Investigations of Three Dimensional Flame Structure and Combustion Efficiency in A Municipal Incinerator

• Main Author: 蔡穎杰
• Other Authors: 陳康興
• Format: Others
• Language: zh-TW
• Published: 1997
• Online Access: http://ndltd.ncl.edu.tw/handle/33343407350252552270

碩士 === 國立中山大學 === 環境工程與科學系 === 85 === 　　The advantages of minimization, stabilization, sanitization, and energy recovery by incineration treatment have made it an effective way to deal with large amount of municipal solid wastes produced regionalyy or worldwild. This disposal scheme is more suitable for densly-populated areas, like Taiwan, Japan etc. In this paper, numerical simulations are carried out for a municipal solid incinerator (MSI) to advance the knowledge of flame structure and combustion efficiency in the combustion chamber under various operation conditions. 　　Finite Element Method (FEM) was employed for analyzing the three-dimensional, steady-state and turbulent combustion flow. In order to analyze the gaseous distribution in the combustion chamber, the devolatilization of solid waste was ignored and was simulated by gaseous methane (CH4) non-uniformly distributed along the grate of incinerator. Combustion process was considered as a two-step chemical reaction when primary underfire air entered and mixed with methane gas in the first combustion chamber (FCC). Mixing-controlled eddydissipation model was employed for predicting the reaction rates of CH4, O2, CO, H2O and CO2. 　　The results of flame structure show that grate was covered by coneshaped flame that are bent and aligned with the flow direction. The CH4 and CO were mainly confined in the FCC and over the grate where vigorous reaction takes place, but CO2 and over the grate where vigorous reaction takes place, but CO2 and H2O were largely confined in the second combustion chamber (SCC). Combustion efficiency up to 99.9% and an exit temperature between 1,100~1,300 K can achieved at 100~150% excess air. Besides, the injection of secondary air, located near the entrance of SCC, can provide better mixing and combustion efficiency. In the other hand, the three-dimensional model can achieve more reasonable results than the two-dimensional one. Comparisons with available field data show reasonable agreements.