JPS6365318B2 - - 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 treatment using a vacuum crystal can, for example, as shown in FIG. 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 it reaches a crystallization concentration that allows crystal precipitation, seed sugar is added to the solution from the injector through the valve 6 to prepare each variety. Generate suitable crystal nuclei. After that, in order to prevent these crystal nuclei from combining with each other and from generating new crystal nuclei of undesired species (pseudo-crystals), add water or a solution while monitoring the inside of the can. Continue concentration and crystal growth. 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 matter to an appropriate value during crystal growth, solution F can be supplied into the can 1 through the differential water valve 9 or the solution valve 3, and the condition inside the can 1 can be monitored through the peephole 10. be able to. The steam in can 1 is passed through valve 1 to condenser 11.
2 by a vacuum pump 13, 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 denotes a valve operation unit that controls opening and closing of the solution valve 3 or the differential water valve 9 based on the output of the adjustment unit 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) shows 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) shows the opening/closing status of the solution valve 3.

At time t ₁ , the measured value e _n increases and the hardness setting value
The solution is supplied when the level of m ₁ of e _s is reached, so that 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 . The solution is supplied at time t ₂ when e _n reaches the level m ₂ of e _s again, 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. 4. time
At t ₁ , the measured value of hardness is at the set level of set value e _s
The time when m ₁ is reached 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 as a limit region R surrounded by two curves starting from point _P1 , that is, an upper limit curve _C1 and a lower limit curve _C2 . 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 lower white reaches a certain set value, two curves starting from that point are read out from the pre-programmed memory.
By programmatically changing the next setting value based on these two curves and controlling the peak point of the next measured value e _n to fall within the region R, the measured value e It becomes possible to advance the decoction while maintaining _n within the limit range.

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. 4, 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 that crystallization can proceed without the measured value e _n of hardness 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 5, the upper limit curve is created by dividing the time from crystallization to sugar drop into multiple sections T 1 , T ₂ , ... with respect to the ideal curves C ₁ and C 2 , and dividing the time from crystallization to sugar drop into multiple sections T ₁ , T ₂ , ... A practical method is to approximate the slope of the curve with representative straight lines D ₁₁ , D ₁₂ , .

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 At the same time, the upper limit curve of the hardness control limit region starting from the above point is determined, and the next set value after the above point is set to the above upper limit curve. When the set value changes to a certain value or after a certain period of time has elapsed, the set value at that point is held, and the holding time is regulated to a certain value, and when a certain period of time has elapsed, the lower limit straight line is determined. The crystal can program control method is characterized in that the set value is changed programmatically along this lower limit straight line.

More specifically, the slope of the lower limit straight line is calculated based on the time Δht' required to increase the set value by Δm along the upper limit curve, the time t ₀ to maintain the set value at a constant value, and the constant value Δm. or the above based on the increase value Δm' of hardness when the set value is increased for a certain time Δt along the above upper limit curve, the time t ₀ for holding the set value constant, and the above fixed time Δt. It is characterized by determining the slope of the lower limit straight line.

<Operation> According to the method of the present invention, the set value of the hardness changes at a constant value along the upper limit curve, or the set value at the time point when a certain period of time has elapsed is maintained for a certain period of time thereafter. The slope of the straight line approximating the lower limit curve is determined based on this constant holding time t ₀ and the time Δt′ required for the constant stiffness change Δm along the upper limit curve or the set value change Δm′ during the elapse of a certain time Δt. be done.

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

As shown in FIG. 5, 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 _t1 is given by e _s21 shown by a dashed dotted line along this upper limit curve or straight line _D1 until the set value changes by Δm and reaches _m2 . When e _s21 reaches m ₂ at point Q ₂₁ , the set value is held constant and becomes the 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 first feature of this embodiment is that the time for maintaining the horizontal setting e _s22 is set to a constant value t ₀ . Therefore, point Q ₂₂ , which is reached after t ₀ has elapsed from point Q ₂₁ , is expressed as (t ₁ +Δt+t _{0 )} , where t 1 is the time of P ₁ .

The second feature of this embodiment is that the lower limit curves D ₂ , D ₂ ′,
It lies in the method of determining... First, the first lower limit curve D ₁ is a straight line that starts from point P ₁ and connects point P ₁ and point Q ₂₂ .
D ₂ and its slope is Δm/(Δt+t ₀ ). Along the infinite straight line defined in this way, e _s23
is set.

