JPS6365319B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method of setting a program in an apparatus for automatic crystal growth by programmatically controlling the hardness of the white undercoat in a crystal can.

<Prior art> In the crystal growth process using a vacuum crystal can, for example, as shown in FIG. It is supplied from the bottom via the solution valve 3. The heating steam S is supplied to the heating section 2 in the crystal can 1 via the control valve 4. The solution is concentrated by heating and evaporated, and at the same time, the solution is replenished, and when the crystallization concentration at which crystal precipitation is reached is reached, seed sugar is added to the solution through the valve 6 from the injector 5 to prepare each variety. generate crystal nuclei suitable for After that, in order to prevent these crystal nuclei from combining with each other and from generating new crystal nuclei of undesired species (pseudocrystals),
Concentration and crystal growth are continued by supplying differential water or solution while monitoring the inside of the can. When the crystals grow to a certain extent, the volume of the crystals per unit volume in the white (mixture of solution and crystals) exceeds a certain value, and the crystals come quite close to each other, pseudocrystals occur. It becomes relatively difficult for the crystals to occur, and when the solution is further concentrated and the crystals grow easily, the volume inside the can increases to a certain value, and when the grain size of the crystals grows to the required size, the can The white undercoat 7 inside is discharged from the discharge valve 8. The discharged white matter is separated into crystals and a solution by a centrifuge, and the solution is repeatedly used for crystal growth. In order to adjust the concentration of the white undercoat to an appropriate value in the roasted sugar, the difference water W or solution F can be supplied into the can 1 through the difference water valve 9 or the solution valve 3, and the state inside the can 1 can be monitored through the peephole. 10 can be monitored. The steam in the can 1 is drawn into a condenser 11 through a valve 12 by a vacuum pump 13, and this condenser 11 is cooled by cooling water W through a valve 14.

Various methods have been proposed for controlling the crystal can, but the intermittent crystal growth method, which focuses on the hardness of the white bottom and increases this value stepwise in a programmatic manner, is the control method that can realize stable operation. As a method, Japanese Patent Application Publication No. 1973
- As shown in No. 41248, it is becoming common.

Reference numeral 15 denotes a hardness meter such as a rheometer, and a measurement signal e _n representing the hardness of the white underside is guided to the adjustment section 161 of the sequence control device 16 . 162 is the hardness setting value e _s
a program setting section 1 that supplies the adjustment section 161 with
Reference numeral 63 indicates a valve operation operation that controls opening and closing of the solution valve 3 or the differential water valve 9 based on the output of the adjustment section 161.

Although not shown in Figure 1, there are other
A level meter for measuring the level inside the can, pressure regulating means for maintaining a constant degree of vacuum inside the can, etc. are provided.

<Problems to be Solved by the Invention> Next, a conventional program control method will be explained with reference to FIG. A is the measured value e _n and the set value e _s of hardness in a specific region of the crystal growth process during solution crystal growth.
B represents the opening/closing status of the solution valve 3.

At time t ₁ , the measured value e _n increases and the hardness setting value
Since the solution is supplied when the e _s reaches the m ₁ level, the hardness of the white bottom is temporarily loosened. The next set value e _s increases by Δm in steps from m ₁ and becomes m ₂ . At time t ₂ when e _n reaches the level m ₂ of e _s again, solution co-feeding is performed, and the same operation is continued at t ₃ , t ₄ , and so on. The curve shown by the dotted line C connecting the peak values of e _n shows the ideal limit curve for which the hardness should be controlled programmatically. By controlling the hardness along this line, high quality crystals can be maintained and the shortest operation One batch can be completed in one hour.

However, maintenance of such an ideal curve C can be realized when parameters such as the steam in the can, the degree of vacuum, and the purity of the solution are kept at certain values. If a disturbance such as a large change in the amount or a large change in the degree of vacuum occurs, it becomes difficult to maintain this ideal pattern for crystal growth.

