When ash, slag and combustion residues, also referred to below as “hot material”, are transported away, it is of particular importance, firstly, to solidify or cure the hot materials, which are still partially in melt form, in a specific manner by cooling such that, in particular, the materials can be conveyed or further processed after being extracted from the combustion boiler. Furthermore, it is also desirable to use the energy still found in the hot material and therefore to improve the overall efficiency of the combustion plant or of the combustion boiler.
It was initially assumed that quenching in a water bath was necessary for conveying the hot materials (“wet discharging”). However, this required large quantities of water which were not readily available in particular in dry regions. In addition, the water used had to be expensively cleaned. Therefore, a transition has been made since the 1990s to “dry extraction systems”. In this case, the hot material is placed onto conveyor belts where it is transported further, with specific cooling of the hot material being carried out on the conveyor belt. The conveyor belts are generally designed so as to be encapsulated in relation to the outer environment, i.e. have a housing which prevents combustion gases which are still being produced during the treatment of the material from being able easily to escape into the environment. In addition, the combustion boilers are operated at a negative pressure such that a gas flow enters the housing through a gas inlet or a material outlet of the housing, where it is extracted by corresponding suction counter to a conveying direction of the hot material towards the combustion boiler, with the hot material being cooled in the process by the gas flow.