Performance Of An Alumina Ball Packed Bed Porous Media Burner Fueled By Producer Gas

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Date
2012-04
Authors
Ho, John Chung eng
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Publisher
Universiti Sains Malaysia
Abstract
Producer gas from biomass gasification is unable to burn efficiently in conventional burner due to low burning velocity of CO which comprises of about 20% of the producer gas. Porous media burner (PMB) is a promising technology for improving combustor performance that could solve the problem. The study aims to investigate the performance of PMB fueled by producer gas from biomass gasification. A stratified throatless downdraft gasifier was used to generate producer gas with heating value of about 4-5 MJ m-3. Investigation has been done on a 2-layer alumina balls packed bed PMB with first and second layer consist of 10 mm and 20 mm alumina balls respectively. The study was done at various equivalence ratios (Φ) and heights of second layer packed bed (H). Flow rate of producer gas was kept constant at 130 LPM whereas flow rate of air was varied to produce different equivalence ratios. Increase in both equivalence ratio and height of second layer packed bed increase the maximum temperature and the volume of combustion zone. The combustion region achieved the highest temperature between 1300 K and 1550 K for all cases. CO emission generally decreases with equivalence ratio. NOx emission increases significantly when packed bed height exceeds 140 mm. But for the case of packed bed heights of 80 mm and 110 mm, it shows increasing CO emission near the lean limit. The lowest recorded emissions from the PMB were 6 ppm and 230 ppm for CO and NOx respectively. PMB with second layer height of 140 mm was found to be the best height for the current setup that manages to operate with submerged flame between the range of equivalence ratio of 0.33 and 0.71. A cyclone burner (CB) was experimented and the results were compared with the PMB for the same producer gas flow rate of 130 LPM. It produces lower maximum temperature at about 1200 K with minimum emissions of CO and NOx at 4 ppm and 350 ppm respectively. It was found that PMB has better performance than CB in general. A shell and tube heat exchanger was incorporated with the PMB for hot air production yielding maximum thermal output of 7 kW. Lean combustion in PMB generally yields better performance.
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Keywords
The performance of PMB fueled , producer gas from biomass gasification
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