Pressure-drop predictions in a fixed-bed coal gasifier

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dc.contributor.author Bunt, John Reginald
dc.contributor.author Luckos, Adam
dc.date.accessioned 2012-10-08T07:23:23Z
dc.date.available 2012-10-08T07:23:23Z
dc.date.issued 2011
dc.identifier.citation Luckos, Adam & Bunt, J.R. 2011. Pressure-drop predictions in a fixed-bed coal gasifier. Fuel, 09(3):917-921. [http://www.journals.elsevier.com/fuel/] en_US
dc.identifier.issn 0016-2361
dc.identifier.uri http://hdl.handle.net/10394/7448
dc.description.abstract In the Sasol Synfuels plant in Secunda, Sasol-Lurgi fixed-bed dry-bottom gasifiers are used for the conversion of low-grade bituminous coals to synthesis gas (syngas). The gasifiers are fed with lump coal having a particle size in the range from 5 to 100 mm. Operating experience shows that the average particle size and particle-size distribution (PSD) of feed coal, char and ash influence the pressure drop across the bed and the gas-flow distribution within the bed. These hydrodynamic phenomena are responsible for stable gasifier operation and for the quality and production rate of the syngas. The counter-current operation produces four characteristic zones in the gasifier, namely, drying, de-volatilization, reduction and combustion. The physical properties of the solids (i.e. average particle size, PSD, sphericity and density) are different in each of these zones. Similarly, the chemical composition of the syngas, its properties (temperature, density and viscosity) and superficial velocity vary along the height of the bed. The most popular equation used to estimate the pressure drop in packed beds is that proposed by Ergun. The Ergun equation gives good predictions for non-reacting, isothermal packed beds made of uniformly sized, spherical or nearly spherical particles. In the case of fixed-bed gasifiers, predictions by the Ergun equation based on the average or inlet values of bed and gas flow parameters are unsatisfactory because the bed structure and gas flow vary significantly in the different reaction zones. In this study, the Ergun equation is applied to each reaction zone separately. The total pressure drop across the bed is then calculated as the sum of pressure drops in all zones. It is shown that the total pressure drop obtained this way agrees better with the measured result. (C) 2010 Elsevier Ltd. All rights reserved. en_US
dc.description.uri http://dx.doi.org/10.1016/j.fuel.2010.09.020
dc.language.iso en en_US
dc.publisher Elsevier science en_US
dc.subject Pressure drop en_US
dc.subject Ergun equotion en_US
dc.subject fixed-bed gasification en_US
dc.subject packed bed en_US
dc.title Pressure-drop predictions in a fixed-bed coal gasifier en_US
dc.type Article en_US

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