Method for High-Temperature Particle Sampling in Tar-Rich Gases from the Thermochemical Conversion of Biomass

摘要

The thermochemical conversion of biomass produces compounds in both gas and particle phases that may be regarded as contaminants. These contaminants include both particulate matter (e.g., fly ash, soot, and fragmented nonvolatilized material) and volatilized metals and tars that condense and form particulate matter during cooling. In this study a method for high-temperature particle sampling in tar-rich gases from the thermochemical conversion of biomass was developed and tested. Both a bed of granular activated carbon and a denuder were used for tar adsorption. First, the transport efficiency of particles was determined both theoretically and experimentally using a K_2SO_4 reference aerosol, and the losses were found to be smaller in the denuder than in the bed of granular activated carbon. The adsorption capacity was then tested using a model aerosol of K_2SO_4 and diethyl-hexyl-sebacate (DEHS). The adsorption capacity of the bed of granular activated carbon was found to be higher than that of the denuder. The adsorption capacity was also tested using a model aerosol of K_2SO_4 particles and tar-rich gas from a laboratory-scale gasifier. As for DEHS, the result indicated that the capacity of the bed of granular activated carbon was higher than that of the denuder; it was also found that the adsorption was incomplete when the tar concentrations increased. In addition, the bed of granular activated carbon was successfully tested during experiments using a 100 kW circulating fluidized bed gasifier. The results indicate that the tar adsorption capacity is dependent not only on the total tar concentration but also on the tar composition.