Difference Between LPG & Natural Gas

LPG (propane) and Natural Gas (methane) are both used in essentially the same way but they are also different in many ways.

In Australia, we rely on both types of gas for our energy needs.  

LPG and Natural Gas are widely available and used for thousands of applications in homes and business. 

What are the Key Differences Between LPG vs Natural Gas?

Natural gas (methane) vs LPG (propane)

In summary:

• LPG (propane) and natural gas (methane) have different chemical formulas: Methane is CH4Propane is C3H8.

• LPG has a higher calorific value - energy content - than natural gas, with 93.2MJ/m3 vs 38.7MJ/m3.

For proper combustion, LPG requires an air to gas ratio of approximately 25:1 whilst natural gas requires a 10:1 ratio.

• LPG (propane) is more dense than air, at a relative density of 1.5219:1 vs natural gas (methane) at 0.5537:1, which is lighter than air.

• LPG can be compressed into a liquid and stored or transported in a cylinder or larger vessel.

• Natural gas and LPG appliances operate at different pressures.

LPG can be easily processed into Simulated Natural Gas – SNG – and used as a substitute for natural gas. The same is not true in reverse.

Please read more for all of the details about the differences…

Properties: LPG (Propane) vs Natural Gas (Methane)

Properties: LPG (Propane) vs Natural Gas (Methane)
 
Gas Properties
LPG
(Propane)
Natural Gas
(Methane)
Chemical Formula
C3H8
CH4
Energy Content: MJ/m3
93.2
38.7
Energy Content: Btu/ft3
2572
1011
Energy Content: MJ/kg
49.58
52.5
Boiling Temp: Cº
-42
-161.5
Flame Temp: Cº
1967
1950
Flame Temp: Fº
3573
3542
Gas Volume: m3/kg
0.540
1.499
Specific Gravity
1.5219
0.5537
Density @15ºC: kg/m3
1.899
0.668
  Note: Some numbers have been rounded.
 

Calorific Value of LPG vs Natural Gas - Energy Content

There are also two main differences in the way that LPG (Propane) and natural gas (Methane) are burnt. 
The first difference is in the energy content. 
LPG has a higher energy content than natural gas, with 93.2MJ/m3 vs 38.7MJ/m3.
With this higher calorific value, less LPG is required to produce the same amount of heat.

LPG Needs More Oxygen

The second difference is in the oxygen to gas ratio required for proper combustion. 
LPG requires an oxygen to gas ratio of approximately 25 to 1.  
Natural gas requires a ratio of around 10 to 1.  
To achieve this difference, LPG is typically provided in a smaller quantity but at a higher pressure, drawing more oxygen with it into the combustion process.

LPG Density is Greater than Natural Gas

LPG is more dense (has a higher specific gravity) than natural gas.
Natural gas (methane) is less dense than air, at a relative density of 0.5537 to 1.
LPG (propane) is more dense than air, at a relative density of 1.5219 to 1.
So, LPG settles whilst natural gas rises.

LPG (Liquefied Petroleum Gas)

The term LPG actually encompasses more than one type of gas. 
There are a number of hydrocarbon gases that fall into the category of LPG.  
Their common characteristic is that they can be compressed into liquid at relatively low pressures. 
The two most common are Propane and Butane.

What are Natural Gas Liquids – NGLs?

Natural Gas Liquids – NGLs – are heavier gaseous hydrocarbons that are included in the raw natural gas stream from the wellhead.

NGLs include propane, butane, isobutane, ethane, ethene, propene, isobutene, butadiene, pentane, and pentene and pentanes plus.

Pentanes Plus is a mixture of liquid hydrocarbons, mostly pentanes and heavier. Natural gasoline is the largest component of pentanes plus.

Raw natural gas also contains impurities including water vapour, hydrogen sulphide (H2S), carbon dioxide, helium, nitrogen, and other compounds that must be removed.

Propane, butane and isobutane are the three gases that are typically sold as LPG – Liquefied Petroleum Gas.

LPG (Propane)

propane molecule C3H8

Propane is the gas that is supplied to virtually all homes and most businesses that purchase LPG in Australia. 
LPG is supplied in 45kg gas bottles that are either exchanged or refilled on site by LPG tankers. 
LPG goes by a number of names in Australia including LPG, LPG gas, bottled gas, Propane, BBQ gas, camping gas and LP gas.  It’s all the same gas. 
The chemical formula for Propane is C3H8.  

LPG (Butane)

Butane molecule C4H10

Butane is supplied to certain businesses that specify Butane, as opposed to Propane.  

Butane has some specific applications where it has advantages over Propane.

These include greenhouse applications and use as a propellant in aerosols.   

The chemical formula for Butane is C4H10.

