JPH07136495A - Continuous production of hardly water-soluble salt - Google Patents

Abstract

PURPOSE:To stably produce a hardly water-soluble salt suitable for extender pigment and having a uniform particle size by forming a hardly water-soluble salt by reacting an unreacted raw material with a new raw material in the supply line to a reactor and supplying the same as a seed crystal. CONSTITUTION:In a method for producing a hardly water soluble salt by continuously introducing two or more kinds of raw materials (a), (b) into a tubular reactor 6, the hardly water-soluble salt obtained by reacting the unreacted raw material contained in a mother liquor with a new raw material while the mother liquor is circulated is supplied to the reactor 6 as a seed crystal to uniformize the generation of a nucleus and the growth of a crystal. At this time, a bypass line allowing a raw material soln. containing the seed crystal to pass as it is and a filtrate line removing the seed crystal through a solid- liquid separator are provided and, by controlling the amt. of the soln. passed through both lines, the supply amt. of the seed crystal is suitably controlled. By this constitution, the hardly water-soluble salt crystal having a desired particle size is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for stably producing a poorly water-soluble salt having a uniform particle size suitable for extender pigments, cosmetics, photographic emulsions, electronic materials and additives.

[0002]

2. Description of the Related Art When two or more kinds of raw material solutions are mixed and reacted to synthesize a poorly water-soluble salt, it is known that crystals exhibit various shapes and particle sizes depending on the synthesis conditions.
For example, according to Bull. Chem. Soc. Japan No. 3 page 121, the barium sulfate crystals produced depending on the concentration of the mixed raw materials are variously deformed into amorphous, spherical, spindle-shaped, diamond-shaped, etc., and their sizes. Is 0.013 μm to 2.0 μm
It has been shown to vary significantly to the extent.

That is, since the sparingly water-soluble salt has a very low concentration range of generation of crystal nuclei and crystal growth as compared with the easily water-soluble salt, the degree of supersaturation greatly varies due to some fluctuations in the feed rate of the raw material solution. As a result, the particle size and shape of the crystal change, and it is difficult to obtain a crystal having a uniform size. Therefore,
A method of adding a seed crystal can be considered in order to obtain a crystal with a uniform particle size and shape. This is because the presence of the seed crystal facilitates the nucleation on the seed crystal, so that the nucleation occurs at a lower supersaturation state than when there is no seed crystal, and the generated nuclei are uniform. It is considered that the crystal growth becomes possible under the condition. In other words, it is considered that the presence of the seed crystal promotes crystallization under a mild state, so that the crystal grain size and shape become uniform.

As means for solving the above problems, there are those disclosed in Japanese Patent Application Laid-Open No. 3-205314, Japanese Patent Publication No. 61-34841, and Japanese Patent Publication No. 4-48730.
In these methods, a slurry containing crystals is extracted from a crystal can (crystallization part), sieved, and then fine particles are continuously returned to a crystal can as seed crystals together with a mother liquor.

At this time, a problem is how to control the supply amount of the seed crystal. In the above case, in the means for controlling the seed crystal supply amount, since it is a water-soluble salt, it is possible to control the seed crystal amount by dissolving the seed crystal by means of adding water to reduce the salt concentration or by heating to increase the solubility. The way to do is taken. However, with a poorly water-soluble salt like this case, it is almost impossible to dissolve the seed crystal by adding water to reduce the salt concentration or by heating to increase the solubility, and there is no other effective means. The means for controlling the amount of seed crystals is also extremely limited.

Further, Japanese Patent Publication No. 54-22200 discloses a continuous production method of barium carbonate which is a poorly water-soluble salt. In this invention, seed crystals are formed in a spiral reactor, and crystals are grown in a stirring reactor to produce barium carbonate having a desired particle size. However, in this method, the only factor that determines the seed crystal amount is the gas-liquid contact efficiency in the spiral reactor, and when the seed crystal amount must be greatly increased, the pipe length is increased and the residence time is increased. There is no other way but optimization of reaction conditions is very difficult. Furthermore, it is difficult to make the gas-liquid contact efficiency even and uniform in the spiral reactor and to increase the tube diameter, and this poses a very difficult problem in scale-up.

[0007]

Therefore, it has been desired to develop a method for producing a poorly water-soluble salt having a uniform particle size by controlling the amount of seed crystals in the production of the poorly water-soluble salt. An object of the present invention is to provide a method for stably producing a poorly water-soluble salt having a uniform particle size suitable for extender pigments, cosmetics, photographic emulsions, electronic materials, additives and the like.