For example, if the amount of steam drops abnormally after time _t4 , it will take a long time for the measured hardness value e _n to reach the next set value _m5 , and if the same setting method is continued, the hardness will decrease. The measured value changes as shown in e' _n , and the slope of the curve connecting the peak values becomes smaller like C', and it deviates significantly from C. If crystal growth is carried out under such conditions, the operating time for one batch will be significantly extended, and crystals are likely to occur, making it difficult to obtain high-quality crystal products.

On the other hand, if the amount of steam increases abnormally after t ₄ , the opposite phenomenon to the above will occur, the measured value of hardness will be like e″ _n , and the curve connecting the peak values will have a steep slope like C″. , significantly different from C, and abnormally early.
There is a drawback that the batch operation ends and the product becomes defective with many crystals.

The applicant solved the problems of the conventional program control method that uses step-like setting value changes, and proposed a control method that does not cause large deviations from the limit curve in response to disturbances. In Japanese Patent Application No. 59-137439 (Japanese Unexamined Patent Publication No. 61-15700), we proposed a limit zone control method that controls the hardness within the defined range.

The present invention aims to provide one of the concrete implementation means of this limit band control method which is a basic technology.

Hereinafter, prior to explaining the present invention, an outline of this limit band control method will be explained based on FIG. 3.

The time point when the measured value of hardness reaches the set level m ₁ of the set value e _s at time t ₁ will be explained as a representative example.
Let P ₁ be the peak point of the measured value e _n . Through experience through various actual operations, the applicant has confirmed that the limit curve is not a single limit curve, and that for each peak point of hardness, there is a region where the next peak point should be reached. This region is specified by a limit region R surrounded by two curves starting from P ₁ , that is, an upper limit curve C ₁ and a lower limit curve C ₂ . Strictly speaking, it was confirmed that there is an optimal pair of curves for each peak point among these two limit curves.

Therefore, when the hardness of the white bottom reaches a certain set value, two curves starting from that point are read out from the pre-programmed memory, and the next set value is changed programmatically based on these two curves. Then, by controlling the next hardness measurement value e _n so that its peak point falls within the region R, the hardness measurement value e _n
It becomes possible to maintain crystal growth within the limit range and proceed with crystal growth.

Next, a specific method of program control of the set value e _s will be explained. First, when e _n reaches the set value e _s1 (hardness m ₁ ) of the previous crystal growth cycle at P ₁ , the two curves C ₁ and C ₂ shown by dotted lines change to point P ₁ (time t ₁ , hardness
m ₁ ) as the starting point, the set value for the next crystal growth cycle is first set as a curve that monotonically increases with time along a curve e _s21 shown by a dashed line along the curve C ₁ . Point _Q on e s21 at the point when the stiffness changes by a constant value Δm from point P _{1 or after a certain time Δt has passed from point P 1 On} the horizontal straight line e _s22 where the set value maintains the stiffness m ₂ at ₂₁ is held constant along. When this straight line _es22 reaches the point _Q22 where it intersects the lower limit curve _C2 , the set value is set as a curve that monotonically increases with time along the lower limit curve _C2 . Q ₂₁ , Q ₂₂
Δm or Δt, which is the element that determines the point, is empirically set so that the predicted point of the next peak P ₂ of e _n falls on the straight line e _s22 connecting Q ₂₁ and Q ₂₂ .

By implementing such program settings for each peak point of e _{n ,} each peak point P ₁ ,
If the parameters inside the can are normal, P2 will always fall within the _limit region R determined for each peak point, so it is possible to obtain operational results equivalent to conventional program control along the limit curve. can. In Fig. 3, the operation in which the peak point P ₁ corresponds to the horizontal part e _s22 of the programmed set value e _s is performed in the conventional device by changing the set value e _s from m ₁ to m ₂ in a stepwise manner. The behavior is equivalent to .

Next, let us consider the case where the next peak point _P2 of the measured hardness value e _n deviates from the horizontal part e _s22 of the set value due to a disturbance and rises faster than the Q ₂₁ point. The hardness program setting is not stepwise as in the past, but is a curve that monotonically increases over time at e _s21 along curve C ₁ with values smaller than m ₂ , so the rising trend of e _n is different from the conventional one. Compared to the stepwise setting method
There is an upward trend with the C ₁ curve at a value lower than m ₂ as the upper limit, and a corrective action is added in the direction of lowering the next peak point P ₂ .

