What is Falling film evaporator
Falling film evaporator is to add the material liquid from the upper tube box of the heating chamber of the falling film evaporator. After the liquid distribution and film forming device, it is evenly distributed into the heat exchange tubes. Under the action of gravity, vacuum induction and air flow, it becomes a uniform film. Flow from top to bottom. During the flow process, it is heated and vaporized by the heating medium in the shell side, and the generated steam and liquid phase enter the separation chamber of the Falling film evaporator. After the vapor and liquid are fully separated, the steam enters the condenser for condensation or enters the next-effect evaporator as the heating medium. To achieve multi-effect operation, the liquid phase is discharged from the separation chamber.
Evaporation is a unit operation for concentrating a solution. Usually, the solvent can be volatilized, but the vapor pressure of most solutes is close to zero and cannot be volatilized. The process of evaporating a solution under boiling conditions to remove part of the solvent and condense it is called evaporation. In most cases, the evaporator uses water vapor as the heating medium to indirectly transfer heat to the solution through the metal wall. After the solution is heated, the solvent boils and vaporizes, and the generated steam is called secondary steam.
The material liquid of the vertical Falling film evaporator enters the material liquid distributor from the top. The material liquid distributor evenly distributes the material liquid into each heating tube and makes it flow down the inner wall of the tube in a film shape. The liquid film is vaporized by the heat transmitted from the tube wall. When the heat transfer temperature difference is small, vaporization occurs on the inner surface of the strongly disturbed membrane, rather than at the interface between the heating tube and the liquid membrane, so it is not easy to scale. The steam produced usually flows down side-by-side with the liquid film. Due to the large vaporization surface, the amount of liquid foam entrained in the steam is small, and the material liquid flows in a film on the inner wall of the tube, and does not fill the entire section of the tube, so the amount of material liquid passing through can be very small.
The material-liquid distributor is a key component of the Falling film evaporator. The heat exchange intensity and production capacity of the Falling film evaporator essentially depend on the uniformity of the material-liquid distribution along the heat exchange tube. The so-called uniform distribution not only means that the liquid must be evenly distributed into each tube, but also evenly distributed along the entire periphery of each tube, and to maintain its uniformity over the entire length of the Falling film evaporator tube.