The central circulation crystallizer consists of a vertical heating tube bundle consisting of boiling heating tubes, central circulation tubes, and upper and lower tube plates, ensuring that the solution is fully heated and well circulated. The central circulation tube and heating tube are generally fixed on the upper and lower tube plates by expansion tube method or welding method, thus forming a vertical heating tube bundle. The solution flows inside the tube, while the heating steam flows between the tube bundles. In order to improve heat transfer efficiency, several baffles can be added between the pipes, or several rows of heating pipes can be removed to form steam channels. At the same time, with the full distribution of non condensable gas discharge pipes, it is conducive to the uniform distribution of heating steam. There are non condensable gas discharge pipes, heating steam pipes, condensate water discharge pipes, etc. on the outer side of the heater body, thereby improving heat transfer and condensation efficiency.

The evaporation chamber of the central circulation crystallizer is a cylindrical body at the upper part of the heating chamber. After the solution is heated, it vaporizes and must have a certain height and space to separate the vapor and liquid. The secondary steam rises and the solution descends through the central circulation tube, ensuring continuous circulation and concentration of the solution. The height of the evaporation chamber is mainly determined by the upward speed to prevent the material liquid from being carried by the secondary steam, while considering the need for cleaning and repairing the heating tube. Generally, it is 1.1-1.5 times the length of the heating tube. The evaporation chamber is equipped with mirrors, manholes, washing water, lighting, instruments, sampling devices, etc. There is a trap device at the top, which mainly separates the juice that may be carried by the secondary steam, ensures the cleanliness of the secondary steam, and is conducive to improving the heat transfer effect of the primary concentration pot and reducing the loss of material liquid. The top is connected to the secondary steam discharge pipe.

Due to structural limitations, the circulation speed of the central circulation crystallizer is generally below 0.4m/s-0.5m/s; Due to the continuous circulation of the solution, the concentration of the solution in the heating tube is always close to that of the finished liquid, resulting in disadvantages such as high viscosity and boiling point of the solution. In addition, the heating chamber of the evaporator is not easy to clean, and the circulation effect is poor when the viscosity is high. It can be applied to solutions with less severe scaling, a small amount of crystallization, and less corrosiveness during evaporation.