Process for operating a continuous removal of a target product X in the form of fine crystals

A process for continuously removing a target product X in the form of fine crystals of the target product X from a liquid phase P consisting of the target product X and constituents Bi other than the target product X, whose total mole fraction of constituents Bi has the value MB,Ptot, comprising the operation of an indirect heat transferer having a secondary chamber and at least one primary chamber, in which the secondary chamber and the at least one primary chamber are each spatially separated from one another by at least one material dividing wall which serves as a surface for transfer of heat out of the secondary chamber into the at least one primary chamber, by conducting a stream of liquid phase P into the secondary chamber of the heat transferer, while the at least one primary chamber is simultaneously flowed through by at least one fluid cooling medium such that, in the secondary chamber, fine crystals of the target product X form from the liquid phase P to leave a liquid residual phase R, and are suspended in the remaining liquid residual phase R which, compared to the liquid phase P, comprises the constituents other than the target product X with a total mole fraction MB,Rtot>MB,Ptot and whose content of target product X is at least 70% by weight to obtain a suspension S of fine crystals of the target product X in the liquid residual phase R which has a degree of crystallization Y, and suspension S with the temperature TSout is withdrawn continuously from the secondary chamber of the heat transferer, and further comprising the supply of suspension S withdrawn with the temperature TSout to a mixed buffer vessel, and, with the aid of a pump, the charging of a separating apparatus from the buffer vessel with suspension of fine crystals of the target product X present in the buffer vessel, and the separation of the suspension supplied to the separating apparatus into crystals present therein and liquid phase present therein,

• wherein, on the route from the secondary chamber into the buffer vessel, in the buffer vessel and/or in one or more pumped circulation lines leading out of the buffer vessel and back into it, the temperature of the suspension S fed to the buffer vessel is increased with the aid of an external energy source to a value TPu above TSout and/or the total mole fraction of the constituents other than the target product X which are present in the liquid residual phase R of the suspension S fed to the buffer vessel is increased to a value MB,Putot above MB,Rtot by external addition of constituents other than the target product X.