[0008]

The summary of the present invention is as follows.
A method for producing a sparingly water-soluble salt by mixing two or more kinds of raw materials into a mother liquor containing any of the raw materials, continuously supplying the mixture to a tubular reactor, and mixing and reacting in the reactor. The product slurry in which the poorly water-soluble salt discharged from the reactor is dispersed in the mother liquor is sieved, and the mother liquor containing the unreacted raw material obtained is circulated so that the mother liquor is circulated again to the reactor. To a continuous production method of a poorly water-soluble salt, which comprises reacting the unreacted raw material with a new raw material in a feed line to produce a poorly water-soluble salt and supplying the poorly water-soluble salt to a reactor as a seed crystal. .

In the present invention, as a mode of supplying seed crystals, a mother liquor containing unreacted raw materials obtained by sieving a product slurry in which a poorly water-soluble salt discharged from the reactor is dispersed in the mother liquor is put into the reactor. This is a method in which the unreacted raw material is reacted with a new raw material while the mother liquor is circulated so as to be supplied again, and the resulting sparingly water-soluble salt is supplied to the reactor as a seed crystal (FIG. 2). This method eliminates the waste of discharging the mother liquor and, in addition, does not need to discharge the unreacted raw material contained in the mother liquor as it is to the outside of the system, which is advantageous in terms of energy saving and environmental cleanliness. Become. Further, in this method, a seed crystal is generated by the reaction between an unreacted raw material and a new raw material, and therefore it is not necessary to include the seed crystal in the circulating mother liquor, and the presence or absence of the seed crystal in the mother liquor is not limited.

In the present invention, one of the starting materials is contained in an appropriate amount in the mother liquor in the mother liquor tank (both or one side) at the start of the reaction so that the product slurry discharged from the reactor contains unreacted starting materials. I will let you. However, at this time, if the mother liquor in both mother liquor tanks contains the unreacted raw material and the content concentrations are equal, the content concentration of the unreacted raw material is constant and stable even after the reaction for a long time. Various reactions can be performed.

Further, when the mother liquor in both mother liquor tanks contains unreacted raw material and the concentration is different, or when the mother liquor in one mother liquor tank contains unreacted raw material, Since the content of the unreacted raw material changes from moment to moment, it is desirable to carry out a stable reaction by means such as means for controlling the ratio of the liquid feed amount in the fill tray line / bypass line, which will be described later. However, since the mother liquor containing the unreacted raw material is circulated in both mother liquor tanks, the content of the unreacted raw material in the mother liquor in both mother liquor tanks is finally equal. That is, the same state as in the above case is obtained.

At this time, the content of the excessive unreacted raw material, in other words, the content of the unreacted raw material contained in the mother liquor obtained by sieving the product slurry discharged from the reactor is changed. Thus, the amount of seed crystals can be easily changed, and a poorly water-soluble salt having a desired average particle diameter can be obtained.

Further, when the raw material is dissolved in the same solvent as the mother liquor and supplied as a raw material solution, or when a by-product (for example, generated water) from the reaction is produced, the reaction is carried out for a long time, that is, When recycled again, the mother liquor is diluted with the solvent and by-products derived from the raw material solution,
The content of unreacted raw materials in the mother liquor decreases. Therefore, in such a case, it is more preferable to intentionally supply the raw material in excess with the unreacted raw material that is being diluted. In the present invention, in the case of producing a poorly water-soluble salt by reacting three kinds of raw materials, one or two kinds of the three kinds of raw materials are contained in the mother liquor as unreacted raw materials to obtain the present invention. It can be suitably implemented.

Therefore, in any of the methods, the content of unreacted raw material contained in the mother liquor obtained by sieving the product slurry is 100% of the product produced by 100% reaction of the supplied raw material. Therefore, 0.005 to 30 mol is preferable, and 0.01 to 15 mol is more preferable. Content of unreacted raw material is 0.00
When the amount is less than 5 mol, the amount of seed crystals formed is too small, and the reaction is hardly affected.
If it exceeds 0 mol, most of the supplied raw materials are used for the production of seed crystals, and it becomes meaningless to react in a tubular reactor.

