Pyrogenic oxidation method for nickel chloride

Abstract

The invention discloses a nickel chloride pyrogenic oxidation method, which comprises the following steps: adding chloridized alkali metal salt and / or chloridized alkaline earth metal salt into nickel chloride to obtain mixed salt, preheating oxygen to 400-600 DEG C, carrying out oxidation reaction on the mixed salt and the preheated oxygen at 600-850 DEG C to obtain crude nickel oxide powder and chlorine, and carrying out water washing, filter pressing and drying on the coarse nickel oxide powder to obtain refined nickel oxide powder. The method disclosed by the invention can effectively avoid caking during high-temperature oxidation of nickel chloride, and is high in reaction speed, short in reaction time, high in yield, high in conversion rate, less in generated three wastes, green and environment-friendly.

Description

Technical Field

[0001] The invention belongs to the technical field of pyrometallurgy, and particularly relates to a method for pyrooxidation of nickel chloride. Background Art

[0002] Nickel-iron alloy is separated by pyrochlorination to obtain high-purity ferric chloride and crude nickel chloride. The crude nickel chloride needs to be further converted into refined nickel oxide with high performance, strong stability, environmental safety and higher product added value. Nickel oxide, as an electrode material for lithium-ion batteries, has a high specific capacity: as a positive electrode precursor, the theoretical capacity of NiO reaches 718mAh / g (actual commercial use is about 300-400mAh / g), which significantly improves the battery energy density. Nickel oxide can be used as a functional material in electronics and information technology, such as in semiconductor devices and sensors. It can also be used in industrial catalysis and environmental governance, such as heavy metal adsorption, photocatalytic degradation, etc. In the field of special materials and emerging applications, it can be used for high-temperature coatings and alloys, biomedicine and biomimetic melting, etc. However, the existing methods for the oxidation of nickel chloride have the following problems:

[0003] 1. During the high temperature oxidation process, nickel chloride will be semi-melted, and only the nickel chloride on the surface will be oxidized, while the nickel chloride inside will be severely agglomerated and unable to continue the reaction. The reasons are (1) Nickel chloride is an ionic crystal, composed of Ni 2 + and Cl- are combined through ionic bonds. At high temperatures, the ions gain enough energy and the vibration intensifies. 2 The thermal kinetic energy of Cl+ and Cl- exceeds the lattice energy (about 2765 kJ / mol), the ionic bonds are partially broken, and partial melting occurs; (2) It may be a pre-melting phenomenon of the material, that is, local structural collapse occurs preferentially at the surface and grain boundaries, forming a disordered liquid area, which appears as a semi-molten state macroscopically.

[0004] 2. Nickel chloride reacts slowly during high-temperature oxidation. The reasons are: (1) agglomeration makes it difficult for oxygen to diffuse to the reaction interface, and most raw materials cannot participate in the reaction; (2) the activation energy of the reaction is high, much higher than that of most metal oxidation reactions, and it is necessary to increase the reaction temperature or extend the reaction time to achieve the required reaction heat.

[0005] In summary, it is necessary to develop a new oxidation method for nickel chloride to solve the above technical problems. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a method for pyrooxidation of nickel chloride, which can improve the high-temperature caking resistance of nickel chloride raw materials, has a fast reaction speed, a short reaction time, a high yield, a high conversion rate and reduces the three wastes.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions.

[0008] A method for pyrooxidation of nickel chloride comprises the following steps:

[0009] (1) adding an inorganic metal chloride to nickel chloride, wherein the inorganic metal chloride is an alkali metal chloride and / or an alkaline earth metal chloride to obtain a mixed salt, preheating oxygen to 400° C. to 600° C., and subjecting the mixed salt to an oxidation reaction with the preheated oxygen at 600° C. to 850° C. to obtain a crude nickel oxide powder and chlorine gas;

[0010] (2) The crude nickel oxide powder is washed with water and filtered to obtain nickel oxide and a filtrate, and the nickel oxide is dried to obtain a refined nickel oxide powder.

