What is LPG .

2012-09-07T23:36:00.000-07:00

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Liquefied petroleum gas, also called LPG, GPL, LP Gas, liquid petroleum gas or simply propane, is a flammable mixture of hydrocarbon gases used as a fuel in heating appliances and vehicles. It is increasingly used as an aerosol propellant and a refrigerant, replacing chlorofluorocarbons in an effort to reduce damage to the ozone layer. When specifically used as a vehicle fuel it is often referred to as autogas.
Varieties of LPG bought and sold include mixes that are primarily propane (C₃H₈), primarily butane (C₄H₁₀) and, most commonly, mixes including both propane and butane, depending on the season — in winter more propane, in summer more butane^{[citation needed]}. In the United States, primarily only two grades of LPG are sold, commercial propane and HD-5. These specifications are published by the Gas Processors Association (GPA)^[1] and the American Society of Testing and Materials (ASTM)^[2]. Propane/butane blends are also listed in these specifications. Propylene, butylenes and various other hydrocarbons are usually also present in small concentrations. HD-5 limits the amount of propylene that can be placed in LPG, and is utilized as an autogas specification. A powerful odorant, ethanethiol, is added so that leaks can be detected easily. The international standard is EN 589. In the United States, tetrahydrothiophene (thiophane) or amyl mercaptan are also approved odorants^[3], although neither is currently being utilized.
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 relatively cleanly 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 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 (gasoline).^[4] However, its energy density per volume unit of 26 MJ/L is lower than either that of petrol or fuel oil, as its liquid density is lower (about 0.5—0.58, compared to 0.71—0.77 for gasoline).
As its boiling point is below room temperature, LPG will evaporate quickly at normal temperatures and pressures and is usually supplied in pressurised steel vessels. They are typically filled to between 80% and 85% of their capacity to allow for thermal expansion of the contained liquid. The ratio between the volumes of the vaporized 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 kilopascals (32 psi) for pure butane at 20 °C (68 °F), and approximately 2.2 megapascals (320 psi) for pure propane at 55 °C (131 °F). LPG is heavier than air, unlike natural gas, and thus will flow along floors and tend to settle in low spots, such as basements. There are two main dangers from this. The first is a possible explosion if the mixture of LPG and air is right and if there is an ignition source. The second is suffocation due to LPG displacing air, causing a decrease in oxygen concentration. Fortunately, LPG is not toxic, so there is no danger of poisoning. In addition, odorants are mixed with all LPG so that leaks can be detected more easily.
Large amounts of LPG can be stored in bulk cylinders and can be buried underground.

1 Uses
- 1.1 Rural heating
- 1.2 Motor fuel
- 1.3 Refrigeration
- 1.4 Cooking
2 Security of supply
3 Comparison with natural gas
4 Environmental effects
5 Fire risk and mitigation
6 See also
7 References
8 External links

Uses

Rural heating

Cylinders with LP gas in India

Predominantly in Europe and rural parts of many countries, LPG can provide an alternative to electricity and heating oil (kerosene). LPG is most often used where there is no access to piped natural gas.
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 de-centralised generation of electricity.
LPG can be stored in a variety of ways. LPG, as with other fossil fuels, can be combined with renewable power sources to provide greater reliability while still achieving some reduction in CO₂ emissions.

Motor fuel

LPG filling connector on a car

Main article: Autogas

White bordered green diamond symbol used on LPG-powered vehicles in China

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. 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.^[5]^[6] The studies were split on CO emissions, with one finding significant increases,^[5] and the other finding slight increases at low engine load but a considerable decrease at high engine load.^[6] Its advantage is that it is non-toxic, non-corrosive and free of tetra-ethyl lead or any additives, and has a high octane rating (102-108 RON depending on local specifications). It burns more cleanly than petrol or fuel-oil and is especially free of the particulates from the latter.
LPG has a lower energy density than either petrol or fuel-oil, so the equivalent fuel consumption is higher. Many governments impose less tax on LPG than on petrol or fuel-oil, which helps offset the greater consumption of LPG than of petrol or fuel-oil. However, in many European countries this tax break is often compensated by a much higher annual road tax on cars using LPG than on cars using petrol or fuel-oil. Propane is the third most widely used motor fuel in the world. 2008 estimates are that over 13 million vehicles are fueled by propane gas worldwide. Over 20 million tonnes (over 7 billion US gallons) are used annually as a vehicle fuel.
Not all automobile engines are suitable for use with LPG as a fuel. LPG provides less upper cylinder lubrication than petrol or diesel, as a consequence LPG fueled engines are more prone to wearing valves if not suitably modified. Many modern common rail diesel engines respond well to LPG use as a supplementary fuel. This is where LPG is used as fuel as well as diesel. Systems are now available that integrate with OEM engine management systems.

