Nitrogen Membrane technology was developed by Dow Chemical Company in the mid 1980’s using a hollow polymeric fiber.
Feed air, whether provided by the customer or a dedicated air compressor is compressed, filtered, dried, and heated before passing through the membrane modules containing thousands of tiny hair-like hollow fibers. The oxygen, CO2, and water molecules permeate and exit the hollow fiber walls and vented as waste gas (35% mixture of O2/CO2/H2O). The nitrogen molecules, which differ in size, pass through the hollow tubes to the product pipeline.
This technology requires an air pressure of at least 145 psig for an efficient separation to take place; otherwise, the system requires a much higher volume of compressed air and additional modules to achieve the same production rate and purity.
Hollow membrane units have a life expectancy of 5-7 years depending onthe unit’s design purity and flow rate, air quality, and type of operating environment. Therefore, membrane modules must be periodically replaced in order to maintain flow rate and purity.
HERE’S HOW THE MEMBRANE SYSTEM GENERATES NITROGEN
- Compression: Atmospheric air is compressed and cooled to ambient temperature.
- Air Dryer: The compressed air enters an air dryer that reduces/removes water condensate.
- Air Receiver Vessel: The compressed dry air enters the air receiver vessel to assure adequate air pressure is available to the Nitrogen Membrane Generator.
- Air Filtration: The compressed air is filtered in a series of filtration stages. The first stage consists of two acetate type filters with a pore space of .1 and .01 micron designed primarily to remove water and particulates in the compressed air. The third stage is a carbon material filter designed to eliminate any residual oil from the air before it passes into the membrane modules.
- Separation: Compressed dry air enters the membrane modules and passes through bundles of semi-permeable hollow fibers. The membranes divide the compressed dry air into a stream of nitrogen and a stream of waste gases containing oxygen, carbon dioxide, and other trace gases. The oxygen, water vapor and other “fast gases’’ permeate through the hollow fiber membrane walls and are vented while the nitrogen component travels the length of the hollow fibers and captured as pure nitrogen.
- Product Receiver: Product nitrogen gas enters the optional product receiver to buffer instantaneous nitrogen demand.