JPH0773518B2 - Crystal can program control method - Google Patents

Description

The present invention relates to improvement of controllability of a crystal can program control method.

<Prior Art> The structure of an automatic decoction device using a crystal can will be described with reference to FIG. A solution F to be infused is supplied into an upright crystal can 1 having a calandria type heating unit 2 through a conduit 3 and a control valve 4 into the can. The heating steam S is supplied to the pipe 5 and the control valve 6.
Is supplied to the heating unit 2 in the crystal can via the.

The solution is heated to evaporate and concentrated, and at the same time, the solution is replenished. To generate crystal nuclei suitable for each variety. After that, in order to prevent these crystal nuclei from binding to each other and generating new crystal nuclei (pseudocrystals) of undesired seeds, the conduit 9, control valve The difference water W is supplied via 10 or the solution F is supplied via the conduit 3 and the control valve 4 to continue the concentration and crystallization.

When the crystals grow to a certain extent, and the volume of crystals in the white area per unit volume exceeds a certain value, and the crystals come very close to each other, pseudo-crystals are relatively unlikely to occur, and the concentration is further increased. , When the crystal is grown easily and the solution is supplied, the volume in the can increases to a certain value, and the grain size of the crystal grows to the required size, the white bottom F is discharged from the discharge valve 11 to the outside of the can. . The discharged white powder is separated into crystals and a solution by a centrifuge, and the solution is repeatedly used for decoction again.

The vapor evaporated from underneath the white in the crystal can is drawn by the pump 13 through the condenser 12 and condensed. Reference numeral 14 is a cooling water supply pipe line to the condenser.

The degree of vacuum in the can, that is, the pressure, is constantly controlled by the air control valve 15 that controls the supply amount of the atmosphere A into the can.

Reference numeral 16 is a pressure sensor inside the can, and PV _P is a measured value thereof, which is guided to the control device 17. A control calculation is performed on the deviation between the measured value and the pressure set value SV _P, and the operation output MV _P is supplied from the control device 17 to the control valve 15 to control the pressure inside the can to SV _P.

18 is a rheometer for measuring the hardness of the under-white in the can, PV _R is its measured value, 19 is a level sensor for detecting the level of the under-white in the can, and PV _H is its measured value. These measured values PV _R , P
V _H is input to the controller 17.

MV _F and MV _W are operation outputs supplied from the control device 17 to the control valves 4 and 10 via the manual automatic switching devices 20 and 21, respectively.

A normal control method in such a configuration is shown in FIG.
As shown in (B), at the timing t ₁ when the measured value of hardness reaches the set value which is B ₁ point, as shown in (B), a certain time T
Open the period control valve 10 or 4 to supply the difference water or solution into the can, loosen the hardness once, and then concentrate, and the hardness reaches the set value higher than the previous set value at B ₂ point. When doing, perform the same operation and gradually raise the hardness and level to grow crystals.

In order to loosen the hardness by supplying water or a solution once, it is a spore that is closely related to crystal growth (a solute mass different from liquid and solid, and has both liquid and solid properties).
(Refer to SICE'86 July 23-25 Tokyo, ES11-4 for literature)
By increasing the growth rate up to the limit point of pseudo-crystal generation and breaking it down by supplying water or a solution, in order to enable the decoction to maintain the crystal rate at the maximum rate without generating pseudo-crystals. Yes, this is the basic method of so-called intermittent decoction.

<Problems to be solved by the invention> In the case of the intermittent sucrose system by intermittent supply of water or solution,
In order to concentrate to the next set value of hardness, heating energy for evaporating the supplied water is required. In order to avoid this energy consumption, the applicant has made a proposal in Japanese Patent Publication No. 60-1000 to perform an operation equivalent to supplying water or solution.

In this operating method, as shown in FIG. 3 (B), at a timing of t ₁ and t ₂ , an operation of raising to a SV _P2 higher by ΔP than the steady pressure set value SV _P1 for a certain period T is executed. Temporary pressure rise is, for example, normal pressure 700mmg 600mmg
As a result, the boiling point under white is increased by about 10 ° C., the degree of supersaturation under white is reduced, and an effect equivalent to the supply of differential water or solution is obtained.

However, the amount of spores closely related to crystal growth fluctuates due to the operation of rapidly changing the degree of vacuum inside the can.

That is, the phenomenon in which solutes form spores and the phenomenon in which solutes dissolve into solutes differ greatly between an unsteady small disturbance and a large disturbance forcibly given by changing the vacuum degree. The dynamics of the process fluctuates greatly, and a pressure control system that simply controls the opening and closing of the valve does not control the collapse of the sprouting well, resulting in a problem of poor controllability.

That is, generally, the ability of the vacuum pump and the ejector in the crystal can apparatus has only the ability necessary to maintain a predetermined vacuum value. Therefore, it is clear that if the above-mentioned control is carried out with an appropriate value for the tuning of proportional, integral, and derivative control, the growth and collapse control of the blast will not be carried out smoothly.

