Liquefied Natural Gas as it relates to the Field of Cryogenics
John W. Bonn
VJ Systems, LLC
johnbonn@vjsystems-lic.com
Today the world is looking for a cleaner fuel and Liquefied Natural Gas (LNG) plays a large part in achieving this goal. LNG in a liquid form is at -162°C (-259°F) and considered a cryogenic fluid by most everyone’s standards.
Actually, LNG is not used as a liquid; it is used as an ambient temperature gas. The only reason natural gas is liquefied is to transfer it over long distances from the liquefaction site and ship it to a receiving terminal. Then it is vaporized to near ambient temperature and sent to a gas fired power plant or into a gas pipeline distribution system. The need for more clean energy increases the present requirement for natural gas and related equipment.
What does this mean to the cryogenic industry in North America? North America is the largest consumer of energy in the world. Additional receiving terminals are being built to meet this demand for a cleaner burning fuel. The large natural gas reserves are located in Alaska, Russia, Middle East, Western Africa, Venezuela and Australia and require transporting by ship in the liquid form to North America and other consuming nations like Europe, India, China, Korea and Japan. Natural gas is over 600 times denser as a liquid and requires less volume to ship huge amounts to these consuming nations. The liquefication site fills very large LNG cryogenically insulated ground based tanks on a continuing basis and then when a ship is at the dock the LNG in the tank is transferred to the ship. All transfer equipment including the pumps, valves and piping are cryogenically rated.
There is a several year backlog in manufacturing of these large LNG ships. The newer ships being built today are getting even larger. The standard LNG ship will hold about 135,000m3 (35.6 million gallons). The LNG ships being built today are designed to hold about 205,000m3 (54.1 million gallons) of LNG. This is the largest cryogenic equipment ever built to hold and transfer LNG across the ocean. However, there are ground based tanks being built at about the same volume of the ships to transfer most all of the LNG to these tanks when they reach a LNG receiving terminal.
When a ship reaches a receiving terminal it will be unloaded as fast as possible to keep the ship’s operating cost down and demurrage for extended time in port. The optimum time the ship is at the dock is about 12 hours. In reality, I believe the time in port is about 13 to 14 hours. This means the transfer rate is very high to load or unload a ship of 205,000m3 of LNG. This will relate to an average flowrate of about 17,084 m3/hour or about 75,000 gpm. The loading rate of the ships is the same as the unloading rate.
These large flowrates require transfer lines of at least 30″ NPS pipe and even larger if the transfer line is fairly long. In most cases the transfer line from the ship is at about 1.6 to 2 kilometers (1 to 1.25 miles) long and some lines are as long as 8 kilometers (5 miles). Certainly the longer the line the larger the pipe size and the better the cryogenic insulation system should be for these critical transfer lines. The reason for the longer lines in most cases is because the shoreline is too shallow at the terminal location and these large ships have a very deep draft and cannot get close to shore, so the transfer lines are extended to reach the ship.
Presently North America has 5 operating LNG receiving terminals and there are 59 LNG terminals proposed for North America alone. The actual number that will be built in North America is not yet determined, but the Federal Energy Regulatory Commission (FERC) has already approved 12 new LNG terminals for the United States. In addition, 2 LNG offshore terminals in the Gulf of Mexico have been approved by the U.S. Coast Guard. Canada has approved two LNG terminals and Mexico has approved 3 LNG terminals. In summary this is probably the largest market for cryogenic equipment in North America and worldwide since the cryogenic industry has been liquefying cryogenic fluids.
The cost of this equipment for these terminals and ships is very large compared to all other cryogenic equipment markets. A LNG ship for example costs about $1,200/m3 x 150,000 m3 ship volume = $180 million. Each LNG liquefication terminals and receiving terminals may have several million dollars of cryogenic equipment. Considering the number of LNG terminals being built and others being considered it is definitely a very large requirement for cryogenic equipment and tanks and ships for at least the next 10 to 15 years.
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