Master of Science in Biological and Agricultural Engineering (MSBAE)
Biological and Agricultural Engineering
Alternative energy production through biomass gasification produces combustible gases, such as carbon monoxide, hydrogen, and methane. These gases can be used for generation of direct heat, electricity, or liquid fuels through the Fischer Tropsch process. However, a major limitation of the overall process is the purity of the generated synthesis gas. The tars and particulates generated in the gasification process constitute a major impediment to the commercial use of this technology because they may condense on valves, fittings, and therefore, hinder the smooth running of an engine. This research was aimed at developing a gas characterization and testing protocol, and the removal of tars and particulates in the synthesis gas generated from a downdraft biomass gasifier. The tars and particulates sampling and analysis was based on a modified EPA Method 5. The protocol modifications were done to suit the specific characteristics of the gasifier and the generated synthesis gas. This test protocol involves gravimetric analysis of the particulates retained on a high temperature glass-fiber filter and tars dissolved in a series of solvent bottles (with acetone). Baseline studies using woodchips produced tar and particulates concentrations of 1.63 g/Nm3 +0.46 and 3.84 g/Nm3+1.16 respectively; while pine pellets produced 0.85 g/Nm3 +0.16 and 4.75 g/Nm3 + 0.07 respectively. Downstream treatment using a catalytic bed of calcined dolomite, albermale proprietary catalyst, and bag filter were designed for cleaning the raw gas. An investigation of the dolomite bed temperature on gas cleaning showed that at temperature above 750oC, about 90% and 50% of the tar and particulate were respectively removed; while at 650oC about 60% and 40% of tar and particulate were removed respectively. A combined use of the proprietary catalyst at 250oC and bag filter reduced the tars and particulate concentration by approximately 90% and 98% respectively. The exiting gas was also characterized for its heating value and found to be approximately 3.38 MJ/Nm3 +0.39 and 3.67 MJ/Nm3 +0.09 for woodchips and pine pellets respectively.
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Akudo, Christopher Osita, "Quantification of tars and particulates from a pilot scale, downdraft biomass gasifier" (2008). LSU Master's Theses. 204.