Today Gas, Electricity, Water and Compressed air is a common utility in most industrial and process plants. Typically, pneumatics consumes 10 to 15% of a plant's electrical energy, according to most experts. The big difference is that while the other utilities are purchased, compressed air must be generated in-house. This puts the burden on the user to ensure that the compressed air quality is suitable for plant operations.
Compressors produce high pressure air that is hot, wet, and dirty for e.g. the ambient air in an Air Compressor room may contain water and particles up to 1 mg/m3 of oil; a compressed air in this state cannot be used. If not removed, liquid water in an air system leads to a lot of different problems such as:
- Water rusts and corrodes piping and other metal components.
- Air tools often run on lubricated air. Water leaches out additives in the lubricant and accelerates tool wear.
- Water can destroy positive-displacement, rotary-vane air tools because they are not designed to operate with incompressible fluids.
- Air lines that run outdoors can freeze, shutting down an operation or even an entire plant.
- In paint booths, water in air lines causes blisters, bubbles, poor adhesion, and corrosion. Electrostatic painting processes are sensitive to moisture as well.
- Wet air can affect the quality of moisture sensitive chemicals and processes, from manufacturing pharmaceuticals to transporting powdered concrete.
- Scale, bacteria, rust and water will begin to form in the compressed air piping,
To avoid possible damage to the compressor and equipment using compressed air and make sure the air quality satisfies the quality standards required, proper drying and filtration of the compressed air is essential.
Compressed air drying is the most elementary key component of compressed air treatment. The important task of compressed air drying is to reduce the amount of moisture contained in the compressed air down to a defined residual value. At the outlet of the compressor there is, compared to the sum of all other contaminants, 1000-times more moisture – 100% saturated – which means even the slightest temperature reduction of the compressed air on its way to the application causes a condensation of liquid water, forming condensate within the compressed air.
Compressed air dryers eliminate the moisture and thus produce dry, non-saturated compressed air where no further condensation can occur – either within the compressed air system or at the point of use.
Refrigeration dryer
Compressed air drying down to pressure dew-points of 3°C
for every range of volume flow
• Maximum volume flow 20 m³/h – 11,460 m³/h
• Maximum operating pressure 14 bar - 16 ba
Adsorption dryer
Compressed air drying down to pressure dew-points of -70°C
for every range of operating pressure and volume flow
• Maximum volume flow 8 m³/h – 14.700 m³/h
• operating pressure 11 bar - 350 bar
Important Notes:
The inlet and ambient temperature is also crucial for a dryer’s performance.
Dryer capacity decreases dramatically with higher inlet/ambient temperatures.
Regarding Compressed Air Dryers As adsorption and refrigeration dryers are designed to
remove only water vapor and not water in a liquid form, they require the use of:
- Water Separators
- Condensate drainss
Now days with usage expansion of compressed air in Medical facilities, Hospitals and Food & beverages industries, High quality compressed air is becoming more & more critical. For that reason higher levels of filtration are becoming more common to prevent compressed air contamination.
In normal processes contamination originates from:
• Contaminants in the surrounding ambient are drawn into the air system through the intake of the air compressor. Ingested contaminants appear in the form of water vapor, hydrocarbon vapors, natural particles and airborne particulates.
• As result of the mechanical compression process, additional impurities may be introduced into the air system. Generated contaminants include compressor lubricant, wear particles and vaporized lubricant.
• A compressed air system will contain in-built contamination. Piping distribution and air storage tanks, more prevalent in older systems, will have contaminant in the form of rust, pipe scale, mineral deposits and bacteria.
To prevent and remove each type of contaminations new purification technologies have become available:
Coalescing Filters:Coalescing filters are probably the most important items of purification equipment in any compressed air system. They are designed to remove oil and water aerosols using mechanical filtration techniques and have the additional benefit of removing solid particulate to very low levels (as small as 0.01micron in size).
Installed in pairs, most users believe one to be an oil removal filter and the other to be a particulate filter, when in fact the pair of filters both performs the same function. The first filter, a general purpose filter is used to protect the high efficiency filter against bulk contamination. This ‘dual filter’ installation ensures a continuous supply of high quality compressed air with low operational costs and minimal maintenance time.
Water Separators: Used to protect coalescing filters in systems where excessive cooling takes place in distribution piping. Water Separators will remove in excess of 90% of bulk liquid contamination.
Oil vapor is simply oil in a gaseous form and as with water vapor will pass through a coalescing filter just as easily as the compressed air itself. Therefore, oil vapor removal filters must be employed as these provide a large bed of activated carbon adsorbent for the effective removal of oil vapor, providing the ultimate protection against oil contamination.
Dust Removal Filters : Dust removal filters are used for the retention of particulates when no liquid is present. They usually provide identical particulate removal performance to the equivalent coalescing filter and use the same mechanical filtration techniques to provide up to 99.9999% particle removal efficiency. For absolute particulate retention (100% at a given size), a sieve retention membrane filter must be used.
Micro-Biological (Sterile) Filters : Absolute removal of solid particulates and micro-organisms is performed by a sieve retention or membrane filter. They are often referred to as sterile air filters as they also provide sterilized compressed air. Housings are manufactured from stainless steel to allow steam sterilization of the filter and element. It is important to note that the piping between the sterile filter and the application must also be cleaned and sterilized on a regular basis.
