Measurement of the temperature depending spectral emissivity of ashes and deposits under Oxy-Fuel conditions

The aim of this project is the measurement of the surface emissivity of synthetic ashes and deposits under Oxy-Fuel conditions. The synthetic samples will contain the typical mineral phases or ashes and deposits which are present on heat transfer surfaces. The quantitative influence of the chemical-mineralogical composition will be investigated. Especially, the influence of mineral phases which might form preferably under Oxy-Fuel conditions (carbonates) will be examined. Furthermore, the correlation between surface structure and optical properties is in the scope of investigations. Starting with well-defined micro-structured surfaces, the measurements are extended to powders and sintered powders. The goal is to define a critical particle-size which indicates the transition from chemical-mineralogical to particle size dominated emission behavior.

The measurements are carried out in a reactor where plane samples can be heated up to a specific temperature under a well-defined Oxy-Fuel atmosphere. Sample radiation is compared with the radiation of a reference black body radiator to derive emittances. A FTIR-spectrometer is used to determine the thermal radiation as a function of the wavelength in the range from 0.68 µm to 28.5 µm. Sample temperatures are varied between 500 °C and 1100 °C. From these measurements, the spectral normal emittances and the total emittances are calculated.

The project ended after the 1st funding period.