Comparative Experiment on Tar Removal Methods
in Fixed Bed Gasifier
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Author:P. Vijayakumary and P. Venkatachalam
p-ISSN:0024-9602, e-ISSN:2582-5321, Vol:97, Issue:apr-jun
DOI: https://doi.org/10.29321/MAJ.10.100379
Abstract
Gasification is a thermo chemical transformation of a combustible solid in the presence of
gaseous compound to produce producer gas, which is a mixture of Carbon monoxide,
Hydrogen, Nitrogen, Carbon dioxide, Methane and traces of other hydrocarbons more
commonly known as tar, resulting from an incomplete destruction of volatiles during different
stage of transformation in the gasifier. Tar will impose serious limitations in the use of
producer gas due to fouling of downstream process equipment, engine wear and high
maintenance cost. Tar can be removed from producer gas by chemical and physical methods.
Present study was carried out to study the removal of tar from selected biomass through
physical method and catalytic cracking method. Catalytic cracking of tar was done with
dolomite as tar cracking catalyst was carried out in this study. The selected biomass for the
study was wood, arecanut husk and coconut shell. A dry filter with carbonized porous
charcoal as bed material was designed and developed with a diameter of 15.5 cm, filter bed
height of 60 cm, height of filter 90cm, superficial velocity of 0.06 m/s and residence time of 10
seconds to remove the tar coming after two condensers. By employing the filter, a tar
conversion efficiency of 90.5 per cent was achieved. To reduce the tar further, dolomite was
used as the catalyst. As the catalyst was added in the gasifier, the temperature gets increased
from 675oC to 935 oC and the tar produced gets cracked in the gasifier. A tar conversion
efficiency of 96.9% was attained by using dolomite as a catalyst. The mass closure and the
energy closure for the gasifier were calculated as 98.04% and 98.55% respectively.
Key words : Gasification, tar, catalytic cracking, filter, dolomite