Method and apparatus for monitoring the formation of deposits in furnaces
Method and apparatus for monitoring formation of deposits of solid particles from flue gas onto furnace walls formed of welded-together tubes through which cooling medium flows. For the entire surface of the walls, the exact surface temperature is detected with infrared cameras, offset by 90° relative to one another, via a thermal image obtained of a surface development of the furnace. This exact surface temperature is compared with the temperature of the cooling medium from measurement locations. Individual images from the cameras are composed to form an overall development of the inner surface of the furnace walls. The coordinates of the deposits on the walls are determined from the overall development, and the thickness of the deposits is determined from the temperature comparison.
1. A method of monitoring formation of deposits caused by depositions of solid particles from a hot, dust-laden flue gas onto walls of a rectangular furnace of a boiler, wherein said walls are formed of tubes that are tightly welded together and through which a cooling medium flows, said method including the steps of:
providing two infrared cameras that are offset by 90° relative to one another;
detecting, over the entire surface of said walls of said furnace, the exact surface temperature with said infrared cameras via a thermal image obtained of a surface development of said furnace;
comparing the detected exact surface temperature with the temperature of the cooling medium known at respective measurement locations, taking into consideration the thickness and the thermal conductivity of said tubes of said walls of said furnace;
comparing individual images taken by each of said infrared cameras to form an overall development of said walls of the inner surface of said furnace;
determining the coordinates of said deposits on said walls from said overall development; and
determining the thickness of said deposits on said walls from the temperature comparison.
2. A method according to claim 1 , wherein said coordinates and said thickness of said deposits on said walls are conveyed to a cleaning system for a precise and intensive removal of said deposits.
3. A method according to claim 1 , wherein a radiation influence of the solid particles contained in the flue gas is determined and eliminated with a mathematical/physical radiation model and the determined parameters for each image point.
4. A method according to claim 1 , wherein a heat-flux density that strikes each point of said walls of said furnace is determined.
5. A method according to claim 1 , wherein said step of detecting the exact surface temperature is carried out in the middle infrared range of 3.0 to 5.0 μm.
6. A method according to claim 5 , wherein said step of detecting the exact surface temperature is carried out at a wavelength of 3.9 μm.
7. An apparatus for carrying out the method of claim 1 , comprising:
at least one of said infrared cameras in each of two adjacent walls of said rectangular furnace;
wherein each infrared camera is rotatable in a stepwise manner by 360° about its longitudinal axis and is provided with an oblique objective lens;
wherein each of said infrared cameras has a predetermined rake angle of said oblique objective lens in conjunction with the angle of image of said infrared camera; and
wherein each of said infrared cameras detects the entire width of a wall of said furnace for an image composition, image processing and image evaluation.
8. An apparatus according to claim 7 , wherein said infrared cameras are disposed in the walls of said furnace offset by 90° relative to one another.