Phosphorus production methods

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 Art

[0002] Phosphorus is used in a wide range of fields such as agriculture, food, medicine, and industry, while it is a resource that is unevenly distributed globally, and the producing countries are limited to China, the United States, Morocco, etc. Phosphorus resources circulating in Japan are phosphorus products such as yellow phosphorus and crude phosphoric acid, or phosphate ore which is the raw material thereof, and the total amount depends on imports.

[0003] In recent years, due to reasons such as the depletion of phosphate ore and the encirclement of phosphate ore by China, the United States, etc., the price of phosphorus resources has been soaring, so the phosphorus in steelmaking slag generated during steelmaking has been regarded as a precious phosphorus resource. However, the phosphorus concentration in hot metal tapped from a blast furnace is about 0.1% by mass. And the phosphoric acid concentration in steelmaking slag generated by subjecting this hot metal to conventional general treatments (phosphorus removal treatment, decarburization refining) is at most about 5% by mass in terms of P2O5, which is low. Therefore, the phosphorus in steelmaking slag has not been recovered.

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

Prior Art Documents

[0007] This invention has been made in view of the above points, and aims to provide a method for efficiently producing phosphorus from a phosphoric acid solution. [Means for solving the problem]

[0008] As a result of diligent research, the inventors of this invention discovered that the above objective can be achieved by adopting the following configuration, and thus completed the present invention.

[0009] In other words, 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 reducing the phosphoric acid by heating the container while controlling the pressure inside the container. [2] The method for producing phosphorus according to [1] above, wherein the pressure inside the above container is controlled to be within the range of 0.12 MPa or less. [3] A method for producing phosphorus according to [1] or [2] above, wherein the pressure inside the above container is controlled to be in the range of 0.03 MPa or higher. [4] A 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 an amount such that the mass ratio of the reducing agent to the phosphoric acid (reducing agent / phosphoric acid) is 1 / 2 to 1 / 10. [5] A method for producing phosphorus according to any one of [1] to [4] above, wherein phosphorus is recovered by cooling the gas generated by the reduction of phosphoric acid. [6] A method for producing phosphorus according to any one of [1] to [5] above, wherein the phosphoric acid solution is dehydrated before reducing the phosphoric acid. [7] A method for producing phosphorus according to any one of [1] to [6] above, wherein after filling the container with the reducing agent and the phosphoric acid solution, and before reducing the phosphoric acid, granular filler is filled around the reducing agent and the phosphoric acid solution filled inside the container. [8] The method for producing phosphorus according to [7], 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. [Effects of the Invention]

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

[0011] [Figure 1] This is a schematic cross-sectional view showing a manufacturing apparatus used for phosphorus production. [Modes for carrying out the invention]

[0012] The method for producing phosphorus according to this embodiment (hereinafter also referred to as "this production method" for convenience) will be described below. First, an example of the manufacturing equipment used in this manufacturing method will be explained based on Figure 1.

[0013] [Manufacturing equipment] Figure 1 is a schematic cross-sectional view showing a manufacturing apparatus 1 used for phosphorus production. The manufacturing apparatus 1 includes a reaction apparatus 2 and a recovery apparatus 3. The manufacturing apparatus 1 shown in Figure 1 is a so-called batch type, in which the reaction apparatus 2 and the recovery apparatus 3 are provided independently. However, the manufacturing apparatus 1 is not limited to a batch type; for example, it may be a continuous type in which the upstream reaction apparatus 2 and the downstream recovery apparatus 3 are connected in a continuous manner.

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

[0015] The reactor 2 is equipped with an atmospheric gas pipe 5 for introducing an atmospheric gas (for example, carbon monoxide) into the reactor 2. A pressure measuring device 15 for measuring the pressure inside the reaction device 2 is arranged in the reaction device 2. A pressure control device 8 for controlling 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 reaction device 2 is arranged in the reaction device 2. The manufacturing device 1 has a heating device 7. By driving the heating device 7, the inside of the reaction device 2 is heated to a desired temperature.

[0017] The recovery device 3 has a hermetically sealable main body, and cooling water 9 for cooling the generated gas described later is stored inside.

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

[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 via the exhaust gas pipe 10. Note that 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 via 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 absorbent for absorbing the moisture of the exhaust gas is provided in the middle of the exhaust gas pipe 10. A valve (not shown) for controlling the passage of the exhaust gas may be provided in the middle of the exhaust gas pipe 10.

