Gas鈭扴olid Flow Behavior in the Standpipe of a Circulating Fluidized Bed with a Loop Seal

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• 作者：Xuan Yao ; Hairui Yang ; Hai Zhang ; Chengchuan Zhou ; Qing Liu ; Guangxi Yue
• 刊名：Energy & Fuels
• 出版年：2011
• 出版时间：January 20, 2011
• 年：2011
• 卷：25
• 期：1
• 页码：246-250
• 全文大小：815K
• 年卷期：v.25,no.1(January 20, 2011)
• ISSN：1520-5029

文摘

In this paper, the flow behavior of gas鈭抯olid flow in the standpipe of a circulating fluidized bed (CFB) and its influence on the system pressure balance and hydrodynamic performance have been studied. A CFB apparatus with a square riser of 0.1 脳 0.1 m in cross-section and 4.5 m in height and a standpipe of 3.0 m in height and 0.08 m in diameter were established. The standpipe connected the riser to a loop seal on one end and connected to the cyclone on the other end. The experimental results showed that the flow behavior in the standpipe is not only strongly related to the particle holdup, the structure, and the aeration flow rate of the standpipe and loop seal but also strongly coupled with the pressure drops of the rest of the parts of the CFB system. At fixed-bed inventory M_t and fluidizing gas velocity in the riser U_g, the solid circulating rate G_S increases with the flow rate of aeration air Q in the loop seal. With an increasing G_S, the pressure drop of the loop seal decreases, while both the pressure drops of the riser and cyclone increase. The flow pattern of the gas鈭抯olid two-phase flow in the standpipe and the gas鈭抯olid slip velocity change when the pressure drops of the rest of the parts of the system change. Normally, the gas鈭抯olid flow can be categorized into transient packed-bed flow (TPBF). With an increasing Q, the flow rate of downward-moving gas flow entrained by the circulating solid increases at first to a maximum value and then decreases because of the presence of bubbles in the loop seal and the bottom of the standpipe. Beyond the critical value of Q, the flow state in the standpipe becomes bubbling fluidization. The calculation results based on the TPBF agree well with the experimental data and the prediction of the transition of the flow state in the standpipe.