Membrane distillation is a thermal process in which only vapour molecules can pass through a hydrophobic membrane.
The driving force for the separation is the vapour pressure and not the total pressure, as with reverse osmosis. Increasing the temperature of the feed increases the vapour pressure and therefore the vapour pressure gradient, which is the driving force.
Membrane distillation equipment consists of several stages, or effects, leading to improved separation and greater energy efficiency.
As with the case of evaporation, the membrane distillation process is not limited by equilibrium; thus, the desired water recovery factors and reject concentration can be achieved. Unlike reverse osmosis, there is no equilibrium imposing a limit upon the separation.
Membrane distillation has a number of advantages that make it very competitive compared to other techniques. The main ones are:
Membrane distillation has been successfully used in the following applications:
Extraction from petroleum
Mining and industrial processes
UIHE offers its customers the design and implementation of a membrane distillation separation process. Specifically, there are two complementary treatment options, designed for different treatment volumes:
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