JPS6028802A - Controlling method of discharge of slurry in crystallizer - Google Patents

Abstract

PURPOSE:To control freely the discharge of a slurry from a crystallizer by keeping the flow rate of the slurry sent to a centrifugal separator constant, and controlling the return of the mother liquor in accordance with the concn. of the slurry in the crystallizer. CONSTITUTION:The slurry contg. crystal particles, flowing down along the outer circumference of a draft tube 2 in a crystallizer 1, is introduced into a classifying leg 6, wherein the particle diameters are classified. Then the slurry is supplied into a centrifugal separator 16 through a slurry discharge pipe 13 and a slurry discharge pump 14, and the crystals are taken out from a line 17. When the concn. of the slurry in the crystallizer 1 is low, the opening of a throttle valve 19 is increased through a slurry concn. detector 20 and a discharge regulator 21, and the mother liquor separated from the centrifugal separator 16 is allowed to flow into the suction side of said pump 14 through a return pipe 18 to reduce the discharge of the slurry from the classifying leg 6. When the concn. of the slurry in the crystallizer 1 is high, the opening of the throttle valve 19 is decreased to increase the discharge of the slurry from the classifying leg 6.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a crystallization method that is widely used in various organic and inorganic chemical industries such as fertilizers, foods, and pharmaceuticals, and in particular involves extracting a slurry after concentration from a crystallization can. Slurry removal from crystal can ffi II
This relates to the a11 method.

DTi type ([) rart T' ube alld
Bable (forced circulation type) crystallization apparatus has a draft tube erected in the crystallizer for raising the solution in the crystallizer, and a settling area is formed by a baffle tube around the outer circumference of the draft tube. After being heated, the processing solution is supplied to the lower part of the crystallization vessel, and while rising in the draft tube, it is evaporated and reduced by RIIA, and falls from the outer circumference of the draft tube, and those with large crystal particles are extracted as a concentrated slurry from the classification leg. The solution containing fine particles is taken out from the settling zone, heated again, and then forcedly circulated into the crystallization vessel.

The concentrated slurry extracted from the classification leg is then centrifuged into 1
Solid-liquid separation is performed using 11 tlN, and the solid fraction is recovered as crystals. Normally, in order to control the concentration of crystals precipitated in the crystal can, it is necessary to drain the amount of slurry extracted, but if the slurry concentration in the crystal can is low, the discharge of the extraction pump should be adjusted to reduce the amount of slurry extracted. If the amount is reduced by restricting the amount with a throttle valve, the flow rate of the slurry in the piping leading to the centrifuge will decrease, causing problems such as crystals in the slurry settling in the piping and blocking the throttle valve, which will hinder the classification. Control the amount of slurry extracted from the legs as you wish! I can't do it.

An object of the present invention is to make it possible to freely control the amount of slurry extracted from a crystal can.

The present invention extracts slurry from a crystal can, centrifuges it, and crystallizes it.
In method 1, the mother liquor separated by centrifugation is returned to the slurry extraction pump, and the amount of mother liquor returned in step (a) is controlled according to the slurry concentration in the crystallization vessel, so that the centrifuged mother liquor is By returning the slurry to the suction side of the slurry withdrawal pump, the flow rate of the slurry sent to the centrifugal separator is kept constant, and the amount of the mother liquor withdrawn can be freely controlled by controlling the amount of returned slurry according to the slurry 11j in the crystal can. It was designed so that it could be controlled.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the method for controlling the extraction of slurry in a crystal can according to the present invention will be described below with reference to the accompanying drawings.

In the figure, 1 is a DTB type crystal can, in which a draft tube 2 is erected in the center, a baffle tube 3 is provided on the outer periphery of the draft tube, and a settling region 4 is formed between the baffle tube 3 and the inner wall of the can. Ru. Below the draft tube 2, there is a
J'l' 115 is provided, a classification leg 6 is provided on the sloped wall of the lower part of the crystal can 1, and a vapor discharge lower is provided in the upper part of the crystal can 1.

Reference numeral 8 denotes a heater, and reference numeral 9 denotes a circulation pump, which are each connected to the circulation line 10 and take out the liquid in the crystal can 1 from the settling area 4, and return the liquid to the lower part of the crystal can 1 through the circulation pump 9 and the heater 8. , circulate. 11 is the stock solution supply pipe, and heater 8
and a circulation line 10 between the circulation pump 9 and the circulation pump 9. An auxiliary pump 12 is connected to the circulation line 10, and the classification leg 6
Supply liquid for classification.