[0011] In the above-mentioned method for pyrooxidation of nickel chloride, preferably, in step (1), the alkali metal chloride salt is sodium chloride and / or potassium chloride, and the alkaline earth metal chloride salt is one or more of calcium chloride, magnesium chloride and barium chloride.

[0012] In the above-mentioned method for pyrooxidation of nickel chloride, preferably, in step (1), the mass of the inorganic metal chloride is 2% to 10% of the mass of the nickel chloride.

[0013] In the above-mentioned method of pyrooxidation of nickel chloride, more preferably, in step (1), the mass of the inorganic metal chloride is 4% to 7% of the mass of the nickel chloride.

[0014] In the above-mentioned method of pyrooxidation of nickel chloride, preferably, in step (1), the temperature of the oxidation reaction is 750°C to 850°C.

[0015] In the above-mentioned method for pyrooxidation of nickel chloride, preferably, in step (1), the molar ratio of the oxygen to the nickel chloride is 0.5-0.8:1, the flow rate of the oxygen is controlled at 1 cm / min-10 cm / min, and the oxidation reaction time is 0.5h-4h.

[0016] In the above-mentioned method for pyrooxidation of nickel chloride, preferably, in step (1), the molar ratio of oxygen to nickel chloride is 0.52-0.6:1, the flow rate of oxygen is controlled at 1.5 cm / min-4 cm / min, and the oxidation reaction time is 1.5 h-2.5 h.

[0017] In the above-mentioned method of pyrooxidation of nickel chloride, preferably, in step (1), the oxidation reaction is carried out in a reactor, and the reactor includes one of a fluidized bed reactor, a fixed bed reactor, a tower reactor and a rotary kiln.

[0018] In the above-mentioned method for pyrooxidation of nickel chloride, preferably, in step (1), the crude nickel oxide powder is a powder mixture of nickel oxide, nickel chloride and inorganic metal chloride, the oxygen content in the chlorine gas is 3% to 10%, and the chlorine gas is liquefied and deoxygenated to obtain high-purity chlorine gas, the purity of which is 97% to 99.5%, and the high-purity chlorine gas is used in the chlorination process.

[0019] In the above-mentioned method for pyrooxidation of nickel chloride, preferably, in step (2), the water washing is carried out with soft water, the nickel oxide is high-purity nickel oxide, the purity of the high-purity nickel oxide is above 99.5%, and the Cl in the refined nickel oxide powder is - The content is 0.01% to 0.2%, the oxidation conversion rate of nickel chloride is not less than 95%, the filtrate contains inorganic metal chloride and unreacted nickel chloride, and the filtrate is concentrated and dried to obtain a powder mixture of nickel chloride and inorganic metal chloride, which is returned to the process of preparing the mixed salt to achieve material circulation.

[0020] The principle of the nickel chloride pyrooxidation method of the present invention is shown in formula (1):

[0021]

[0022] Compared with the prior art, the advantages of the present invention are:

[0023] (1) The method of the present invention uses alkali metal chloride and / or alkaline earth metal chloride as a catalyst and dispersant, which can solve the agglomeration problem of nickel chloride during high-temperature oxidation in the prior art. Alkali metal chloride or alkaline earth metal chloride is stable and does not decompose at high temperatures. After adding alkali metal chloride and / or alkaline earth metal chloride as a dispersant, nickel chloride with a high stacking thickness does not agglomerate at high temperatures and is in the form of loose particles, which can allow the internal nickel chloride raw material to fully react with oxygen. Taking sodium chloride as a dispersant as an example, sodium chloride and NiCl2 form a eutectic at a high temperature of >800°C. The liquid phase region expands so that the NiCl2 particles are evenly dispersed in the molten salt. The ionic conductivity of the molten salt promotes electron transfer, which allows Ni 2 + The oxidation reaction proceeds uniformly on a macroscopic scale, avoiding local hot spots that trigger sintering; sodium chloride can also regulate the oxygen transmission channel, and the O2 dissolved in the molten NaCl migrates through the Cl- vacancies to form [Cl - -O2]-complex ions, whose diffusion coefficient (D≈10 -8 m 2 / s) is three orders of magnitude higher than that of gas-phase O2. This mechanism transforms the oxidation reaction from a gas-solid interface reaction to a molten salt phase reaction, which increases the NiO generation rate and limits the grain size to 50-100 nm, and 1-5 μm in the absence of dispersant.

