Efficient separation of air into oxygen and nitrogen by using generators facilitate manufacturing processes

Nitrogen has become essential for numerous sectors of the food industry, because the inert gas achieves bacteria-free foodstuffs and prevents oxidation. With a view to avoid the problems of storing steel cylinders, bundles or tanks, it is much more preferable to generate the nitrogen environmentally friendly close to the production site by use of generators.

Average users in the food-, or packing industry and transport business use a rather significant amount of the inert gas. However, there is not given too much thought to this specific point: nitrogen gas supplies in cylinders, bundles or liquid in tank installations are often required several times per month, and hence appear to represent a relatively small part of the overall production costs. Most of the time it is at the end of the year that more attention is given to the costs of nitrogen provisioning, when the cumulated amount of all the small expenses over the recent year is calculated. It will then be discovered that they form a significant part of the production costs which should be reduced as possibly can be done. Nitrogen supply by cylinders, bundles or tanks holds other disadvantages: it is time-consuming and the regulations in regard to transportation of hazardous goods need to be observed. Moreover there are some security risks: a cylinder could topple down, or else be suddenly emptied during production.
The generator is now frequently the attractive alternative to this conventional nitrogen provisioning. The generator allows for one’s own nitrogen production on site by use of compressed air, in precisely the required quantity and purity, and independently from any external supplier. The generator technology eliminates the oxygen from the air and achieves the required purity of nitrogen.
The user may decide between two different technologies depending on the mode of application.

Membrane technology

For storage or packing the residual oxygen content must not exceed 0.5 %. In this field of application the membrane technology is used. The pores size of the hollow fibre membranes utilised here are designed in such a way that the smaller oxygen molecules diffuse through the outer side of the hollow fibre membrane, whereas the bigger size nitrogen molecules are passing through the membrane. Based on this apparently easy principle the separation between oxygen and nitrogen is operated. By adjustment of the volume flow the retention time of the air inside the membrane is extended or reduced, and thereby also the concentration of nitrogen is increased or reduced. The hollow fibre membrane also offers the advantage of being operated without electric power and is almost free from wear.
In order to ensure a high purity of the nitrogen, the Inmatec generators provide extra activated carbon- and fine filters. These elements filtrate the compressed air and eliminate volatile and solid hydrocarbon down to >0,003 mg/m³, and also all aerosol elements and particles up to 0,01 µm/m³.

PSA technology

Highest levels of nitrogen purity are generated by the so-called PSA-technology (Pressure Swing Adsorption). These plants are operated by use of a specific activated carbon with the characteristic to absorb oxygen molecules from the compressed air. In order to ensure continuous operation mode, the PSA generator is composed of two recipients containing the activated carbon, which are operated in altering mode for production or regeneration. Depending on the required nitrogen quantity, the fill time of both activated carbon recipients is longer or shorter. All models of Inmatec PSA nitrogen generators are controlled by a Touch-Control-Panel (TCP). Due to this feature the user has the possibility to precisely regulate the flow rate on the outlet of the generator, and thereby to customise the residual oxygen content in accordance to the production process and consequently to optimise the consumption of compressed air. By use of this Touch-Control-Panel (TCP) it is also possible to monitor the concentration of residual oxygen as well on the generator unit itself, but also, in case of existing network connection, on an external PC. Hereby the relevant process parameters are provided to the quality assurance system.

Profitable solution

Due to the minimal operating costs when producing the nitrogen on site, significant cost savings may be achieved, compared to the conventional nitrogen provisioning with cylinders or bundles. Furthermore, the effort of repeated orders, and the handling, storage and replacement of cylinders or bundles, or tanks, very often necessary at inappropriate moments, is now omitted. The generator technology allows for nitrogen production precisely when the gas is needed. Hereby the risk of disruption of nitrogen supply during the production process is also avoided. The pressure monitoring prevents surplus production and automatically switches the generator into stand-by mode, if nitrogen demand has stopped.

Anuga Food Tec Cologne, 10.-13.03.2009, hall 6, stand H39