Basic compressed air
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Transcript of Basic compressed air
Product Line Training
Product Line - Industrial Filtration Technology
Status: July 2010
01 Basics of Compressed Air C - Generation & Pollution
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Content
• Functionality• Type of contruction• Atmospheric Pollution• System Pollution
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Functionality
Compressors are similar to pumps: both increase the pressure on a fluid and both can transport the fluid through a pipe. As gases are compressible, the compressor also
reduces the volume of a gas. Liquids are relatively incompressible, so the main action of a pump is to pressurize and transport liquids.
A compressor is a mechanical device that increases the pressure of a gas by reducing its volume.
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Functionality
SO2
NH3
COCO2
O3
VOCNOX
H2OParticle
s
SO2
NH3
COCO2
O3VOC
NOX
CO2
NH3
NOX
VOC
VOC
Compressed Air
Compressor
Atmospheric Pressure ≈ 1 bar Compressed Air Pressure ≈ 7 bar
Atmospheric Air
Compressor
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Content
• Functionality• Compressor Types• Atmospheric Pollution• System Pollution
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Compressor Types
Positive Displacement Dynamic
Reciprocating Rotary
Lobe
Liquid Ring
Screw
Vane
Scroll
Single-Acting
Diaphragm
Double-Acting
Centrifugal Axial
Compressor TypesOverview
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Compressor Types
Dynamic
Centrifugal Axial
Compressor TypesDynamic Compressors
Dynamic compressor depends on a rotating impeller to compress the air. In order to do this efficiently, centrifugal compressors must rotate at higher speeds than the other types of compressors. These types of compressors are designed for higher capacity because flow through the compressor is continuous and oil free by design.
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Compressor Types
Compressor Types
Positive Displacement
Rotary
Lobe
Liquid Ring
Screw
Vane
Scroll
Rotary Compressor
Rotary air compressors are positive displacement compressors. The most common rotary air compressor is the single stage helical or spiral lobe oil flooded screw air compressor, consisting of two rotors within a casing where the rotors compress the air internally. There are no valves. These units are basically oil cooled with the oil sealing the internal clearances. Since the cooling takes place right inside the compressor, the working parts never experience extreme operating temperatures making them continious duty compressors.
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Compressor TypesScrew Compressor
Ca. 50% of all compressors are screw compressors.
Existence of two spindle-shaped rotors (screws) which attack each other.
Oil-free or Oil lubricated.
Functionality1. phase: The air enters through the opening in the
compressor housing.
2. phase: The compressor chamber is closed by the rotation.
3. phase: By reduction of the space, the air is compressed
4. phase: The compressed air enters.
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Compressor TypesScrew Compressor – Oil lubricated
In case of oil lubricated compressors one part of the oil, determined by the heat and the mechanical pressure is converted into steam. Besides the steam, aerosol consisting of fine droplets and oil in liquid form is released into the air.
Production of normal air quality residual oil content about 3 mg / m³
Screw Compressor – Oil freeOil-free screw compressors are called dry running, in which the compression chamber is not lubricated and run the screws couples without contact. Highest precision in manufacturing and production make this compression principle for optimal efficiency. Can be effective over seals to ensure that no oil entering the compression chamber and contaminate the air.
A) Dry Compressors:• Production of high pressure air quality
• Residual oil content <0.002 mg / m³• Max. pressure of 1-stage: 3.5 bar• Max. pressure of 2-stage: 10 bar
B) Water sprayed Compressors:• Production of high pressure air quality• Residual oil content <0.002 mg / m³• Max. pressure of 1-stage: 13 bar
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Compressor TypesPressure range
Screw Compressor
Fluid cooled Dry running
Water Oil
Single-stage Single-stage Single-stage Single-stage Single-stage
Up to 13 barUp to 160 KW
Up to 14 barUp to 600 KW
Up to 20 barUp to 200 KW
Up to 3,5 barUp to 500 KW
Up to 10 barUp to 1000 KW
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Compressor TypesScroll Compressor
Functionality
Consisting of a suction chamber, a pressure chamber, a stationary and a rotating screw.
Final pressure max. 8bar
As between the scroll compressor elements, there is no metal contact, no lubrication of the compression space is needed.
Intake air passes through the suction in the suction chamber
The rotating screw seals off the suction chamber and pushes the air into the increasingly small pressure chamber.
The generated compressed air leaves the compressor via an outlet opening in the center of the screw.
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Compressor Types
Compressor Types
Positive Displacement
Reciprocating
Single-Acting
Diaphragm
Double-Acting
Reciprocating
Reciprocating air compressors are positive displacement machines. This means that they increase the pressure of the air by reducing its volume, this is accomplished by a piston moving up a cylinder compressing the air above it. Single-stage and two-stage reciprocating compressors are commercially available. Single-stage compressors are generally used for pressures in the range of 70 psi to 150 psi. Two-stage compressors are generally used for higher pressures.
