Saving energy and improving product quality

The new plant installation was planned to coincide with the company’s move to its brand new 30,000 sq.ft. production facility where Haith’s had to make certain of the best energy use from the plant as well as provide for future expansion.

The solution to these requirements and increased viable shelf life was met by the installation of an Atlas Copco energy-efficient compressed air system together with a 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 screw compressor 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 setting 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-organisms i.e., bacteria and moulds. Storage of perishable products in a modified gaseous atmosphere can maintain quality and extend product shelf 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 no odour, taste, or colour, it has a lower density than air, is non-flammable and has a low solubility in water and other food-type constituents. Nitrogen does not support the growth of aerobic microbes and therefore inhibits the growth of aerobic spoilage. Product presentation is also improved because the low solubility of nitrogen in packaged products can be used to prevent pack collapse.

The working principle of Atlas Copco’s 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 Atlas Copco’s AIRnet modular network system. The smooth internal surface of corrosion-resistant aluminium pipes, together with self-aligning, fully sealed polymer fittings, 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.