Next, a method of supplying the seed crystal will be described.
First, as described above, the amount of one raw material is adjusted in advance in the mother liquor by adjusting the amount, and a certain amount of the resulting seed crystal is supplied to obtain a sparingly water-soluble salt having a desired average particle size. be able to. In this case, it is necessary to obtain the relationship between the content and the average particle size in advance. That is, the content of the unreacted raw material may be adjusted so that a poorly water-soluble salt having a desired average particle diameter can be obtained based on the relationship between the two, for example, as shown in Example 1 described later.
Alternatively, a constant amount is supplied by controlling the amount of seed crystal supplied by the following method. According to this method, a sparingly water-soluble salt having a desired average particle diameter can be obtained without changing the content of unreacted raw materials in the mother liquor.

That is, in this method, the amount of seed crystals supplied is appropriately adjusted according to the size of the seed crystals and the number of particles. That is, when the average particle size of the seed crystal is small,
Since a large specific surface area can be obtained, it is effective even if the number of particles is small, and it is necessary to increase the number of particles as the average particle diameter becomes larger. This is due to the nucleation on the surface of the seed crystal, and it is theoretically interpreted that the specific surface area of the seed crystal is involved in the number of nucleation. Therefore, it is essentially important to measure the size of the seed crystal and the number of particles, or the specific surface area, but it is impossible to measure all of them in real time at the current technical level.

In the poorly water-soluble salt as in the present invention, the crystal growth rate is very high, so that the variation of the seed crystal supply amount is directly reflected in the produced particle size. In other words, unless the supply amount is appropriate, only product crystals having a particle size or shape that is not desired can be produced. Therefore, the following method is preferable as a method for controlling the supply amount of the seed crystal. That is, this is a method in which the amount of mother liquor containing seed crystals, unreacted raw materials, etc. (hereinafter abbreviated as seed crystals, etc.) is kept constant, and the seed crystal supply amount is controlled by the following method.

The feature of this method is that the mother liquor containing seed crystals and the like is introduced through two lines. That is, one is a line (filtrate line) that passes through a solid-liquid separator such as a Kuno filter, a liquid filter, a rotary filter, or a filter press, and the other is a line that directly feeds a seed crystal (bypass line). . In this method, the seed crystal supply amount is determined by the ratio of the amount of liquid fed in the line that captures the seed crystal and does not pass the seed crystal at all (filtrate line) and the line that feeds the seed crystal as it is (bypass line). Controlled.

Specifically, for example, when the grain size of the crystals discharged from the reactor is larger than the desired grain size, it is necessary to increase the seed crystal supply amount, and at this time, the mother liquor flow rate flowing toward the fill trait line. By increasing the flow rate of the mother liquor flowing toward the bypass line, the seed crystal supply amount can be increased. As a result, the amount of nucleation is increased and the number of produced particles is increased. That is, the size of each particle is reduced, and the particle size of the product approaches the target particle size. On the contrary, when the grain size of the crystals discharged from the reactor is smaller than the desired grain size, the mother liquor flow rate on the fill tray line is increased and the mother liquor flow rate on the bypass line is reduced to reduce the seed crystal supply amount. You can do it. At this time, the flow rate ratio is operated by, for example, a flow meter and a valve installed in each line. By appropriately adjusting the flow rate ratio in this manner, a certain amount of seed crystals can be supplied to the reactor.

In the present invention, the type of the tubular reactor is not particularly limited, but the residence time distribution of the fluid in the apparatus can be kept extremely narrow, and the reaction apparatus has a stirring section / driving section. However, from the standpoint of a continuous reaction device capable of promptly and uniformly mixing and stirring various fluids to react with each other and promptly discharging the reaction product out of the reaction device, Japanese Patent Application No. The tubular reactor described in No. 358429 can be preferably used. As a specific example of such a tubular reactor, for example, one shown in FIG.

[0021] By using such a tubular reactor, even if a device having no driving unit or stirring unit is used in the tubular reactor, it is possible to quickly and uniformly contact different fluids. It can be a mixed fluid.
Moreover, the residence time distribution is kept very narrow because there is almost no backmixing in the tubular reactor. Furthermore, when looking at the inside of the reactor as a whole, the mixed and agitated fluid is a piston flow, and the fluid containing the reaction products is promptly discharged to the outside of the reactor, so the residence time is short, and It has the characteristic that the time to reach a steady state is short.

The slurry containing the sparingly water-soluble salt (product) discharged from the continuous reaction device is sieved by a classifier. The classifier used here is not particularly limited, but centrifugal force is used. The sedimentation type is preferred. Specifically, a liquid cyclone, a cylindrical centrifuge,
A decanter type centrifugal separator and the like can be mentioned. Among these,
A liquid cyclone is more preferable in terms of equipment cost, maintainability, and compactness of equipment space.

