使用旋轉窯焚化爐焚化稻殼之數值模擬分析

Numerical Simulation for the Combustion of Rice Hulls inside a Rotary Kiln Incinerator

吳中興(Chung-Hsing Wu) ； 李志萍(Chih-Ping Lee)

《農業機械學刊》 13卷1期 (2004/03) Pp. 17-32

https://doi.org/10.30062/JAM.200403.0002

摘要

稻殼為台灣主要的農業廢棄物之一，若是沒有經過妥善地處理，大量的稻殼囤積則會對於環境造成衝擊。稻殼之高位發熱量(HHV)為3036 kcal/kg，屬於高熱值之廢棄物，且燃燒後不容易產生毒性廢氣，因此適合以焚化方式處理。惟固定爐床式焚化爐不適合處理稻殼焚化，因此本文以旋轉窯焚化爐之操作特性，進行稻殼焚化之數值模擬分析。本研究以計算流體力學(Computational Fluid Dynamics，CFD)軟體，模擬旋轉窯焚化爐稻殼焚化之3D燃燒流場。旋轉窯焚化爐之流場為紊流燃燒反應流場，假設燃燒流場已達到穩態。本研究之紊流模式採用標準k-ε模式；燃燒模式則採用渦流消散模式(Eddy-Dissipation Model，EDM)。模擬結果顯示，在過剩空氣量100%之操作條件下，旋轉窯焚化爐內之平均溫度為1309K，氣體滯留時間為6.5sec，焚化效率為96.85%。由模擬結果得知，旋轉窯焚化爐需要加掛二次燃燒室，以提高焚化處理之品質。

關鍵字

稻殼 ； 旋轉窯焚化爐 ； 計算流體力學 ； 標準k-ε模式 ； 渦流消散模式

並列摘要

The rice hull is one of the main agricultural wastes in Taiwan. If we do not dispose them properly, they will accumulate and cause a great impact on the environment of the rural area. Rice hulls possessing considerable thermal energy, of which higher heating value reaches 3036 kcal/kg, are good traditional fuel before. As burning process do not form toxic gases, rice hulls are suitable to be treated by combustion method from the standing point of thermal recovery. However, an incinerator equipped with fixed hearth fails to burn rice hulls properly. Therefore, we tried to evaluate the effects of burning rice hulls by a rotary kiln incinerator. This study utilized CFD (Computational Fluid Dynamics) software to simulate the burning rice hulls inside the rotary kiln incinerator. The flow field was regarded as 3D, steady state and turbulent flow field. And also, the phenomenon of combustion should be considered in the flow field. The standard k-ε turbulent model and the combustion model EDM (Eddy Dissipation Mod el) were adopted in this study. The results revealed that the average temperature, the retention time of flue gas, and the combustion efficiency were 1309 K,6.9 sec, and 96.85%, respectively, when the excess air was supplied at the rate of 100% theoretical air. Judging from the results, we suggested that the secondary combustion chamber should be added in order to improve the overall performance.

並列關鍵字

Rice hulls ； Rotary kiln incinerator ； CFD ； Standard k-ε turbulent model ； EDM