Method and system for recovering titanium dioxide solid residues produced by fluorination method

Abstract

The invention discloses a method and a system for recovering solid residues in titanium dioxide production by a fluorination method. The recovery method comprises the following steps: mixing and reacting solid residues obtained after titanium dioxide is produced by a fluorination method with concentrated sulfuric acid with the concentration of 95-100wt% at the temperature of 25 DEG C or above, so as to obtain ferric sulfate and hydrogen fluoride. According to the method for recycling the solid residues in the titanium dioxide produced through the fluorination method, FeF3 in the solid residues can be converted into Fe2 (SO4) 3 and HF to be recycled, waste is turned into wealth, H2SO4 used in the recycling method is wide in source, the requirement for technological conditions is low, pollution to the environment is small, and the method is suitable for industrial production. And clean production can be realized while the process energy consumption is reduced.

Description

Technical Field

[0001] The invention relates to the field of recycling solid residues produced by fluoridation of titanium dioxide, and in particular to a method and system for recycling solid residues produced by fluoridation of titanium dioxide. Background Art

[0002] Titanium dioxide (TiO 2 ), with high chemical stability, heat resistance, weather resistance, good whiteness, tinting power and hiding power, is considered to be the best white pigment and important chemical product in the world. It is non-toxic, has the best opacity, the best whiteness and brightness. Titanium dioxide is divided into pigment grade and non-pigment grade according to its use. Pigment grade titanium dioxide is mainly used in coatings, plastics, papermaking, rubber, printing inks, chemical fibers and other industries, while non-pigment grade titanium dioxide is mainly used in enamel, capacitors, welding rods, etc.

[0003] At present, the industrial production methods of titanium dioxide include sulfuric acid method and chlorination method. The sulfuric acid method has a long process flow, discontinuous production process, high energy consumption, and large amount of "three wastes" emissions. The chlorination process has high requirements for raw materials and high construction costs due to foreign technical barriers.

[0004] The fluorination process for preparing titanium dioxide effectively solves the problems of high pollution and high energy consumption faced by the existing sulfuric acid process. This method uses titanium-containing materials such as ilmenite, titanium concentrate or high-titanium slag as raw materials, and based on the recycling technology of fluorination agents, it efficiently extracts titanium, iron, silicon, vanadium and other elements from titanium-containing raw materials. The process is green and environmentally friendly. However, the FeF-containing ... 3 How to efficiently utilize the solid residue, which is mainly composed of carbon dioxide, is crucial to the integrity, environmental protection and economy of the entire process system.

[0005] The publication number is "CN110498450B" "A method for preparing TiO2 from ilmenite 2 One solution proposed in the "method of preparing powder and iron oxide red" is to subject the aforementioned solid residue to thermal hydrolysis to generate Fe 2 O 3 , and recover the ammonia and hydrogen fluoride generated during the thermal hydrolysis process.

[0006] The method for treating titanium magnetite ore material disclosed in the publication number "CN111989413A" is to perform thermal hydrolysis on the solid residue to generate Fe 2 O 3 , and recover the generated hydrogen fluoride during the thermal hydrolysis process.

[0007] Although the above prior art mentions that FeF is produced in the process of producing titanium dioxide by fluorination, 3The solid residue, which is mainly composed of slag, undergoes thermal hydrolysis with high-temperature steam to generate iron oxide and hydrogen fluoride, which can then be recycled. However, a large amount of high-temperature steam is required, and the reaction temperature is high, resulting in high energy consumption. In addition, the high-temperature resistance performance of the equipment is high, resulting in high equipment investment and maintenance costs. Summary of the invention

[0008] In view of the deficiencies in the prior art, the object of the present invention is to provide a method and system for recovering solid residues from titanium dioxide produced by fluorination.

[0009] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention includes: The invention provides a method for recovering solid residue of titanium dioxide produced by fluorination, comprising: mixing and reacting the solid residue after titanium dioxide is produced by fluorination with concentrated sulfuric acid with a concentration of 95wt%-100wt%, thereby obtaining ferric sulfate and hydrogen fluoride.

