Propane Gas & Liquid Propane Gas | Propane Gas vs LPG Gas
Propane gas is a flammable hydrocarbon gas that is converted into liquid propane gas through pressurisation and commonly used for fuel in heating, cooking, hot water and vehicles.
The propane formula is C3H8 meaning a propane molecule has 3 carbon and 8 hydrogen atoms.
Propane gas is a co-product of natural gas processing and a derivative of crude oil refining.
Is Liquid Petroleum Gas the Same as Propane? Propane Gas vs LPG Gas
In Australia, liquid petroleum gas (LPG) is the same as propane.
Propane is liquid petroleum gas (LPG) but not all LPG is propane.
So, regarding propane gas vs LPG gas, is LP gas same as propane the answer is “it depends”.
Liquid petroleum gas also includes butane (n-butane) and isobutane (i-butane), as well as mixtures of the three LPG gases.
These gases are also referred to as natural gas liquids – NGL, as they are stripped from natural gas during processing.
What is Liquid Propane? Liquid Propane Gas
Propane is stored under pressure as liquid propane (liquid propane gas) in a gas bottle or tank. When the pressure is released, the liquid propane turns into propane gas.
Liquid propane turns into propane gas at -42 °C or -44 °F, which is the boiling point for liquid propane. Conversely, propane gas turns into liquid propane when it drops below -42 °C or -44 °F.
LPG – Propane Gas: What is Propane?
LPG – propane gas is one of the gases that fits the definition of LPG – Liquefied Petroleum Gas.
Propane gas is the same as LPG gas in Australia and the USA.
LPG – propane is stored as a liquid in a propane gas bottle or larger propane tank, compressed into liquid at relatively low pressures.
The common uses for propane gas is as fuel gas for home cooking, heating, hot water and vehicles.
Propane gas can also be used for refrigerants, aerosol propellants and petrochemical feedstock.
Propane gas comes from natural gas processing and crude oil refining.
Propane Physical Properties
Propane Properties Chart
Propane Properties |
|
| Properties | Propane |
| Chemical Formula | C3H8 |
| Energy Content: MJ/m3 | 95.8 |
| Energy Content: MJ/kg | 49.58 |
| Energy Content: MJ/L | 25.3 |
| Boiling Temp: Cº | -42 |
| Pressure @ 21ºC: kPa | 858.7 |
| Flame Temp: Cº | 1967 |
| Expansion: m3/L | 0.270 |
| Gas Volume: m3/kg | 0.540 |
| Relative Density: H2O | 0.51 |
| Relative Density: air | 1.53 |
| kg per L | 0.51 |
| L per kg | 1.96 |
| Specific Gravity @ 25ºC | 1.55 |
| Density @ 15ºC: kg/m3 | 1.899 |
Note: Some numbers have been rounded.
Where Does Liquid Propane Gas Come From?
Liquid propane gas comes from natural gas wells and oil wells.
Liquid propane gas is a fossil fuel that does not occur in isolation. Propane gas is found naturally in combination with other hydrocarbons.
Liquid propane gas is a co-product of natural gas processing and crude oil refining.
It is isolated, liquefied through pressurisation into liquid propane gas and stored in pressure vessels for easy storage, shipping and distribution.
How is Propane Gas Made?
Propane gas is made during natural gas processing and oil refining. It is separated from the unprocessed natural gas using refrigeration.
Propane is extracted from heated crude oil using a distillation tower.
It is then pressurised and stored as liquid propane gas in bottles and propane tanks.
How is Propane Made from Natural Gas?
Propane gas isn’t so much made from natural gas as it is separated from natural gas. Propane gas is separated from the raw natural gas stream by ‘stripper plants’ that literally strip the propane from the raw natural gas stream.
It is important to understand that “raw natural gas”, as it leaves the gas well, contains other gases (including propane) and impurities that need to be processed out to obtain the nearly pure methane gas that we refer to as “refined natural gas” or just “natural gas”.
Applications for Propane Gas
The hospitality industry – hotels, restaurants, pubs and clubs – use propane gas for heating, cooking and hot water.- Liquid propane gas is used in forklifts.
- Chicken farmers use propane gas to keep the chicks warm.
- Farm uses include flame weeding, crop drying and irrigation pumps.
- Auto body repair shops use propane gas for the oven to cure painted cars.
- Refrigeration manufacturers use propane gas for a refrigerant gas.
- Many companies use propane gas to fuel boilers for a multitude of purposes. And the list for uses just goes on and on.
Common Uses of LPG – Propane Gas
LPG – propane gas is used as fuel in homes, business, industrial and agricultural, primarily for space heating, water heating and cooking.
Liquid propane gas is also used as fuel for internal combustion engine applications including cars, forklifts, buses, irrigation pumps, and fleet vehicles.
