Method for removing sulfur in high-purity ferrous sulfate by combining dry method and wet method

Abstract

The invention discloses a method for removing sulfur in high-purity ferrous sulfate by combining a dry method and a wet method, and relates to the technical field of preparation of high-purity iron products. The method comprises the following steps: dissolving ferrous sulfate in warm water to obtain a ferrous sulfate aqueous solution; alkali liquor is added into the ferrous sulfate aqueous solution, the pH of the ferrous sulfate aqueous solution is adjusted, and ferrous sulfate is converted into hydroxyl compound sediment of iron; adjusting the pH value of the iron hydroxyl compound precipitation solid-liquid mixture to 7-8, heating, aging, carrying out solid-liquid separation, washing and drying to obtain an iron hydroxyl compound; putting into a container, and deeply desulfurizing by one or more methods of high-temperature calcination, thermal shock, positive and negative pressure alternation and dynamic cold quenching; and washing, drying and reducing the deeply desulfurized product to obtain the low-sulfur iron powder. According to the method, wet desulfurization and dry desulfurization are combined, so that deep desulfurization of ferrous sulfate can be realized, the sulfur content in the obtained product is reduced to be less than 1ppm, and the limitation on impurity sulfur in the fields of catalysis, metallurgy, magnetic materials and the like is met.

Description

Technical Field

[0001] This invention relates to the field of high-purity iron product preparation technology, and in particular to a method for removing sulfur from high-purity ferrous sulfate using a combination of dry and wet methods. Background Technology

[0002] Solid wastes such as titanium dioxide slag, steel slag, battery black powder, and copper smelting slag contain a large amount of iron. Using iron-containing waste as raw material to recover iron and prepare iron products is an important way to achieve resource recycling and environmental governance. The iron-based products are widely used in catalysis, metallurgy, magnetic materials and other fields. Their purity directly determines the performance and application safety of downstream products.

[0003] Different application fields have different requirements for the types and contents of impurities. For example, in the field of hot processing, the presence of sulfur impurities is the root cause of the hot brittleness of high-purity iron powder. Sulfur reacts with iron to form low-melting-point FeS, which easily leads to grain boundary melting and cracking during hot processing. In the field of catalysis, the presence of sulfur impurities can easily poison the catalyst and corrode the material. Specifically, when preparing high-temperature processed products (such as high-density powder metallurgy structural parts, high-temperature alloys, etc.), the sulfur content in the raw materials is required to be below 10 ppm; when preparing chemical catalysts and other products for use at room temperature, the sulfur content in the raw materials is required to be 30-50 ppm.

[0004] In the process of iron recovery from solid waste, in addition to iron, solid waste often contains transition metal impurities such as nickel, cobalt, and manganese, as well as non-metallic impurities such as carbon, sulfur, and phosphorus. During the preparation of iron products, metallic impurities can be removed through processes such as pH adjustment, solid-liquid separation, and washing. A related technology provides a method for preparing high-purity ferrous sulfate, which removes metallic impurities by adjusting the solution pH, achieving a purity of 4N. However, the high sulfur content of ferrous sulfate limits its application in related fields.

[0005] Therefore, providing a method for removing sulfur from ferrous sulfate has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] This invention discloses a method for removing sulfur from high-purity ferrous sulfate using a combination of dry and wet methods, in order to solve the technical problem of high sulfur content in iron products recovered by related technologies.

[0007] To solve the above problems, the present invention adopts the following technical solution: The present invention provides a method for removing sulfur from high-purity ferrous sulfate using a combination of dry and wet methods, comprising the following steps: Step 100: Dissolve ferrous sulfate in warm water to obtain an aqueous solution of ferrous sulfate; Step 200: Add alkali to the ferrous sulfate aqueous solution to adjust the pH of the ferrous sulfate aqueous solution and convert the ferrous sulfate into iron hydroxyl compound precipitate; Step 300: Adjust the pH of the solid-liquid mixture of iron hydroxyl compound precipitate to 7-8, heat and age it, then separate the solid and liquid, wash and dry it to obtain iron hydroxyl compound; Step 400: Place the hydroxyl compounds of iron in a container and perform deep desulfurization of the hydroxyl compounds of iron through one or more of the following methods: high-temperature calcination, thermal shock, alternating positive and negative pressure, and dynamic cold quenching, to obtain iron oxides. Step 500: Wash, dry and reduce the iron oxides after deep desulfurization to obtain low-sulfur iron powder.

[0008] The present invention provides a method for removing sulfur from high-purity ferrous sulfate using a combination of dry and wet methods, comprising the following steps: Step 100: Place high-purity ferrous sulfate in a container and desulfurize it by one or more of the following methods: high-temperature calcination, thermal shock, alternating positive and negative pressure, and dynamic cold quenching, to obtain iron oxide. Step 200: Dissolve the iron oxide in hydrochloric acid solution to obtain an aqueous solution of iron salt; Step 300: Add alkali solution to the iron salt aqueous solution to adjust the pH of the iron salt aqueous solution and convert the iron salt into iron hydroxyl compound precipitate; Step 400: Adjust the pH of the solid-liquid mixture of iron hydroxyl compound precipitate to 7-8, heat and age, then separate the solid and liquid, wash and dry to obtain iron hydroxyl compound; Step 500: Place the hydroxyl compounds of iron in a container and perform deep desulfurization of the hydroxyl compounds of iron through one or more of the following methods: high-temperature calcination, thermal shock, alternating positive and negative pressure, and dynamic cold quenching, to obtain iron oxides. Step 600: Wash, dry and reduce the iron oxides after deep desulfurization to obtain ultra-low sulfur iron powder.

[0009] The technical solution adopted in this invention can achieve the following beneficial effects: Firstly, this invention provides a method for removing sulfur from high-purity ferrous sulfate using a combination of wet and dry methods. Firstly, the iron in the ferrous sulfate is precipitated (by ferric hydroxide or ferrous hydroxide) using a wet process, while the sulfate ions exist as sulfates. Through solid-liquid separation, preliminary desulfurization of the ferrous sulfate is achieved. Secondly, the hydroxyl compounds of the iron after preliminary desulfurization are transferred to a pyrometallurgical process for further desulfurization of the iron hydroxyl compounds. This combination of wet and dry desulfurization not only overcomes the bottleneck of wet desulfurization, achieving deep desulfurization of ferrous sulfate and reducing the sulfur content in the resulting product to below 20 ppm, meeting the sulfur impurity limits in fields such as catalysis, metallurgy, and magnetic materials, but also reduces the energy consumption of the subsequent pyrometallurgical desulfurization process and decreases sulfur dioxide emissions in the tail gas because most of the sulfur has already been removed in the wet process.

[0010] Secondly, the present invention provides a method for removing sulfur from high-purity ferrous sulfate using a combination of dry and wet methods. This method involves one or more of the following techniques: high-temperature calcination, thermal shock, alternating positive and negative pressure, and dynamic cold quenching. Under high-temperature conditions, these methods not only oxidize the sulfur in the hydroxyl compounds of iron into gaseous sulfur oxides (such as sulfur dioxide and / or sulfur trioxide) for discharge, thereby achieving deep desulfurization, but also induce microcracks in the hydroxyl compounds of iron, exposing sulfur impurities present in the interstitial spaces and / or particle pores. Subsequent washing and oxidation can further remove the sulfur impurities present in the interstitial spaces and / or particle pores.

[0011] Thirdly, the present invention's method for removing sulfur from high-purity ferrous sulfate using a combination of dry and wet processes allows for the formation of microcracks in the iron hydroxyl compounds. This exposes other non-metallic impurities (such as phosphorus, carbon, nitrogen, etc.) and metallic impurities (such as nickel, cobalt, manganese, etc.) existing in the interstitial spaces and / or particle pores. This further overcomes the bottleneck of impurity removal in wet processes, enabling deep removal of metallic impurities that are difficult to remove in wet processes, thereby further improving the purity of the desulfurized iron product. Moreover, after the lattice of the iron hydroxyl compounds is destroyed, the iron hydroxyl compounds can undergo lattice rearrangement under high-temperature conditions, further improving the purity of the desulfurized iron product. Detailed Implementation

[0012] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0013] In this application specification and claims, "and / or" means at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0014] The following is a detailed description of the method for removing sulfur from high-purity ferrous sulfate using a combination of dry and wet methods.

[0015] The method for removing sulfur from high-purity ferrous sulfate using a combination of dry and wet methods, as described in this application, includes the following steps: Step 100: Dissolve ferrous sulfate in warm water to obtain an aqueous solution of ferrous sulfate.