Autogas (Propane/Butane mix)

Autogas that is sold at petrol stations can be either just Propane or a Propane/Butane mix. 
Not only is running an LPG car economical, but Autogas is also cleaner burning fuel than petrol, so engine life is actually extended and greenhouse gas emissions reduced.

Natural Gas (Methane)

Natural gas is primarily Methane. 

Methane molecule CH4

When it is extracted from the ground it may also contain Ethane, Propane, Butane, and Pentane. 
Most of these are usually stripped out for other specific applications before it is passed along through the pipelines.  
Impurities are also removed, including water and sulphur.  
The chemical formula for Methane is CH4.

Simulated Natural Gas

Simulated Natural Gas – SNG – is produced by mixing vaporised LPG with compressed air.

SNG can be used in place of natural gas, as it has virtually identical combustion characteristics.

It can be used alone or mixed with regular natural gas.

No changes are required in burners, regulators or gas jets.

Simulated natural gas has a number of names.

In addition to SNG, it is also called propane-air and LPG-air.

Pictured below is a simulated natural gas installation:

Simulated Natural Gas System
Images courtesy of TransTech
 

Piped Gas

Natural gas or “mains gas” is the gas supplied to homes and businesses by gas pipelines or “gas mains” (reticulation systems).  
This is how most Australians receive their gas.

CNG (Compressed Natural Gas)

Methane gas can be stored at high pressure, typically over 200 bars, but it is not very economical for long distance transport. 
CNG does have some specific applications where the product is used in close proximity to where it is compressed. 
City buses are a good example of a successful CNG application.

LNG (Liquefied Natural Gas)

LNG reduces volume by 600 times

Methane gas is processed into LNG by cooling it to −161°C, at which point it becomes a liquid.

This reduces the volume of the natural gas by a factor of more than 600 times as it goes from its gaseous state to liquid.  

That's like going from a beach ball to a ping pong ball. 

This reduced volume facilitates economical transport by sea or road.

Common LNG uses include industrial applications and long haul trucking.

The technology involved with LNG is generally not cost effective for small volume users, such as homes and small businesses.  

For more information, please visit the Elgas LNG web site.

What is LPG?

LPG is the acronym for Liquefied Petroleum Gas 

LPG is used for heating our homes & hot water, cooking our food, powering our BBQs & fuel our cars.

It also powers many business and agricultural processes.

Learn more about this amazing transportable gas that comes in a bottle...

What is LPG? LPG in gas bottles.

How Does LPG Work?

LPG is stored under pressure, as a liquid, in a gas bottle.  

It turns back into gas vapour when you release some of the pressure in the gas bottle by turning on your appliance.

Almost all of the uses for LPG involve the use of the gas vapour, not the liquefied gas. 

What is LPG made of: LPG Composition

The gases that fall under the “LPG” label, including Propane, Butane and Isobutane, as well as mixtures of these gases. 
The two most common are Propane and Butane.

Where does LPG come from?

LPG is not made or manufactured, it is found naturally in combination with other hydrocarbons.

LPG is produced during natural gas processing and petroleum refining. 

Once refined, LPG is stored as a liquid under pressure in gas bottles or tanks.

LPG processing involves the separation and collection of the gas from its petroleum base.

About 60% is produced from the natural gas stream that comes out of the wellhead.

The other 40% is produced during the crude oil refining process.

LPG is isolated from the hydrocarbon mixtures by its separation from natural gas or by the refining of crude oil.

Natural gas liquids (NGL) range from 1% to 10% of the natural gas flow.

Similarly, LPG produced from crude oil refining constitutes between 1% and 4% of the crude oil processed.

Both processes begin by drilling oil wells.

Following its refinement, LPG is stored and distributed as a liquid under pressure until used, at which point it is utilised as either a liquid or a gas (vapour).

Refined from Oil & Natural Gas

LPG processing involves separation and collection of the gas from its petroleum base. 
LPG is isolated from the petrochemical mixtures by separation from natural gas or by the refining of crude oil.
Both processes begin by drilling oil wells. 
The gas/oil mixture is piped out of the well and into a gas trap, which separates the stream into crude oil and "wet" gas, which contains LPG and natural gas.
The heavier crude oil sinks to the bottom of the trap and is then pumped into an oil storage tank for refining. 
Crude oil undergoes a variety of refining processes, including catalytic cracking, crude distillation, and others.  
One of the refined products is LPG.
The "wet" gas, off the top of the gas trap, is processed to separate the gasoline (petrol) from the natural gas and LPG. 
The natural gas, which is mostly methane, is piped to towns and cities for distribution by gas utility companies. 
The petrol is shipped to service stations.
The LPG also enters the distribution network, where it eventually finds its way to end users, including Home LPG and Commercial LPG users all around Australia and the world.
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The information in this article is derived from various sources and is believed to be correct at the time of publication. However, the information may not be error free and may not be applicable in all circumstances.

 

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