Reverse osmosis crossflow

The membrane/filtration processes have been considered in the following order crossflow gas permeation, crossflow reverse osmosis, crossflow ultraflltration, crossflow micro-filtration and rotary vacuum filtration. 

Tangential crossflow filtration Process where the feed stream sweeps the membrane surface and the particulate debris is expelled, thus extending filter life. The filtrate flows through the membrane. Most commonly used in the separation of high-and-low-molecular weight matter such as in ultrapure reverse osmosis, ultrafiltration, and submicron microfiltration processes. 

When pressurized liquid is used lo separate micrometer-size particles from fluids, the process is called microfiltration. Generally particle sizes are front 0.02 to 10 pm. Thus compared lo ultrafiltration and reverse osmosis, fluxes and pore sizes are large, osmotic pressure low. and pressures moderate. Two types of niicrofiltration processes exist, crossflow and deadend. Commercially, the former is growing at Ihe expense of the latter. 

Sengupta, S.K., Slade, J.A., and Tulk, W.S., Liquid radioactive waste processing with crossflow microflltration and spiral wound reverse osmosis, Report AECL-11270, Chalk River, Ontario, February 1995. 

On the other hand, reverse osmosis finds extensive use for the removal of dissolved metals. In most cases the technique is used in crossflow conditions, in other words the effluent flow is parallel to the membrane plane. The technique is very popular in the electroplating industry where effluent is concentrated to a point where it can be reused this represents a considerable saving in terms of chemicals and water costs. Typically, in these situations effluent flow rates are of the order of 100-300 1 min ... 

We have studied crossflow reverse osmosis, ultafiltration and microfiltration in Sections 7.2.2-7.2.4. In any such process, if a very substantial fraction of the solvent... 

A major development in filtration, which came with the first, reverse osmosis membrane process, was the fact that the flow of the fluid at the membrane snrface is tangential to it, rather than perpendicular to that surface. This has become known as cross-flow filtration (see Figure 2.21), and almost all membrane processes now operate in crossflow rather than through flow mode. Further scouring action is achieved by having the membrane medium move relative to the hquid flow, either rotating close to a stator, or vibrating. 

---