Simulation Research on Thermal Deviation in 700 °C Ultra-Supercritical Boiler

Abstract

Based on commercial CFD software, a 700 °C ultra-supercritical tangential boiler was simulated by the orthogonal test method, and the thermal deviation of flue gas at the furnace outlet section was used as the optimization index. Three horizontal optimization treatments are designed respectively for the air distribution mode of secondary air (factor A), the reverse tangent angle of the separate over-fire air (factor B), and the upper swing angle of the burner (factor C). The range analysis method, variance analysis method, and weight matrix analysis method are used to determine the factor and level combination of the best optimization effect and the weight of each factor. The research results show that the significance of the influence of each factor on the optimization index is: B > C > A (reverse tangent angle of the separate over-fire air > the upper swing angle of the burner > the secondary air distribution mode); the weight ratios of the three factors are: factor A is 0.080, factor B is 0.543, and factor C is 0.241; based on the three analysis methods, it is concluded that factor B has a highly significant impact on the optimization index, factor C has an impact on the optimization index, and factor A has no impact on the optimization index, and it is determined that the optimal factor and level combination of the orthogonal test is A1B3C3. Under this combination, the thermal deviation in the furnace is 1.349 K, and the problem of thermal deviation is basically eliminated, being 116.066 K lower than the highest thermal deviation of 117.415 K, which is very obvious.