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LNG - Liquefied Natural Gas - Methane

LNG, or Liquefied Natural Gas, is simply natural gas in a liquid form.  

It is the same natural gas (Methane) that millions of homeowners and businesses use every day.

LNG, which is predominantly Methane, is an odourless, non-toxic and non-corrosive.

It is liquefied using a cryogenic process.

LNG Energy Content - Energy Density of LNG

The energy content of LNG ranges from 24 MJ/L to 21 MJ/L. The energy density of LNG is roughly 0.41 kg/L to 0.5 kg/L, depending mostly on temperature and pressure. The energy density of LNG is 2.4 times greater than CNG. This makes it economical to transport. The energy content of LNG is comparable to propane.

LNG Physical Properties: What is LNG?  Liquefied Natural Gas?

Liquefied Natural Gas – LNG – physical properties include being flammable methane liquefied at -161°C (-160ºC boiling point) to reduces its volume 600 to 1 (1m³ of LNG = 600m³ of methane gas). LNG is a colourless, naturally odourless cryogenic liquid with a density of 426kg/m³ or 26.5943lb/ft³.

LNG - Liquefied Natural Gas - Physical Properties List:

LNG is liquefied natural gas - methane

♦ LNG is the acronym for Liquefied Natural Gas or Liquid Natural Gas.

♦ LNG – liquefied natural gas – is methane (CH4) that is liquefied by cryogenic chilling below -161°C.

1m³ of LNG = 600m³ of methane gas: as a liquid, the volume of the methane is reduced to 1/600 its gaseous state. 

♦ This makes LNG transportable in cryogenic ships or trucks.

♦ LNG comes from raw natural gas processing.

♦ There are a number of other gases that are separated from the raw natural gas before chilling, including propane, butane (n-butane) and isobutane (i-butane), as well as mixtures of these gases and are also referred to as natural gas liquids – NGL.

♦ LNG gas can be converted into liquid at a relatively low pressure.

♦ LNG converts into a flammable hydrocarbon gas - methane - that is commonly used as fuel.

♦ LNG is frequently used for fuel in heating, cooking, hot water and vehicles, after it has been regasified into methane. 

♦ This the same natural gas that is piped to homes and businesses.

Australia will likely be the world’s largest exporter of LNG by the year 2020.  This will have a huge positive impact on the Australian economy.

♦ LNG is stored, as a liquid, in cryogenic steel vessels with very low storage pressure, at less than 10 kPa.

♦ After regasification, it reverts to and is used as natural gas.

(Pictured above is LNG storage with heat exchangers for regasification)

To get all of the details on LNG, let's look at:

  • LNG - Liquefied Natural Gas Properties

  • Uses of LNG

  • LNG Defined
  • Uses and Applications

  • Volume Reduction

  • Transportability

  • Energy Content

  • Use of "Stranded" Natural Gas

  • Micro LNG Plants

  • LNG and the Environment

  • Production Process

  • Storage

  • Regasification

  • LNG Value Chain

LNG - Liquefied Natural Gas Properties

LNG - Liquefied Natural Gas Properties
LNG - Liquefied Natural Gas Properties
Natural Gas Chemical Formula CH(Methane)
Boiling Point -161°C or -257.8°F
Liquid Density
426kg/m³
or 26.5943lb/ft³
Gas Density
at 25°C or 77ºF
0.656 kg/m³
or 0.04095lb/ft³
Specific Gravity (Air=1) 0.554
Limits of Flammability 5.3% to 14%
Auto Ignition Temperature 595°C or 1103°F

 

Odourant is added, for safety, before the gas is piped to end users.

If spilled, the LNG evaporates quickly and disperses.

• LNG - natural gas chemical formula: CH4

Flammability Limits (in air by volume): 5.3% to 14%

Auto Ignition Temperature: 595°C

Natural Gas Chemical Formula - Chemical Formula for Methane

The natural gas chemical formula is CH4. To be accurate, this natural gas chemical formula is actually the chemical formula for methane, which is the primary constituent of refined natural gas.

Raw natural gas, straight out of the ground, also contains natural gas liquids and various impurities.

What is the Main Constituent of Liquified Natural Gas?

The main constituent of liquefied natural gas is refined methane.

It is specifically NOT the raw natural gas that comes out of the gas well.

Raw natural gas has NGLs and impurities would make liquefaction difficult, if not impossible.

For example, any impurity that freezes above -161°C, like water, would prevent the flow of the liquefied methane.

LNG Density - Specific Gravity of LNG

Liquid Density: 426kg/m3

Gas Density (25°C): 0.656 kg/m3

Specific Gravity (15°C): 0.554

LNG Boiling Point

The boiling point of LNG is -161°C.

This is the same temperature that must be achieved when chilling the methane during the liquefaction process.

Composition of LNG

LNG composition is purified methane.

All of the impurities, including moisture, need to be removed before it can be liquefied by chilling it to −161°C.

Full Form of LNG - Meaning of LNG

LNG is the acronym for Liquefied Natural Gas.

LNG should not be confused with NGL - Natural Gas Liquids - which are totally different.

What is LNG Used For? LNG Uses and Applications

LNG Boilers

Industrial and commercial boilers are one of the most common uses for LNG in Australia. 

The industries include dairy products, manaufacturing, food processing and construction products.

Road Transport with LNG    

LNG as an alternative fuel to diesel for road transportation has been in development in Australia since 2001. 

Over 200 heavy duty vehicles are now in daily operation.

LNG is also a practical and cost effective way to reduce road transport emissions.

Natural gas as a vehicle fuel has a long and established record in Europe, the UK, Canada, and in the USA.

