It is well known that fouling deposits on the wall of power generation units where solid fuels, like pulverized coal, is burnt cause significant reduction of the overall efficiency of the furnace and the boiler. In order to take fouling into account in the overall balance of the boiler it is necessary to measure two main parameters - thickness of the deposits and their reflectivity (emissivity) in the wavelength of visible and IR region. In the present paper an electro-optical system is described which enables to perform direct on-line measurement of these two parameters of heat transfer in the course of normal operation of the power unit. The system is capable to carry out measuring procedure inside the furnace chamber at temperatures up to 1800 C. Dynamic measurement of thickness of the fouling deposits created on the wall tubes is measured with accuracy of 0.1mm. Spectral reflectivity of the wall is also continuously measured and compared with the reflectivity of the stainless steel specimen located inside the system. Experimental results are reported obtained during three months operation of the system on the power unit of Israel Electric Company (power station in Hadera).
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