| Summary: | 碩士 === 臺灣大學 === 機械工程學研究所 === 98 === In this study, a simple-structure fixed bed downdraft gasifier is used with rice husk as fuel to build up an experiment process. We discuss the gas composition, heating value, gas production rate, and heat output of gasifier with different operating conditions, which includes air inlet flow rate, ignition point, fuel preheating time, fuel moisture content, and fuel size. Determine the proper operation condition and use life cycle assessment to analysis the developing potential. The fuel is ignited in the gasifier and the additional fuel is fed with the upper manual feeding device. The product gas is cooled and cleaned then burn in a burner for flame observation. The gasifier temperature and air flow rate are monitored during the experiment and the gas is sampled every 10 minutes.
Experimental results of the gasifier indicate that the air inlet flow rate is lower. The equivalence ratio is between 0.010~0.057, which cause lower temperature and can only take out the volatile matter. In this condition, the gas production rate is rising as the air inlet flow rate increase. The proper ignition point is at 330mm and the heating value decreases in either higher or lower place. The preheated fuel can raise the heating value of gas with lower air inlet. Using undried fuel would cause the temperature drop down and reduce the gas heating value. The pulverized fuel would block the fuel gap and make the flame surface moving toward upper layer. The experiment No.4 with cold gas efficiency 3.02% is taken into life cycle assessment. The carbon emission of product gas is calculated as 0.051kg CO2-Eq/MJ, which is lower than using natural gas.
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