JP2014181138A - Method for producing sodium hydrogensulfide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a sodium hydrogensulfide solution capable of swiftly progressing gas-liquid contact reaction while preventing device clogging caused by carbonate and sodium sulfide.SOLUTION: Provided is a method for producing a sodium hydrogensulfide solution comprising: a mixing step of mixing a caustic soda solution and a sodium hydrogensulfide solution; a step of generating a gas-liquid two phase flow with a mixed solution obtained by the mixing step as a driving fluid and a carbon dioxide-containing hydrogen sulfide gas as a suction fluid in an ejector to react the mixed solution and the hydrogen sulfide gas at a prescribed temperature.

Description

  The present invention relates to a method for producing sodium hydrosulfide using an ejector, and more specifically to a method for producing sodium hydrosulfide by reacting a mixed solution of sodium sulfide and sodium hydrosulfide with carbon dioxide-containing hydrogen sulfide.

  Sodium hydrosulfide is used in a wide range of fields such as pulp cooking, ore refining, fur hair removal promotion, viscose rayon desulfurization, wastewater treatment, and thiolation. Recently, high-concentration, high-purity sodium hydrosulfide is required as a raw material for polyphenylene sulfide (PPS) and polysulfide polymer.

  Conventionally, as a method for producing sodium hydrosulfide, a method in which a high-concentration caustic soda solution and a high-concentration hydrogen sulfide gas are brought into contact with each other is known (for example, Patent Document 1). However, in the method described in Patent Document 1, when carbon dioxide gas is contained in the hydrogen sulfide gas, carbonate (sodium carbonate or sodium bicarbonate) may precipitate in the reaction tower and cause clogging. It was necessary to use high-purity hydrogen sulfide gas, and it was difficult to reduce manufacturing costs.

  In contrast, several methods for producing sodium hydrosulfide using carbon dioxide-containing hydrogen sulfide gas have been proposed. For example, in Patent Document 2, carbon dioxide-containing hydrogen sulfide gas (carbon dioxide concentration is 0.5 mol% or less with respect to hydrogen sulfide) and low-concentration caustic soda solution (10 to 30% by weight) are absorbed with two bubble tanks. In a reaction apparatus combining a single tower, a method is described in which a catalytic reaction is carried out while feeding nitrogen gas. Further, in Patent Document 3, contact reaction is performed with hydrogen sulfide gas (hydrogen sulfide concentration 1 to 10 mol%, carbon dioxide concentration 0.1 to 10 mol%) while forming a falling film with a caustic soda solution (20 to 40 wt%). A method is described.

Japanese Patent Laid-Open No. 02-022107 JP 59-026902 A US Pat. No. 3,969,081

  However, in the method described in Patent Document 2, it is necessary to use a large absorption tower in order to flow nitrogen, and there is a problem that the manufacturing cost increases because nitrogen is used in a large amount without being recycled. In addition, when a high-concentration caustic soda solution is used, carbonate may precipitate and the absorption tower may be blocked. Furthermore, there is a possibility that carbonate or sodium sulfide is deposited on the gas feed nozzle and becomes clogged.

  In addition, the method described in Patent Document 3 is a wet wall system in which a large number of tubes are arranged vertically and the liquid flows down along the tube wall, so that the apparatus becomes large and a large installation space is required. In addition, when a high-concentration caustic soda solution is used, carbonate may precipitate and the reaction tube may be blocked or the reaction may be hindered.

  The present invention is to solve such problems and to provide a method for producing sodium hydrosulfide by reacting a mixed solution of sodium hydrosulfide and sodium sulfide with hydrogen sulfide containing carbon dioxide.

  As a result of intensive research to solve the above problems, the inventors of the present invention prepared sodium hydrosulfide and sodium hydrosulfide solution in advance to prepare a mixture of sodium hydrosulfide and sodium sulfide. By reacting carbon dioxide-containing hydrogen sulfide using an ejector, the area of the gas-liquid interface is increased, the reactivity of sodium sulfide and hydrogen sulfide is improved, and the reaction is completed in a short time. It has been found that the device can be prevented from being blocked by crystals of sodium carbonate or sodium bicarbonate produced as a by-product by the reaction of gas with sodium sulfide or sodium hydrosulfide.

