Numerical Simulation Study on Spray Evaporation Process of Desulfurization Wastewater in Flue Duct

Abstract

Spraying flue gas desulfurization (FGD) wastewater into flue duct is a promising technology to achieve zero discharge of wastewater by evaporation in thermal power plants. In this study, a substantiated combined Eulerian-Lagrangian mathematical model is developed to calculate the thermo-fluid behavior of the FGD wastewater in the flue gas during evaporating process. In order to increase the amount of FGD wastewater to be treated at the same time and avoid the scale and corrosion on flue duct walls, the mounting spacing between two nozzles and the safe mounting spacing between nozzles and flue duct wall are analyzed. Then the effect of nozzle characteristics on droplets evaporation is studied, such as the flow rate, full cone angle and direction of a spray nozzle. Based on the achieved numerical results, a Least-Square Support Vector Machine (LSSVM) model is introduced to forecast the evaporation rate of droplets. The results show that the maximum evaporation rate of droplets can be obtained by spaying droplets in the co-flow direction of flue gas. An optimized arrangement of multiple nozzles having small flow rate is proposed to improve the droplets evaporation rate. The proposed LSSVM model can expeditiously predict the evaporation rate of droplets along the flue duct with high accuracy. All the findings of the present study can be used to guide the design of spraying FGD wastewater treatment technology.