Patent ID: 7999120

Claim:
A process for continuously removing a target product X in the form of crystals of the target product X from a liquid phase P comprising the target product X and constituents other than the target product X with the aid of a heat exchanger 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 an area for transferring heat out of the secondary chamber into the at least one primary chamber, in which liquid phase P is conducted continuously into the secondary chamber of the heat exchanger, while the at least one primary chamber is simultaneously flowed through by at least one fluid cooling medium such that crystals of the target product X are formed from the liquid phase P in the secondary chamber 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 in enriched form and whose content of target product X is at least 70% by weight to obtain a suspension S of crystals of the target product X in the liquid residual phase R which has a degree of crystallization Y, and suspension S is conducted continuously out of the secondary chamber of the heat exchanger, wherein variations in the desired degree of crystallization Y of the suspension S conducted out of the secondary chamber of the heat exchanger are minimized by determining and then minimizing the difference, determined at a particular operating time with the aid of a process computer, between (1) the flow of heat of crystallization {dot over (Q)} Kr,Y which develops in the secondary chamber according to the desired degree of crystallization Y, and (2) the difference formed between the heat flow {dot over (Q)} out otherwise conducted overall out of the secondary chamber of the heat exchanger and the heat flow {dot over (Q)} in otherwise conducted overall into the secondary chamber of the heat exchanger, and wherein the target product X is acrylic acid, methacrylic acid, p-xylene or N-vinylpyrrolidone.