Abstract:
The current study reveals various features that can affect the gasification process to improve syngas quality and yield. A comprehensive study was carried out using a 24 kW downdraft gasifier to evaluate the effect of uniformly distributed air in the oxidation zone, additional throat on the gasifier internal thermal profile distribution and the overall gasification process. The effect of biomass moisture, equivalence ratio, gasifying agent type and pre-treatment of the gasifying agent on producer gas yield and composition were also evaluated. The gasifier unit was equipped with cyclone separator, wet scrubber, water gas separator, biomass filter, auxiliary filter, cooling tower and vapour compression refrigeration system. The maximum flow rate of producer gas was found to be 90-104 m3h-1 under the biomass feeding range of 30-40 kgh-1. When corn cobs and waste wood (carpenter waste) with moisture content from 5-30% were used as feed stock, with 70ºC air as the oxidizing agent, the energy value of the producer gas obtained was 6.31 and 6.66 MJm-3, respectively. The heating value was improved to 6.72 and 8.43 MJm-3 when using 150ºC air-steam mixture as the gasifying agent, with the optimum equivalence ratio of 0.30. The Methane, Hydrogen and Carbon monoxide concentration (on volume basis) were found to be 6.20, 19.32 and 21.00%. The average amount of syngas produced from one kg of corn cobs and waste wood were 2.94 and 2.62 m3, while the average amount of tar produced was 2.2 and 1.8 gNm-3 respectively. The efficiency of cleaning and cooling system were found to be 86.81 and 92.06%. The experimental research concluded that uniformly distributed air in the combustion zone as an interconnected parameter with biomass moisture level, type of gasifying medium and pre-treatment/pre-heating of gasifying agent played a vital role in affecting the syn gas production and composition.
Keywords: Gasification, Gasifier, Equivalence ratio, Gasifying agent, Pre-treatment, Syngas.
