Compressed Air and Nitrogen

Compressed air generation and nitrogen production units have been installed at Haith’s birdfoods production plant in Grimsby as the company looks to improve its energy effciency and increase the shelf life of its packaged products.. The new plant installation was planned to coincide with the com-pany’s move to its brand new 2,800m2. production facility whereHaith’s had to make certain of the best energy use from the plantas well as provide for future expansion. The solution to these re-quirements and increased viable shelf life was met by the instal-lation of an energy-efficient compressed air system together witha nitrogen generator.Plant air at an average pressure between 7-10 bar and output in the range of 15-82 l/s is provided by a GA30 VSD  rotary  screwcompressor which also feeds air to a NG27 nitrogen  generator.
The variable speed drive allows automatic adjustment of flow and pressure  to match  the demands of  the generator unit and, when necessary, the flow can be uprated by adjusting the pressure set-ting of the VSD compressor. 
Modified Gas Packing (MGP) methods are adopted because many food products spoil  rapidly  in air due  to moisture  loss or uptake,reaction with oxygen and the growth of aerobic micro-organismsi.e., bacteria and moulds. Storage of perishable products in a modified gaseous atmosphere can maintain quality and extend productshelf life by slowing chemical and biochemical deteriorative reactions and by slowing or, in some instances, preventing the growth of spoilage organisms.
Nitrogen  is  ideal  for MGP  applications. A dry,  inert gas with noodour,  taste,  or  colour,  it  has  a  lower  density  than  air,  is  nonflammable and has a low sol-ubility in water and othe rfood-type  constituents.Nitrogen  does  not  support  the  growth  of  aerobic  microbes  and  there-fore  inhibits  the  growthof  aerobic  spoilage.Product presentation is also improved because the  low  solubility  of nitrogen  in  packaged products  can  be  usedto  prevent  pack  collapse.
The  working  principle of  the  NG27  units  is based  on  Pressure Swing  Adsorption (PSA)  technology and provides a continuous flow of nitrogen at desired purity by using carbon molecular  sieve  (CMS). Oxygen  is selectively separated while continuous nitrogen production is ensured at the rate of 12 - 24 m3/hr with a purity level of the order of 98-99%. This is to limit the presence of oxygen in the bird food packages to an absolute maximum of 1.4%.  If  required,  Haith’s on-site nitrogen output capacity can be doubled by the simple addition of a further generation module to the existing unit.
The entire air/ nitrogen supply pipework at  the Grimsby plant  is comprised of AIRnet modular network system. The smooth internal surface of corrosion-resistant aluminium pipes, together with self-aligning, fully sealed polymer fit tings, eliminates the possibility of leaks. It also ensures the air supply is kept clean to protect downstream equipment and production  processes. The  smooth bore  helps maintain the  desired flow rate and system pressure, thus reducing energy costs.
The compressed air system is complemented by an oil/water separator unit for ecologically-efficient collection and disposal of compressor condensate.
Commenting on the new installation, Carl Boyington, Haith’s Assistant Manager, said: “With Atlas Copco’s expertise both in compressed air and nitrogen technology, we have been able to satisfy all parties. The packed product has a sterile, longer shelf life and we have an energy-efficient system with in-built capacity for future expansion."