Manufacturing method of anhydrous sodium hydrosulfide tangible material

Abstract

To provide a method of producing an anhydrous sodium hydrosulfide tangible product that is safe and highly efficient in production, capable of producing the anhydrous sodium hydrosulfide tangible product with few impurities continuously.SOLUTION: In the method of producing the anhydrous sodium hydrosulfide tangible product of the present invention, the anhydrous sodium hydrosulfide tangible product is obtained continuously by repeating such steps as in order, a thin film forming step of using a sodium hydrosulfide aqueous solution as a starting material and supplying the sodium hydrosulfide aqueous solution to a disk surface to obtain a thin film of the sodium hydrosulfide aqueous solution, a drying step of dehydrating the thin film of sodium hydrosulfide aqueous solution on the disk surface under reduced pressure inert gas atmosphere, and a separation step of removing from the disk surface the anhydrous sodium hydrosulfide tangible product obtained in the drying step.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for continuously producing anhydrous sodium hydrosulfide solid matter having a small amount of impurities. [Background technology]

[0002] Sodium hydrosulfide (NaSH) is known as a raw material for organic synthesis and polyphenylene sulfide (PPS) resin, but commercially available sodium hydrosulfide usually contains a certain amount of water, which can lead to undesirable side reactions and reverse reactions. For this reason, it is necessary to remove the water before using it as a raw material, and known methods for removing such water include a method of heating and dehydrating sodium hydrosulfide shaped substances in the form of flakes, chips, pellets, etc. under reduced pressure, a method of dehydrating said sodium hydrosulfide shaped substances under an inert gas atmosphere, or a combination of both of these methods.

[0003] For example, Patent Document 1 describes a method for dehydrating sodium hydrosulfide tangible matter containing a total sodium hydrosulfide content of 65% by weight or more, which is characterized in that an inert gas is passed through the sodium hydrosulfide tangible matter to dehydrate the surface of the matter, and then the matter is heated and dehydrated under reduced pressure. According to this method, it is said that a high-concentration sodium hydrosulfide tangible matter can be obtained in a high yield in a short time without altering the sodium hydrosulfide. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 6-298502 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the dehydration method described in Patent Document 1 is a batch type, and the dehydration time is long, so that the production efficiency is not good and the cost is high in some cases. In addition, there is a risk that the sodium hydrosulfide tangible matter will melt when heated at a temperature equal to or higher than the melting point of sodium hydrosulfide. As another method for removing moisture from sodium hydrosulfide, there is a method of recrystallizing the sodium hydrosulfide tangible matter, but this requires solid-liquid separation at a high temperature of 100°C or higher, which poses a safety issue. Another method is to concentrate and dehydrate an aqueous sodium hydrosulfide solution, but as the concentration and dehydration proceeds, the viscosity increases rapidly and the solution becomes lumpy, making the subsequent dehydration operation difficult.

[0006] The present invention has been made in order to solve the above problems, and an object of the present invention is to provide a method for producing anhydrous sodium hydrosulfide tangible product which can continuously produce anhydrous sodium hydrosulfide tangible product having few impurities, safely and efficiently. [Means for solving the problem]

[0007] The above-mentioned object can be attained by providing a method for producing an anhydrous sodium hydrosulfide tangible product, characterized in that the following steps are repeated in this order to continuously obtain an anhydrous sodium hydrosulfide tangible product: a thin film forming step of supplying an aqueous sodium hydrosulfide solution to a disk surface to obtain a thin film of the aqueous sodium hydrosulfide solution; a drying step of dehydrating the thin film of the aqueous sodium hydrosulfide solution on the disk surface under reduced pressure and in an inert gas atmosphere; and a separation step of extracting an anhydrous sodium hydrosulfide tangible product obtained in the drying step from the disk surface.

