Equipment for crystallization operation. There are many types of crystallizers, which can be divided into evaporation crystallizer and cooling crystallizer according to the method of obtaining supersaturation state of solution; According to the flow mode, it can be divided into mother liquor circulating crystallizer and crystal slurry (i.e. the mixture of mother liquor and crystal) circulating crystallizer; According to the operation mode, it can be divided into continuous crystallizer and intermittent crystallizer.