降膜蒸发器

概述：

由于具有传热系数，适应温差小，高真空蒸发的特点，可广泛利用低品质废热(如干燥机热空气及烟道气)，余热冷凝水，过程水及其闪蒸汽)组成废热蒸发机组可少用或不用新鲜蒸汽而完成浓缩任务。具有传热效能高，温差小，无液柱引起的沸点损失、动力消耗少的优点。在降膜蒸发系统中，物料呈膜状覆盖整个换热管内壁，沿换热管向下流动同时蒸发。即使在蒸发温差较低的情况下仍有可能获得较高的传热系数。换热管中部充满物料蒸发形成的二次蒸气，设计中可以根据情况，选择二次蒸汽与物料在换热管中同向或逆向流动。离开换热管的二次蒸汽然后进入分离器完成汽液分离。分离器可采用常规的离心式或冲击式可以设计为独立于降膜加热器的分体式，也可以是与加热器集成的一体式。一体式的设计可以缩小占地空间，降低安装成本。蒸发有轻微结垢问题的物料需要采用循环茶发;即使物料循环，采用降设计也比强制循环节能很多。热敏的物料可采用直流程降膜设计以缩短物料停留时间，同时降低的能耗。膜发系统适用于处理没有结垢问题或结垢系数低的物料，通常不能用来结品。但根据蒸发物料的特性，可以在设计中合并降膜与强制循环两种形式，用于处理有结垢问题的物料和连续结品系统。在MVR(机械蒸汽压缩)和TVR(蒸汽动力热泵)设计中，低蒸发温差可以降低电耗和蒸汽消耗，降膜设计可以用于蒸发温差较低的情况，所以较适用于这类设计。受物料本身特性的影响或采用低温废热蒸发时(例如管束尾气或液化闪蒸汽)，蒸发器内物料温度受到限制，与升膜相比采用降膜设计可放入更多效以降低能耗。降膜系统普遍应用于食品，制药，化工，造纸/制浆，和煤化工等行业。

Because of the characteristics of heat transter coefficient,small temperature difference and high vacuum evaporation, low-qualit waste heat (such as dryer hot air and flue gas) can be widely used, and waste heat (condensed water. process water and its flash steam) can be used to form a waste heat evaporation unit,which can complete the concentration task with little or no fresh steam. It has the advantages of high heat transfer efficiency,small temperature difference,no boiling point loss caused by liquid column and less power consumption. In the falling film evaporation system, the material covers the inner wall of the whole heat exchange tube in the form of a film, and flows downward along the heat exchange tube while evaporating. Even if the evaporation temperature difference is low, it is stil possible to obtain a higher heat transfer coefficient,The middle part of the heat exchange tube is filled with secondary steam formed by evaporation of materials. and the secondary steam and materials can be selected to flow in the same direction or in the opposite direction in the design according to the situation.The secondary steam leaving the heat exchange tube then enters the separator to complete vapor-liquid separation. The separator can adopt conventional centrifugal or impact type; It can be designed as a separate type independent of the falling film heater,or it can be integrated with the heater.The integrated design can reduce the floor space and the installation cost. Evaporation of materials with slight scaling problems requires cyclic evaporation Even if the material circulates, the falling film design is much more energy-saving than forced circulation,For heat-sensitive materials, straight-flow falling film desian can be used to shorten the residence time of materials and reduce the eneray consumption of pumps. Falling film evaporation system is suitable for treating materials with no scaling problem or low scaling coefficient, and usually cannot be used for crystallization,However,according to the characteristics of evaporated materials, falling film and forced circulation can be combined in the design to deal with materials with scaling problems and continuous crystallization systems. In MVR (mechanical vapor compression)ａnd TVR (steam driven heat pump) designs, low evaporation temperature difference can reduce power consumotion and steam consumption. and falling film desian can be used in the case of low evaporation tomperature difference. so it is more suitable for this kind of desian. The maximum material temperature in the evaporator is limited by the characteristics of the material itself or when low-temperature waste heat evaporation is used (such as tube bundle tail aas or liauefied flash steam).Compared with the falling film design,more efficiency can be put in to reduce eneray consumption.Falling film svstems are widelv used in food pharmaceuticalchemical.paper/pulpａnd coal chemical industries.

特点：
1、适用于浓度低，含固量少，结垢倾向较低的物料;
2、适用于热敏性物料，传热系数高;
3、温差小，真空蒸发，保证物料管路足够的液状膜，避免干辟，结垢现象:
4、无液柱压力引起的沸点温差损失，温差损失小，循环量少，动力消耗少。
1.Suitable for materials with low concentration, low solid content and low scaling tendency:
2.It is suitable for heat-sensitive materials with high heat transfer coefficient:
3. The temperature difference is small, and vacuum evaporation ensures enough liquid film in the material pipeline to avoid dry wall and scaling;
4.There is no loss of boiling point temperature difference caused by liquid colun pressure, and the loss of teperature difference is small with less circulation and less power consumption.

技术参数：