Liquefied petroleum gas
Liquefied petroleum gas (also called LPG,
GPL, LP Gas, or
autogas) is a mixture of
used as a
in heating appliances and vehicles, and increasingly replacing
chlorofluorocarbons as an aerosol propellant and a
refrigerant to reduce damage to the
Varieties of LPG bought and sold include mixes that are
propane, mixes that are primarily
butane, and the more common, mixes including both
propane (60%) and
butane (40%), depending on the season—in winter more
propane, in summer more butane.
butylenes are usually also present in small concentration. A
ethanethiol, is added so that leaks can be detected easily.
The international standard is
LPG is usually derived from
fossil fuel sources, being manufactured during the refining
crude oil, or extracted from oil or
gas streams as they emerge from the ground.
At normal temperatures and pressures, LPG will evaporate.
Because of this, LPG is supplied in pressurised
bottles. In order to allow for
thermal expansion of the contained liquid, these bottles are
not filled completely; typically, they are filled to between 80%
and 85% 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. The pressure at
which LPG becomes liquid, called its
vapour pressure, likewise varies depending on composition
and temperature; for example, it is approximately 220
bar) for pure butane at 20 °C (68 °F), and approximately 2.2
megapascals (22 bar) for pure propane at 55 °C (131 °F). LPG
is heavier than
air, and thus will flow along floors and tend to settle in
low spots, such as basements. This can cause ignition or
suffocation hazards if not dealt with.
LPG is the lowest
carbon emitting hydrocarbon fuel available in rural areas,
emitting 19 percent less CO2
kWh than oil, 30 percent less than coal and more than 50
percent less than coal- generated electricity distributed via
LPG burns cleanly with no soot and very few sulfur emissions,
posing no ground or water pollution hazards.
Large amounts of LPG can be stored in bulk tanks and can be
buried underground if required. Alternatively, gas cylinders can
LPG has a typical specific
calorific value of 46.1MJ/kg compared to 42.5MJ/kg for
diesel and 43.5MJ/kg for premium grade petrol (gasoline).
However, its energy density per unit volume is lower than
either petrol or diesel.
Production LPG is synthesised by refining petroleum or
'wet'natural gas it was first produced in 1910 by Dr. Walter
Snelling, and the first commercial products appeared in 1912. It
currently provides about 3% of the energy consumed.
LPG as cooking fuel
According to the 2001 Census of
17.5% of Indian households or 33.6 million Indian households
used LPG as cooking fuel in 2001.
76.64% of such households were from urban India making up 48% of
urban Indian households as compared to a usage of 5.7% only in
Indian households. LPG is subsidised by the government. Increase
in LPG prices has been a politically sensitive matter in India
as it potentially affects the
middle class voting pattern.
LPG was once a popular cooking fuel in
Hong Kong; however, the continued expansion of
town gas to buildings has reduced LPG usage to less than 24%
of residential units.
LPG is the most common cooking fuel in
Brazilian urban areas, being used in virtually all
households. Poor families receive a government grant ("Vale Gás")
used exclusively for the acquisition of LPG.