木屑於渦旋式流體化床燃燒爐中氣態污染物排放之研究

A Study of Gaseous Pollutant Emissions from Sawdust in a Vortexing Fluidized Bed Combustor

黃煜翔(Yu-Hsiang Huang)

指導教授 ： 錢建嵩

中原大學/工學院/化學工程學系/碩士(2006年)

https://doi.org/10.6840/CYCU.2006.00417

摘要

摘要

由於石油蘊藏量有限，及燃燒化石燃料造成的CO2排放過量的問題，促進了生質燃料的研究。流體化床燃燒爐可處理多種形態燃料與低NOx排放特性，而在燃燒生質燃料的研究上佔有一席之地。本研究將針對生質燃料之氮氧化物排放做一探討。
本研究係於一總高4.6 m之渦旋式流體化床燃燒爐中進行，其乾舷區內徑為0.75 m，氣泡床區為0.8 m × 0.4 m之矩形。以木屑做為燃料，矽砂為床質，探討不同操作條件對於燃燒爐中各區段氮氧化物分布及出口排放濃度之影響。實驗之主要操作參數為：床溫、過量空氣、配風比與床溫控制方式。
研究結果顯示，大部分NO與N2O於飛濺區生成，可歸因於木屑揮發物含量高達70% 以上之故，隨後在二次風注入混合區與乾舷區進行還原。各操作條件下，N2O之出口排放濃度極小，可考慮忽略。NO之排放濃度：隨床溫之增加而增加；當過量空氣小於40%，隨過量空氣增加而增加，但過量空氣大於40%，反而隨之下降；在靜床高20 cm之條件下，NO之排放有一最低值；以床內噴水控溫，噴水量大時，NO之排放濃度將明顯高於以熱傳管控溫。
木屑之熱值不低，易於燃燒，所產生之氮氧化物排放亦低於環保法規，應為一不錯之生質燃料選擇。

關鍵字

木屑 ； 氮氧化物排放 ； 渦旋式流體化床燃燒爐

並列摘要

ABSTRACT

In this study, all the experiments were carried out in a pilot scale vortexing fluidized bed combustor of 0.75 m I.D. and 4.6 m in height. Sawdust was used as the fuel, and silica sand was employed as the bed material.
The effects of various operating conditions on NOx and N2O emissions were investigated, and the main operating parameters studied were bed temperature, excess air, and the method of bed temperature control.
The experiment results show that most formation of NOx and N2O take place in splashing zone, and then reduce in secondary air injection zone and freeboard. This is due to high volatile matter content of sawdust. Under each different operating condition, the N2O emissions are very small, and it can consider to be ignored. The NOx emission increases with the bed temperature. The NOx emission increases with excess air ratio from 10% to 40%, but the contrary result was found at a higher excess air ratio. At the static bed height of 20 cm, there is a lowest NOx emission. In addition, the amount of NOx is more with the method of water injection than heat transfer tube in bed temperature control.
Sawdust burns easily, and its heating value achieves above 3000 kcal/kg. Furthermore, the nitrogen oxides emissions from sawdust combustion conform to the environmental protection regulations. Thus sawdust could be a good choice for biofuel.

並列關鍵字

Sawdust ； Nitrogen oxides emissions ； Vortexing fluidized bed combustor

參考文獻

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