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== '''[[Industrial cooling tower]]''' ==
== '''[[Liquefied natural gas]]''' ==
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{{Image|TVA Cooling Towers.jpg|right|200px|Figure 1: Power plant counterflow cooling tower (note water vapor plumes)}}


{{Image|Crossflow Cooling Tower.jpg|right|200px|Figure 2: Process plant crossflow cooling tower (offstream for maintenance, no water vapor plume)}}
'''Liquefied natural gas''' or '''LNG''' is [[natural gas]] (consisting primarily of [[methane]], CH<sub>4</sub>) that has been converted into [[liquid]] form for ease of transport and storage. More simply put, it is the liquid form of  the natural gas that people use in their homes for cooking and for heating,


'''Industrial cooling towers''' are heat rejection systems used primarily to provide circulating cooling water in large industrial facilities. The circulating cooling water absorbs heat by cooling and/or condensing the hot process streams or by cooling hot rotating machinery and other hot equipment within the industrial facilities. The cooling towers then reject that absorbed heat by transferring it to the [[atmosphere]].  
A typical raw natural gas contains only about 80% methane and a number of higher boiling [[hydrocarbons]] as well as a number of impurities. Before it is liquefied, it  is typically purified so as to remove the higher-boiling hydrocarbons and the impurities. The resultant liquefied natural gas contains about 95% or more methane and it is a  
clear, colorless and essentially odorless liquid which is neither corrosive nor toxic.<ref name=CalifEnergyCommission>[http://www.energy,ca.gov./faq.html Frequently Asked Questions About LNG] From the website of the [[California Energy Commission]]</ref><ref name=CEE>[http://www.beg.utexas.edu/energyecon/lng/LNG_introduction.php Introduction To LNG] Michelle Michot Foss (updated January 2007), Center for Energy Economics (CEE), Bureau of Economic Geology, Jackson School of Geosciences, University of Texas</ref>


=== How a cooling tower works ===
LNG occupies only a very small fraction (1/600th) of the [[volume]] of natural gas and is therefore more economical to transport across large distances. It can also be stored in large quantities that would be impractical for storage as a gas.<ref name=CalifEnergyCommission>[http://www.energy,ca.gov./faq.html Frequently Asked Questions About LNG] From the website of the [[California Energy Commission]]</ref><ref name=CEE>[http://www.beg.utexas.edu/energyecon/lng/LNG_introduction.php Introduction To LNG] Michelle Michot Foss (January 2007), Center for Energy Economics (CEE), Bureau of Economic Geology, Jackson School of Geosciences, University of Texas</ref>


Basically, a cooling tower intimately contacts a flow of warm water with a flow of ambient air which is not saturated with water vapor (i.e, air which contains less water vapor than it is capable of containing). That causes part of the warm water to evaporate and the air absorbs that evaporated water. The heat required to evaporate  part of the water is derived from the water itself and thus causes the water to cool. This process is known as [[evaporative cooling]].<ref>{{cite book|author=Larry Drbal, Kayla Westra and Pat Boston|title=Power Plant Engineering|edition=1st Edition |publisher=Springer|year=1996|id=ISBN 0-412-06401-4}}</ref><ref>{{cite book|author=Robert H. Perry (deceased), Don W. Green and James O. Maloney (Editors)|title=[[Perry's Chemical Engineers' Handbook]]|edition=6th Edition|publisher=McGraw-Hill|year=1984 |id=ISBN 0-07-049479-7}}</ref> The net result is that the air leaving the tower is saturated with water vapor and the unevaporated water leaving the cooling tower has been cooled.


An evaporative cooling tower is referred to as a ''wet cooling tower'' or simply a ''cooling tower''. Such towers can cool water to a temperature that approaches the [[wet-bulb temperature]] of the ambient air. The average ambient air wet-bulb temperature chosen as the design basis essentially determines the size of the cooling tower, and the size of a cooling tower is inversely proportional to the design wet-bulb temperature.
''[[Liquefied natural gas|.... (read more)]]''
 
''[[Industrial cooling tower|.... (read more)]]''


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Revision as of 11:59, 17 November 2012

Liquefied natural gas

Liquefied natural gas or LNG is natural gas (consisting primarily of methane, CH4) that has been converted into liquid form for ease of transport and storage. More simply put, it is the liquid form of the natural gas that people use in their homes for cooking and for heating,

A typical raw natural gas contains only about 80% methane and a number of higher boiling hydrocarbons as well as a number of impurities. Before it is liquefied, it is typically purified so as to remove the higher-boiling hydrocarbons and the impurities. The resultant liquefied natural gas contains about 95% or more methane and it is a clear, colorless and essentially odorless liquid which is neither corrosive nor toxic.[1][2]

LNG occupies only a very small fraction (1/600th) of the volume of natural gas and is therefore more economical to transport across large distances. It can also be stored in large quantities that would be impractical for storage as a gas.[1][2]


.... (read more)

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