[0008] In this case, it is preferable that the dehydration time in the drying step is 6 to 300 seconds, and the concentration of the aqueous sodium hydrosulfide solution is 10 to 70% by weight. It is also preferable that the content of the anhydrous sodium hydrosulfide component in the anhydrous sodium hydrosulfide tangible product is 95% by weight or more, and that the content of the sodium sulfide component in the anhydrous sodium hydrosulfide tangible product is 1.5% by weight or less. It is also preferable that the water content in the anhydrous sodium hydrosulfide tangible product is 3% by weight or less. Effect of the Invention

[0009] INDUSTRIAL APPLICABILITY The present invention provides a method for producing anhydrous sodium hydrosulfide shaped products safely and efficiently, which can continuously produce anhydrous sodium hydrosulfide shaped products containing fewer impurities. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a schematic diagram showing an example of a vacuum thin film dryer used in Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present invention will be specifically described below with reference to the drawings. Fig. 1 is a schematic diagram showing an example of a vacuum thin film dryer used in the present invention, and the inside of the container is provided with a supply tank for supplying an aqueous sodium hydrosulfide solution, a supply pump, a circulation tank, a circulation pump, and a supply nozzle. The vacuum thin film dryer further includes a disk having a rotating shaft, a scraper for removing anhydrous sodium hydrosulfide tangible matter from the surface of the disk, a collection tank for collecting the anhydrous sodium hydrosulfide tangible matter, and the like, and is also provided with a disk heating means, an inert gas supplying means, and a pressure reducing means, which are not shown in Fig. 1.

[0012] The method for producing an anhydrous sodium hydrosulfide tangible product of the present invention is characterized in that it uses an aqueous sodium hydrosulfide solution as a starting material, and continuously obtains an anhydrous sodium hydrosulfide tangible product by repeating in this order the following steps: a thin film forming step (hereinafter sometimes abbreviated as "thin film forming step") of supplying the aqueous sodium hydrosulfide solution to a disk surface to obtain a thin film of the aqueous sodium hydrosulfide solution; a drying step (hereinafter sometimes abbreviated as "drying step") of dehydrating the thin film of the aqueous sodium hydrosulfide solution on the disk surface under reduced pressure and in an inert gas atmosphere; and a separation step (hereinafter sometimes abbreviated as "separation step") of removing the anhydrous sodium hydrosulfide tangible product obtained in the drying step from the disk surface.

[0013] As will be seen from the comparison between the Examples and Comparative Examples described later, in Comparative Example 1, in which the sodium hydrosulfide tangible matter was heated and dehydrated under reduced pressure, the temperature increase operation had to be adjusted excessively to prevent the sodium hydrosulfide tangible matter from melting and forming lumps, resulting in a longer dehydration time and an increase in the amount of sodium sulfide (Na2S) impurity. In Comparative Example 2, in which the sodium hydrosulfide aqueous solution was concentrated and dehydrated, the viscosity increased rapidly as the concentration and dehydration proceeded, forming lumps, which made stirring impossible, and the dehydration operation had to be stopped. In Comparative Example 3, in which the sodium hydrosulfide aqueous solution was dehydrated by spraying it in a mist form using a vacuum spray dryer, the pressure of the liquid delivery pump increased due to pipe blockage, etc., and when the pressure of the liquid delivery pump increased, the hot, strongly alkaline sodium hydrosulfide aqueous solution may spray out of the pipe, which is a problem in terms of safety. In addition, the spray pressure was not stable, and the quality of the obtained sodium hydrosulfide varied. In contrast, in Example 1, in which the thin film forming step, drying step, and separation step were repeated in this order, anhydrous sodium hydrosulfide tangible product with few impurities can be obtained continuously, safely, and efficiently. Therefore, it can be seen that the significance of the present invention, which employs such a method, is great.

[0014] In the thin film forming step in the present invention, a step of supplying an aqueous sodium hydrosulfide solution to the disk surface to obtain a thin film of the aqueous sodium hydrosulfide solution is carried out. As shown in FIG. 1, it is preferable that the aqueous sodium hydrosulfide solution is sent from the supply tank to the circulation tank by the supply pump, and it is preferable that the aqueous sodium hydrosulfide solution is sent from the circulation tank to the supply nozzle by the circulation pump. Then, a step of supplying the aqueous sodium hydrosulfide solution to the rotating disk surface from the supply nozzle to obtain a thin film of the aqueous sodium hydrosulfide solution is preferably carried out. A method is preferably adopted in which the excess aqueous sodium hydrosulfide solution not attached to the disk surface is recovered in the circulation tank and sent again to the supply nozzle by the circulation pump. At this time, it is preferable that the disk surface is kept at 50 to 170° C. by the disk heating means, and it is more preferable that the disk surface is kept at 80 to 150° C. The disk heating means is not particularly limited, and a heating device may be provided separately, or steam removed in the drying step described later may be used as the heating means. As in the drying step described below, in the thin film formation step, a method in which the inside of a container is placed under reduced pressure and an inert atmosphere is preferably adopted.

