On-site nitrogen generators are preferred over gas cylinders and dewars for many applications in the food and beverage industry including blanketing edible oils and packaging. Plants producing nitrogen in-house can realize a 50 percent gas cost reduction as well as savings related to improved operations efficiencies. Additionally, a nitrogen generator eliminates the expense and CO2 emissions associated with truck deliveries.
Most on-site nitrogen generators are free-standing and are housed in a cabinet or skid-mounted, depending on the amount of nitrogen needed. Set-up is easy. Simply connect a standard compressed air line to the inlet of the nitrogen generator and connect the outlet to the nitrogen line. Standard features usually include high-efficiency coalescing pre-filters with automatic drains and sterile grade after-filters.
There are two types of on-demand technologies for generating nitrogen gas: membrane nitrogen generators and pressure swing adsorption (PSA) nitrogen generators.
The choice of generator depends largely on the purity of nitrogen needed for the application being considered. For example, applications such as fire prevention require nitrogen of 95-98 percent purity and are a good fit for membrane generators. Membranes are also a good choice in explosion-proof areas as they do not require electricity. Applications such as blanketing oxygen-sensitive food products require a higher-purity nitrogen stream that can be delivered with PSA generators. In other words, a PSA system would be chosen over a membrane system when the application requires higher purities (>99%).
A good example of how membrane nitrogen generators work is the Parker Balston membrane nitrogen generator. This system uses a proprietary hollow-fiber membrane technology that separates the compressed air into two streams. The generator separates the compressed air into component gases by passing the air through semipermeable membranes consisting of bundles of hollow fibers. One stream is 95-99 percent nitrogen, while the other stream contains the separated oxygen, carbon dioxide, water vapor and other gases. The nitrogen gas steam is very dry, with dew points of at least -58°F (-50°C). Membrane nitrogen generators need no electricity to generate nitrogen, so they can be used in Class-1 explosion-proof environments without any concerns.
For PSA nitrogen generators, Parker uses high-efficiency pre-filtration to remove all contaminants from the compressed air stream, down to 0.01 micron. Filtration is followed by dual beds filled with carbon molecular sieve (CMS). The CMS beds absorb oxygen, carbon dioxide and water vapor. Cycling the pressure in the CMS beds causes all contaminants to be captured at high pressure and released at low pressure, while allowing the nitrogen to pass through.
Cycling from high to low pressure regenerates the beds and assures a sustainable stream of pure nitrogen. A final sterile grade filter removes any microbial contamination. The Parker Balston DB-30 nitrogen system produces a flow of nitrogen of at least 1530 standard ft3 at 99.9-percent purity, with dew points as low as -40°F (-40°C) - ideal for food-processing applications.
Both membrane and PSA units produce nitrogen at precise purities, flow rates, and pressures. In addition to providing significant cost savings, generating nitrogen in-house represents a sustainable approach to the supply of nitrogen. It also simplifies the production process and improves operational efficiencies.
For protecting oils and other foodstuffs from the oxidative effects of air, PSA nitrogen generators are the preferred choice for creating a 99.9 percent pure nitrogen stream (if flow is reduced, purities of 99.999+ percent can be achieved).
On-site nitrogen gas generation is the most cost-effective way to neutralize the negative effects of oxidation for edible oils and other food products.
This post was contributed by David Connaughton, nitrogen product manager and Judy Silva, members of the Gas Generation technology blog team, Parker Hannifin
To learn more about on-site nitrogen gas generation, visit www.parker.com/gasgeneration or call 978-858-0505 to speak with an Applications Specialist.