A slurry extraction pipe 13 is connected to the classification leg 6, and a slurry extraction pump 14 is connected to the slurry extraction pipe 13. A slurry supply pipe 15 on the discharge side of the slurry extraction pump 1 is connected to a centrifuge 16 .

The solid fraction centrifuged in centrifugal fraction Il1 machine 16 is transferred to line 1.
7, and the mother liquor is connected to the slurry extraction pipe 13 via a mother liquor return pipe 18. A throttle valve 19 such as a die 17 flam valve is connected to the mother liquor return pipe 18 .

A slurry concentration detector 20 is installed in the crystal can 1, and its signal is input to a slurry withdrawal amount regulator 21.
The opening degree of the throttle valve 10 is adjusted by the output signal 22 from the extraction sum adjuster 21.

Next, the present invention will be explained in detail based on the apparatus having the above configuration.

The liquid in the crystal can 1 rises in the draft tube 2, evaporates there, concentrates, grows crystals, and descends around the outer periphery of the drum 71-tube 2. The liquid and minute crystal components are taken out from the retring zone 4, heated by a heater 8, and circulated into the crystal canister 1. The slurry containing crystal particles descending on the outer periphery of the trough + tube 2 enters the classification leg 6, where the particle size is classified, and then supplied from the slurry extraction pipe 13 to the centrifugal part m1vA 16 through the slurry extraction pump 14, There, it is centrifuged and the crystals are removed through line 17.

When the slurry concentration in the crystal can 1 is low, circulation is repeated to grow crystals and the amount of slurry extracted is reduced.
By increasing 1Ft1 degree of the throttle valve 19 via the regulator 21, the mother liquor separated from the centrifuge 16 is allowed to flow through the return pipe 18 to the suction side of the slurry extraction pump 14, and the slurry is extracted from the classification leg 6. The amount of slurry can be reduced, and since the extracted slurry flows through the slurry supply pipe 15 together with the mother liquor, its flow rate is kept constant and crystals do not settle within the pipe 15.

Further, when the slurry concentration in the crystal can 1 is high, the opening degree of the throttle valve 19 is reduced by the withdrawal amount regulator 21, so that more slurry can be withdrawn from the classification leg 6.

By appropriately returning the mother liquor separated by the centrifugal unit 18 to the suction side of the slurry extraction pump 14, the discharge amount of the slurry extraction pump 14 can be maintained constant, and the amount of slurry extraction can be freely adjusted. It becomes possible.

The mother liquor passed through the centrifugal valve 111 is not returned to the suction side of the slurry extraction pump 14, but is instead returned to the stock solution supply pipe 11 as appropriate. In addition, in the above embodiment, D is used as a crystal device.
Although the TB type is used as an example, forced circulation type (F, C
, ) Of course, it can also be used in crystal devices.

As is clear from what has been described in detail above, the present invention exhibits the following excellent effects.

(1) By returning the centrifuged mother liquor to the suction side of the slurry extraction pump and adjusting the amount, it is possible to control the amount of slurry extraction while keeping the discharge amount of the extraction pump constant.

(2) Since the discharge interval of the extraction pump can be kept constant, even if the amount of slurry extracted is small, crystals will not settle in the pipe leading to the centrifuge and will not be sipped.

(3) Since the amount of mother liquor returned can be controlled according to the slurry concentration in the crystal can, the concentration in the crystal can can be optimally controlled.

[Brief explanation of drawings]

The attached drawings are seven views showing one embodiment of the method for controlling the amount of slurry withdrawn from a crystal can according to the present invention. In the figure, 1 is a crystallization can, 13 is a slurry extraction pipe, 14 is a slurry extraction pump, 1G is a centrifugal separator, 18 is a mother liquor return pipe, and 22 is a slurry extraction regulator. Patent applicant: Ishikawajima-Harimaju] - Nobuo Kinuya, patent attorney at Gyogyo Co., Ltd.

Claims (1)

[Claims] In a method for controlling the amount of slurry withdrawn from a crystal can, in which slurry is extracted from the crystal can and centrifuged to recover crystals, the mother liquor separated by the centrifugation is returned to the suction side of the slurry withdrawal pump, and the returned amount of the mother liquor is controlled as described above. A method for controlling the amount of slurry withdrawn from a crystal can, characterized in that the amount of slurry withdrawn from a crystal can is controlled according to the slurry 81rt1 in the crystal can.