Program setting for the next cycle is performed starting from the peak point _P2 formed at time _t2 when the measured value e _n of hardness falls within one of e _s21 to e _e23 . For subsequent program settings, the methods for determining the upper limit straight line and the lower limit straight line are divided into two depending on whether the standard is a constant increase in hardness Δm from the peak point or the constant elapsed time Δt from the peak point.

Figure 2 illustrates the case where a constant increase in hardness Δm is used as the standard, and the hardness is higher than m ₂ by Δm on the upper limit curve or straight line D ₁ starting from point P ₂ .
The point where m ₃ is taken is Q ₃₁ point. The straight line D ¹ ′ connecting the P ₂ points and the Q ₃₁ point becomes the second upper limit straight line, and e _s31 is set along this line. The time required from point P ₂ to point Q ₃₁ is expressed as Δt′. Q ₃₁ Horizontal setting from ′ point
Similar to e _s22 , e _s32 is set to a certain time t ₀ . If the point after t ₀ has elapsed from the Q ₃₁ point in e _s32 is the Q ₃₂ point, then the lower limit straight line D ₂ ′ is defined by the straight line connecting P ₂ and Q ₃₂ point,
e _s33 will be set along this straight line.

Next, FIG. 3 shows an embodiment in which a constant elapsed time Δt is used as a reference. In this case, Δt from P ₂ points
_{The point} on _the upper limit curve or upper limit straight line D ₁ at the time when Since the upper limit straight line approaches _D1 every cycle, the number of divided regions from crystallization to discharge can be reduced. The horizontal setting and the method for determining the lower limit straight line are the same as in the case of FIG. 2 where Δm is constant.

The embodiments shown in FIGS. 2 and 3 above have shown a method for setting a program for the hardness in a specific region of the crystal growth area, but as shown in FIG. Sections T ₁ , T ₂ ... When divided by T _o , the upper limit curve or straight line D ₁₁ , D ₁₂ ,
..., D _1n takes the form of a curve with gradually increasing slope or a combination of a group of straight lines, 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 box significantly deviates from the limit line, 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 to correct normal values to the limit line, and the products of that operation batch may be marked as defective. However, according to the method of the present invention, as long as the parameter fluctuations inside the can do not reach a fatal level, it is possible to prevent the occurrence of defective products by automatically adjusting 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) By using a realistic and simple method as shown in Figures 2 and 3, program settings can be made by simply setting two straight lines for each specific area, and stable operation is possible. No configuration is required and the device can be implemented economically.

[Brief explanation of drawings]

Fig. 1 is a general configuration diagram of a crystal growth apparatus using a crystal can; Fig. 2 is an explanatory diagram of crystal growth according to the method of the present invention; Fig. 3 is an explanatory diagram of crystal growth according to another embodiment of the method of the present invention; Figure 4 is an explanatory diagram of the basic technology related to lost applications, Figure 5
The figure is an explanatory diagram of the method for determining the upper limit curve, and FIG. 6 is an explanatory diagram of intermittent crystal growth using the 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 operating section, _en ...Hardness measurement value, e _s ...Set value, _D1 ,
D ₁ ′... Upper limit curve, D ₂ , D ₂ ′... Lower limit curve, R...
marginal area.

Claims (1)

[Scope of 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 solute solution is supplied to While lowering the lower stiffness once, determine the upper limit curve of the stiffness control limit region starting from the above point, and increase the next set value after the above point along the above upper limit curve to maintain a constant value. When the set value changes or after a certain period of time has elapsed, the set value at that point is held, and the holding time is regulated to a certain value, and when a certain period of time has elapsed, a lower limit straight line is determined, and from then on, the set value is set along this lower limit straight line. A crystal can program control method characterized by programmatically changing. 2. A patent claim in which the slope of the lower limit straight line is determined based on the time Δt' required to increase the set value by Δm along the upper limit curve, the time t ₀ for maintaining the set value at a constant value, and the constant value Δm. The crystal can program control method according to scope 1. 3 The set value is maintained for a certain period of time Δt along the above upper limit curve.
The crystal can program according to claim 1, which determines the slope of the lower limit straight line based on the increase value Δm' of hardness when the hardness is increased, the time t ₀ for holding the set value constant, and the fixed time Δt. control method.