Ammonia Installation Tour reveals the not-so-obvious refrigeration system choice
Industrial refrigeration end-users, engineering consultants and contractors had the opportunity to examine a state of the art low charge ammonia cooling installation at Brake Brothers facilities in Newhouse, Scotland.
Star Technical Solutions consultants took industry stakeholders on a technical tour to examine an innovative ammonia refrigeration plant recently installed at one of Brakes Brother’s largest distribution centres. The visit complemented the International Institute of Refrigeration’s Gustav Lorentzen Conference programme, with a practical, hands-on event.
Brakes Group is a leading food wholesaler in the UK and the food supplier of choice for thousands of businesses in the catering industry in the UK, Ireland, France and Sweden. Over the past four years, Brakes have expanded their business operations with the development of three new, strategically located distribution centres across the UK. With a clear commitment to sustainable growth, the company followed a key design strategy to invest in refrigeration systems that combine maximum safety with high efficiency.
David Blackhurst, director of Star Technical Solutions, said, “Brakes had a very strong vision to go down the route of ammonia refrigeration. They already had ample experience with the use of ammonia and were well aware of its high efficiency properties and health and safety requirements. Based on our feasibility study, a range of options that took into account capital costs, operating costs and total cost of ownership, were presented. The final choice was not the so obvious one”.
Star Technical Solutions led visitors through an inspection of the refrigeration and associated safety systems, followed by a review of Brakes’ design strategy and decision making process that led to the development of a low charge ammonia refrigeration plant. David Blackhurst also demonstrated the positive impact the system of choice had on site safety, comparing the results to more traditional ammonia refrigeration systems.
The facility combined a cold and a chill store with a required cooling load of 395kW and 664kW respectively. Consultants at STS offered three viable options using evaporative condensers. The first two alternatives had the lowest operating costs and specified a Central 2-Stage Pumped System with either direct ammonia to cold and chill or direct R717 to Cold & Chilled Glycol from Intercooler. The third option was a modular pumpless overfeed system with direct R717 to Cold Store & Chilled Glycol, which offered the lowest capital cost. While NPV costs on a 10 year basis were similar, option one delivered the lowest cost of ownership in a 20 year NPV basis.
Moving from evaporative to air-cooled condensers was shown to increase energy use by 5% to 10%, but saved overall as there are no water procurement, treatment or disposal costs.
Revealing a trend to suppress marginal value and driven by the desire to achieve maximum safety, Brakes system of choice for both the cold and chill stores was based on a Pumpless Overfeed System with air cooled condensers and economised (close flash) systems operating with screw compressor. The safety benefits included a 90% reduction in total ammonia charge, from circa 10,000kg to just 840kg, a complete elimination of ammonia valve stations in the roof void – compared to a minimum of eleven for option one, and the consequent removal of hundreds of potential leak routes, in the roof void, to zero.
Blackhurst said, “Ammonia is an excellent refrigerant with a wide operating range, excellent thermodynamic properties and low cost. However, it also toxic and flammable at certain concentrations and this has had an impact in its public perception. The negative attributes are, in some measure, overcome by new technological advancements and low charge ammonia refrigeration is a great example of this.”
“Working with the appropriate safety regulations, such as the Dangerous Substances & Explosive Atmosphere Regulations (DSEAR) 2002, the Management of Health & Safety at Work Regulations 1999 and
Control of Substances Hazardous to Health (COSHH) Regulations, provides the framework and procedures for the safe use of ammonia refrigeration systems.”
The full CPD certified presentation of “Brakes Group Case and Ammonia Safety with Low Charge Refrigeration Systems” is available at www.star-ts.co.uk
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