Liquefied natural gas

Liquefied natural gas is a natural gas that is purified and cooled to -161 degrees Celsius to become a liquid. This process reduces its volume 600 times, which is like a beach ball being compressed into a ping pong ball.

The liquid is then loaded onto an LNG ship and transported internationally to a re-gasification terminal. At the terminal, the liquid is heated and turned back into gas.

LNG is refrigerated natural gas, it's colourless, odourless and non-toxic. LNG will not pollute land or water resources.

Converting natural gas to LNG

The CSG arrives at the LNG facility via a 530km gas transmission pipeline.

The LNG facility, located on the southwest side of Curtis Island, incorporates key infrastructure including two production units (known as ‘trains’), each with the capacity to produce 4.5 million tonnes per annum of LNG, two 160,000m3 LNG storage tanks, a loading jetty for the LNG ships, and a control centre.

After the gas has been delivered to the LNG facility, and before it enters the liquefaction process, impurities such as nitrogen, carbon dioxide and water are removed and the gas is dehydrated. 

The dry gas is fed to the refrigeration systems where it is liquefied into the LNG product through a combination of heat exchange and pressure reduction with refrigerants.

Optimized Cascade® technology is used for liquefying the gas to -161 degrees Celsius. This liquefaction system consists of three refrigeration circuits: propane, ethylene and methane, each progressively lowering the temperature until the gas becomes LNG.  

The LNG product is then piped to the LNG storage tanks. Gases which continually boil out of the LNG as it warms slightly in the storage tank are captured and returned to the process to be re-liquefied. Liquefaction allows gas to be shipped economically and stored safely.

LNG technology

Australia Pacific LNG’s shareholder and LNG facility operator, ConocoPhillips, owns and licenses the Optimized Cascade® technology for liquefying natural gas. This technology was first adopted by the Kenai LNG plant that started operation in 1969. With 45 years of LNG plant operating experience and cutting-edge technology improvements, ConocoPhillips continues to provide cost effective, high-value natural gas liquefaction solutions. Since Kenai, the Optimized Cascade® process has been licensed by owners of 24 additional LNG trains around the world.

How is LNG stored?

LNG is stored at atmospheric pressure in especially engineered and constructed double-walled storage tanks. Australia Pacific LNG has two LNG tanks, each with the capacity of 160,000m3, a diameter of 87m and height of 32m. The tank outer walls are made from concrete over one metre thick and the inner tank is made from a steel / nickel alloy, specifically designed to keep LNG cold.

The tanks are not pressurised and are designed to safely trap any leaks between the inner and outer walls. Because LNG is not stored under pressure, it is not explosive when stored in tanks or on ships. It is also not explosive if released into the atmosphere. As LNG is lighter than air, it will float away if released, quickly vaporising. Sophisticated monitoring systems provide constant surveillance for internal leaks.

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