[0016] Preferably, when ferrous sulfate is dissolved in warm water, the mass concentration of iron is 2-5%. This application controls the mass concentration of iron to be less than 5% to avoid the formation of viscous iron hydroxyl compounds during the subsequent iron ion precipitation process, which would be difficult to filter.

[0017] Preferably, the temperature of the warm water is 40~50℃. This makes ferrous sulfate easier to dissolve.

[0018] Step 200: Add alkali to the ferrous sulfate aqueous solution to adjust the pH of the ferrous sulfate aqueous solution and convert the ferrous sulfate into iron hydroxyl compound precipitate.

[0019] The precipitate of iron with hydroxyl compounds can be either ferric hydroxide or ferrous hydroxide. The process for forming these two types of iron hydroxyl compound precipitates is described in detail below.

[0020] Preferably, the formation of ferric hydroxide precipitate includes the following process: adding an alkaline solution to an aqueous solution of ferrous sulfate, controlling the pH of the aqueous solution of ferrous sulfate to be 4-5, and then adding hydrogen peroxide to the aqueous solution of ferrous sulfate to oxidize the ferrous sulfate, thereby obtaining a solid-liquid mixture containing ferric hydroxide precipitate.

[0021] More preferably, when adding alkali and hydrogen peroxide to the ferrous sulfate aqueous solution, the temperature of the ferrous sulfate aqueous solution is maintained at 40-50°C. More preferably, the amount of hydrogen peroxide used is 1-1.2 times the theoretical amount (the amount theoretically needed to completely oxidize ferrous ions), and the concentration of hydrogen peroxide is 5-20%. Controlling the concentration of hydrogen peroxide to 5-20% allows the hydrogen peroxide to oxidize ferrous ions to ferric hydroxide as much as possible, avoiding the direct reaction of high-concentration hydrogen peroxide with ferrous ions to form ferrous hydroxide, which is colloidal and difficult to filter and wash in subsequent processes.

[0022] More preferably, the alkaline solution is one or more of ammonia, ammonium carbonate, ammonium bicarbonate, urea solution, sodium hydroxide, sodium carbonate, sodium bicarbonate, potassium hydroxide, potassium carbonate, and potassium bicarbonate. Particularly preferred is that the alkaline solution is ammonia, ammonium carbonate, ammonium bicarbonate, or urea solution. After such alkaline solutions are used to adjust the pH, ammonium ions are easily removed in subsequent processes, avoiding the introduction of other impurity ions.

[0023] Preferably, the formation of ferrous hydroxide precipitate includes the following process: adding an alkaline solution to an aqueous solution of ferrous sulfate, controlling the pH of the aqueous solution of ferrous sulfate to be 7-8, and obtaining a solid-liquid mixture containing ferrous hydroxide precipitate.

[0024] More preferably, the alkaline solution is one or more of ammonia, ammonium carbonate, ammonium bicarbonate, urea solution, sodium hydroxide, sodium carbonate, sodium bicarbonate, potassium hydroxide, potassium carbonate, and potassium bicarbonate. Particularly preferred is that the alkaline solution is ammonia, ammonium carbonate, ammonium bicarbonate, or urea solution. After such alkaline solutions are used to adjust the pH, ammonium ions are easily removed in subsequent processes, avoiding the introduction of other impurity ions.

[0025] More preferably, when adding alkali to the ferrous sulfate aqueous solution, the temperature of the ferrous sulfate aqueous solution is maintained at 40~50°C.

[0026] More preferably, after washing the ferrous hydroxide precipitate, the ferrous hydroxide precipitate is dissolved again to obtain a ferrous solution; an alkaline solution is added to the ferrous solution to control the pH of the ferrous solution to 7-8, thereby obtaining a solid-liquid mixture containing ferrous hydroxide precipitate; the steps of dissolving the ferrous hydroxide precipitate and reprecipitating the ferrous solution are repeated 1-5 times.

[0027] When ferrous sulfate forms ferrous hydroxide precipitate, the ferrous hydroxide is in a colloidal state, causing some sulfate ions to be encapsulated within it. This application addresses this by dissolving the ferrous hydroxide precipitate again to obtain a ferrous-containing solution, and then precipitating the ferrous-containing solution again. This process separates the sulfate ions encapsulated in the ferrous hydroxide, thereby improving the initial desulfurization effect in the wet process.

[0028] Step 300: Adjust the pH of the solid-liquid mixture of iron hydroxyl compound precipitate to 7-8, heat and age it, then separate the solid and liquid, wash and dry it to obtain iron hydroxyl compound.

[0029] In this step, the pH of the iron hydroxyl compound precipitate solid-liquid mixture is adjusted to 7-8 again, which can cause all the incompletely precipitated ferrous ions in the solid-liquid mixture to precipitate, thereby improving the iron yield.

[0030] Preferably, after adjusting the pH of the solid-liquid mixture containing the precipitated iron hydroxyl compounds, the temperature is raised to 80-100°C. This application, by increasing the temperature and then aging for 1-3 hours, allows the formed colloidal iron hydroxyl compounds to grow, facilitating the separation of the precipitated iron hydroxyl compounds in subsequent steps.

[0031] Preferably, the hydroxyl compound precipitate of iron is washed multiple times, and deionized water is added to the hydroxyl compound precipitate of iron at a solid-liquid mass ratio of 1:4 during each wash. This application, by repeatedly washing the hydroxyl compound precipitate of iron, can remove sulfates, sodium ions, etc., thereby improving the initial desulfurization effect in the wet process.

[0032] Step 400: Place the hydroxyl compounds of iron in a container and perform deep desulfurization of the hydroxyl compounds of iron through one or more of the following methods: high-temperature calcination, thermal shock, alternating positive and negative pressure, and dynamic cold quenching, to obtain iron oxide.

[0033] In this step, sulfur existing in the interstices of the crystal lattice and / or the pores of the particles can be removed by one or more methods such as high-temperature calcination, thermal shock, alternating positive and negative pressure, and dynamic cold quenching, so as to achieve deep desulfurization.

[0034] The high-temperature calcination method, the thermal quenching method, the alternating positive and negative pressure method, and the dynamic cold quenching method will be explained in detail in the following sections.

[0035] Step 500: Wash, dry and reduce the iron oxides after deep desulfurization to obtain low-sulfur iron powder.

[0036] Preferably, the iron oxides after deep desulfurization are placed in warm water at 50-70°C, stirred evenly for washing, and then the washing product is subjected to solid-liquid separation. The solid material obtained after solid-liquid separation is then placed in a drying oven and dried at 100-200°C for 30-60 minutes. This application, through the washing step, can remove impurities such as sulfates in the deep desulfurization process by water washing, thereby further improving the deep desulfurization effect.

[0037] Preferably, the dried solid material is placed in a reduction furnace, hydrogen is introduced into the reduction furnace, and the furnace is heated to 400~450℃ to reduce the deeply desulfurized iron oxide into iron powder; after the reaction is completed, inert gas is introduced into the reduction furnace, and after cooling and vacuuming, low-sulfur iron powder is obtained.

[0038] The low-sulfur iron powder obtained in this application has a sulfur content of less than 20 ppm and can be used in the manufacture of downstream products.

[0039] Not limited to this, after deep desulfurization by pyrometallurgical process, ferric oxide product is obtained with a sulfur content of less than 20 ppm, which can be used in the manufacture of downstream products without the need for hydrogen reduction.

[0040] This application presents a method for removing sulfur from high-purity ferrous sulfate using a combination of wet and dry methods. First, the iron in the ferrous sulfate is precipitated (by ferric hydroxide or ferrous hydroxyl oxide) using a wet process, while the sulfate ions exist as sulfates. Through solid-liquid separation, preliminary desulfurization of the ferrous sulfate is achieved. Second, the hydroxyl compounds of the iron after preliminary desulfurization are transferred to a pyrometallurgical process for further desulfurization of the iron hydroxyl compounds. This combination of wet and dry desulfurization not only overcomes the bottleneck of wet desulfurization, achieving deep desulfurization of ferrous sulfate and reducing the sulfur content in the resulting product to below 20 ppm, meeting the sulfur impurity limits in fields such as catalysis, metallurgy, and magnetic materials, but also reduces the energy consumption of the subsequent pyrometallurgical desulfurization process and decreases sulfur dioxide emissions in the tail gas because most of the sulfur has already been removed in the wet process.

[0041] This application describes a method for removing sulfur from high-purity ferrous sulfate using a combination of dry and wet methods. This method involves one or more of the following techniques: high-temperature calcination, thermal shock, alternating positive and negative pressure, and dynamic cold quenching. Under high-temperature conditions, these methods not only oxidize the sulfur in the iron's hydroxyl compounds into gaseous sulfur oxides (such as sulfur dioxide and / or sulfur trioxide) for discharge, thus achieving deep desulfurization, but also create microcracks in the iron's hydroxyl compounds, exposing sulfur impurities present in the interstitial crystal lattice and / or particle pores. Subsequent washing and oxidation can further remove these sulfur impurities.

