Method for low-temperature solid-phase oxidation of ferric chloride

Abstract

The invention discloses a ferric chloride low-temperature solid-phase oxidation method which comprises the following steps: carrying out microwave pretreatment on a ferric chloride solid raw material, and heating the ferric chloride solid raw material to 80-120 DEG C to obtain preheated and activated ferric chloride; oxygen is preheated to 250-300 DEG C and then subjected to a low-temperature oxidation reaction with preheated and activated ferric chloride, the temperature of the low-temperature oxidation reaction is 200-320 DEG C, crude iron oxide and chlorine are obtained, and the crude iron oxide is a mixture of mica iron oxide and ferric chloride; and heating and separating ferric chloride in the crude iron oxide to obtain a mica iron oxide product. The ferric chloride raw material is preheated and activated through the microwave pretreatment technology, the activation energy of the oxidation reaction is reduced, and then the temperature range required by raw material preheating is reduced, so that the solid-phase oxidation reaction can be carried out at a relatively low temperature; therefore, the heating energy consumption is greatly reduced on the premise of ensuring high product yield and purity, the generated three wastes are few, and the method is green and environment-friendly.

Description

Technical Field

[0001] The invention belongs to the technical field of iron oxide preparation, and particularly relates to a method for low-temperature solid-phase oxidation of ferric chloride. Background Art

[0002] Iron oxide is a compound formed by the combination of iron and oxygen. It primarily includes ferrous oxide, ferric oxide, and ferric oxide. Iron oxide is widely used in pigments, magnetic materials, catalysts and energy, environmental protection and pollution control, biology, and medicine. Iron oxide can be derived from natural ores such as hematite (Fe2O3) and magnetite (Fe3O4). It can also be synthesized artificially through processes such as wet precipitation (e.g., reacting ferrous sulfate with alkali) and thermal decomposition (calcining ferrous sulfate or ferric nitrate). Flake iron oxide is a regular hexagonal single crystal composed primarily of α-Fe2O3. Because its flake structure resembles mica, it is called mica iron oxide. Flake iron oxide is a key raw material for high-end anti-rust paints for vehicles, bridges, and other applications, earning it the reputation of "armor paint." Numerous existing iron oxide production processes exist, but each has its own drawbacks. For example, traditional pyrooxidation methods cannot produce micaceous iron oxide that meets industry standards. Pyrooxidation with ferric chloride typically involves high-temperature vapor-phase oxidation at 600°C to 800°C, resulting in black particles with cubic or polyhedral structures. The target flaky micaceous iron oxide content is less than 10%. Direct solid-phase pyrooxidation with ferric chloride at 200°C to 320°C results in a slow reaction rate due to the high activation energy and low reaction temperature, typically requiring 6 to 8 hours for complete reaction. α-Iron oxide produced by existing solid-phase methods is typically powdery or spherical, rarely in the form of flakes. Liquid-phase methods, such as the traditional hydrothermal method, require large amounts of solvents to produce iron oxide, generating acidic wastewater (pH approximately 2) for post-reaction treatment, and consuming at least 5000 kWh of electricity per ton of iron oxide produced. Vapor-phase methods are costly, with chemical vapor deposition equipment requiring investments exceeding 2 million yuan, and reaction temperatures exceeding 600°C resulting in excessive energy consumption. Therefore, it is of great significance to develop a mica iron oxide preparation process with low energy consumption, high efficiency, green environmental protection and low cost. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for low-temperature solid-phase oxidation of ferric chloride with high efficiency, low energy consumption, low cost and environmental protection in view of the deficiencies in the prior art.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0005] A method for low-temperature solid-phase oxidation of ferric chloride comprises the following steps:

[0006] (1) pre-treating the ferric chloride solid raw material with microwaves to heat the ferric chloride solid raw material to 80° C. to 120° C. to obtain preheated activated ferric chloride;

[0007] (2) preheating oxygen to 250° C. to 300° C. and then performing a low-temperature oxidation reaction with the preheated activated ferric chloride, wherein the temperature of the low-temperature oxidation reaction is 200° C. to 320° C. to obtain crude iron oxide and chlorine, wherein the crude iron oxide is a mixture of mica iron oxide and ferric chloride;

[0008] (3) raising the temperature to separate the ferric chloride in the crude ferric oxide to obtain a mica ferric oxide product.