[0024] The alkali metal chloride or alkaline earth metal chloride used in the present invention can also serve as an oxidation reaction catalyst, increasing the reaction rate by over 50%. For example, sodium chloride, acting as a catalyst, forms a molten medium with nickel chloride at high temperatures, accelerating oxygen transport through Cl- vacancies (forming a [NiCl4]2- complex), reducing oxidation activation energy, and refining NiO grains to 20-50nm. Na+ dynamically regulates the oxygen partial pressure, inhibiting overoxidation and releasing lattice strain, reducing the reaction temperature from 900°C to 750°C and reducing energy consumption by over 30%.

[0025] (2) The method of the present invention includes the steps of raw material mixing, oxidation, water washing and drying. The method has a fast reaction speed, a short reaction time, a high yield and a high conversion rate. The obtained crude nickel oxide and refined nickel oxide are in the form of uniform and loose powders, and less three wastes are generated, which is green and environmentally friendly. The purity of the high-purity nickel oxide obtained in the method of the present invention is above 99.5%, the oxidation conversion rate of ferric chloride is not less than 95%, and the Cl in the refined nickel oxide powder is less than 1%. - The content is 0.01% to 0.2%. The chlorine in nickel chloride is converted into chlorine gas. The oxygen content in the chlorine gas is 3% to 10%. After liquefaction and deoxygenation, it can be directly used in the chlorination process.

[0026] (3) The method of the present invention can remove chloride salts by washing with water, and simultaneously remove residual unreacted nickel chloride, thereby improving the purity of the product nickel oxide. The filtrate after washing and filter pressing is concentrated and dried to obtain a powder mixture of nickel chloride and alkali metal chloride salt and / or alkaline earth metal chloride salt. This mixture can be directly returned to the mixing step (the step of preparing the mixed salt) for reuse. Therefore, the amount of dispersant used is small and can be recycled. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 1 is a process flow chart of the method for pyrooxidation of nickel chloride in Examples 1-3 of the present invention. DETAILED DESCRIPTION

[0028] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but the scope of protection of the present invention is not limited thereby. The materials and instruments used in the following examples are all commercially available.

[0029] Example 1

[0030] A method for pyrooxidation of nickel chloride according to the present invention, as follows Figure 1 As shown, the following steps are included:

[0031] (1) Add 0.2 kg of potassium chloride (inorganic metal chloride) to 5 kg of nickel chloride and mix thoroughly to obtain a mixed salt. The mixed salt is added to a fluidized bed reactor and oxygen preheated to 500° C. is introduced into the fluidized bed reactor. The molar ratio of oxygen to nickel chloride is 0.55:1. The oxygen is pure oxygen and the flow rate of the oxygen is controlled to 4 cm / min. The temperature in the fluidized bed reactor is controlled to 800° C. An oxidation reaction is carried out for 1.5 hours to obtain 3.13 kg of crude nickel oxide powder and chlorine. The obtained crude nickel oxide powder is a powder mixture of nickel oxide, nickel chloride and potassium chloride, wherein the content of nickel oxide is 90.5%. The oxygen content in the obtained chlorine is 8%. After liquefaction and deoxygenation of the chlorine, chlorine with a purity of 97.8% is obtained, which can be directly used in the chlorination process.

