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Difference between revisions of "Air Dryers"
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[[File:Air Dryer.jpg|thumb|200px|Right|Air Dryer]] | [[File:Air Dryer.jpg|thumb|200px|Right|Air Dryer]] | ||
A compressed '''Air Dryer''' is a device for removing water vapor from compressed air. [[Compressed Air Dryers]] are commonly found in a wide range of industrial and commercial facilities. | |||
A compressed ''' | |||
The process of air compression concentrates atmospheric contaminants, including water vapor. This raises the dew point of the compressed air relative to free atmospheric air and leads to condensation within pipes as the compressed air cools downstream of the compressor. | The process of air compression concentrates atmospheric contaminants, including water vapor. This raises the dew point of the compressed air relative to free atmospheric air and leads to condensation within pipes as the compressed air cools downstream of the compressor. | ||
Excessive water in compressed air, in either the liquid or vapor phase, can cause a variety of operational problems for users of compressed air. These include freezing of outdoor air lines, corrosion in piping and equipment, malfunctioning of pneumatic process control instruments, fouling of processes and products, and more. | Excessive water in compressed air, in either the liquid or vapor phase, can cause a variety of operational problems for users of compressed air. These include freezing of outdoor air lines, corrosion in piping and equipment, malfunctioning of pneumatic process control instruments, fouling of processes and products, and more. | ||
There are various types of compressed air dryers. Their performance characteristics are typically defined by the dew point. | There are various types of compressed air dryers. Their performance characteristics are typically defined by the dew point. | ||
* Regenerative | * [[Regenerative Desiccant Dryers]], often called [[Regens]] or [[Twin Tower Dryers]] | ||
* Refrigerated | * [[Refrigerated Dryers]] | ||
* Deliquescent | * [[Deliquescent Dryers]] | ||
* Membrane | * [[Membrane Dryers]] | ||
Water vapor is removed from compressed air to prevent condensation from occurring and to prevent moisture from interfering in sensitive industrial processes. | Water vapor is removed from compressed air to prevent condensation from occurring and to prevent moisture from interfering in sensitive industrial processes. | ||
==Characteristics== | ==Characteristics== | ||
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* A deliquescent dryer delivers a dew point suppression that fluctuates with air temperature. Typically this suppression is 20 °F | * A deliquescent dryer delivers a dew point suppression that fluctuates with air temperature. Typically this suppression is 20 °F | ||
:below the compressed air temperature. | :below the compressed air temperature. | ||
==Refrigerated dryer== | ==Refrigerated dryer== | ||
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Some manufacturers are marketing compressors with built-in refrigeration dryers, but these have had a mixed acceptance in the market. | Some manufacturers are marketing compressors with built-in refrigeration dryers, but these have had a mixed acceptance in the market. | ||
Commonly a coalesing prefilter is installed immediately upstream of a refrigerated dryer to remove lubricating oil and other contaminants that have the potential to foul the dryer's heat exchangers. | Commonly a coalesing prefilter is installed immediately upstream of a refrigerated dryer to remove lubricating oil and other contaminants that have the potential to foul the dryer's heat exchangers. | ||
==Deliquescent dryer== | ==Deliquescent dryer== | ||
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Deliquescent dryers have no moving parts and don't require electrical power for operation. Common applications therefore often involve remote, hazardous, or mobile worksites. Deliquescent dryers are used for removing water vapor from compressed air, natural gas, and waste gases such as landfill gas and digester gas. | Deliquescent dryers have no moving parts and don't require electrical power for operation. Common applications therefore often involve remote, hazardous, or mobile worksites. Deliquescent dryers are used for removing water vapor from compressed air, natural gas, and waste gases such as landfill gas and digester gas. | ||
The performance of a deliquescent dryer, as measured by outlet dew point, is highly dependent on the temperature of the air or gas being processed, with cooler temperatures resulting in better performance. | The performance of a deliquescent dryer, as measured by outlet dew point, is highly dependent on the temperature of the air or gas being processed, with cooler temperatures resulting in better performance. | ||
==Desiccant dryer== | ==Desiccant dryer== | ||
The term | The term [[Desiccant Dryers]] refers to a broad class of dryers. Other terms commonly used are regenerative dryer and twin tower dryer, and to a lesser extent [[Absorption Dryers]]. | ||
The compressed air is passed through a pressure vessel filled with an absorbent media such as activated alumina, silica gel, molecular sieve or other desiccant material. The desiccant can bring the dew point of the water vapor in the air down to −40 °C (−40 °F) or below. This means that the air will not condense (deposition) water until it is cooled to −40 °C (−40 °F). In practice, two cylinders with desiccant are used; one is drying the air, while the other vessel is being regenerated. The switching of the vessels and the regeneration sequence is typically done automatically via solenoid operated valves. | The compressed air is passed through a pressure vessel filled with an absorbent media such as activated alumina, silica gel, molecular sieve or other desiccant material. The desiccant can bring the dew point of the water vapor in the air down to −40 °C (−40 °F) or below. This means that the air will not condense (deposition) water until it is cooled to −40 °C (−40 °F). In practice, two cylinders with desiccant are used; one is drying the air, while the other vessel is being regenerated. The switching of the vessels and the regeneration sequence is typically done automatically via solenoid operated valves. | ||
The regeneration of the desiccant vessel can be during three different methods: | The regeneration of the desiccant vessel can be during three different methods: | ||
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* Heated dryer, which uses a hot air blower, so there is no loss of compressed air. | * Heated dryer, which uses a hot air blower, so there is no loss of compressed air. | ||
* Heat of compression, which can only be used with an oil free compressor. | * Heat of compression, which can only be used with an oil free compressor. | ||
==Membrane dryer== | ==Membrane dryer== | ||
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Dew point suppression is not a feature of refrigerated dryers, as they chill the incoming air to a fixed temperature, usually 35 °F. So a lower dew point challenge will not yield a dew point lower than 35 °F. | Dew point suppression is not a feature of refrigerated dryers, as they chill the incoming air to a fixed temperature, usually 35 °F. So a lower dew point challenge will not yield a dew point lower than 35 °F. | ||
Membrane air dryers are used in pneumatic components, spray painting, laser plenum purge, air bearings, air spindles, medical equipment, air guns and pneumatic brakes for vehicles and trains. | Membrane air dryers are used in pneumatic components, spray painting, laser plenum purge, air bearings, air spindles, medical equipment, air guns and pneumatic brakes for vehicles and trains. | ||
==Usage== | ==Usage== | ||
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:* Feed air for Zeolite type Oxygen and Nitrogen generators | :* Feed air for Zeolite type Oxygen and Nitrogen generators | ||
* Truck and Train Air brake systems. | * Truck and Train Air brake systems. | ||
==Video== | ==Video== | ||
<youtube>QKBnamODCb8</youtube> | <youtube>QKBnamODCb8</youtube> | ||
<youtube>gUUYYyF2wyg</youtube> | <youtube>gUUYYyF2wyg</youtube> | ||