[0010] In a specific embodiment, the solid residue is mixed with the concentrated sulfuric acid at a temperature above 25° C. to react, thereby obtaining iron sulfate and hydrogen fluoride.

[0011] In one embodiment, the reaction temperature is 25°C to 120°C; In one embodiment, the reaction is carried out under normal pressure.

[0012] In one specific embodiment, the reaction time is 0.5 to 4 hours.

[0013] In a specific embodiment, the mass ratio of the solid residue to the concentrated sulfuric acid is 1:1.4 to 1:2.5.

[0014] In a specific embodiment, after the reaction is completed, iron sulfate is separated from the solid phase reaction product, and hydrogen fluoride is separated from the gas phase reaction product.

[0015] The present invention also provides a recovery system for solid residues of titanium dioxide produced by fluorination method, comprising: A premixer is used to fully mix the solid residue after the production of titanium dioxide by the fluorination method with concentrated sulfuric acid with a concentration of 98wt% or more to form a mixed reactant; The acidolysis reactor is used to receive the mixed reactants and provide the reaction conditions required for the acidolysis reaction, so that the solid residue in the mixed reactants undergoes the acidolysis reaction with the concentrated sulfuric acid, thereby producing ferric sulfate and hydrogen fluoride.

[0016] In a specific embodiment, the recovery system of solid residue of titanium dioxide produced by fluorination method is characterized in that it also includes a silo and a storage tank, the silo is connected to the premixer and is used to provide the solid residue to the premixer, and the storage tank is connected to the premixer and is used to provide the concentrated sulfuric acid to the premixer.

[0017] In a specific embodiment, the recovery system for solid residue of titanium dioxide produced by fluorination method also includes a first discharge pipe, a circulating cooler and a second discharge pipe; the first discharge pipe is connected to the acidolysis reactor, and is used to discharge the gaseous product generated by the acidolysis reaction; the circulating cooler is connected to the acidolysis reactor, and is used to cool the solid product generated by the acidolysis reaction; the second discharge pipe is connected to the circulating cooler, and is used to discharge the cooled solid product.

[0018] Compared with the prior art, the advantages of the present invention include: 1) The present invention provides a method for recovering solid residues from the production of titanium dioxide by fluorination, which can recover FeF 3 Converted to Fe 2 (SO 4 ) 3 and HF for recycling; 2) The concentrated H2O2 required for the recovery of the solid residue from the production of titanium dioxide by fluorination provided by the present invention 2 SO 4 It has a wide range of sources, low requirements on process conditions, and little pollution to the environment. It can achieve clean production while reducing process energy consumption; 3) The method for recovering solid residue from titanium dioxide produced by fluorination provided by the present invention is simple and easy to operate, has low cost, strong applicability, and can be widely used. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic diagram of the structure of a recovery system for solid residues of titanium dioxide produced by a fluorination process provided by the present invention; Explanation of the accompanying drawings: 1. Silo; 2. Storage tank; 3. Premixer; 4. Acid hydrolysis reactor; 5. Circulating cooler; 6. Hydrofluoric acid preparation process system; 7. Lithium iron phosphate preparation process system. DETAILED DESCRIPTION

[0020] In view of the deficiencies in the prior art, the inventor of this case has proposed the technical solution of the present invention after long-term research and extensive practice. The technical solution, its implementation process and principle will be further explained as follows.

[0021] Example 1 See also Figure 1This embodiment provides a recovery system for solid residues of titanium dioxide produced by fluorination method, which includes a silo, a storage tank, a premixer, an acidolysis reactor and a circulating cooler. Specifically, the premixer is connected to the acidolysis reactor and can premix solid residues and sulfuric acid, so that the mixed mixture enters the acidolysis reactor for acidolysis reaction. Of course, the silo and the storage tank can also be connected to the premixer, the silo is used to accommodate solid residues, and the solid residues are input to the premixer through a feed line connected to the premixer, and the storage tank is used to store sulfuric acid, and sulfuric acid can be input to the premixer through a feed line connected to the premixer.

