Liquified petroleum gas

Liquified petroleum gas - LPG

Liquified Petroleum Gas is the general name given to propane, butane or a mixture of the two that is sold in pressurised canisters.

LPG can be put in cylinders and delivered for home use.

Propane and butane are short chain alkanes with 3 and 4 carbons respectively. They are both gases at normal temperaures. They come out of the top of the distillation tower and are separated before being bottled.

However, they can be pressurised to turn them into a liquid. We then refer to them as Liquified Petroleum Gas.

Once they have been liquified, they can be put into pressurised cylinders and sold for domestic and industrial use. Butane cylinders are used for gas barbecues and camping and caravan heaters. Propane is used as a substitute for natural gas in remote areas. So it can be used for central heating systems, cookers and so on.

The cylinders have to withstand the high pressure of the gas inside. This is why they are made from strong welded steel.

Similarly, the storage tanks on the refinery site have to be strong. They are steel spheres. The shape means that the tension is the same in the steel all round the sphere - i.e. there are no bits that need to be stronger than the rest of it. [This is the shape that a flexible container like a football or balloon takes up when it is pressurised inside.]

Gas	Carbons	BP °C	Formula	Uses
propane	3	- 42	C₃H₈	• central heating • water heating • cookers • patio heaters
butane	4	- 0.5	C₄H₁₀	• barbecues • caravan cookers • camping fires.