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A membrane is a selective barrier that permits the separation of certain species in a fluid by a combination of sieving and sorption diffusion mechanisms.  In terms of energy, membrane separations have an important advantage in that, unlike evaporation and distillation, no change of phase is involved in the process, thus avoiding latent heat requirements.  No heat is required with membranes, thus it is possible to produce products with functional properties superior in some respects to those produced by conventional processes.  Membrane technology also enables to simultaneously concentrate, fractionate, and purify the products.

At RAHA, Membranes are available in several different configurations such as tubular, hollow fiber, plate-and-frame, and spiral-wound. Some of these designs may work better than others for a particular application, depending on such factors as viscosity, concentration of suspended solids, particle size, and temperature.


Spiral Membranes

Spiral Membranes, are produced by winding consecutive layers of feed spacer, membrane, permeate collection channel, and membrane around a perforated center tube for permeate collection. Spirals offer the advantages of a wide range of membranes and lower energy costs due to reduced pumping requirements and higher packing density. The features of spiral construction also allow the module to be operated at elevated pressure and temperature, resulting in greater output.

View cutaway view of a SPIRAL WOUND PERMEATOR

Hollow Fiber Membranes

Hollow Fiber membranes are anisotropic (asymmetric). The self-supporting membrane can be back-flushed to maximize the efficiency of the cross-flow filtration process. This operating feature, combined with chemical stability, ensures reliability and long life expectancy. The hollow fiber geometry allows a high membrane surface area to be contained in compact modules providing high capacity while utilizing minimal space.

View cutaway view of a HOLLOW FIBER PERMEATOR

Tube Membranes

Tube Membranes consist of a membrane cast on the inside of a support tube, 1/2" to 1" in diameter. Typically, the 1" tube is used singly, and the 1/2" tubes are bundled into modules. The tubular design provides superior performance at high concentrations of solids. Plugging is minimized and high product recovery is achievable.

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