JPH0514559B2 - - Google Patents

Description

Detailed Description of the Invention <Related Technical Field> The present invention relates to an automatic crystallization method for obtaining crystals of a target substance from a solution or suspension containing the target substance, and relates to an automatic crystallization method for obtaining crystals of a target substance from a solution or suspension containing the target substance. However, significant effects can be expected by applying the method of the present invention when a desired crystal is obtained by concentrating and crystallizing a solution or suspension. This type of crystallization method is generally applied to the crystallization of organic substances, such as monosodium glutamate, lysine,
It can be applied to amino acids such as proline, organic acids such as citric acid and malic acid, antibiotics, and others.

<Prior art> Figure 1 is a conceptual diagram of an automatic crystallizer in a crystal can.
1 is a crystal can, 2 is a heating section provided at the bottom of the crystal can, S is heating steam supplied to this heating section 2,
3 is the crystallization slurry in the can, 4 is a hardness meter that measures the hardness (flow rate) of the crystallization slurry, 5 is a level meter that measures the level of the crystallization slurry, 6 is a stirring blade, and 7 is a stirrer. An electric motor is used to drive the stirrer, and 8 is a supply control valve for the solution F supplied into the can.

Reference numeral 9 denotes a sequence control device, which controls opening and closing of the liquid supply valve 8 based on measurement signals e _M and e _L from the hardness meter 4 and level meter 5. Although not further illustrated,
A differential water supply control valve for controlling differential water into the can is also provided, and its opening and closing is controlled by a sequence control device.

The crystallization method in the crystal growth process based on the measured value of the hardness meter is to supply differential water or solution every time the measured value of hardness reaches the programmed set value, and after loosening the hardness at the bottom, Concentration and crystallization continues, and when the hardness reaches a set value that is a certain value higher than the previous set value, water or solution is supplied again to loosen the hardness of the slurry, and the level in the tube is reduced. Concentration ends when reaches a certain value. Generally, difference crystallization is performed in the first half of the crystal growth process, and liquid crystallization is performed in the second half, but operations in which both are performed alternately are also performed.

Figure 3 shows a comparison of program control of hardness in the concentration crystallization stage of sugar and glutamic acid.
Glutamic acid, shown by the solid line, requires an operation to gradually increase the hardness in a relatively soft range of hardness M ₁ to _{M 2} . On the other hand, for sugar shown by the dotted line, the hardness
An operation is performed to increase the stiffness with a fairly steep slope in the relatively hard region M ₃ to _{M 4} .

Figure 4 is a partially enlarged view of the program control of hardness in crystallization of sugar solution, as shown in A.
When the measured value e _M of hardness reaches the set value of _M3 , as shown in B, the liquid supply valve 8 is opened for a certain period of time to supply the solution, and after the hardness has been loosened, concentration crystallization is continued, and the time
When the set value _M4 , which is higher than the previous hardness set value _M3 by ΔM, is reached at _t2 , the solution is supplied again for a certain period of time, and the same operation is repeated.

In the case of sugar refining, the hardness setting gradient is quite steep, and the value of ΔM is the hardness measurement value e _M due to disturbance etc.
Since the fluctuation is sufficiently large compared to the fluctuation of eM, no problem occurs even if the opening and closing of the liquid supply valve 8 is controlled based only on the level change of _eM .

However, in the purification of amino acids, etc., as mentioned above, it is necessary to control the liquid supply valve in a region where the change in the measured value e _M of hardness is small, ΔM becomes small, and noise such as disturbance _etc. There is a risk of erroneous operation if superimposed on the Also, the hardness meter has a structure that measures hardness by rotating a blade inside the can and using the reaction force.
If a cluster of crystals hits the blade as the slurry flows in the can using the stirrer, the measured value e _M will temporarily fluctuate. If this variation exceeds ΔM, malfunctions also occur, and the operation becomes extremely unstable, making it difficult to achieve program control of consistency similar to that used in sugar refining.

<Object of the Invention> The present invention focuses on level changes in a crystal can and provides a control method that solves conventional problems by controlling solution supply based on changes in hardness and level. do.

