Gas system is cool and low cost

French process technology specialist Institut Français du Petrole (IFP) has launched a new process for liquefying natural gas, based on combining the effects of mixed refrigerants and plate-fin heat exchangers.

Dubbed 'Liquefin', the process is cheaper to build and to run than competing technologies.

The gas is precooled using a mixed refrigerant instead of propane, which is the current standard refrigerant. With the right composition, says IFP, the refrigerant can be cooled to -50°C to -80°C; this means it can be completely condensed, with no phase separation, which reduces the amount of refrigerant needed. This also reduces the power needed to pump the refrigerant around the plant.

The precooling stage and the plate-fin heat exchangers that liquefy the gas are combined into single units called 'cold-boxes'. The exchangers themselves have a compact design which is more efficient than the spiral-wound exchangers which are commonly used.

They have a high surface area density - around 1000m2/m3 of gas - and can handle up to ten warm and cold streams simultaneously. Moreover, says IFP, the cold-boxes can be designed and built in 18 months, which shortens the engineering, procurement and construction phase of plant-building projects.