以回應曲面法探討渦旋式流體化床中之淘析現象

A Study of Elutriation in a Vortexing Fluidized Bed Using Response Surface Methodology

蘇豊棋(Li-Chi Su)

指導教授 ： 錢建嵩

中原大學/工學院/化學工程研究所/碩士(2003年)

https://doi.org/10.6840/cycu200300607

摘要

流體化床操作時，如何降低粒子淘析為一重要研究課題，以往學者除了尋求淘析速率關係式外亦致力於降低淘析之設計相關研究。
Sowards(1977) 最早採用渦旋流來降低粒子淘析之設計，其特點係於焚化爐之乾舷區中加裝一排渦旋產生器，二次空氣由渦旋產生器導入乾舷區中，以降低污染排放量。Korenberg(1983) 建立首座循環式流體化床∕旋風集塵器整合型燃燒爐(Integrated Circulating Fluidized bed/Cyclone Combustor, CFB/CYC)。Nieh & Yang(1987b) 改良原CFB/CYC系統並正式命名為渦旋式流體化床燃燒爐(Vortexing Fluidized Bed Combustor, VFBC)，本論文即係採此概念，針對渦旋式流體化床降低淘析量之作用，進行深入且全面的探討。
本研究係採實驗設計法中之回應曲面法(Response surface methodology)進行研究各操作參數(一次風氣速(U1)、二次風入口管徑(do)、二次風流量(Q2)、二次風入口假想圓直徑(Ds)、及細粒子粒徑(dp))對淘析之影響，並分作兩個實驗設計表進行探討，希冀能藉由採取此一系統化之實驗設計，得到一整體之參數效應排序及重要因子間交互作用之闡述。由實驗結果顯示：影響淘析速率之主要操作變數，依重要性排序依序為：一次氣速、細粒子粒徑、二次風量、二次風入口假想圓直徑、二次風入口管徑；且一次氣速與粒徑、二次風量與假想圓直徑、二次風量與二次風入口管徑間之交互作用，此三種交互作用對淘析量影響皆巨，設計時皆應予以考慮；文中最後並提出實驗經驗式供實際設計渦旋式流體化床時採用。

關鍵字

回應曲面法 ； 渦旋式流體化床 ； 淘析

並列摘要

Elutriation of particles would increase the operation cost caused by the loss of catalyst particles from the fluidized bed reactors and decrease the combustion efficiency caused by the carry over of unburned combustible particles from the combustor or incinerator. Therefore, how to minimize the elutriation rate from the fluidized bed has become an important issue. Researchers in this field have conducted not only the academic studies but also engineering designs for reducing elutriation.
Swirl flow, used by Sowards (1977), resulted from injecting the secondary air into the freeboard through a series of swirl generators to reduce the elutriation of particles from the incinerator. A pilot scaled apparatus which was integrated circulating fluidized bed combustor with cyclone (CFB/CYC) was firstly constructed by Korenberg (1983). The CFB/CYC system was modified by Nieh and Yang (1987b), and it was named as “vortexing fluidized bed combustor, VFBC”. Based on these concepts, this study will conduct a comprehensive investigation of the elutriation in VFB.
The effects of various parameters on the elutriation will be investigated from the data obtained by using the response surface methodology (RSM), which provide a systematic and efficient experimental strategy.
This study aims to integrate the piecemeal results of previous studies by using a VFB cold model with inside diameter of 19 cm. Based on the past experiments, the dominant factors for elutriation are known as the characteristics of gas, particle and fluid dynamics within the fluidized bed. Therefore, the primary air velocity, the inlet diameter of secondary air, the flow rate of secondary air, the imaginary circle diameter of secondary air and the diameter of fine particles are chosen as the operating parameters of this study and processed in terms of two experimental design tables. The specific elutriation rate constant (K*) is the objective function. The experimental results show that the significant order of dominant factors is: primary air velocity, fine particle diameter, secondary air flow rate, the imaginary circle diameter, and the inlet diameter of secondary air. The interaction between primary air velocity and fine particle size, between secondary air flow rate and the imaginary circle diameter, and between secondary air flow rate and the inlet diameter of secondary air all exert great influences to elutriation quantity. In the end, an experimental equation is provided for adoption when designing a VFB.

並列關鍵字

Vortexing fluidized bed ； Response surface methodology ； elutriation

參考文獻

邱華逸，【流體化床中水平噴嘴分佈器對氣體徑向混合之研究】，中原大學化工所碩士論文，(2002)。

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