净化后含氚废水高压微雾大气载带蒸发实效模拟验证

Simulation⁃based verification of evaporation efficiency for an air carrier discharge with purified tritium⁃containing wastewater using high pressure spray technology

目的确认净化后含氚废水经高压微雾喷嘴喷射后,随载带气在水平蒸发室内的输运特性和蒸发实效。方法基于设计工况和相似性准则搭建单喷嘴蒸发特性缩比实验台架,探究所产生的微雾在水平蒸发室内的设计蒸发情况;同时结合实验数据,采用Ansys Fluent软件中的离散相模型(DPM),构建描述微雾载带和蒸发的数值模型;在此基础上,进一步模拟分析设计水平蒸发室内多喷嘴工况条件下的蒸发进程和蒸发实效。结果对于单喷嘴实验,喷嘴中心线处微雾的粒径分布在12~50μm之间,近似于Rosin⁃Rammler粒径分布,且相对光照强度随距离增加呈指数减小,说明微雾粒径和浓度均快速减少,微雾的蒸发速度较快。对于水平蒸发室多喷嘴喷射模拟,即使对于最不利蒸发的设计工况,蒸发百分比也可高达99%,并且少量逃逸微雾也将在与其他工艺排气共同混合的过程中不断蒸发,直至在竖直烟囱段内实现完全蒸发。结论在设计微雾粒径、典型运行工况和模拟区域来流的条件下,水平蒸发段基本可以实现微雾的完全蒸发,从而确保含氚废水经高压喷雾载带后,在离开烟囱出口处可以实现完全蒸发。

Objective To confirm the transportation and evaporation efficiency of micro droplets sprayed by high⁃pressure nozzles from purified tritium⁃containing wastewater with carrier gas in the horizontal evaporation chamber.Methods A scale test bench with a single high⁃pressure nozzle had been built based on design conditions and similarity criteria to explore the designed evaporation characteristics of generated micro droplets in the horizontal evaporation chamber.At the same time,combined with experimental data,a suitable evaporation model was constructed using the Discrete Phase Model(DPM)in Ansys Fluent.On this basis,further simulation and analysis were conducted on the evaporation process and efficiency under the condition of multiple nozzles in the desighed horizontal evaporation chamber.Results For single nozzle tests,the particle size of micro droplets along the nozzle centerline was between 12-50μm and the particle size distribution was similar to the Rosin⁃Rammler distribution.Besides,the relative light intensity decreased exponentially with distance,indicating that the particle size and concentration of micro droplets both decreased rapidly,which means the evaporation rate of micro droplets was rapid.For the simulation of multiple nozzles injection in the desighed horizontal evaporation chamber,even for the hardest design condition,the evaporation percentage reached up to 99%,and small amount of the escaping micro droplets continued to evaporate during the process of mixing with other process exhaust until complete evaporation in the vertical chimney section.Conclusions Under the conditions of desighed sprayed particle size distribution,typical operating conditions and the incoming flow similar to the supposed area,the complete evaporation of the micro droplets can be basically achieved in the horizontal evaporation chamber,so as to ensure the complete evaporation of purified tritium⁃containing wastewater from the outlet of the chimney.