Conversely, if the next peak point P ₂ deviates from the horizontal part of the set value and rises later than the Q ₂₂ point, the stiffness program setting is set to a value greater than the level m ₂ of the Q ₂₂ point and curve C ₂ Since the _curve rises monotonically over time with _{e s23 along} There is an upward trend, and at the next peak point _P2 , a corrective action is added in the direction of raising it.

In this way, when the parameters inside the can are abnormal, the set value e _s monotonically increases due to the action of the curve parts e _s21 and e _s23 , so that the peak point of the measured hardness value e _n is located at the horizontal part e of the setting curve. _s22 , and each peak point is maintained slightly on the upper limit curve or lower limit curve, so crystal growth can proceed without the measured hardness value e _n falling outside the limit region R. This greatly reduces the large fluctuations in operating time and the occurrence of product defects, unlike in the past.

Since the above control method requires determining two limit curves for each peak point of the measured value e _n of hardness,
Since the algorithm for determining the curve based on the position of the peak point is somewhat complicated, it is more practical to set the upper limit curve and the lower limit curve approximately, and maintenance is easier.

Generally, as shown in Figure 4, the upper limit curve is created by dividing the time from crystallization to discharge into multiple sections T ₁ , T ₂ , etc. with respect to the ideal curves C ₁ and C ₂ . A practical method is to approximate the slope of the curve with representative straight lines D ₁₁ , D ₁₂ , . . . and use these straight lines as the upper limit curves by switching in each section.

An object of the present invention is to provide a practical method for similarly determining a lower limit curve by approximating the upper limit curve set in this way using a group of straight lines.

<Means for solving the problem> The feature of the method of the present invention is that in the automatic crystal growth of a crystal can in which the hardness of the white bottom is controlled by a program, when the hardness of the white bottom reaches a set value, the difference water or solution is is supplied to lower the hardness of the white bottom, and at the same time, determine the upper limit curve of the hardness control limit region starting from the above point and the lower limit curve with a constant deviation value from this upper limit curve. Then, the next set value after the above point is increased along the above upper limit curve, and when the set value changes by a constant value, the set value at that point is maintained after a certain period of time has passed, and the straight line representing the set value is The crystal can program control method is characterized in that the set value is changed in a programmatic manner so as to increase the set value along the lower limit curve after the point where the set value intersects the lower limit curve.

More specifically, the upper limit curve and the lower limit curve are approximated by straight lines.

<Operation> According to the method of the present invention, when the upper limit curve is determined, the lower limit curve is always determined with a constant deviation from the upper limit curve. Therefore, if the upper limit curve is approximated by a group of straight lines, the lower limit curve is also determined by a group of straight lines.

<Example> An example of the method of the present invention will be described based on FIG.

As shown in Fig. 4, the area to be grown is appropriately divided, and the initial value of the white undertone in the specific area is m ₁ ,
Let the final value of the white lower part be m _o . The time when the measured value of hardness reaches m ₁ is defined as t ₁ , the peak point P ₁ determined by t ₁ and m ₁ is the starting point, and first the upper limit curve or upper limit straight line D ₁
decide. The next set value after time t ₁ is given by e _s21 shown by a dashed dotted line along this upper limit curve or straight line D ₁ until the set value changes to Δm and reaches m ₂ .
When e _s21 reaches m ₂ at point Q ₂₁ , the set value becomes horizontal setting e _s22 that maintains the level of m ₂ . The time required to reach the _Q21 point from _P1 is expressed as Δt.

The feature of this embodiment is that the method for determining the upper limit straight line D ₁ is the same as in the case of FIG. 4, but the lower limit straight line is
It is located at a point defined by _{a straight line D 2 shifted} lower than D 1 by a constant deviation m ₀ . That is, settings with P ₁ as the starting point e _s21 , e _s22 , e _s23 and settings with P ₂ as the starting point
e _s31 , e _s32 , and e _s33 are completely similar to the method shown in FIG. 3, but each time a peak point is reached, only the upper limit straight line is determined, and the lower limit straight line D ₂ does not change.