[0009] In the above-mentioned method of low-temperature solid-phase oxidation of ferric chloride, preferably, in step (1), the power of the microwave in the microwave pretreatment is 10kW to 30kW, and the duration of the microwave pretreatment is 10s to 120s.

[0010] In the above-mentioned method of low-temperature solid-phase oxidation of ferric chloride, preferably, in step (2), the temperature of the low-temperature oxidation reaction is 260°C to 310°C.

[0011] In the above-mentioned method of low-temperature solid-phase oxidation of ferric chloride, preferably, in step (2), the low-temperature oxidation reaction time is 1 hour to 3 hours.

[0012] In the above-mentioned method of low-temperature solid-phase oxidation of ferric chloride, preferably, in step (2), the oxygen is pure oxygen, and the molar ratio of the oxygen to the preheated activated ferric chloride is 0.6-0.75:1.

[0013] In the above-mentioned method of low-temperature solid-phase oxidation of ferric chloride, preferably, in step (2), the low-temperature oxidation reaction is carried out in a fluidized bed reactor, and the flow rate of the oxygen introduced into the fluidized bed reactor is controlled to be 0.1 cm / min to 0.4 cm / min.

[0014] In the above-mentioned method of low-temperature solid-phase oxidation of ferric chloride, preferably, in step (3), the temperature-raising separation is to heat the crude ferric oxide to 350°C to 400°C and maintain it for 0.2h to 1h, so that the residual ferric chloride solid is converted into gaseous ferric chloride and separated from the ferric oxide.

[0015] In the above-mentioned method of low-temperature solid-phase oxidation of ferric chloride, preferably, the gaseous ferric chloride is recycled to the low-temperature oxidation reaction step and provides heat for the low-temperature oxidation reaction.

[0016] In the above-mentioned method of low-temperature solid-phase oxidation of ferric chloride, preferably, in step (2), the oxygen content in the chlorine gas is 0-5%, and the chlorine gas is purified to obtain high-purity chlorine gas, the purity of which is 98%-99.5%, and the high-purity chlorine gas is used in the chlorination process.

[0017] In the above-mentioned method of low-temperature solid-phase oxidation of ferric chloride, preferably, in step (2), the mass percentage of iron oxide in the crude iron oxide is 80% to 95%; in step (3), the yield of the mica iron oxide product is 90% to 98%, and the purity of the mica iron oxide product is 99.00% to 99.99%.

[0018] The effects and principles of microwave pretreatment adopted in the present invention are as follows:

[0019] (1) Preheating, polarization effect: Fe is induced by microwaves 3+ -Cl - The ion pairs oscillate at high frequency, with an instantaneous heating rate of 50°C / s, to preheat the ferric chloride raw material.

[0020] (2) Molecular-scale activation mechanism

[0021] (2.1) Bond energy reorganization effect: The microwave electric field induces the dipole oscillation of the Fe-Cl bond, causing Cl - The diffusion coefficient is increased by 5 times, accelerating Cl - ion migration;

[0022] (2.2) Oxygen defect engineering: Microwave non-thermal effect promotes Fe 3+ The octahedral sites generate oxygen vacancies, which become active sites for subsequent oxidation reactions.

[0023] (2.3) Lattice prestrain regulation: Microwave thermal shock (heating rate > 50℃ / s) forms compressive strain in FeCl3 crystals. The strain energy stored in microwave pretreatment can provide a driving force for the solid-phase oxidation reaction.

[0024] (3) Decreased activation energy

[0025] The activation energy of oxidation reaction in traditional process is Ea=150kJ / mol; after microwave pretreatment, the activation energy of oxidation reaction Ea is reduced to 98kJ / mol, and the slope of Arrhenius curve is reduced by 34%.