[0022] After sulfuric acid and solid residue are uniformly mixed in the premixer, they are introduced into the acid hydrolysis reactor for acid hydrolysis reaction to generate Fe 2 (SO 4 ) 3 And HF, wherein HF can be discharged through a first discharge pipe connected to the acidolysis reactor, and of course the first discharge pipe can also be connected to a downstream hydrofluoric acid preparation process system to use HF as a raw material for downstream production of hydrofluoric acid products.

[0023] The Fe produced 2 (SO 4 ) 3 The Fe2O3 can be discharged through a second discharge pipe connected to the acid hydrolysis reactor. Of course, the second discharge pipe can also be connected to a circulating cooler. 2 (SO 4 ) 3 It can be connected to the downstream lithium iron phosphate preparation process system and serve as the raw material for the downstream production of lithium iron phosphate products.

[0024] In addition, this embodiment also provides a method for recovering solid residue of titanium dioxide produced by fluorination, which is implemented based on the above recovery system and includes the following steps: S1, placing the solid residue after the production of titanium dioxide by fluorination into silo 1 in advance, and placing concentrated sulfuric acid with a concentration of 98wt% into storage tank 2; S2, opening the valve on the pipeline connecting the silo 1 and the premixer 3, and opening the valve on the pipeline connecting the storage tank 2 and the premixer 3, so that the solid residue and the concentrated sulfuric acid are uniformly mixed in the premixer 3 at a mass ratio of 1:1.4 to form a mixed reactant; S3, opening the valve on the pipeline connecting the premixer 3 and the acidolysis reactor 4, allowing the mixed reactants to react in the acidolysis reactor 4, and setting the reaction temperature to 35° C., continuing the reaction for 2 hours, and then ending the reaction; S4, opening the valve of the first discharge pipe connecting the acidolysis reactor 4 and the hydrofluoric acid preparation process system 6, so that the HF gas generated in step S3 is discharged from the system; S5, open the valve on the pipeline connecting the acid hydrolysis reactor 4 and the circulating cooler 5, so that the solid phase product Fe after the thermal hydrolysis reaction in step S3 2 (SO 4 ) 3 It is cooled to 25℃~60℃ by the circulating cooler and then discharged from the system.

[0025] In a preferred embodiment, the HF gas (hereinafter referred to as hydrogen fluoride) coming out of the acidolysis reactor 4 can be used as a raw material for downstream production of hydrofluoric acid products, and the first discharge pipe can be connected to the downstream hydrofluoric acid preparation process system.

[0026] In another preferred embodiment, the cooled Fe 2 (SO 4 ) 3 (hereinafter referred to as ferrous sulfate) can be used as a raw material for producing downstream lithium iron phosphate products, and the second discharge pipe can be connected to the downstream lithium iron phosphate preparation process system.

[0027] The mechanism of the aforementioned acid hydrolysis reaction can be referred to the following formula:

[0028] By adopting the method of this embodiment, 1224 g of ferric sulfate is produced based on 1000 g of titanium dioxide solid residue produced by fluorination method, wherein the ferric trifluoride content in the solid residue is 86.33%, and 330 g of hydrogen fluoride can be directly collected in gaseous form, and its concentration is 35.6%.

[0029] Example 2 This embodiment also provides a method for recovering solid residue from titanium dioxide produced by fluorination, which is basically the same as that in Embodiment 1, except that the solid residue and the concentrated sulfuric acid are uniformly mixed in the premixer 3 at a mass ratio of 1:2, and the acidolysis reaction temperature is 25°C and the time is 4 hours.

[0030] Using the method of this embodiment, 1377 g of ferric sulfate is produced based on 1000 g of solid residue of titanium dioxide produced by fluorination, and 430 g of hydrogen fluoride can be directly collected in gaseous form, with a concentration of 37.2%.

