What is LPG or LP Gas?
Liquefied petroleum gas (LPG), is the generic name for propane and butane gas. They are both a mixture of hydrocarbon gases used as a fuel in heating appliances and vehicles, and increasingly replacing chlorofluorocarbons as an aerosol propellant and a refrigerant to reduce damage to the ozone layer. When LPG is used to fuel internal combustion engines, it is often referred to as autogas or auto propane. In some countries, it has been used since the 1940s as a petrol alternative for spark ignition engines.
Why is it called Liquefied Petroleum Gas?
This is because these gases liquefy under moderate pressure and they readily vaporize upon release of pressure. At normal temperatures and pressures, LPG will evaporate. Because of this, LPG is stored in steel tanks. In order to allow for thermal expansion of the liquid gas, these tanks are filled between 80% and 90% of their capacity. The ratio between the volumes of the vaporised gas and the liquefied gas varies depending on composition, pressure and temperature, but is typically around 250:1. LPG is heavier than air, and thus will flow along floors and tend to settle in low spots, such as basements. You should not park your converted car in underground car parks and your car will not be allowed in the Channel Tunnel.
Where does LPG come from?
LPG is manufactured during the refining of crude oil, or extracted from oil or gas streams as they emerge from the ground. LPG is either delivered by sea tanker or piped in from offshore gas fields.
LPG as Autogas?
Autogas is widely used as a "green" fuel as it decreases exhaust emissions. In particular, it reduces CO2 emissions by around 35% compared to petrol. One litre of petrol produces 2.3 kg of CO2 when burnt, whereas the equivalent amount of autogas produces only 1.5 kg of CO2 when burnt. It has an octane rating (MON/RON) that is between 90 and 110 and an energy content (higher heating value—HHV) that is between 25.5 megajoules per liter (for pure propane) and 28.7 megajoules per litre (for pure butane) depending upon the actual fuel composition.
Autogas is the third most popular automotive fuel in the world, with approximately 17 million of 600 million passenger cars powered using the fuel, representing less than 3% of the total market share. Approximately half of all autogas-fueled passenger vehicles are in the five largest markets (in ascending order): Turkey, South Korea, Poland, Italy, and Australia.