| Selective Catalytic Reduction (SCR) has become the mainstream flue gas denitrification technology of the coal-fired power plant because of its high denitrification efficiency. In the temperature of 420-493K, the ammonium bisulfate (NH4HSO4) escapes from the SCR system is a strong adhesive liquid, sticking on the medium and low temperature area of the rotary air preheater, and glue the particles in flue gas, leading to deposition, this may affect the safety and economy of the coal-fired power plant. This kind of deposition differs from the traditional slag, fouling and loose deposition a lot because of the strong stickiness of the liquid NH4HSO4. However, currently, the numerical computation method of loose deposition is still employed to calculate this kind of deposition, thus the accuracy and reliability of the calculation results remained to be improved. Employing mathematic models fits to depict the deposition with stickness NH4HSO4 deposition, and predict the deposition characteristics of rotary air preheater after SCR denitrification reform is of important theoretical significance as well as application value.Firstly, appropriate particle tracking model, visco-elastic model to descibe the collision between particles and regenerator, contact mechanism, sticking criterion has been adopted to build the complete deposition model, by which different manage method has been employed to distinct the deposition with or without liquid stickiness NH4HSO4 adhesion. This model has been validated, and can effectively simulate the deposition of the regenerator in rotary air preheater after SCR reform.Secondly, deposition simulation of a rotary air preheater in a 300MW coal-fired power unit after SCR denitrification reform has been modeled in a flue gas period. Deposition characteristic parameters such as deposition intensity, deposition thickness, the deposition particle size distribution, nomal impact velocity, nomal impact angle, deposition efficiency as well as the differentia of the deposition characteristics between the normal area and area with adhesion of NH4HSO4 were analyzed. The results show that:The deposition intensity in the NH4HSO4 adhesion area is about 7-8 times of this in the deposition area without NH4HSO4 adhesion, and the deposition probability in the area with adhesion of NH4HSO4 is around 90% while this value is lower than 31%, and decreases as the particle diameter grows in the area without NH4HSO4 deposition; Deposition intensity of the upwall is 2 times of that in the lowwall, and the nomal impact velocity as well as angle in the upwall is notablely larger than these values in the lowwall; The distribution of deposition thickness agrees well with that of deposition intensity.Finally, the influence of operating parameter like particle flux, particle size, flue gas temperature, flue gas velocity and air temperature to the deposition process as well as deposition characteristics has been considered and discussed. The results show that:Deposition intensity and thickness in the area with or without adhesion of stickiness NH4HSO4 increases significantly as the particle flux increases; The particle distribution of the inlet particles can directly determine that of the deposition particles; The variation of the inlet flue gas temperature can result in position modification of NH4HSO4 adhesion area, as the flue gas temperature increases 10K, NH4HSO4 deposition position move about 0.07m backward; The increase of flue gas velocity doesn't have a distinct impact on the deposition intensity and deposition probability of the NH4HSO4 adhesion area but can decrease these values in area without NH4HSO4 adhesion. Meanwhile, as the flue gas velocity increases 2.5m/s, the NH4HSO4 deposition position move 0.065m forward; The air temperature mainly effects the position of NH4HSO4 adhesion area and has no obvious effects of the other parameters of deposition characteristics. As the air temperature increases 10K, NH4HSO4 deposition position move about 0.08m backward. |
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