Gasification of hay in a bench scale fluidised bed reactor with emphasis on the suitability for gas turbines

Thermal gasification of pasture plants (hay) is so far considered as difficult mainly due to the high amount of inorganics (ash, alkalis). Under certain circumstances it could be an additional resource for power production. There has been some experiments to test hay in gasification plants but most lack inorganic analysis. A bubbling fluidized bed was set up and gasification experiments with extensive analysis of the gas composition was conducted. Dolomite, silica and alumina particles were used as bed material. Silica proved to work successfully at 700 °C. Ash experiments showed that at higher temperatures silica forms compounds that melt and lead to unstable gasification conditions. Dolomite proved to be not stable enough for fluidised bed conditions, since it was ground down to smaller particles and subsequently entrained. Alumina was the best bed material tested, which was used up to 750 °C with good results. The longest run was 10 h at 750 °C without defluidisation. Despite the low temperature in the process the bulk tar concentration was low. The heating value of the gas was good (4–6 MJ m−3). The concentration of sodium and potassium in the syngas after the warm gas filter at 400 °C is low enough towards a cofiring IGCC application with 10% energy input from hay.