Optimization of a 50 MW bubbling fluidized bed biomass combustion chamber by means of computational particle fluid dynamics |
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| Affiliation: | 1. Bioenergy 2020+ GmbH, Wiener Strasse 49, 7540 Güssing, Austria;2. Energie Burgenland Biomasse GmbH & Co KG, Industriegelände 7, 7561 Heiligenkreuz iL, Austria;3. Vienna University of Technology, Institute of Chemical Engineering, Getreidemarkt 9/166, 1060 Vienna, Austria;1. Institute of Thermal Technology, Silesian University of Technology, Gliwice, Poland;2. Institute of Advanced Energy Technologies, Częstochowa University of Technology, Częstochowa, Poland;1. Institute for Process, Energy and Environmental Technology, Telemark University College, 3901 Porsgrunn, Norway;2. University of Natural Resources and Life Sciences, Institute of Chemical and Energy Engineering, Muthgasse 107, A-1190 Vienna, Austria;1. Department of Chemical Engineering, University of Utah, 50 S. Central Campus Drive, Room 3290, Salt Lake City, UT 84112 USA;2. Reaction Engineering International, 189 E. Fort Union Boulevard, Suite 201, Midvale, UT 84047 USA;3. Department of Mechanical and Biomedical Engineering, Boise State University, 1910 University Dr., Boise, ID 83725 USA;1. Pusan Clean Energy Research Institute, Pusan National University, Busan, 46241, Republic of Korea;2. School of Mechanical Engineering, Pusan National University, Busan, 46241, Republic of Korea;3. Samcheok Thermal Power Site, Korea Southern Power Company (KOSPO), Samcheok-si, Gangwon-do, 25961, Republic of Korea;1. Thermal Engineering Group, CSIR - Central Mechanical Engineering Research Institute, Durgapur 713209, India;2. Department of Mechanical Engineering, Jadavpur University, Kolkata 700032, India |
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| Abstract: | An efficient utilization of biomass fuels in power plants is often limited by the melting behavior of the biomass ash, which causes unplanned shutdowns of the plants. If the melting temperature of the ash is locally exceeded, deposits can form on the walls of the combustion chamber. In this paper, a bubbling fluidized bed combustion chamber with 50 MW biomass input is investigated that severely suffers deposit build-up in the freeboard during operation. The deposit layers affect the operation negatively in two ways: they act as an additional heat resistance in regions of heat extraction, and they can come off the wall and fall into the bed and negatively influence the fluidization behavior. To detect zones where ash melting can occur, the temperature distribution in the combustion chamber is calculated numerically using the commercial CPFD (computational particle fluid dynamics) code, Barracuda Version 15. Regions where the ash melting temperature is exceeded are compared with the fouling observed on the walls in the freeboard. The numerically predicted regions agree well with the observed location of the deposits on the walls. Next, the model is used to find an optimized operating point with fewer regions in which the ash melting temperature is exceeded. Therefore, three cases with different distributions of the inlet gas streams are simulated. The simulations show if the air inlet streams are moved from the freeboard to the necking area above the bed a more even temperature distribution is obtained over the combustion chamber. Hence, the areas where the ash melting temperatures are exceeded are reduced significantly and the formation of deposits in the optimized operational mode is much less likely. |
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| Keywords: | Computational particle fluid dynamics simulation Biomass combustion Fluidized bed combustion chamber Deposits build-up |
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