脱硫废水旋转喷雾蒸发特性实验研究

脱硫废水旋转喷雾干燥技术是一种利用热烟气蒸发脱硫废水的零排放技术。开展了不同悬浮物（SS）含量的脱硫废水原水以及经浓缩的高盐废水的蒸发实验，采用可视化手段观察了脱硫废水在干燥塔内的蒸发特性，考察了脱硫废水喷雾蒸发过程中停留时间、进口烟气温度、气液比对蒸发特性的影响。结果表明，旋转喷雾蒸发工艺对高盐、高SS含量等复杂脱硫废水组分具有较佳的适应性；脱硫废水从旋转雾化器喷出后迅速蒸发，主蒸发区在雾化盘下方0.75~1.00 m区域内；随后是蒸发析出的未干盐分及未完全蒸发的废水液滴进一步蒸干至含水率低于2 %；烟气在喷雾干燥塔内的停留时间需要维持在20 s以上才能保证塔出口灰分含水率低于2 %；入口烟气温度越高，其塔底及塔出口的灰分含水率越低，在气液比为12 000 m³/m³（标准状态）的废水工况下，入口烟温为280 ℃时已经难以保证废水液滴良好蒸发；在入口烟气温度为340 ℃、气液比大于10 000 m³/m³（标准状态）时，塔底灰分含水率小于2%，蒸发效果良好。

Experimental Study on the Characteristics of Rotating Spray Evaporation of Desulfurization Wastewater

As a type of zero-discharge technologies, the rotary spray drying technology utilizes hot flue gas to evaporate desulfurization wastewater. In this paper, the evaporation test is carried out for both the raw wastewater with different suspended solid (SS) content and the concentrated high salinity wastewater. Specifically, the evaporation characteristics of the desulfurization wastewater in the drying tower are examined with the aid of visualization techniques. Moreover, the impacts of residence time duration, inlet flue gas temperature and gas-liquid ratio on the evaporation characteristics are also investigated during the spray evaporation process of the desulfurization wastewater. The results show that the rotary spray evaporation process has better adaptability to complex desulphurization wastewater components such as high salinity and high SS content. After sprayed from the rotary atomizer, the desulfurization wastewater evaporates rapidly mainly into the zone of 0.75~1.00 m below the atomization tray, and then the precipitated salt and the incompletely evaporated wastewater droplets are further evaporated until the moisture content is less than 2%. The residence time of the flue gas needs to last at least 20 seconds in the spray drying tower so as to ensure the moisture content of ash particles to be less than 2% at the outlet of the tower. The higher the temperature of the inlet flue gas, the lower the particle moisture content at both the bottom and the outlet of the tower. As for the wastewater with the gas-liquid ratio at 12 000 m³/m³ (standard state), the expected outcome of evaporation of wastewater droplets could hardly be guaranteed with the inlet smoke temperature at 280 ℃. However, if the inlet flue gas temperature is maintained at 340 ℃ and the gas-liquid ratio is greater than 10 000 m³/m³(standard state), the bottom ash moisture content is dropped down below 2%, which shows good evaporation effect.