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Nitrogen gas costs halved

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article image MAXIGAS continuous on-site gas generation installation.

A GLOBAL speciality chemicals company has nearly halved its nitrogen gas costs by introducing domnick hunter on-site gas generation technology being adopted by leading Australian companies.

Arch Chemicals BV, has adopted the same MAXIGAS continuous on-site gas generation technology used in Australasia, at its Dublin copper and zinc omadine manufacturing facility.

The omadine biocides produced by Arch are used in market-leading marine antifouling paints and as an anti-dandruff ingredient in popular shampoo brands.

Arch relies on nitrogen to blanket Zyline, a highly flammable substance that is a key component during the manufacturing process. Inert nitrogen prevents oxygen coming into contact with flammable substances. It is also used to purge equipment.

"The company previously used bulk liquid nitrogen, but considered alternatives when a process that relied on liquid nitrogen was relocated to a different site and made nitrogen gas a viable alternative," domnick hunter market development manager John Davis said.

"Nitrogen is a production critical for Arch; any nitrogen failures could cause loss of valuable batches that have a 12-hour cycle time. Product losses would not only reduce profitability, but also cause serious storage problems if a backlog of raw materials requiring special storage built up," he said.

After installing a trial MAXIGAS unit, the company concluded it could achieve substantial cost savings and still maintain nitrogen quality by using the reliable domnick hunter pressure swing technology, which extracts nitrogen from ordinary compressed air.

"As with most chemical companies, Arch has strict health and safety procedures, so each new technology is scrutinised with a stringent hazard analysis check. The check indicated that nitrogen might potentially pose a hazard in the form of oxygen deficiency, so extra precautions were needed. domnick hunter was fully able to meet these demands by installing oxygen analysers that would immediately detect any nitrogen leaks and trigger an audible and visual alarm," said Mr Davis.

Arch installed an N2MAX112 unit supplying nitrogen gas at a purity of 99 per cent which, Arch Plant manager Keven Whelan says, achieved considerable economies "despite penalties imposed by our original supplier for exiting a 12-month contract early, we are making savings of around 45 per cent."

In addition to the cost savings, Arch has also benefited from space-saving after the removal of its bulk liquid nitrogen tank. A small multi-cylinder pack has been installed to provide an emergency backup gas supply in the unlikely event of generator failure.

Being introduced to Australia as part of a global launch by domnick hunter MAXIGAS generators are a proven technology, having been used in more than 10,000 installations worldwide.

MAXIGAS operates on the pressure swing adsorption (PSA) principle to separate larger nitrogen molecules from the air stream. This domnick hunter MAXIGAS nitrogen generation system - which can be set to supply nitrogen from 97% to 10 parts per million (99.999%) - incorporates a self-regeneration feature to minimise maintenance.

MAXIGAS units are constructed in pairs of extruded aluminium columns filled with carbon molecular sieve (CMS) material. Operating on the pressure swing adsorption principle (PSA), the two columns function alternately, with one side producing gas while the other regenerates itself.

The side of the unit being pressurised by compressed air produces a continuous stream of nitrogen, which passes through the CMS while oxygen and other trace cases are adsorbed by it.

The carbon molecular sieve differs from ordinary activated carbons in that it has a much narrower range of pore openings. This allows smaller molecules such as oxygen to penetrate the pores and be separated from the air stream. The larger molecules of nitrogen bypass the CMS and emerge as high purity gas. Purities are determined by the velocity at which the air passes through the CMS columns.

At a pre-set time, before the online bed is saturated with adsorbed gases, the system switches to regenerative mode, venting the contaminants from the CMS. As this happens, the second CMS bed comes online and takes over the separation process to ensure uninterrupted nitrogen production. An in-built oxygen analyser with alarm function ensures only gas of the required purity is delivered to the storage vessel.

Mr Davis says this CMS technology is state-of-the-art for purity of on-site gas production, and is largely maintenance-free in operation, provided it is protected against water, oil and oily gas vapours, which are the enemy of sieve and membrane technology alike.

Installation is simple and proven at applications such as Arch Chemicals. The MAXIGAS design means that if users want more gas, they simply add extra banks of generators. With this system, nitrogen is available on-demand 24/7 without the risk of nitrogen supply failures holding up production, Mr Davis says.

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