To produce nitrogen from air, PCI uses hollow-fiber membrane technology that allows oxygen to permeate the fibers, leaving high-pressure nitrogen as the product.
The membrane consists of a bundle of selectively permeable hollow fibers. It separates nitrogen from atmospheric air by the principle of selective permeation across the membrane wall. The “fast” gases (oxygen, carbon dioxide, and water vapor) permeate the membrane wall much faster than the “slow” gas (nitrogen).
The membrane separates the original gas mixture into two streams: the permeate and the product. The permeate is a mixture of concentrated oxygen, carbon dioxide, and water vapor that vents to the atmosphere. The product is high-pressure nitrogen that exits the downstream end of the membrane at near feed-air pressure and is delivered to the end user. A supplemental booster can be used if further compression is required.
The purity of the product can be adjusted by setting the operation conditions – nitrogen purity increases as nitrogen flow rate decreases and vice versa. This is done via a flow / purity control valve at the discharge of the nitrogen stream, after the flow meter and nitrogen analyzer, thus allowing finite control of both flow and purity.
Process Flow Diagram
PCI’s Nitrogen Membrane Systems are on-site generators that produce nitrogen from the atmosphere at the point of use. By producing nitrogen on-site, users can save at least 50% in operating costs and eliminate the logistics associated with the liquid nitrogen supply chain of transports and pumpers.
Our systems have 3 main components:
1. The Air Module consists of a diesel or electrically driven feed-air compressor. The air compressor takes in ambient air and compresses it to 10-25 times atmospheric pressure. The compressed air then passes through an oil separator and is after-cooled, thus allowing water and oil vapors to condense and drop out from the air flow.
2. The Membrane Module is where the air pretreatment system employs a series of filters to clean and dry the air prior to exposure to the membrane separators. The clean compressed air travels through a reheater to keep any remaining moisture in the vapor phase. These are critical protective measures required for the longevity of the membrane fiber. The reheated air then passes through the membrane separators where the “fast” gases are ejected as waste and the nitrogen product is collected and delivered at high pressure to the Booster Module.
3. The Booster Module consists of a diesel or electrically driven booster compressor. Here, the nitrogen gas that is delivered from the membrane module is compressed to a higher pressure through 2-4 stages of compression, depending on the system and requirements.
In the design and integration of the major components of our nitrogen membrane systems, PCI also takes into account the minor details to optimize the efficiency of the system. This can range from:
- The class rating of engines for long-term performance, to
- The design of air pretreatment to minimize pressure drop for maximum nitrogen recovery efficiency and minimal maintenance, and to
- A quick and accurate air reheating system for stable control of output.
– Just to name a few. Please feel free to contact any of our experts to learn more.