DOI: https://doi.org/10.15587/1729-4061.2018.133659

CFD modelling of particle size effect on stoker coal­fired boilers combustion

Moch. Agus Choiron

Abstract


In the previous study, CFD simulation had been developed to predict combustion characteristic on the Fluidized Bed Boiler and Pulverized Boiler. The high demand on coal used for stoker-fired boilers in Indonesia the power plants provide challenge due to low thermal efficiency problem. In this study, CFD simulation is observed to predict the temperature distribution, heat of reaction, CO and CO2 mass fraction on the stoker-fired boiler. Boiler geometry is modelled as the combustion chamber until the area before economizer. The selection of boundary conditions is set according to the governing equations available in the ANSYS Fluent software. Parameter design of coal which are particle size  and properties of coal is determined to investigate the effect of the observed values. Four models are set to provide a combination of particle size and properties of coal. The solution strategy is developed to reduce instability of the simulation process. Coal combustion modelling includes several physical processes that could result in numerical stability issue when all processes are solved at once. The three stages were used to run the solution of the model. Plot of temperature distribution, heat of reaction, CO2 and CO mass fraction is generated. The maximum temperature in the 1st to 4th model is 1440.95, 1473.85, 1347.72 and 1617.17 [oK]. The amount of CO produced from each model tends to increase; respectively from the 1st to 4th model is 2.314E-07, 5.878E-07, 5.678E-07 and 7.904E-07. Based on the simulation results, it can be seen that the particle size of coal affects the combustion characteristic in the Stoker Coal-Fire Boiler.


Keywords


Stoker boiler; temperature distribution; heat of reaction; CO and CO2 mass fraction

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References


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GOST Style Citations


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Rompalski P., Róg L. Effect of the temperature of different combustion zones in the boiler grate on changes in physical and chemical parameters of bituminous coal and slags // Journal of Sustainable Mining. 2016. Vol. 15, Issue 2. P. 73–83. doi: 10.1016/j.jsm.2016.07.002 

Zhang X., Ghamari M., Ratner A. Numerical modeling of co-firing a light density biomass, oat (Avena sativa) hulls, and chunk coal in fluidized bed boiler // Biomass and Bioenergy. 2013. Vol. 56. P. 239–246. doi: 10.1016/j.biombioe.2013.05.006 

Bartoňová L. Unburned carbon from coal combustion ash: An overview // Fuel Processing Technology. 2015. Vol. 134. P. 136–158. doi: 10.1016/j.fuproc.2015.01.028 

Kobyłecki R. Unburned carbon in the circulating fluidised bed boiler fly ash // Chemical and Process Engineering. 2011. Vol. 32, Issue 4. doi: 10.2478/v10176-011-0020-8 

Improvement of Pulverized Coal Combustion Technology for Power Generation / H. Makino, H. Matsuda (Eds.). Central Research Institute of Electric Power Industry. URL: https://criepi.denken.or.jp/en/energy/research/pdf/Improvement.pdf

Statistik MINERBA 2017. Ministry of Energy and Mineral Resource of the Republic Indonesia.

Numerical study on the effect of fine coal accumulation in a coal beneficiation fluidized bed / Wang Q., Yin W., Yang H., Lu J., Zhao B. // Powder Technology. 2015. Vol. 283. P. 570–578. doi: 10.1016/j.fuproc.2014.02.015 

Zhenfu L., Qingru C. Effect of fine coal accumulation on dense phase fluidized bed performance // International Journal of Mineral Processing. 2001. Vol. 63, Issue 4. P. 217–224. doi: 10.1016/s0301-7516(01)00050-3 

The impact of coal characteristics on the fouling of stoker-fired boiler convection surfaces / Pronobis M., Kalisz S., Polok M. // Fuel. 2013. Vol. 112. P. 473–482. doi: 10.1016/j.fuel.2013.05.044 

Depman A. J. III. Stoker Boiler CFD Modeling Improvements Through Alternative Heat Exchanger Modeling. University of Iowa, 2014. 97 p. URL: https://ir.uiowa.edu/cgi/viewcontent.cgi?article=5125&context=etd

Numerical modeling of straw combustion in a fixed bed / Zhou H., Jensen A., Glarborg P., Jensen P., Kavaliauskas A. // Fuel. 2005. Vol. 84, Issue 4. P. 389–403. doi: 10.1016/j.fuel.2004.09.020 

Van der Lans R. Modelling and experiments of straw combustion in a grate furnace // Biomass and Bioenergy. 2000. Vol. 19, Issue 3. P. 199–208. doi: 10.1016/s0961-9534(00)00033-7 

Dong W., Blasiak W. CFD modeling of ecotube system in coal and waste grate combustion // Energy Conversion and Management. 2001. Vol. 42, Issue 15-17. P. 1887–1896. doi: 10.1016/s0196-8904(01)00048-6 

Ford N. W. J., Cooke M. J., Sage P. W. Modelling of fixed bed combustion // Fuel Processing Technology. 1993. Vol. 36, Issue 1-3. P. 55–63. doi: 10.1016/0378-3820(93)90010-2 

Effect of coal particle size on the proximate composition and combustion properties / Yu D., Xu M., Sui J., Liu X., Yu Y., Cao Q. // Thermochimica Acta. 2005. Vol. 439, Issue 1-2. doi: 10.1016/j.tca.2005.09.005 

Tutorial ANSYS FLUENT: Coal Combustion with Eddy Break Up (EBU) Model. ANSYS, Inc., 2012.







Copyright (c) 2018 Moch. Agus Choiron

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ISSN (print) 1729-3774, ISSN (on-line) 1729-4061