Developments in de-icing

posted on 27th June 2018

The on-airport de-icing business is changing, as both sounds economic and environmental pressures have forced those involved to look for cheaper and greener ways of ensuring that aircraft can continue to fly in harsh winter conditions

Modern airports are often able to recycle de-icing fluid more efficiently than older ones. That’s fortunate, because heightened awareness of the environmental and financial implications of de-icing fluid loss has encouraged airport planners to make recycling an integral aspect of airport infrastructure.

Munich Airport, which was opened in 1992, has unsurpassed recycling facilities. The airport has a full ‘closed-loop’ system that recycles Type 1 de-icing fluid on site and allows it to meet 70% of its de-   icing fluid requirements through recycling. The gateway’s operator, Flughafen München, estimates that its recycling saves the gateway 2 million euros (US$2.7 million) a year and reduces carbon emissions by about 15,000 tonnes over the same period.

Hans-Joachim Püschner, managing director of Munich Airport’s Aircraft De-Icing and Towing Services, explains: “Before the 1980s, general de-icing was done on airport stands and waste fluid went down drains. Some went into sewage treatment plants. Only at the old Oslo Airport and a small Swedish airport in Lulea was some recycling performed.

“The new Munich Airport was the first major airport to do it on a large scale. Specialists planned the construction of remote de-icing pads, as well as a recycling plant which collects and recycles up to 60% of spent glycol.”

Munich de-ices aircraft with engines running just before take-off at de-icing pads at the heads of each of its runways. There are three pads for each end of the north and south runways. The proximity of the remote pads to the runways allows aircraft to take off very shortly after being de-iced. This minimises the possibility that the holdover time – the period an aircraft can safely be held after treatment prior to take-off without requiring further de-icing – will be exceeded.

After the de-icing fluid is sprayed, the waste liquid is channelled from the pads into large, subterranean tanks. The fluid-water mixture is then taken to the airport’s recycling facility and treated to produce newly useable de-icing fluid.

“For most of the older airports, it’s hard to create such a recycling solution. They rarely have a place to put the special de-icing pads that are so essential to the process. There’s also the need to build tanks and figure out how to truck the fluid-water mixture to a recycling plant,” Püschner notes.

“As a result they mainly do their de-icing on the apron, where recycling is impractical. It would mean huge investment in infrastructure and so much water would have to be collected that recycling costs would be too high,” he observes.

Munich Airport carries out a comparatively small amount of de-icing on the apron. This could be the case for under-wing de-icing, or de-icing aircraft outside the usual season. For example, propeller aircraft without propeller brakes are de-iced on the apron in the aircraft’s parked position.

Munich employs a fleet of 27 de-icing vehicles, which it calls ‘polar bears’. There are three types: Vestergaard’s Elephant Beta, the Elephant Beta NG and the Elephant Beta-15, which has a reach sufficient to treat aircraft giants such as the A380. The ‘polar bears’ hold about 6,000 litres of Type I and 2,000 litres of Type IV de-icing fluid.

The vehicles spray two different types of glycol-based de-icing fluid onto the aircraft. The thinner Type I de-icing fluid is combined with water in a 55:45 mixture. It is heated and applied to the aircraft at a temperature of 85°C. The thickener in Type IV de-icing fluid gives it a higher viscosity, and it is sprayed cold and unmixed. The two fluids are dyed different colours to help distinguish them more easily.

Efficient recycling

Norway’s Oslo Airport is another example of a modern airport that made de-icing and recycling infrastructure integral to its original design. The airport opened in 1998 with dedicated de-icing pads. “We are obliged to recycle because of environmental restrictions on the airport. It is built on a large ground water basin which is a water reserve for the area and cannot be polluted,” says airport press spokesperson Lasse Vangstein.

At Oslo Airport, the fluid run-off is routed into a storage basin and divided into A, B and C streams, corresponding to ‘very low glycol’, ‘low glycol’ and ‘moderate glycol’ categorisations. The low glycol solution goes into ground water or the waste water system. The slightly more toxic B stream goes into sewage, or bio-treatment plants. Finally, if there is more than 5% glycol, Oslo Airport will recycle it.

“This system ensures that a high amount of spent de-icing fluid is collected in a relatively small volume. On average, 60% of spent glycol is collected for recycling, with an average glycol concentration of 10-12%,” Vangstein notes.

Switzerland-headquartered chemicals manufacturer Clariant has managed the recycling system for Oslo Airport since the winter of 2011-12. In an average winter, 7,000 metric tonnes of used fluid will be treated and concentrated to about 1,100 metric tonnes of 60-65% propylene glycol in an 800 square metre factory at the Norwegian capital’s gateway.

