Halons, which were widely used in fire extinguishers and explosion suppression systems, have an extremely high potential for ozone depletion - they are ten times more potent than chlorofluorocarbons (CFCs) - and they also act as a global warming agent - three and a half thousand times as potent as carbon dioxide (CO2). The use of halons is steadily reducing across the globe in response to the Montreal Protocol, but there are now large stockpiles of halon that need to be disposed of.
Destruction of halons can be achieved in many different ways, including with plasma arc technology like that used at Australia's National Halon Bank. Although these technologies are effective, the destruction of halons is expensive and energy intensive.
What if, instead of being destroyed, halon could be converted into useful products? What if, instead of breaking all the strong chemical bonds in halon, the useful bonds could be kept, making it a much more energy efficient process and producing something useful into the bargain?
This is exactly what researchers from the University of Newcastle are investigating with support from the Australian Department of Sustainability, Environment, Water, Population and Communities and the United States Environment Protection Authority. Professors Eric Kennedy and Bogdan Dlugogorski of the University of Newcastle have been developing a process, which converts halons into vinylidene difluoride (VDF), one of the building blocks of various types of plastics. These plastics are extremely resistant to heat, electricity, flames, ultraviolet (UV) light and chemicals which makes them useful as electrical insulation in computers, aircraft wiring, as seals on bottles containing dangerous chemicals and to use in the production of UV light resistant windows.
There are four main units in the process being researched at the University of Newcastle. Basically though, halon goes in one end and VDF comes out at the other end!
Schematic of the four process units.
A machine that can convert up to 3-tonnes of halon per day is currently under construction in Newcastle to test this process at a commercial scale. In the future, further research will be undertaken to test this process on other types of wastes, including other environmentally unfriendly ozone depleting substances (ODS) and synthetic greenhouse gases (SGGs).
Synthetic greenhouse gases contribute to global warming. Compounds such as hydrofluorocarbons (HFCs) and perfluorocarbons (PFCs) can have high global warming potentials (GWP), several thousands of times that of CO2 and long atmospheric lifetimes. In their current work, the researchers are examining the possibility of adapting their halon and CFC process to also treat PFCs and HFCs. Their initial experimental work looks promising, though more work needs to be undertaken to develop this new application of their halon treatment technology. This innovative Australian research also has promising implications internationally.