渦旋式流體化床燃燒爐中以煙氣迴流燃燒木屑之研究

Combustion of Sawdust in a Vortexing Fluidized Bed Combustor with Flue Gas Recirculation

胡駿軒(Chun-Hsuan Hu)

指導教授 ： 錢建嵩

中原大學/工學院/化學工程研究所/碩士(2012年)

https://doi.org/10.6840/cycu201200618

摘要

木屑是一種易取得之生質物燃料，應用於流體化床燃燒爐時，普遍出現CO排放濃度過高之情形，本研究為解決此問題，使用渦旋式流體化床(VFBC)，藉由切線加入之二次風，增加細粒子在爐內燃燒的停滯時間，並使用煙氣迴流，固定釋熱量130,000 kcal/hr，改變床溫、過量氧率、床內計量氧及粒徑大小，探討操作參數對燃燒份額、爐內溫度分佈與污染物排放濃度的效應。
結果顯示，床溫對燃燒份額影響不大，於固定過量氧率時，改變床內計量氧造成二次風送氧量的差異，對於飛濺區與二次風注入區燃燒份額影響顯著，及粒徑越大床區燃燒份額越高；CO排放濃度隨著床溫、過量氧率、床內計量氧及粒徑增加而降低，其中粒徑效應影響最大，最小粒徑(354 μm)與最大粒徑(932 μm)CO排放濃度分別為1759及849 ppm，以RDF(ψ6×15 mm)之11 ppm為最低；不論操作條件為何，NOX排放濃度之變動不大，均低於法規標準，顯示木屑是一種乾淨的生質能源。
整體而言，木屑於VFBC燃燒，床溫750℃、過量氧率70%及床內計量氧100%為最佳操作條件，雖CO排放濃度過高，但適度的改變操作條件，或是製備成RDF燃料，於流體化床燃燒爐應用頗具潛力。

關鍵字

流體化床 ； 生質物 ； 木屑

並列摘要

Sawdust is an easily available bio-fuel, it usually has high concentration of CO emission when using in a fluidized bed combustor. In this study, combustion of sawdust was investigated in a vortexing fluidized bed combustor with flue gas recirculation. The second air was introduced into the freeboard tangentially to enhance the residence time of fine fuel particle in the combustor. Bed temperature, excess air ratio, stoichiometric oxygen ratio in the bed and particle size were studied to compare the difference of combustion proportion, axial distribution and pollutant emissions.
The results showed that the combustion proportion had less effect by bed temperature, stoichiometric oxygen ratio in the bed share impact for splashing zone and secondary air injection region significantly. Besides, the larger particle size, the higher the combustion proportion in the bed.
CO emission decreased as bed temperature, excess oxygen ratio, stoichiometric oxygen ratio in the bed and particle size increased. The particle size had the greatest impact for CO emission. The CO emission decreased from 1759 to 849 ppm when the particle size of sawdust from maximum to minimum. The lowest CO concentration 11 ppm was obtained while RDF employed. The effect of operation conditions on NOX emission is minimum, and NOX emission is below regulation. Therefore, sawdust is a clean bio-fuel.
Generally speaking, the optimum operating conditions is at 750℃, with 70% excess oxygen ratio and 100% stoichiometric oxygen ratio in the bed. Although the CO emission is too high, the change of operating conditions suitability or prepared it to RDF fuel. It still has much potential using in FBC.

並列關鍵字

fluidized bed ； biomass ； sawdust

參考文獻

蘇冠彰, “渦旋式流體化床燃燒爐中燃燒木屑之研究,” 中原大學化學工程研究所碩士論文, 1-99 (2006).

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