Experiments were performed using olivine, magnesite, and silica sand as bed material. Grot and birch were tested as fuel. The experiments were carried out in a 75 KWfuel bubbling fluidized bed gasifier at 20 bar, using Steam/Oxygen as a gasifying agent. Produced gas composition, tar production, and carbon conversion efficiency were examined. Olivine and magnesite showed good resistance against attrition and agglomeration. Stable bed temperature with no signs of defluidization or sintering were observed during the experiments. Silica sand cannot be used as a bed material with grot due to its high ash content. However, mild agglomeration was also observed with the birch feedstock. Carbon dioxide in the produced gas increased with increase in pressure, whereas, carbon monoxide decreased with increase in pressure. Olivine showed excellent reduction properties for tars lighter than naphthalene, whereas, magnesite performed best for overall tar reduction for grot. It was observed that fuel feeding is a big challenge for running operation at high pressure.
These tests at 20 bar were an intermediate step to validate BFB biomass gasification at 40 bar. It would be interesting to study the changes in gas composition, tar, and char formation to evaluate the performance related to carbon conversion efficiency, produced gas composition, and tar production for different bed material at 40 bar.