[0026] (4) Constructing oxygen diffusion channels

[0027] Microwaves induce the formation of nanoscale pores on the ferric chloride raw material. The BET detection shows that the pore diameter is 3nm to 5nm, shortening the oxygen diffusion path to 1 / 3 of the original raw material; in situ Raman spectroscopy shows that compared with the original ferric chloride raw material, the adsorption of O2 by ferric chloride after microwave pretreatment is increased by 2.7 times. Both the shortening of the oxygen diffusion path and the increase in the oxygen adsorption amount by the ferric chloride raw material can effectively increase the rate of the solid-phase oxidation reaction.

[0028] The reaction principle of the low-temperature solid-phase oxidation of ferric chloride of the present invention is as follows:

[0029] 2FeCl3 + 1.5O2 → Fe2O3 + 3Cl2↑ (1)

[0030] By controlling the ratio of oxygen to preheated activated ferric chloride solid, the ferric chloride reacts completely and the content of unreacted ferric chloride in the product is reduced as much as possible. The low-temperature oxidation reaction is carried out in a fluidized bed reactor. By controlling the flow rate of oxygen, the product ferric oxide can be prevented from violently colliding and becoming powdery or spherical.

[0031] Compared with the prior art, the advantages of the present invention are:

[0032] (1) The method of low-temperature solid-phase oxidation of ferric chloride of the present invention applies microwave technology to the pyrometallurgical oxidation of ferric chloride, and the oxidation process of ferric chloride is completed by microwave pretreatment and low-temperature solid-phase oxidation in collaboration. Compared with the traditional heating method, the microwave pretreatment adopted in the present invention not only has a fast heating speed, high efficiency, uniform heating, precise temperature control, and low energy consumption, but also can catalytically activate the ferric chloride raw material. Under the action of microwaves, the atoms and molecules of the reaction center are vibrated, the reaction activation energy is reduced, and thus the activation temperature is reduced. The present invention preheats and activates the ferric chloride raw material by microwave pretreatment technology, reduces the activation energy of the oxidation reaction, and then reduces the reaction temperature of the raw material, so that the solid-phase oxidation reaction can be carried out at a relatively low temperature, thereby achieving a significant reduction in heating energy consumption under the premise of ensuring higher product yield and purity.

[0033] (2) The method of the present invention can improve the reaction speed of the overall process through the synergistic effect of microwave pretreatment and low-temperature oxidation, reduce the residence time of the material in the reactor, and realize a low-temperature (<320°C) rapid continuous production process. In addition, the target product mica iron oxide and unreacted ferric chloride solid are separated by heating, and the obtained gaseous ferric chloride can be directly reused in the oxidation reaction process, while providing heat for the oxidation process. The overall energy consumption is low, the product yield is high (90% to 98%), the purity is high (99.00% to 99.99%), and the three wastes are less, which is green and environmentally friendly.

[0034] (3) The method of the present invention can prepare mica iron oxide that meets the industry standard (HG / T3006-2012 Micaceous Iron Oxide Pigment) by controlling key process conditions such as the microwave pretreatment temperature of the ferric chloride solid raw material to 80°C to 120°C and the temperature of the low-temperature oxidation reaction to 200°C to 320°C, that is, it meets the technical requirements of the content of flaky particles ≥50%, the mass fraction of iron ≥85%, and the mass fraction of water-soluble matter ≤0.5%. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The process flow chart of the method for low-temperature solid-phase oxidation of ferric chloride in Example 1 of the present invention is shown.

[0036] Figure 2 This is a SEM image of iron oxide x5000 prepared by the method of low-temperature solid-phase oxidation of ferric chloride in Example 1 of the present invention.

[0037] Figure 3 This is a SEM image of iron oxide x10000 prepared by the method of low-temperature solid-phase oxidation of ferric chloride in Example 1 of the present invention. DETAILED DESCRIPTION

[0038] The present invention will be further described below in conjunction with the accompanying drawings and specific preferred embodiments, but the scope of protection of the present invention is not limited thereby.

