Membrane Contactors

In the membrane separation processes discussed so far, the membrane acts as a selective barrier allowing

Figure 25 Schematic of a membrane reactor to separate butadiene from n-butane.

Figure 26 Schematic showing application of a membrane contactor to remove dissolved oxygen from water. This process is used to prepare power plant boiler feed water.

Figure 25 Schematic of a membrane reactor to separate butadiene from n-butane.

Figure 26 Schematic showing application of a membrane contactor to remove dissolved oxygen from water. This process is used to prepare power plant boiler feed water.

relatively free passage of one component while retaining another. In membrane contactors the membrane function is to provide an interface between two phases but not to control the rate of passage of per-meants across the membrane. An example of this technology, in which the membrane is used in a process to deoxygenate water, is shown in Figure 26.

A hollow-fibre microporous membrane separates the oxygen-containing water from the nitrogen sweep gas. Even though the dissolved oxygen concentration in the water is very low, its equilibrium concentration in the gas phase in contact with the water is several thousand times higher. This means that oxygen permeation through the membrane down the concentration gradient to the nitrogen sweep gas is high. The membrane provides a large surface contact area between the water and nitrogen sweep gas but does not affect the relative permeabilities of oxygen and water vapour through the membrane. In this type of application, the membrane serves as a contactor or phase separator. Exactly the same separation could be achieved by running the water and nitrogen countercurrent to each other in a packed tower, but membrane contactors are much more compact. Membrane contactors are typically shell- and tube-devices containing microporous capillary hollow-fibre membranes. The membrane pores are made sufficiently small that capillary forces prevent direct mixing of the two phases on either side of the membrane.

A small market has already developed for membrane contactors to degas ultrapure water for the electronics industry and boiler feed water for power plants. The long-term goal of the process is to replace packed towers in conventional absorber-stripper operations. Practical problems related to membrane fouling and lifetime are the principal limitations.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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