Liquefied petroleum gas or liquid petroleum gas (LPG or LP gas), also referred to as simply propane or butane, are flammable mixtures of hydrocarbon gases used as fuel in heating appliances, cooking equipment, and vehicles.
LPG is prepared by refining petroleum or “wet” natural gas, and is almost entirely derived from fossil fuel sources, being manufactured during the refining of petroleum (crude oil), or extracted from petroleum or natural gas streams as they emerge from the ground. It was first produced in 1910 by Dr. Walter Snelling, and the first commercial products appeared in 1912. It currently provides about 3% of all energy consumed, and burns in a relatively clean manner, with no soot and very few sulfur emissions. As it is a gas, it does not pose ground or water pollution hazards, but it can cause air pollution.
LPG has a typical and specific calorific value of 46.1 MJ/kg compared with 42.5 MJ/kg for fuel oil and 43.5 MJ/kg for premium grade petrol. However, its energy density per volume unit of 26 MJ/L is lower than either that of petrol or fuel oil, as its relative density is lower (about 0.5–0.58 kg/L, compared to 0.71–0.77 kg/L for gasoline).
Since, its boiling point is below room temperature, LPG will evaporate quickly at normal temperature and pressure and is usually supplied in pressurized steel vessels. They are typically filled to 80–85% of their capacity to allow for thermal expansion of the contained liquid.
LPG is heavier than air, unlike natural gas, and thus will flow along the floors and tend to settle in lower spots, such as basements. This may result in two possible hazardous threat. The first is a possible explosion if the mixture of LPG and air is within the explosive limits and there is an ignition source. The second is suffocation due to LPG displacing natural air, thereby, causing a decrease in oxygen concentration.
Commercially available LPG is currently derived from fossil fuels. Burning LPG releases carbon dioxide, a greenhouse gas. The reaction also produces some carbon monoxide. LPG however, releases less CO2 per unit of energy than coal or oil.
Being a mix of propane and butane, LPG emits less carbon per joule than butane but more carbon per joule than propane. LPG burns more cleanly than than hydrocarbons which are of higher molecular weight, because it releases less particulate.
If a tank is subjected to a fire of sufficient duration and intensity, it can undergo a boiling liquid expanding vapor explosion (BLEVE). This is typically a concern for large refineries and petrochemical plants that maintain very large containers. In general, tanks are designed that the product will vent faster before the pressure can build up to dangerous levels.
LPG is instrumental in providing off-the-grid refrigeration, usually by means of a gas absorption refrigerator. Such substitution is widely prohibited or discouraged in motor vehicle air conditioning systems, on the grounds that using flammable hydrocarbons in systems originally designed to carry non-flammable refrigerant presents a significant risk of fire or explosion.
19.5 kg of gas in cylinders
LPG is used for cooking in many countries for economic reasons, for convenience or because LPG can be used as a power source for combined heat and power technologies (CHP). CHP is the process of generating both electrical power and useful heat from a single fuel source. This technology has allowed LPG, to be used not just as fuel for heating and cooking, but also for decentralized generation of electricity.
When LPG is used to fuel internal combustion engines, it is often referred to as auto gas or auto propane. Two recent studies have examined LPG-fuel-oil fuel mixes and found that smoke emissions and fuel consumption are reduced, but hydrocarbon emissions are increased. Its advantage is that it is non-toxic, non-corrosive and free of tetraethyl lead or any additives, and has a high octane rating It burns more cleanly than petrol or fuel-oil and is especially free of the particulates present in the latter.
LPG is instrumental in providing off-the-grid refrigeration, usually by means of a gas absorption refrigerator.
Blended of pure, dry propane (refrigerant designator R-290) and isobutane (R-600a) the blend “R-290a” has negligible ozone depletion potential and very low global warming potential. It can serve as a functional replacement for R-12, R-22, R-134a and other chlorofluorocarbon or hydro fluorocarbon refrigerants in conventional stationary refrigeration and air conditioning systems.