[0039] Example 1

[0040] A method for low-temperature solid-phase oxidation of ferric chloride of the present invention, as Figure 1 As shown, the following steps are included:

[0041] (1) 2 kg of room temperature ferric chloride solid raw material is fed into the feeding system, and the raw material particles are first pretreated with microwaves using an industrial microwave device. The microwave power is 20 kW, and the microwave pretreatment time is 50 seconds. The ferric chloride solid raw material is quickly heated to 100° C., and preheating, molecular activation, and oxygen diffusion channel construction are completed to obtain preheated and activated ferric chloride (solid);

[0042] (2) After preheating oxygen to 250°C, a low-temperature oxidation reaction is carried out with preheated and activated ferric chloride in a fluidized bed reactor. The oxygen is pure oxygen, and the molar ratio of oxygen to preheated and activated ferric chloride solid is 0.73:1. The flow rate of oxygen into the fluidized bed reactor is controlled to 0.3 cm / min, and the temperature in the fluidized bed reactor chamber is controlled to maintain the temperature of the low-temperature oxidation reaction at 280°C for 1.5 hours. After the low-temperature oxidation reaction is completed, 1.03 kg of crude iron oxide and chlorine are obtained through a cyclone separator. The crude iron oxide is a mixture of flaky iron oxide and ferric chloride, wherein the mass percentage of iron oxide is 91.2%. The chlorine contains a small amount of residual oxygen, with an oxygen content of about 4.1%. After purification, high-purity chlorine is obtained. The purity of the high-purity chlorine is 99.1%, which can be directly used in the chlorination process.

[0043] (3) The crude iron oxide was heated to 380°C and maintained for 0.5 h to volatilize the residual ferric chloride solid into gaseous ferric chloride, which was separated from the iron oxide to obtain mica iron oxide product with a yield of 96.1%. The purity of the mica iron oxide was 99.7% after testing. SEM images at magnifications of 5000 times and 10000 times were obtained under a scanning electron microscope. The results are as follows: Figure 2 、 Figure 3 As shown in the figure, it can be seen that the mica iron oxide prepared in this embodiment is in the form of thin flakes. Among them, the gaseous ferric chloride is recycled to the low-temperature oxidation reaction process to provide heat for the low-temperature oxidation reaction.

[0044] Example 2

[0045] A method for low-temperature solid-phase oxidation of ferric chloride of the present invention has the following main steps, which are substantially the same as those in Example 1, except that the microwave time is shortened and the preheating temperature of the ferric chloride solid is lowered. The specific steps are as follows:

[0046] (1) 2 kg of room temperature ferric chloride solid raw material is fed into the feeding system, and the raw material particles are first pretreated with microwaves using an industrial microwave device. The microwave power is 20 kW, and the microwave pretreatment time is 40 seconds. The ferric chloride solid raw material is quickly heated to 80° C., and preheating, molecular activation, and oxygen diffusion channel construction are completed to obtain preheated and activated ferric chloride (solid);

[0047] (2) The oxygen is preheated to 250°C and then subjected to a low-temperature oxidation reaction with the preheated activated ferric chloride in a fluidized bed reactor. The oxygen is pure oxygen, and the molar ratio of oxygen to the preheated activated ferric chloride is 0.73:1. The flow rate of oxygen into the fluidized bed reactor is controlled to 0.3 cm / min, and the temperature in the fluidized bed reactor chamber is controlled to maintain the low-temperature oxidation temperature at 280°C for 1.5 hours. After the low-temperature oxidation reaction is completed, 1.05 kg of crude iron oxide and chlorine are obtained through a cyclone separator. The crude iron oxide is a mixture of flaky iron oxide and ferric chloride, wherein the mass percentage of iron oxide is 88.6%. The chlorine contains a small amount of residual oxygen, the content of which is about 4.5%. After purification, high-purity chlorine is obtained. The purity of the high-purity chlorine is 99.0%, which can be directly used in the chlorination process.

