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

Nitrogen generator SN 1750

This generator provides the required nitrogen

The European Directive RoHS-WEEE on the interdiction of the
use of hazardous substances shall be in application In the electronic
industry as from 01.07.2006, resulting in the obligation to apply
the lead free brazing process.

Lead free solders require an increased processing temperature
involving significantly higher oxidation. The N² inert gas atmosphere
diminishes oxidation and provides therefore a simpler process
and improved soldering quality.

Due to its property to be not reactive, colourless and non-toxic,
nitrogen is an extremely useful industrial gas for application in
various techniques. For its characteristics to maintain and to improve
the quality of certain products, nitrogen is normally used as
protective gas in various processes. But how is nitrogen used
actually, resp. which logistic system delivers nitrogen to the consumer ?

At present, nitrogen supply is proposed in steel cylinders,
cylinder bundles or from tank installations. This is no longer
up to-date. Meanwhile there is the technology of nitrogen
generation on-site, well-established since more than 20 years,
with purity grades of up to 99,999 % (5.0) by use of locally available
compressed air. Due to its ultra rapid amortisation of only one year,
the nitrogen generator is there to replace the intricate logistics
for provisioning with cylinders or from tank installations.
The on-site nitrogen production by generator is a very attractive
option to the conventional provisioning with cylinders, nitrogen
bundles, or from tank installations which very often are over
dimensioned or provide unnecessary high purity grades.

How does it work ?

The nitrogen generator is fed with normal compressed air,
as it is available at nearly any business site.
Filter units mounted upstream clean the incoming
compressed air.

The technology that provides a continuous nitrogen gas flow
of super pure and even ultra pure quality is called
Pressure Swing Adsorption (PSA). This technology is
operated under use of two molecular sieves made of specific
carbon (CMS), which eliminate oxygen and carbon dioxide
molecules from the compressed air. Both sieves are switched
alternating from filter mode to regeneration mode and ensure
a continuous nitrogen gas flow.


Demand of nitrogen is not on a constant level in most business
operations. Requirements under varying specific application
processes fluctuate from a few litres per day up to very high
volumetric flow rates per hour. The nitrogen generators supply
between 0,2 up to 1500 Nm³/h at purity grades of 95 % up to 99,999 %.
By use of the “in-house air fractionation plant” nitrogen is permanently
available at steady high quality. The generators are easy to operate,
with small space requirements and cause only negligible running costs.

Both wall- and floor mounting versions are available.
The nitrogen generator only needs to be connected to the compressed
air supply line, and the inlet valve of the generator just be opened,
then the in-house air fractionation plant starts to produce
nitrogen. Built-in filters ensure the continuous good quality
of incoming compressed air.

Benefits of the generator

By comparison to conventional gas steel cylinders, bundles or
tank installations, the benefits for the operator are considerable:

- constant high quality of nitrogen

- permanent assured availability

- low installation costs

- negligible running costs

- easy and safe operation

- no handling costs as for steel cylinders or gas bundles

- no safety hazard as for steel cylinders.

Cost savings of up to 80 % compared to conventional nitrogen
gas cylinders are achieved.

By use of the nitrogen generator steel cylinders or gas bundles
may be replaced at any place where nitrogen is needed.
Nitrogen being used as protective gas or process gas,
its potential for the most various applications is nearly unlimited.
The generator presents a safe, easy and self-operated nitrogen
supply source for the user.

Producing High-Purity Nitrogen

Published in edition 7-8/2004 of German periodical DRUCKLUFTTECHNIK

Due to the further development of special fibres which filtrate compressed air
very efficiently, nitrogen purity values of up to 99,9 % are achieved in the membrane
range.
This procedure is an alternative to the PSA-technology (Pressure Swing Adsorption,
and to the conventional supply by steel cylinders, bundles or tank installations.
The gas production is carried out directly on site by use of the competitive and
technically mature membrane technology. These nitrogen generators are appropriate
to replace anywhere gas cylinders or bundles, where nitrogen supply is required,
for ex. as inert gas, or process gas, as well as for the control of ripening in the food
stuffs sector. By use of these nitrogen generators, the user has at its disposal
a simple, reliable nitrogen supply line being self operated. The generators are fed
with normal compressed air being available in almost any company. The compressed air
is purified by filter elements mounted upstream of the diaphragm, the flow then
subsequently enters the membrane module, consisting of manifold small hollow fibres. The various components contained in the air – such as water vapour, oxygen, nitrogen, rare gases and carbon dioxide – diffuse at different speed through the hollow fibre membrane, according to their respective molecular structure. Oxygen, carbon dioxide and hydrogen have a high diffusion rate and are eliminated from the air mixture very rapidly. Nitrogen having a low diffusion rate, permeates very slowly through the hollow fibre diaphragm and is therefore concentrated during this process. Purity value of nitrogen supply is subject to the flow speed. By variation of pressure and quantity the nitrogen generator may be adjusted exactly to the required purity and nitrogen supply quantity. The core piece of the generator, the hollow fibre membrane, is manufactured from synthetic material within a complex process under accurately defined temperature and pressure conditions, and involving a specific solvent. Length and arrangement of the individual hollow fibre diaphragm determines the performance of each nitrogen generator.
Demand of nitrogen is not on a constant level for most business operations. Indeed
nitrogen supply may vary from a few litres per day up to very high volume flows per
hour, in accordance to purity data requirements related to different applications.
The nitrogen generators supply between 0,1 and 2.000 m³/h at purity values from 95 %
up to 99,9 %.
By use of the “own in-house air separation unit”, nitrogen is available perpetually and
in constant high quality. The generators are easy to use, have a minor footprint and
cause only unimportant running costs. The own air separation unit only needs to be
connected to compressed air supply, after opening the valve of the nitrogen generator,
the unit starts to produce nitrogen at purity of up to 99,9 %. The built-in filters guarantee the constant good quality of incoming compressed air. Cost savings of
up to 80 % may possibly be achieved in comparison to the conventional nitrogen
steel cylinders.