[0042] This application presents a method combining wet and dry processes for removing sulfur from high-purity ferrous sulfate. After the iron hydroxyl compounds generate microcracks, they expose other non-metallic impurities (such as phosphorus, carbon, and nitrogen) and metallic impurities (such as nickel, cobalt, and manganese) existing in the interstitial spaces and / or particle pores. This further overcomes the bottleneck of impurity removal in wet processes, enabling deep removal of metallic impurities that are difficult to remove in wet processes, thereby further improving the purity of the desulfurized iron product. Furthermore, after the lattice of the iron hydroxyl compounds is destroyed, under high-temperature conditions, the iron hydroxyl compounds can undergo lattice rearrangement, further improving the purity of the desulfurized iron product.

[0043] Preferably, the high-temperature calcination method involves the deep desulfurization of iron hydroxyl compounds through the following steps: The hydroxyl compound of iron is placed in a high-temperature container, and both the hydroxyl compound of iron and the high-temperature container are heated to above 600°C. For example, the temperature may be 600°C, 700°C, 800°C, 900°C, 1000°C, 1100°C, or 1200°C.

[0044] Maintain the temperature inside the high-temperature container at above 600°C, introduce oxygen into the container, stir evenly, and subject the iron hydroxyl compound to high-temperature oxygen calcination for 30 to 120 minutes. For example, the gas-solid ratio of oxygen to the iron hydroxyl compound is 1 to 2 L / min : 100 g.

[0045] This method, through high-temperature calcination, oxidizes the sulfur element in the hydroxyl compounds of iron into gaseous sulfur oxides (such as sulfur dioxide and / or sulfur trioxide) which are then discharged, thereby achieving deep desulfurization.

[0046] This application introduces oxygen into the corundum crucible via bottom blowing. Introducing oxygen into the high-temperature vessel not only oxidizes the sulfur in the iron hydroxyl compounds into gaseous sulfur oxides (such as sulfur dioxide and / or sulfur trioxide) and removes them, but also keeps the iron hydroxyl compounds in the corundum crucible in a fluidized state, thereby improving reaction efficiency and ensuring the complete conversion of sulfur impurities.

[0047] Preferably, the thermal desulfurization method performs deep desulfurization of iron hydroxyl compounds through the following steps: A high-temperature container is heated to above 1000°C, and then the iron hydroxyl compound is placed in the container and rapidly heated. Oxygen is then introduced into the container, and the mixture is stirred until homogeneous, thus subjecting the iron hydroxyl compound to high-temperature oxygen-charging calcination. More preferably, the high-temperature oxygen-charging calcination time for the iron hydroxyl compound is 5-30 minutes. More preferably, the gas-solid ratio of oxygen to iron hydroxyl compound is 1-2 L / min: 100 g; and / or, oxygen is introduced into the corundum crucible via bottom blowing.

[0048] After high-temperature oxygen-charging roasting, the product obtained is placed in a low-temperature container for cryogenic quenching, stirred evenly, and then rapidly cooled to below 10°C. More preferably, the low-temperature container is a container holding a cryogenic substance, such as ice, an ice-water mixture, a calcium chloride brine dry ice-ethanol solution, a dry ice-isopropanol solution, a dry ice-ethylene glycol solution, liquid nitrogen, liquid argon, liquid oxygen, or liquid hydrogen. The cryogenic quenching time for the high-temperature oxygen-charging roasted product is 1–5 minutes.

[0049] After the low-temperature quenching is completed, the product obtained from the low-temperature quenching is washed, separated from the solid and liquid, dried, ground, and then placed in a high-temperature container for rapid heating.

[0050] Repeat the steps of high-temperature oxygen-assisted roasting, low-temperature quenching, and washing 2 to 5 times. More preferably, repeat the steps of high-temperature oxygen-assisted roasting, low-temperature quenching, and washing 2 to 5 times.

[0051] The thermal desulfurization process lasts from 30 to 120 minutes and is used for deep desulfurization of hydroxyl compounds in iron.

[0052] In this method, iron hydroxyl compounds are subjected to rapid heating in a high-temperature environment, which generates lattice stress and microcracks inside the iron hydroxyl compound particles. This exposes sulfur impurities existing in the lattice gaps and / or particle pores. Then, through high-temperature oxygen-filled roasting, the sulfur element in the iron hydroxyl compounds is oxidized into gaseous sulfur oxides (such as sulfur dioxide and / or sulfur trioxide) and discharged, thereby achieving deep desulfurization.

[0053] Furthermore, by rapidly heating the iron hydroxyl compound in a high-temperature environment, lattice stress and microcracks are generated inside the iron hydroxyl compound particles. Then, by rapidly cooling the iron hydroxyl compound in a low-temperature environment, the iron hydroxyl compound lattice and sulfur impurities existing in the lattice gaps and / or particle pores undergo rapid contraction. Due to the difference in thermal expansion coefficients between the main phase and the impurity phase, the microcracks in the iron hydroxyl compound further expand, thereby exposing the sulfur impurities existing in the lattice gaps and / or particle pores more fully. These impurities can then be further removed by washing and oxidation.

[0054] Beyond this, the microcracks generated in the iron hydroxyl compound particles expose non-metallic impurities (such as phosphorus, carbon, and nitrogen) and metallic impurities (such as nickel, cobalt, and manganese) existing in the interstitial spaces and / or particle pores. This overcomes the impurity removal bottleneck of wet processes, enabling deep removal of metallic impurities that are difficult to remove in wet processes. Crucially, after the lattice of the iron hydroxyl compounds is disrupted, lattice rearrangement can occur under high-temperature conditions, further improving the purity of the desulfurized iron product.

[0055] Preferably, the alternating positive and negative pressure method performs deep desulfurization of hydroxyl compounds in iron through the following steps: The iron hydroxyl compound is placed in a container, a heating program is initiated, and the temperature inside the container is raised to above 1000°C. Simultaneously, a vacuum is applied to maintain a negative pressure of -100 kPa to -80 kPa inside the container. More preferably, the negative pressure is maintained for 5 to 15 minutes.

[0056] Maintain the temperature inside the container above 1000℃, and then introduce oxygen into the container until a positive pressure of 80 kPa to 100 kPa is maintained inside the container. More preferably, the positive pressure is maintained for 5 to 15 minutes.

[0057] Repeat the operation of maintaining negative pressure and maintaining positive pressure 2 to 5 times. More preferably, repeat the operation of maintaining negative pressure and maintaining positive pressure 2 to 5 times.

[0058] The alternating positive and negative pressure method lasts for 30 to 120 minutes to deeply desulfurize the hydroxyl compounds of iron.

[0059] In this method, during the negative pressure stage, by drawing negative pressure into the container, the volatilized or decomposed gases (such as H2S, SO2, and sulfur vapor) inside the container can be discharged, reducing the gaseous concentration of sulfur inside the container and creating a concentration difference between the inside and outside of the iron hydroxyl compound. This provides mass transfer impetus for the continuous diffusion of sulfur within the iron hydroxyl compound, forcing sulfur in the pores and lattice of the iron hydroxyl compound to continuously volatilize to the surface of the iron hydroxyl compound, thereby improving the sulfur removal effect. In addition, the method of removing impurities from iron hydroxyl compounds by alternating positive and negative pressure in this application also slightly expands the pore structure of the iron hydroxyl compound during the negative pressure stage, allowing sulfur in the lattice or encapsulated state of the iron hydroxyl compound to be exposed, while also providing a channel for oxygen to enter the lattice or pores.

[0060] During the positive pressure stage, the positive pressure forces oxygen into the pores and microcracks of the iron's hydroxyl compounds. Combined with the high-temperature environment exceeding 1000°C within the container, this provides activation energy for the chemical reaction of sulfur, allowing oxygen to oxidize the sulfur within the iron's hydroxyl compounds, thus facilitating deep desulfurization. By cyclically executing negative and positive pressure steps, and through the superposition of multiple physical stresses, sulfur present in the interstitial spaces and / or pores of the iron's hydroxyl compounds, or sulfur that is trapped within them, is gradually exposed. Combined with oxidative roasting, this alters the chemical form of sulfur, achieving deep desulfurization and yielding high-purity iron products with low sulfur content.

