Patent ID: 7229833

Claim:
A method for measuring the concentration of alkali metal chlorides in flue gases through a heat-producing plant of the kind comprising a first space for combustion of a fuel, a super-heater device placed in a second space located downstream of the combustion space, said superheater comprising tubes through which a medium such as water, air or steam, may pass in order to be heated by heat transfer from the flue gases formed during the combustion, and a chimney located downstream of said super-heater for letting out the flue gases from the plant, the method comprising the steps of: locating a UV-light emitter and a UV-light receiver in a region near said super-heater tubing in said second space; connecting a photo-spectrometer, in which the light is divided spectrally, to the UV-light receiver; calibrating the photo-spectrometer for registering the spectral intensity distribution of received UV-light within the wavelength range of 200 to 310 nanometers; detecting, in said second space and in immediate proximity of the super-heater tubing, the concentration of alkali metal chlorides in flue gases at temperatures ranging from 600° C. to 1400° C.; and controlling the combustion of the fuel in response to a detected concentration of said alkali metal chlorides in the flue gases, wherein the fuel combustion control comprises the step of feeding a metal chloride reducing material into the combustion space.