Air heater profiles
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The equipment of most boiler units, used mainly in the heat power industry, includes a regenerative air heater, designed to heat the incoming air into the boiler due to the flue gases leaving it. In return, the main elements of the regenerative air heater are heat-exchange elements (or, as they are usually called, heat exchange profile), which are directly involved in the heat transfer process.
As a rule, the heat-exchange profile is installed in rotary cells of the regenerative rotating air heater (RAH) in the form of basketss, which are installed in several layers, usually two - "cold" and "hot" layers (depending on the design of the RAH, the number of layers may have been much higher). Each basket consists of a frame and alternating filling and spacing metal profiled sheets.
The filling sheets of the cold layer of the mass produced baskets of most manufacturers have an aerodynamically smooth straight surface. Although, spacing sheets have longitudinal corrugation, they also remain aerodynamically smooth.
Longitudinal filling channels formed by spacing and filling sheets, when assembling, form parallel autonomous channels that coincide with the direction of heat-transfer media.
The purpose of the different layers of air heater profiles
Hot and protective layers
With regard to high-ash fuel burning in the furnace of energy boilers, the concentration of ash in the gas-ash stream at the inlet into the baskets can be increased with a sufficiently significant fraction of abrasive components, such as SiO2, Al2O3, Fe2O3 and others, contributes to the high degree of fly ash erosion inlet of the gas-ash stream into the baskets.
Protective baskets layer can be installed in order to extend the service life of heat elements of the upper hot layer at the inlet of the gas-ash flow.
The essence of the application of the protective layer is that it provides a coaxial direction of the gas-ash flow at the inlet into the hot layer of the RAH. Elimination of the angular inlet of the gas ash stream into the hot layer reduces the degree of wear of the heat exchange surface of the inlet part of the hot layer and increases the service life of the inlet part of the hot layer, i.e. safe heat in the RAH at the initial level.
In the presence of blind ash erosion, the protective layer baskets can be replaced with new ones. It will eliminate the local abrasive wear of the corresponding baskets of the hot layer.
Thus, the baskets of the hot layer make it possible to provide a high degree of heat exchange and excludes the accumulation of slag fractions and ash inside the baskets of all layers.
Cold layer
The special baskets of the cold layer differs from the above described baskets in that the surface of the spacer sheets has inclined waves with respect to the direction of the longitudinal corrugation.
The complex reliable operation of the cold and hot layers with the corresponding surface parameters of the heat exchanger sheets creates the basis for reliable operation of the RAH.