[0061] Preferably, the dynamic cold quenching method performs deep desulfurization of hydroxyl compounds in iron through the following steps: A high-temperature container is heated to above 600°C, and then the iron hydroxyl compound is placed in the container and rapidly heated; or the iron hydroxyl compound is placed in a high-temperature container, and both the iron hydroxyl compound and the high-temperature container are simultaneously heated to above 600°C, and then oxygen is introduced into the high-temperature container, stirred evenly, and the iron hydroxyl compound is subjected to high-temperature oxygen-charging calcination. More preferably, the gas-solid ratio of oxygen to iron hydroxyl compound is 1~2 L / min:100g; and / or, oxygen is introduced into the corundum crucible by bottom blowing.

[0062] During the high-temperature oxygen-charging roasting process, a cooling medium is sprayed onto the surface of the iron hydroxyl compound. This cooling medium is used for quenching the iron hydroxyl compound. The cooling medium is water, and the spraying volume is 1-3 mL per 100 g of iron hydroxyl compound. The time interval between spraying the cooling medium onto the surface of the iron hydroxyl compound is 3-5 minutes. However, the cooling medium can also be sodium hydroxide solution, potassium hydroxide solution, or ammonia solution.

[0063] The high-temperature oxygen-assisted roasting lasts for 30 to 120 minutes to deeply desulfurize the hydroxyl compounds of iron.

[0064] In this method, during the high-temperature oxygen-filled roasting process, a cooling medium is sprayed onto the surface of the iron hydroxyl compound. A huge temperature difference is formed between the cooling medium and the surface of the iron hydroxyl compound. The cooling medium rapidly quenches the iron hydroxyl compound and generates thermal stress on the surface of the iron hydroxyl compound, which can cause microcracks in the iron hydroxyl compound. This exposes the sulfur impurities that originally existed in the interstitial spaces and / or particle pores. After being roasted again by high-temperature oxygen filling, deep desulfurization can be further achieved.

[0065] Beyond this, the microcracks generated in the iron hydroxyl compound particles expose non-metallic impurities (such as phosphorus, carbon, and nitrogen) and metallic impurities (such as nickel, cobalt, and manganese) existing in the interstitial spaces and / or particle pores. This overcomes the impurity removal bottleneck of wet processes, enabling deep removal of metallic impurities that are difficult to remove in wet processes. Crucially, after the lattice of the iron hydroxyl compounds is disrupted, lattice rearrangement can occur under high-temperature conditions, further improving the purity of the desulfurized iron product.

[0066] On the other hand, the method of removing sulfur from the hydroxyl compounds of iron by dynamic cold quenching of this application sprays a cooling medium onto the surface of the hydroxyl compounds of iron, which can instantly "freeze" the sulfate. The "frozen" sulfate can be removed by washing in the future, avoiding the problem that the sulfate is difficult to remove by washing because it dissolves or solidifies (returns to the interstitial space, particle pores or is wrapped by the lattice).

[0067] When performing deep desulfurization of hydroxyl compounds in iron using the dynamic cold quenching method of this application, it is not limited to using liquid to quench the hydroxyl compounds in iron; gas can also be used to quench the hydroxyl compounds in iron.

[0068] Preferably, after obtaining the iron oxide in step 400 and before washing, drying, and reducing the iron oxide in step 500, the following steps are also included: Iron oxides are dissolved in hydrochloric acid solution to obtain an aqueous solution of iron salts; Repeat steps 200 to 400 at least once to obtain ultra-low sulfur iron oxide.

[0069] The ultra-low sulfur iron oxides are then washed, dried, and reduced to obtain ultra-low sulfur iron powder.

[0070] After obtaining low-sulfur iron powder, this application repeats the wet desulfurization-pyrometallurgical desulfurization steps. In the wet step, hydroxyl iron oxide precipitate is obtained through dissolution and precipitation and solid-liquid separation. Some impurities are dissolved in the filtrate, which can further remove impurities. Moreover, the iron compound crystal form can be reconstructed through the wet step. Then, pyrometallurgical desulfurization is carried out, which can break through the limit of single pyrometallurgical desulfurization, so as to further remove sulfur impurities in low-sulfur iron powder and obtain ultra-low sulfur iron powder with a sulfur content of less than 1 ppm.

[0071] This application also provides another method for removing sulfur from high-purity ferrous sulfate using a combination of dry and wet methods. Preferably, the method for removing sulfur from high-purity ferrous sulfate using a combination of dry and wet methods includes the following steps: Step 100: Place high-purity ferrous sulfate in a container and desulfurize it by one or more of the following methods: high-temperature calcination, thermal shock, alternating positive and negative pressure, and dynamic cold quenching, to obtain iron oxide. Step 200: Dissolve the iron oxide in hydrochloric acid solution to obtain an aqueous solution of iron salt; Step 300: Add alkali solution to the iron salt aqueous solution to adjust the pH of the iron salt aqueous solution and convert the iron salt into iron hydroxyl compound precipitate; Step 400: Adjust the pH of the solid-liquid mixture of iron hydroxyl compound precipitate to 7-8, heat and age, then separate the solid and liquid, wash and dry to obtain iron hydroxyl compound; Step 500: Place the hydroxyl compounds of iron in a container and perform deep desulfurization of the hydroxyl compounds of iron through one or more of the following methods: high-temperature calcination, thermal shock, alternating positive and negative pressure, and dynamic cold quenching, to obtain iron oxides. Step 600: Wash, dry and reduce the iron oxides after deep desulfurization to obtain ultra-low sulfur iron powder.

[0072] The specific operating procedures for each step can be found in the first method of removing sulfur from high-purity ferrous sulfate using a combination of dry and wet methods, and will not be repeated here.

[0073] The iron oxide mentioned in this embodiment refers to one or more of ferric oxide, iron(II) oxide, and ferrous oxide.

[0074] This application first uses pyrometallurgical desulfurization to obtain iron oxides, and the sulfur content in the obtained iron oxides can be reduced to less than 50 ppm. At this point, the iron oxide crystal form is stable and it is difficult to continue desulfurization. Then, this application uses a wet process to dissolve the iron oxides and convert them into iron hydroxyl compounds, thereby reconstructing the crystal form of the iron compounds. Then, it uses pyrometallurgical desulfurization again to further remove sulfur impurities from the iron hydroxyl compounds, breaking through the limit of single pyrometallurgical desulfurization and obtaining ultra-low sulfur iron powder with a sulfur content of less than 1 ppm.

[0075] The method for removing sulfur from high-purity ferrous sulfate using a combination of dry and wet methods, provided in this application, will be described in detail below through specific embodiments.

[0076] The ferrous sulfate used in each example was high-purity ferrous sulfate that had been purified and dried, and its composition was analyzed as follows: 21% sulfur, 25.8 ppm carbon, 0 ppm phosphorus, 8.4 ppm sodium, 1.6 ppm magnesium, 0.5 ppm aluminum, 1.0 ppm potassium, 2.8 ppm calcium, 1.2 ppm boron, 0.2 ppm titanium, 0.05 ppm chromium, 0.08 ppm manganese, 0.06 ppm nickel, and 0.02 ppm copper.

[0077] Example 1 This embodiment describes a method for removing sulfur from high-purity ferrous sulfate using a combination of dry and wet methods, including the following steps: Step 100: Using 150g of ferrous sulfate as raw material, dissolve the ferrous sulfate in 50℃ warm water and stir evenly to obtain a ferrous sulfate aqueous solution with an iron mass concentration of 3%.

[0078] Step 200: Add 25% ammonia to the ferrous sulfate aqueous solution to adjust the pH of the ferrous sulfate aqueous solution to 4. Then add 10% hydrogen peroxide to the ferrous sulfate aqueous solution. The amount of hydrogen peroxide used is 1.2 times the theoretical amount. The hydrogen peroxide oxidizes the ferrous sulfate and obtains a solid-liquid mixture containing ferric hydroxide precipitate. When adding ammonia and hydrogen peroxide to the ferrous sulfate aqueous solution, maintain the temperature of the ferrous sulfate aqueous solution at 50°C.

[0079] Step 300: Add 25% ammonia water to the solid-liquid mixture containing ferric hydroxide precipitate, adjust the pH of the ferric hydroxide precipitate solid-liquid mixture to 8, heat to 100℃, age for 1 hour, filter, and wash 4 times with deionized water at a solid-liquid mass ratio of 1:4. After filtration, place the ferric hydroxide in a 105℃ oven and dry for 60 minutes to obtain solid ferric hydroxide.

[0080] The amount of iron hydroxyl oxide in this embodiment was 86.7 g. The impurity elements and their contents in the iron hydroxyl oxide were detected using an infrared carbon-sulfur analyzer and ICP-MS. The impurities in the iron hydroxyl oxide are shown in Table 1 below.

