Modeling and Optimization of Biomass Gasifier with Waste Heat Recovery via Thermoelectric Effect

• Main Authors: Ming-Yung Wang, 王明勇
• Other Authors: Hsiao-Kang Ma
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/59832189449147112643

博士 === 國立臺灣大學 === 機械工程學研究所 === 102 === Based on fossil fuels in the world have limited, and usage keeps increase in the present there are quick to shorten its serviceable life. For this tendency, all countries are research and development in alternative energy sources, which includes wind energy, solar energy, hydrogen energy, ocean currents, tides, and the biofuels of this article discussion. Due to the front mention different kinds of alternative energy development would require special equipment and need to spend a great deal of money, but solid biomass fuels fixed-bed gasifier would easy to assemble and construct. It can be promoted the application of biomass fuel of agriculture wastes in local rural area. Computational Fluid Dynamic (CFD) modeling applications of the biomass gasification process help to optimize the gasifier. This study aims to investigate the impact of several physical parameters on the behavior of gasification in a fixed-bed downdraft gasifier. To that end, the study presents a comparison of the results computed using the Fire Dynamics Simulator (FDS) model with the experimental results of biomass gasification. Therefore, different sets of simulations and experiments have been performed to examine the effects of initial moisture content, equivalence ratio, high heating value (HHV), and cold gas efficiency (CGE). At the optimum operation, the equivalence rate is 0.3, the HHV can reach 5.71 MJ/m3, and the produced hydrogen concentration is 26.53 vol%. For an initial moisture content of 11.18%, the measured CGE is 66.85%, which is within the range of 65.07% to 70.44%. In general, the initial moisture content of the rice husks is suggested in between 10% to 20%. Meanwhile FDS is also application on biomass gasifier venting duct temperature distribution for investigated searching the best position of the modules to enhance the system thermal efficiency. The electrical characteristic of TEG modules at temperature difference 140℃, the maximum voltage can reach 1.33V and 1.83V at 1Ω and 5Ω respectively, however the output power attain 1.37W is higher than cooling pump power waste 0.45W, and the TEG power per unit area can reach 857W/m2. The overall results indicate that the FDS model can effectively simulate and analyze gasification performance inside the gasifier, and the performance of an improved downdraft gasifier system (IDGS) is improved by higher cold gas efficiency.