变质量流动吸附床内的速度分布

Velocity distribution in axial adsorber with consideration of mass variation

在气体吸附分离过程中,吸附床内气体流动过程实质上是一个变质量流动过程.借助二维模型对吸附床内气体的速度分布进行了研究,在模型中考虑了吸附引起的质量变化和床层的径向空隙率的分布.结果表明:(1)多孔介质本身对流动有着重整作用,使流动趋于均匀分布,但是进口端的吸附剂受入口效应的影响较大,在此区域速度呈W形分布,部分区域达到流化状态;(2)在吸附步骤,速度在传质区有着较大的变化,在其他的三个步骤内,速度沿吸附剂床层近似线性变化;(3)降压步骤中,床中气体速度较高,对颗粒冲击较大,易引起摩擦和粉化,应合理控制降压速率;(4)气体吸附引起的质量变化对压力和速度有着重要影响,不能轻易忽略.

In gas separation by adsorption,the gas flow in an adsorber is virtually a variable mass flow.The velocity distribution in an adsorber was investigated by a two-dimensional model with consideration of radial porosity and mass variation caused by sorption.Four conclusions are drawn as follows.（1） Porous media themselves have a role in the gas distribution that they make the gas flow uniformly.But the adsorbent in the feed end is greatly affected by entrance effect,in this region the velocity is in a W-shaped distribution,and some parts of the region are in a fluidization state.（2） During the adsorption step there is a greater change in velocity located at the mass transfer zone,while in the other three steps the change in velocity is approximately linear along the bed.（3） During the depressurization step there is a higher velocity in the bed,which blasts the sorbent and causes the sorbent＇s attrition and pulverization,so it is better to control the rate of depressurization.（4） Mass variation has important effect on the pressure and velocity,so it can not be easily ignored.