[0081] Table 1. Impurity elements and their contents in ferric hydroxide in this embodiment. Step 400: Heat the corundum crucible to 1000℃ and introduce oxygen from the bottom of the crucible at a flow rate of 1L / min. Using 80g of ferric hydroxide as raw material, add the ferric hydroxide to the corundum crucible in three batches and heat rapidly. After each batch is added, stir thoroughly before adding the next batch. Maintain the temperature of the corundum crucible at 1000℃ and perform high-temperature oxygen-charged calcination of the ferric hydroxide for 10 minutes.

[0082] After the high-temperature oxygen-charging roasting is completed, the product obtained by high-temperature oxygen-charging roasting is poured into a low-temperature container filled with ice for rapid cooling, stirred evenly, and then subjected to low-temperature quenching for 3 minutes.

[0083] After the low-temperature quenching is completed, the product obtained by low-temperature quenching is poured into 60℃ warm water and stirred and washed for 10 minutes. After washing, the washed product is filtered. The filtered solid material is placed in a 120℃ oven and dried for 60 minutes. Then it is naturally cooled to room temperature. The dried solid material is then sent to a grinder and ground for 3 seconds.

[0084] Then, the steps of rapid heating, low-temperature quenching, and washing were repeated three times to obtain low-sulfur ferric oxide.

[0085] Step 500: Argon gas is introduced into the reduction furnace to purge the air. The obtained low-sulfur ferric oxide is then placed in the reduction furnace, hydrogen gas is introduced, and the furnace is heated to 400°C to reduce the low-sulfur ferric oxide to iron powder. After the reduction reaction is complete, the hydrogen gas is turned off, argon gas is introduced into the reduction furnace, the temperature is lowered to below 200°C, a vacuum is drawn for 60 minutes, and the furnace is allowed to cool naturally to room temperature to obtain low-sulfur iron powder.

[0086] The amount of low-sulfur iron powder in this embodiment was 47.5g. The impurity elements and their contents in the low-sulfur iron powder were detected using an infrared carbon-sulfur analyzer and ICP-MS. The impurities in the low-sulfur iron powder are shown in Table 2 below.

[0087] Table 2. Impurity elements and their contents in the low-sulfur iron powder of this embodiment. Example 2 This embodiment describes a method for removing sulfur from high-purity ferrous sulfate using a combination of dry and wet methods, including the following steps: Step 100: Using 150g of ferrous sulfate as raw material, dissolve the ferrous sulfate in 50℃ warm water and stir evenly to obtain a ferrous sulfate aqueous solution with an iron mass concentration of 3%.

[0088] Step 200: Add 25% ammonia water to the ferrous sulfate aqueous solution to adjust the pH of the ferrous sulfate aqueous solution to 7, and then obtain a solid-liquid mixture containing ferrous hydroxide precipitate; when adding ammonia water to the ferrous sulfate aqueous solution, keep the temperature of the ferrous sulfate aqueous solution at 50°C.

[0089] Step 300: Add 25% ammonia water to the solid-liquid mixture containing ferrous hydroxide precipitate, adjust the pH of the ferrous hydroxide precipitate solid-liquid mixture to 8, heat to 100℃, age for 1 hour, filter, and wash 4 times with deionized water at a solid-liquid mass ratio of 1:4. After filtration, place the ferrous hydroxide in a 120℃ oven and dry for 60 minutes to obtain solid ferrous hydroxide.

[0090] The amount of ferrous hydroxide in this embodiment was 85.7g. The impurity elements and their contents in the ferrous hydroxide were detected using an infrared carbon-sulfur analyzer and ICP-MS. The impurities in the ferrous hydroxide are shown in Table 3 below.

[0091] Table 3. Impurity elements and their contents in ferrous hydroxide in this embodiment. Step 400: Heat the corundum crucible to 1000℃ and introduce oxygen from the bottom of the crucible at a flow rate of 1L / min. Using 80g of ferrous hydroxide as raw material, add the ferrous hydroxide to the corundum crucible in three batches and heat rapidly. After each batch is added, stir thoroughly before adding the next batch. Maintain the temperature of the corundum crucible at 1000℃ and perform high-temperature oxygen-charged calcination of the ferrous hydroxide for 10 minutes.

[0092] After the high-temperature oxygen-charging roasting is completed, the product obtained by high-temperature oxygen-charging roasting is poured into a low-temperature container filled with ice for rapid cooling, stirred evenly, and then subjected to low-temperature quenching for 3 minutes.

[0093] After the low-temperature quenching is completed, the product obtained by low-temperature quenching is poured into 60℃ warm water and stirred and washed for 10 minutes. After washing, the washed product is filtered. The filtered solid material is placed in a 120℃ oven and dried for 60 minutes. Then it is naturally cooled to room temperature. The dried solid material is then sent to a grinder and ground for 3 seconds.

[0094] Then, the steps of rapid heating, low-temperature quenching, and washing were repeated three times to obtain low-sulfur ferric oxide.

[0095] Step 500: Argon gas is introduced into the reduction furnace to purge the air. The obtained low-sulfur ferric oxide is then placed in the reduction furnace, hydrogen gas is introduced, and the furnace is heated to 400°C to reduce the low-sulfur ferric oxide to iron powder. After the reduction reaction is complete, the hydrogen gas is turned off, argon gas is introduced into the reduction furnace, the temperature is lowered to below 200°C, a vacuum is drawn for 60 minutes, and the furnace is allowed to cool naturally to room temperature to obtain low-sulfur iron powder.

[0096] The amount of low-sulfur iron powder in this embodiment was 47.8g. The impurity elements and their contents in the low-sulfur iron powder were detected using an infrared carbon-sulfur analyzer and ICP-MS. The impurities in the low-sulfur iron powder are shown in Table 4 below.

[0097] Table 4. Impurity elements and their contents in the low-sulfur iron powder of this embodiment. Example 3 The method for removing sulfur from high-purity ferrous sulfate using a combination of dry and wet methods in this embodiment differs from that in Example 2 in that: In step 300, the solid-liquid mixture containing ferrous hydroxide precipitate is separated, and 10% hydrochloric acid by mass is added to the ferrous hydroxide precipitate and stirred evenly to completely dissolve the ferrous hydroxide precipitate, thereby obtaining a ferrous solution.

[0098] Then, 25% ammonia was added to the ferrous sulfate solution to adjust the pH of the ferrous sulfate solution to 7, thus obtaining a solid-liquid mixture containing ferrous hydroxide precipitate. When adding ammonia to the ferrous sulfate solution, the temperature of the ferrous sulfate solution was kept at 50°C.

[0099] Repeat the steps of dissolving ferrous hydroxide precipitate and reprecipitating it with ferrous solution three times.

[0100] Add 25% ammonia water to the solid-liquid mixture containing ferrous hydroxide precipitate to adjust the pH of the mixture to 8. After heating to 100℃ and aging for 1 hour, filter the mixture and wash it 4 times with deionized water at a solid-liquid mass ratio of 1:4. After filtration, dry the ferrous hydroxide in a 120℃ oven for 60 minutes to obtain solid ferrous hydroxide.

[0101] The remaining steps are the same as in Example 2, and will not be repeated here.

[0102] The amount of ferrous hydroxide in this example was 84.1 g. The impurity elements and their contents in the ferrous hydroxide were detected using an infrared carbon-sulfur analyzer and ICP-MS. The impurities in the ferrous hydroxide are shown in Table 5 below.

[0103] Table 5. Impurity elements and their contents in ferrous hydroxide in this embodiment. Example 4 The method for removing sulfur from high-purity ferrous sulfate using a combination of dry and wet methods in this embodiment differs from that in Example 1 in that: Step 400: The steps of rapid heating, low-temperature quenching, and washing are repeated 5 times to obtain low-sulfur ferric oxide. The remaining steps are the same as in Example 1 and will not be repeated here.

[0104] The amount of low-sulfur iron powder in this embodiment was 46.6g. The impurity elements and their contents in the low-sulfur iron powder were detected using an infrared carbon-sulfur analyzer and ICP-MS. The impurities in the low-sulfur iron powder are shown in Table 6 below.

[0105] Table 6. Impurity elements and their contents in the low-sulfur iron powder of this embodiment. Example 5 The method for removing sulfur from high-purity ferrous sulfate using a combination of dry and wet methods in this embodiment differs from that in Example 1 in that: In step 400, 80g of ferric hydroxide is used as raw material. The ferric hydroxide is placed into an alumina crucible all at once, and the alumina crucible and ferric hydroxide are heated to 600°C using a programmed temperature increase (10°C / min). The temperature of the alumina crucible is maintained at 600°C, and oxygen is introduced from the bottom of the alumina crucible at a flow rate of 1L / min. The mixture is stirred thoroughly, and the ferric hydroxide is subjected to high-temperature oxygen calcination for 60 minutes. The remaining steps are the same as in Example 1 and will not be repeated here.

