Measurement of thermal deviation of flue-gas in crossover pass of single tangential boiler

Abstract

Aiming at the problem of thermal deviation in crossover pass of single tangential boiler, an on-line measurement method of radiation parameters of high temperature coal particles based on radiation spectroscopy was proposed. A measurement system consisting of an optical fiber spectrometer system and a water-cooled structure probe was developed, which was used to measure the radiation parameters of high temperature coal particles in crossover pass of the boiler. The radiation spectra at 500–1000 nm band on the gas flow side of the final reheaters inlet section of a 660 MW ultra-supercritical boiler were measured by the system. According to Planck’s law, the distribution of coal particles temperature, emissivity and other parameters along the section was obtained by fitting parameter method. The results show that the burnout delay of pulverized coal particles caused by the air-stage combustion system and the radiant heat transfer deviation caused by the non-uniform concentration of coal particles are the main causes of the thermal deviation of the final reheaters. Under the condition of increasing yaw angle of SOFA nozzles, the ability of SOFA to alleviate the residual swirling flow is significant, and the temperature distribution of coal particles in the crossover pass is more uniform. However, due to the phenomenon of single-side particles accumulation still exists, the deviation of particles radiation intensity remains large, which cannot effectively reduce the steam temperature deviation in reheaters. Through differentially adjusting the angles of SOFA nozzles in vertical direction and horizontal direction, the phenomenon of single-side coal particles accumulation can be improved, the non-uniform radiation heat transfer of heat exchangers on both sides can be balanced, and the steam temperature deviation in final reheaters can be reduced.