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Compressor TypesReciprocating
Existence of a crankcase, crankshaft, connecting rod, cylinder, piston, suction and pressure valve.
Oil-free or Oil lubricated
Oil-free compressors operate completely without oil. Bearings are greasedand encapsulated.
1-2-and multi stage compressor available
single-stage double-stage
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Content
• Functionality• Compressor Types• Atmospheric Pollution• System Pollution
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Nitrogen78%
Oxygen21%
Other gases1%
Ambient air does not only consist of….
You will also find…
Atmospheric PollutionWhy is air filtration and treatment needed?
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Atmospheric Pollution….Pollution!
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0,01 0,1 10 1001 10000,001
Viruses
Particle Size [ µm ]
Vapour, fumes, smoke Dust Mist Spray
10000
Droplets, Grains
Bacteria Drifting Sand
Gas Molecules Flour
Grains of Salt Pollen
Dried Milk Spores
Pigments Human Hair
Soot Cement Dust
Tobacco Smoke Coal Dust
Oil / Vapour Water Clouds
Perceptible under microscope Visually PerceptibleSubmicroscopic Perceptible
Atmospheric PollutionAerosols and Solid Particles
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Pollution Typical concentration range Main source
Carbon dioxide (CO2) 600…2000 mg/m³
Internal combustion engines and combustion processes in
industry and energy production plants
Carbon monoxide (CO) 1…50 mg/m³
Nitrogen oxide(NOX – NO, NO2)
0,01…0,08 mg/m³
Sulphur oxide(SO2)
0,002…0,01 mg/m³
Ammonia(NH3)
0,02…0,05 mg/m³ Agriculture, biogas
Ozone(O3)
0,03…0,1 mg/m³Develops from precursors like NOX or NMVOC (non-methane volatile
organic compouns) through photochemical processes
Atmospheric PollutionGaseous Components
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Pollution Typical concentration range Main source
VOC (Volatile organic
compounds)4…14 mg/m³ Several industrial processes,
vapour from solvents
Total emissions of
NMVOC (non-methane volatile organic compouns)
in the European Union per country
Atmospheric PollutionGaseous Components
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Atmospheric PollutionWater Vapor in Atmospheric Air
Atmospheric air always contains a certain amount of water vapor
Fog/mist = mass of fine droplets of water in the atmosphere near or in contact with the earth
Water vapor is always invisible – do not mistake vapor for fog or mist!
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Atmospheric air is a composition of several gases + water vapor.
Percentage portion of each component depends e.g. on the water vapor content
Water vapour content at
25°C70% R.H
Atmospheric PollutionWater Vapor in Atmospheric Air
23
Atmospheric PollutionOil – How does the oil get into compressed air?
One part of the oil, determined by the heat and the mechanical pressure is converted into steam. Besides the steam, aerosol consisting of fine droplets and oil in liquid form is released into the air.
Oil injected screw compressor
For 360m³/h (100 l/s)Compressor (37kW)
=> ± 8 l/s oil
Oil carry over± 3mg/m³
Intake air
Compressed air + oil
Compressed air 70 to 100ºC
Compressed air ambient +10ºC
OilCondensate
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Atmospheric PollutionOil – Types of oil content
Lubricated air compressors introduce three forms of oil contaminant into the compressed air stream: aerosol droplets, vapor and liquid wall flow. By contrast, oil-free compressors introduce no oil
contaminants whatsoever
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Atmospheric PollutionOil – How oil free is the air from oil free compressors?
Ambient air aspirated by a compressor already contains some hydrocarbons. The concentration will strongly vary based on the location but the following averages could be representative
Average (mg/m3) ISO oil class *
Rural < 0.001 1 (0)
Sub urban 0.01 1
Light industrial 0.01-0.03 1-2
City 0.01-0.10 2
Industrial area with major hydrocarbon industry 0.1-0.2 2-3
* At the outlet of an oil free compressor it can be estimated that the quality is one class better than those listed above, since the compressor coolers (after the 1st and 2nd stage), dryer and air receiver will also
wash out some of these ambient vapours and aerosols and remove them with the condensate.
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Content
• Functionality• Type of contruction• Atmospheric Pollution• System Pollution
27
SO2
NH3
COCO2
O3
VOCNOX
H2OParticle
s
SO2
NH3
COCO2
O3VOC
NOX
CO2
NH3
NOX
VOC
VOC
Compressed Air
Compressor
Atmospheric Concentration 8 x Atmospheric Concentration
+ H2OAgglomerationAcids + Bases
Bacteria
Atmospheric Air
System PollutionPollution in Compressed Air Systems
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Corrosion + contamination Material Damage Production downtime High maintenance cost High operating cost (Δp) Production of scrap Invest in new equipment
required
System PollutionWithout Filtration + Treatment…