The forced circulation evaporator generates external power through a large flow circulation pump, and sends the crystal slurry or solution in the separator into the heating chamber at a high speed of 1.5-3 meters per second. The material is heated during the flow in the heat exchange tube, with a temperature rise of about 1-5 ℃. The heated material enters the separator, and due to the decrease in pressure, the material evaporates instantly by flash evaporation, while the liquid temperature cools to its boiling point at the current pressure. The generated secondary steam is discharged from the top of the separator, and the finished liquid or concentrated liquid is discharged from the bottom or continues to circulate.