In order to solve the above problems, a method for producing sodium hydrosulfide according to the present invention has any one of the following configurations (1) to (4).
(1) a mixing step of mixing a caustic soda solution and a sodium hydrosulfide solution;
In the ejector, the mixed liquid obtained in the mixing step is used as a driving fluid, and a gas-liquid two-phase flow using hydrogen sulfide gas containing carbon dioxide gas as a suction fluid is generated, whereby the mixing is performed at a predetermined reaction temperature. And a reaction step of reacting the liquid with the hydrogen sulfide gas.
(2) In the mixing step, the caustic soda concentration of the caustic soda solution and the sodium hydrosulfide concentration of the sodium hydrosulfide solution are adjusted so that the sodium sulfide concentration in the mixed solution is not more than the solubility at the predetermined reaction temperature. The method for producing a sodium hydrosulfide solution according to claim 1.
(3) The manufacturing method of the sodium hydrosulfide solution of Claim 1 or 2 whose carbon dioxide gas concentration in the said hydrogen sulfide gas is 0.1-20 mol%.
(4) The method for producing a sodium hydrosulfide solution according to any one of claims 1 to 3, wherein at least a part of the reaction liquid discharged from the ejector in the reaction step is returned to the ejector as the driving fluid.

  According to the method for producing sodium hydrosulfide according to the present invention, since the gas-liquid two-phase flow is generated in the ejector and the reaction is performed, even if the gas-liquid contact reaction proceeds rapidly and the carbonate is precipitated. The device will not be blocked. Further, since there is no moving part in the gas phase part, sealing is unnecessary, the risk of gas leakage can be reduced, and the reaction can be performed safely. Furthermore, since there is no need to install a large reaction tower, it is possible to reduce the capital investment without taking up an installation place.

  In addition, the caustic soda solution is not directly reacted with hydrogen sulfide gas, but the caustic soda solution and the sodium hydrosulfide solution are premixed, so that it is possible to prevent the clogging of the reaction intermediate with sodium sulfide, and the caustic soda concentration of the raw material Is applicable to a wide range from low to high concentrations. Furthermore, the concentration of the sodium hydrosulfide solution obtained by the reaction can be applied from a low concentration to a high concentration.

It is a schematic block diagram which shows an example of the apparatus for implementing this invention. It is a model longitudinal cross-sectional view which shows an example of the structure of an ejector. It is a characteristic view which shows the solubility of sodium sulfide with respect to a 47% sodium hydrosulfide solution. It is a schematic diagram which illustrates the state of the gas-liquid two-phase flow in an ejector.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

When caustic soda (NaOH) and hydrogen sulfide (H ₂ S) are reacted directly without mixing the caustic soda solution and the sodium hydrosulfide solution in advance, the following reaction (1) proceeds and sodium sulfide (Na ₂ When S) is generated and the reaction further proceeds, sodium hydrosulfide (NaSH) is generated by the following reaction (2). When the reaction (1) and the reaction (2) are combined, the reaction (3) is obtained.
2NaOH + H ₂ S → Na ₂ S + 2H ₂ O (1)
Na ₂ S + H ₂ S → 2NaSH (2)
NaOH + H ₂ S → NaSH + H ₂ O (3)

  When a high-concentration caustic soda solution (for example, 48% by weight caustic soda solution, which is easily available industrially) is used to react with hydrogen sulfide, sodium sulfide having low solubility is once generated as shown in the reaction (1). . Conventional reaction towers often have a structure in which the flow path of the reaction liquid is finely branched in order to increase the contact area, and the flow path may be blocked by sodium sulfide having low solubility. .

As a method for preventing such blockage by sodium sulfide, a method in which a sodium hydroxide solution is previously mixed with a caustic soda solution can be mentioned. When a sodium hydroxide solution is mixed with a sodium hydroxide solution, the following reaction (4) proceeds quantitatively to produce sodium sulfide. Then, when reacted with hydrogen sulfide, sodium hydrosulfide is produced by the above reaction (2).
NaOH + NaSH → Na ₂ S + H ₂ O (4)