In the following, in the continuous manufacturing method of the present invention, all steps from the supply of raw materials to the recovery of products will be described in detail based on the apparatus configuration (FIG. 2). 2 shows an example of a device configuration diagram of a device used in the present invention. The present invention is
In the method for producing a sparingly water-soluble salt by continuously introducing two or more raw materials into a tubular reactor, while circulating the mother liquor,
A sparingly water-soluble salt obtained by the reaction of an unreacted raw material and a new raw material contained therein is supplied to a reactor as a seed crystal to homogenize nucleation and crystal growth. At this time, a line (bypass line) that allows the raw material solution containing the seed crystals to pass through as it is and a line (filtrate line) that removes the seed crystals through the solid-liquid separator are provided to control the amount of liquid that passes through each line. By doing
The supply amount of the seed crystal is appropriately controlled. In this way
It is characterized in that crystals of a poorly water-soluble salt having a desired particle size are obtained.

Even if the seed crystal supply amount is not controlled in this way, a poorly water-soluble salt having a desired particle size can be obtained by appropriately adjusting the excess amount of the unreacted raw material as described above. The apparatus configuration in this case is achieved by deleting both lines in the apparatus configuration of FIG. 2 and setting the flow rate ratio of the bypass line to 100%.

The respective constituent devices are as follows. A mother liquor tank 11 'and a mother liquor tank 12' for storing a solvent (mother liquor) used when preparing a raw material solution are installed. Usually, one material is preliminarily charged in an appropriate amount in the mother liquor (both or one mother liquor tank), the mother liquor is sent from the mother liquor tank, and the raw material is dissolved in the mother liquor to obtain a raw material solution. Tubular reactor 6
Then, the raw material solution reacts to generate crystals of a poorly water-soluble salt and is stored in the relay tank 17. Further, after being classified by the classifier 18, the product is collected in the liquid receiving tank 15. Further, all of the mother liquor containing unreacted raw materials is fed back to the mother liquor tanks 11 'and 12' by a liquid feeding means such as a pump. The mother liquor fed back contains unreacted raw materials, and when this liquid and new raw materials are mixed, the unreacted raw materials react with the new raw materials to produce crystals. This is used as a seed crystal. At this time, when the mother liquor contains fine crystals that were not captured by the classifier, both the fine crystals and the newly generated crystals can be used, and thus the control of the supply amount of the seed crystals is more effective. It will be easy. Further, since the mother liquor is collected and reused, almost no liquid is discharged.

The sparingly water-soluble salt referred to in the present invention means Chem. Eng.
Technol. Vol. 11 P.264 to 276 (1988), the relative supersaturation σ at the time of reaction is 1 to 1000.
A salt such as However, the relative degree of supersaturation is expressed by the following equation.

[0027]

[Equation 1]

The continuous reaction of the sparingly water-soluble salt of the present invention is to obtain a sparingly water-soluble salt by an instantaneous reaction having a relative supersaturation degree of 1 to 1000. The degree of supersaturation is preferably 5 to 500. More preferably, 10 to 200 is most desirable.
When the relative degree of supersaturation is less than 1, in the reaction of a poorly water-soluble salt,
Since the reaction concentration is extremely dilute, the production efficiency becomes extremely low, which is disadvantageous in terms of manufacturing cost. In addition, when the relative supersaturation exceeds 1000, the reaction rate is the fastest among the reactions of poorly water-soluble salts. In order to carry out such a reaction, the velocity difference between the two fluids should be very large and Need to mix. However, as the speed difference becomes extremely large, the pressure loss becomes large, and the equipment and power for liquid feeding also become large, which is disadvantageous in terms of cost.

Thus, the relative degree of supersaturation is 1 to 1000.
Examples of the raw material for the reaction such as: alkali; Ca (OH) ₂ , Ba (OH) ₂ acid; HF, H ₂ SO ₄ , H ₂ CO ₃ salt; BaCO ₃ , BaCl ₂ , K ₂ CO ₃ , Ag
NO ₃ , KCl, NaClO ₄ , MgCl ₂ , Na ₂ C
₂ O ₄ , Ba (NO ₃ ) ₂ NH ₄ F, NiSO ₄ , (NH ₄ ) ₂ SO ₄ , Na ₂ S
O ₄ alkoxide; Ti (OC ₂ H ₅ ) ₄ or the like is dissolved in water, a lower alcohol (eg, methanol, ethanol, isopropanol, etc.) or the like to form a solution (raw material fluid). In the present invention, by appropriately combining these, the relative degree of supersaturation is 1 to 100.
The relative supersaturation is 10-
Specific examples of the combination of raw materials such as 200 are as follows (a) to (f).