LPG – propane gas uses in everyday home life include home heating, cooking, hot water heaters, gas fireplaces and clothes drying.
Outdoor home uses include patio heaters, pool heaters, backup generators, and as BBQ fuel.
In addition, propane gas is used for propellant, refrigerant gas and petrochemical feedstock applications.
It does get used in leisure time activities including caravans, boats, recreational vehicles, hot air balloons and camping.
LPG – propane gas is also used for fuel for many commercial and agricultural heat applications, including steam boilers, kilns, ovens and forklifts
Crop and produce drying, heating greenhouses, hot water for dairies, irrigation pumps and heating animal enclosures are just some of the agricultural applications for propane gas.
There are also many, many more propane applications, including power generation and the hospitality industry.
Used as a Fuel Gas
LPG – propane gas is used as a fuel because of its portability and high energy density.
In addition, it only requires modest pressure for liquefication keeping vessel weight down.
LPG – Propane Goes by Many Names
In Australia, propane has many names.
It is also called LPG, LPG Gas, LP Gas, BBQ Gas or Autogas.
In the USA it is just called Propane.
In the UK, it is referred to as either propane or LPG.
How Propane Works
Liquid propane gas is stored under pressure, as a liquid, in a gas bottle.
Liquid propane gas turns back into gas vapour when you release some of the pressure in the gas bottle by turning on your appliance through a process called vaporisation.
To boil, the liquid propane gas draws heat from the steel walls of the gas bottle which, in turn, get heat from the ambient air.
Almost all of the uses for propane involve the use of the gas vapour, not the liquefied gas.
Propane Composition & Structure
Propane structure is as a hydrocarbon gas with 3 carbon and 8 hydrogen atoms in a propane molecule.
The chemical formula for propane is C3H8. (Propane molecule structure model shown)
Propane is not made or manufactured, it is found naturally in combination with other hydrocarbons.
It is produced or “made” during natural gas processing and crude oil refining.
Both processes begin by drilling oil wells.
Propane does not occur naturally in isolation.
LPG – Propane Gas Heating Systems for Homes
LPG – propane gas heating systems for home are an energy efficient way to keep warm and cozy.
Gas heating systems works well for large home spaces.
LPG – propane heating systems are synonymous with fast home heating and real warmth.
Propane gas heating system sub-types include radiant, convectors, radiant-convectors, flued radiant, freestanding fireplaces, fireplace inserts, inbuilt fireplace gas heaters and power flued gas heaters for the home.
With a wide range of propane gas heating appliances systems to choose from, there is a model that is just right for your home.
Propane Tank with Propane
A propane tank with propane is typically a steel vessel for storing the gas.
Homes and small businesses typically use either 45kg gas bottles or the larger 90kg or 210kg propane tank with propane.
BBQ propane tanks come in 9kg and 4kg propane gas bottle sizes.
High volume commercial users have the larger propane tank sizes, some as large as 100 tonne capacity.
Propane gas tanks contain liquid and gas, as propane liquefies under relatively low pressure.
A propane tank is considered low pressure versus high pressure cylinders, as used with CNG.
Propane tank sizes and volumes vary, based on application and demand.
A small propane gas bottle is portable, as used in camping.
You Can Bury a Propane Tank
You can bury a propane tank with propane as long as it was made for burying.
A buried liquid propane gas tank needs anti-corrosive coatings and cathode protection.
Underground propane tanks are tanker filled by hose.
The burying of a liquid propane gas tank should be handled by an experienced professional company and minimum and maximum distances from your home or business apply.
The buried propane tank must also be safely away from any ignition source.
LPG – Propane Tank Installation Distance Requirements & Regulations
Residential LPG – propane tank regulations and propane tank distance requirements are important for a safe installation.
The installation distance requirements can vary based on the size of the propane tank.
The typical minimum distance is 10 feet or 3 meters, including ignition sources and building openings in all directions.
Propane Gas Pressure Regulators
A propane gas regulator is used to control the pressure of the propane gas delivered to the appliance, from the propane gas bottles.
Propane gas pressure regulators automatically modulate high pressure gas down to a maximum pre-determined limit.
The pressure within a gas bottle can be 800-900kPa which is regulated down to the 2.75kPa typically required.
Propane gas pressure regulators are usually factory pre-set.
Is Propane Gas Explosive? Can a Propane Tank Explode?
A propane gas tank explosion or blast is actually quite rare.
Gas cylinders can be explosive but not easily or often.
Even trying to create a propane cylinder explosion intentionally is very challenging.
Propane is explosive only under the right circumstances.
The propane can be explosive if it is within the limits of flammability, between 2.15% and 9.6% of the total propane/air mixture.
For the propane to be explosive, it must also collect in a confined space for an explosion to occur.
Odourant is Added for Safety
In its natural state, propane gas is an odourless gas.
