.
Zhang H., Lu J.F., Yang H.R., 2005. Heat transfer measurements inside the furnace 135MWe CFB boiler, In: Cen Kefa (Ed.), Circulating Fluidized Bed Technology VIII. International Academic Publishers, World Publishing Corporation, 254-260.