[0032] (2) Add the crude nickel oxide powder to a stirring tank, add 3 kg of soft water, stir and wash at room temperature for 0.5 h, and filter through a filter press to obtain high-purity nickel oxide and filtrate. The purity of the high-purity nickel oxide is 99.6%. After the high-purity nickel oxide is dried with hot air, 2.83 kg of refined nickel oxide powder is obtained, with a conversion rate of 98.1%. The degree of oxidation of nickel chloride is high. The obtained refined nickel oxide powder is analyzed for residual chlorine content, Cl - The filtrate contains nickel chloride and potassium chloride, which is concentrated and dried to obtain a powder mixture of potassium chloride and nickel chloride, which is reused in the mixed salt preparation process.

[0033] Example 2

[0034] A method for pyrooxidation of nickel chloride according to the present invention, as follows Figure 1 As shown, the following steps are included:

[0035] (1) Add 0.1 kg of potassium chloride and 0.1 kg of magnesium chloride to 5 kg of nickel chloride, mix thoroughly, and obtain a mixed salt. The mixed salt is added to a fluidized bed reactor, and oxygen preheated to 500° C. is introduced into the fluidized bed reactor. The molar ratio of oxygen to nickel chloride is 0.55:1. The oxygen is pure oxygen. The flow rate of oxygen is controlled at 4 cm / min. The temperature in the fluidized bed reactor is controlled at 800° C. An oxidation reaction is carried out for 1.5 hours to obtain 3.12 kg of crude nickel oxide powder and chlorine. The obtained crude nickel oxide powder is a powder mixture of nickel oxide, nickel chloride, potassium chloride, and magnesium chloride, wherein the content of nickel oxide is 90.9%. The oxygen content of chlorine is 7.8%. After liquefaction and deoxygenation of the chlorine, chlorine with a purity of 98.1% is obtained, which can be directly used in the chlorination process.

[0036] (2) Add the crude nickel chloride powder into a stirring tank, add 3 kg of soft water, stir and wash at room temperature for 0.5 h, and filter through a filter press to obtain high-purity nickel oxide and filtrate. The purity of the high-purity nickel oxide is 99.7%. After the high-purity nickel oxide is dried with hot air, 2.83 kg of refined nickel oxide powder is obtained, with a conversion rate of 98.3%. The degree of oxidation of nickel chloride is high. The obtained refined nickel oxide powder is analyzed for residual chlorine content, Cl - The filtrate contains nickel chloride, potassium chloride and magnesium chloride, which is concentrated and dried to obtain a powder mixture of potassium chloride, magnesium chloride and nickel chloride, which is reused in the process of preparing mixed salt.

[0037] Example 3

[0038] A method for pyrooxidation of nickel chloride according to the present invention, as Figure 1 As shown, the following steps are included:

[0039] (1) Add 0.35 kg of barium chloride to 5 kg of nickel chloride and mix thoroughly to obtain a mixed salt. The mixed salt is added to a fluidized bed reactor and oxygen preheated to 500°C is introduced into the fluidized bed reactor. The molar ratio of oxygen to nickel chloride is 0.55:1. The oxygen is pure oxygen and the flow rate of oxygen is controlled at 4 cm / min. The temperature in the fluidized bed reactor is controlled at 800°C. An oxidation reaction is carried out for 1 hour to obtain 3.25 kg of crude nickel oxide powder and chlorine. The obtained crude nickel oxide is a powder mixture of nickel oxide, nickel chloride and barium chloride, wherein the nickel oxide content is 87.8%. The oxygen content of the chlorine is 6.7%. After liquefaction and deoxygenation of the chlorine, chlorine with a purity of 98.5% is obtained and can be directly used in the chlorination process.

[0040] (2) Add the crude nickel chloride powder into a stirring tank, add 3 kg of soft water, stir and wash at room temperature for 0.5 h, and filter through a filter press to obtain high-purity nickel oxide and filtrate. The purity of the high-purity nickel oxide is 99.9%. After the high-purity nickel oxide is dried with hot air, 2.90 kg of refined nickel oxide powder is obtained, with a conversion rate of 99.1%. The degree of oxidation of nickel chloride is high. The obtained refined nickel oxide powder is analyzed for residual chlorine content, Cl - The filtrate contains nickel chloride and barium chloride, which is concentrated and dried to obtain a powder mixture of barium chloride and nickel chloride, which is reused in the mixed salt preparation process.