[0020] [Manufacturing Method] Next, based on FIG. 1, this manufacturing method will be described.

[0021] 〈Filling〉 First, the reducing agent and a phosphoric acid solution containing phosphoric acid are placed inside container 4, and then the mixture is stirred to uniformly disperse the reducing agent. In this way, the mixture 12 of the reducing agent and phosphoric acid solution is filled inside container 4. In the mixture 12, the phosphoric acid solution is impregnated with the reducing agent.

[0022] Examples of reducing agents include activated carbon and 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. A known method can be appropriately used to extract phosphoric acid from steelmaking slag.

[0023] If the amount of phosphoric acid is too small relative to the amount of reducing agent, the amount of phosphorus produced from the phosphoric acid will be small, and the efficiency of phosphorus production will likely 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 the phosphoric acid and the reducing agent will likely be insufficient. Therefore, the mass ratio (reducing agent / phosphoric acid) of the reducing agent to phosphoric acid filled inside container 4 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. This allows the P4O produced by heating the phosphoric acid to be released. 10 This makes it easier for the phosphorus to come into contact with the reducing agent, increasing the efficiency of phosphorus production.

[0024] Subsequently, the container 4 filled with the mixture 12 of the reducing agent and phosphoric acid solution is placed in the reaction apparatus 2 and sealed. In this case, if the phosphoric acid solution (phosphoric acid) is reacted only with the reducing agent in mixture 12, not all of it may be reduced to phosphorus, and some may vaporize while remaining unreduced (unreacted). Therefore, it is preferable to place the packing material 13 on top of the mixture 12 inside the container 4. This allows the unreduced phosphoric acid to be reduced by the packing material 13 as well, thereby improving the yield of recovered phosphorus. Similarly, it is also preferable to place the packing material 13 between the main body of the reaction apparatus 2 and the container 4. For example, a reducing agent such as granular activated carbon can be used as the filler material 13. The reducing agent used as the filler material 13 is distinct from the reducing agent that constitutes the mixture 12 (the reducing agent impregnated with phosphoric acid solution).

[0025] Incidentally, it is generally known that inside a container, the porosity of granular material is greater towards the walls (outer periphery) than in the center (the so-called wall effect). If the porosity of the granular packing material 13 differs between the central and outer parts of the container 4, differences may occur in the reaction with the packing material 13 when reducing the phosphoric acid solution.

[0026] Therefore, within the container 4, it is preferable that the particle size of the filler 13 in the center is larger than the particle size of the filler 13 in the outer periphery (the wall side of the container 4). This reduces the effect of the wall. In other words, the reaction between the filler 13 and the phosphoric acid solution can be made more uniform inside the container 4, allowing for more efficient reduction of the phosphoric acid solution.

[0027] Three methods (Methods A to C) can be used to vary the particle size of the filler 13 between the center and the outer periphery of the container 4. Method A: The particle size of the filler 13 is varied from the center to the outer periphery (the 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 (the wall side of the container 4) is set to 0.5 mm. The particle size in the area between the center and the outer periphery (the intermediate area) 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) of the intermediate area. Method B: Inside the container 4, filler material 13 having different particle sizes is filled in a concentric pattern. Specifically, for example, circles with particle sizes of 2 mm, 1 mm, and 0.5 mm are formed from the center outwards. The thickness of each circle is set as appropriate. Method C: Instead of using a filler 13 consisting of a single particle size, use a filler 13 having different particle sizes.

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

[0029] <dehydration> In this manufacturing method, it is preferable to dehydrate the phosphoric acid solution (aqueous phosphoric acid solution) to increase its concentration. This allows for more efficient production of phosphorus from the phosphoric acid solution and suppresses steam explosions during the reduction process described later. Specifically, the phosphoric acid concentration of the phosphoric acid solution after dehydration is preferably 80% by mass or higher, more preferably 85% by mass or higher, and even more preferably 90% by mass or higher.

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

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

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

[0033] If the temperature at which the phosphoric acid solution is heated for dehydration (dehydration temperature) is too high, the phosphoric acid itself will evaporate easily. For this reason, the dehydration temperature is preferably less than 300°C, and more preferably 290°C or lower. There is no particular lower limit; 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 reducing agent in container 4 before dehydration. By dehydrating after stirring, a solid material of the reducing agent impregnated with a highly concentrated phosphoric acid solution is obtained as mixture 12, which facilitates handling.