[0031] Example 3 This embodiment also provides a method for recovering solid residue from titanium dioxide produced by fluorination, which is basically the same as that in Embodiment 1, except that the solid residue and the concentrated sulfuric acid are uniformly mixed in the premixer 3 at a mass ratio of 1:2.5, and the acidolysis reaction temperature is 120° C. and the time is 0.5 h.

[0032] Using the method of this embodiment, 1469 g of ferric sulfate is produced based on 1000 g of solid residue of titanium dioxide produced by fluorination, and 440 g of hydrogen fluoride can be directly collected in gaseous form, with a concentration of 37.5%.

[0033] Comparative Example 1 This embodiment also provides a method for recovering solid residues from titanium dioxide produced by fluorination, which is basically the same as that in Embodiment 1, except that the concentrated sulfuric acid is replaced by a sulfuric acid solution having a concentration of 75 wt %, and the H 2 SO 4 The content is the same as that of the concentrated sulfuric acid.

[0034] By adopting the method of this comparative example, 1071 g of ferric sulfate is produced based on 1000 g of solid residue of titanium dioxide produced by fluorination, and 289 g of hydrogen fluoride can be directly collected in gaseous form, with a concentration of 31.8%.

[0035] Comparative Example 2 This embodiment also provides a method for recovering solid residues from titanium dioxide produced by fluorination, which is basically the same as that in embodiment 1, except that the concentrated sulfuric acid is replaced by concentrated hydrochloric acid with a concentration of 37%, and the H + The content is the same as that of the concentrated sulfuric acid.

[0036] By adopting the method of this comparative example, 1238 g of ferric chloride is produced based on 1000 g of solid residue of titanium dioxide produced by fluorination, and 458 g of hydrogen fluoride can be directly collected in gaseous form, with a concentration of 9.5%.

[0037] Comparative Example 3 This embodiment also provides a method for recovering solid residues from titanium dioxide produced by fluorination, which is basically the same as that in Embodiment 1, except that the concentrated sulfuric acid is replaced by concentrated nitric acid with a concentration of 65%, and the H + The content is the same as that of the concentrated sulfuric acid.

[0038] By adopting the method of this comparative example, 1848 g of ferric nitrate is produced based on 1000 g of solid residue of titanium dioxide produced by fluorination, and 504 g of hydrogen fluoride can be directly collected in gaseous form, with a concentration of 16.6%.

[0039] In the present application, the yield and purity of gas-phase hydrogen fluoride in Examples 1 to 3 are significantly higher than those in Comparative Examples 1 to 3. The reasons may be: Although hydrochloric acid can react with solid residue, hydrochloric acid itself will volatilize hydrogen chloride gas and enter into the product hydrogen fluoride, resulting in low purity of the generated hydrogen fluoride and increasing the difficulty of subsequent separation and purification of hydrogen fluoride.

[0040] The nitric acid content in concentrated nitric acid is about 65%. It is easily decomposed by light or heat to produce nitrogen dioxide, which enters into the product hydrogen fluoride, resulting in low purity of the generated hydrogen fluoride, which increases the difficulty of subsequent separation and purification of hydrogen fluoride. It is also not applicable.

[0041] In the present application, concentrated sulfuric acid is used to react with the solid residue, which has at least the following advantages: ① The reaction conditions required for the acidolysis reaction are mild, the energy consumption is low, the reaction rate is fast, and the higher the concentration of concentrated sulfuric acid, the faster the reaction rate, the more thorough the reaction degree, and the higher the yield; ② The water content in concentrated sulfuric acid is very small, and hydrogen fluoride is very soluble in water. The use of concentrated sulfuric acid can effectively avoid a large amount of product hydrogen fluoride from dissolving in sulfuric acid; ③ Because the raw material contains water, concentrated sulfuric acid has good water absorption, which can effectively reduce the water content in the product hydrogen fluoride and simplify the post-treatment process of the product; ④ In this embodiment, concentrated sulfuric acid and ferric fluoride can react at 25-120°C. Even if sulfuric acid is highly corrosive, more common organic corrosion-resistant materials can also be used normally in this temperature range. For example, in the acidolysis reaction equipment, polytetrafluoroethylene is used as the lining material (which can be used for a long time at -180 to 260°C), so that the reaction can be carried out at room temperature and pressure, the process conditions are mild, the equipment material can also be effectively solved, the process operation is simple, and the applicability is strong.

