A simple measurement method of temperature and emissivity of coal-fired flames from visible radiation image and its application in a CFB boiler furnace

The two-color method is widely used in non-contact temperature measurement of combustion flames from radiation images, traditionally based on the spectroscopic characteristics of the image sensor, and/or the representative wavelengths for the red, green and blue filters of the image-forming devices, for example, Charge Coupled Device (CCD) cameras. In this paper, a new method to derive the temperature and emissivity images from a color CCD image is presented for coal-fired combustion processes, which is independent of the spectroscopic characteristics and the representative wavelengths of the CCD and the image processing system. In this method, it is only necessary to capture image information by the image processing system from a blackbody furnace at different temperatures which cover the possible temperature range of the combustion processes to be measured. In a 480 ton/h coal-fired circulating fluidized bed (CFB) boiler experiments are conducted. The temperature measured by this method is validated by that obtained by thermocouple, and it varies obviously with the load the boiler. The flame emissivity provided by this system is worthy for further study.