[0035] Furthermore, if the phosphoric acid solution used in this manufacturing method is already highly concentrated, dehydration may not be necessary.

[0036] <reduction> With the container 4 filled with mixture 12 placed in the reaction apparatus 2 and the reaction apparatus 2 sealed, the heating device 7 is activated. In this way, the inside of the reaction apparatus 2 (particularly container 4) is heated in order to reduce the phosphoric acid solution that constitutes 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, but can be, for example, 0.5 to 2 hours.

[0037] As a result, the reaction represented by the following equations (1) to (3) proceeds, and the phosphoric acid (H3PO4) in the phosphoric acid solution is reduced by the reducing agent activated carbon (C) to obtain 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 reaction apparatus 2 (especially the container 4) in conjunction with heating at the reduction temperature.

[0039] Incidentally, the pressure inside reactor 2 is, for example, atmospheric pressure, and when an atmospheric gas is introduced into reactor 2, the pressure becomes higher than atmospheric pressure (for example, 0.20 MPa). Therefore, in this manufacturing method, the pressure control device 8 is driven in conjunction with the introduction of the atmospheric gas to control the pressure inside the reactor 2 (particularly the container 4). More specifically, the pressure inside the reactor 2 is reduced. As a result, in the reactions (reduction reactions) represented by equations (1) to (3) above, the product on the right-hand side decreases, the reaction shifts to the right-hand side, and the generation of gaseous phosphorus (P4) is promoted. In this way, phosphorus can be efficiently obtained from a phosphoric acid solution.

[0040] The internal pressure of the reaction apparatus 2 (especially the container 4) is preferably 0.18 MPa or less, more preferably 0.15 MPa or less, even more preferably 0.12 MPa or less, and particularly preferably 0.10 MPa or less.

[0041] On the other hand, if the pressure inside the reactor 2 is reduced too much, the components necessary for the reaction may be excessively reduced. For this reason, the pressure inside the reactor 2 (especially the container 4) is preferably 0.03 MPa or higher, more preferably 0.05 MPa or higher, and even more preferably 0.08 MPa or higher.

[0042] Note that all pressure values ​​in this specification are gauge pressure values.

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

[0044] Specifically, for example, the valve on the gas generation pipe 6 is opened (while the valve on the exhaust gas pipe 10 is closed). In this way, the gas generated inside the reactor 2 is introduced into the recovery device 3 via the gas generation pipe 6. The generated gas introduced into the recovery device 3 is cooled by passing through the cooling water 9. The melting point of yellow phosphorus is 44.1°C. Cooling with cooling water 9 recovers the gaseous phosphorus contained in the generated gas as liquid phosphorus (if the cooling water temperature is 44.1°C or higher) or solid phosphorus (if the cooling water temperature is below 44.1°C). Inside the recovery device 3 shown in Figure 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 oxidizing it in contact with air. The cooling water 9 also contains unreacted phosphoric acid.

[0046] The gas (exhaust gas) generated after recovering gaseous phosphorus as liquid or solid phosphorus is discharged outside the recovery device 3 via the exhaust gas pipe 10. However, the gas generated inside the reaction apparatus 2 contains not only gaseous phosphorus but also a large amount of carbon monoxide. For this reason, the gaseous phosphorus contained in the generated gas may be recovered as liquid or solid phosphorus before the generated gas can be reused. Specifically, for example, the reactor 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 into the reactor 2 from inside the recovery device 3, via the exhaust gas pipe 10. At this time, by installing a water-absorbing material in the middle of the exhaust gas pipe 10, the generated gas (exhaust gas) from which gaseous phosphorus has been recovered can be introduced into the reactor 2 while being dried by the water-absorbing material. [Examples]