[0106] The amount of low-sulfur iron powder in this embodiment was 46.9g. The impurity elements and their contents in the low-sulfur iron powder were detected using an infrared carbon-sulfur analyzer and ICP-MS. The impurities in the low-sulfur iron powder are shown in Table 7 below.

[0107] Table 7. Impurity elements and their contents in the low-sulfur iron powder of this embodiment. Example 6 The method for removing sulfur from high-purity ferrous sulfate using a combination of dry and wet methods in this embodiment differs from that in Example 1 in that: In step 400, 80g of ferric hydroxide is used as raw material. The ferric hydroxide is placed into an alumina crucible all at once, and the alumina crucible and ferric hydroxide are heated to 800°C using a programmed temperature increase (10°C / min). The temperature of the alumina crucible is maintained at 800°C, and oxygen is introduced from the bottom of the alumina crucible at a flow rate of 1L / min. The mixture is stirred thoroughly, and the ferric hydroxide is subjected to high-temperature oxygen calcination for 60 minutes. The remaining steps are the same as in Example 1 and will not be repeated here.

[0108] The amount of low-sulfur iron powder in this embodiment was 46.5g. The impurity elements and their contents in the low-sulfur iron powder were detected using an infrared carbon-sulfur analyzer and ICP-MS. The impurities in the low-sulfur iron powder are shown in Table 8 below.

[0109] Table 8. Impurity elements and their contents in the low-sulfur iron powder of this embodiment. Example 7 The method for removing sulfur from high-purity ferrous sulfate using a combination of dry and wet methods in this embodiment differs from that in Example 1 in that: In step 400, 80g of ferric hydroxide is used as raw material. The ferric hydroxide is placed into an alumina crucible all at once, and the alumina crucible and ferric hydroxide are heated to 800°C using a programmed temperature increase (10°C / min). The temperature of the alumina crucible is maintained at 800°C, and oxygen is introduced from the bottom of the alumina crucible at a flow rate of 1L / min. The mixture is stirred thoroughly, and the ferric hydroxide is subjected to high-temperature oxygen calcination for 30 minutes. The remaining steps are the same as in Example 1 and will not be repeated here.

[0110] The amount of low-sulfur iron powder in this embodiment was 46.9g. The impurity elements and their contents in the low-sulfur iron powder were detected using an infrared carbon-sulfur analyzer and ICP-MS. The impurities in the low-sulfur iron powder are shown in Table 9 below.

[0111] Table 9. Impurity elements and their contents in the low-sulfur iron powder of this embodiment. Example 8 The method for removing sulfur from high-purity ferrous sulfate using a combination of dry and wet methods in this embodiment differs from that in Example 1 in that: In step 400, 80g of ferric hydroxide is placed into a quartz tube at once, and the heating program is started (10℃ / min). At the same time, a vacuum is drawn to maintain a negative pressure of -95Kpa inside the quartz tube. When the temperature inside the quartz tube reaches 1000℃ and the pressure is -95Kpa, it is maintained for 10 minutes.

[0112] Maintain the temperature inside the quartz tube at 1000℃, and simultaneously introduce oxygen into the quartz tube until the pressure displayed inside the quartz tube reaches 90 kPa, then maintain this temperature for 10 minutes.

[0113] The process of maintaining negative pressure and positive pressure was repeated three times, followed by cooling and annealing, to obtain low-sulfur ferric oxide.

[0114] The remaining steps are the same as in Example 1, and will not be repeated here.

[0115] The amount of low-sulfur iron powder in this embodiment was 45.4g. The impurity elements and their contents in the low-sulfur iron powder were detected using an infrared carbon-sulfur analyzer and ICP-MS. The impurities in the low-sulfur iron powder are shown in Table 10 below.

[0116] Table 10. Impurity elements and their contents in the low-sulfur iron powder of this embodiment. Example 9 The method for removing sulfur from high-purity ferrous sulfate using a combination of dry and wet methods in this embodiment differs from that in Example 1 in that: In step 400, 80g of ferric hydroxide is placed into a quartz tube at once, and the heating program is started (10℃ / min). At the same time, a vacuum is drawn to maintain a negative pressure of -80Kpa inside the quartz tube. When the temperature inside the quartz tube reaches 1000℃ and the pressure is -80Kpa, it is maintained for 10 minutes.

[0117] Maintain the temperature inside the quartz tube at 1000℃, and simultaneously introduce oxygen into the quartz tube until the pressure displayed inside the quartz tube reaches 80 kPa, then maintain this temperature for 10 minutes.

[0118] The process of maintaining negative pressure and positive pressure was repeated three times, followed by cooling and annealing, to obtain low-sulfur ferric oxide.

[0119] The remaining steps are the same as in Example 1, and will not be repeated here.

[0120] The amount of low-sulfur iron powder in this embodiment was 45.7g. The impurity elements and their contents in the low-sulfur iron powder were detected using an infrared carbon-sulfur analyzer and ICP-MS. The impurities in the low-sulfur iron powder are shown in Table 11 below.

[0121] Table 11. Impurity elements and their contents in the low-sulfur iron powder of this embodiment. Example 10 The method for removing sulfur from high-purity ferrous sulfate using a combination of dry and wet methods in this embodiment differs from that in Example 1 in that: In step 400, 80g of ferric hydroxide is used as raw material. The ferric hydroxide is placed into an alumina crucible all at once, and the alumina crucible and ferric hydroxide are heated to 600°C. Then, oxygen is introduced from the bottom of the alumina crucible at a flow rate of 1L / min to perform high-temperature oxygen-assisted calcination of the ferric hydroxide. The temperature of the alumina crucible is maintained at 600°C, and the ferric hydroxide is subjected to high-temperature oxygen-assisted calcination for 60 minutes.

[0122] During the high-temperature oxygen-charging roasting of ferric hydroxide, 0.8 mL of water was sprayed onto the surface of the iron-containing material every 3 minutes to quench it. Cooling medium was sprayed onto the surface of the iron-containing material without stirring. Ten seconds after the cooling medium spraying was completed, the iron-containing material was stirred again. This process continued until the high-temperature oxygen-charging roasting was finished.

[0123] After the high-temperature oxygen calcination is completed, the temperature inside the corundum crucible is reduced to 300℃ and held for 10 minutes; then the temperature inside the corundum crucible is reduced to room temperature by a programmed cooling method (10℃ / min).

[0124] The remaining steps are the same as in Example 1, and will not be repeated here.

[0125] The amount of low-sulfur iron powder in this embodiment was 45.8g. The impurity elements and their contents in the low-sulfur iron powder were detected using an infrared carbon-sulfur analyzer and ICP-MS. The impurities in the low-sulfur iron powder are shown in Table 12 below.

[0126] Table 12. Impurity elements and their contents in the low-sulfur iron powder of this embodiment. Example 11 The method for removing sulfur from high-purity ferrous sulfate using a combination of dry and wet methods in this embodiment differs from that in Example 10 in that, in step 400, the ferric hydroxide is subjected to high-temperature oxygen calcination for 30 minutes. The remaining steps are the same as in Example 10 and will not be repeated here.

[0127] The amount of low-sulfur iron powder in this embodiment was 46.2g. The impurity elements and their contents in the low-sulfur iron powder were detected using an infrared carbon-sulfur analyzer and ICP-MS. The impurities in the low-sulfur iron powder are shown in Table 13 below.

[0128] Table 13. Impurity elements and their contents in the low-sulfur iron powder of this embodiment. Example 12 The method for removing sulfur from high-purity ferrous sulfate using a combination of dry and wet methods in this embodiment differs from that in Example 1 in that: in step 100, 150g of ferrous sulfate is dissolved in warm water at 50°C and stirred evenly to obtain a ferrous sulfate aqueous solution with an iron mass concentration of 5%. The remaining steps are the same as in Example 1 and will not be repeated here.

[0129] The amount of iron hydroxyl oxide in this embodiment was 86.5 g. The impurity elements and their contents in the iron hydroxyl oxide were detected using an infrared carbon-sulfur analyzer and ICP-MS. The impurities in the iron hydroxyl oxide are shown in Table 14 below.

[0130] Table 14. Impurity elements and their contents in ferric hydroxide in this embodiment. Example 13 The method for removing sulfur from high-purity ferrous sulfate using a combination of dry and wet methods in this embodiment differs from that in Example 1 in that: after step 400 and before step 500, the following steps are also included: Take 60g of low-sulfur ferric oxide, add the low-sulfur iron powder to a 2.1mol / L hydrochloric acid solution, stir evenly to obtain an iron salt aqueous solution with an iron mass concentration of 3.5%.

