University patents CO2/HC blend

AUSTRALIA: An Australian university has filed a patent for a CO2/hydrocarbon refrigerant blend which lowers CO2’s freezing point to -78.5°C.

Curtin University in Western Australia has found that by adding what has been described as “a small amount” of “a light hydrocarbon agent”, CO2’s triple point could be lowered to -78.5°C at atmospheric pressure.

The patent holder sees the CO2 blend’s lower triple point making it a useful addition to the list of currently available refrigerants for specialist industrial applications. These currently include the flammable hydrocarbons ethane, which has a boiling point of -89°C and propylene, which has a boiling point of -47.6°C.

The Cooling Post has yet to receive answers to specific questions from the developers, but it might be assumed that if only “a small amount” of hydrocarbon is being used the refrigerant would be non-flammable.

The developers, themselves, say that the inert nature of CO2 “is seen as an advantage, particularly in offshore processing plants where risk factors are high, citing its use in cascade refrigeration for producing liquefied natural gas”.

The petrochemical industry is known to have a particular problem in finding a safe replacement for R22, a refrigerant often used in fully-flooded refrigeration systems for the process of liquifying natural gas.