A turbine is a means of extracting work from a fluid as it changes from a high pressure to a low pressure. A turbine consists of a shaft carrying a number of vanes or blades, and there is a transfer of energy between the fluid and the rotor. In a turbine, the fluid does work on the rotor.
For gas, steam or water turbines, the fluid is accelerated in a set of fixed nozzles, and the resulting high-speed jets of fluid then change their direction as they pass over a row of curved blades attached to a shaft. A force is exerted on the blades equal to the rate of change of momentum of the fluid, and this produces a torque at the rotor shaft. The momentum of the fluid in the tangential direction is changed and so a tangential force on the rotor is produced. The rotor therefore rotates and performs useful work, while the fluid leaves it with reduced energy. The velocity of the fluid is reduced to somewhere near the value it possessed before entering the nozzles.
For any turbine, the energy held by the fluid is initially in the form of pressure. For a turbine in a hydro-electric scheme, water comes from a high-level reservoir: in a mountainous region, several hundred metres head may thus be available, although water turbines are in operation in other situations where the available head is as low as three metres or less. For a steam turbine, the pressure of the working fluid is produced by the addition of heat in a boiler; in a gas turbine, pressure is produced by the chemical reaction of fuel and air in a combustion chamber.
The impulse (or constant pressure) turbine has one or more fixed nozzles, in each of which the pressure is converted to the kinetic energy of an unconfined jet. The jets of fluid then impinge on the moving blades of the rotor, where they lose practically all their kinetic energy and, ideally, the velocity of the fluid at discharge is only just sufficient to enable it to move clear of the rotor.
In a reaction turbine, the change from pressure to kinetic energy takes place gradually as the fluid moves through the rotor and, for this gradual change of pressure to be possible, the rotor must be completely enclosed and the passages in it entirely full of the working fluid.
It was during the oil crisis of the early 1970s that modern interest in wind turbines took form. From this period, the basic wind energy conversion system for power generation has gradually taken shape. Today, the basic system starts with a large rotor comprising two, three or four blades mounted on a horizontal shaft at the top of a tall tower. The blades interest the wind and capture the energy it contains, energy which causes them to rotate in a vertical plane about the shaft axis. The slow rotation of the shaft is normally increased by use of a gearbox, from which the rotational motion is delivered to a generator.
Tuesday, 21 July 2009
Friday, 17 July 2009
Lowest ammonia prices
The production of ammonia (NH3) is an energy intensive process. The Haber-Bosch process uses natural gas and air to create ammonia. It takes about 750 kg of natural gas and 30,000 MJ of energy to produce 1 tonne of ammonia. Hydrocarbon gas (CH4) is now used to create ammonia because hydrocarbon gas is cheap. A byproduct of this Haber-Bosch process is carbon dioxide, but other methods of ammonia production have been used in the past that don’t use hydrocarbons and don’t create carbon dioxide.
Currently, the Nymex (New York Mercantile Exchange) price of natural gas is near the 52-week low of $3.50 per million BTU.
Average ammonia prices today are less than half of those a year ago, and profits of ammonia producers are more than 50% down, due to the decrease in international ammonia prices. For example, Saudi Fertilizers Company reported last week that net profits of $128M for the 3 months to June were 60% down on a year ago.
The price of Gulf of Mexico anhydrous ammonia was $800 per ton in September 2008 but, by January 2009, the price had fallen to below $200 per ton. Anhydrous ammonia is now trading at around $160.00 per ton from the Gulf of Mexico and the Black Sea. The current price of ammonia is within the price range experienced during the 10-year period from 1998 to 2007 of $140 to $170 per short US ton.
The high proportion of natural gas used in ammonia manufacture means that, under most market conditions, a strong correlation exists between the price of natural gas and the price of ammonia. Historically, natural gas accounts for 70% to 90% of the cost of ammonia production. Additionally, the current low price is due to the global financial crisis, large remaining distribution stocks, and a late North American harvest season.
The non-functioning of credit markets constrained ammonia consumers in advance purchases, reducing demand. Ammonia suppliers overproduced, in anticipation of a high demand due to high commodity prices. Consequently, the current supply of ammonia greatly exceeds the demand and ammonia producers are curtailing production.
