Tar capture effect of porous particles for biomass fuel under pyrolysis conditions

In the low temperature gasification of wood biomass, fluidized beds may exhibit defluidization problems caused by tar. These problems may be avoided by using porous particles as a bed material to capture the tar. Using wood chips, we studied the tar capture behavior of various porous particles and the influence of fluidization on the tar capture performance under pyrolysis conditions. The results of thermobalance experiments showed that gamma-alumina, sepiolite and activated clay had high tar capture performance. The tar capture depended on the specific pore surface area and pore volume of the particles, with particles having higher pore surface and volume showing greater tar capture. Furthermore, micropores in the particles were used for capture of the tar, and this promoted carbonization. The results of a small fluidized bed experiment showed that porous particles were able to capture the tar even under fluidized bed conditions, and that defluidization did not occur at a low weight ratio of the wood chip to the bed material.