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

[0048] <Example 1> Using the manufacturing apparatus 1 described in Figure 1, phosphorus was produced from a phosphoric acid solution according to the manufacturing method described above. As the phosphoric acid solution, an aqueous phosphoric acid solution (phosphoric acid concentration: 80% by mass) was used. A mixture 12, in which a phosphoric acid solution was impregnated with a reducing agent (free carbon) in a mass ratio of 1 / 3.5 (reducing agent / phosphoric acid), was filled into the container 4. A container 4 filled with the mixture 12 was placed inside the reactor 2 and sealed. Granular activated carbon was packed as a packing material 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, which is the atmospheric gas, into the reactor 2 from the atmospheric gas pipe 5, the heating device 7 was driven to heat the mixture 12 at a reduction temperature of 1000°C for 1 hour to obtain the generated gas. At the same time, the pressure control device 8 was driven to reduce the pressure inside the reactor 2 (container 4) to 0.08 MPa while heating the mixture 12. The gas generated in reaction apparatus 2 was introduced into recovery apparatus 3 and cooled with cooling water 9 to obtain a solid product. The obtained product was confirmed to be yellow phosphorus by Raman spectroscopy (the same applies hereafter). In other words, yellow phosphorus 14 was recovered. The total yield (hereinafter simply referred to as "yield") of the recovered yellow phosphorus 14 and the phosphoric acid dissolved in the cooling water 9 was 70% by mass.

[0049] <Example 2> In Example 2, after filling the container 4 with mixture 12, the mixture was heated at a dehydration temperature of 280°C to dehydrate the phosphoric acid solution constituting mixture 12 before heating at a reduction temperature of 1000°C for 1 hour. The phosphoric acid concentration of the phosphoric acid solution after dehydration was 83% by mass. Otherwise, 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 Example 3, the method of filling the filler 13 was changed in order to reduce the effect of the wall. More specifically, in Example 3, the center of the container 4 was filled with a filler material 13 with a particle size of 2 mm, the outer periphery (the wall side of the container 4) was filled with a filler material 13 with a particle size of 0.5 mm, and the intermediate part between the center and the outer periphery was filled with a filler material 13 with a particle size of 1 mm. Otherwise, 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 inside of the reaction apparatus 2 was not depressurized when the mixture 12 was heated at a reduction temperature of 1000°C for 1 hour. Therefore, the pressure inside the reaction apparatus 2 (container 4) was 0.20 MPa during heating at the reduction temperature. Otherwise, yellow phosphorus 14 was recovered in the same manner as in Example 1. The yield of Comparative Example 1 was 55% by mass.

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

[0053] <Summary of Evaluation Results> Examples 1-3, in which pressure control (reduced pressure) was implemented during the heating of the phosphoric acid solution (reduction of phosphoric acid), showed a higher phosphorus yield compared to Comparative Examples 1-2, in which this control was not implemented. In Comparative Examples 1 and 2, where pressure control was not implemented, it is thought that the pressure inside the reaction apparatus 2 (container 4) increased during the reduction reaction, resulting in less gaseous phosphorus being produced.

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

[0055] Furthermore, comparing Examples 1-2 with Example 3, Example 3, in which the particle size of the filler 13 was adjusted, showed an even higher phosphorus yield than Examples 1-2, in which the particle size was not adjusted. In Examples 1 and 2, the consumption of the filler material 13 on the outer periphery (the wall side of the container 4) was more severe than in Example 3, suggesting that the contact efficiency between the filler material 13 and the vaporized phosphoric acid was reduced. [Explanation of Symbols]

[0056] 1: Manufacturing equipment 2: Reactor 3: Recovery device 4: Container 5: Atmosphere gas pipe 6: Gas generation pipe 7:Heating device 8: Pressure control device 9: Cooling water 10: Exhaust 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 container. A method for producing phosphorus, comprising heating the container while controlling the internal pressure of the container to a range of 0.18 MPa or less, thereby reducing the phosphoric acid.

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

3. A method for producing phosphorus according to claim 1 or 2, wherein the pressure inside the container is controlled to be in the range of 0.03 MPa or higher.

4. A 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 an amount such that the mass ratio of the reducing agent to the phosphoric acid (reducing agent / phosphoric acid) is 1 / 2 to 1 / 10.

5. A method for producing phosphorus according to claim 1 or 2, wherein phosphorus is recovered by cooling the gas generated by the reduction of the phosphoric acid.

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

7. A method for producing phosphorus according to claim 1 or 2, wherein, after filling the container with the reducing agent and the phosphoric acid solution, and before reducing the phosphoric acid, granular filler is filled around the reducing agent and the phosphoric acid solution filled inside the container.

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

Images