Roy L. Nersesian - Energy Economics: Markets, History and Policy

Table CW6.1 Historical Development of Refining Processes

Table CW8.1 Examples of Radioactivity in Bq

Table CW8.2 Likely Effects of Whole-body Radiation Doses

Compressed natural gas (2,0004,000 psi) can be transported in specially built tanks. The problem is the cost of building large-capacity cargo tanks that can withstand this magnitude of pressure with a cargo still four times greater in volume than in a liquefied state. However, there are special circumstances where compressed natural gas carriers are feasible such as small natural gas fields in remote areas of the Amazon River where reserves are not sufficient to justify building a long-distance pipeline or a liquefaction plant. Compressed natural gas carriers are useful for natural gas delivery to lightly populated Caribbean or Southeast Asian islands whose consumption is far too small to sustain an LNG import terminal, but where less costly natural gas can be substituted for diesel fuel for electricity generation. Compressed natural gas is not conducive to high volume, long-distance transport of natural gas.

With the exception of Russia and the US, much of the worlds natural gas reserves would be stranded if pipelines were the only means of transmission. The construction of long-distance undersea pipelines to connect remote fields in Iran, Qatar, Nigeria, Venezuela, Indonesia, and Malaysia with industrially developed nations thousands of miles away in waters that may be 23 miles deep with undersea mountains replete with deep chasms would be either impossible to construct or prohibitively expensive. The natural gas reserves for these nations remained stranded with no commercial value until a new means of transmission was devised. Just as liquefied gas liquids (propane and butane) are refrigerated for transport as a liquid at ambient pressure, so too can natural gas. As a liquid, natural gas takes up 610 times less volume than at ambient conditions with a specific gravity a little less than LPG. The problem is that natural gas is a liquid at atmospheric pressure at a much colder temperature of 161C (258F), which imposes severe constraints on tank design and insulation to prevent LNG from coming in contact with the hull. Conventional steel in ship hulls, if exposed to the cold temperature of LNG, is subject to instantaneous cracking, known as brittle fracture. A few mass-produced Liberty freighters during the Second World War sunk after their hulls split open from brittle fracture when the vessels sailed into cold north Atlantic waters. A steel belt welded around the hull of Liberty vessels resulted in no further losses from this cause. Better quality steel prevents brittle fracture at freezing ocean temperatures, but not from the cold of liquefied natural gas.