Method and system for separating and recovering phosphorus and iron in ferrophosphorus waste residues

Abstract

The invention discloses a method and system for separating and recycling phosphorus and iron in ferrophosphorus waste residues, and relates to the technical field of solid waste utilization. The method comprises the following steps: crushing the ferrophosphorus waste residue, and heating and melting in an inert environment; the molten ferrophosphorus waste residues are sprayed into a reaction furnace in a blowing mode, the inert atmosphere is kept in the reaction furnace, and meanwhile water is introduced into the reaction furnace; the temperature of the reaction furnace is increased to 400-1000 DEG C, heat preservation is conducted for 10-60 min, the ferrophosphorus waste residues react with water, and hydrogen phosphide gas and iron oxide are obtained; and introducing the obtained phosphine gas into a collection device for collection, and collecting the obtained iron oxide from the bottom of the reaction furnace. The method disclosed by the invention has the advantages of simple process flow, small wastewater generation amount, high phosphorus element recovery rate and high phosphine purity.

Description

Technical Field

[0001] The invention relates to the technical field of solid waste utilization, and in particular to a method and system for separating and recovering phosphorus and iron in ferrophosphorus waste slag. Background Art

[0002] Ferrophosphorus slag is a by-product of yellow phosphorus production. The raw material source is wide and the price is cheap. For every ton of yellow phosphorus produced, the by-product ferrophosphorus slag is 100-200 kg. With the development of the phosphorus production industry, a large amount of ferrophosphorus slag is produced and needs to be treated. The phosphorus content in ferrophosphorus slag is 18-28%, the iron content is 64-72%, and the rest contains a small amount of silicon, manganese, calcium, aluminum, magnesium, vanadium, etc. At present, ferrophosphorus slag is mostly used as waste slag or randomly piled up, and the value of ferrophosphorus slag has not been fully utilized; at the same time, with the increasing depletion of phosphate resources, it has become a top priority to improve the high-value utilization of ferrophosphorus slag.

[0003] The following process is used in the related art to recover phosphorus and iron from ferrophosphorus slag: the ferrophosphorus slag is mixed with sodium hydroxide, and ferric oxide is obtained after roasting, water immersion, solid-liquid separation, filter cake washing, and drying; the filtrate is concentrated, crystallized, and dried to obtain sodium phosphate. This process for recovering phosphorus and iron from ferrophosphorus slag requires multiple steps such as roasting, water immersion, solid-liquid separation, washing, drying, concentration, and crystallization. Not only are the steps cumbersome, but it also produces a large amount of heavy metals or acidic wastewater, and the treatment cost is high; in the process of recovering phosphorus and iron from ferrophosphorus slag in the related art, the purity of phosphate and iron oxide is difficult to meet the high purity requirements in the battery field.

[0004] It can be seen that in order to improve the effective utilization rate of lithium iron phosphate battery waste or ferrophosphorus slag, comprehensive recovery of phosphorus and iron elements in lithium iron phosphate battery waste or ferrophosphorus slag and use them to produce high value-added products has become a current research hotspot. Therefore, improving the process of recycling lithium iron phosphate battery waste or ferrophosphorus slag to improve its quality has become a technical problem that needs to be solved urgently by those skilled in the art. Summary of the invention

[0005] The invention discloses a method and system for separating and recovering phosphorus and iron in ferrophosphorus waste slag, so as to solve the technical problems that the process of recovering phosphorus and iron in ferrophosphorus waste slag in the related art has complicated steps, generates a large amount of waste water, and the product purity is difficult to meet the requirements of the battery field.

[0006] In order to solve the above problems, the present invention adopts the following technical solutions: The first aspect of the present invention discloses a method for separating and recovering phosphorus and iron in ferrophosphorus waste slag.

[0007] The method for separating and recovering phosphorus and iron in ferrophosphorus waste slag of the present invention comprises the following steps: After the ferrophosphorus waste slag is crushed, it is heated and melted in an inert environment; The molten ferrophosphorus slag is sprayed into the reaction furnace in a spraying manner, and an inert atmosphere is maintained in the reaction furnace while water is introduced into the reaction furnace. The reaction furnace is heated to 400 - 1000 °C and kept warm for 10 - 60 min. The ferrophosphorus slag reacts with water to obtain phosphine gas and iron oxide. The obtained phosphine gas is introduced into a collection device for collection, and the obtained iron oxide is collected from the bottom of the reaction furnace.

[0008] According to an optional embodiment, the reaction furnace is heated to 600 - 900 °C and kept warm for 20 - 40 min. And / or, the water introduced into the reaction furnace is steam. And / or, the steam is sprayed into the reaction furnace in a spraying manner, the pressure of the sprayed steam is 1 - 3 MPa, and the steam is atomized. And / or, the amount of steam introduced into the reaction furnace is 1 - 1.5 times the theoretical amount.

[0009] According to an optional embodiment, the molten ferrophosphorus slag is sprayed into the reaction furnace by means of atomizing nozzle spraying. The particle size of the ferrophosphorus slag ejected from the atomizing nozzle is 25 - 100 μm; and / or, an inert gas is used as the carrier gas, and the spraying pressure is 0.6 - 0.7 MPa.

[0010] According to an optional embodiment, when the molten ferrophosphorus slag is sprayed into the reaction furnace, the material is sprayed downward from the upper part of the reaction furnace, and steam is introduced upward from the bottom of the reaction furnace.

[0011] According to an optional embodiment, the atomizing nozzle is fixed on the wall of the reaction furnace, and an angle of 30° - 60° is formed between the spraying direction of the atomizing nozzle and the inner wall of the reaction furnace.

[0012] According to an optional embodiment, the composition of the ferrophosphorus slag includes one or more of FeP, Fe₂P, and Fe₃P. And / or, the ferrophosphorus slag is crushed to 300 - 500 meshes.

[0013] According to an optional embodiment, the method of heating and melting the ferrophosphorus slag is one or more of induction heating, microwave heating, fuel combustion heating, arc heating, plasma heating, and roasting heating.

