Method for controlling vacuum pan

Claim 2

IN A METHOD FOR CONTROLLING AVACUUM PAN ACCORDING TO WHICH HEAT IS EXCHANGED BETWEEN A HEAT EXCHANGER AND A MASSECUITE TO GENERATE AND GROW CRYSTALS IN THE MASSECUITE IN A BATCH OPERATION, THE IMPROVEMENT COMPRISING (A) MEASURING THE INTER-CRYSTAL GAP LENGTH OF THE CRYSTALS GROWN IN THE SOLUTION AND CONTROLLING THE QUANTITY OF THE SUPPLY OF THE SOLUTION ON THE BASIS OF THE MEASURED INTER-CRYSTAL GAP LENGTH TO EFFECTIVELY GROW CRYSTALS AND (B) MEASURING THE VALUE OF AT LEAST ONE OTHER PARAMETER INDICATIVE OF THE PROGRESS OF THE CRYSTAL GROWING PROCESS, COMPRISING THE MEASURED INTER-CRYSTAL GAP LENGTH WITH A PROGRAMMED VALUE FOR THE INTER-CRYSTAL GAP LENGTH PROVIDED BY THE FIRST PROGRAM,COMPARING THE MEASURED VALUE OF SAID OTHER PARAMETER WITH A PROGRAMMED VALUE FOR SAID OTHER PARAMETER PROVIDED BY A SECOND PROGRAM, AUTOMATICALLY PREFERENTIALLY SELECTING EITHER SAID FIRST PROGRAM OR SAID SECOND PROGRAM FOR CONTROLLING SAID SUPPLY QUANTITY, AND CONTROLLING SAID SUPPLY QUANTITY ON THE BASIS OF THE DEVIATION OF THE MEASURED VALUE FOROM THE PROGRAMMED VALUE OF THE PARAMETER CORRESPONDIN TO THE SELECTED PROGRAM.

Claim 3

A method for controlling a vacuum pan as claimed in claim 1, wherein when the deviation of the measured value of at least one of the parameters corresponding to the non-selected programs from the corresponding programmed value exceeds a predetermined level, the progress of the program is suspended; and when the deviation of the measured value of the parameter corresponding to the selected program becomes equal to a predetermined level, the control of the supply quantity of the solution is resumed on the basis of the selected program.

Claim 4

after the addition of the seeds, automatically selecting by means of a selector the deviation between the detected value of the consistency of the massecuite in the vacuum pan and a signal from a consistency control programmer in preference to the deviation between the signal from the level control programmer and the detected level of the massecuite in the vacuum pan for controlling the quantity of raw solution supplied to the vacuum pan, said consistency control programmer further controlling the quantity of warm water supplied to the vacuum pan.

Claim 5

after the addition of the seeds, automatically selecting by means of a selector the deviation between the detected value of the consistency of the massecuite in the vacuum pan and a signal from a consistency control programmer in preference to the deviation between the signal from the level control programmer and the detected level of the massecuite in the vacuum pan for controlling the quantity of raw solution supplied to the vacuum pan, said consistency control programmer further controlling the quantity of warm water supplied to the vacuum pan.

Claim 6

after a predetermined time period or when the level of the solution in the vacuum pan reaches a predetermined level after addition of the seeds, preferentially controlling the supply of raw solution and the supply of water to the vacuum pan with respect to the deviation between the detected value of the supersaturation of the massecuite in the vacuum pan and a signal from a consistency control program, the preferential control of step 2 being in preference to controlling the supply of raw solution by reference to the deviation between the detected value of the liquid level and the signal produced by the level control programmer, the preferential control of step 2 being automatically selected by means of a selector, and 3 after another predetermined time period or when the level of the massecuite in the vacuum pan reaches another predetermined level after the addition of the seeds, preferentially controlling the supply of raw solution and the supply of water to the vacuum pan by reference to the deviation between the detected value of the consistency of the massecuite and a signal from the consistency control programmer, the preferential control of step (3) being in preference to control by reference to the deviation of the detected value of the liquid level of the massecuite and the signal from the level control programmer, the preferential control of step (3 being automatically selected by means of a selector.

