Compressed air – the fourth utility
A gas compressor is a mechanical compressed air are pneumatic tools, The major cooling applications for device that converts power into kinetic energy storage, production lines, compressors where heat exchangers energy by increasing the pressure of automated assembly stations, are used are: gas and reducing its volume. refrigeration, gas dusters and air-start • Air cooling systems. • Oil cooling Compressed air has become one of • Water cooling the most important power media used Another important power media is • Heat recovery in industry providing power for a compressed natural gas (CNG), which multitude of manufacturing operations. is made by compressing natural gas to In industry, compressed air is so widely less than 1% of the volume it occupies used that it is often regarded as the at standard atmospheric pressure. fourth utility, after electricity, natural gas CNG is generally used in traditional and water. General uses of combustion engines. Oil-free
Compressor
Oil
Air
Water
Air cooling The compressed gas from the Oil cooling A multi-stage compressor can contain compressor is hot after compression, Both lubricated and oil-free one or several intercoolers. Since often 70-200°C. An aftercooler is used compressors need oil cooling. In compression generates heat, the to lower the temperature, which also oil-free compressors it is the lubrication compressed gas needs to be cooled results in condensation. The aftercooler oil for the gearbox that has to be between stages, making the is placed directly after the compressor cooled. In oil-injected compressors it is compression less adiabatic and more in order to precipitate the main part of the oil which is mixed with the isothermal. The inter-stage coolers the condensate as quickly as possible compressed air for lubrication, sealing typically result in some partial that would otherwise follow out into the and cooling that has to be cooled. condensation that is removed in vapor- system. The aftercooler is generally liquid separators. fitted with a vapor-liquid separator with automatic drainage. Oil-injected
Compressor
Oil
Air
Water
Water cooling concentrated in the decreasing volume For compressor cooling A water cooler is generally used, direct and the excess is led off before the Alfa Laval offers: or indirect, to cool the closed loop gas leaves the compressor. The cooling water to the air/gas and oil energy used to produce compressed Air cooling coolers. Since this is typically an air or gas typically represents 80% • AlfaNova fusion-bonded plate heat outdoor installed air heat exchanger, of the total cost. Over 90% of the exchangers the water is mixed with anti-freeze energy supplied to the compressor • Copper brazed plate heat such as glycol. This is a common can be recovered. exchangers cooling method for CNG compressors. • Gasketed plate heat exchangers Air heat exchangers are particularly For water cooled compressors, the suitable when the availability of water is cooling water from the compressor can Oil cooling limited or as an alternative to cooling supplement a hot water flow. If the • Copper brazed plate heat towers. As air heat exchangers have a water is used for e.g., washing, exchangers closed cooling water loop – make-up cleaning or showers, a normal hot • Gasketed plate heat exchangers water, water contamination and water boiler is still required. However, chemicals to prevent algae can be the recovered heat is a supplement Water cooling avoided. that can reduce the load on the boiler. • AlfaBlue air heat exchangers This saves fuel and can possibly result Heat recovery in the use of a smaller boiler. Heat recovery When a gas is compressed heat is • Copper brazed plate heat emitted. The thermal energy is exchangers • Gasketed plate heat exchangers