The distinctive smell that people associate with propane gas is actually added to it as a safety measure.
Without the addition of an odourant, leaking gas could collect without being detected.
Avoid Direct Contact with Liquid Propane Gas – Cold Burns
Caution should always be used to avoid direct exposure, as liquid propane gas is cold enough to cause severe cold burns on exposed skin.
Specific Gravity of Propane – Density
Unlike water, 1 kilogram of liquid propane gas does NOT equal 1 litre of propane.
Propane density or specific gravity is about half that of water, at 0.51.
1kg of liquid propane gas has a volume of 1.96L.
Conversely, 1L of liquid propane gas weighs 0.51kg.
1lb of propane @ 60ºF has a volume of 0.24 US gallons.
Conversely, 1 US gallon of propane @ 60ºF only weighs 4.23lbs, instead of the 8.34lbs it would weigh if it was water.
Propane Gaseous Expansion
Liquid propane gas expands to 270 times the volume when it goes from liquid to gas.
So, 1L of liquid propane gas equals 270L of gaseous propane.
As there are 1000L in a cubic meter (M3), 1L of liquid propane gas expands to 0.27M3.
1 US gallon of liquid propane gas equals 36.38ft3 of gaseous propane
Energy Content of LPG – Propane
LPG- propane contains approximately 25MJ per litre.
This also converts to 6.9kWh.
More LPG – propane energy content facts:
1 US gallon of propane = 91,502 BTU @ 60ºF
1ft3 propane gas = 2,488 BTU of Gas @ 60ºF
1 US gallon propane = 1.1 therm
1 therm = 100,000 BTU
1 watt = 3.41214 BTU/h
LPG – Propane Combustion Formula
LPG – propane combustion formula in words:
Propane + Oxygen → Carbon Dioxide + Water + Heat
Propane combustion formula expressed with molecular formulas:
(C3H8 + 5 O2 → 3 CO2 + 4 H2O + Heat)
In the presence of sufficient oxygen, propane burns to form water vapour and carbon dioxide, as well as heat.
If not enough oxygen is present for complete combustion, incomplete combustion occurs with water, carbon monoxide, and carbon dioxide being produced.
LPG – Propane Flame Temperature
An LPG – propane flame burns at 1980ºC (3596ºF).
When it is burning properly, the flame is blue.
A yellow or red flame is usually indicative of incomplete combustion.
LPG – Propane Limits of Flammability
LPG – propane lower and upper limits of flammability are the percentages of gas that must be present in an propane/air mixture.
This means that between 2.15% and 9.6% of the total propane/air mixture must be propane in order for it to be combustible.
LPG – Propane Flash Point
The flash point of LPG – propane is -104ºC (-155.2ºF).
This is the minimum temperature at which propane will burn on its own after having been ignited.
Below this temperature, it will stop burning on its own.
However, if a source of continuous ignition is present, it will burn below -104°C.
Dissipation of the Gas
Propane gas is heavier than air and will sink to and collect at the lowest point.
If propane is vented to the outside air, it will quickly dissipate with the slightest movement of air.
Conversely, if propane gas is vented into a sealed structure, with no air movement, the propane gas will collect on the floor and rise vertically as more propane is vented into the structure.
Propane Vapour (Gas) Use vs. Liquid Propane Gas Use
Propane can be supplied in either liquid propane gas or vapour (gas).
The difference is in the extraction from cylinder or vessel in which it is supplied.
Most propane applications use vapour.
Appliances such as water heaters, room heaters and cookers all use vapour.
If these appliances were to have liquid propane gas flow to their burners, the result could possibly be a fire or similar safety hazard.
This is why propane cylinders should always be kept upright, so that only vapour is released.
Eric Hahn has over a decade of experience in the LPG industry and has become a key figure in shaping how LPG is marketed and communicated. As the creator of one of the world’s first LPG blogs, Eric has authored over 200 technical posts, helping educate and inform the industry and consumers.
Eric has served on multiple committees for Gas Energy Australia and the World LPG Association (WLPGA), contributing to important discussions and advancements within the global LPG sector. He has presented at WLPGA Annual Conferences, sharing his expertise as a speaker, panellist, and panel chair.
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Steve Reynolds
Technical Consultant
Steve Reynolds is a leading expert in the LPG industry with over 22 years of experience. As part of the national management team at ELGAS, Steve ensures the safe and efficient storage, handling, and transportation of LPG. He serves as the lead investigator for incidents and collaborates with authorities on industry developments.
Steve is a technical advisor to Standards Australia and Gas Energy Australia (GEA), and an active member of the World LPG Association (WLPGA), contributing to global standards and technical reviews. He holds a BSc. (Hons) in Industrial Chemistry from UNSW and has held senior safety and technical roles at ELGAS, making him a trusted authority in LPG safety and standards.