Refrigeration

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 and can serve as a functional replacement for R-12, R-22, R-134a,and other chlorofluorocarbon or hydrofluorocarbon refrigerants in conventional stationary refrigeration and air conditioning systems.^[7]
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.^[8]^[9]^[10]^[11]^[12]^[13]^[14]^[15]
Vendors and advocates of hydrocarbon refrigerants argue against such bans on the grounds that there have been very few such incidents relative to the number of vehicle air conditioning systems filled with hydrocarbons.^[16]^[17] One particular test was conducted by a professor at the University of New South Wales that unintentionally tested the worst case scenario of a sudden and complete refrigerant loss into the passenger compartment followed by subsequent ignition. He and several others in the car sustained minor burns to their face, ears, and hands, and several observers received lacerations from the burst glass of the front passenger window. No one was seriously injured.^[18]

Cooking

Truck carrying LPG cylinders to residential consumers in Singapore

According to the 2001 Census of India, 17.5% of Indian households or 33.6 million Indian households used LPG as cooking fuel in 2001, which is supplied to their homes by Indian Oil which is known as Indane.^[19] 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 rural 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 urban 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.

Security of supply

Because of the natural gas and the oil-refining industry, Europe is almost self-sufficient in LPG. Europe's security of supply is further safeguarded by:

a wide range of sources, both inside and outside Europe;
a flexible supply chain via water, rail and road with numerous routes and entry points into Europe;

As of early 2008, world reserves of natural gas — from which most LPG is derived — stood at 6,342.411 trillion cubic feet. Added to the LPG derived from cracking crude oil, this amounts to a major energy source that is virtually untapped and has massive potential. Production continues to grow at an average annual rate of 2.2%, virtually assuring that there is no risk of demand outstripping supply for the foreseeable future.^{[citation needed]}

Comparison with natural gas

LPG is composed primarily of propane and butane, while natural gas is composed of the lighter methane and ethane. LPG, vaporised and at atmospheric pressure, has a higher calorific value (94 MJ/m³ equivalent to 26.1kWh/m³) than natural gas (methane) (38 MJ/m³ equivalent to 10.6 kWh/m³), which means that LPG cannot simply be substituted for natural gas. In order to allow the use of the same burner controls and to provide for similar combustion characteristics, LPG can be mixed with air to produce a synthetic natural gas (SNG) that can be easily substituted. LPG/air mixing ratios average 60/40, though this is widely variable based on the gases making up the LPG. The method for determining the mixing ratios is by calculating the Wobbe index of the mix. Gases having the same Wobbe index are held to be interchangeable.
LPG-based SNG is used in emergency backup systems for many public, industrial and military installations, and many utilities use LPG peak shaving plants in times of high demand to make up shortages in natural gas supplied to their distributions systems. LPG-SNG installations are also used during initial gas system introductions, when the distribution infrastructure is in place before gas supplies can be connected. Developing markets in India and China (among others) use LPG-SNG systems to build up customer bases prior to expanding existing natural gas systems.

Environmental effects

Commercially available LPG is currently derived from fossil fuels. Burning LPG releases CO₂, an important greenhouse gas, contributing to global warming. LPG does, however, release less CO₂ per unit of energy than that of coal or oil. It emits 81% of the CO₂ per kWh produced by oil, 70% of that of coal, and less than 50% of that emitted by coal-generated electricity distributed via the grid.^{[citation needed]} Being a mix of propane and butane, LPG emits less carbon per joule than butane but more carbon per joule than propane.
LPG can be considered to burn more cleanly than heavier molecule hydrocarbons, in that it releases very few particulates.

Fire risk and mitigation

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A spherical gas container typically found in refineries

In a refinery or gas plant, LPG must be stored in pressure vessels. These containers are either cylindrical and horizontal or spherical. Typically, these vessels are designed and manufactured according to some code. In the United States, this code is governed by the American Society of Mechanical Engineers (ASME).
LPG containers have pressure relief valves, such that when subjected to exterior heating sources, they will vent LPGs to the atmosphere. If a tank is subjected to a fire of sufficient duration and intensity, it can undergo a boiling liquid expanding vapour 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 than pressure can build to dangerous levels.
One remedy, that is to utilized in industrial settings, is to equip such containers with a measure to provide a fire-resistance rating. Large, spherical LPG containers may have up to a 15 cm steel wall thickness. They are equipped with an approved pressure relief valve. A large fire in the vicinity of the vessel will increases its temperature and pressure, following the basic gas laws. The relief valve on the top is designed to vent off excess pressure in order to prevent the rupture of the container itself. Given a fire of sufficient duration and intensity, the pressure being generated by the boiling and expanding gas can exceed the ability of the valve to vent the excess. If that occurs, an overexposed container may rupture violently, launching pieces at high velocity, while the released products can ignite as well, potentially causing catastrophic damage to anything nearby, including other containers.

