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Compressed air is a largely employed utility in industrial plants. It is also used for pneumatics switches of tools and machinery, and for measurement and control instruments. In Italy, 11% of total energy amount in manufacturing consumption is used in the air compressors sector, and in the lifecycle of a compressor, approximately ten years, energy consumption represents 73% of tco, and the percentage gets even higher for higher power equipments. A total of 75% of this energy used in air compressor stations gets wasted as heat generated by the machinery; this gives an idea of how many benefits it is possible to achieve by installing thermal systems and heat recovery equipment for cost and energy saving.
The right dissipation of heat loads generated by an air compressor station, along with fitting cooling solutions and air treatments in input and output on the engines, and thermal recovery and hydraulic oil cooling, can lead to high reductions on energy consumption and management costs, achieving the most suitable working conditions for the compressor engines with an appropriate thermal dissipation process of generated heat, increasing performances, affordability in a longer lifecycle, enhancing the overall industrial production. In addition, each energy-saving solution lowers the plant’s environmental impact: each kWh saved leads to a reduction of 500 gr in CO2 emissions.
An air compressor station needs appropriate cooling systems, especially in large plants. Depending on the amount and type of compressed air applications requested, compressed air production engines can vary in size, up to big and powerful compressed air stations, producing large amounts of process heat. Compressors are engines working on highly repetitive mechanical movements, generating heat and reaching high machinery temperatures, but generally cooling water is not requested to have very low temperatures: water at 30-40 degrees is usually enough feeding a compressed air station cooling system. Water cooling of compressed air machinery is so often achieved using evaporative towers, dissipators and dry coolers, or evaporative coolers with forced circuit.
An evaporative tower is a typical application in compressed air station cooling solutions. An evaporative tower cools down water to be used to carry away the heat generated by the compressors, used as a cooling agent on air compressor cylinders, or employed in heat exchangers. Heat exchangers can also have several applications, thermoregulating machinery and hydraulic oil temperatures, cooling air feeding the compressors, or also cooling air compressed coming from the process, functioning as a dryer for compressed gas treatment, extracting water vapour from air using a condensation process.
Heat exchangers are thermal machines used to cool down or warm up a fluid. Plate heat exchangers are a more efficient, cheaper and practical solution, being lighter, easier to install and easily customisable, and offer a higher thermal transfer rate.
Pumping stations complete the thermoregulating system in a compressed air station, ensuring the transfer and the recycle of cooling water among the different thermal machines, evaporative towers and heat exchangers.
Dryer systems are also a need for an air compressor station, essential to supply quality compressed air. It must be dehumidified not to damage instruments and equipments, with deposits leading to rust and corrosion on machinery and pneumatic tools. Compressed air can be treated with drying thermal machines, and heat exchangers are used as dryers, using right temperature gradients to obtain high drying levels. A heat exchanger can indeed be used to cool down compressed air temperature coming from the compressor: lowering air temperature is achieved by contact thermal transfer with the cold surface area of plates, with condensation process based on pressure dew point, extracting water from compressed air.
Cooling air used to lower machinery temperature in a compressor air station, that optimises affordability and performance, can be re-used for other purposes, using heat generated by the mechanical equipments for ambient warming, or recovered with heat exchangers or other thermal cycle-based machinery to produce hot water or employing it in other production processes. A heat recovery integrated system in the compressor cooling process can save up to 94% of energy dissipated by the engines.
It is then important not only to properly evaluate the compressed air needs of a production facility, but also to design and build a proper cooling system, employing thermal cycle machines to achieve thermoregulation of components, working fluids, suction air itself and compressed air in output, optimising plant performances, and the whole production process, but also reducing energy consumption and industrial process wastes.
Please contact Tempco for more information.
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