[0030]

[Chemical 1]

Of these, barium sulfate having a uniform particle size is desired, and barium sulfate is preferably the sparingly water-soluble salt, especially for use in cosmetics and extender pigments.

According to the manufacturing method of the present invention as described above,
Even in a reaction that produces a poorly water-soluble salt having a very high reaction rate, a product of uniform quality (particle size, crystal shape, etc.) can be continuously produced. In particular, it has excellent feeling of use such as stretching and sticking, and has high light diffusion and transparency, and a bare skin feeling,
Barium sulfate, which is excellent as an extender pigment and a blending component for cosmetics, can be efficiently and continuously produced because it has an effect of making color unevenness such as spots and freckles less visible.

[0033]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1 In order to continuously produce barium sulfate powder based on the apparatus shown in FIG. 2, the following preparations were made. Special grade reagent 18930g of barium hydroxide octahydrate 180.4L of deionized water
Barium hydroxide raw material (raw material b) dissolved in (heated to 60 ° C.) and special grade reagent 98 wt% sulfuric acid 5880 g
(Raw material a) was prepared as a raw material. Mother liquor tank 1
1'and mother liquor tank 12 'contain 1000 L of deionized water.
According to the procedure described above, various sulfuric acid aqueous solutions in which various amounts of 98% by weight sulfuric acid were dissolved were charged and the temperature was raised to 60 ° C. The tubular reactor used was that shown in Table 1, and the classifier used was a liquid cyclone (manufactured by Oishi Machine Co., Ltd., Supercron TR10-50). In this example, the apparatus configuration was used in which only the bypass line was used without using the fill trait line (that is, 100% of the seed crystal was supplied).

When all the preparations are completed, the reactor is preliminarily filled with liquid (ion-exchanged water) and preheated to 60 ° C. (reactor configuration is shown in FIG. 1, 1 in FIG. 1 is a raw material supply port ( B), 2 is a raw material supply port (A), 3 is a buffer tank, 4 is a run-up section, 5 is a raw material supply pipe, 6 is a pipe diameter reactor, 7 is a product discharge port, 8 is an end portion, 9 is a raw material A mother liquor is supplied at a rate of 30 L / min using a pump (which is a supply pipe), and at the same time, a raw material a is fed at 88.2 g / min and a raw material b is fed at 2.84 kg / min to be dissolved in the mother liquor, The raw material solution was used.

Two minutes after the raw material feed pump was operated, the pump for supplying the product slurry to the liquid cyclone was started, and the mother liquor containing the unreacted raw material was fed from the top in the liquid cyclone, and other The slurry containing non-fine particles was extracted from the bottom and stored in the liquid receiving tank. At this time, all of the mother liquor containing the unreacted raw material extracted from the top was returned to the mother liquor tank (11 'and 12'). The results are shown in Table 2 and FIG. From these, it can be seen that a product having a desired average particle size can be obtained by changing the content of the unreacted raw material in the mother liquor. The average particle size of the obtained barium sulfate powder was measured by Horiba Ltd.
Manufactured by a particle size distribution measuring device LA-700.

[0037]

[Table 1]

[0038]

[Table 2]

Example 2 For the continuous production of barium sulfate powder based on the apparatus of FIG. 2, it was prepared as follows. Special grade reagent 18930g of barium hydroxide octahydrate 180.4L of deionized water
Barium hydroxide raw material (raw material b) dissolved in (heated to 60 ° C.) and special grade reagent 98 wt% sulfuric acid 5880 g
(Raw material a) was prepared as a raw material. Mother liquor tank 1
1'and mother liquor tank 12 'have 98 in 1000 L of deionized water
A sulfuric acid aqueous solution in which 30 g of weight% sulfuric acid was dissolved was charged and the temperature was raised to 60 ° C. A liquid filter (Sumitomo 3M Co., Ltd., using a filter bag 523A) was used for the fill tray line, Table 1 was used for the tubular reactor, and a liquid cyclone (manufactured by Oishi Machinery Co., Ltd.) for the classifier.
Super Clone TR10-50) was used.

