What are liquid gases?

LPG stands for liquefied petroleum gas, and it is a mixture of propane and butane, most often associated with automotive fuels.  It is a liquid fuel because in this form it is stored in tanks or cylinders under appropriate pressure. However, it is primarily used as a gas, that is in a volatile form.

LPG is obtained as a by-product of crude oil refining and from natural gas deposits, usually at the start of a new borehole.

Vehicles are fuelled with a standard mixture of propane and butane in proportions of approximately 50/50, but it is common to see a 60/40 mixture, and in winter it goes up to a 70/30 ratio in favour of propane. This is due to the characteristics of propane as a lighter gas that is less affected by low temperatures than butane, which in a way forces the use of more propane in winter. On the other hand, too high propane content is not recommended in summer, as high temperatures translate into expansion of the lighter gas and increased pressures, which may result, for example, in damage to the gas system. It is worth knowing that LPG at room temperature and normal pressure is a gas. However, it will liquefy at room temperature when the pressure is between 2.2 and 4 atmospheres. It is pumped into the cylinder at a pressure of 6 atm. For this reason, the cylinders in which it is stored and transported are usually filled to approximately 80% of their capacity in order to prevent the liquid, which expands in response to temperature changes, from rupturing the cylinder. Naturally, safety valves are also used to minimise this risk.

LPG is widely used in everyday life, in industry, e.g. automotive industry, tourism or in households. More about the applications of LPG in the next post!