流體化床燃燒爐中通入迴流煙氣或氮氣對氮氧化物排放之效應

The Effect of Injecting FGR or Nitrogen on NOx Emission in a Fluidized Bed Combustor

邱俊賓(Jiun-Bin Chiou)

指導教授 ： 錢建嵩

中原大學/工學院/化學工程研究所/碩士(2010年)

https://doi.org/10.6840/cycu201000704

摘要

流體化床燃燒爐之操作溫度較低(700-900℃)，故爐內生成之氮氧化物係以燃料式氮氧化物(Fuel-NOx)為主。迴流煙氣(Flue gas recirculation)能有效降低氮氧化物之排放，但降低原因尚未徹底釐清。本研究為了探討迴流煙氣之效應，故在相同床下總風量、床溫、床下計量氧比及過量氧率下，比較一次風通入迴流煙氣或氮氣，對於NOx排放濃度之影響。
本研究係於一總高4.6 m之先導型渦旋式流體化床燃燒爐中進行，燃燒室底面積為0.8 m × 0.4 m，乾舷區內徑為0.75 m，二次空氣由乾舷區底部以切線方向進入爐內，注入點距分配板2.05 m。以粒徑1.4～8mm煤炭為燃料，矽砂為床質，探討操作參數對於爐床溫度、乾舷區溫度、一氧化碳排放、氮氧化物排放、燃燒效率及各區段燃燒份額之影響。
研究結果顯示，於本研究設備中，迴流煙氣是可以有效降低NOx排放濃度，迴流煙氣降低NOx排放濃度之原因，為(1)迴流煙氣可以使NOx有機會再次回到爐內進行還原反應。(2)迴流煙氣所含的CO2較多，CO2會抑制NOx生成或是CO2轉化成CO藉由與焦炭之反應使得NOx還原。

關鍵字

氮氣 ； 迴流煙氣 ； 氮氧化物 ； 流體化床燃燒爐

並列摘要

The oxidation of fuel-N is the major source of NOx formation in the fluidized bed combustor. It can be attributed to the lower operating temperature to prevent the formation of the thermal NOx. The Flue gas recirculation (FGR) technique gave significant reductions in NOx emission, but the reasons for its reduction are not clear. In order to study the effect of FGR by primary air mixed with FGR or nitrogen on NOx emissions in the fixed total primary air flow rate, bed temperature, stoichiometric oxygen ratio in the combustion chamber and excess oxygen ratio were investigated in a fluidized bed combustor.
The combustion experiments were carried out in a 0.75 m I.D. and 4.6 m in height pilot scale vortexing fluidized bed combustor (VFBC). The secondary air were injected tangentially at the bottom of freeboard, 2.05m above the distributor plate. The particle size of 1.4 to 8 mm coal was used as the fuel. Silica sand was used as the bed material. The effect of operating conditions on bed temperature, freeboard temperature, CO emissions, NOx emissions, combustion efficiency, and combustion proportion were investigated.
The results showed that the NOx emissions can effectively decreased with FGR in the VFBC. The lower NOx emissions was attributed to the following potentially reasons. (1)The FGR that allowed NOx enters the reactor again and has the chance of being reduced. (2)The FGR contains more CO2 to suppress NOx formation or promote NOx reduction through its conversion to CO by reaction with char.

並列關鍵字

Fluidized bed combustor ； Nitrogen ； FGR ； NOx

參考文獻

楊宗翰，《廢液於渦旋式流體化床焚化爐中氧化亞氮排放之研究》，私立中原大學化學工程學系碩士論文(2003)。

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