Regulation of a wash column in a melt crystallization process

1. A method for regulating a wash column in a melt crystallization process, comprising:

regulating the position of a build-up front in the wash column by means of at least one optical line detector.

2. A method for regulating a wash column in a melt crystallization process in which

a suspension, which contains, suspended in a mother liquor, crystals of a substance to be purified, is passed continuously into a wash column,

a crystal bed of crystals of the substance to be purified forms in the wash column, the crystal bed having a build-up front at which crystals of the suspension passed and continuously accumulate,

crystals are continuously removed at that end of the crystal bed which is opposite to the build-up front, the crystals removed are melted, a part of the melt is removed as pure product stream and another part of the melt is passed as a wash liquid stream through the crystal bed in the direction opposite to the transport direction of the crystals, a wash front forming in the crystal bed, wherein the position of the build-up front and/or of the wash front in the wash column is regulated by means of at least one optical line detector.

3. A method as claimed in claim 2 , wherein the position of the wash front is measured by means of an optical line detector and is regulated to a setpoint position by controlling the pure product stream taken off.

4. A method as claimed in either of claims 2 and 3 , a hydraulic wash column being used, wherein the position of the build-up front is measured by means of an optical line detector and is regulated to a setpoint position in the wash column by controlling the hydrodynamic pressure, which is neither a measured variable nor a control variable, or controlling the amount of liquid fed in above the build-up front.

5. A method as claimed in any of claims 2 and 3 , wherein the line detector used comprises at least one linear array of fiber-optic reflection probes.

6. A method as claimed in any of claims 2 and 3 , wherein the line detector used comprises at least one line camera, in particular a CCD line camera.

7. An apparatus for separating crystals and mother liquor in a suspension crystallization process, comprising

a wash column which has at least one feed line for a crystal suspension, filtration means for removing mother liquor and means for removing crystals from a crystal bed at an end of the crystal bed which is opposite to a build up front at which crystals of the suspension passed in continuously accumulate,

means for melting the crystals removed,

a takeoff means for removing a part of the melt as pure product stream,

at least one measuring means for determining the position of a build-up front and/or of a wash front of the crystal bed in the wash column,

means for regulating the position of the build-up front and/or the position of the wash front,

wherein the measuring means comprises at least one optical line detector.

8. An apparatus as claimed in claim 7 , wherein the optical line detector comprises a linear array of fiber-optic reflection probes which are arranged in a wall of the wash column.

9. An apparatus as claimed in claim 7 , wherein at least one transparent window is arranged in a wall of the wash column, and wherein the optical line detector comprises at least one line camera, in particular a CCD line camera.

10. An apparatus as claimed in claim 9 , wherein the optical line detector comprises a color CCD line camera.

11. A method as claimed in claim 4 , wherein the line detector used comprises at least one linear array of fiber-optic reflection probes.

12. A method as claimed in claim 4 , wherein the line detector used comprises at least one line camera, in particular a CCD line camera.

13. An apparatus for separating crystals and mother liquor in a suspension crystallization process, comprising

a wash column which has at least one feed line for a crystal suspension, a filtration mechanism for removing mother liquor and a removal mechanism for removing crystals from a crystal bed at an end of the crystal bed which is opposite to a build up front at which crystals of the suspension passed in continuously accumulate,

a melting mechanism for melting the crystals removed,

a takeoff mechanism for removing a part of the melt as pure product stream,

at least one measuring mechanism for determining the position of a build-up front and/or of a wash front of the crystal bed in the wash column,

a regulating mechanism for regulating the position of the build-up front and/or the position of the wash front,

wherein the measuring mechanism comprises at least one optical line detector.

14. An apparatus as claimed in claim 13 , wherein the optical line detector comprises a linear array of fiber-optic reflection probes which are arranged in a wall of the wash column.

15. An apparatus as claimed in claim 13 , wherein at least one transparent window is arranged in a wall of the wash column, and wherein the optical line detector comprises at least one line camera, in particular a CCD line camera.

16. An apparatus as claimed in claim 15 , wherein the optical line detector comprises a color CCD line camera.

17. A method for regulating a wash column according to claim 1 , further comprising:

regulating the position of a wash front in the wash column by means of at least one optical line detector.

18. A method for regulating a wash column in a melt crystallization process, comprising:

regulating the position of a build-up front and/or of a wash-front in the wash column by emitting light onto said build-up front and/or said wash front and detecting light reflected by said build-up front and/or said wash front by at least one optical line detector.