[0048] (3) The crude iron oxide is heated to 380°C and maintained for 0.5 h to volatilize the residual ferric chloride solid into vapor-phase ferric chloride, which is separated from the iron oxide to obtain a mica iron oxide product with a yield of 94.9%. The content of the mica iron oxide is determined to be 99.6%. The vapor-phase ferric chloride is recycled to the low-temperature oxidation reaction step to provide heat for the low-temperature oxidation reaction.

[0049] Example 3

[0050] A method for low-temperature solid-phase oxidation of ferric chloride according to the present invention has the following main steps, which are substantially the same as those in Example 1, except that the temperature of the oxidation reaction is lowered. The specific steps are as follows:

[0051] (1) 2 kg of room temperature ferric chloride solid raw material is fed into the feeding system, and the raw material particles are first pretreated with microwaves using an industrial microwave device. The microwave power is 20 kW, and the microwave pretreatment time is 50 seconds. The ferric chloride solid raw material is quickly heated to 100° C., and preheating, molecular activation, and oxygen diffusion channel construction are completed to obtain preheated and activated ferric chloride (solid);

[0052] (2) The oxygen is preheated to 250°C and then subjected to a low-temperature oxidation reaction with the preheated activated ferric chloride in a fluidized bed reactor. The oxygen is pure oxygen, and the molar ratio of oxygen to the preheated activated ferric chloride is 0.73:1. The flow rate of oxygen into the fluidized bed reactor is controlled to 0.3 cm / min, and the temperature in the fluidized bed reactor chamber is controlled to maintain the temperature of the low-temperature oxidation reaction at 250°C for 1.5 hours. After the low-temperature oxidation reaction is completed, 1.06 kg of crude iron oxide and chlorine are obtained through a cyclone separator. The crude iron oxide is a mixture of flaky iron oxide and ferric chloride, wherein the mass percentage of iron oxide is 85.7%. The chlorine contains a small amount of residual oxygen, the content of which is about 4.7%. After purification, high-purity chlorine is obtained. The purity of the high-purity chlorine is 98.8%, which can be directly used in the chlorination process.

[0053] (3) The crude iron oxide is heated to 380°C and maintained for 0.5 h to volatilize the residual ferric chloride solid into vaporous ferric chloride, which is separated from the iron oxide to obtain a mica iron oxide product with a yield of 93.2%. The content of the mica iron oxide is determined to be 99.6%. The vaporous ferric chloride is recycled to the low-temperature oxidation reaction step to provide heat for the low-temperature oxidation reaction.

[0054] Comparative Example 1

[0055] A method for solid-phase oxidation of ferric chloride, the main steps of which are basically the same as those of Example 1, except that conventional electric heating pretreatment is used instead of microwave pretreatment. The specific steps are as follows:

[0056] (1) 2 kg of room temperature ferric chloride solid raw material is fed into the feeding system, and the raw material particles are first heated through a tunnel-type electric heating furnace to raise the temperature of the ferric chloride solid to 100° C. to obtain preheated ferric chloride solid;

[0057] (2) The oxygen is preheated to 250°C and then subjected to a low-temperature oxidation reaction with the preheated ferric chloride in a fluidized bed reactor. The oxygen is pure oxygen, and the molar ratio of oxygen to preheated activated ferric chloride is 0.73:1. The flow rate of oxygen into the fluidized bed reactor is controlled to 0.3 cm / min, and the temperature in the fluidized bed reactor chamber is controlled to maintain the temperature of the low-temperature oxidation reaction at 280°C for 1.5 hours. After the low-temperature oxidation reaction is completed, it passes through a cyclone separator to obtain 1.11 kg of crude iron oxide and chlorine. The crude iron oxide is a mixture of flaky iron oxide and ferric chloride, wherein the mass percentage of iron oxide is 78.3%. The chlorine contains a small amount of residual oxygen, the content of which is about 4.6%. After purification, high-purity chlorine is obtained. The purity of the high-purity chlorine is 98.7%, which can be directly used in the chlorination process.