<Structure> The feature of the method of the present invention is that in an automatic concentration crystallization method that repeats the operation of supplying a solution every time the hardness of the slurry reaches a certain value to temporarily loosen the hardness, the measured value of the hardness is The point is that the next solution supply is executed when the level in the can increases by a predetermined value from the previous set value and decreases by a predetermined value from the level at the time of the previous solution supply.

<Example> Functions according to the method of the present invention will be explained with reference to a functional block diagram in the sequence control device 9 shown in FIG. 91 is a hardness setter that programmatically supplies a hardness set value e _MS higher than the previous set value by ΔM, and 92 compares the set value e _MS with the measured hardness value e _M , e _M ≧ Comparator that sends output e _MO when e _MS , 9
3 receives the measured value e _L of the slurry level in the can, and the change in this e _L from the previous maximum value is set at 94 . The comparator 95 sends the output e _LO when the drop exceeds ∆L, that is, ∆e _L ≦ ∆L, and the comparator 95 opens the liquid supply valve 8 for a certain period of time when e _MO and e _LO are sent, and the solution is poured into the can. It is a solution valve control means that sends out a supply signal e _VO .

FIG. 2 is an explanatory diagram of the operation of automatic crystallization according to the method of the present invention. As shown in A, at time t ₁ when the measured value e _M of hardness reaches the set value M ₁ , the measured value e _L of the level inside the can decreases by more than Δ _L than the previous maximum value, as shown in B. If so, open the liquid supply valve 8 as shown in C.
is opened and the solution is supplied for a certain period of time. As a result, the fluidity of the slurry decreases, so the measured hardness e _M temporarily decreases. On the other hand, the level e _L inside the can rises by the amount of solution supplied. After the solution is supplied, the solidity increases again due to concentration crystallization, and the level of the crystallized slurry in the can becomes lower than the level at t ₂ immediately after the solution is supplied. At time t ₃ , when the measured value of hardness reaches M ₂ which is higher than the previous set value M ₁ by ΔM, if the drop in the level e _L in the can is more than ΔL, the solution is supplied again, and so on. operation is repeated.

In this way, in the method of the present invention, the solution is supplied only when both the consistency of the measured hardness value with the set value and the change in the level in the can are satisfied, so that the measured value of the hardness meter is Erroneous operations caused by superimposed noise can be completely eliminated.

<Effects> According to the method of the present invention, it is possible to completely automate the concentration crystallization of amino acids, etc., which has been considered difficult in the past.

The method of the present invention is basically program control based on the measured value of a hardness meter, and is the same method as the program control using a hardness meter in sugar crystallization.
Significant sharing of sequence control devices becomes possible.
The functions of the sequence control device are actually realized in software using a computer, so by making slight changes to the software, it is possible to share the same device for both systems, which has great economic effects. be.

As described above, in the method of the present invention, when the relationship between time and hardness as shown in FIG. If applied in cases where it is difficult to accurately capture changes, it can be expected to have an extremely large effect.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an automatic crystallizer crystallizer to which the method of the present invention is applied, Fig. 2 is an explanatory diagram of its operation, Fig. 3 is a comparison diagram of hardness control of glutamic acid and sugar, and Fig. 4
The figure is an explanatory diagram of the operation of program control of the hardness of sugar by sugar liquid crystallization. 1... Crystal can, 2... Heating section, 3... Crystallization slurry, 4... Hardness meter, 5... Level meter, 6... Stirrer, 8... Solution supply control valve, 9... Sequence control device, F...solution, S...steam.

Claims (1)

[Claims] 1 In an automatic concentration crystallization method that repeats the operation of supplying a solution and temporarily loosening the hardness each time the hardness of the crystallization slurry reaches a certain value, the measured value of hardness is lower than the previous set value. A method for automatic crystallization using a crystal can, characterized in that when the level of the crystallizing slurry in the can increases by a predetermined value and decreases by a predetermined value from the level at the time of the previous solution supply, the next solution supply is executed.