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

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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

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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…