[0058] (3) The crude iron oxide is heated to 380°C for 0.5 h to volatilize the residual ferric chloride solid into vapor-phase ferric chloride, which is separated from the iron oxide to obtain a mica iron oxide product with a yield of 88.8%. The content of the mica iron oxide is determined to be 98.9%. The vapor-phase ferric chloride is recycled to the low-temperature oxidation reaction step to provide heat for the low-temperature oxidation reaction.

[0059] Comparative Example 2

[0060] A method for solid-phase oxidation of ferric chloride, the main steps of which are substantially the same as those of Example 1, except that the temperature of the low-temperature oxidation reaction in step (2) is 350° C. The specific steps are as follows:

[0061] (1) 2 kg of room temperature ferric chloride solid raw material is fed into the feeding system, and the raw material particles are first pretreated with microwaves using an industrial microwave device. The microwave power is 20 kW, and the microwave pretreatment time is 50 seconds. The ferric chloride solid raw material is quickly heated to 100° C., and preheating, molecular activation, and oxygen diffusion channel construction are completed to obtain preheated and activated ferric chloride solid;

[0062] (2) The oxygen is preheated to 250°C and then subjected to a low-temperature oxidation reaction with the preheated activated ferric chloride in a fluidized bed reactor. The oxygen is pure oxygen, and the molar ratio of oxygen to the preheated activated ferric chloride is 0.73:1. The flow rate of oxygen into the fluidized bed reactor is controlled to 0.3 cm / min, and the temperature in the fluidized bed reactor chamber is controlled to maintain the temperature of the low-temperature oxidation reaction at 350°C for 1.5 hours. After the low-temperature oxidation reaction is completed, 0.31 kg of crude iron oxide and chlorine are obtained through a cyclone separator. The crude iron oxide is a mixture of flaky iron oxide and ferric chloride, wherein the mass percentage of iron oxide is 88.7%. The chlorine contains a small amount of residual oxygen, with an oxygen content of about 4.7%. After purification, high-purity chlorine is obtained. The purity of the high-purity chlorine is 98.8%, which can be directly used in the chlorination process.

[0063] (3) The crude iron oxide was heated to 380°C and maintained for 0.5 h to volatilize the residual ferric chloride solid into gaseous ferric chloride, which was separated from the iron oxide to obtain mica iron oxide product with a yield of 27.9%. The content of mica iron oxide was 98.3% after testing.

[0064] The iron oxide prepared in this comparative example has low yield and low purity.

[0065] Table 1 Reaction conditions and corresponding reaction conditions of Examples 1-3 and Comparative Examples 1-2

[0066]

[0067]

[0068] As shown in Table 1, microwave pretreatment in the present invention can effectively improve the reactivity of the solid raw material of ferric chloride. In contrast, Comparative Example 1 does not use microwave activation. The ferric chloride raw material is preheated to the same temperature as Example 1 by electric heating. Its reactivity is low, and the conversion rate of the oxidation reaction of the ferric chloride raw material is significantly lower than that of Example 1. In addition, the temperature of microwave pretreatment and the temperature of solid-phase oxidation reaction have a greater influence on the yield of mica iron oxide. If the microwave pretreatment temperature is too low, the preheating activation effect will be reduced, thereby affecting the conversion rate of the solid-phase oxidation reaction and reducing the product yield. If the microwave pretreatment temperature exceeds 120 ° C, the microwave time required is long, which will lead to local overheating and cause some ferric chloride raw materials to volatilize. As shown in Comparative Example 2, if the solid-phase oxidation temperature is too low, the oxidation reaction will be insufficient and the product yield will be reduced. If the temperature of the solid-phase oxidation reaction is too high, a large amount of ferric chloride will be gasified, resulting in a reduction in the output of the product mica iron oxide of a single reaction and low production efficiency.

[0069] The overall process of the method of the present invention has significant energy consumption and economic advantages compared with the existing traditional process. The comprehensive energy consumption comparison is as follows:

[0070] Traditional resistance furnace heating solid-phase oxidation usually requires a high temperature reaction of 300°C for 6 to 8 hours. The average energy consumption is about 2.8 kWh / kg per kilogram of ferric chloride raw material. Using the microwave pretreatment + low-temperature oxidation of the present invention, taking Example 1 as an example, microwave pretreatment at 20 kW for 50 seconds and oxidation reaction at 280°C for 1.5 hours, the average energy consumption is about 1.4 kWh / kg, which can save 50% energy.

