升膜式蒸发器与降膜式蒸发器的比较

料液在升膜与降膜式蒸发器中均以膜的形式沿着管壁边流动边与管外加热介质进行热与质的交换并蒸发。两者都不适合浓度较高的易洁垢结焦或在蒸发过程中有结晶析出的料液的蒸发;不同点前者料液是在高速的二次蒸汽流及真空的作用下在管壁成膜并向上运动,蒸发后料液与二次蒸汽从蒸发器顶部进入分离器,实现蒸发后料液与二次蒸汽的分离,而降膜式蒸发器则是在料液分布器的作用下将来料均匀的分配给每根降膜管并以膜的状态沿着管壁在自身重力及二次蒸汽流的作用下自上而下流动,蒸发后的料液与二次蒸汽在蒸发器底部进入分离器中实现蒸发后料液与二次蒸汽的彻底分离。升膜式蒸发器要求加热温差较大,操作不易控制,易造成跑料等现象的发生。因此,近些年来很少应用。就此进行阐述。

Climbing film evaporator and the falling film evaporator

The material liquid in climbing film and falling film type evaporator flows in the formof a film along the tube wall side and outside the tube heating medium for heat exchange and e-vaporation with nature.Both of them are not suitable for high concentration coking or in the pro-cess of evaporation there is precipitation crystallization of material liquid evaporation; Differencematerial liquid is at high speed under the action of secondary steam and vacuum film and moveupward, material liquid after evaporation and secondary steam enter the separator from the top af-ter evaporation of feed liquid, the separation of the secondary steam can be aehiered, and thefalling film evaporator is under the action of material liquid distributor distributing incomingevenly to each tube falling film and in state of film along the tube wall under the action of its owngravity and secondary＇ steam flow from top to bottom, the material liquid after evaporation andsecondary steam enters the separator at the bottom in the evaporator in the material liquid afterevaporation and the secondary steam separate completely. Climbing film evaporator required heat-ing temperature difference is bigger, the operation is not easy to control, easy to cause run mate-rial, etc. As a result, there are few applications in recent years. Analyzed in this paper.