[0131] Repeat steps 200 and 300 to obtain solid iron hydroxyoxide.

[0132] The amount of iron hydroxyl oxide in this embodiment was 64.9 g. The impurity elements and their contents in the iron hydroxyl oxide were detected using an infrared carbon-sulfur analyzer and ICP-MS. The impurities in the iron hydroxyl oxide are shown in Table 15 below.

[0133] Table 15. Impurity elements and their contents in ferric hydroxide in this embodiment. Using 60g of ferric hydroxide as raw material, step 400 was repeated to obtain ultra-low sulfur ferric oxide.

[0134] Step 500: Argon gas is introduced into the reduction furnace to purge the air. Then, the obtained ultra-low sulfur ferric oxide is placed in the reduction furnace, hydrogen gas is introduced into the furnace, and the furnace is heated to 400°C to reduce the low-sulfur ferric oxide to iron powder. After the reduction reaction is complete, the hydrogen gas is turned off, argon gas is introduced into the reduction furnace, the temperature is lowered to below 200°C, a vacuum is drawn for 60 minutes, and then the furnace is allowed to cool naturally to room temperature to obtain ultra-low sulfur iron powder.

[0135] The amount of ultra-low sulfur iron powder in this embodiment was 35.6g. The impurity elements and their contents in the ultra-low sulfur iron powder were detected using an infrared carbon-sulfur analyzer and ICP-MS. The impurities in the ultra-low sulfur iron powder are shown in Table 16 below.

[0136] Table 16. Impurity elements and their contents in the ultra-low sulfur iron powder of this embodiment. Example 14 This embodiment describes a method for removing sulfur from high-purity ferrous sulfate using a combination of dry and wet methods, including the following steps: Step 100: Heat the corundum crucible to 1000℃ and introduce oxygen from the bottom of the crucible at a flow rate of 1L / min. Using 150g of ferrous sulfate as raw material, add the ferrous sulfate to the corundum crucible in three batches and heat rapidly. After each batch is added, stir thoroughly before adding the next batch. Maintain the temperature of the corundum crucible at 1000℃ and perform high-temperature oxygen-charged calcination of the ferrous sulfate for 10 minutes.

[0137] After the high-temperature oxygen-charging roasting is completed, the product obtained by high-temperature oxygen-charging roasting is poured into a low-temperature container filled with ice for rapid cooling, stirred evenly, and then subjected to low-temperature quenching for 3 minutes.

[0138] After the low-temperature quenching is completed, the product obtained by low-temperature quenching is poured into 60℃ warm water and stirred and washed for 10 minutes. After washing, the washed product is filtered. The filtered solid material is placed in a 120℃ oven and dried for 60 minutes. Then it is naturally cooled to room temperature. The dried solid material is then sent to a grinder and ground for 3 seconds.

[0139] Then, the steps of rapid heating, low-temperature quenching, and washing were repeated three times to obtain low-sulfur ferric oxide.

[0140] The amount of low-sulfur ferric oxide in this embodiment was 75.5g. The impurity elements and their contents in the low-sulfur ferric oxide were detected using an infrared carbon-sulfur analyzer and ICP-MS. The impurities in the low-sulfur ferric oxide are shown in Table 17 below.

[0141] Table 17. Impurity elements and their contents in the low-sulfur ferric oxide of this embodiment. Step 200: Take 50g of low-sulfur ferric oxide, add the ferric oxide to a hydrochloric acid solution with a concentration of 2.06 mol / L, stir evenly, and obtain an aqueous solution of ferric salt with a mass concentration of 4.76%.

[0142] Step 300: Add 25% ammonia to the ferrous salt aqueous solution to adjust the pH of the ferrous sulfate aqueous solution to 4. Then add 10% hydrogen peroxide to the ferrous sulfate aqueous solution. The amount of hydrogen peroxide used is 1.2 times the theoretical amount. The hydrogen peroxide oxidizes the ferrous sulfate and obtains a solid-liquid mixture containing ferric oxide precipitate. When adding ammonia and hydrogen peroxide to the ferrous sulfate aqueous solution, keep the temperature of the ferrous sulfate aqueous solution at 50°C.

[0143] Step 400: Add 25% ammonia water to the solid-liquid mixture containing ferric hydroxide precipitate, adjust the pH of the ferric hydroxide precipitate solid-liquid mixture to 8, heat to 100℃, age for 1 hour, filter, and wash 4 times with deionized water at a solid-liquid mass ratio of 1:4. After filtration, place the ferric hydroxide in a 105℃ oven and dry for 60 minutes to obtain solid ferric hydroxide.

[0144] The amount of iron hydroxyl oxide in this embodiment was 52.2 g. The impurity elements and their contents in the iron hydroxyl oxide were detected using an infrared carbon-sulfur analyzer and ICP-MS. The impurities in the iron hydroxyl oxide are shown in Table 18 below.

[0145] Table 18. Impurity elements and their contents in ferric hydroxide in this embodiment. Step 500: Heat the corundum crucible to 1000℃ and introduce oxygen from the bottom of the crucible at a flow rate of 1L / min. Using 50g of ferric hydroxide as raw material, add the ferric hydroxide to the corundum crucible in three batches and heat rapidly. After each batch is added, stir thoroughly before adding the next batch. Maintain the temperature of the corundum crucible at 1000℃ and perform high-temperature oxygen-charged calcination of the ferric hydroxide for 10 minutes.

[0146] After the high-temperature oxygen-charging roasting is completed, the product obtained by high-temperature oxygen-charging roasting is poured into a low-temperature container filled with ice for rapid cooling, stirred evenly, and then subjected to low-temperature quenching for 3 minutes.

[0147] After the low-temperature quenching is completed, the product obtained by low-temperature quenching is poured into 60℃ warm water and stirred and washed for 10 minutes. After washing, the washed product is filtered. The filtered solid material is placed in a 120℃ oven and dried for 60 minutes. Then it is naturally cooled to room temperature. The dried solid material is then sent to a grinder and ground for 3 seconds.

[0148] Then, the steps of rapid heating, low-temperature quenching, and washing were repeated three times to obtain ultra-low sulfur ferric oxide.

[0149] Step 600: Argon gas is introduced into the reduction furnace to purge the air. Then, the obtained ultra-low sulfur ferric oxide is placed in the reduction furnace, hydrogen gas is introduced into the furnace, and the furnace is heated to 400°C to reduce the ultra-low sulfur ferric oxide to iron powder. After the reduction reaction is complete, the hydrogen gas is turned off, argon gas is introduced into the reduction furnace, the temperature is lowered to below 200°C, a vacuum is drawn for 60 minutes, and then the furnace is allowed to cool naturally to room temperature to obtain ultra-low sulfur iron powder.

[0150] The amount of ultra-low sulfur iron powder in this embodiment was 30.2g. The impurity elements and their contents in the ultra-low sulfur iron powder were detected using an infrared carbon-sulfur analyzer and ICP-MS. The impurities in the ultra-low sulfur iron powder are shown in Table 19 below.

[0151] Table 19. Impurity elements and their contents in the ultra-low sulfur iron powder of this embodiment. It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0152] Furthermore, it should be noted that the scope of the methods and apparatus in the embodiments of this application is not limited to performing functions in the order shown or discussed, but may also include performing functions substantially simultaneously or in the reverse order, depending on the functions involved. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. In addition, features described with reference to certain examples may be combined in other examples.

[0153] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for removing sulfur from high-purity ferrous sulfate using a combination of dry and wet methods, characterized in that, Includes the following steps: Step 100: Dissolve ferrous sulfate in warm water to obtain an aqueous solution of ferrous sulfate; Step 200: Add alkali to the ferrous sulfate aqueous solution to adjust the pH of the ferrous sulfate aqueous solution and convert the ferrous sulfate into iron hydroxyl compound precipitate; Step 300: Adjust the pH of the solid-liquid mixture of iron hydroxyl compound precipitate to 7-8, heat and age it, then separate the solid and liquid, wash and dry it to obtain iron hydroxyl compound; Step 400: Place the hydroxyl compounds of iron in a container and perform deep desulfurization of the hydroxyl compounds of iron through one or more of the following methods: high-temperature calcination, thermal shock, alternating positive and negative pressure, and dynamic cold quenching, to obtain iron oxides. Step 500: Wash, dry and reduce the iron oxides after deep desulfurization to obtain low-sulfur iron powder.

2. The method for removing sulfur from high-purity ferrous sulfate using a combination of dry and wet methods according to claim 1, characterized in that, After obtaining the iron oxide in step 400, and before washing, drying, and reducing the iron oxide in step 500, the following steps are also included: Iron oxides are dissolved in hydrochloric acid solution to obtain an aqueous solution of iron salts; Repeat steps 200 to 400 at least once to obtain ultra-low sulfur iron oxide.

