Performance Enhancement of Downdraft Gasifier with Steam Injection

Abstract

In India, ample amount of biomass is available. Gasification is the thermochemical conversion in which biomass is converted in to producer gas with partial amount of air. In spite of being a century old technology, it is not fully developed especially for electricity generation because of producer gas contaminants such as tar and particulate matter (PM). Saw dust briquettes and lignite were identified for the experimentation on 10 kWe downdraft gasifier. Effect of steam injection on performance of Downdraft gasifier was studied in present work. To improve quality of producer gas by steam injection, steam gasification system was developed. 6 kW electrical steam generator was used to generate steam and this steam was heated with dry heater mounted on steam pipeline. Steam pressure 1 atm (± 0.01 atm), temperature 121 °C (± 1°C) and flow rate 1.6 kg/hr (± 0.000032%) were maintained with temperature-pressure sensor with controller and valve. Steam was decomposed at higher temperature in gasifier reactor cause lower yield of CO and higher yield of H2 and CO2. It was observed that H2 yield of product gas significantly increase and remain in the range of 16-21%. CO yield was reduced by 10%. The combustion zone temperature was reduced 25-50 °C. Gas calorific value was varying between 1200-1400 kcal/m3 with steam injection. Cold gas efficiency was improved by 11%. Tar is diminished significantly with steam injection because of complete combustion of fuel. Tar in the producer gas in range of 60-160 mg/m3 (± 0.0022%) which maybe the good alternative fuel for engine application. Particulate was in the range of 10-30 mg/m3 (± 0.0347%). Steam gasification helps to increase calorific value by increasing H2 yield and lower tar and particulates are the general conclusion from present study.