Many countries have natural gas vehicles today. 

It is estimated that there are 4,000 plus LNG vehicles globally.

LNG powered vehicle technology has matured over the last 15 years.

Technology improvements have all contributed to this.

Engine manufacturers, such as Cummins and Caterpillar, have also assisted by providing engines for natural gas.

LNG powered vehicles have range and refuelling times comparable to diesel.

LNG Fuelling Station

LNG Power Generation

LNG is a suitable alternative to diesel for the remote power generation market.

These remote power generating plants provide electricity for towns or mine sites and can vary in size from 1 MW to 50MW.

Replacing the current diesel fuel supply with LNG is a cost effective, safe and clean option. 

Customers either replace existing diesel generators with gas generators or convert existing units to dual fuel.

This typically occurs during expansion or with new projects, or by converting existing sets to dual fuel operation.

Mining and Industrial Uses of LNG

LNG mining truckMining and industrial markets have considerable potential employ LNG into their operations.

LNG is currently used in power generation, boilers, fluid bed dryers, rotary kilns and furnaces.

Large quantities of diesel are consumed by mining vehicles. 

These vehicles are typically used only on a particular site with short repetitive routes. 

This makes them ideal for refuelling at a one site location.

LNG Powering Rail and Ships

Rail is also a potential LNG application.

LNG to replace diesel for locomotives has increased substantially in the past few years and LNG powered locomotives are already in use in other countries.

Ships with short repetitive routes are also a viable LNG use. 

Ferries are a prime example of this application.

LNG has Reduced Volume

LNG is 600 times more dense than natural gasNatural 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.

The fact that LNG takes up much less space than natural gas is its key advantage.  

Six hundred cubic meters of natural gas turns into just one cubic meter of liquefied natural gas. 

This volume reduction is similar to reducing the volume of a beach ball to the volume of a ping-pong ball.

LNG is Transportable

Since the volume of LNG is 600 times smaller than natural gas, it is more efficiently transported over long distances. 

This takes place in specially designed trucks and ships.  

The real advantage is that LNG allows us to move natural gas from and to other areas around Australia and for export. 

This expands and diversifies Australian natural gas supplies, increases exports and our helps our positive balance of trade. 

All of this increases supply reliability and economic growth. 

Energy Content of LNG

LNG Energy ContentThe exact energy value depends on the gas source and the process used to liquefy the gas.

The energy value of LNG ranges from 24 MJ/L to 21 MJ/L. 

The energy density of LNG is 2.4 times greater than CNG. 

This makes it economical to transport.

The energy content of LNG is comparable to propane.

The density of LNG is roughly 0.41 kg/L to 0.5 kg/L, depending mostly on temperature and pressure.

"Stranded" Natural Gas

LNG also allows for the use of “stranded” natural gas deposits that are too small to justify pipeline construction.  

Conversion to LNG solves this problem. 

LNG provides the opportunity to economically transport and store this stranded natural gas.  

It is stored as a liquid until it is needed, at which point it is returned to its gaseous state.

Micro LNG Plants

Micro LNG plantA key factor in making use of the smaller stranded gas assets is the development of micro LNG plant technology. 

In order to find a cost effective solution, our parent company, Linde, has found a way to build a micro LNG plant (50 tonnes a day and less) at the same price per tonne as small scale plants (200 tonnes per day).

LNG and the Environment

LNG, which is predominantly Methane, is an odourless, non-toxic and non-corrosive.  

If spilled, the LNG evaporates quickly and disperses, leaving no residue.  

There is no environmental clean-up needed for LNG spills on water or land.

Source: Shell           

The LNG Process

As previously explained, natural gas becomes LNG by chilling it to −161°C.  

The liquefaction process also involves the removal of certain impurities, including dust, acid gases, helium, water and heavy hydrocarbons. 

It is important to remove all components that would freeze during the liquefaction process.

LNG Transport

The reduced volume facilitates efficient transport by sea or road.  

Specially designed cryogenic ships or cryogenic tanker trucks are used for its transport. 

Once at its destination, LNG is unloaded into storage facilities, where it is stored as a liquid until use. 

LNG Storage - Keeping it Cold

Storage pressure in these tanks is very low, at less than 10 kPa.  

The liquid is stored at its boiling point for the pressure at which it is stored (atmospheric pressure).  

As the vapour boils off, heat for the phase change cools the remaining liquid.  

As the insulation is very efficient, only a relatively small amount of boil off is necessary to maintain the desired temperature.

This occurrence is known as auto-refrigeration.  

The boil-off gas is not wasted, as it is used as a fuel source.

What is the Difference Between LNG and LPG in the Container?

LNG storage pressure in the container (vessel) is very low, at less than 10 kPa.

LPG pressure is much higher. 

At a typical ambient temperature, the LPG pressure is 858.7 kPa.

LNG temperature is −161°C.

LPG temperature is much closer to -42°C, except when the gas is being drawn from the vessel.

When it is being used, the liquid boils as it draws heat from the steel walls of the container (vessel) to vaporise.

LNG Regasification

When required for use, LNG is warmed back to natural gas in a process known as regasification.  

This regasification is achieved using a method involving heat exchangers.  

The natural gas can then be used on-site, sent through pipelines for distribution to homes and businesses or used as a fuel for large vehicles. 

In fact, there are numerous LNG applications.

The LNG Value Chain

LNG Value Chain

The LNG value chain consists of five interdependent activities:

♦  Exploration and production of natural gas

♦  Liquefaction of natural gas into LNG

♦  Transport from liquefaction facility to the final destination

♦  Receiving and storage at the final destination.

♦  Access to end users including regasification, when required

 

 

 

 

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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.