Method for producing phosphorus

Abstract

To efficiently produce phosphorus from a phosphoric acid solution.SOLUTION: A reducing agent and a phosphoric acid solution containing phosphoric acid are charged into a container, and the container is heated while controlling the internal pressure of the container, resulting in the reduction of the phosphoric acid. Preferably, the internal pressure of the container is controlled to a range of 0.12 MPa or less. Preferably, the internal pressure of the container is controlled to a range of 0.03 MPa or more. Preferably, the reducing agent and the phosphoric acid solution are charged into the container such that the mass ratio of the reducing agent to phosphoric acid (reducing agent / phosphoric acid) is 1 / 2-1 / 10.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for producing phosphorus. [Background technology]

[0002] While phosphorus is used in a wide range of fields, including agriculture, food, medicine, and industry, it is a resource that is unevenly distributed around the world, and is only produced in a limited number of countries, including China, the United States, and Morocco. The phosphorus resources circulating in Japan are phosphorus products such as yellow phosphorus and crude phosphoric acid, and the raw material for these, phosphate rock, and the entire supply is imported.

[0003] In recent years, the price of phosphorus resources has been rising sharply due to factors such as the depletion of phosphate rock and the monopolization of phosphate rock by China, the United States, and other countries. As a result, phosphorus in steelmaking slag generated during steel smelting is being reconsidered as a valuable phosphorus resource. However, the phosphorus concentration of the molten iron tapped from a blast furnace is about 0.1 mass%. The phosphorus concentration in the steelmaking slag generated by subjecting this molten iron to conventional treatments (dephosphorization, decarburization refining) is low, at most about 5 mass% in terms of P2O5. For this reason, the phosphorus in the steelmaking slag is not recovered.

[0004] Therefore, studies are being conducted on a method for producing phosphorus from a phosphoric acid solution by reacting the solution with a reducing agent (such as activated carbon) (for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2019-19029 A [Patent Document 2] International Publication No. 2021 / 131231 Summary of the Invention [Problem to be solved by the invention]

[0006] Patent Documents 1 and 2 disclose only conditions such as temperature, and there is room for improvement in terms of the efficiency of phosphorus production.

[0007] The present invention has been made in consideration of the above-mentioned points, and an object of the present invention is to provide a method for efficiently producing phosphorus from a phosphoric acid solution. [Means for solving the problem]

[0008] As a result of extensive investigations, the present inventors have found that the above object can be achieved by employing the following configuration, and have completed the present invention.

[0009] That is, the present invention provides the following [1] to [7]. [1] A method for producing phosphorus, comprising filling a container with a reducing agent and a phosphoric acid solution containing phosphoric acid, and heating the container while controlling the pressure inside the container, thereby reducing the phosphoric acid. [2] The method for producing phosphorus according to [1] above, wherein the pressure inside the vessel is controlled to a range of 0.12 MPa or less. [3] The method for producing phosphorus according to [1] or [2] above, wherein the pressure inside the vessel is controlled to a range of 0.03 MPa or more. [4] The method for producing phosphorus according to any one of [1] to [3] above, wherein the reducing agent and the phosphoric acid solution are filled into the container in amounts such that a mass ratio of the reducing agent to the phosphoric acid (reducing agent / phosphoric acid) is 1 / 2 to 1 / 10. [5] The method for producing phosphorus according to any one of the above [1] to [4], wherein phosphorus is recovered by cooling a gas generated by the reduction of the phosphoric acid. [6] The method for producing phosphorus according to any one of [1] to [5] above, wherein the phosphoric acid solution is dehydrated before the phosphoric acid is reduced. [7] The method for producing phosphorus according to any one of [1] to [6] above, wherein after the reducing agent and the phosphoric acid solution are filled inside the container and before the phosphoric acid is reduced, a granular filler is filled around the reducing agent and the phosphoric acid solution filled inside the container. [8] The method for producing phosphorus described in [7] above, wherein inside the container, the particle size of the filler in the center is larger than the particle size of the filler in the outer periphery. Effect of the Invention

[0010] According to the present invention, phosphorus can be efficiently produced from a phosphoric acid solution. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a cross-sectional view that illustrates a manufacturing apparatus used for manufacturing phosphorus. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The method for producing phosphorus according to this embodiment (hereinafter, for convenience, also referred to as "this production method") will be described below. First, an example of a manufacturing apparatus used in the present manufacturing method will be described with reference to FIG.