“After we’ve concentrated it on-site into the 65% glycol-dirty water mix, we ship it to our main manufacturing plant in Gendorf, in Germany, and concentrate it right up to pure glycol,” informs Nigel Westlake, Clariant’s head of aviation sales. “There are technical challenges because of trace contaminants in the fluid. We analyse the contaminants to decide if it is pure enough to be used as de-icing fluid again. Alternatively, we use it for other Clariant products.”

Apart from ever-increasing environmental pressures, Westlake considers that the biggest trend in the on-airport de-icing industry concerns the growing importance of logistics. This, he says, goes back to the harsh winter of 2010, when arctic conditions covered most of Europe and North America’s airports in a blanket of snow and ice and there was unusually high demand for de-icing fluid. “In Europe, we had a shortage of supply of glycol to the market and there were numerous airport closures because of the lack of de-icing fluid,” he points out.

“This experience really concentrated our minds on logistics, so that is something we’ve strengthened every year since 2010-11. We’ve set up new depots and strategic stock locations all over Europe. We now have more than 10 depots in Europe, including three master ones in Central Europe. We’ve also diversified our manufacturing so that we now have one main plant in Germany, others in Sweden and Finland, as well as two in Russia. We are moving production closer to the customers to speed up our supply chains.”

The benefits of Clariant’s improved logistics were evident during the severe 2012-13 European winter. British Airways had to perform a record number of de-icing operations at Heathrow Airport and Clariant had just won the contract to supply fluid. “Heathrow in January was a really tough month, with a lot of extra demand for de-icing fluid. But the superior links we had set up between depots after the winter of 2010 meant we coped well under extreme conditions,” Westlake enthuses.

Clariant has also introduced shipment tracking tools. Customers can check the status of their orders online and track deliveries using GPS. Plus, the Clariant customer portal contains details about paperwork, including drivers’ names and licence numbers. “All these measures are about making supply chains more efficient,” Westlake confirms.

A new challenge for manufacturers, he goes on, has arisen from the introduction of composite wings on aircraft, such as those on the B787 and A380. Compared to their predecessors, carbon composite wings do not transmit as much heat from the fluid to heat up the ice and shift it. “That’s tricky for operators as they might need to use more fluid than in the past,” he says.

Plus, composite wings reduce holdover time. “It’s a similar problem. You can’t get enough heat into the wings from the liquid, so you don’t get enough de-icing protection and holdover times are shortened.” Despite these issues, Westlake says, liquid de-icing will be required for aircraft well into the foreseeable future.

He argues that emerging technologies with the potential to disrupt the market will be held back by various challenges. “Manufacturers are trying to develop electrical heating for aircraft wings. But this is not only technically very difficult because of the power requirements involved, but also aircraft don’t have it fitted, so there would need to be complete retrofits of fleets. So it won’t be feasible for a long time.”

Sustainable fluids

One of Clariant’s major rivals in the global aircraft de-icing sector, Kilfrost, has put a lot of money into research and development in recent years. In 2007, Kilfrost teamed up with DuPont Tate & Lyle BioProducts to develop a sustainable de-icing fluid from corn. Users include All Nippon Airways in Japan, Lambert St Louis Airport in the US and Air New Zealand. “Environmental products have been our major focus in recent years. So far we have only produced Type 1 green products, but a Type IV fluid is on the way,” says chief executive Gary Lydiate.

Kilfrost’s R&D team, Lydiate remarks, could be on the verge of an even bigger breakthrough. But he is only willing to give general details at this stage. “We are testing a radical, game-changing new product. The potential is to produce a fluid that doesn’t just take snow and ice off the wings, but also cleans the wings. If we are happy with the test results and it fits with what the airline industry wants today, we will publicise it within 12 months,” he promises.

Forward-looking airports, such as Munich and Oslo, are also experimenting with new de-icing methods. For instance, Munich Airport is sought out by manufacturers wanting to evaluate new products in the field.

“We’re testing a number of new technologies, including systems using hot air to remove ice and snow,” Püschner says. “For the aircraft, we’re trying out new surfaces that function like lotus leaves, which are self-cleaning and repel water. The water rolls off and takes contaminants with it. For our new vehicles, we are testing a pre-positioning system that helps to maintain the optimum distance from the aircraft for spraying fluid. This reduces the quantity used.”

Oslo Airport, meanwhile, has tested a Canadian-built system for de-icing aircraft that employs infra-red rays rather than chemicals. Radiant Energy’s InfraTek De-icing System has proved successful at New York’s JFK and Newark airports. It uses infra-red panels powered by natural gas. They are fixed into a large hangar, where the infra-red rays melt the ice off the aircraft’s wings and body.

However, in Norway: “We installed a hangar and tried out the system, but operational use was not agreed for Oslo and the installation was removed,” Vangstein says. “It was unfortunate as we were hoping it would reduce glycol use considerably and improve our environmental record.” Nevertheless, he does not rule out using the system in future. “Developments in this technology might make it more effective in our type of climate in the future,” he adds.