TAR REMOVAL FROM SYNGAS WITH NATURAL ZEOLITES FROM TUFFS: WET SCRUBBING AND CATALYTIC CRACKING

Natural zeolites from tuffs were tested for tar removal, during woody biomass gasification. The following compounds were considered: benzene, toluene, ethylbenzene, xylenes, styrene, naphthalene, phenol, cresols and guaiacol. Two different methodologies have been tested: addition of tuffs in a wet scrubber (30 °C) and catalytic cracking (600 °C). Wet scrubbing without zeolites was not efficient towards hydrocarbons (efficiency <5%): the use of natural zeolites allowed to reach an abatement of up to 90% for benzene. Results showed that the efficiency mostly depends on water solubility and specific adsorption capacity, while volatility has a lower impact. A slight improvement was also observed in dephenolisation, especially for low volatile and low water-soluble cresols. Catalytic cracking with natural zeolites resulted in a total (>95% dephenolisation) and a satisfactory degradation of hydrocarbons, depending on the reactivity: efficiencies ranged from 82% (naphthalene) to >95% (styrene). A comparison of technologies showed that wet scrubbing is more affected by linear velocity.