[0014] According to an optional embodiment, the phosphine generated in the reaction furnace is collected by the following method: A cyclone separator is used to remove the particles and / or dust entrained in the phosphine gas generated in the reaction furnace. The phosphine gas after removing slag is sequentially introduced into a primary absorption tower and a secondary absorption tower, and NaOH solution and / or NaClO solution is used as the absorbent in the primary absorption tower and the secondary absorption tower.

[0015] The second aspect of the present invention provides a system for separating and recovering phosphorus and iron from phosphorus-iron waste slag.

[0016] The system for separating and recovering phosphorus and iron from phosphorus-iron waste slag of the present invention is used to implement the method for separating and recovering phosphorus and iron from phosphorus-iron waste slag described in any one of the technical solutions of the present invention. The system includes: A smelting furnace, which is used to heat and melt the crushed phosphorus-iron waste slag; A reaction furnace, a spray gun is provided between the reaction furnace and the smelting furnace. The spray gun is used to spray the heated and melted phosphorus-iron waste slag into the reaction furnace, and the reaction furnace is used to react the phosphorus-iron waste slag with water to obtain phosphine gas and iron oxide; A collection device, which is communicated with the reaction furnace, and the collection device is used to collect phosphine gas.

[0017] According to an optional embodiment, the collection device includes: A cyclone separator, which is arranged at the outlet of the reaction furnace, and the cyclone separator is used to separate the particles and / or dust entrained in the phosphine gas; A primary absorption tower, which is communicated with the gas outlet of the reaction furnace, and the primary absorption tower is used to preliminarily absorb the phosphine gas; A secondary absorption tower, which is connected in series with the primary absorption tower, and the secondary absorption tower is used to perform secondary absorption on the phosphine gas.

[0018] The technical solution adopted by the present invention can achieve the following beneficial effects: The method for separating and recovering phosphorus and iron from phosphorus-iron waste slag of the present invention only requires steps of melting, spraying, reacting and collecting. Compared with the related technology that uses a wet process to recover iron and phosphorus from phosphorus-iron waste slag, the present invention uses a pyrometallurgical process to separate and recover phosphorus and iron from phosphorus-iron waste slag, which has the advantage of a simple process flow, can greatly reduce the generation amount of wastewater, and thus can greatly reduce the wastewater treatment cost; on the other hand, by adopting the method of spray feeding, the phosphorus in the phosphorus-iron waste slag can be fully contacted with water to generate phosphine gas, which is beneficial to improving the recovery rate of phosphorus; at the same time, the phosphine generated by the combination of phosphorus and water overflows in the form of steam, and the phosphine overflowing in the form of steam has high purity, and the phosphate prepared therefrom can meet the requirements of the battery field for the purity of raw materials.

[0019] That is, the method for separating and recovering phosphorus and iron from phosphorus-iron waste slag of the present invention adopts the above-mentioned solution, solving the technical problems in the related art that the process for recovering phosphorus and iron from phosphorus-iron slag is cumbersome, generates a large amount of wastewater, and the product purity is difficult to meet the requirements of the battery field. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0021] Figure 1 It is a flowchart of the method for separating and recovering phosphorus and iron from phosphorus-iron waste slag of the present application.

[0022] Figure 2 It is a schematic diagram of the spraying direction and the water vapor inlet direction in the embodiment of the present application; Figure 3 It is a device diagram for separating and recovering phosphorus and iron from phosphorus-iron waste slag of the present application.

[0023] In the figure: 100, reaction furnace; 200, smelting furnace; 300, spray gun; 400, induced draft fan; 500, collection device. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] To make the objectives, technical solutions, and advantages of the present invention clearer, the following will describe the technical solutions of the present invention in detail. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope protected by the present invention.

[0025] The terms "first", "second", etc. in the description and claims of the present application are used to distinguish similar objects, rather than to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present application can be implemented in an order other than those illustrated or described herein, and the objects distinguished by "first", "second", etc. are generally of the same type, and do not limit the number of objects. For example, the first object can be one or multiple. In addition, "and / or" in the description and claims means at least one of the connected objects, and the character " / " generally indicates an "or" relationship between the associated objects before and after.

[0026] In the related art, the wet process is adopted to recover phosphorus and iron from phosphorus iron slag. The steps are cumbersome, and a large amount of wastewater will be generated, and the wastewater treatment cost is relatively high. In addition, for the process of recovering phosphorus and iron from phosphorus iron slag, the recovery rate and purity of iron and phosphorus elements are greatly affected by impurities, and the obtained products are difficult to meet the high-purity requirements in the battery field. The present application adopts a pyrometallurgical process to recover phosphorus and iron from phosphorus iron slag, which can avoid the above problems. Further, the present invention adopts a blowing feeding method, which is beneficial to improving the recovery rate of phosphine. At the same time, phosphine overflows in the form of steam, and the phosphine overflowing in the form of steam has high purity, and the phosphate prepared therefrom can meet the requirements of the battery field for the purity of raw materials.

[0027] The following will Figures 1 to 3 be described in detail with reference to the accompanying drawings, through specific embodiments and their application scenarios, the method and system for separating and recovering phosphorus and iron from phosphorus iron waste residue provided by the present application.

[0028] Figure 1 FIG. shows a flowchart of the method for separating and recovering phosphorus and iron from phosphorus iron waste residue of the present application. As Figure 1 shown, the method for separating and recovering phosphorus and iron from phosphorus iron waste residue of the present application includes the following steps: Step 100: After crushing the phosphorus iron waste residue, it is heated and melted in an inert environment.

[0029] In some embodiments, the phosphorus iron waste residue is the phosphorus iron slag generated in the industrial production process. Exemplarily, the main components of the phosphorus iron slag are one or more of FeP, Fe2P, and Fe3P, and the phosphorus element in the phosphorus iron slag is 10-30%, and the iron element is 30-70%. The present application does not limit the main components and sources of the phosphorus iron slag.

