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EXCLUSIVE Natures Way invests in ammonia plant

29 August 2012

Natures Way invests in ammonia plant to increase cooling efficiencies, maximise product freshness and minimise its environmental impact

When Natures Way the UK supplier of packaged fresh fruit and salads to major retail and food service companies built a new processing facility, a refrigeration system using a natural refrigerant was a critical part of the design criteria.

Natures Way is a major supplier of prepped and ready to eat Salads and Fruit to many of the high supermarket chains and its philosophy from its inception some 16 years ago is characterised by its name. All of its products are fresh and natural and the company strives to build a business that is in harmony with its environment.

Where practical produce is sourced locally and the same ethos was applied to the building of the plant, materials, labour and equipment including its critical resource – a state of the art central Ammonia /Glycol refrigeration plant supplied by Dartford based J & E Hall International.

The south coast was already home to two Natures Way facilities at Selsey and Runcton when demand for fresh produce required a major expansion. The company acquired a green field site on the outskirts of Chichester which became NWF Merston offering 7,500m² of production space.

“NWF has been very pleased and impressed with our appointed contractors, such as J & E Hall, and their ability to work concurrently with the builders to meet NWF aggressive build schedule. We are delighted that we were able to go from breaking ground to manufacturing our first customer product in 38-weeks,” says Richard Sellis, Head of Engineering, Natures Way.

The project was characterised by Natures Way’s philosophy that requires a green solution for all business activities. The company prides itself on its ‘zero to landfill’ approach where as much as possible is recycled including waste water which is used to irrigate crops.

At the heart of the ‘pack house’ is the refrigeration plant which maintains the required air temperatures in preparation halls and provides chilled water to the processing equipment.

The cooling is supplied from a plant room built by J & E Hall which includes two HallScrew HSO 2035 open drive single screw compressors each sized to provide 60% of the total cooling duty and each fitted with a Fridgewatch™ compressor controller (one per compressor pack), two evaporative condensers, two stainless steel plate heat exchanger packs - ammonia flooded evaporators sized for 60% duty. These indirectly cool the water with a 25% propylene glycol solution which is ultimately used as the secondary cooling medium.

The large system volume totalling some 180,000 litres of water/glycol eliminated the requirement for a system buffer tank.

Natures Way specifications and requirements took into account the future expansion of the site and redundancy against servicing/critical system failures. These considerations provided a total cooling capacity at design conditions in excess of 2.7 megawatts.

Reducing energy consumption, carbon emissions, energy costs, maintenance and overall costs long term were essential criteria for Natures Way who takes a pragmatic but holistic approach to its business and the environmental impact which has to be minimal.

As a result one of the compressor motor packs is driven by a variable speed drive (VSD) for more efficient capacity control. It enhances the performance of the unit at part load acting as the lead compressor until the load exceeds its maximum capacity. At this point the second, fixed drive pack, automatically takes over to take care of the load and the VSD pack runs to trim the load accordingly. Also the speed of the compressor driven by the VSD can vary from 1000rpm – 2975 rpm and in so doing can reduce the running costs by up to 25% offering a payback on the cost of the VSD in less than 18 months.

The second compressor pack has been designed with soft start and capacity control is achieved by means of compressor slide valves that provide continuous variable (stepless) capacity control. Part load operation is very efficient.

The production and storage areas are temperature controlled and some incorporate positive pressure and regular air changes to comply with their customer’s requirements.

The room cooling in the production and storage areas are supplied by a series of ceiling mounted food grade coolers, which are specially coated to prevent any contaminants adhering. They are controlled and monitored by a sophisticated building management and monitoring system.

The whole plant has the capability to be monitored remotely and the system has been designed to reduce on-site man power and improve maintenance. The plant operates 24/7; downtime is not an option as a major system failure could impact their ability to maintain customer service. The ability to diagnose and affect most repairs remotely saves time and minimises manual intervention which in turn reduces maintenance costs. In the event of a serious problem, J & E Hall engineers are on 24-hour callout.

“Natures Way chose Ammonia, as it was felt it offered the best compromise between capital investment, running costs, maintenance and environmental impact,” says Nathan Bennett Projects Manager at Natures Way.

The factory’s refrigeration duty is served by a mixture of water and 25% (by weight) food safe, propylene glycol. This cooling medium, though less efficient than direct ammonia is far safer and the system is easier to modify in the future. This medium is pumped through system distribution pipe work at -7°C and controlled by valve stations located in the roof void, to serve in total 43 coolers at ceiling level and a number of different production process requirements.

Year on year Natures Way is setting a remarkable benchmark for other companies to follow by reducing its energy consumption and costs.

The company has ambitious growth plans. It has already unveiled its own branded Lasting Leaf salads as well as producing leafy bowls and trays. The fabric of the building and the services-infrastructure has been designed to meet these future plans.

In keeping with its environmental concerns, Natures Way is also actively looking at a number of environmental initiatives using biofuels. The company’s environmental commitments and blue sky thinking characterise a highly successful business.

Factory Facts
• Full height windows to allow natural light into the production space
• Silver curved roof, which blends in with the surrounding landscape and reflects heat
• Specialised temperature storage areas allowing for precise handling of a wide variety of produce
• Segregated High Risk Area
• Process innovation to improve shelf life and organoleptic product quality
• Roof drainage system, which captures rain water and channels into wildlife ponds
• Office air-conditioning system which uses heat pumps to reclaim heat
• 100 seat canteen, with panoramic views of the South Downs
• Bespoke Innovation Kitchen

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