Ammonia supply is a complex issue and involves; ammonia prices, natural gas contract prices, opportunity costs of using natural gas to produce ammonia, ammonia production and inventory, production technology and capacity, and global competition with ammonia imports and exports.
Annual US production of ammonia has steadily declined over the last decade, whilst imports have more than doubled to satisfy the increasing demand and North America is the world’s largest ammonia importer. North America accounts for more than one-third of world ammonia trade and much of the US imported ammonia is from Trinidad. China consumes one-third of the world’s ammonia production but doesn’t have much impact on trading because it consumes almost all of the ammonia that it produces.
Production of ammonia in Western Europe had substantially decreased within the last decade, with the exception of Belgium and Germany, whilst Russian ammonia production has increased, due to the availability of cheap natural gas, the major ingredient of ammonia using the Haber-Bosch process.
Currently, the Nymex (New York Mercantile Exchange) price of natural gas is near the 52-week low of $3.50 per million BTU.
Average ammonia prices today are less than half of those a year ago, and profits of ammonia producers are more than 50% down, due to the decrease in international ammonia prices. For example, Saudi Fertilizers Company reported last week that net profits of $128M for the 3 months to June were 60% down on a year ago.
The price of Gulf of Mexico anhydrous ammonia was $800 per ton in September 2008 but, by January 2009, the price had fallen to below $200 per ton. Anhydrous ammonia is now trading at around $160.00 per ton from the Gulf of Mexico and the Black Sea. The current price of ammonia is within the price range experienced during the 10-year period from 1998 to 2007 of $140 to $170 per short US ton.
The high proportion of natural gas used in ammonia manufacture means that, under most market conditions, a strong correlation exists between the price of natural gas and the price of ammonia. Historically, natural gas accounts for 70% to 90% of the cost of ammonia production. Additionally, the current low price is due to the global financial crisis, large remaining distribution stocks, and a late North American harvest season.
The non-functioning of credit markets constrained ammonia consumers in advance purchases, reducing demand. Ammonia suppliers overproduced, in anticipation of a high demand due to high commodity prices. Consequently, the current supply of ammonia greatly exceeds the demand and ammonia producers are curtailing production.
Ammonia supply is a complex issue and involves; ammonia prices, natural gas contract prices, opportunity costs of using natural gas to produce ammonia, ammonia production and inventory, production technology and capacity, and global competition with ammonia imports and exports.
Annual US production of ammonia has steadily declined over the last decade, whilst imports have more than doubled to satisfy the increasing demand and North America is the world’s largest ammonia importer. North America accounts for more than one-third of world ammonia trade and much of the US imported ammonia is from Trinidad. China consumes one-third of the world’s ammonia production but doesn’t have much impact on trading because it consumes almost all of the ammonia that it produces.
Production of ammonia in Western Europe had substantially decreased within the last decade, with the exception of Belgium and Germany, whilst Russian ammonia production has increased, due to the availability of cheap natural gas, the major ingredient of ammonia using the Haber-Bosch process.
Tuesday, 7 July 2009
Everyday ammonia leaks
After an ammonia gas leak, and for the second day, fire crews tackle a blaze at a food processing plant in Cudahy, Wisconsin. Residents near the plant had previously been evacuated.
This ammonia leak is the most recent in a catalogue of worldwide accidents involving this pollutant of key environmental concern that can cause serious or even fatal respiratory injuries …
6 July Belleville, Illinois
Residents in the immediate vicinity of a food processing plant were confined indoors after the St Clair County HAZMAT team found an ammonia leak.
6 July Waggaman, Louisiana
Residents reported burning eyes and strong odors following a release of ammonia when a heavy thunderstorm resulted in a power outage at a manufacturing facility.
5 July Cotswold Dene, UK
A factory had to be evacuated when a large ammonia leak needed firefighters with breathing apparatus to stem the leak in a refrigeration unit.
1 July Dallas, Texas
An ammonia leak prompted the evacuation of 70 workers from a food packaging company.
27 June Tertre, Belgium
Two people were injured when an explosion caused substantial damage to a fertilizer plant, caused by plant design weaknesses and operating procedure deficiencies.
