格栅对新型流化床流动特性影响的模拟研究

Numerical simulation of effect of grids on flow characteristics of new fluidized bed

为实现水杨酸的高效生产,提出一种以新型流化床反应器(NRFB)为核心的连续化工艺系统,内构件格栅对于NRFB内实现固体颗粒与气体高效接触具有重要作用。利用CFD模拟不同数量的格栅对NRFB内流场特性以及颗粒分布特征的影响,使用等面积环面法与均匀度指数定量地考察NRFB内颗粒分布状况。结果表明:格栅的存在能使床内轴向和径向的气相分布更加均匀;不安装格栅时,颗粒在密相段易出现中心低、壁面高的“环核流”,不利于气固相间的充分接触,安装9个格栅时,颗粒的分布均匀程度能够提升17%左右,且有更多的颗粒停留在反应密相段,有效提高反应效率。研究结果可为新型流化床的中试装置搭建及流态化操作奠定理论基础。

A new fluidized bed reactor(NRFB)is proposed as the core of a continuous process system for the efficient production of salicylic acid,and the inner component grids play an important role in achieving efficient contact between solid particles and gas in the NRFB.The effect of different numbers of grilles on the flow field characteristics and particle distribution in the NRFB was simulated by CFD.The particle distribution in the NRFB was quantitatively investigated using the equal area annulus method and the uniformity index.The results show that the presence of grids can make the gas phase distribution in the bed more uniform in the axial and radial directions;without grids,the particles are prone to“ring-core flow”with low center and high wall in the dense phase section,which is not conductive to the sufficient contact between gas and solid phases,and with nine grids installed,the uniformity of particle distribution can be improved by about 17%,and more particles stay in the dense phase section of the reaction,effectively improving the reaction efficiency.The results of the study can lay the theoretical foundation for the construction of the pilot plant and fluidization operation of the new fluidized bed,which has good guidance and reference value.