[0042] The system and method for recovering solid residues from the production of titanium dioxide by fluorination provided by the present invention can not only recover and reuse the solid residues produced as byproducts from the production of titanium dioxide by fluorination, but also require lower process conditions for the treatment of the solid residues, and cause less environmental pollution, thereby achieving clean production and lower production energy consumption. 2 (SO 4 ) 3 HF can also be reintroduced into the downstream lithium iron phosphate preparation and hydrofluoric acid preparation processes, achieving resource recycling and reuse.

[0043] It should be understood that the above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for recovering solid residue from titanium dioxide produced by fluorination, characterized in that: include: The solid residue after the titanium dioxide is produced by the fluorination method is mixed with concentrated sulfuric acid with a concentration of 95wt% to 100wt% to obtain iron sulfate and hydrogen fluoride.

2. The method for recovering solid residue from titanium dioxide produced by fluorination according to claim 1, characterized in that: include: The solid residue is mixed with the concentrated sulfuric acid at a temperature of 25° C. or higher to react, thereby obtaining iron sulfate and hydrogen fluoride.

3. The method for recovering solid residue from titanium dioxide produced by fluorination according to claim 1, characterized in that: The reaction temperature is 25°C to 120°C.

4. The method for recovering solid residue from titanium dioxide produced by fluorination according to claim 1, characterized in that: The reaction is carried out under normal pressure.

5. The method for recovering solid residue from titanium dioxide produced by fluorination according to claim 1, characterized in that: The reaction time is 0.5~4h.

6. The method for recovering solid residue from titanium dioxide produced by fluorination according to claim 1, characterized in that: The mass ratio of the solid residue to the concentrated sulfuric acid is 1:1.4 to 1:2.

5.

7. The method for recovering solid residue from titanium dioxide produced by fluorination according to claim 1, characterized in that: After the reaction is completed, iron sulfate is separated from the solid phase reaction product, and hydrogen fluoride is separated from the gas phase reaction product.

8. A system for recovering solid residues from titanium dioxide produced by fluorination, characterized in that: include: A premixer (3) is used to fully mix the solid residue after the production of titanium dioxide by the fluorination method with concentrated sulfuric acid having a concentration of 98 wt % or more to form a mixed reactant; The acidolysis reactor (4) is used to receive the mixed reactants and provide reaction conditions required for the acidolysis reaction, so that the solid residue in the mixed reactants undergoes the acidolysis reaction with the concentrated sulfuric acid, thereby producing iron sulfate and hydrogen fluoride.

9. The system for recovering solid residues from titanium dioxide produced by fluorination according to claim 8, characterized in that: The invention also comprises a silo (1) and a storage tank (2), wherein the silo (1) is connected to the premixer (3) and is used to provide the solid residue to the premixer (3), and the storage tank (2) is connected to the premixer (3) and is used to provide the concentrated sulfuric acid to the premixer (3).

10. The system for recovering solid residues from titanium dioxide produced by fluorination according to claim 9, characterized in that: It also includes a first discharge pipe, a circulating cooler (5) and a second discharge pipe; the first discharge pipe is connected to the acidolysis reactor (4) and is used to discharge the gaseous product generated by the acidolysis reaction; the circulating cooler (5) is connected to the acidolysis reactor (4) and is used to cool the solid product generated by the acidolysis reaction; the second discharge pipe is connected to the circulating cooler (5) and is used to discharge the cooled solid product.

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