[0071] In terms of equipment operating efficiency, the microwave-fluidized bed coupling system of the present invention has a continuous processing capacity of 500 kg / h, a particle size qualification rate of >99.3%, and a microwave feed system efficiency of >85%. In comparison, the system efficiency of traditional equipment is ≤60%.

[0072] Although the present invention is disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can, without departing from the spirit and technical solutions of the present invention, use the methods and technical contents disclosed above to make many possible changes and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments with equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments based on the technical spirit of the present invention without departing from the content of the technical solutions of the present invention, shall still fall within the scope of protection of the technical solutions of the present invention.

Claims

1. A method for low-temperature solid-phase oxidation of ferric chloride, characterized in that: The following steps are involved: (1) pre-treating the ferric chloride solid raw material with microwaves to heat the ferric chloride solid raw material to 80° C. to 120° C. to obtain preheated activated ferric chloride; (2) preheating oxygen to 250° C. to 300° C. and then performing a low-temperature oxidation reaction with the preheated activated ferric chloride, wherein the temperature of the low-temperature oxidation reaction is 200° C. to 320° C. to obtain crude iron oxide and chlorine, wherein the crude iron oxide is a mixture of mica iron oxide and ferric chloride; (3) raising the temperature to separate the ferric chloride in the crude ferric oxide to obtain a mica ferric oxide product.

2. The method for ferric chloride low-temperature solid-phase oxidation according to claim 1, wherein In step (1), the power of the microwave in the microwave pretreatment is 10kW to 30kW, and the duration of the microwave pretreatment is 10s to 120s.

3. The method for ferric chloride low temperature solid phase oxidation according to claim 1, wherein In step (2), the temperature of the low-temperature oxidation reaction is 260°C to 310°C.

4. The method for ferric chloride low-temperature solid-phase oxidation according to claim 1, wherein In step (2), the low-temperature oxidation reaction time is 1 h to 3 h.

5. The method for ferric chloride low temperature solid phase oxidation according to claim 1, wherein In step (2), the oxygen is pure oxygen, and the molar ratio of the oxygen to the preheated activated ferric chloride is 0.6 to 0.75:

1.

6. The method for ferric chloride low-temperature solid-phase oxidation according to claim 1, wherein In step (2), the low-temperature oxidation reaction is carried out in a fluidized bed reactor, and the flow rate of the oxygen introduced into the fluidized bed reactor is controlled to be 0.1 cm / min to 0.4 cm / min.

7. The method for low-temperature solid-phase oxidation of ferric chloride according to claim 1, wherein In step (3), the temperature separation is to heat the crude iron oxide to 350° C. to 400° C. and maintain the temperature for 0.2 h to 1 h, so that the residual ferric chloride solid is converted into gaseous ferric chloride and separated from the iron oxide.

8. The method for low-temperature solid-phase oxidation of ferric chloride according to claim 7, wherein The gaseous ferric chloride is recycled to the low-temperature oxidation reaction process and provides heat for the low-temperature oxidation reaction.

9. The method for low-temperature solid-phase oxidation of ferric chloride according to any one of claims 1 to 8, characterized in that: In step (2), the oxygen content in the chlorine gas is 0-5%. After the chlorine gas is purified, high-purity chlorine gas is obtained. The purity of the high-purity chlorine gas is 98%-99.5%. The high-purity chlorine gas is used in the chlorination process.

10. The method for low-temperature solid-phase oxidation of ferric chloride according to any one of claims 1 to 8, characterized in that: In step (2), the mass percentage of iron oxide in the crude iron oxide is 80% to 95%; in step (3), the yield of the mica iron oxide product is 90% to 98%, and the purity of the mica iron oxide product is 99.00% to 99.99%.

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