THERMAL AND RADIATIVE PROPERTIES OF ASH DEPOSITS ON HEAT TRANSFER SURFACES OF BOILERS

摘要

A review of thermal and radiative properties of ash deposits formed on heat transfer surfaces of the coal- and oil-fired boilers is given in the paper. It is shown that the spectral emissivity, total emissivity, total absorptivity and the effective thermal conductivity of the deposits are greatly influenced by the type of fuel, the way of fuel combustion, the flue gases flow and thermal conditions maintained in the boiler. The radiative properties of deposits seem to depend mostly on the chemical composition and granularity of the ash while thermal properties are primarily influenced by the microstructure of deposits. The ash deposits coming from Polish coal-fired boilers have similar properties to those cited in literature and of another origin. Prediction of radiative and thermal properties of ash deposits seems possible. However, detailed information on ash deposition, its chemical composition and conditions occurring in the boiler during boiler operation is necessary.