(537d) Production of Clean Synthetic Gas from Biomass Using a Downdraft Gasifier

Biomass is considered as a potential feedstock for sustainable energy production that can be converted to chemicals, fuels, electricity etc., either by thermochemical or biological processes. Gasification is one of the thermochemical methods of converting biomass to synthetic gas (CO and H2), which could potentially be used to produce different chemicals such as acetic acid and ethanol via chemical or biological processes and/or generate electricity by using engines, turbines, fuel cells etc. However, the synthetic gas produced may contain different organic (Tars) and inorganic impurities, which have the potential to damage the process equipment used in different conversion processes. Hence, the synthetic gas has to be cleaned to remove these impurities, and the extent to which the gas has to be cleaned is dictated by the end use application. The production of tars both in terms of quality and quantity depends on various factors such as the gasifier type, type of feedstock, moisture content of the feed, feed size, gasification conditions, atmospheric conditions etc. Therefore, additional work needs to be done that can correlate tar production in different types of gasifiers under varying operating conditions. This could help establish standard tolerance limits of tars for different end use applications. Active research is being carried out currently at Mississippi State University that involves the biological conversion of synthetic gas to ethanol and acetic acid. The presence of tars in the synthetic gas is expected to inhibit the growth of microorganisms. Hence, the feasibility of this process would entail minimal tar content in the synthetic gas being produced. The conversion of biomass to synthetic gas is being accomplished utilizing a downdraft gasifier. The effect of different feedstocks such as hard wood and soft wood on the production of tars is being evaluated. Also, the effect of different operating parameters on the production and quality of synthetic gas is being studied. Tar characterization will be done and the amount of tar produced during different gasification experiments will be measured, the results of which will be presented. These results will aid in the selection of a suitable method for the destruction/removal/reforming of the tars produced, which will be the future course of research.