[0030] In some embodiments, the phosphorus iron waste residue is crushed to 300-500 meshes. After the phosphorus iron waste residue is crushed to 300-500 meshes, it is easy to heat and melt the phosphorus iron waste residue, which is beneficial to reducing energy consumption. Exemplarily, the phosphorus iron waste residue can be crushed to 300-500 meshes by means of a jet mill. Compared with ball milling, the jet mill method can not only crush the phosphorus iron waste residue to a smaller particle size, but more importantly, this method can avoid introducing metal impurities, which is of great significance for obtaining high-quality products.

[0031] In some embodiments, the method of heating and melting the phosphorus iron waste residue is one or more of induction heating, microwave heating, fuel combustion heating, arc heating, plasma heating, and roasting heating. Exemplarily, the crushed phosphorus iron waste residue is heated to 1000-1400 °C to be in a molten state. An inert environment is maintained during the heating process, and the inert environment is, for example, a nitrogen atmosphere, which can avoid the loss of phosphorus elements in the phosphorus iron slag.

[0032] Step 200: Spray the molten ferrophosphorus slag into the reaction furnace in a spraying manner. An inert atmosphere is maintained in the reaction furnace, and water is introduced into the reaction furnace at the same time.

[0033] Furthermore, heat the reaction furnace to 400 - 1000 °C and keep it warm for 10 - 60 min. The ferrophosphorus slag reacts with water to obtain phosphine gas and iron oxide.

[0034] Taking the main component of ferrophosphorus slag as FeP as an example, the following reaction occurs between FeP and H₂O in a high-temperature molten state: 2FeP + 6H₂O = 2FeO + 2PH₃↑ + 3H₂↑ Maintaining an inert atmosphere in the reaction furnace is beneficial to improving the safety of the reaction. Exemplarily, inert gases such as nitrogen, argon, and helium can be introduced into the reaction furnace.

[0035] The iron oxide obtained from the reaction can be extracted by acid leaching.

[0036] Step 300: Introduce the obtained phosphine gas into a collection device for collection, and collect the obtained iron oxide from the bottom of the reaction furnace.

[0037] Exemplarily, the obtained phosphine gas can be collected by oxidation to convert the phosphine gas into a salt.

[0038] The method for separating and recovering phosphorus and iron from ferrophosphorus slag in this application only requires steps of melting, spraying, reacting, and collecting. Compared with the related technology that uses a wet process to recover iron and phosphorus from ferrophosphorus slag, this application uses a pyrometallurgical process to separate and recover phosphorus and iron from ferrophosphorus slag, which has the advantage of a simple process flow, can greatly reduce the generation of wastewater, and thus can greatly reduce the wastewater treatment cost. On the other hand, by using the spraying feeding method, the phosphorus in the ferrophosphorus slag can be fully contacted with water to generate phosphine gas, which is beneficial to improving the recovery rate of phosphorus. At the same time, the phosphine generated by the combination of phosphorus and water overflows in the form of steam, and the obtained phosphine has a high purity, and the phosphate prepared therefrom can meet the requirements of the battery field for the purity of raw materials.

[0039] That is, the method for separating and recovering phosphorus and iron from ferrophosphorus slag in this application adopts the above scheme to solve the technical problems existing in the process of recovering phosphorus and iron from ferrophosphorus slag in the related technology, such as cumbersome steps, generating a large amount of wastewater, and the product purity being difficult to meet the requirements of the battery field.

[0040] According to an alternative embodiment, the reaction furnace is heated to 600-900 °C and kept at this temperature for 20-40 min. Under low-temperature regulation, such as at 400-600 °C, the reaction rate is low, the phosphorus-iron waste residue does not react completely, and the amount of PH3 generated is small, resulting in a low phosphorus recovery rate. When the temperature is too high, PH3 may decompose, affecting the stability of the product and also causing a decrease in the phosphorus recovery rate. In the embodiments of the present application, the reaction furnace is heated to 600-900 °C and kept at this temperature for 20-40 min, which can balance the reaction rate and the stability of the product to obtain a high phosphorus recovery rate.

[0041] According to an alternative embodiment, the water introduced into the reaction furnace is water vapor. Exemplarily, the water is vaporized and then introduced into the reaction furnace. Preferably, the temperature of the water vapor can be kept consistent with the temperature inside the reaction furnace.

[0042] The inventors found in their research that if liquid water is introduced into the reaction furnace, during the endothermic vaporization process of the liquid water, the local temperature inside the furnace will decrease, especially in the area where the liquid water enters, there is a potential risk of inhibiting the continuous progress of the reaction. In addition, if the liquid water fails to be completely vaporized, it may also locally accumulate and react with iron oxides to form by-products such as hydroxyapatite, resulting in the retention of phosphorus in a non-gaseous form and reducing the yield of phosphine. In the method for separating and recovering phosphorus and iron from phosphorus-iron waste residue in the present application, the water introduced into the reaction furnace is water vapor, which can form a uniform and stable thermal environment inside the furnace, effectively avoiding the decrease in the local temperature inside the furnace and the generation of by-products, thereby contributing to improving the yield and purity of phosphine.

[0043] According to an alternative embodiment, the amount of water vapor introduced into the reaction furnace is 1-1.5 times the theoretical amount. In the method for separating and recovering phosphorus and iron from phosphorus-iron waste residue in the present application, the amount of water vapor is 1-1.5 times the theoretical amount. On the one hand, it can ensure the full reaction of phosphorus in the phosphorus-iron waste residue and ensure the conversion rate of phosphorus. On the other hand, it can also avoid excessive water volume, resulting in an increase in system energy consumption or an increase in equipment load.

[0044] According to an alternative embodiment, the molten phosphorus-iron waste residue is sprayed into the reaction furnace by means of an atomizing nozzle. Preferably, the particle size of the phosphorus-iron waste residue ejected from the atomizing nozzle is 25-100 μm. Without limitation, the particle size of the phosphorus-iron waste residue ejected from the atomizing nozzle can also be smaller. By selecting atomizing nozzles with different pore sizes, phosphorus-iron waste residues with different particle sizes can be ejected.

