Pipeline, LNG

The internally-insulated LNG pipeline appears to be a viable solution with attractive economic advantages. It is particularly attractive in areas such as Northern Canada, where low ambient temperatures prevail for much of the year. 

Based on the recommendations of the IAEA mission held in April 1990 at Temelin, the following measures concerning a liquified natural gas (LNG) pipeline are being implemented ... 

Fig. 7.45. Cooling-station spacing as a function of LNG pipeline diameter for two insulation types.

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. 

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. 

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. 

LNG—consisting of ethane, propane, butane, and natural gasoline (condensate)—arrives at the plant for upgrading before it is sent to petrochemical plants and refineries as feedstock. Residue gas is sold to the interstate and intrastate pipeline network. MESA, one of the world s major crude helium producers, also delivers helium to a pipeline operated by the U.S. Bureau of Mines. 

Hoff (1983) Ignition of spill after simulated pipeline rupture LNG 15 ... 

This study investigated risks to the public from serious accidents which could occur at the industrial facilities in this part of Essex, U.K. Results are expressed as risk to an individual and societal risk from both existing and proposed installations. Risk indices were also determined for modified versions of the facilities to quantify the risk reduction from recommendations in the report. Nine industrial plants were analyzed along with hazardous material transport by water, road, rail and pipeline. The potential toxic, fire and explosion hazards were assessed for flammable liquids, ammonia, LPG, LNG, and hydrogen fluoride (HE). The 24 appendices to the report cover various aspects of the risk analysis. These include causes and effects of unconfined... 

About 20 percent of the world s natural gas production was exported during the late 1990s, three-quarters of it through pipelines, and the rest by LNG tankers. The former Soviet Union, Canada, the Netherlands, and Norway are the largest pipeline exporters, while Indonesia, Algeria, and Malaysia dominate the LNG trade. The largest importers of piped gas are the United States, Germany, Italy, and France Japan and South Korea buy most of the LNG. 

The natural-gas industries of Japan, Korea and Taiwan are based almost entirely on gas imported by tanker as liquified natural gas (LNG). These insular and peninsular economies produce almost no domestic natural gas, and until recent efforts to develop production on the Russian island of Sakhalin immediately north of Japan, import of natural gas by pipeline from nearby has not seemed a realistic alternative, In 1999, LNG imports provided about 12 percent of Japan s primary energy, 9 percent of South Korea s, and 6 percent of Taiwan s. In turn, these three countries together accounted for 79 percent of the world s international movements of LNG,... 

Because much of the world lacks the natural gas resources and transportation pipelines of the United States, remote natural gas must be liquefied and transported by ship. Gas-rich countries want to capture stranded gas by liquefying and shipping it to gas-poor regions as LNG. The gas-poor countries enter into contracts so that a long-term supply is available to warrant the investment in the electricity-generating infrastructure. The overall investment is enormous, not only in the liquefaction plant, but in the refrigerated tankers and the regasification plant at the deliveiy site. 

Sometimes LNG is the only option in regions and countries where political issues constrain pipeline development. 

I. The globalization of transportation has changed the economic relationship between primary fuel resource countries and user nations. Supertankers and pipelines have made eveiy oil field a strategic neighbor for most countries. What have gas pipelines and LNG done for natural gas global availability and its use, arguably as an environmentally more benign fuel Where does it leave coal ... 

Remote and relatively small gas fields cannot justify the high investment cost associated with liquefied natural gas (LNG) production or a gas pipeline system. Conversion of the natural gas from such gas fields to liquids by a gas-to-liquids facility allows these gas fields to be exploited. 

These results stimulated a number of studies, both in industry (Conoco, Esso, Shell Pipeline) and in academia (University of Maryland, M.I.T.). The objective was, primarily, to delineate the mechanism that led to these explosive events. The results of many small-scale experiments, primarily conducted by Shell Pipeline Corporation and M.I.T., led to the hypothesis that the apparent explosion was, in fact, a very rapid vaporization of superheated LNG. Contact of LNG, of an appropriate composition, with water led to the heating of a thin film of the LNG well above its expected boiling temperature. If the temperature reached a value where homogeneous nucleation was possible, then prompt, essentially explosive vaporization resulted. This sequence of events has been termed a rapid phase transition (RPT), although in the earlier literature it was often described by the less appropriate title of vapor explosion. 

Concerning the projected energetics from LNG RPTs, SheU Pipeline measured overpressures from small-size (0.1 m = 30 gallons) spills both in the air and under water. From calibration tests in their spill apparatus. 

Enger and Hartman (1972a-d) carried out extensive studies at the Shell Pipeline Corporation. The work was divided into two phases. In the first, or exploratory part, a few small-scale LNG spills were made on water ranging from 273 to 356 K no RPTs were noted. Also in the same phase, several pure liquefied gases were spilled on water. A brief summary of their results is shown in Table V. 

It was fortunate that, for the BURRO-9 test, RPTs were anticipated and a pressure transducer was located in the air about 30 m from the LNG injection point. The reflected overpressures at various times are shown in Table Vin. Also given on the same table are the TNT equivalents assuming a free-air, point-source explosion. Some equivalents were significantly higher than noted in the smaller Shell Pipeline tests. 

The most complete set of overpressure measurements was obtained by Enger and Hartman in the Shell Pipeline study. The data were collected using a spill tank 1.5 m deep and 2.1 m in diameter. The tank was made of 6.3-mm mild steel plate with 12-mm-diameter circumferential reinforcing rods spot-welded to the exterior. The capacity was 5.3 m, but during the tests the water depth was held constant at 1 m (3.8 m ). The LNG was contained in a 0.13-m Dewar made from 6.3-mm mild steel with a stainless steel inner liner. The annulus was evacuated. When spilling, the Dewar lip was about 0.75 m above the water surface. 

Fig. 7. Overpressures from LNG RPTs. Note All pressures are reflected values ( ) Shell Pipeline, 1972 tests (x) LLNL/NWC China Lake tests, 1980 (V) Shell Research Maplin Sands tests, 1980, outside visible cloud (A) Shell Research Maplin Sands tests, 1980, inside visible cloud.

Enger, T., and Hartman, D. E. (1972a). LNG Spillage on Water, Tech. Prog. Rep. 1-72. Shell Pipeline Corp. 

Most of the natural gas that is extracted in the United States is also used there. Natural gas is also imported. The gas is shipped in huge, double-hulled tankers in the form of liquefied natural gas (LNG). Gas to be shipped is cooled to -260°F (-162°C), which reduces it to 1/600 of its original volume. At its final destination, the condensed gas is heated, which causes it to expand. It is offloaded from the tankers into pipelines at off-shore terminals. 

The composition of natural gas varies with the source, but essentially is made up of methane, ethane, propane, and other paraffinic hydrocarbons, along with small amounts of hydrogen sulfide, carbon dioxide, nitrogen, and. in some deposits, helium. Natural gas is found underground at various depths and pressures, as well as in solution with crude-oil deposits. Principal gas deposits are found in the United States, Canada, the former Soviet Bloc, and the Middle East. The analysis of a gas sample taken from the Panhandle natural gas field in Texas is given in Table 1. Because numerous parts of the earth do not have natural gas at all, or where supply is less than demand, much natural gas is transported, notably by pipeline in the gaseous or liquid phase and across the seas in specially-designed LNG (liquefied natural gas) earners. 

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