[0041] Comparative Example 1

[0042] A method for pyrooxidation of nickel chloride comprises the following steps:

[0043] (1) Add 0.6 kg of potassium chloride to 5 kg of nickel chloride and mix thoroughly to obtain a mixed salt. The mixed salt is added to a fluidized bed reactor and oxygen preheated to 500°C is introduced into the fluidized bed reactor. The molar ratio of oxygen to nickel chloride is 0.55:1. The oxygen is pure oxygen and the flow rate of oxygen is controlled at 4 cm / min. The temperature in the fluidized bed reactor is controlled at 800°C. An oxidation reaction is carried out for 1 hour to obtain 3.63 kg of crude nickel oxide powder containing a small amount of lumps and 2.92 kg of chlorine. The obtained crude nickel oxide is a mixture of nickel oxide, nickel chloride and calcium chloride, wherein the content of nickel oxide is 73.8%. The oxygen content of the chlorine is 8.9%. After liquefaction and deoxygenation of the chlorine, chlorine with a purity of 96.8% is obtained and can be directly used in the chlorination process.

[0044] (2) Add the crude nickel chloride into a stirring tank, add 3 kg of soft water, stir and wash at room temperature for 0.5 h, and filter through a filter press to obtain high-purity nickel oxide and filtrate. The purity of the high-purity nickel oxide is 96.9%. After the high-purity nickel oxide is dried with hot air, 2.68 kg of refined nickel oxide powder containing a small amount of lumps is obtained. The conversion rate is 93.0%, and the oxidation degree of nickel chloride is general. The obtained refined nickel oxide is analyzed for residual chlorine content, Cl - The filtrate contains nickel chloride and potassium chloride, which is concentrated and dried to obtain a powder mixture of potassium chloride and nickel chloride, which is reused in the mixed salt preparation process.

[0045] Comparative Example 2

[0046] A method for pyrooxidation of nickel chloride comprises the following steps:

[0047] Using silicon dioxide as a dispersant, add 0.2 kg of silicon dioxide to 5 kg of nickel chloride, mix thoroughly in a mixer, and add the resulting mixture to a fluidized bed reactor. Oxygen preheated to 500°C is introduced into the fluidized bed reactor. The molar ratio of oxygen to nickel chloride is 0.55:1. The oxygen is pure oxygen. The flow rate of oxygen is controlled to 4 cm / min. The temperature in the fluidized bed reactor is controlled to 800°C. The oxidation reaction is carried out for 1.5 hours to obtain 3.23 kg of crude nickel oxide and chlorine. The obtained crude nickel oxide is a loose powder, 20% of which is deposited on the surface. The crude nickel oxide is a mixture of nickel oxide, nickel chloride and silicon dioxide, wherein the content of nickel oxide is 83.3% and the conversion rate is 93.2%. However, silicon dioxide and nickel oxide are both insoluble in water, and the particle size distribution range partially overlaps, making it difficult to separate by screening. The residual chlorine content of the product is analyzed and tested. The Cl in the obtained crude nickel chloride is 20%. - The oxygen content of chlorine is 7.9%. After liquefaction and deoxygenation, the chlorine with a purity of 96.5% is obtained and can be directly used in the chlorination process.

[0048] Table 1 shows the reaction conditions and results for Examples 1-3 and Comparative Examples 1-2. As shown in Table 1, the addition of an inorganic metal chloride salt as a dispersant and catalyst yields a loose powder with uniform particle size. However, the excessive amount of dispersant in Comparative Example 1 lowers the melting point of the mixed salt, causing particle aggregation, reducing dispersion effectiveness, and affecting reaction uniformity. In Comparative Example 2, silica, an inert dispersant, exhibits a strong dispersing effect, but it makes it difficult to obtain high-purity nickel oxide through water washing.