Claim 7

after a predetermined time period or when the level of the solution in the vacuum pan reaches a predetermined level after addition of the seeds, preferentially controlling the supply of raw solution and the supply of water to the vacuum pan with respect to the deviation between the detected value of the supersaturation of the massecuite in the vacuum pan and a signal from a consistency control program, the preferential control of step 2 being in preference to controlling the supply of raw solution by reference to the deviation between the detected value of the liquid level and the signal produced by the level control programmer, the preferential control of step 2 being automatically selected by means of a selector, and 3 after another predetermined time period or when the level of the massecuite in the vacuum pan reaches another predetermined level after the addition of the seeds, preferentially controlling the supply of raw solution and the supply of water to the vacuum pan by reference to the deviation between the detected value of the consistency of the massecuite and a signal from the consistency control programmer, the preferential control of step (3) being in preference to control by reference to the deviation of the detected value of the liquid level of the massecuite and the signal from the level control programmer, the preferential control of step (3 being automatically selected by means of a selector.

Claim 8

after the addition of the seeds, automatically selecting by means of a selector the deviation between the detected value of the supersaturation of the massecuite in the vacuum pan and a signal from a consistency control programmer in preference to the deviation between the signal from the level control programmer and the detected level of the massecuite in the vacuum pan for controlling the quantity of raw solution supplied to the vacuum pan, said consistency control programmer further controlling the quantity of warm water supplied to the vacuum pan.

Claim 9

after the addition of the seeds, automatically selecting by means of a selector the deviation between the detected value of the supersaturation of the massecuite in the vacuum pan and a signal from a consistency control programmer in preference to the deviation between the signal from the level control programmer and the detected level of the massecuite in the vacuum pan for controlling the quantity of raw solution supplied to the vacuum pan, said consistency control programmer further controlling the quantity of warm water supplied to the vacuum pan.

Claim 10

A method for controlling a vacuum pan as claimed in claim 1, wherein the average diameter of the crystals grown in the solution is used as said other parameter.

Claim 11

A method for controlling a vacuum pan as claimed in claim 1, wherein the level the solution is used as said other parameter.

Claim 12

A method for controlling a vacuum pan as claimed in claim 1, wherein the average diameter of the crystals grown in the solution is used as a component for controlling the supply quantity of the solution.

Claim 13

In a method for controlling a vacuum pan according to which heat is exchanged between a heat exchanger and a massecuite to generate and grow crystals in the massecuite in a bath operation, the improvement comprising (a) measuring the crystal content of the massecuite and controlling the supply quantity of the solution on the basis of the measured quantity to effectively grow crystals, and (b) measuring the value of at least one other parameter indicative of the progress of the crystal growing process, comparing the measured crystal content of the massecuite with a programmed value for the crystal content of the massecuite provided by a first program, comparing the measured value of said other parameter with a programmed value for said other parameter provided by a second program, automatically preferentially selecting either said first program or said second program for controlling said supply quantity, and controlling said supply quantity on the basis of the deviation of the measured value from the programmed value of the parameter corresponding to the selected program.

Claim 14

In a method for controlling a vacuum pan according to which heat is exchanged between a heat exchanger and a massecuite to generate and grow crystals in the massecuite in a bath operation, the improvement comprising (a) measuring the crystal content of the massecuite and controlling the supply quantity of the solution on the basis of the measured quantity to effectively grow crystals, and (b) measuring the value of at least one other parameter indicative of the progress of the crystal growing process, comparing the measured crystal content of the massecuite with a programmed value for the crystal content of the massecuite provided by a first program, comparing the measured value of said other parameter with a programmed value for said other parameter provided by a second program, automatically preferentially selecting either said first program or said second program for controlling said supply quantity, and controlling said supply quantity on the basis of the deviation of the measured value from the programmed value of the parameter corresponding to the selected program.

Claim 15

A method for controlling a vacuum pan as claimed in claim 6, wherein when the deviation of the measured value of at least one of the parameters corresponding to the non-selected programs from the corresponding programmed value exceeds a predetermined level, the progress of the program is suspended; and when the deviation of the measured value of the parameter corresponding to the selected program becomes equal to a predetermined level, the control of the supply quantity of the solution is resumed on the basis of the selected program.