[0045] Preferably, an inert gas is used as the carrier gas, and the spraying pressure is 0.6-0.7 MPa. Using an inert gas as the carrier gas is beneficial to ensuring an inert atmosphere inside the reaction furnace to improve the safety of the reaction.

[0046] The method for separating and recovering phosphorus and iron from phosphorus-iron waste slag in this application. After heating the phosphorus-iron waste slag to melt, the mineral lattice is destroyed, and the phosphorus originally dissolved in the oxide lattice or encapsulated in silicate is released as free phosphorus, which is beneficial for subsequent contact between phosphorus and water vapor to produce phosphine. Further, crushing the phosphorus-iron waste slag before heating and melting can reduce energy consumption and shorten the melting time.

[0047] However, the inventors found in the research that it is difficult to completely release the encapsulated phosphorus by heating and melting. Generally, melting can reduce the encapsulation rate of phosphorus from 30% - 50% to about 5% (part of the phosphorus is encapsulated in unmelted particles with higher melting temperatures). Since some of the encapsulated phosphorus is always difficult to release, it leads to a bottleneck in the phosphorus recovery rate. In this application, the phosphorus-iron waste slag is sprayed into the reaction furnace by means of spraying. On the one hand, spraying can disperse the melt into fine droplets or particles, increasing the specific surface area, making the encapsulated phosphorus more easily exposed on the surface, and improving the reaction rate and the yield of phosphine; on the other hand, the shear force caused by high-speed spraying can break the mineral phase boundary inside the slag body, which is beneficial for the release of the encapsulated phosphorus, thereby further improving the reaction rate and the yield of phosphine. Further, in this application, the phosphorus-iron waste slag is sprayed into the reaction furnace by means of spraying, and the fluidity of spraying can also prevent the problem that phosphorus is re-coated in iron oxides to form a eutectic melt when the melt is in a static state, thereby ensuring the yield of phosphine.

[0048] According to an optional embodiment, water vapor is sprayed into the reaction furnace by means of injection, and the pressure of the injected water vapor is 1 - 3 MPa. The rising water vapor and the falling phosphorus-iron waste slag form a countercurrent contact, which can significantly enhance the gas-solid two-phase mass transfer efficiency; at the same time, it can also expand the contact area between the two, and further improve the yield of phosphine.

[0049] According to an optional embodiment, when the melted phosphorus-iron waste slag is sprayed into the reaction furnace, the material is sprayed downward from the upper part of the reaction furnace, and water vapor is introduced upward from the bottom of the reaction furnace. This feeding method can make the water vapor continuously collide with the falling melted material during the rising process, thereby improving the utilization rate of water vapor; on the other hand, the melted phosphorus-iron waste slag and water vapor form a convection, which can extend the residence time of the melted phosphorus-iron waste slag in the furnace, so that the melted phosphorus-iron waste slag and water vapor can react more fully.

[0050] According to an optional embodiment, the atomizing nozzle is fixed on the wall of the reaction furnace, and an angle of 30° - 60° is formed between the spraying direction of the atomizing nozzle and the inner wall of the reaction furnace. Preferably, the atomizing nozzle is fixed on the side wall or the top wall of the reaction furnace. Exemplarily, an angle of 30° is formed between the spraying direction and the inner wall of the reaction furnace, or an angle of 45° is formed between the spraying direction and the inner wall of the reaction furnace, or an angle of 60° is formed between the spraying direction and the inner wall of the reaction furnace. Figure 2A schematic diagram showing the spraying direction is presented.

[0051] In the method for separating and recovering phosphorus and iron from phosphorus-iron waste residue in this application, the molten phosphorus-iron waste residue is sprayed into the reaction furnace in an inclined downward manner. Compared with the vertically downward spraying direction, when using the inclined downward spraying method, the molten phosphorus-iron waste residue can form a spiral movement trajectory with the rising water vapor, triggering forced turbulence, which can improve the uniformity of the mixing of the molten phosphorus-iron waste residue and water vapor, so that the reaction between the molten phosphorus-iron waste residue and water vapor can be more sufficient; moreover, the centrifugal acceleration generated by the spiral movement can also reduce the dust, iron oxide particles, etc. entrained in the PH3 vapor, which can further improve the purity of the PH3 vapor. On the other hand, when the molten phosphorus-iron waste residue is sprayed into the reaction furnace in an inclined downward manner, the rising water vapor can generate a shear force on the falling phosphorus-iron waste residue, prompting large droplets or large particles of the material to split into smaller particle sizes, which can further improve the reaction rate and the yield of PH3.

[0052] According to an optional embodiment, phosphine generated in the reaction furnace is collected in the following manner: Step 310: Use a cyclone separator to remove the particles and / or dust entrained in the phosphine gas generated in the reaction furnace. By removing the particles and / or dust entrained in the phosphine gas, it is not only beneficial to improve the purity of phosphine, but also can avoid blocking the absorption tower when the subsequent phosphine gas enters the absorption tower.

[0053] Step 320: Sequentially introduce the phosphine gas after slag removal into a primary absorption tower and a secondary absorption tower. The primary absorption tower and the secondary absorption tower use NaOH solution and / or NaClO solution as absorbents.

[0054] Exemplarily, the primary absorption tower uses NaOH solution as the absorbent, and the secondary absorption tower uses NaClO solution as the absorbent. The concentrations of the NaOH solution and the NaClO solution can be determined based on the actual situation. The primary absorption tower and the secondary absorption tower can be packed towers or spray towers.

[0055] Exemplarily, in the primary absorption tower, the concentration of the NaOH solution is 2 - 4 mol / L, the liquid-gas ratio is 10 - 15 L / m 3 , the temperature is 40 - 60 °C to prevent the crystallization and blockage of NaH2PO2. The inside of the primary absorption tower is an inert atmosphere, and a slightly positive pressure of 0.5 - 2 Kpa is maintained inside the primary absorption tower to prevent air infiltration.