3. The method for removing sulfur from high-purity ferrous sulfate using a combination of dry and wet methods according to claim 1, characterized in that, In step 200, an alkaline solution is added to the ferrous sulfate aqueous solution to control the pH of the ferrous sulfate aqueous solution to 4-5. Then, hydrogen peroxide is added to the ferrous sulfate aqueous solution to oxidize the ferrous sulfate, thereby obtaining a solid-liquid mixture containing ferric oxide precipitate. The alkaline solution is one or more of the following: ammonia water, ammonium carbonate, ammonium bicarbonate, urea solution, sodium hydroxide, sodium carbonate, sodium bicarbonate, potassium hydroxide, potassium carbonate, and potassium bicarbonate. The amount of hydrogen peroxide used is 1 to 1.2 times the theoretical amount, and the concentration of hydrogen peroxide is 5% to 20%. When adding alkali and hydrogen peroxide to a ferrous sulfate aqueous solution, maintain the temperature of the ferrous sulfate aqueous solution at 40~50℃.

4. The method for removing sulfur from high-purity ferrous sulfate using a combination of dry and wet methods according to claim 1, characterized in that, In step 200, an alkaline solution is added to the ferrous sulfate aqueous solution to control the pH of the ferrous sulfate aqueous solution to 7-8, thereby obtaining a solid-liquid mixture containing ferrous hydroxide precipitate. The alkaline solution is one or more of the following: ammonia water, ammonium carbonate, ammonium bicarbonate, urea solution, sodium hydroxide, sodium carbonate, sodium bicarbonate, potassium hydroxide, potassium carbonate, and potassium bicarbonate. When adding alkali to a ferrous sulfate aqueous solution, maintain the temperature of the ferrous sulfate aqueous solution at 40~50℃.

5. The method for removing sulfur from high-purity ferrous sulfate using a combination of dry and wet methods according to claim 4, characterized in that, After washing the ferrous hydroxide precipitate, the ferrous hydroxide precipitate was dissolved again to obtain a ferrous solution. Add alkali to the ferrous solution and control the pH of the ferrous solution to 7-8 to obtain a solid-liquid mixture containing ferrous hydroxide precipitate. Repeat the steps of dissolving ferrous hydroxide precipitate and reprecipitating with ferrous solution 1 to 5 times.

6. The method for removing sulfur from high-purity ferrous sulfate using a combination of dry and wet methods according to claim 1, characterized in that, In step 100, when ferrous sulfate is dissolved in warm water, the mass concentration of iron is 2-5%. And / or, in step 100, the temperature of the warm water is 40~50℃; And / or, in step 300, after adjusting the pH of the iron hydroxyl compound precipitate solid-liquid mixture, the temperature is raised to 80~100℃; And / or, in step 300, the aging time is 1~3 hours; And / or, in step 300, the precipitate of iron hydroxyl compounds is washed multiple times, and deionized water is added to the precipitate of iron hydroxyl compounds at a solid-liquid mass ratio of 1:4 during each wash.

7. The method for removing sulfur from high-purity ferrous sulfate using a combination of dry and wet methods according to any one of claims 1 to 6, characterized in that, The high-temperature calcination method achieves deep desulfurization of iron hydroxyl compounds through the following steps: The hydroxyl compound of iron is placed in a high-temperature container, and both the hydroxyl compound of iron and the high-temperature container are heated to above 600°C. Maintain the temperature inside the high-temperature container at above 600℃, introduce oxygen into the high-temperature container, stir evenly, and calcine the iron hydroxyl compound at high temperature with oxygen for 30min~120min.

8. The method for removing sulfur from high-purity ferrous sulfate using a combination of dry and wet methods according to any one of claims 1 to 6, characterized in that, The thermal desulfurization method achieves deep desulfurization of iron hydroxyl compounds through the following steps: The high-temperature container is heated to above 1000°C, and then the iron hydroxyl compound is placed in the high-temperature container and heated rapidly. Oxygen is introduced into the high-temperature container, and the mixture is stirred evenly to perform high-temperature oxygen-filled roasting of the iron hydroxyl compound. After the high-temperature oxygen calcination is completed, the product obtained by high-temperature oxygen calcination is placed in a low-temperature container for low-temperature quenching, stirred evenly, and then the product obtained by high-temperature oxygen calcination is rapidly cooled to below 10°C. After the low-temperature quenching is completed, the product obtained by low-temperature quenching is washed, separated from solid and liquid, dried, ground, and then placed in a high-temperature container for rapid heating again. Repeat the process of high-temperature oxygen-charging roasting, low-temperature quenching, and washing 2 to 5 times. The thermal desulfurization process lasts from 30 to 120 minutes and is used for deep desulfurization of hydroxyl compounds in iron.

9. The method for removing sulfur from high-purity ferrous sulfate using a combination of dry and wet methods according to any one of claims 1 to 6, characterized in that, The alternating positive and negative pressure method performs deep desulfurization of iron hydroxyl compounds through the following steps: The iron hydroxyl compound is placed in a container, the heating program is started, and the temperature inside the container is raised to above 1000℃, while at the same time the container is kept under a negative pressure of -100Kpa to -80Kpa by evacuation. Maintain the temperature inside the container above 1000℃, and then introduce oxygen into the container until the container maintains a positive pressure of 80Kpa~100Kpa; Repeat the operation of maintaining negative pressure and maintaining positive pressure 2 to 5 times; The alternating positive and negative pressure method lasts for 30 to 120 minutes to deeply desulfurize the hydroxyl compounds of iron.

10. The method for removing sulfur from high-purity ferrous sulfate using a combination of dry and wet methods according to any one of claims 1 to 6, characterized in that, The dynamic cold quenching method deeply desulfurizes iron hydroxyl compounds through the following steps: A high-temperature container is heated to above 600°C, and then the iron hydroxyl compound is placed in the container and rapidly heated, or the iron hydroxyl compound is placed in a high-temperature container and both the iron hydroxyl compound and the high-temperature container are heated to above 600°C simultaneously, then oxygen is introduced into the high-temperature container, and the mixture is stirred evenly to subject the iron hydroxyl compound to high-temperature oxygen-assisted roasting. During the high-temperature oxygen-charging roasting process, a cooling medium is sprayed onto the surface of the iron hydroxyl compound. The cooling medium is used to quench the iron hydroxyl compound. The cooling medium is water, and the amount of water sprayed is 1-3 mL per 100 g of iron hydroxyl compound. The time interval between spraying the cooling medium onto the surface of the iron hydroxyl compound is 3-5 min. The high-temperature oxygen-assisted roasting lasts for 30 to 120 minutes to deeply desulfurize the hydroxyl compounds of iron.

11. The method for removing sulfur from high-purity ferrous sulfate using a combination of dry and wet methods according to claim 1, characterized in that, Step 500 involves washing, drying, and reducing the iron oxides after deep desulfurization, including the following steps: The iron oxides after deep desulfurization are placed in warm water at 50~70℃, stirred evenly and washed, and the washing product is then separated into solid and liquid. The solid material obtained from solid-liquid separation is placed in a drying oven and dried at 100~200℃ for 30~60 minutes; The dried solid material is placed in a reduction furnace, hydrogen is introduced into the reduction furnace, and the furnace is heated to 400~450℃ to reduce the iron oxide after deep desulfurization into iron powder. After the reaction is complete, inert gas is introduced into the reduction furnace, and after cooling and evacuation, low-sulfur iron powder is obtained.

12. A method for removing sulfur from high-purity ferrous sulfate using a combination of dry and wet methods, characterized in that, Includes the following steps: Step 100: Place high-purity ferrous sulfate in a container and desulfurize it by one or more of the following methods: high-temperature calcination, thermal shock, alternating positive and negative pressure, and dynamic cold quenching, to obtain iron oxide. Step 200: Dissolve the iron oxide in hydrochloric acid solution to obtain an aqueous solution of iron salt; Step 300: Add alkali solution to the iron salt aqueous solution to adjust the pH of the iron salt aqueous solution and convert the iron salt into iron hydroxyl compound precipitate; Step 400: Adjust the pH of the solid-liquid mixture of iron hydroxyl compound precipitate to 7-8, heat and age, then separate the solid and liquid, wash and dry to obtain iron hydroxyl compound; Step 500: Place the hydroxyl compounds of iron in a container and perform deep desulfurization of the hydroxyl compounds of iron through one or more of the following methods: high-temperature calcination, thermal shock, alternating positive and negative pressure, and dynamic cold quenching, to obtain iron oxides. Step 600: Wash, dry and reduce the iron oxides after deep desulfurization to obtain ultra-low sulfur iron powder.

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