低温烟气余热蒸发脱硫废水工艺研究及工程应用

Research and engineering application on evaporation technology of FGD wastewater using low-temperature flue gas

低温烟气余热蒸发脱硫废水以其低成本优势引起业内关注。通过工艺研究,确定了该工艺的主要设计参数,浓缩塔内烟气流速为3.5 m/s,浓缩塔蒸发区高度为5.8 m,浓缩塔内设置2层喷淋层,每层喷淋层采用空心锥大流量碳化硅喷嘴。采用CFD软件对浓缩塔进行了流场模拟,采用欧拉法和拉格朗日法分别处理气相和液滴,并且考虑了相间的双向耦合作用。模拟结果显示:浓缩塔的烟气流速、浓缩塔的有效高度、2层喷淋层及喷嘴布置均设计合理;塔内气液相流场分布均匀,具有很高的换热效率。以上述模拟结果和设计为依据,在鄂州电厂三期项目建造了低温烟气余热蒸发脱硫废水示范工程。在运行过程中浓缩液的盐浓度达到了饱和并结晶析出,以Cl^(-)计浓缩倍率达到了15倍;该项目运行已超过5000 h,验证了该脱硫废水零排放技术的工程可行性。

As the technology of evaporation of FGD wastewater using low-temperature flue gas had the cost advantage,the technology attractes the attention of thermal power industry.By the technology researching,the technological conditions not only were determined,but also the key design parameters that it was optimal to select concentrating tower were provided.In the concentrating tower the flue gas velocity was determined to be 3.5 m/s and height of evaporation zone was determined to be 5.8 m.At the same time,two spray layers were arranged in the concentrating tower,each of which was a hollow cone-shaped high-flow silicon carbide nozzle.The flow fields of concentrating tower as core equipment were researched by CFD software.Taken the double phase coupling into account,gas phase and liquid drop respectively were studied by using Euler′s method and Lagrangian′s method.The simulation results are exhibited.Not only do the velocity of flue gas and valid height of tower reasonably design,but also two spray layers and the arrangement of nozzle is reasonably designed.The flow fields between the gas phase and liquid phase are uniformly distributed and the thermal efficiency are high in concentrating tower,which has a performance that there is rational design for concentrating tower.According to the results of simulation and design basis,the demonstration project of evaporation of FGD wastewater using low-temperature flue gas was constructed in Ezhou power plant the third project.During operation,with salt concentration reached saturation,the crystals of salt is precipitated from concentrated solution,which has a phenomenon that concentration ratio could reaches 15 in terms of chloride ions.The project has continued operating 5000 h,so it is proved that zero liquid discharge of desulfurization wastewater is attained.