[0056] Exemplarily, in the secondary absorption tower, the concentration of the NaClO solution is 0.1 - 0.5%. Through the NaClO solution, the residual phosphine gas can be further absorbed.

[0057] Without being limited thereto, it is also possible to use only a primary absorption tower to absorb phosphine gas, and the absorption tower uses a NaOH solution or a NaClO solution as an absorbent.

[0058] The method for separating and recovering phosphorus and iron from phosphorus-iron waste slag in the present application uses a primary absorption tower to absorb most of the phosphine gas, and then uses a secondary absorption tower to absorb a small amount of residual phosphine gas, which can ensure the absorption efficiency of phosphine gas.

[0059] The system for separating and recovering phosphorus and iron from phosphorus-iron waste slag in the present application is used to implement the method for separating and recovering phosphorus and iron from phosphorus-iron waste slag in any one of the technical solutions in the present application.

[0060] The system for separating and recovering phosphorus and iron from phosphorus-iron waste slag in the present application includes a smelting furnace 200, a reaction furnace 100 and a collection device 500, as Figure 3 shown. Among them, the smelting furnace 200 is used to heat and melt the crushed phosphorus-iron waste slag. Exemplarily, the smelting furnace 200 is a muffle furnace or an intermediate frequency furnace, a high frequency furnace, etc. in the prior art. A spray gun 300 is provided between the reaction furnace 100 and the smelting furnace. The spray gun 300 is used to spray the heated and melted phosphorus-iron waste slag into the reaction furnace 100, and the reaction furnace 100 is used to react the phosphorus-iron waste slag with water to obtain phosphine gas and iron oxide. The phosphine gas is introduced into the absorption device 500 through a blower 400. Exemplarily, the reaction furnace 100 can be an atmospheric high-temperature reaction furnace in the prior art, such as an intermediate frequency furnace, a high frequency furnace, etc. The collection device 500 is communicated with the reaction furnace, and the collection device 500 is used to collect phosphine gas. Exemplarily, the collection device 500 can be an absorption tower or a packed tower.

[0061] According to an optional embodiment, the collection device includes a cyclone separator, a primary absorption tower and a secondary absorption tower. Among them, the cyclone separator is arranged at the outlet of the reaction furnace, and the cyclone separator is used to separate the particles and / or dust entrained in the phosphine gas. The primary absorption tower is communicated with the gas outlet of the reaction furnace, and the primary absorption tower is used to preliminarily absorb the phosphine gas. The secondary absorption tower is connected in series with the primary absorption tower, and the secondary absorption tower is used to perform secondary absorption on the phosphine gas. For the introduction of the cyclone separator, the primary absorption tower and the secondary absorption tower, please refer to the foregoing part, and will not be elaborated here.

[0062] The reduced electric furnace or the reduced slag produced by treating high-phosphorus iron ore is all phosphorus-iron ore slag. The main component of phosphorus-iron ore slag is iron phosphide (FeP), and there are also about 10% of metal impurities such as silicon dioxide, calcium oxide, aluminum, manganese, chromium, nickel, etc. Its iron content is 30%-60%, and its phosphorus content is 5%-20%, and it contains some other components. Hereinafter, the phosphorus-iron ore slag produced by treating high-phosphorus iron ore is used as the raw material.

[0063] Example 1 The method for separating and recovering phosphorus and iron from phosphorus-iron waste slag in this embodiment includes the following steps: Step 100: Using phosphorus-iron ore slag as raw material, after crushing, it is sieved through a 300-mesh sieve. The selected phosphorus-iron ore slag powder is put into an intermediate-frequency furnace. First, nitrogen is purged to remove oxygen, and then under a nitrogen atmosphere, it is heated by induction to 1200 °C to raise the temperature of the phosphorus-iron ore slag to a molten state.

[0064] Maintain a nitrogen atmosphere in the reaction furnace, and the molten phosphorus-iron ore slag is sprayed obliquely downward into the reaction furnace (for example, if the phosphorus-iron ore slag sprayed into the reaction furnace contains 10 mol of iron phosphide). The spraying direction forms an angle of 60° with the inner wall of the reaction furnace, and the spraying particle size is 25 μm. At the same time, steam is sprayed into the reaction furnace, the spraying pressure is 1 MPa, and the amount of steam used is the theoretical amount required for the complete reaction of iron phosphide.

[0065] Step 200: Raise the temperature of the reaction furnace to 600 °C and keep it warm for 40 min. The phosphorus-iron ore slag reacts with steam to generate PH3 vapor and iron oxide.

[0066] Step 300: After the reaction ends, the PH3 vapor discharged from the reaction furnace is passed through an absorption tower in sequence. In the absorption tower, a 4 mol / L NaOH solution is used as the absorbent.

[0067] Collect the iron oxide from the bottom of the reaction furnace, and the iron oxide is extracted by acid leaching.

[0068] After detection, the recovery rate of phosphorus in this embodiment is 96.3%, the purity of NaH2PO2 is 99.7%, the recovery rate of iron is 99.5%, and the purity of iron oxide is 74.9%.

[0069] Example 2 The method for separating and recovering phosphorus and iron from phosphorus-iron waste slag in this embodiment includes the following steps: Step 100: Using phosphorus-iron ore slag as raw material, after crushing, it is sieved through a 300-mesh sieve. The selected phosphorus-iron ore slag powder is put into an intermediate-frequency furnace. First, nitrogen is purged to remove oxygen, and then under a nitrogen atmosphere, it is heated by induction to 1200 °C to raise the temperature of the phosphorus-iron ore slag to a molten state.

[0070] Maintain a nitrogen atmosphere in the reaction furnace, and the molten phosphorus-iron ore slag is sprayed obliquely downward into the reaction furnace. The spraying direction forms an angle of 60° with the inner wall of the reaction furnace, and the spraying particle size is 25 μm. At the same time, steam is sprayed into the reaction furnace, the spraying pressure is 1 MPa, and the amount of steam used is the theoretical amount required for the complete reaction of iron phosphide.

