|dc.description.abstract||This study investigates that automobile shredder residue (ASR) converted into energy by fixed bed and fluidized bed gasification system with controlling at ER 0.2, temperature 900℃ and 5-15 wt.% prepared catalyst addition. The producer gas composition, products distribution, energy yield efficiency and trace pollutants (e.g. heavy metal, sulfur and chlorine) emission characteristics were also evaluated. The tested catalysts were prepared by oyster shell and their performances were discussed.
The waste oyster shell was a major matrix for manufacturing prepared catalyst. Catalyst A was directly converted from waste oyster shell to powder oyster shell via shredding. Based on the analysis results of elemental and thermogravimetric analysis, the powder oyster shell (Catalyst A) was approximately 90.55-96.86 wt.% of calcium carbonate with 1.983 m2/g of specific surface area. Catalyst B was manufactured from powder oyster shell calcined at 800℃ for 3 hours (referred as calcined oyster shell). The major composition of tested catalyst B was calcium oxide. The specific surface area was slightly increased to 4.932 m2/g. The Catalyst C was prepared by the chemical method adding sodium hydroxide and expected to form calcium hydroxide. The specific surface area of tested Catalyst C was approximately 1.978 m2/g that it was similar with that of tested catalyst A.
In the case of fixed bed gasifier and without tested catalyst addition, the heating value of producer gas and cold gas efficiency (CGE) were approximately 1.55 MJ/Nm3 and 5.22%, respectively. And the energy yield efficiency of ASR conversion was increased with an increase in tested prepared catalyst addition. In the case of 10 wt.% of tested prepared catalysts addition, the producer gas heating value increased from 1.55 MJ/Nm3 to 3.11 MJ/Nm3 (catalyst A), 3.06 MJ/Nm3 (catalyst B), and 2.67 MJ/Nm3 (catalyst C), respectively. Meanwhile, in the case of 10 wt% tested catalyst B addition, CGE was also increased from 5.22 % to 11.50 %. Overall, the prepared Catalyst A could enhance heating value and CGE resulted in high specific surface area and promotion in methane formation reaction. On the other hand, in the case of fluidized bed gasifier and 10 wt.% Catalyst A addition, the producer gas heating value and CGE were approximately 3.80 MJ/Nm3 and 25.29 %, respectively. In terms of energy conversion efficiency, the fluidized bed gasification system has better ASR energy conversion efficiency than that of fixed bed gasifier.
The heavy metals emission characteristics results indicated that chromium, copper and zinc were mainly partitioned in char under gasified by fixed bed gasifier and 10 wt.% Catalyst A addition. The Cr, Cu, and Zn partitioning percentages of char were approximately 97.54%, 85.74% and 90.07%, respectively. This is because the above tested metals have a higher volatilization temperature. The partitioning of cadmium and lead were mainly partitioned in tar or particulate resulted in their high volatility characteristics. The Cd and Pb partitioning percentages of tar and/or particulate were approximately 57.09% and 65.77%, respectively. In the case of mercury partitioning characteristics, the Hg partitioning percentage of syngas was nearly 87.24% resulted in Hg has a relatively high volatility. As for the fluidized bed gasifier system, the variation of the heavy metals partitioning characteristics was mainly influenced by the turbulent characteristics of the fluidized bed gasifier. Therefore, the most tested metals were mainly partitioned in particulate, especially for Pb partitioning characteristics was significantly varied. In summary, the prepared catalysts used in this research could enhance energy conversion from ASR via gasification. Meanwhile, the tested heavy metals emission and partitioning characteristics were also well established during ASR gasification process. Therefore, the results of this research could provide the good information for selection of gasification technologies and control strategies of metals emission in the future.||en_US|