固体颗粒对流化床多相蒸发海水淡化操作浓缩比及膜传热系数的影响

提高海水淡化操作浓缩比，不仅可以提高造水比，还可以有效降低淡化后浓海水再利用的后处理成本，故其是实现低成本零排放的关键之一。在一套循环流化床多相蒸发海水淡化实验装置上，分别采用汽-液两相及汽-液-固三相操作，考察固体颗粒对海水淡化操作浓缩比及膜传热系数的影响，并分析垢层的主要成分。实验表明：高温下CaSO4首先析出，是形成垢层的主要成分；采取汽-液两相操作，膜传热系数保持在1.75 kW·m-2·K-1左右，操作浓缩比可达到3.8左右；采取汽-液-固三相操作，固体颗粒强化传热和防除垢的作用显著，加入颗粒体积分数为4%时，在膜传热系数保持在2.3 kW·m-2·K-1左右不降低的情况下，海水淡化操作浓缩比达到5.8以上。

Effects of solid particles on experimental concentration factor of seawater desalination and film heat transfer coefficient in fluidized bed with multi-phase evaporation

Increasing seawater desalination concentration factor can improve the performance ratio and effectively reduce the post-treatment cost of the concentrated seawater that is reused,therefore,it is one of the keys to realizing low-cost zero discharge of seawater desalination.The experiment was carried out in a multi-phase circulating fluidization bed(CFB)evaporator.It aimed to study the effects of particle volume fraction on seawater desalination concentration factor and film heat transfer coefficient.The main components of the scaling were also analyzed.The operations of vapor-liquid two-phase boiling flow and vapor-liquid-solid three-phase boiling flow were investigated in the experiment.The results showed that calcium sulfate is the main component of the scaling,and it was firstly separated out in the seawater desalination experiment.In the vapor-liquid two-phase boiling flow,the film heat transfer coefficient was kept at 1.75 kW·m-2·K-1 and concentration factor reached 3.8.In the vapor-liquid-solid three-phase boiling flow,the result revealed that solid particles remarkably enhanced heat transfer and improved the prevention and removal of fouling.When particle volume fraction was 4% and film heat transfer coefficient was kept at 2.3 kW·m-2·K-1,seawater desalination concentration factor reached more than 5.8.