[0013] [Manufacturing equipment] FIG. 1 is a cross-sectional view that illustrates a manufacturing apparatus 1 used for manufacturing phosphorus. The production apparatus 1 includes a reaction apparatus 2 and a recovery apparatus 3 . The production apparatus 1 shown in Fig. 1 is a so-called batch type in which a reaction apparatus 2 and a recovery apparatus 3 are provided independently. However, the production apparatus 1 is not limited to the batch type, and may be, for example, a continuous type in which the reaction apparatus 2 on the upstream side and the recovery apparatus 3 on the downstream side are continuously connected.

[0014] The reaction apparatus 2 has a body that can be sealed, and a heat-resistant container 4 is housed inside. The container 4 is made of bricks (MgO-C, alumina silica), for example. By making the container 4 out of bricks, the maintainability is improved compared to when it is made out of other heat-resistant materials such as quartz.

[0015] The reaction apparatus 2 is provided with an atmospheric gas pipe 5 for introducing an atmospheric gas (for example, carbon monoxide) into the reaction apparatus 2. A pressure measuring device 15 for measuring the pressure inside the reactor 2 is disposed in the reactor 2 . A pressure control device 8 that controls the pressure inside the reaction device 2 is connected to the reaction device 2. The pressure control device 8 is, for example, a compressor, a vacuum pump, or the like.

[0016] A temperature measuring device 16 for measuring the temperature inside the reactor 2 is disposed in the reactor 2 . The production apparatus 1 has a heating device 7. By driving the heating device 7, the inside of the reaction apparatus 2 is heated to a desired temperature.

[0017] The recovery device 3 has a body that can be sealed, and stores therein cooling water 9 for cooling the generated gas, which will be described later.

[0018] The reaction device 2 and the recovery device 3 are connected by an evolved gas pipe 6. The evolved gas (for example, gaseous phosphorus described later) generated inside the reaction device 2 is introduced into the recovery device 3 via the evolved gas pipe 6. The generated gas pipe 6 may be provided with a valve (not shown) in the middle thereof for controlling the passage of the generated gas.

[0019] An exhaust gas pipe 10 is connected to the recovery device 3. The gas (exhaust gas) inside the recovery device 3 is discharged to the outside of the recovery device 3 through the exhaust gas pipe 10. The exhaust gas pipe 10 may connect the reaction device 2 and the recovery device 3. In this case, the gas (exhaust gas) inside the recovery device 3 is introduced into the reaction device 2 through the exhaust gas pipe 10. When the exhaust gas pipe 10 connects the reaction device 2 and the recovery device 3, it is preferable that a water absorbing material that absorbs moisture in the exhaust gas is provided midway in the exhaust gas pipe 10. A valve (not shown) for controlling the passage of exhaust gas may be provided midway in the exhaust gas pipe 10.

[0020] [Manufacturing method] Next, the present manufacturing method will be described with reference to FIG.

[0021] <filling> First, a reducing agent and a phosphoric acid solution containing phosphoric acid are placed inside the container 4, and then the reducing agent is uniformly dispersed by stirring. In this way, a mixture 12 of the reducing agent and the phosphoric acid solution is filled inside the container 4. In the mixture 12, the phosphoric acid solution is impregnated with the reducing agent.

[0022] The reducing agent may, for example, be activated carbon or free carbon. The phosphoric acid solution is, for example, an aqueous solution of phosphoric acid. The phosphoric acid contained in the phosphoric acid solution may be phosphoric acid extracted from steelmaking slag or other phosphoric acid. As a method for extracting phosphoric acid from steelmaking slag, a known method can be appropriately adopted.