Claim 16

A method for controlling a vacuum pan as claimed in claim 6, wherein the level of the solution is used as said other parameter.

Claim 17

In a method for controlling a vacuum pan according to which heat is exchanged between a heat exchanger and a massecuite to generate and grow crystals in the massecuite in a batch operation, the improvement comprising (a) measuring the consistency of the massecuite and controlling the supply quantity of the solution on the basis of the measured quantity to effectively grow crystals, and (b) measuring the value of at least one other parameter indicative of the progress of the crystal growing process, comparing the measured consistency of the solution with a programmed value for the consistency of the solution provided by a first program, comparing the measured value of said other parameter with a programmed value for said other parameter provided by a second program, automatically preferentially selecting either said first program or said second program for controlling said supply quantity, and controlling said supply quantity on the basis of the deviation of the measured value from the programmed value of the parameter corresponding to the selected program.

Claim 18

In a method for controlling a vacuum pan according to which heat is exchanged between a heat exchanger and a massecuite to generate and grow crystals in the massecuite in a batch operation, the improvement comprising (a) measuring the consistency of the massecuite and controlling the supply quantity of the solution on the basis of the measured quantity to effectively grow crystals, and (b) measuring the value of at least one other parameter indicative of the progress of the crystal growing process, comparing the measured consistency of the solution with a programmed value for the consistency of the solution provided by a first program, comparing the measured value of said other parameter with a programmed value for said other parameter provided by a second program, automatically preferentially selecting either said first program or said second program for controlling said supply quantity, and controlling said supply quantity on the basis of the deviation of the measured value from the programmed value of the parameter corresponding to the selected program.

Claim 19

A method for controlling a vacuum pan as claimed in claim 9, wherein when the deviation of the measured value of at least one of the parameters corresponding to the non-selected programs from the corresponding programmed value exceeds a predetermined level, the progress of the program is suspended, and when the deviation of the measured value of the parameter corresponding to the selected program becomes equal to a predetermined level, control of the supply quantity of the solution is resumed on the basis of the selected program.

Claim 20

A method for controlling a vacuum pan as claimed in claim 9, wherein the average diameter of the crystals grown in the solution is used as said other parameter.

Claim 21

A method for controlling a vacuum pan as claimed in claim 9, wherein the level of the solution is used as said other parameter.

Claim 22

In a process for controlling a vacuum pan in which a raw solution is heated to cause said raw solution to reach a supersaturated condition, crystal seeds as nuclei are added to the raw solution to form massecuite, and the massecuite is furthher heated and additional raw solution or water or both are supplied to the massecuite to thereby generate and grow crystals in the massecuite, the improvement comprising:

Claim 23

In a process for controlling a vacuum pan in which a raw solution is heated to cause said raw solution to reach a supersaturated condition, crystal seeds as nuclei are added to the raw solution to form massecuite, and the massecuite is furthher heated and additional raw solution or water or both are supplied to the massecuite to thereby generate and grow crystals in the massecuite, the improvement comprising:

Claim 24

The process according to claim 13, further comprising stopping the progress of the programs in the liquid level controller and the consistency controller when the detected level of the massecuite in the vacuum pan is different from the programmed value of the liquid level by a predetermined value, allowing heat exchange to be carried out while controlling the supply of raw solution and water with respect to the signals produced by said liquid level control programmer and said consistency control programmer at the time of the stopping of said programs, and resuming the progress of the programs in the level control programmer and the consistency control programmer when the level of the massecuite reaches a predetermined level.

Claim 25

In a process for controlling a vacuum pan in which a raw solution is heated to cause said raw solution to reach a supersaturated condition, crystal seeds as nuclei are added to the raw solution to form massecuite, and the massecuite is further heated and additional raw solution or water or both are supplied to the massecuite to thereby generate and grow crystals in the massecuIte, the improvement comprising:

Claim 26

In a process for controlling a vacuum pan in which a raw solution is heated to cause said raw solution to reach a supersaturated condition, crystal seeds as nuclei are added to the raw solution to form massecuite, and the massecuite is further heated and additional raw solution or water or both are supplied to the massecuite to thereby generate and grow crystals in the massecuIte, the improvement comprising:

Claim 27

The process according to claim 15, further comprising stopping the progress of the programs in the liquid level controller and the consistency controller when the detected level of the massecuite in the vacuum pan is different from the programmed value of the liquid level by a predetermined value, allowing heat exchange to be carried out while controlling the supply of raw solution and water with respect to the signals produced by said liquid level control programmer and said consistency control programmer at the time of the stopping of said programs, and resuming the progress of the programs in the level control programmer and the consistency control programmer when the level of the massecuite reaches a predetermined level.