[0015] The concentration of the aqueous sodium hydrosulfide solution used in the present invention is not particularly limited, but is preferably 10 to 70% by weight. If the concentration of the aqueous sodium hydrosulfide solution is less than 10% by weight, the production efficiency may be significantly reduced, so the concentration is more preferably 30% by weight or more, and even more preferably 40% by weight or more. On the other hand, if the concentration of the aqueous sodium hydrosulfide solution exceeds 70% by weight, the aqueous solution may solidify in the piping during the transfer, so the concentration is more preferably 65% ​​by weight or less, and even more preferably 55% by weight or less.

[0016] In the drying step of the present invention, the sodium hydrosulfide aqueous solution formed into a thin film is dehydrated on the disk surface under reduced pressure and in an inert gas atmosphere. As the disk rotates, moisture is removed from the sodium hydrosulfide aqueous solution formed into a thin film on the disk surface. At this time, similar to the thin film forming step, the disk surface is preferably kept at 50 to 170°C by a disk heating means, more preferably at 80 to 150°C. In the drying step, the method of reducing the pressure is not particularly limited, and a method of reducing the pressure inside a container by a reducing means such as a vacuum pump is preferably adopted, whereby moisture is evaporated uniformly and efficiently and removed as steam. From the viewpoint of removing the steam present in the container, it is a preferred embodiment to provide an outlet for removing the steam at an arbitrary position of the container.

[0017] In addition, in the drying step, the method of creating an inert gas atmosphere is not particularly limited, and a method of supplying an inert gas into the container by an inert gas supplying means is preferably adopted. Examples of the inert gas include nitrogen, helium, and argon, and among them, nitrogen is preferably used. In addition, it is preferable to have a recovery means for recovering the inert gas supplied into the container. The recovery means is not particularly limited, but the inert gas may be recovered together with the steam from the exhaust port for removing the above-mentioned steam, and it is also a preferred embodiment to separate the recovered inert gas from the steam and then supply the inert gas again into the container by the inert gas supplying means.

[0018] The inventors' investigations have revealed that the content of impurities such as sodium hydrosulfide (Na2S) tends to increase as the dehydration time in the drying step increases. From this viewpoint, the dehydration time is preferably 6 to 300 seconds, more preferably 10 to 240 seconds, and even more preferably 20 to 180 seconds. When the dehydration time is within such a range, an anhydrous sodium hydrosulfide tangible product containing fewer impurities can be obtained. The dehydration time in the present invention refers to the time required for the drying step, and refers to the time from immediately after the sodium hydrosulfide aqueous solution formed into a thin film in the thin film forming step is obtained to immediately before the anhydrous sodium hydrosulfide tangible product is removed from the disk surface in the separation step.

[0019] The degree of reduced pressure (absolute pressure) in the container in the drying step is preferably 1 to 40 kPa, more preferably 5 to 30 kPa. By controlling the degree of reduced pressure and the temperature of the disk surface, it is possible to efficiently remove moisture from the aqueous sodium hydrosulfide solution formed into a thin film on the disk surface, and obtain an anhydrous sodium hydrosulfide tangible product.

[0020] Next, in the separation step in the present invention, a step of removing the anhydrous sodium hydrosulfide tangible matter obtained in the drying step from the disk surface is carried out. The method of removing the anhydrous sodium hydrosulfide tangible matter is not particularly limited, but as shown in Fig. 1, it is preferable that a scraper is provided in the container, and the anhydrous sodium hydrosulfide tangible matter obtained in the drying step is scraped off the disk surface with the scraper as the disk rotates, and a collection tank is provided in which the scraped off anhydrous sodium hydrosulfide tangible matter is collected. Since the anhydrous sodium hydrosulfide tangible matter exhibits deliquescent properties, a method of making the inside of the container under a reduced pressure and an inert atmosphere is preferably adopted in the separation step as in the drying step.

[0021] The method for producing an anhydrous sodium hydrosulfide tangible product of the present invention is characterized by repeating the above-mentioned thin film forming step, drying step and separation step in this order, thereby making it possible to continuously, safely and efficiently produce an anhydrous sodium hydrosulfide tangible product with few impurities. In the anhydrous sodium hydrosulfide tangible product obtained by the present invention, the content of the anhydrous sodium hydrosulfide component is preferably 95% by weight or more, more preferably 96% by weight or more, and even more preferably 97% by weight or more. The content of the anhydrous sodium hydrosulfide component is usually 99.5% by weight or less, and preferably 99% by weight or less.

