Boilers & Heat Recovery
The essence of successful CHP is the beneficial use of the heat produced as a by-product of generating electricity. This heat is contained in the exhaust gases from a prime mover, or in the cooling systems.
In the most straightforward cases, the heat from the prime mover is used directly, without conversion to steam or hot water. Examples include the use of exhaust gases for drying, or the use of hot water from cooling systems for heating purposes. However, the direct use of exhaust gases involves contact with the material to be heated, which may cause damage to the product, particularly where non-premium fuels are being used. Similarly, while engine cooling water can, in theory, be used directly in applications such as space heating, it is desirable in practice for the cooling circuits to be self-contained and to include additives to avoid scaling and corrosion. Heat from the engine cooling water is, therefore, transferred by heat exchangers to separate heating water circuits.
In the majority of CHP plants, it is effective heat recovery that is the essence of success. In most instances, some form of heat recovery equipment is needed to convert the heat generated by the prime mover into the form or forms required by the site, and to deliver it to the heat users. By far the most common heat recovery methods used are steam generation from gas turbine and engine exhaust gases, and water heating from medium- and low-grade heat sources, such as engine exhausts and cooling systems.
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