Claim 28

In a process for controlling a vacuum pan in which a raw solution is heated to cause said raw solution to reach a supersaturated condition, crystal seeds as nuclei are added to the raw solution to form massecuite, and the massecuite is further heated and additional raw solution or water or both are supplied to the massecuite to thereby generate and grow crystals in the massecuite, the improvement comprising:

Claim 29

In a process for controlling a vacuum pan in which a raw solution is heated to cause said raw solution to reach a supersaturated condition, crystal seeds as nuclei are added to the raw solution to form massecuite, and the massecuite is further heated and additional raw solution or water or both are supplied to the massecuite to thereby generate and grow crystals in the massecuite, the improvement comprising:

Claim 30

The process according to claim 17, further comprising stopping the progress of the programs in the liquid level controller and the consistency controller when the detected level of the massecuite in the vacuum pan is different from the programmed value of the liquid level by a predetermined value, allowing heat exchange to be carried out while controlling the supply of raw solution and water with respect to the signals produced by said liquid level control programmer and said consistency control programmer at the time of the stopping of said programs, and resuming the progress of the programs in the level control programmer and the consistency control programmer when the level of the massecuite reaches a predetermined level.

Claim 31

In a method for controlling a vacuum pan in which heat is exchanged between a heat exchanger and a raw solution to generate and grow crystals therein, the improvement comprising measuring the value of a first parameter indicative of the progress of the crystal growing process, comparing the measured value of the first parameter with a programmed value for the first parameter provided by a first program, measuring the value of at least one other parameter indicative of the progress of the crystal growing process, comparing the measured value of said other parameter with a programmed value for the other parameter provided by a second program, automatically preferentially selecting either said first program or said second program for controlling the supply of the solution fed to said vacuum pan, and controlling the supply of solution fed to said vacuum pan on the basis of the deviation of the measured value from the programmed value of the parameter corresponding to the selected program.

Claim 32

In a method for controlling a vacuum pan in which heat is exchanged between a heat exchanger and a raw solution to generate and grow crystals therein, the improvement comprising measuring the value of a first parameter indicative of the progress of the crystal growing process, comparing the measured value of the first parameter with a programmed value for the first parameter provided by a first program, measuring the value of at least one other parameter indicative of the progress of the crystal growing process, comparing the measured value of said other parameter with a programmed value for the other parameter provided by a second program, automatically preferentially selecting either said first program or said second program for controlling the supply of the solution fed to said vacuum pan, and controlling the supply of solution fed to said vacuum pan on the basis of the deviation of the measured value from the programmed value of the parameter corresponding to the selected program.

Claim 33

The process according to claim 19, wherein when the deveation of the measured value of at least one of the parameters corresponding to the non-selected programs from the corresponding programmed value exceeds a predetermined level, the progress of the programs is suspended; and when the deviation of the measured value of the parameter corresponding to the selected program becomes equal to a predetermined level, the control of the supply quantity of the solution is resumed on the basis of the selected program.

Claim 36

The method according to claim 21, wherein said other parameter is the consistency of the solution.

Claim 37

The method according to claim 21, wherein said other parameter is the degree of supersaturation when the crystal growing process is in an unstable phase, and further wherein said other parameter is the consistency of the solution when the crystal growing process is in a stable phase.

Claim 38

The method according to claim 21 wherein said other parameter is the supersaturation of said solution.

Claim 39

The process according to claim 24, further comprising determining the value of the supersaturation of said solution by comparing the boiling point of said solution with the temperature in said vacuum pan.

Claim 40

The method according to claim 25, wherein the pressure in said vacuum pan is measured and the value of the temperature in said vacuum pan is determined by means of a pressure/temperature transducer.