When carbon dioxide (CO ₂ ) is present in the system, sodium carbonate (Na ₂ CO ₃ ) or sodium bicarbonate (NaHCO ₃ ) is obtained by the reaction of carbon dioxide and alkali components shown in (5), (6) and (7) below. Is a by-product. In the production method of the present invention, no reaction (5) occurs because no caustic soda is present in the system.
2NaOH + CO ₂ → Na ₂ CO ₃ + H ₂ O (5)
Na ₂ S + CO ₂ + H ₂ O → Na ₂ CO ₃ + H ₂ S (6)
_{NaSH + CO 2 + H 2 O} → NaHCO 3 + H 2 S ...... (7)

  FIG. 1 is a schematic configuration diagram showing an example of an apparatus for carrying out the method for producing sodium hydrosulfide according to the present invention. In FIG. 1, a production apparatus 12 is provided with a circulation line 10 including an ejector 1, a circulation pump 4, and a heat exchanger 11, and a sodium hydrosulfide solution supplied from a sodium hydrosulfide supply line 9 is supplied in a desired manner. It can be circulated at temperature and flow rate. A caustic soda supply line 7 is provided upstream of the ejector 1, and a mixed liquid of the caustic soda solution and the sodium hydrosulfide solution is supplied to the ejector 1 as a high-pressure driving fluid. Further, hydrogen sulfide gas containing carbon dioxide gas is supplied from the hydrogen sulfide supply line 8 to the ejector 1 as a suction fluid. As a result, a gas-liquid two-phase flow composed of the driving fluid and the suction fluid is generated in the ejector 1, and sodium hydrosulfide is generated by the reaction between the mixed liquid and hydrogen sulfide gas.

  A single tube 2 and a gas-liquid separator 3 are provided downstream of the ejector 1, and the reaction liquid discharged from the ejector 1 is gas-liquid separated in the gas-liquid separator 3. The gas-liquid separator 3 is provided with an off-gas line 6 so that the pressure in the reaction system can be controlled by the off-gas flow rate. And the sodium hydrosulfide solution is obtained by suitably extracting the reaction liquid separated from the gas and liquid from the reaction liquid extraction line 5 and filtering as necessary. A part of the reaction liquid is circulated along the circulation line 10 and returned to the ejector 1 as a driving fluid.

  In the production method of the present invention, the type of ejector is not particularly limited, and a steam ejector or a water ejector that is industrially easily available can be appropriately used. An example of such an ejector is shown in FIG. In FIG. 2, a suction fluid inlet 22 communicating with the suction chamber 23 is provided on the side surface of the ejector 1. In addition, a drive fluid inlet 20 is provided in the upper portion of the ejector 1, and a drive fluid (for example, a mixed solution of sodium hydrosulfide and sodium sulfide) flowing from the drive fluid inlet 20 is injected from the nozzle 21 to the suction chamber 23. Then, the suction fluid (for example, hydrogen sulfide gas containing carbon dioxide gas) flows from the suction fluid inlet 22 into the suction chamber 23, and the drive fluid and the suction fluid are mixed with each other. As a result, the driving fluid and the suction fluid are ejected to the diffuser 24 in a gas-liquid two-phase state, and the gas-liquid contact reaction proceeds rapidly. Thus, when the gas-liquid contact reaction is performed using an ejector, since there is no movable part in the gas phase part, sealing is unnecessary, and the risk of gas leakage can be reduced and the reaction can be performed safely. Further, since there is no need to install a large reaction tower, the apparatus can be downsized.

In the present invention, the caustic soda and hydrogen sulfide are not directly reacted, but the caustic soda solution and the sodium hydrosulfide solution are mixed and converted to sodium sulfide before the reaction. Therefore, the concentration of the caustic soda solution to be used is not limited. It can be selected according to the concentration of the sodium hydrosulfide solution.
For example, when a 47% by weight sodium hydrosulfide solution is to be synthesized, a 48% by weight sodium hydroxide solution is used.

The sodium hydrosulfide solution supplied from the sodium hydrosulfide supply line may be separately synthesized, or may be prepared by dissolving solid sodium hydrosulfide in water.
The concentration of the sodium hydrosulfide solution supplied from the sodium hydrosulfide supply line is selected according to the concentration of the caustic soda solution used and the concentration of the sodium hydrosulfide solution to be synthesized. For example, when it is desired to synthesize a 47 wt% sodium hydrosulfide solution, a 48 wt% sodium hydroxide solution and a 47 wt% sodium hydrosulfide solution are used. When a low concentration sodium hydrosulfide solution is synthesized, the high concentration sodium hydrosulfide solution may be once synthesized and then diluted with water to obtain a low concentration sodium hydrosulfide solution.

