Increasing tar and hydrocarbons conversion by catalysis in bubbling fluidized bed gasifiers

The paper reports on the catalytic gasification of biomass (lignocellulosic) in bubbling fluidized beds. A review of the influence of operating conditions influencing the effectiveness of the catalytic bed is proposed. The concept of a partitioned fluidized bed by introduction of screens in the middle is also introduced and analyzed for its advantages in increasing the contact between tar and catalyst. An experimental test with a partitioned bed proved that the presence of an intermediate screen could affect the tar yield and composition. The catalyst can be present in the bed only partly, as demonstrated by a test with a bed composed of 25% catalyst and 75% inert materials giving similar tar conversion with respect to the 100% catalytic bed. The results obtained during biomass gasification are reported for a bed composed of a novel iron based catalyst. It proved to be a good substitute of Ni-oxide as catalyst for in-bed tar conversion. Furthermore, the novel catalyst is harmless and easily disposable. The iron based catalyst also preserves the content of hydrocarbons in the syngas.