Chiller chemistry

While the 1997 Kyoto Protocol on climate change has still to be ratified in many parts of the world, there is no doubt that it has already had far-reaching consequences on many industrial activities.

The refrigeration and air conditioning sectors, for example, are now governed by a raft of local and international legislation aimed at controlling the production and use of fluorochemicals - now generally acknowledged as environmentally damaging ozone depleters and greenhouse gases.

The earlier Montreal Protocol led to a phasing out of CFCs as refrigerants, but their HCFC alternatives are now also strictly controlled through production and import quotas.

The European Union has the world's most advanced HCFC phase-out schedule and, as part of the first phase of the ECCP (European Climate Change Programme) adopted last August, is now looking to introduce further restrictions under the Kyoto Protocol on the so-called F-gases, or fluorinated greenhouse gases such as HFCs.

However, according to Mike Dennis, BOC Special Products director, new legislation is just one of the main issues affecting the refrigeration market.

As he explains, 'refrigeration accounts for 14% of the UK's electricity bill and so operators also have to look to the energy efficiency of their systems and consider the total cost of running the plant in economic and environmental terms'.

Since the opening in 1993 of its special gases facility at Immingham, Lincolnshire, BOC has continued to expand its refrigerant services and last year trebled its filling capacity. The refrigerants business is 20% of BOC Special Products, which handles around a quarter of a million cylinders each year at the ISO 14001 accredited 90-acre site.

But apart from filling and shipping cylinders and drums of refrigerants, Immingham is also home to the service arm of BOC Refrigerants, which last year entered into a global alliance with the US refrigeration specialist Hudson Technologies.

Aimed at industries such as chemical and petrochemical, pharmaceuticals, food and drink, the services offered range from system evaluation and rectification, to ongoing process monitoring and, the latest development, high-speed on-site recovery of refrigerant.

Typical problems that can be picked up by a system evaluation include contamination from excess oil, non-condensables, moisture, rust and chemicals - all of which can build up to reduce the thermodynamic efficiency of the plant. Rectifying these problems is also part of the BOC service, purifying the refrigerant, separating out the oil, removing moisture, non-condensables and potentially damaging particulates, and generally restoring the system's refrigerant and oil to their optimum operating levels.

As part of the optional 'ongoing process monitoring service', BOC engineers monitor the plant's performance using Hudson's patented software and feed the data through to the BOC Customer Control Centre. Here, diagnostic reports can be prepared and remedial action recommended as soon as performance shows signs of deteriorating.

BOC's agreement with Hudson Technologies covers the use of the latter's patented refrigerant-cleaning technology in over 20 countries outside of the US. Kevin Baudhuin, BOC's global director for special projects, said at the announcement of the alliance last year: 'We feel Hudson's refrigerants recovery and reclaim technology is superior to any other currently available. Its main advantages are speed of operation and that it can operate without the plant having to be shut down. For our customers that means financial savings.'

Robert Moore, BOC's refrigerants business manager, says BOC approached Hudson after searching for its type of service. 'We only considered one other possible partner, but they couldn't match the speed of Hudson's system, nor the experience built into its systems and software.'

That experience stems from Hudson's 12 years of involvement with refrigerant-side services. Founder, chairman and ceo, Kevin Zugibe, was formerly with Du Pont and brought with him a depth of knowledge in what he describes as chiller chemistry. 'This is one of the hallmarks of our business - to study the relationship of refrigerants, oil and all types of contaminants on the performance of chillers, cooling equipment and refrigeration systems, and provide the best-in-class solutions to refrigerant problems.'

That approach is typified by its on-site, high-speed refrigerant recovery unit, which BOC now has available for use at its larger customers' sites, typically those with a refrigerant loading of 500kg and above. Operated by experienced BOC personnel, the portable unit operates at speeds up to ten times faster than existing recovery systems (up to 2tonne/h), pulling deeper vacuums down to 0.2mbar.

Requiring no heat input, the recovery unit basically works by flash distilling the refrigerant, pulled from the plant system by a compressor with carefully balanced flows. Drawn into the unit's receiving cylinder, the refrigerant flashes off into an upper chamber where it condenses, leaving contaminants such as oil and particulates behind to be subsequently drained from the system and either cleaned up or safely disposed of.

A typical recent application for the unit was on an air separation plant at Margam in South Wales, which supplies oxygen to the Port Talbot steel works. The refrigeration plant consisted of four flooded-shell type evaporators using R22 to cool nitrogen to -64 degrees C. BOC's refrigeration services manager, Colin McNicholl, says that after system evaluation the plant was found to be running warm by some 15 degrees C.

Moreover, software analysis of the system using Hudson's thermodynamic models showed that although the design energy consumption was 1.8kW/tonne of refrigeration working capacity, the actual operating figure was 4.6kW/tonne. There was also evidence of fouling and a significant inventory shortfall.

Over a four-day visit to the site, McNicholl and his team used the portable recovery unit to clean up the R22, removing in the process some 250 litres of oil. They also cleaned up the evaporators and, by being able to pull a deeper vacuum on the system, enabled additional mechanical and instrument refurbishment work to be done.

'The end result,' says McNicholl, 'was a step change in performance. The system is now running 11 degrees C cooler and much closer to its design specifications.'