[0022] In the anhydrous sodium hydrosulfide tangible material obtained by the present invention, the water content is preferably 3% by weight or less, more preferably 2% by weight or less, even more preferably 1% by weight or less, particularly preferably 0.6% by weight or less, and most preferably substantially free of water.

[0023] The anhydrous sodium hydrosulfide tangible product obtained by the present invention may contain impurities such as sodium sulfide (Na2S), sodium carbonate (Na2CO3), sodium sulfite (Na2SO3), sodium thiosulfate (Na2S2O3), etc., but the total content of sodium sulfide (Na2S), sodium carbonate (Na2CO3), sodium sulfite (Na2SO3) and sodium thiosulfate (Na2S2O3) components is preferably 5% by weight or less, more preferably 4% by weight or less, even more preferably 3% by weight or less, and particularly preferably 2% by weight or less. The total content is usually 0.5% by weight or more.

[0024] In particular, in the anhydrous sodium hydrosulfide tangible product obtained by the present invention, the content of the sodium sulfide component is preferably 1.5% by weight or less. From the viewpoint of minimizing impurities, the content of the sodium sulfide component is more preferably 1.2% by weight or less, and further preferably 1.0% by weight or less. The content of the sodium sulfide component is usually 0.1% by weight or more.

[0025] The shape of the anhydrous sodium hydrosulfide shaped product obtained in the present invention is not particularly limited, and may be any shape such as flakes, chips, pellets, etc. The anhydrous sodium hydrosulfide shaped product obtained in the present invention has a small amount of water and impurities, and therefore can be suitably used as a raw material for organic synthesis or industrial products. EXAMPLES

[0026] The present invention will now be described in more detail with reference to examples.

[0027] Example 1 2 L of 45 wt% sodium hydrosulfide aqueous solution was supplied from the supply tank of a vacuum thin film dryer (manufactured by Nishimura Iron Works, Ltd.) to the circulation tank by a supply pump. The 45 wt% sodium hydrosulfide aqueous solution was sent from the circulation tank to the supply nozzle by the circulation pump, and the 45 wt% sodium hydrosulfide aqueous solution was rotated from the tip of the supply nozzle with a heat transfer area of ​​0.4 m 2 The aqueous sodium hydrosulfide solution was continuously supplied to the disk surface, and a thin film of the aqueous sodium hydrosulfide solution was formed on the disk surface. The excess aqueous sodium hydrosulfide solution that did not adhere to the disk returned to the circulation tank and was again sent from the circulation tank to the supply nozzle. At this time, the degree of vacuum (absolute pressure) in the device was 20 kPaabs, the disk steam pressure (gauge pressure) was 0.3 MPaG, the amount of nitrogen was 50 L / min (99.9% or more), and the temperature of the disk surface was 140°C. As the disk rotated, the water in the thin film was dehydrated in 30 seconds and turned into a tangible substance, which was scraped off from the disk surface with a scraper and collected in a collection tank, obtaining an anhydrous sodium hydrosulfide tangible substance. The components of the obtained anhydrous sodium hydrosulfide tangible substance were analyzed by a combination of neutralization titration and oxidation-reduction titration. The moisture value was calculated by subtracting other components from the total. The results are summarized in Table 1.

[0028] Comparative Example 1 300 kg of flake-shaped sodium hydrosulfide was charged into a conical dryer, and the vacuum was set to 0.8 to 1.3 kpa. The warm water used to raise the jacket temperature of the conical dryer was heated to 45°C over 100 minutes. After that, when drainage began to come out, the temperature was kept as it was, and then the temperature was gradually raised. When the temperature was raised to 47°C at 1°C / h, drainage began to come out, so it was kept at 47°C for 3 hours. After raising the temperature to 48°C, it was kept as it was for 815 minutes overnight. After that, it was raised to 50°C at 1°C / h, and a lot of drainage began to come out. When the temperature was raised to 51°C at 0.5°C / h, even more drainage began to come out, so the temperature increase was stopped. It was kept as it was for 6 hours. It was raised to 52°C and kept as it was for 800 minutes overnight. It was then raised at 0.5°C / h, and kept as it was for 1410 minutes. The temperature was raised to 55°C at 0.5°C / 3h and kept at 55°C for 630 minutes. After keeping at 55.5°C for 1 hour, the temperature was raised to 56°C. As a result, the amount of drainage increased, so the temperature was kept at 4 hours and raised to 60°C at 0.5°C / 2h. The temperature was raised to 70°C at 1°C / h, and then to 79.5°C at 0.5-1°C / 30min, and dehydration was completed. The components of the obtained sodium hydrosulfide tangible matter were analyzed using the method described in Example 1. The results are summarized in Table 1.