[0023] If the amount of phosphoric acid is too small relative to the amount of reducing agent, the amount of phosphorus produced from phosphoric acid will be small, and the phosphorus production efficiency will tend to be insufficient. On the other hand, if the amount of phosphoric acid is too large relative to the amount of reducing agent, the reactivity between phosphoric acid and the reducing agent will tend to be insufficient. For this reason, the mass ratio of the reducing agent and phosphoric acid filled inside the container 4 (reducing agent / phosphoric acid) is preferably 1 / 2 to 1 / 10, and more preferably 1 / 3 to 1 / 8. In other words, it is preferable to impregnate the reducing agent with 2 to 10 times the amount of phosphoric acid. 10 This makes it easier for the catalyst to come into contact with the reducing agent, thereby increasing the efficiency of phosphorus production.

[0024] Thereafter, the container 4 filled with the mixture 12 of the reducing agent and the phosphoric acid solution is placed in the reaction apparatus 2 and sealed. At this time, if the phosphoric acid solution (phosphoric acid) is reacted only with the reducing agent in the mixture 12, not all of it will be reduced to phosphorus, and some of it may evaporate unreduced (unreacted). Therefore, it is preferable to place a filler 13 on the upper side of the mixture 12 inside the container 4. This allows the unreduced phosphoric acid to be reduced by the filler 13 as well, thereby improving the yield of recovered phosphorus. Similarly, it is preferable to place a filler 13 between the main body of the reaction device 2 and the container 4. For example, a reducing agent such as granular activated carbon is used as the filler 13. The reducing agent used as the filler 13 is distinguished from the reducing agent constituting the mixture 12 (the reducing agent impregnated with the phosphoric acid solution).

[0025] Incidentally, it is generally known that inside a container, the porosity of granular material is greater on the wall side (outer periphery) than in the center (so-called wall effect). If the porosity of the granular filler 13 differs between the center and the outer periphery inside the container 4, a difference in reaction with the filler 13 may occur when the phosphoric acid solution is reduced.

[0026] For this reason, inside the container 4, the particle size of the filler 13 in the center is preferably larger than the particle size of the filler 13 in the outer periphery (the wall side of the container 4). This can reduce the influence of the wall effect. That is, inside the container 4, the reaction between the filler 13 and the phosphoric acid solution can be made uniform, so that the phosphoric acid solution can be reduced more efficiently.

[0027] As a method for changing the particle size of the filler 13 between the center and the outer periphery inside the container 4, for example, the following three methods (Methods A to C) can be mentioned. Method A: The particle size of the filler 13 is changed from the center to the outer periphery (wall side of the container 4) inside the container 4. Specifically, for example, the particle size of the filler 13 in the center is set to 2 mm, and the particle size in the outer periphery (wall side of the container 4) is set to 0.5 mm. The particle size between the center and outer periphery (intermediate portion) is set to an intermediate particle size between the two. The particle size of the filler 13 may be changed linearly according to the distance (thickness) in the intermediate portion. Method B: The inside of the container 4 is filled with fillers 13 having different particle sizes in a concentric circle pattern. Specifically, for example, from the center to the outer periphery, the circles are 2 mm in diameter, 1 mm in diameter, and 0.5 mm in diameter. The thickness of each circle is appropriately set. Method C: Fillers 13 having different particle sizes are used instead of fillers 13 consisting of a single particle size.

[0028] The method for measuring the particle diameter is not particularly limited as long as it is the same for the central portion and the outer periphery. For example, the particle size may be a particle size (median size) equivalent to an integrated value of 50% in a volume-based particle size distribution determined by a laser diffraction / scattering method, or may be a particle size determined by sieving or the like.

[0029] <dehydration> The phosphoric acid solution (aqueous phosphoric acid solution) used in the present production method is preferably dehydrated to increase its concentration, which makes it possible to produce phosphorus from the phosphoric acid solution more efficiently and also makes it possible to prevent steam explosion during the reduction process described below. Specifically, the phosphoric acid concentration of the phosphoric acid solution after dehydration is preferably 80% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass or more.

[0030] The method for dehydrating the phosphoric acid solution is not particularly limited, and the reaction device 2 may be used, or a dehydration device (not shown) separate from the reaction device 2 may be used.

[0031] When dehydrating using a dehydrator, the phosphoric acid solution is placed inside the dehydrator and then heated to evaporate the water in the phosphoric acid solution. After that, the dehydrated phosphoric acid solution and a reducing agent are filled into the container 4, and the container 4 is placed in the reaction device 2.

