The term heat recovery describes the recuperation of thermal energy – usually heat – from preceding production processes. The heat is a waste product which is released untreated outside with strong negative effects on the environment without using a heat recovery system.
During the production process, thermal energy can be generated in various ways, for example through pressure, friction or the heating of raw materials, water or air. This shows: thermal energy is always bound to a medium. Common carrier media are, for example, the process exhaust air or the cooling water. Heat recovery systems are used to recover the bound thermal energy. Such systems usually consist of a heat exchanger and an additional heat pump, in case of low exhaust air temperatures.
Both systems – heat exchanger and heat pump – are based on the transfer of heat from one medium to another. These two media are usually air, gas or a thermally conductive liquid. One medium, the so-called carrier medium, is located in the recuperation system. Inside this recuperation system the carrier medium flows through specially arranged pipes. The second medium, containing the thermal energy, e.g. the process exhaust air, then flows through the heat exchanger or heat pump through this pipelines. During this process the thermal energy of the exhaust air is transferred to the carrier medium. Is the heat bound inside the carrier medium, it can be used to heat fresh air or process water.
Heat recovery makes a significant contribution to the energy efficiency of production plants. Especially in energy-intensive industries such as metal and food processing or textile finishing, process waste heat is a valuable resource. Heat recovery reduces the consumption of fossil fuels greatly, which in turn means a large potential for cost and energy reduction. Furthermore, effective heat recovery also means reducing the ecological footprint and improve the company’slife cycle assessment.
To prevent the risk of fire due to deflagration or ignition of exhaust air gases, heat recovery systems are always connected to an exhaust air purification system. This way only purified process exhaust air enters the heat recovery systems. The preceding purification of the exhaust air stream also contributes to the longevity of both heat exchanger and heat pump, as any accumulations of impurities and deposits are avoided.