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List of CO2 emitted per million Btu of energy from various fuels

References

^ "Liquefied Petroleum Gas Specifications and Test Methods". Gas Processors Association. https://www.gpaglobal.org/publications/view/id/36/. Retrieved 5/18/2012.
^ "ASTM D1835 - 11 Standard Specification for Liquefied Petroleum (LP) Gases". American Society for Testing & Materials. http://www.astm.org/Standards/D1835.htm.
^ 49CFR173.315(b)(1)Note 2
^ Horst Bauer, ed. (1996). Automotive Handbook (4th ed.). Stuttgart: Robert Bosch GmbH. pp. 238–239. ISBN 0-8376-0333-1.
^ ^a ^b Zhang, Chunhua; Bian, Yaozhang; Si, Lizeng; Liao, Junzhi; Odbileg, N (2005). "A study on an electronically controlled liquefied petroleum gas-diesel dual-fuel automobile". Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 219 (2): 207. doi:10.1243/095440705X6470.
^ ^a ^b Qi, D; Bian, Y; Ma, Z; Zhang, C; Liu, S (2007). "Combustion and exhaust emission characteristics of a compression ignition engine using liquefied petroleum gas–fuel-oil blended fuel". Energy Conversion and Management 48 (2): 500. doi:10.1016/j.enconman.2006.06.013.
^ "European Commission on retrofit refrigerants for stationary applications" (PDF). http://ec.europa.eu/environment/ozone/pdf/hcfc_technical_meeting_summary.pdf. Retrieved 30 July 2009.
^ "U.S. EPA hydrocarbon-refrigerants FAQ". United States Environmental Protection Agency. http://www.epa.gov/ozone/snap/refrigerants/hc12alng.html. Retrieved 30 July 2009.
^ Compendium of hydrocarbon-refrigerant policy statements, October 2006^{[dead link]}
^ "MACS bulletin: hydrocarbon refrigerant usage in vehicles" (PDF). http://www.autoacforum.com/MACS/HCwarning.pdf. Retrieved 30 July 2009.
^ "Society of Automotive Engineers hydrocarbon refrigerant bulletin". Sae.org. 27 April 2005. http://www.sae.org/news/releases/05hydrocarbon_warning.htm. Retrieved 30 July 2009.
^ "Shade Tree Mechanic on hydrocarbon refrigerants". Electromechanics.com. 27 April 2005. http://www.shadetreemechanic.com/cc_hydrocarbon_refrigerants.htm. Retrieved 30 July 2009.
^ "Saskatchewan Labor bulletin on hydrocarbon refrigerants in vehicles". Labour.gov.sk.ca. 1 January 1996. http://www.labour.gov.sk.ca/Default.aspx?DN=2fb5ac24-d90e-4408-bf40-559793bd8e96. Retrieved 30 July 2009.
^ VASA on refrigerant legality & advisability^{[dead link]}
^ "Flammable Refrigerant Alert" (PDF). http://www.energy.qld.gov.au/zone_files/petroleum_pdf/safety_alert025.pdf. Retrieved 30 July 2009.
^ "New South Wales (Australia) Parliamentary record, 16 October 1997". Parliament.nsw.gov.au. 16 October 1997. http://www.parliament.nsw.gov.au/prod/parlment/HansArt.nsf/V3Key/LA19971016015. Retrieved 30 July 2009.
^ "New South Wales (Australia) Parliamentary record, 29 June 2000". Parliament.nsw.gov.au. http://www.parliament.nsw.gov.au/prod/parlment/hansart.nsf/V3Key/LC20000629051. Retrieved 30 July 2009.
^ http://web.archive.org/web/20080719142356/http://www.vasa.org.au/pdf/memberlibrary/hydrocarbons/maclaine-cross.pdf VASA news report on hydrocarbon refrigerant demonstrations (from the Internet Archive; retrieved 24 May 2012)
^ "Indian Census". Censusindia.gov.in. http://www.censusindia.gov.in/. Retrieved 30 July 2009.

External links

WLPGA World LP Gas Association
PERC Propane Education & Research Council
NPGA National Propane Gas Association, USA
Propane 101 Explaining propane and LP Gas fundamentals

Liqufied Petrolium Gas Piping