27 June Alberta, Canada
Police closed off streets whilst HAZMAT units investigated an ammonia leak from three 682 kg ammonia tanks and paramedics checked workers evacuated from the facility.
25 June Lawrence, Indianapolis
An ammonia leak forced a few homes and a Wal-mart to evacuate when 4 cubic meters of ammonia leaked out of a tank in just 40 minutes, sending a cloud of ammonia into the air.
24 June Aurora, Illinois
An ammonia leak at a carbon dioxide liquefaction plant was caused by a sticking valve and a potentially serious situation was averted.
22 June Jefferson City, Missouri
A damaged regulator caused an ammonia leak, prompting the evacuation of a business whilst firefighters wearing HAZMAT suits investigated.
21 June Bayou La Batre, Alabama
Residents in the immediate vicinity of a food processing plant were confined indoors and an officer was transported to USA Medical Center after suffering from ammonia inhalation.
20 June Lumber Bridge, North Carolina
One person was killed and three people were injured when ammonia leaked at a food processing plant.
9 June Garner, North Carolina
38 people were injured and three fire fighters were treated for ammonia inhalation when a 130 cubic meter refrigeration system ruptured in the aftermath of an explosion.
The above incidents are only the ones that have been reported and I’d suggest that they are only a fraction of the total number of daily global accidental ammonia leaks.
Ammonia emissions produce environmental problems, from acid soil to biodiversity reductions and dust, which cause health problems such as asthma. Biomass burning creates ammonia and global ammonia emissions have more than doubled since pre-industrial times.
Exposure to high concentrations of ammonia can result in lung damage and death to humans, whilst ammonia in even dilute concentrations is highly toxic to aquatic animals.
This ammonia leak is the most recent in a catalogue of worldwide accidents involving this pollutant of key environmental concern that can cause serious or even fatal respiratory injuries …
6 July Belleville, Illinois
Residents in the immediate vicinity of a food processing plant were confined indoors after the St Clair County HAZMAT team found an ammonia leak.
6 July Waggaman, Louisiana
Residents reported burning eyes and strong odors following a release of ammonia when a heavy thunderstorm resulted in a power outage at a manufacturing facility.
5 July Cotswold Dene, UK
A factory had to be evacuated when a large ammonia leak needed firefighters with breathing apparatus to stem the leak in a refrigeration unit.
1 July Dallas, Texas
An ammonia leak prompted the evacuation of 70 workers from a food packaging company.
27 June Tertre, Belgium
Two people were injured when an explosion caused substantial damage to a fertilizer plant, caused by plant design weaknesses and operating procedure deficiencies.
27 June Alberta, Canada
Police closed off streets whilst HAZMAT units investigated an ammonia leak from three 682 kg ammonia tanks and paramedics checked workers evacuated from the facility.
25 June Lawrence, Indianapolis
An ammonia leak forced a few homes and a Wal-mart to evacuate when 4 cubic meters of ammonia leaked out of a tank in just 40 minutes, sending a cloud of ammonia into the air.
24 June Aurora, Illinois
An ammonia leak at a carbon dioxide liquefaction plant was caused by a sticking valve and a potentially serious situation was averted.
22 June Jefferson City, Missouri
A damaged regulator caused an ammonia leak, prompting the evacuation of a business whilst firefighters wearing HAZMAT suits investigated.
21 June Bayou La Batre, Alabama
Residents in the immediate vicinity of a food processing plant were confined indoors and an officer was transported to USA Medical Center after suffering from ammonia inhalation.
20 June Lumber Bridge, North Carolina
One person was killed and three people were injured when ammonia leaked at a food processing plant.
9 June Garner, North Carolina
38 people were injured and three fire fighters were treated for ammonia inhalation when a 130 cubic meter refrigeration system ruptured in the aftermath of an explosion.
The above incidents are only the ones that have been reported and I’d suggest that they are only a fraction of the total number of daily global accidental ammonia leaks.
Ammonia emissions produce environmental problems, from acid soil to biodiversity reductions and dust, which cause health problems such as asthma. Biomass burning creates ammonia and global ammonia emissions have more than doubled since pre-industrial times.
Exposure to high concentrations of ammonia can result in lung damage and death to humans, whilst ammonia in even dilute concentrations is highly toxic to aquatic animals.
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