[0029] Comparative Example 2 1820g of 45% by weight sodium hydrosulfide aqueous solution was charged into a vacuum concentrator with stirring function "PV Mixer" (manufactured by Kobelco Eco-Solutions Co., Ltd.), the stirring speed was 70RPM, the jacket temperature was raised to 60°C, the vacuum degree was set to 30Torr, and the state was maintained until the sodium hydrosulfide became a slurry. After the slurry state was reached, the jacket temperature was gradually raised to 80°C and the vacuum degree was set to 20Torr. As a result, stirring became impossible and the operation was stopped. The components of the sodium hydrosulfide tangible matter obtained by the above operations were analyzed using the method described in Example 1. The results are summarized in Table 1.

[0030] Comparative Example 3 A 45 wt% aqueous solution of sodium hydrosulfide was continuously supplied to the heat exchange piping of a vacuum spray drying apparatus at 6 L / h. At that time, the entire apparatus was decompressed to 30 Torr. The heat exchange piping was heated to 150°C, and the 45 wt% aqueous solution of sodium hydrosulfide sprayed in the form of mist was dehydrated at once and sprayed as a solid into a collection can. The jacket of the collection can was heated to 120°C to prevent moisture absorption and condensation. The sodium hydrosulfide powder collected in the collection can was collected in a powder receiver. The components of the obtained sodium hydrosulfide powder were analyzed using the method described in Example 1. The results are summarized in Table 1. It was found that the pressure of the liquid pump increased when the sodium hydrosulfide aqueous solution was supplied to the heat exchange piping due to the occurrence of pipe blockage, etc. Thus, when the pressure of the liquid pump increased, the sodium hydrosulfide aqueous solution of strong alkali at high temperature may spray out from the piping, which is a safety problem. In addition, the quality of the sodium hydrosulfide powder collected in the collection can was uneven.

[0031] [Table 1] [Explanation of symbols]

[0032] 1 Vacuum thin film dryer 2 containers 3. Sodium hydrosulfide solution 4 Supply tank 5 Supply Pump 6 Circulation tank 7 Circulation Pump 8 Supply Nozzle 9 Rotation Axis 10 Disc 11 Scraper 12 Sodium hydrosulfide anhydrous (tangible) 13 Collection tank

Claims

1. Starting material is sodium hydrosulfide aqueous solution, a thin film forming step of supplying the sodium hydrosulfide aqueous solution onto a disk surface to obtain a thin film of the sodium hydrosulfide aqueous solution; a drying step of dehydrating the thin film of sodium hydrosulfide aqueous solution on the disk surface under reduced pressure and in an inert gas atmosphere; A separation step of removing the anhydrous sodium hydrosulfide tangible matter obtained in the drying step from the disk surface. The method is characterized in that the anhydrous sodium hydrosulfide tangible product is continuously obtained by repeating this sequence, The method for producing anhydrous sodium hydrosulfide tangible product, wherein the concentration of the aqueous sodium hydrosulfide solution is 10 to 70% by weight.

2. 2. The method for producing anhydrous sodium hydrosulfide tangible material according to claim 1, wherein the dehydration time in the drying step is 6 to 300 seconds.

3. 3. The method for producing an anhydrous sodium hydrosulfide shaped product according to claim 1, wherein the content of an anhydrous sodium hydrosulfide component in the anhydrous sodium hydrosulfide shaped product is 95% by weight or more.

4. 3. The method for producing an anhydrous sodium hydrosulfide shaped product according to claim 1, wherein the content of sodium sulfide in the anhydrous sodium hydrosulfide shaped product is 1.5% by weight or less.

5. 3. The method for producing an anhydrous sodium hydrosulfide shaped product according to claim 1, wherein the water content in the anhydrous sodium hydrosulfide shaped product is 3% by weight or less.

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