脱硫废水旁路塔雾化蒸发数值模拟

Numerical Simulation of Evaporative Evaporation of Desulfurization Wastewater by the By-pass Tower

脱硫废水成分复杂难以回用,一些电厂已开始采用烟道雾化蒸发处理技术对其进行处理。脱硫废水直接喷入烟道会带来腐蚀、积灰、堵塞等问题,设置旁路蒸发塔对脱硫废水进行干燥是一种较好的选择。为研究此项技术,以某330 MW机组为例,通过计算脱硫废水与烟气的热质平衡,确定了烟气抽取量,建立了物理模型,利用数值模拟的方法对烟气流场进行优化,对喷嘴布置方式、液滴直径、烟气温度等的选择进行稳态模拟。结果表明:抽取烟气量仅占总烟气量的2.27%,烟气流场即能够充满整个蒸发塔;三喷嘴的雾化蒸发效果可以使蒸发塔出口温度达到设计值120℃;液滴直径80μm以下,液滴颗粒无贴壁,液滴直径60μm时蒸发效果好。为延长颗粒停留时间,使颗粒无贴壁、少团聚,宜采用烟气旋流方式、三喷嘴、60μm雾化粒径以及600 K以上的入口烟气温度。

Desulfurization wastewater is difficult to be reused due to its complex composition.Therefore the flue atomization evaporation technology has been applied in the wastewater treatment at some power plants.However,the direct injection of desulfurization wastewater into the flue will cause problems such as corrosion,ash accumulation and clogging.A better option is offered by setting the bypass evaporation tower to dry the desulfurization wastewater.In order to study this technology,taking a 330 MW unit as an example,the flue gas extraction amount was determined by calculating the thermal mass balance between the desulfurization wastewater and the flue gas.Then the physical model was established,and the smoke flow field was optimized by numerical simulation.The steady state simulation was carried out for the nozzle arrangement,droplet diameter and flue gas temperature.The results show that even though the amount of flue gas extracted only accounts for 2.27%of the total flue gas volume,the flue gas flow field is enough to fill the entire evaporation tower.As a result of the atomization evaporation effect from the three nozzles,the evaporating tower outlet temperature can reach reach the designed value of 120°C.If the droplet diameter under 80μm,the droplet particles will not stick to the wall.In particular the desirable evaporation effect is achieved when the droplet diameter is 60μm.In summary,to prolong the residence time of the particles and make the particles non-adherent and less agglomerated,the flue gas swirling method is preferable with the selection of three nozzles,the atomized particle size of 60μm and the inlet flue gas temperature of 600 K.