Master of Science in Biological and Agricultural Engineering (MSBAE)
Biological and Agricultural Engineering
The gasification of biomass produces tars and particulates. These tars and particulates create problems in the gasification systems. Tars condense on surfaces at lower temperatures, such as exit pipes and on particulate filters, leading to blockages and clogged filters. Tars also have varied impacts on other downstream processes. Due to these reasons, syngas containing significant concentrations of tars cannot be used in internal combustion engines. Thus the processes through which tars can be removed have been subject to considerable research. The objective of this research was to identify the best catalyst for for down-draft gasifiers, including the LSU AgCenter down-draft gasifier developed by Dr. Chandra Theegala. An experimental setup was designed and built to help test catalysts with tars that were similar to the ones produced by the gasifier. The experimental setup was used to substitute the gasifier for the purpose of this study. The three catalysts tested using the experimental setup were, Alumina extrudates, Dolomite and Olivine. The Albemarle alumina extrudes (henceforth also referred to as Albemarle Catalyst) were a proprietary catalyst provided by the Albemarle Corporation for experimental purposes only. ASTM 8 x 10 crystals of Dolomite from Imerys, GA was used as the Dolomite catalyst. Thermtec brand Olivine of ASTM grade 4 x 16 was obtained from Unimin Corporation, PA to be used as the Olivine catalyst. In addition, experimental runs using Silica microcrystals, supplied by Unimin Corporation, Tuscaloosa, AL, were used as a control set. Temperature, Flow rate, and Life profiles of all four samples were generated using the setup and compared. The Albemarle catalyst was tested between 300 – 500 ºC and 1 – 5 SCFH. Dolomite, Olivine and Silica were tested between 400 - 800 ºC and 1 – 5 SCFH. Both the Dolomite and Olivine catalysts performed well. Under optimum conditions, at 800 ºC and 1 SCFH, the Dolomite catalyst removed 92% (+/- 3%) of all tars. The Olivine catalyst also achieved optimum performance at 800 ºC and 1 SCFH, removing approximately 89% (+/- 4%) of all tars. Both values were inclusive of the correction factor. In comparison, the Albemarle catalyst peaked at approximately 71%, but at a significantly lower temperature of 400 ºC. Silica in comparison had a peak tar cracking effectiveness of only 66%, at 800 ºC. All three catalysts had similar life run profiles with stable plots and no particular negative trends.
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Mukherjee, Bijeet, "Screening of Tar Cracking Catalysts for Syngas Produced by Biomass Gasification" (2011). LSU Master's Theses. 1228.
Theegala, Chandra S.