The CellaCombustion PX 47 is a special pyrometer for non-contact temperature measurement of sooty flames in coal-fired power plants or waste incineration plants. The measurement and signal processing based on the quotient method detects the thermal radiation of the sooty particles of the flame in the near infrared range at two wavelengths. A special algorithm is used to correct the influences of the wavelength-dependent radiation properties of the soot particles and the optical flame density when determining the temperature. The flame temperature can be used to control the burnout during combustion in order to reduce pollutant emissions and minimize slagging of the combustion chamber walls.