It is an object of the present invention to provide a control method that does not reduce the controllability with respect to the disturbance caused by such pressure change.

<Means for Solving Problems> A feature of the method of the present invention is that it has vacuum degree control means for controlling the degree of vacuum in the crystal can by operating the opening degree of the air control valve, and the When the openness of the can is opened above the steady opening every time the value reaches the set value, the solidity is restored to the above fixed value at the timing when the solidity below the white level is reduced to the fixed value. At this point, the program operation of the valve opening degree is performed to open the opening degree more than the steady opening degree and then return to the steady opening degree with a predetermined gradient.

<Operation> According to the present invention, the steady value is set at the timing when the hardness under the white drops to a constant value after the valve opening is once opened above the steady value in synchronization with the period in which the vacuum degree in the can is controlled to be lowered. Closed, and when the hardness underneath is restored to a certain value, it opens again above the steady value and then an operation to return to the steady opening with a predetermined gradient is performed, resulting in a gentle change in the vacuum recovery curve. Controlled.

<Example> As shown in FIG. 2 (B), in the zone a for controlling the pressure rise and the zone b for controlling the steady pressure, the valve opening degree of each zone is set to the second degree by the operation output MV _P from the controller 17. It is operated as shown in FIG.

That is, at time t ₁ , the internal pressure of the can opened from the steady opening d ₀ to d ₁ is increased from P ₁ to P ₂ . As a result, the operation of closing the valve opening from the steady opening is executed at time t ₃ when the measured value of the ometer drops from W ₁ at point B ₁ to W ₁ . As a result, the pressure inside the can begins to drop, and the hardness underneath is reversed in the upward direction, and W ₁
To the level of. At this time t ₃ , the valve opening is opened to an opening d ₂ (d ₂ <d ₁ ) higher than the steady opening, and then a predetermined gradient k
The operation for returning to the steady opening d ₀ is executed by. As a result,
The pressure in the can gradually decreases from time ₃ , returns to the steady value P ₁ at time t ₅ , and shifts to the b zone. By performing such a pressure control in the can, it is possible to solve the problem that the operation of changing the pressure in the can affects the spore formation and the mechanism of collapse as a disturbance.

Although crystal growth has been considered to be a control of supersaturation in the theory until recently, it is theoretically being demonstrated that it is due to the mechanism of growth and disintegration of blastula. As described above, the spores are neither liquid nor solid, but an intermediate substance having both properties. Although the disruption and division of the spores can be performed with a water difference, the same effect can be obtained by the division with a vacuum as in the present application, and thus an energy-saving crystal growth can be achieved as compared with a water difference control.

The structure of the pressure control system inside the can is the control device as shown in the figure.
In addition to the configuration in which the opening of the control valve is directly set by the arithmetic output of the microcomputer in 17, a single controller may have a configuration in which the pressure set value is changed from the control device side. However, in general, the ejector and vacuum pump capacity for vacuum setting are not constant in each factory, and the dynamics when breaking the vacuum and when pulling the vacuum are different, so an appropriate valve opening is set for each action of the control valve. The controllability is better when operated directly from the control device 17 side.

It is also possible to control both the vacuum adjustment by the control valve 15 and the differential water and solution supply, but in that case the differential water and solution supply amounts are very small, so the vacuum is returned to the steady state b zone. As shown in FIG. 2, it is desirable that the operation program should be gently changed according to a constant slope, polygonal line, or curve. That is, the control of growth and collapse of the spore is a kind of catastrophe phenomenon, and the operation with a gradient, rather than the rapid change control, is highly safe.

<Effects of the Invention> As described above, according to the present invention, the opening of the air control valve during the period of changing the degree of vacuum in the can changes the pressure to control the growth and collapse of spores. It becomes possible to operate without causing any disturbance, and the controllability can be remarkably improved.

[Brief description of drawings]

FIG. 1 is a block diagram of a crystal can control device to which the method of the present invention is applied, FIG. 2 is an operation explanatory diagram thereof, and FIGS. 3 and 4 are operation explanatory diagrams of a conventional control method. 1 ... Crystal can, 2 ... Heating part, 3 ... Solution supply line, 4
...... Solution control valve, 5 …… Steam supply line, 6 …… Steam control valve, 7 …… Sucrose feeding device, 9 …… Diffusion water supply line, 10 …… Diffusion control valve, 11 …… Discharge Valve, 12 ... condenser, 13 ... vacuum pump, 14 ... cooling water supply line, 15 ... air control valve,
16 …… pressure sensor, 17 …… control device, 18 …… rheometer, 19 …… level sensor

Claims (1)

[Claims] 1. A vacuum degree control means for controlling the degree of vacuum in a crystal can by operating the degree of opening of an air control valve, wherein the degree of opening of the can is adjusted each time the hardness of the white bottom in the can reaches a set value. After opening from the steady opening, close the steady opening at the timing when the solidity below the white drops to a certain value, and open again from the steady opening when the solidity recovers to the certain value. A crystal can program control method characterized by executing a program operation of a valve opening for returning to a steady opening with a gradient.