[0071] Step 200: Raise the temperature of the reaction furnace to 1000 °C and keep it warm for 10 min. The phosphorus-iron ore slag reacts with steam to generate PH3 vapor and iron oxide.

[0072] Step 300: After the reaction is completed, the PH3 vapor discharged from the reaction furnace is successively passed through an absorption tower, and a 4 mol / L NaOH solution is used as the absorption liquid in the absorption tower.

[0073] Collect iron oxides from the bottom of the reaction furnace, and the iron oxides are extracted by acid leaching.

[0074] After detection, the phosphorus recovery rate in this example is 92.6%, the purity of NaH2PO2 is 99.2%, the iron recovery rate is 99.3%, and the purity of iron(III) oxide is 72.8%.

[0075] Example 3 The method for separating and recovering phosphorus and iron from phosphorus-iron waste slag in this example includes the following steps: Step 100: Using phosphorus iron ore slag as raw material, after crushing, pass through a 300-mesh sieve. Put the selected phosphorus iron ore slag powder into an intermediate frequency furnace, first purge nitrogen to remove oxygen, and then under a nitrogen atmosphere, use induction heating to 1200 °C to heat the phosphorus iron ore slag to melt it into a liquid state.

[0076] Maintain a nitrogen atmosphere in the reaction furnace, tilt and spray the molten phosphorus iron ore slag downward into the reaction furnace. The spraying direction forms an angle of 60° with the inner wall of the reaction furnace, and the spraying particle size is 25 μm. At the same time, spray steam into the reaction furnace, the spraying pressure is 1 MPa, and the amount of steam used is the theoretical amount required for the complete reaction of iron phosphide.

[0077] Step 200: Heat the reaction furnace to 900 °C and keep it warm for 40 min. The phosphorus iron ore slag reacts with steam to generate PH3 vapor and iron oxides.

[0078] Step 300: After the reaction is completed, the PH3 vapor discharged from the reaction furnace is successively passed through an absorption tower, and a 4 mol / L NaOH solution is used as the absorption liquid in the absorption tower.

[0079] Collect iron oxides from the bottom of the reaction furnace, and the iron oxides are extracted by acid leaching.

[0080] After detection, the phosphorus recovery rate in this example is 95.7%, the purity of NaH2PO2 is 99.5%, the iron recovery rate is 99.4%, and the purity of iron(III) oxide is 73.9%.

[0081] Example 4 The method for separating and recovering phosphorus and iron from phosphorus-iron waste slag in this example includes the following steps: Step 100: Using phosphorus iron ore slag as raw material, after crushing, pass through a 300-mesh sieve. Put the selected phosphorus iron ore slag powder into an intermediate frequency furnace, first purge nitrogen to remove oxygen, and then under a nitrogen atmosphere, use induction heating to 1200 °C to heat the phosphorus iron ore slag to melt it into a liquid state.

[0082] Maintain a nitrogen atmosphere inside the reactor, tilt and spray the molten iron phosphate slag downward into the reactor, forming an angle of 60° between the spraying direction and the inner wall of the reactor, with a spraying particle size of 25 μm. At the same time, spray steam into the reactor, with a spraying pressure of 1 MPa, and the amount of steam used is the theoretical amount required for the complete reaction of iron phosphide.

[0083] Step 200: Heat the reactor to 400 °C and keep it at this temperature for 60 min. The iron phosphate slag reacts with steam to generate PH3 vapor and iron oxide.

[0084] Step 300: After the reaction ends, pass the PH3 vapor discharged from the reactor through an absorption tower in sequence. Use a 4 mol / L NaOH solution as the absorbent in the absorption tower.

[0085] Collect the iron oxide from the bottom of the reactor, and extract the iron oxide by acid leaching.

[0086] After testing, the phosphorus recovery rate in this example is 93.4%, the purity of NaH2PO2 is 99.6%, the iron recovery rate is 99.5%, and the purity of iron(III) oxide is 71.5%.

[0087] Example 5 The method for separating and recovering phosphorus and iron from phosphorus-iron waste slag in this example includes the following steps: Step 100: Use iron phosphate slag as the raw material, crush it and pass it through a 300-mesh sieve. Put the selected iron phosphate slag powder into an intermediate-frequency furnace, first purge nitrogen to remove oxygen, and then under a nitrogen atmosphere, use induction heating to 1200 °C to heat and melt the iron phosphate slag into a liquid state.

[0088] Maintain a nitrogen atmosphere inside the reactor, tilt and spray the molten iron phosphate slag downward into the reactor, forming an angle of 60° between the spraying direction and the inner wall of the reactor, with a spraying particle size of 25 μm. At the same time, spray steam into the reactor, with a spraying pressure of 1 MPa, and the amount of steam used is 1.5 times the theoretical amount required for the complete reaction of iron phosphide.

[0089] Step 200: Heat the reactor to 600 °C and keep it at this temperature for 40 min. The iron phosphate slag reacts with steam to generate PH3 vapor and iron oxide.

[0090] Step 300: After the reaction ends, pass the PH3 vapor discharged from the reactor through an absorption tower in sequence. Use a 4 mol / L NaOH solution as the absorbent in the absorption tower.

[0091] Collect the iron oxide from the bottom of the reactor, and extract the iron oxide by acid leaching.

[0092] After detection, the phosphorus recovery rate in this embodiment is 96.7%, the purity of NaH2PO2 is 99.6%, the iron recovery rate is 99.3%, and the purity of iron(III) oxide is 68.6%.

[0093] Example 6 The method for separating and recovering phosphorus and iron from phosphorus-iron waste slag in this embodiment includes the following steps: Step 100: Using phosphorus iron ore slag as raw material, after crushing, pass through a 300-mesh sieve. Put the screened phosphorus iron ore slag powder into an intermediate frequency furnace, first purge nitrogen to remove oxygen, and then under a nitrogen atmosphere, use induction heating to 1200 °C to heat the phosphorus iron ore slag to melt it into a liquid state.

