玉米穗軸在流體化床的燃燒反應之研究

玉米穗軸的燃燒研究，以量測其在流體化床燃燒中的密度，重量損失，和體積大小的方式完成。實驗結果可以清楚的說明在燃燒過程中，熱分解和焦炭燃燒的反應。當玉米穗軸進入高溫的流體化床時，因熱傳遞的限制，僅密度較低之外莢部份(hull)產生熱分解，經由計算分析可得，揮發氣體向外之擴散通量無法驅散揮發氣體的火燄於玉米穗軸的顆粒表面外，所以在最初10秒內熱分解和燃燒現象同時發生，於是顆粒直徑減少8%。因為外莢部份之密度較低，所以平均密度增加了15-20%，當玉米穗軸之溫度已經昇高到足以開始發生熱分解時，外莢部份的燃燒現象還是存在，但已經減弱了，所以玉米穗軸之直徑減小率降低了。經過大約80秒之後，外莢部份已完全燒光且已完成熱分解，祇剩下密度較低之焦炭。最後之焦炭需要再140秒左右才能燒盡，這和理論預測值相符合。此研究結果顯示，玉米穗軸的燃燒是有系統的，可預測的，和依循數學的分析。

關鍵字

燃燒；熱分解；流體化床；玉米穗軸

並列摘要

Combustion studies have been carried out on corncobs in a fluidized bed by measuring their density, weight loss, and size during reaction. Experimental results for both pyrolysis and combustion have led to a fairly clear picture of the process involved during reaction. On initial immersion of the corncob particle in the hot fluidized bed, heat transfer limitations initially restrict pyrolysis to the outer hull of the particle (of relatively low density). The calculations showed that the volatile efflux is insufficient, to drive the volatile flame off the particle surface with the result that the particle diameter is reduced by 8% in the first 10 seconds by simultaneous combustion during pyrolysis of the outer hull. Since the hull is of lower density than the cob, the mean density of the particle rises by 15 to 20%. At that point the cob is hot enough to start pyrolyzing; this reduces, but does not eliminate, the rate of combustion of the hull so that the rate of diameter reduction is reduced. After about 80 seconds, the hull has been removed totally by simultaneous pyrolysis and combustion, and the cob has also been fully pyrolyzed, leaving the charred cob of reduced density. The final char burnout takes a further 140 seconds or so, in agreement with prediction. The results indicate that behavior of corncob combustion is systematic, predictable, and amenable to mathematical analysis.

並列關鍵字

Combustion ； Pyrolysis ； Fluidized bed ； Corncob

國際替代計量

玉米穗軸在流體化床的燃燒反應之研究

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