When sodium hydroxide is mixed with sodium hydrosulfide solution and the mixture of sodium hydrosulfide and sodium sulfide is adjusted in the circulation line, if too much sodium hydroxide solution is used, the generated sodium sulfide precipitates and the circulation line is blocked. There is a risk. Therefore, it is preferable to control the addition amount of the caustic soda solution so that the amount of sodium sulfide produced is not more than the solubility at the reaction temperature.
For example, when the concentration of the sodium hydrosulfide solution charged in advance is 47% by weight, the solubility of sodium sulfide is as shown in FIG.

  The carbon dioxide gas concentration in the hydrogen sulfide gas is preferably 0.1 to 20 mol%. If the carbon dioxide concentration exceeds 20 mol%, the amount of sodium carbonate or sodium bicarbonate by-product increases, and the slurry concentration increases, which may make pump circulation difficult.

  The reaction temperature in the reaction step is preferably 30 to 100 ° C, more preferably 60 to 100 ° C. When the reaction temperature is lower than 30 ° C., the solubility of sodium sulfide is reduced and productivity is lowered, which is not preferable. On the other hand, if the reaction temperature is higher than 100 ° C., the water may boil when the inside of the reaction system becomes a normal pressure for an unexpected reason, which may make it difficult to control the reaction. Moreover, 100 degrees C or less is preferable also from a viewpoint of suppressing the corrosion of an installation.

The molar ratio of hydrogen sulfide to sodium sulfide (H ₂ S / Na ₂ S) is preferably 1.0 to 2.0, more preferably 1.0 to 1.5. When the molar ratio is lower than 1.0, the amount of unreacted sodium sulfide increases. When the molar ratio is higher than 2.0, the amount of unreacted hydrogen sulfide increases, which is uneconomical and burdens the off-gas treatment process.

  The gas-liquid two-phase flow generated in the ejector in the reaction step changes from a bubble flow → intermittent flow → annular flow → dispersed flow depending on the balance between the gas flow rate and the liquid flow rate. FIG. 4 shows an example of such a change in the gas-liquid two-phase flow, and the ratio of the gas phase increases from the left to the right. When the ratio of the gas phase is small, the state of the bubble flow shown in (A) is shown, but when the ratio of the gas phase increases, the state of the intermittent flow (B) and (C) in which large bubbles almost filling the flow path appear. Become. When the ratio of the gas phase is further increased, a state of an annular flow (D) in which a continuous gas phase exists in the central portion is obtained. And if the ratio of a gaseous phase further increases, it will finally be in the state of a dispersed flow (E). In addition, in FIG. 4, the arrow has shown the flow direction of the gas-liquid two-phase flow. Of these fluid states, the reaction preferably proceeds in an intermittent flow to a dispersed flow state, and more preferably the reaction proceeds in an annular flow to a dispersed flow state. In the bubbling state, when sodium carbonate or sodium bicarbonate is deposited, there is a possibility that the salt is clogged inside the ejector and the reaction cannot be performed.

  As described above, a single pipe can be provided between the ejector outlet and the gas-liquid separator. Since gas-liquid contact occurs even after exiting the ejector, the reaction rate can be changed by changing the length of the single tube.

  In the production method of the present invention, it is preferable that the reaction liquid discharged from the ejector is gas-liquid separated to separate the unreacted gas and the sodium hydrosulfide solution. According to such a configuration, it is possible to prevent mist accompanying the off-gas line. In addition, there is no restriction | limiting in the kind of gas-liquid separator used for gas-liquid separation, What is necessary is just to select an appropriate gas-liquid separator according to implementation conditions.

  Since the sodium hydrosulfide solution separated by the gas-liquid separator may be a slurry of sodium carbonate or sodium bicarbonate depending on the reaction conditions, for example, a filter is installed in the reaction liquid extraction line 5 of FIG. It is preferable. A uniform sodium hydrosulfide solution can be obtained by installing a filter and performing solid-liquid separation of the reaction solution.