In this example, the determination of Q ₃₁ points is determined by the hardness of P ₂ points.
A point on the upper limit curve or upper limit straight line D ₁ that takes a value m ₃ higher than m ₂ by Δm, but for a certain time Δt from point P ₂
It is also possible to determine the point on D ₁ after the elapsed time, and if the increase in hardness (m ₃ − m ₂ ) in that case is Δm′, then
Since Δm'>Δm, and the upper limit straight line D ₁ ' approaches D ₁ more, the number of divided regions from crystallization to discharge explained in FIG. 4 can be reduced. The horizontal setting and lower limit straight line in this case are the same as in the case of FIG.

The embodiment shown in FIG. 2 has shown a method of programming the hardness in a specific area of the crystal growth area, but as shown in _FIG . When divided by T ₂ , ...T _o , the upper limit curve or straight line D ₁₁ , D ₁₂ , ...D _1o in each section
takes the form of a combination of curves or groups of straight lines with gradually increasing slopes, and the stiffness in the entire region is program-controlled.

<Effects> As explained above, by using the method of the present invention, the following effects can be expected.

(1) Abnormal termination of the operating time, which occurs when the curve connecting the peaks of the hardness measurements in the white lower part deviates significantly from the limit curve based on parameter fluctuations such as steam, pressure, and purity of the solution in the crystallizer. This makes it possible to significantly reduce the occurrence of defective products.

It is often difficult even for extremely experienced operators to switch the set values from automatic to manual in response to parameter abnormalities in the can and correct the normal limit curve, resulting in products from that batch being rejected. Although there are many cases, according to the method of the present invention, as long as the variation in parameters within the can does not reach a fatal level, the occurrence of defective products can be prevented by automatic corrective action to the limit range. Therefore, even an inexperienced operator can operate the system, and the mental burden of monitoring the crystal cans, which conventionally required a skilled operator, can be significantly reduced.

(2) The method of the present invention uses a practical and simple method as shown in Fig. 2 to set the program.
Stable operation is possible by simply setting two straight lines for each specific area, and no complicated program settings are required, making it possible to realize the device economically.

[Brief explanation of drawings]

Fig. 1 is a general configuration diagram of a crystal growth device using a crystal can, Fig. 2 is an explanatory diagram of crystal growth by the method of the present invention, Fig. 3 is an explanatory diagram of the basic technology related to the prior application, and Fig. 4 is an upper limit curve. FIG. 5 is an explanatory diagram of an intermittent crystal growth method according to a conventional method. 1... Crystal can, 2... Heating section, 3... Solution valve,
7...White bottom, 9...Different water valve, S...Steam, F...
Solution, W... difference water, cooling water, 15... hardness meter, 1
6... Sequence control device, 161... Adjustment section,
162...Program setting section, 163...Valve operation section, _en ...Hardness measurement value, e _s ...Setting value, _D1 ,
D ₁ ′...Upper limit curve, _D2 ...Lower limit curve, R...Limit area.

Claims (1)

[Claims] 1. In automatic crystal growth of a crystal can in which the hardness of the white bottom is controlled by a program, when the hardness of the white bottom reaches a set value, differential water or a solution is supplied to the white bottom. Once lower the stiffness, determine the upper limit curve of the stiffness control limit region starting from the above point and the lower limit curve with a constant deviation value from this upper limit curve, and set the next setting after the above point. The value is increased along the above upper limit curve, and when the set value changes by a certain value or a certain period of time has passed, the set value at that point is maintained, and after the point when the straight line representing the set value intersects the above lower limit curve. A crystal can program control method characterized in that the set value is changed programmatically so as to increase the set value along the lower limit curve. 2. The crystal can program control method according to claim 1, wherein the upper limit curve and the lower limit curve are approximated by straight lines.