Gasification of wood in a dual fluidized bed gasifier: Influence of fuel feeding on process performance

Abstract: Gasification of wood pellets at a gasification temperature of 850°C and a fuel power of 90kW was performed in a dual fluidized bed gasifier. Pure steam was used as a gasification agent at a steam-to-fuel ratio of 0.6kgH2O/kgfuel,daf. One focus of the investigation was the influence of the position at which the solid fuel was fed into the gasifier. In one case the fuel was fed directly into the bubbling fluidized bed while in the second case the fuel was fed from the top onto the bubbling bed. With in-bed feeding much lower tar contents and a higher H2 content were observed, while with on-bed feeding the amount of product gas generated was significantly higher. A second focus of this test series was the gas composition inside the reactor. To investigate this, gas measurements were carried out at different height levels in the reactor for both fuel feeding options. It was observed that the gas composition changed drastically along the height of the gasifier. A decrease in the H2 content of about 12vol%db was measured from the lowest to the highest sampling point in the gasifier while the contents of higher hydrocarbons, CH4, C2H4, and C2H6, increased towards the gasifier outlet. [Copyright &y& Elsevier]