Experimental And Simulation Study Of An Internally Circulating Aerated Fluidized Bed Gasifier With Concentric Cylinders
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Date
2014-07
Authors
Simanjuntak, Janter Pangaduan
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
Global energy needs in the future will continue to increase, whilst primary energy sources from fossil continue to decline. Amongst renewable energy sources, energy from biomass is a potential energy source due to its abundant supply to compliment the present fuel mix. Biomass can be converted into gaseous fuel and chemical products through gasification process which converts the chemical energy in the biomass into flammable fuel gas. This thesis presents development and characterization of an internally circulating aerated fluidized bed (ICAFB) gasifier based on indirect heating to convert the energy of biomass sawdust into producer gas. Before the actual gasifier is built, an Eulerian–Eulerian model incorporating the kinetic theory of granular flow (KTGF) was applied to model the gas–solid flow hydrodynamic in the ICAFB based on isothermal model and simulated using finite volume approach, ANSYS/Fluent 6.3. Three–dimensional geometry was used to represent the key parts of a laboratory ICAFB to investigate the effect of the changes of operating parameters on the bed material circulation as the key parameter on the real gasifier operation. The optimum parameter found from the CFD parametric study was used to develop the real ICAFB gasifier. This gasifier consists of two individual zones; a pyrolysis zone in the annulus and combustion zone in the draft tube. The annulus and draft tube are connected via orifices at the lower section of the draft tube wall to enable the solids, bed material and char to move from the annulus to the draft tube and overflows at the top of the draft tube back to the annulus. With this system, low equivalence ratio (ER) compared to the conventional bubbling fluidized bed gasifier was used. ER ranges from 0.047 to 0.075 were used in this study and produced producer gas of compositions of 3.13%, 25.8%, 8.2%, 17.39%, 41.21% for H2, CO, CH4, CO2 and N2 respectively with a heating value of about 6.96 MJ/m3 were obtained at ER of 0.051 and temperature of about 866 oC. Compared with previous sawdust air blown fluidized bed gasification results, the ICAFB gasifier is capable of producing producer gas with higher CO and CH4 fractions with maximum producer gas yield of 1.29 Nm3/h, carbon conversion and cold gas efficiency of 70.94% and 54.67% respectively.
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Keywords
aerated fluidizided , concentric cylinders