LNG

For the above reasons, gas Is typically economic to develop only if it can be used locally, i.e. if a local demand exists. The exception to this is where a sufficient quantity of gas exists to provide the economy of scale to make transportation of gas or liquefied gas attractive. As a guide, approximately 10 Tcf of recoverable gas would be required to justify building a liquefied natural gas (LNG) plant. Globally there are few such plants, but an example would be the LNG plant in Malaysia which liquefies gas and transports it by refrigerated tanker to Japan. The investment capital required for an LNG plant Is very large typically in the order of 10 billion. 

Sales gas, which is typically made up of methane (CH ) and small amounts of ethane (C2Hg), can be exported by refrigerated tanker rather than by pipeline and has to be compressed by a factor of 600 (and cooled to -150°C). This is then termed Liquefied Natural Gas (LNG). 

Where the distance to the customer is very large, or where a gas pipeline would have to cross too many countries, gas may be shipped as a liquid. Gas has to be chilled to -160°C in a LNG plant to keep it in liquid form, and is shipped in refrigerated tankers. To condition the gas for liquefaction any COj, HjS, water and heavier hydrocarbons must be removed, by the methods already discussed. The choice of how much propane and butane to leave in the LNG depends upon the heating requirements negotiated with the customer. 

LNG plants require very high initial investments in the order of several billion dollars, and are therefore only viable in cases were large volumes of reserves (typically 10 Bscf) have been proven. 

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Liquefied natural gas (LNG) natural gas that has been Hquefied by reducing its temperature to 111 K at atmospheric pressure. It remains a Hquid at 191 K and 4.64 MPa (673 psig). 

Liquefied natural gas (LNG) also plays a large role in both the transportation and storage of natural gas. At a pressure of 101.3 kPa (1 atm), methane can be Hquefted by reducing the temperature to about — 161°C. When in the Hquid form, methane occupies approximately 1/600 of the space occupied by gaseous methane at normal temperature and pressure. In spite of the very low temperature of the Hquid, LNG offers advantages for both shipping and storing natural gas. 

The use of natural gas as a hydrocarbon source depends on transportation. Over long distances and waterways, Hquefied natural gas (LNG) is dehvered in cryogenic tankers or tmcks (see Gas, natural Pipelines). In the United States, about 22% of the fossil-fuel energy used in 1990 was gas, but in Japan this percentage was much less. 

The largest pipeline transport of gas, by far, is the movement of methane (natural gas). Natural gas can be Hquefted, but it is not pipelined in Hquid form because of cost and safety considerations. For overseas transport, it is shipped as Hquefted natural gas (LNG) in insulated tankers, unloaded at special unloading faciHties, vaporized, and then transported over land in pipelines as a gas. 

Pipeline systems for transporting anhydrous ammonia that are urea and ammonium nitrate (UAN) and LNG compatible, exist in Europe, Mexico, and the Soviet Union. Export-oriented ammonia producing countries utilize huge ocean-going tankers that contain up to 50,000 t for distribution of ammonia. Co-shipment in refrigerated LNG tankers is usuaky done. 

LNG-20, a long-lasting levonorgestrel-releasing lUD, is still under development at the Population Council. Other lUDs in development are the Multiload Mark II (marketed in Einland), the Uterine-Occluding Device, and two new copper devices, the OmbreUe and the Eincoid-350. 

Liquefied Natural Gas (LNG) plants can be categorized as peakshaving or baseload. Peakshaving LNG plants are built at the consumer end of natural gas pipelines to accumulate LNG in storage tanks for later vaporization and sendout into the local grid during periods of peak demand. Baseload LNG plants provide a steady base supply of natural gas to utiHty companies, generally by transportation of LNG by ship from one country to another. 

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