Unlike the LPG (Liquefied Petroleum Gas) which is obtained from the distillation of petroleum, LNG (Liquefied Natural Gas) comes directly from the oil fields, alone or accompanied by oil. And usually has a composition of methane (85%), ethane (10%) and propane (5%).

The   LNG   (LNG) is   natural gas   that has been processed to be transported in liquid form. It is the best alternative to monetize reserves in remote places where it is not economical to bring gas to market either directly   pipeline   or for generating electricity. Natural gas is transported as a liquid at atmospheric pressure and -162 ° C. So, to transport liquefied natural gas, has to achieve to reduce the volume of natural gas by 600 times, which will be transported in special ships called   methane. LNG is odorless, colorless, non-toxic, density (relative to water) is only 0.45 and it burns on contact with air at concentrations of 5-15%.

LIQUEFACTION PROCESS

To convert natural gas into liquid, treated to approximately -161 ° C gas, which is the temperature at which methane-its main component becomes a liquid-cooled forms. The liquefaction process is similar to the common cooling: cooling gases are compressed producing cold, such as propane, ethane / ethylene, methane, nitrogen or mixtures thereof, which then evaporates as it exchanges heat with the liquid gas stream natural. Thus, the natural gas is cooled to the point where it becomes a liquid. Once liquid gas has been subjected to a Joule-Thompson process or work extraction expansion so that it can be stored at atmospheric pressure. The LNG produced is stored in special tanks to be later transferred to special transport tankers.

The design of these plants is governed by strict rules in the LNG industry are four designers plants used industrially: process swapped spiral pipe Air Products (APCI and APX), the cascade optimized Phillips, triple Linde cycle refrigerant and the cold-box process with refrigerant mixture of Black and Veatch (PRICO).

All these processes are used in industry and design competitions are conducted to select the process that will generate the most profitable over its lifetime project.

LNG STORAGE

The LNG is stored at -161 ° C and atmospheric pressure in special cryogenic tanks for low temperature.The typical LNG tank has double wall: an outer wall of reinforced concrete, coated carbon steel and an inner wall of 9% nickel steel. Safety and strength are primary design considerations when building these tanks, which are designed to withstand earthquakes and high winds.

TRANSPORTATION OF LNG

LNG is transported at atmospheric pressure in specially constructed vessels with double hulls. The cargo containment system is designed and constructed using special materials for insulation and tank to ensure the safe transport of this cryogenic load.

The LNG cargo tanks of the vessel is maintained at its saturation temperature (-161 ° C) throughout the entire navigation, but it allows a small amount of steam to dissipate by boiling in a process called "cooling author." The evaporated gas is used to drive the motors of the ship.

Approximately 40% of LNG ships currently in service have cargo containment systems of membrane type, so they have a very similar appearance to other freighters. The rest of the ships have a containment system more particular load, which includes four or more large spherical tanks. Both types of containment system with a history of extremely safe and reliable operation.

LNG REGASIFICATION

Once the LNG tanker arrives at the regasification terminal in the market, the LNG is pumped from the ship to storage tanks. LNG tanks are similar to those used in the liquefaction terminal. Generally, the discharge vessel requires about 12 hours.

Then, LNG gas returns to its original state. To do this, is pumped from the storage tanks and heated with misters to the delivery terms specified by pipeline companies and end users located downstream of the pipe. Subsequently, the gas is distributed to users by a conventional pipeline.

Another form of distribution is to transport LNG tanks aboard specially designed for loading from the regasification plants receiving the product for LNG tankers, to customers who have LNG tanks are designed to store and re-gasification of gas for use. This is the only mode of transport LNG to customers can not reach the conventional pipeline.