[0032] When dehydration is performed using the reaction apparatus 2, first, as described above, the phosphoric acid solution and the reducing agent are placed in the container 4 and then stirred, and the container 4 filled with the mixture 12 is placed in the reaction apparatus 2. Thereafter, the heating device 7 is driven to heat the container 4 (more specifically, the mixture 12 filled in the container 4) contained in the reaction device 2. In this way, the phosphoric acid solution constituting the mixture 12 is heated to evaporate water.

[0033] If the temperature (dehydration temperature) at which the phosphoric acid solution is heated for dehydration is too high, the phosphoric acid itself is likely to evaporate. Therefore, the dehydration temperature is preferably less than 300° C., and more preferably 290° C. or lower. There is no particular lower limit, and the dehydration temperature is, for example, 200° C. or higher, and more preferably 250° C. or higher.

[0034] It is preferable to stir (mix) the phosphoric acid solution and the reducing agent in the container 4 before dehydration. By dehydrating after stirring, a solid reducing agent impregnated with the highly concentrated phosphoric acid solution is obtained as the mixture 12, which is easy to handle.

[0035] When the phosphoric acid solution used in the present production method is initially highly concentrated, dehydration is not necessary.

[0036] <reduction> The container 4 filled with the mixture 12 is housed in the reaction device 2, and the heating device 7 is driven in a state where the reaction device 2 is sealed. In this way, the inside of the reaction device 2 (particularly the container 4) is heated in order to reduce the phosphoric acid solution constituting the mixture 12. The temperature at which the phosphoric acid solution is heated for reduction (reduction temperature) is preferably 800° C. or higher, and more preferably 900° C. or higher. On the other hand, the reduction temperature is preferably 1200° C. or lower, and more preferably 1000° C. or lower. The heating time at the reduction temperature is not particularly limited, and is, for example, 0.5 to 2 hours.

[0037] As a result, the reactions represented by the following formulas (1) to (3) proceed, and phosphoric acid (H3PO4) in the phosphoric acid solution is reduced by the activated carbon (C) serving as a reducing agent, to produce gaseous phosphorus (P4). 4H3PO4+10C→P4+6H2O+10CO...(1) 6C+6H2O→6H2+6CO (2) 4H3PO4+16C→6H2+16CO+P4...(3)

[0038] At this time, it is preferable to introduce an atmospheric gas (for example, carbon monoxide) from the atmospheric gas pipe 5 into the inside of the reaction apparatus 2 (particularly, the vessel 4) in conjunction with the heating at the reduction temperature.

[0039] Incidentally, the inside of the reaction device 2 is at, for example, atmospheric pressure, and when the atmospheric gas is introduced into the reaction device 2, the pressure becomes higher than atmospheric pressure (for example, 0.20 MPa). Therefore, in this production method, in addition to the introduction of the atmospheric gas, the pressure control device 8 is driven to control the pressure inside the reaction device 2 (particularly, the vessel 4). More specifically, the pressure inside the reaction device 2 is reduced. As a result, in the reaction (reduction reaction) represented by the above formulas (1) to (3), the product on the right side decreases, the reaction shifts to the right side, and the generation of gaseous phosphorus (P4) is promoted. Thus, phosphorus can be efficiently obtained from the phosphoric acid solution.

[0040] Specifically, the pressure inside the reaction apparatus 2 (particularly, the vessel 4) is preferably 0.18 MPa or less, more preferably 0.15 MPa or less, further preferably 0.12 MPa or less, and particularly preferably 0.10 MPa or less.

[0041] On the other hand, if the pressure inside the reaction device 2 is reduced too much, the components necessary for the reaction may be excessively reduced. Therefore, the pressure inside the reaction device 2 (particularly, the vessel 4) is preferably 0.03 MPa or more, more preferably 0.05 MPa or more, and even more preferably 0.08 MPa or more.

[0042] In this specification, all pressure values ​​are gauge pressure values.

[0043] <collect> In the reaction device 2, the evolved gas generated by the reduction of phosphoric acid contains gaseous phosphorus. It is preferable to cool the gaseous phosphorus contained in this evolved gas and recover it as liquid phosphorus or solid phosphorus (yellow phosphorus).