[0094] Maintain a nitrogen atmosphere in the reaction furnace, tilt and spray the molten phosphorus iron ore slag downward into the reaction furnace. The spraying direction forms an angle of 60° with the inner wall of the reaction furnace, and the spraying particle size is 25 μm. At the same time, spray water vapor into the reaction furnace, the spraying pressure is 1 MPa, and the dosage of water vapor is 1.3 times the theoretical dosage required for the complete reaction of iron phosphide.

[0095] Step 200: Heat the reaction furnace to 600 °C and keep it warm for 40 min. The phosphorus iron ore slag reacts with water vapor to generate PH3 vapor and iron oxides.

[0096] After the reaction ends, pass the PH3 vapor discharged from the reaction furnace through an absorption tower in sequence. In the absorption tower, 4 mol / L NaOH solution is used as the absorbent.

[0097] Collect iron oxides from the bottom of the reaction furnace, and extract the iron oxides by acid leaching.

[0098] After detection, the phosphorus recovery rate in this embodiment is 96.5%, the purity of NaH2PO2 is 99.5%, the iron recovery rate is 99.4%, and the purity of iron(III) oxide is 69.2%.

[0099] Example 7 The method for separating and recovering phosphorus and iron from phosphorus-iron waste slag in this embodiment includes the following steps: Step 100: Using phosphorus iron ore slag as raw material, after crushing, pass through a 300-mesh sieve. Put the screened phosphorus iron ore slag powder into an intermediate frequency furnace, first purge nitrogen to remove oxygen, and then under a nitrogen atmosphere, use induction heating to 1200 °C to heat the phosphorus iron ore slag to melt it into a liquid state.

[0100] Maintain a nitrogen atmosphere in the reaction furnace, tilt and spray the molten phosphorus iron ore slag downward into the reaction furnace. The spraying direction forms an angle of 60° with the inner wall of the reaction furnace, and the spraying particle size is 25 μm. At the same time, spray liquid water into the reaction furnace, the spraying pressure is 1 MPa, and the dosage of liquid water is the theoretical dosage required for the complete reaction of iron phosphide.

[0101] Step 200: Heat the reaction furnace to 600 °C and keep it at this temperature for 40 min. The phosphorus iron slag reacts with water vapor to produce PH3 vapor and iron oxide.

[0102] Step 300: After the reaction is completed, pass the PH3 vapor discharged from the reaction furnace through an absorption tower in sequence. In the absorption tower, a 4 mol / L NaOH solution is used as the absorbent.

[0103] Collect the iron oxide from the bottom of the reaction furnace, and extract the iron oxide by acid leaching.

[0104] After testing, the phosphorus recovery rate in this example is 92.7%, the purity of NaH2PO2 is 99.1%, the iron recovery rate is 99.3%, and the purity of iron(III) oxide is 68.5%.

[0105] Comparative Example 1 The method for separating and recovering phosphorus and iron from phosphorus iron waste slag in this example includes the following steps: Step 100: Using phosphorus iron slag as raw material, crush it and pass through a 300-mesh sieve. Put the screened phosphorus iron slag powder into an intermediate frequency furnace, first purge nitrogen to remove oxygen, and then under a nitrogen atmosphere, use induction heating to 1200 °C to heat and melt the phosphorus iron slag into a liquid state.

[0106] Keep a nitrogen atmosphere in the reaction furnace, tilt and spray the molten phosphorus iron slag downward into the reaction furnace. The spraying direction forms an angle of 60° with the inner wall of the reaction furnace, the spraying particle size is 25 μm, and at the same time, spray water vapor into the reaction furnace. The spraying pressure is 1 MPa, and the amount of water vapor used is 3 times the theoretical amount required for the complete reaction of iron phosphide.

[0107] Step 200: Heat the reaction furnace to 600 °C and keep it at this temperature for 40 min. The phosphorus iron slag reacts with water vapor to produce PH3 vapor and iron oxide.

[0108] Step 300: After the reaction is completed, pass the PH3 vapor discharged from the reaction furnace through an absorption tower in sequence. In the absorption tower, a 4 mol / L NaOH solution is used as the absorbent.

[0109] Collect the iron oxide from the bottom of the reaction furnace, and extract the iron oxide by acid leaching.

[0110] After testing, the phosphorus recovery rate in this example is 91.6%, the purity of NaH2PO2 is 99.2%, the iron recovery rate is 99.5%, and the purity of iron(III) oxide is 61.9%.

[0111] Comparative Example 2 The method for separating and recovering phosphorus and iron from phosphorus iron waste slag in this example includes the following steps: Step 100: Using phospho-iron slag as raw material, after crushing, sieve it through a 300-mesh sieve. Put the selected phospho-iron slag powder into an intermediate frequency furnace, first purge nitrogen to remove oxygen, and then under a nitrogen atmosphere, use induction heating to 1200 °C to heat and melt the phospho-iron slag to a liquid state.

[0112] Keep a nitrogen atmosphere in the reaction furnace, and vertically spray the molten phospho-iron slag downward from the top of the reaction furnace. The spray particle size is 25 μm. At the same time, spray steam into the reaction furnace. The spray pressure is 1 MPa, and the amount of steam used is the theoretical amount required for the complete reaction of iron phosphide.

[0113] Step 200: Heat the reaction furnace to 600 °C and keep it warm for 40 min. The phospho-iron slag reacts with steam to generate PH3 vapor and iron oxide.

[0114] After the reaction is completed, pass the PH3 vapor discharged from the reaction furnace through an absorption tower in sequence. Use a 4 mol / L NaOH solution in the absorption tower as the absorbent.

[0115] Collect iron oxide from the bottom of the reaction furnace, and extract the iron oxide by acid leaching.

