Characteristics analysis and parameters optimization of desulfurization wastewater evaporation in a rotary spray drying tower

Abstract

Recently, the rotary spray drying technology has received significant attention by virtue of its excellent performance in zero liquid discharge (ZLD) of desulfurization wastewater. Based on the Euler-Lagrangian numerical method of gas-liquid coupling, the gas multi-physical distribution is studied. Meanwhile, the relationship between the evaporation and dispersion characteristics of wastewater and various parameters such as deflector angle, deflector number, hot air distributor outlet radius difference, atomizer rotational speed and rotational direction is investigated. Numerical results show that the spray droplets can strengthen the vortex of the flue gas, thus increasing the evaporation rate. By increasing the deflector angle and the radius difference, droplets were observed to be more dispersed, which leads to improve evaporation efficiency on one hand but enhance the trend of droplets adhering to the wall on the other hand. The optimum deflector angle and radius difference are found to be 15° and 74 mm, respectively. The deflector number has little effect on the evaporation efficiency of droplets. It can be found that the evaporation time of droplets decreases with the increase of rotational speed, and the effect of the reverse rotation is more obvious. Under the case of reverse rotation at 20,100 rpm, the mean evaporation time is reduced to 0.2 s, and no droplets hit the wall.