  The reaction is more likely to proceed in the pressurized state. The pressure of the system is preferably normal pressure to 1 MPaG, more preferably normal pressure to 0.2 MPaG. If it is 1 MPaG or more, it is subject to high-pressure gas regulation, and there is an increase in equipment costs such as a compressor, which is also not preferable for safety. On the other hand, when the pressure is lower than the normal pressure, the boiling point is lowered, so that a sufficient difference in solubility cannot be obtained and the production efficiency is lowered.

  The present invention will be described below with reference to examples and comparative examples.

(Examples 1-4)
An amount necessary for circulation of the 40-50 wt% sodium hydrosulfide solution was supplied into the apparatus from the sodium hydrosulfide supply line 9, pump circulation was performed according to the flow of the circulation line 10, and the temperature and flow rate were set. Thereafter, a 48% by weight caustic soda solution is introduced from the caustic soda supply line 7 so that the sodium sulfide concentration is not more than the solubility, and hydrogen sulfide gas containing carbon dioxide is added at a molar ratio of hydrogen sulfide to sodium sulfide of 1.0 to It introduced from the hydrogen sulfide supply line 8 so that it might become 1.2, and reaction was advanced. The pressure in the reaction system was controlled by the off-gas flow rate of the off-gas line 6, and the reaction was performed at a constant pressure. Moreover, since the liquid level in the apparatus rose with the progress of the reaction, the reaction liquid was extracted from the reaction liquid extraction line 5, and sodium carbonate was separated by filtration as necessary to obtain a sodium hydrosulfide solution.
The gas composition used is as shown in Table 1. The experimental conditions and results are as shown in Table 2. When each condition was operated for 24 hours, no clogging problem due to crystals occurred under any condition.

(Comparative Example 1)
As shown in Table 3, when the operation was carried out in the same manner as in Example 1 except that the operating conditions were set so that the sodium sulfide concentration was about 10% excess from the solubility, blockage occurred in the control valve. Long-term operation was difficult.

(Comparative Example 2)
As shown in Table 3, when the operation was carried out in the same manner as in Example 1 except that hydrogen sulfide gas containing 21 mol% of carbon dioxide gas was supplied, clogging occurred in the heat exchanger 11 and it was stably continuous. It was difficult to drive.

  According to the method for producing sodium hydrosulfide according to the present invention, the device can be effectively prevented from being blocked by carbonate or sodium sulfide, and the device can be operated stably over a long period of time. Further, since the manufacturing apparatus can be realized with a relatively simple structure having no moving part in the gas phase part, the installation area of the apparatus can be reduced, and the amount of capital investment can be reduced.

DESCRIPTION OF SYMBOLS 1 Ejector 2 Single pipe 3 Gas-liquid separator 4 Circulation pump 5 Reaction liquid extraction line 6 Off gas line 7 Caustic soda supply line 8 Hydrogen sulfide supply line 9 Sodium hydrosulfide supply line 10 Circulation line 11 Heat exchanger 12 Manufacturing apparatus 20 Driving fluid Inlet 21 Nozzle 22 Suction fluid inlet 23 Suction chamber 24 Diffuser

Claims (4)

A mixing step of mixing the caustic soda solution and the sodium hydrosulfide solution;
In the ejector, the mixed liquid obtained by the mixing step is used as a driving fluid, and a gas-liquid two-phase flow using hydrogen sulfide gas containing carbon dioxide as suction fluid is generated, whereby the mixing is performed at a predetermined reaction temperature. And a reaction step of reacting the liquid with the hydrogen sulfide gas.   The caustic soda concentration of the caustic soda solution and a sodium hydrosulfide concentration of the sodium hydrosulfide solution are adjusted so that the sodium sulfide concentration in the mixed solution is not more than the solubility at the predetermined reaction temperature in the mixing step. A method for producing a sodium hydrosulfide solution as described in 1. above.   The manufacturing method of the sodium hydrosulfide solution of Claim 1 or 2 whose carbon dioxide gas concentration in the said hydrogen sulfide gas is 0.1-20 mol%. The method for producing a sodium hydrosulfide solution according to any one of claims 1 to 3, wherein at least a part of the reaction liquid discharged from the ejector in the reaction step is returned to the ejector as the driving fluid.

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