HEATING BASKETS
Comparing to the human anatomy, heating baskets are the lungs of the boiler energy recovery system. During each rotation of the rotor, the stream of flue gas encounters a thousand square meters of heating surface in the form of close-fitting, specially profiled sheets, packed in packets called heating baskets that fill the segmented rotor. Heating baskets capture heat from the flue gas and transfer it to the air stream. All of this takes place in a continuous cycle, with the rotor speed ranging from 1 to 3 rpm.
Heating baskets are arranged in the rotor in two or more layers, to form layers of the hot end baskets (GK), and cold end baskets (ZK). ZK baskets operate at a lower temperature of gases, often have different material and basket filling profile than GK baskets, due to problems associated with increased corrosion and condensation of gases.
MATERIAL
The selection of appropriate basket parameters is crucial to ensure optimum heat transfer and obtaining a minimum pressure drop of the outlet gases.
Depending on economic factors and customer requirements we use various steel for baskets filling:
- DC01
Often used as a filling for GK baskets, due to low carbon content has a high capacity for forming and relatively low price. - Corten
Called “weathering steel”, with increased corrosion resistance, due to moisture on the surface, a rust-like protective coating appears by itself. For this reason, it is used mainly as a filling for ZK baskets.
In architecture, it is sometimes used to cover buildings in combination with glass or concrete gives them a brown, austere and modernist look. - Enamel coated steel
with a thin layer of hard enamel, a low surface adherence and high resistance (acids, sulphur, corrosion, temperature, steam). Used under particularly aggressive conditions. - Duplex
Steel characterized by high mechanical properties and good resistance to corrosion, superior hardness, and therefore resistance to abrasive wear. Disadvantage – limited application temperature: 250÷300°C.
FILLING PROFILE
Different profiles of perforated sheet metal in different combinations are used as a filling, in order to obtain the best thermal performance, while keeping the best parameters of the gas flow.
Most often we use FNC corrugated sheet metal for GK baskets, and a combination of corrugated and plain sheets for ZK baskets.
The FNC sheet provides high thermal efficiency and low pressure drops, while the combination of corrugated and plain sheet has lower thermal efficiency, but is more resistant to clogging by ash and is characterized by better gas flow parameters.