[0044] Specifically, for example, the valve of the generated gas pipe 6 is opened (at this time, the valve of the exhaust gas pipe 10 is closed). In this way, the generated gas generated inside the reaction device 2 is introduced into the recovery device 3 through the generated gas pipe 6. The generated gas introduced into the recovery device 3 is cooled by passing through cooling water 9. The melting point of yellow phosphorus is 44.1° C. By cooling with cooling water 9, the gaseous phosphorus contained in the generated gas is recovered as liquid phosphorus (when the temperature of the cooling water is 44.1° C. or higher) or solid phosphorus (when the temperature of the cooling water is less than 44.1° C.). Inside the recovery device 3 shown in FIG. 1, yellow phosphorus 14, which is solid phosphorus, is shown below the cooling water 9.

[0045] The resulting yellow phosphorus 14 can be recovered as phosphoric acid by contacting it with air and oxidizing it. The cooling water 9 also contains unreacted phosphoric acid.

[0046] The generated gas (exhaust gas) after recovering gaseous phosphorus as liquid phosphorus or solid phosphorus is discharged to the outside of the recovery device 3 via an exhaust gas pipe 10. However, the generated gas generated inside the reaction device 2 contains not only gaseous phosphorus but also a large amount of carbon monoxide. Therefore, the gaseous phosphorus contained in the generated gas may be recovered as liquid phosphorus or solid phosphorus, and then the generated gas may be reused. Specifically, for example, the reaction device 2 and the recovery device 3 are connected by an exhaust gas pipe 10, and the valve of the exhaust gas pipe 10 is opened (at this time, the valve of the generated gas pipe 6 is closed). As a result, the generated gas (exhaust gas) from which gaseous phosphorus has been recovered is introduced from inside the recovery device 3 into the reaction device 2 via the exhaust gas pipe 10. At this time, by providing a water absorbing material midway through the exhaust gas pipe 10, the generated gas (exhaust gas) from which gaseous phosphorus has been recovered can be introduced into the reaction device 2 while being dried by the water absorbing material. EXAMPLES

[0047] The present invention will be specifically described below with reference to examples, although the present invention is not limited to the examples described below.

[0048] Example 1 Using the production apparatus 1 explained based on FIG. 1, phosphorus was produced from a phosphoric acid solution according to the present production method described above. As the phosphoric acid solution, an aqueous phosphoric acid solution (phosphoric acid concentration: 80% by mass) was used. The inside of the container 4 was filled with a mixture 12 in which a reducing agent (free carbon) was impregnated with a phosphoric acid solution in a mass ratio (reducing agent / phosphoric acid) of 1 / 3.5. The container 4 filled with the mixture 12 was placed inside the reactor 2 and sealed. Granular activated carbon was filled as the filler 13 above the mixture 12 inside the container 4 and between the container 4 and the main body of the reactor 2. While introducing carbon monoxide as atmospheric gas from the atmospheric gas pipe 5 into the inside of the reaction device 2, the heating device 7 was driven to heat the mixture 12 at a reduction temperature of 1000°C for 1 hour to obtain a generated gas. At this time, the pressure control device 8 was driven to heat the mixture 12 while reducing the pressure inside the reaction device 2 (vessel 4) to 0.08 MPa. The evolved gas obtained in the reaction device 2 was introduced into the recovery device 3 and cooled with cooling water 9 to obtain a solid product. The obtained product was confirmed to be yellow phosphorus by Raman spectroscopic analysis (hereinafter the same). That is, yellow phosphorus 14 was recovered. The total yield of the recovered yellow phosphorus 14 and the phosphoric acid dissolved in the cooling water 9 (hereinafter, also simply referred to as "yield") was 70 mass %.

[0049] Example 2 In Example 2, mixture 12 was filled into container 4, and then heated at a dehydration temperature of 280° C. before being heated for 1 hour at a reduction temperature of 1000° C. to dehydrate the phosphoric acid solution constituting mixture 12. The phosphoric acid concentration of the phosphoric acid solution after dehydration was 83 mass%. Except for this, the yellow phosphorus 14 was recovered in the same manner as in Example 1. The yield of Example 2 was 75% by mass.