When all the preparations have been completed, a pump is used in a reactor (reactor configuration is as shown in FIG. 1) which has been pre-filled with liquid (ion-exchanged water) and preheated to 60 ° C. supply at the same time, and at the same time feed material a
The raw material b was fed at 8.2 g / min and the raw material b at 2.84 kg / min to be dissolved in the mother liquor to obtain a raw material solution.

Two minutes after the raw material feed pump was operated, the pump for supplying the product slurry to the liquid cyclone was started, and in the liquid cyclone, the mother liquor containing the unreacted raw material was supplied from the top, and other The slurry containing non-fine particles was extracted from the bottom and stored in the liquid receiving tank. At this time, all of the mother liquor containing the unreacted raw material extracted from the top was returned to the mother liquor tank (11 'and 12').

At the start of the reaction, the flow rate of the bypass line was set to 100% (= the flow rate of the bypass line / total flow rate), and thereafter the flow rates of the fill rate line and the bypass line were determined based on the measurement results of the average particle size. The valves installed in each line were adjusted as shown in FIG. That is, from the start of the reaction to 30 minutes, the average particle size is 5
The average particle size was set to 4 μm after 30 minutes so that the average particle size became 4 μm. After operating the pump for supplying the product slurry to the liquid cyclone, the slurry was sampled from the bottom of the liquid cyclone every 2 minutes and the average particle size was measured to obtain a product with a stable average particle size. You can see that it is being done.

[0043]

According to the present invention, a poorly water-soluble salt having a uniform particle size suitable for extender pigments, cosmetics, photographic emulsions, electronic materials and additives can be produced. According to the method of the present invention, the following effects can be obtained. In a method for producing a sparingly water-soluble salt by continuously supplying two or more kinds of raw materials to a tubular reactor, mixing and reacting in the reactor, a certain amount of seed crystals is supplied while circulating a mother liquor, By controlling the generation amount, it is possible to stably produce a poorly water-soluble salt crystal having a desired particle size and shape. When controlling the seed crystal supply amount, divide the raw material solution containing the seed crystal into a line that allows it to pass through (bypass line) and a line that removes solids through a solid-liquid separator (filtrate line), and the amount of liquid that passes through it. By controlling the ratio, it is possible to easily adjust the supply amount of the seed crystal of the poorly water-soluble salt with simple equipment. Crystals with uniform particle size and shape can be produced stably,
Furthermore, the yield can be improved and the seed crystals can be prepared and incidental facilities can be reduced.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of a reactor section of a continuous reaction apparatus suitably used in the production method of the present invention.

FIG. 2 is a schematic diagram showing the configuration of a continuous reaction apparatus used in Examples.

FIG. 3 is a graph showing changes in the average particle size of the product produced in Example 1 with respect to the ratio of the content of unreacted raw material to 100 mol of the product.

FIG. 4 is a graph showing changes in the flow rate ratio of the bypass line and the average particle size of the product with the passage of reaction time in Example 2.

[Explanation of symbols]

 1 raw material supply port (B) 2 raw material supply port (A) 3 buffer tank 4 run-up section 5 raw material supply pipe 6 tubular reactor 7 product discharge port 8 end 9 raw material supply pipe 11 'mother liquor tank (mother liquor a) 12 'Mother liquor tank (mother liquor b) 15 Liquid receiving tank 17 Relay tank 18 Classifier

Claims (3)

[Claims] 1. Two or more kinds of raw materials are respectively mixed with a mother liquor containing one of the raw materials, continuously supplied to a tubular reactor and mixed in the reactor to react to produce a poorly water-soluble salt. In the method, the product slurry in which the sparingly water-soluble salt discharged from the reactor is dispersed in the mother liquor is sieved, and the mother liquor containing the unreacted raw material obtained is circulated so as to be supplied to the reactor again. While refusing, the unreacted raw material and a new raw material are reacted in a supply line to the reactor to produce a poorly water-soluble salt, and the poorly water-soluble salt is supplied to the reactor as a seed crystal. Continuous manufacturing method. 2. The continuous production method according to claim 1, wherein the poorly water-soluble salt is barium sulfate. 3. Two lines, a line (filtrate line) capable of removing a seed crystal through a solid-liquid separator capable of collecting a seed crystal and a line not bypassing a solid-liquid separator (bypass line) are provided. 3. The continuous production method according to claim 1, wherein the seed crystal is supplied to the reactor in a constant amount by controlling the amount of liquid passing through each line.