Q.
What is LNG?
A.
Liquefied Natural Gas, or LNG, is the liquid form of natural
gas, just like the gas produced in the North Sea and used
in homes and factories around the world for more than 25
years.
LNG is formed by cooling natural
gas to very low temperatures (minus 162 degrees Celsius),
at which point natural gas condenses into a liquid. This
process is referred to as liquefaction.
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Q.
Why convert natural gas to a liquid?
A.
Converting natural gas to a liquid reduces its volume by
around 600 to 1, making it much easier and economical to
transport over large distances and store in large quantities.
One tanker load of LNG is equivalent to 600 tanker loads
of natural gas. To return LNG back into natural gas it is
fed into a regasification plant where it is simply warmed.
After regasification the gas is distributed to domestic
and commercial consumers through pipelines.
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Q.
Why are looking to LNG as an alternative source of energy?
A.
After converting LNG back to natural gas, the natural gas
provides energy for homes and businesses. LNG has been used
for more than sixty years in countries such as the USA,
Korea and Japan, and improved technology is now making it
more economical to produce, transport and store, therefore
opening up a wider market for its use.
As a result LNG is becoming an increasingly
interesting alternative to oil or piped gas (natural gas
transported from its country of origin through pipelines).
LNG is the best technology for large-scale movement of natural
gas over long distances.
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Q.
How is natural gas liquefied?
A.
Natural gas is cooled in a large refrigeration system to
minus 162 degrees Celsius, minus 260 degrees Fahrenheit,
at either the point of origin (gas production field) or
the point of departure (LNG off loads terminal). Examples
of LNG producing countries are Australia, Algeria, Egypt,
Trinidad, Oman and Qatar.
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Q.
How is LNG kept cold?
A. LNG
is stored in large insulated tanks there is no further
cooling of liquid. The insulation of the tanks, as efficient
as it is, does result in some warming of the liquid,
called ‘boil
off’. This ‘boil off’ is collected from
the tank and sent to the gas output line connecting to
the national gas grid, or used as fuel on the site.
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Q.
Is LNG safe and how will it effect Milford Haven?
A.Yes, the
terminal has been designed and built to the stringent
National and European Standards. LNG has an excellent
record in all aspects of shipping, storage and regasification.
This is due to both the high technical standards that
are used in construction and operation and also the physical
properties of LNG, which are inherently less hazardous
than LPG.
Proposed LNG terminals are subject
to control by the Control of Major Accident Hazards (COMAH)
Regulations and must demonstrate it meets these requirements
to a Health & Safety
Executive before any plant can be operated. This report
considers all aspects of management and operation of the plant, particularly
potential accidents and how major accidents would be prevented. The operation
of LNG terminals is subject to ongoing inspection and audit by the Health and
Safety Executive.
An independent risk assessment
of proposed terminals is also undertaken. This considers
both the individual and the population at large including
local communities.
Navigational risk assessments
are also completed in close cooperation with the relevant
Port Authorities. At Milford Haven, the results of the
study indicated that the risks inherent in the movement
of LNG ships in the Haven are manageable and acceptable.
A number of additional risk management measures were
identified, which would further reduce residual risk.
Following on from this, extensive navigation simulations
were run by the Milford Haven Port Authorities with tug
captains providing assistance. The results again demonstrated
the Haven's capability to receive and safely handle LNG
carriers in future.
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Q.
Is LNG flammable?
A. LNG
vapors (natural gas) are not flammable if the mixture
with air is less than 5% or if the mixture with air is
higher than 15%.
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Q.
What is the safety record for LNG ships and terminals?
A.
The LNG industry has a long and excellent safety record,
due to strict industrial safety standards applied worldwide.
Until now there have been approximately 80,000 LNG
carrier voyages, with 16 million miles alone in 2005,
covering more than 100 million miles. For
more information on LNG tanker safety please click
here.
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Q.
What is the difference between LNG and LPG?
A.
Liquid Petroleum Gas (LPG) is often confused with LNG and
vice versa. LPG is composed primarily of propane (upwards
to 95%) and smaller quantities of butane, and is used primarily
for residential and commercial applications. LPG is maintained
as a liquid by means of elevated pressure. It is not possible
to liquefy natural gas solely by pressurizing. It is heavier
than air in it’s vapor state and has a wider flammability
range.
LNG consists almost entirely of
methane. LNG is odourless, colourless, non-corrosive and
non-toxic. Unlike LPG, LNG is stored at atmospheric pressure
at minus 160 degrees Celsius. An advantage of this low temperature,
atmospheric pressure storage is that if the top of a container
is removed, the LNG will simply boil (at a temperature of
minus 160 degrees). An open container of LNG at room temperature
looks and behaves like one containing boiling water. The
temperature of the liquid will stay at approximately minus
160 degrees Celsius until it has all evaporated assuming
pressure remains constant. This can be compared to boiling
water in a saucepan where the temperature of the water stays
at 100 degrees Celsius but steam is given off.
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Q.
Where does the LNG come from?
LNG mainly comes from the areas
in the world where large discoveries of gas have been made
such as North Africa, the Middle East, and West Indies.
Examples of LNG producing countries are Algeria, Trinidad,
Oman and Qatar.
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Q.
Where else in the world is LNG used?
LNG receiving terminals are located
throughout the world, predominantly in Japan, but also in
Korea, the USA, Belgium, Spain, France, Portuagal and Turkey.
In Europe several additional terminals are either under
construction or planned so as to meet growing demand for
cleaner energy sources.
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Q.
How will LNG be brought to Milford Haven?
A.
LNG would be delivered to Milford Haven by LNG carriers/ships,
which would berth at a jetty. LNG carriers are different
to the traditional oil tankers. The ships can carry
up to 145,000 cubic metres of LNG. For more information
on LNG tanker safety view our Health, Safety and Security page. LNG would be delivered to Milford Haven by
LNG carriers/ships, which would berth at a jetty. LNG carriers
are different to the traditional oil tankers. The ships
can carry up to 145,000 cubic metres of LNG. For more
information on LNG tanker safety view our Health,
Safety and Security page.
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Q.
How do you store LNG?
A.
LNG is stored in storage tanks of around 160,000 m3 capacity
and stored just above atmospheric pressure. The LNG tanks
are of a full containment design. In a full containment
system two tanks are employed, an inner tank which contains
the stored liquid, and an outer tank which provides security
in the event of any loss of containment or leak from the
inner tank.
The inner shell is made of a special
nickel alloy, designed to resist the low temperatures. The
outer shell is of pre-stressed concrete with a reinforced
concrete base slab and roof.
Sophisticated automatic protection
systems are employed to monitor the tank levels, pressures,
temperatures and any potential leakage from the inner tank.
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Q.
What are the air emissions from LNG operations?
A.
During the operation of an LNG terminal, atmospheric emissions
are mainly combustion emissions resulting from the burning
(sulphur free) natural gas. In the UK, LNG terminals are
subject to regulation by the Environment agency, under a
Process Authorisation granted under the Pollution Prevention
and Control (England & Wales) Regulations 1999. This
authorisation is only granted once the Environment Agency
is satisfied that Best Available Techniques (BAT) will be
employed in the operation and management of the terminal,
to eliminate, minimise and render harmless any resultant
emissions to the environment.
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Q.
How will LNG be distributed to domestic and commercial consumers?
A.
Before the LNG can be exported to the national gas grid
(NTS or national transmission network) it must be reverted
back to a gas. This is accomplished by warming the LNG in
a vaporizer (this process is called vaporization or regasification).
After regasification the gas will distributed to domestic
and commercial consumers through existing pipelines.
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