浆态床内颗粒浓度分布的研究

INVESTIGATIONS ON AXIAL SOLID CONCENTRATION DISTRIBUTION IN A BUBBLE SLURRY COLUMN

1 前言浆态床内固体颗粒可以是反应物、生成物、固体催化剂或催化剂载体。固体颗粒的大小和浓度分布与其他流体力学因素相互作用,可以改变过程的传质、传热性能,进而影响反应的转化率和选择性。尤其是对强放热催化反应,作为催化剂的固体颗粒,其浓度分布不同,造成了反应器内各处反应速率的差异,从而引起各处不同的温度效应,结果导致反应速率的更大差异。Serpemen 和 Deckwer 对 F—T 合成、CO 甲烷化和丁炔二醇加氢过程中催化剂分布对转化率影响的分析,证明在设计反应器时必须考虑固体颗粒浓度分布。

This paper presents some new experimental data for axial solid concentration distribution in a bubble slurry column(BSC)of 10 cm i.d.under steady-state conditions.The slurry samples were synchronously withdrawn from BSC by eight sampling valves which a installed on the side of BSC. The three phase system consisted of air,water,and quartz sand.The average particle diameter of 107.5μm,180 μm were used,the gas velocity operated was between 0.02 to 0.2 m/s,the static slurry heihgt ranged from 1.6 to 2.4 m,and the slurry concentration from 0 to 15 w%. In this investigation,the solid particle concentration distribution was found to become uniform with increasing gas velocity,and slurry concentration,or decreasing particle diameter.According to the mechanism of particle suspension,the results were explained by Peclet Number obtained from the sedimentation-dispersion model.The solid particle concentration distribution was indepedent on static slurry height.Eventually,an empirical correlation proposed for Pectlet Number was presented as follows: Pe=0.383Fr-^(0.0070)Ar^(0.49)(1-C_p)^(0.046) Moreover,average gas holdup was measured,and the qualitative dicussion was given by means of bubble size and gas rising velocity.