Minggu, 02 Oktober 2011

LNG Processing

Natural gas exists in gaseous form or as a mixture with oil in natural underground reservoirs all around the world. It comprises primarily methane with smaller amounts of other hydrocarbon, nitrogen, carbon dioxide and other gases. In its treated form, it is not economical and almost impossible to transport to countries which are oceans apart. This problem has been solved with the gas liquefaction process.
Processed natural gas turns into liquid when cooled to -160°C. Through the liquefaction process, methane is reduced to 1/600th of its former volume, allowing larger volumes of natural gas to be transported via LNG tankers to distant markets. Once it reaches its destination, it will be heated to convert from its liquid state into gas again before it can be used.

Basically, the process involves the following steps:

Separation of Liquid from Gas
Natural gas from the offshore wells first goes to the Slugcatcher where the bulk of hydrocarbon liquid was separated from the natural gas.

Removal of Impurities
It is then fed into the Acid Gas Removal Unit to remove impurities such as carbon dioxide, hydrogen sulfide and other organic sulphur compounds. The natural gas is then dried in the Dehydration Unit to avoid freezing and traces of mercury are removed using activated carbon to avoid corrosion in the liquefaction unit.

Treatment of Other Components
Meanwhile, the natural gas liquid from the liquefaction section is sent to the Fractionation Unit where various components are separated and purified by distillation process to produce refrigeration components, commercial grade propane and butane for Liquefied Petroleum Gas (LPG), and stabilised gasoline products.

The dried natural gas is then sent to the Liquefaction Unit to remove natural gas liquid. The light natural gas stream, mainly methane, is then subsequently cooled and liquefied in the Main Cryogenic Heat Exchanger (MCHE).

The LNG leaving the Liquefaction Unit is stored at -160 °C at atmospheric pressure in insulated storage tanks before it is shipped to various market locations

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