In a circulating evaporator, the liquid rises again into the overheating tube according to the principle of the siphon pump. In the separator connected thereto, the liquid is separated from the steam and flows back to the evaporator through the circulation pipe to form a closed circuit cycle. The greater the temperature difference between the heating chamber and the boiling chamber, the more steam bubbles are generated, which enhances the action of the siphon pump and increases the flow rate for good heat transfer.

　　 The standard evaporator is an old-fashioned circulating evaporator. A thicker circulation tube is installed at the center of the heating tube bundle, and the liquid level is higher than the upper tube sheet, so the amount of liquid is relatively high.

　　 Forced circulation evaporators are used to avoid fouling or crystallization of products boiling on the heating surface, for which reason the flow rate in the tubes must be high. The circulating liquid is heated as it flows through the heat exchanger and then partially vaporized as the pressure in the separator decreases, thereby cooling the liquid to a boiling temperature corresponding to the pressure. Due to the circulation pump, the operation of the evaporator is basically independent of the temperature difference, the recirculation rate of the material can be adjusted, and the evaporation rate is set within a certain range. In the crystallization application, the crystal can be adjusted by circulating flow rate and using special separation. The device design is separated from the circulating crystal slurry.

　　 The tubes can be arranged horizontally or vertically, depending on the conditions of the site and the requirements of the process, and in particular, when hot water is used instead of water vapor as the heating medium, a plate heat exchanger can be used.

1、Discharge pump

2、Discharge pump

3、Inlet

4、Splitter

A、Heating steam inlet

B、Concentrate outlet

C、Condensate outlet

D、Secondary steam outlet

E、Heat exchanger

　　 Spiral tube evaporators are particularly suitable for achieving high concentrations and high viscosities. In order to achieve a high evaporation ratio, such evaporators operate at high temperature differences and in a single pass.

　　 In the spiral heating tube, the liquid to be evaporated flows from the top to the bottom, and at the same time, the boiling film flows in parallel with the steam. Since the heating tube is of course spiral shape, a long tube can be accommodated in a medium-high apparatus, after a long period of time. The steam generated in the flow of the pipe exerts a high shear force on the liquid film. For this reason, the curved spiral tube will cause a secondary flow, which is applied to the flow along the tube axis, which promotes turbulence and enhances heat transfer in the case of high viscosity.