Producer Gas Cleaning Techniques

This paper reviews various producer gas cleaning techniques developed/ applied in different biomass gasification processes. It investigates various methods for the removal of particulate matter and tar emissions from producer gas generated by various types of gasifiers. The various tar measurement protocols are inconsistent on the definition of tar and particulate matters. The producer gas if used for power generation using IC engines should be less than 50 mg/Nm³, and in the case of gas turbines a minimum particulate matter concentration of 10 ppm (weight) is needed. To control tars and particulates, various insitu (catalytic tar cracking using Dolomite/Nickel, partial oxidation, high temperature tar cracking, biomass selection, two stage gasification) and post gasification treatments (sand bed filter, wash tower, venturi scrubber, rotational atomizer, electrostatic precipitator, fabric filter, fixed bed tar adsorber, catalytic tar cracker, ceramic filter, cyclones etc) are used. In the cleaning train, collection efficiencies decrease drastically as particulate sizes fall below 1.5 μm. Heavy tar and alkali metals cause engine cylinder deposition and high temperature corrosion of turbine blades respectively. The selection of suitable biomass can improve the quality of gas. Nearly every biomass has a high percentage (60–80%) of Tar Forming Particles (PTFV). Tar is a general nomenclature for a group of compounds like phenols, Poly Aromatic Hydrocarbons (PAH), high Molecular Organic Compounds, Water-soluble organic compounds and ash particles agglomerated with organic compounds. It is easier to remove 90% particulate matter than to achieve 90% tar reduction as they form stable aerosols. A combination of insitu and post gasification treatments is necessary to condition the fuel gas for various power generating equipments. Hence, the analysis of various gas cleaning methods are important for applying them in suitable systems.