[0050] Example 3 In the third embodiment, the method of filling the filler 13 was changed in order to reduce the influence of the wall effect. More specifically, in Example 3, the center of the inside of the container 4 was filled with filler 13 having a particle size of 2 mm, the outer periphery (the wall side of the container 4) was filled with filler 13 having a particle size of 0.5 mm, and the intermediate portion between the center and the outer periphery was filled with filler 13 having a particle size of 1 mm. Except for this, the yellow phosphorus 14 was recovered in the same manner as in Example 2. The yield of Example 3 was 83% by mass.

[0051] Comparative Example 1 In Comparative Example 1, the pressure inside the reaction device 2 was not reduced when the mixture 12 was heated at a reduction temperature of 1000° C. for 1 hour. Therefore, the pressure inside the reaction device 2 (container 4) was 0.20 MPa during heating at the reduction temperature. Except for this, the yellow phosphorus 14 was recovered in the same manner as in Example 1. The yield in Comparative Example 1 was 55% by mass.

[0052] Comparative Example 2 In Comparative Example 2, the pressure inside the reaction device 2 was not reduced when the mixture 12 was heated at a reduction temperature of 1000° C. for 1 hour. Therefore, the pressure inside the reaction device 2 (container 4) was 0.20 MPa during heating at the reduction temperature. Except for this, the yellow phosphorus 14 was recovered in the same manner as in Example 2. The yield in Comparative Example 2 was 59% by mass.

[0053] <Summary of evaluation results> Examples 1 to 3, in which pressure control (reduced pressure) was performed when heating the phosphoric acid solution (reduction of phosphoric acid), had a higher phosphorus yield than Comparative Examples 1 and 2, in which this was not performed. In Comparative Examples 1 and 2 in which pressure control was not performed, it is believed that the pressure inside the reaction device 2 (vessel 4) increased during the reduction reaction, resulting in less generation of gaseous phosphorus.

[0054] Comparing Example 1 and Example 2, Example 2 in which dehydration was performed before reduction had a higher phosphorus yield than Example 1 in which dehydration was not performed.

[0055] Furthermore, comparing Examples 1 and 2 with Example 3, Example 3 in which the particle size of the filler 13 was adjusted had a higher phosphorus yield than Examples 1 and 2 in which the particle size was not adjusted. In Examples 1 and 2, wear of the filler 13 on the outer periphery (the wall side of the container 4) was greater than that in Example 3, and this is thought to have reduced the contact efficiency between the filler 13 and the vaporized phosphoric acid. [Explanation of symbols]

[0056] 1: Manufacturing equipment 2: Reactor 3: Recovery device 4: Container 5: Atmospheric gas pipe 6: Gas generating pipe 7:Heating device 8: Pressure control device 9: Cooling water 10: Exhaust gas pipe 12:Mixture 13: Filling material 14: Yellow phosphorus 15: Pressure measuring device 16:Temperature measuring device

Claims

1. A reducing agent and a phosphoric acid solution containing phosphoric acid are filled into the inside of the container, The method for producing phosphorus comprises heating the container while controlling the pressure inside the container, thereby reducing the phosphoric acid.

2. The method for producing phosphorus according to claim 1 , wherein the pressure inside the vessel is controlled to a range of 0.12 MPa or less.

3. The method for producing phosphorus according to claim 1 or 2, wherein the pressure inside the vessel is controlled to a range of 0.03 MPa or more.

4. The method for producing phosphorus according to claim 1 or 2, wherein the reducing agent and the phosphoric acid solution are filled into the container in amounts such that a mass ratio of the reducing agent to the phosphoric acid (reducing agent / phosphoric acid) is 1 / 2 to 1 / 10.

5. 3. The method for producing phosphorus according to claim 1, wherein phosphorus is recovered by cooling a gas generated by the reduction of the phosphoric acid.

6. The method for producing phosphorus according to claim 1 or 2, wherein the phosphoric acid solution is dehydrated before the phosphoric acid is reduced.

7. 3. The method for producing phosphorus according to claim 1, further comprising the step of filling a granular filler around the reducing agent and the phosphoric acid solution filled in the container after the reducing agent and the phosphoric acid solution are filled in the container and before the phosphoric acid is reduced.

8. The method for producing phosphorus according to claim 7 , wherein inside the container, the particle size of the filler in the center portion is larger than the particle size of the filler in the outer periphery portion.

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