[0116] After testing, in this example, the phosphorus recovery rate is 89.8%, the purity of NaH2PO2 is 99.3%, the iron recovery rate is 99.2%, and the purity of iron oxide is 59.7%.

[0117] In the above examples and comparative examples, an inductively coupled plasma mass spectrometry was used to detect the content of NaH2PO2, and the phosphorus recovery rate was calculated based on the ratio of the obtained phosphorus content to the phosphorus content in the phospho-iron slag.

[0118] The purity of NaH2PO2 was detected by detecting the phosphorus content in NaH2PO2.

[0119] The iron content obtained from the iron oxide was measured by the potassium dichromate titration method, and the iron recovery rate was calculated based on the ratio of the obtained iron content to the iron content in the phospho-iron slag.

[0120] The purity of the iron oxide was detected by atomic absorption spectrometry.

[0121] It should be noted that in this article, the term "including", "comprising" or any other variation thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or also includes elements inherent to this process, method, article or device. Without further limitations, an element defined by the statement "including one..." does not exclude the existence of additional identical elements in the process, method, article or device including that element.

[0122] In addition, it should be noted that the scope of the methods and apparatuses in the embodiments of the present application is not limited to performing functions in the order shown or discussed. It may also include performing functions in a substantially simultaneous manner or in a reverse order according to the functions involved. For example, the described methods may be performed in an order different from that described, and various steps may also be added, omitted, or combined. Additionally, the features described with reference to certain examples may be combined in other examples.

[0123] As described above, the above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, and all should be covered within the protection scope of the present invention.

Claims

1. A method for separating and recovering phosphorus and iron in ferrophosphorus waste slag, characterized in that: The steps include: After the ferrophosphorus waste slag is crushed, it is heated and melted in an inert environment; The molten ferrophosphorus waste slag is sprayed into a reaction furnace by a blowing method, an inert atmosphere is maintained in the reaction furnace, and water is introduced into the reaction furnace; The reaction furnace is heated to 400-1000° C. and kept warm for 10-60 minutes, and the ferrophosphorus waste slag reacts with water to obtain phosphine gas and iron oxide; The obtained phosphine gas is introduced into a collecting device for collection, and the obtained iron oxide is collected from the bottom of the reaction furnace.

2. The method for separating and recovering phosphorus and iron in ferrophosphorus waste slag according to claim 1, characterized in that: The reactor is heated to 600-900°C and kept at this temperature for 20-40 minutes; And / or, the water introduced into the reaction furnace is water vapor; And / or, water vapor is sprayed into the reaction furnace in a jet manner, the pressure of the sprayed water vapor is 1-3 MPa, and the water vapor is atomized; And / or, the amount of water vapor introduced into the reaction furnace is 1 to 1.5 times the theoretical amount.

3. The method for separating and recovering phosphorus and iron in ferrophosphorus waste slag according to claim 2, characterized in that: The molten ferrophosphorus waste slag is sprayed into the reaction furnace by an atomizing nozzle, and the particle size of the ferrophosphorus waste slag sprayed through the atomizing nozzle is 25-100 μm; and / or, an inert gas is used as a carrier gas, and the spraying pressure is 0.6-0.7 MPa.

4. The method for separating and recovering phosphorus and iron in ferrophosphorus waste slag according to claim 2, characterized in that: When the molten ferrophosphorus waste slag is sprayed into the reaction furnace, the material is sprayed downward from the top of the reaction furnace, and water vapor is introduced upward from the bottom of the reaction furnace.

5. The method for separating and recovering phosphorus and iron in ferrophosphorus waste slag according to claim 4, characterized in that: The atomizing nozzle is fixed on the wall surface of the reaction furnace, and the spraying direction of the atomizing nozzle forms an angle of 30° to 60° with the inner wall of the reaction furnace.

6. The method for separating and recovering phosphorus and iron in ferrophosphorus waste slag according to claim 1, characterized in that: The components of the ferrophosphorus waste slag include one or more of FeP, Fe2P, and Fe3P; And / or, the ferrophosphorus waste slag is crushed to 300-500 mesh.

7. The method for separating and recovering phosphorus and iron in ferrophosphorus waste slag according to claim 1, characterized in that: The method of heating and melting the ferrophosphorus waste slag is one or more of induction heating, microwave heating, fuel combustion heating, arc heating, plasma heating, and roasting heating.

8. The method for separating and recovering phosphorus and iron in ferrophosphorus waste slag according to claim 1, characterized in that: The phosphine generated in the reaction furnace is collected by the following method: Using a cyclone separator to remove particles and / or dust entrained in the phosphine gas generated in the reaction furnace; The phosphine gas after slag removal is introduced into a primary absorption tower and a secondary absorption tower in sequence, wherein the primary absorption tower and the secondary absorption tower use NaOH solution and / or NaClO solution as absorbent.

9. A system for separating and recovering phosphorus and iron from ferrophosphorus waste slag, characterized in that: The method for separating and recovering phosphorus and iron from ferrophosphorus waste slag according to any one of claims 1 to 8 comprises: A smelting furnace, wherein the smelting furnace is used to heat and melt the crushed ferrophosphorus waste slag; A reaction furnace, wherein a spray gun is provided between the reaction furnace and the smelting furnace, the spray gun is used to spray the heated and melted ferrophosphorus waste slag into the reaction furnace, and the reaction furnace is used to react the ferrophosphorus waste slag with water to obtain phosphine gas and iron oxide; A collecting device is communicated with the reaction furnace and is used to collect phosphine gas.

10. The system for separating and recovering phosphorus and iron in ferrophosphorus waste slag according to claim 9, characterized in that: The collecting device comprises: a cyclone separator, the cyclone separator being arranged at the outlet of the reaction furnace and being used for separating particles and / or dust entrained in the phosphine gas; a primary absorption tower, the primary absorption tower being in communication with the gas outlet of the reaction furnace and being used for preliminarily absorbing the phosphine gas; A secondary absorption tower is connected in series with the primary absorption tower, and the secondary absorption tower is used for secondary absorption of the phosphine gas.

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