The invention relates to a self-circulating crystallizer and a multistage
continuous crystallization method. The crystallizer sequentially comprises a kettle head, an upper cylinder body, a middle cylinder body and a bottom hole-shrinkage cylinder body with a W-shaped bottom from top to bottom, wherein a steam outlet and / or a feeding hole are / is arranged on the kettle head, an annular spraying
pipe is arranged at the lower part of the kettle head; a middle straight cylinder section is arranged in the middle cylinder body, a flow guiding cylinder is arranged in the middle straight cylinder section, and a stirrer is arranged in the flow guiding cylinder; the
diameter of the middle cylinder body is larger than that of the upper cylinder body, and the
diameter of the upper cylinder body is larger than that of the middle cylinder body; and the lower part of the upper cylinder body and the upper part of the middle cylinder body are respectively connected with the circumference of the top ofthe middle straight cylinder section via a hole-shrinkage transition section, and a discharging hole is formed in the W-shaped bottom. The invention provides the method for realizing multistage continuous
evaporation, cooling or reaction
crystallization through the series connection of the crystallizer, the prepared crystals are large in
granularity and uniform in particle size, the problems thatthe product
granularity is small, equipment is seriously scaled, a pipeline is blocked, and the like in the
continuous crystallization process are improved, and the operation period of the continuouscrystallization process is prolonged.