[0049] Table 1 Reaction conditions and effects of Examples 1-3 and Comparative Examples 1-2

[0050]

[0051] The above description is only a preferred embodiment of the present invention and does not constitute any formal limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can, without departing from the spirit and technical solution of the present invention, use the methods and technical contents disclosed above to make many possible changes and modifications to the technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention, still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for pyrooxidation of nickel chloride, characterized in that: The following steps are involved: (1) adding an inorganic metal chloride to nickel chloride, wherein the inorganic metal chloride is an alkali metal chloride and / or an alkaline earth metal chloride to obtain a mixed salt, preheating oxygen to 400° C. to 600° C., and subjecting the mixed salt to an oxidation reaction with the preheated oxygen at 600° C. to 850° C. to obtain a crude nickel oxide powder and chlorine gas; (2) The crude nickel oxide powder is washed with water and filtered to obtain nickel oxide and a filtrate, and the nickel oxide is dried to obtain a refined nickel oxide powder.

2. The method for pyrooxidation of nickel chloride according to claim 1, wherein In step (1), the alkali metal chloride salt is sodium chloride and / or potassium chloride, and the alkaline earth metal chloride salt is one or more of calcium chloride, magnesium chloride and barium chloride.

3. The method for pyrooxidation of nickel chloride according to claim 1, wherein In step (1), the mass of the inorganic metal chloride is 2% to 10% of the mass of the nickel chloride.

4. The method for pyrooxidation of nickel chloride according to claim 3, wherein In step (1), the mass of the inorganic metal chloride is 4% to 7% of the mass of the nickel chloride.

5. The method for pyrooxidation of nickel chloride according to any one of claims 1 to 4, characterized in that: In step (1), the temperature of the oxidation reaction is 750°C to 850°C.

6. The method for pyrooxidation of nickel chloride according to any one of claims 1 to 4, characterized in that: In step (1), the molar ratio of the oxygen to the nickel chloride is 0.5 to 0.8:1, the flow rate of the oxygen is controlled at 1 cm / min to 10 cm / min, and the oxidation reaction time is 0.5 h to 4 h.

7. The method for pyrooxidation of nickel chloride according to claim 6, characterized in that: In step (1), the molar ratio of the oxygen to the nickel chloride is 0.52 to 0.6:1, the flow rate of the oxygen is controlled at 1.5 cm / min to 4 cm / min, and the oxidation reaction time is 1.5 h to 2.5 h.

8. The method for pyrooxidation of nickel chloride according to any one of claims 1 to 4, characterized in that: In step (1), the oxidation reaction is carried out in a reactor, which includes one of a fluidized bed reactor, a fixed bed reactor, a tower reactor and a rotary kiln.

9. The method for pyrooxidation of nickel chloride according to any one of claims 1 to 4, characterized in that: In step (1), the crude nickel oxide powder is a powder mixture of nickel oxide, nickel chloride and inorganic metal chloride, the oxygen content in the chlorine is 3% to 10%, and the chlorine is liquefied and deoxygenated to obtain high-purity chlorine, the purity of which is 97% to 99.5%, and the high-purity chlorine is used in the chlorination process.

10. The method for pyrooxidation of nickel chloride according to any one of claims 1 to 4, characterized in that: In step (2), the water washing is performed with soft water, the nickel oxide is high-purity nickel oxide, the purity of the high-purity nickel oxide is above 99.5%, and the Cl in the refined nickel oxide powder is - The content is 0.01% to 0.2%, the oxidation conversion rate of nickel chloride is not less than 95%, the filtrate contains inorganic metal chloride and unreacted nickel chloride, and the filtrate is concentrated and dried to obtain a powder mixture of nickel chloride and inorganic metal chloride, which is returned to the process of preparing the mixed salt to achieve material circulation.

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