Analysis for numerical optimization on square fluidized bed with altering structural parameters and internals reinforcement

doi:10.16085/j.issn.1000-6613.2017.06.005

Abstract

Abstract: Analysis on fluid dynamic behavior of multi-functional fluidized-bed reactor by numerical simulation method can reduce the amount of scale-up experiments,as well as find out the description of the reactor structure in biological wastewater treatment. This paper takes the convenient square fluidized-bed for consideration on construction(civil engineering). Three kinds of changing structural parameters like rising area to drop area ratio(A_d/A_r),annular area to drop area ratio (A_b/A_r)and distance between draft tube and liquid surface to the height of tube ratio(H_t/H_dt),added with two inner-components(cross-shaped internal and funnel-shaped internal),were investigated to inspect liquid feature response behavior under different liquid velocities and gas-holdup situations,aiming at looking for the optimization of structure and operating conditions for realizing high-efficiency oxygen mass transfer,energy conservation and shortcut nitrification-denitrification. The results indicated that A_d/A_r,A_b/A_r and H_t/H_dt mainly influence distribution and peak of liquid,the direction and velocity of liquid at the bottom and effective rectification above diversion tube,respectively,which is recommended to take 1.25,1.2 and 1/8 in due order. Based on the optimization of structural parameters,the coupling effect of two inner-components in fluidized-bed is able to satisfy the requirement of low liquid velocity and gas-holdup in different biological stages. It has been proved that numerical simulation of CFD can achieve the functional development of reactor under different wastewater treatment systems. The square fluidized-bed reactor with optimized structural parameters and inner-component has the characteristics of strengthening mass-transfer and region functionalization,which makes the combination of these two aspects and fulfill the object of efficient energy utilization and research and development cost reduction.

Key words: gas-liquid flow, fluidized bed, structural parameters, internals, CFD

摘要： 借助数值模拟方法分析多功能结构反应器内部的流体力学行为，可以减少放大实验的批次，获知反应器结构关于废水生物处理功能区划的描述。以土建工程便利的正方形流化床为研究对象，通过改变下降区和上升区面积比（A_d/A_r）、环隙过流区和上升区面积比（A_b/A_r）、导流筒与液面距离和导流筒高度比（H_t/H_dt）3种结构参数，并添加十字型挡板和漏斗型导流板两种内构件，考察各种状态下液速（U_L）和气含率（ε_G）的流体特性响应行为，在实现高效氧传质、节能与短程硝化反硝化方面寻找结构优化和操作条件优化的空间。结果表明：A_d/A_r的改变主要影响液速的分布及其峰值，取1.25；A_b/A_r主要影响流化床底部的液速的大小和方向，取1.2为宜；H_t/H_dt主要影响导流筒上方液体受到的有效整流作用，取值1/8。在结构参数优化的基础上，两种内构件对流化床的耦合作用能够满足生化流化床技术对低液速和各生化阶段气含率的需求。结果证明了采用CFD数值模拟可以实现废水处理不同目标体系下反应器功能化开发，结构参数优化和内构件置入的正方形流化床反应器具有强化传质与区域功能化的特征，两个方面的结合可以实现能量高效利用和降低研发成本的目标。

关键词: 气液两相流, 流化床, 结构优化, 内构件, 计算流体力学

CLC Number:

X703

CHEN Zisheng, ZHANG Tao, MAI Lijie, WU Jinhua, HU Chengsheng, WEI Chaohai. Analysis for numerical optimization on square fluidized bed with altering structural parameters and internals reinforcement[J]. Chemical Industry and Engineering Progress, 2017, 36(06): 1997-2009.

陈梓晟, 张涛, 麦礼杰, 吴锦华, 胡成生, 韦朝海. 正方形流化床结构参数改变和内构件强化的数值模拟解析[J]. 化工进展, 2017, 36(06): 1997-2009.

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