Method for recycling sulfuric acid process titanium dioxide waste acid and application thereof

Abstract

The invention relates to the technical field of production of titanium dioxide by a sulfuric acid method, and discloses a method for recycling sulfuric acid method titanium dioxide waste acid, which comprises the following steps: carrying out solid-liquid separation on a product generated in a sulfuric acid method titanium dioxide hydrolysis process to obtain titanium dioxide waste acid; the titanium white waste acid is reused in the leaching process of acidolysis solid-phase substances of titanium concentrate or titanium slag, and the leaching temperature, the leaching time and the stirring speed are controlled for a leaching reaction; and carrying out solid-liquid separation on the system after the leaching reaction to obtain a titanium-containing leaching solution and leaching residues, and returning the titanium-containing leaching solution to a subsequent process of titanium dioxide production by a sulfuric acid method. According to the method, the titanium dioxide waste acid is innovatively used for the leaching procedure of the acidolysis solid-phase matter of the titanium concentrate, and the technological parameters of the leaching procedure of the acidolysis solid-phase matter are improved, so that the problems of high viscosity, low leaching efficiency and the like of a titanium dioxide waste acid system are solved, and efficient utilization of the titanium dioxide waste acid is realized.

Description

Technical Field

[0001] This invention relates to the field of titanium dioxide production technology using the sulfuric acid process, and more particularly to a method for recycling waste acid from the sulfuric acid process for titanium dioxide production. Background Technology

[0002] The sulfuric acid process is the mainstream technology for producing titanium dioxide, but its hydrolysis process generates a large amount of titanium dioxide waste acid. China generates over 26 million tons of titanium dioxide waste acid annually, and the current treatment of this waste acid accounts for approximately 10% of the total cost of titanium dioxide production. There is an urgent need to develop a low-cost and green method for treating titanium dioxide waste acid. Titanium dioxide waste acid mainly contains 20wt% H₂SO₄ and 10wt% FeSO₄, as well as small amounts of sulfates such as MgSO₄ and CaSO₄. The complexity of the waste acid composition exacerbates the difficulty of treatment and utilization.

[0003] Currently, traditional methods for treating waste acid from titanium dioxide production in industry mainly include neutralization and concentration / recovery. Neutralization involves adding alkaline substances such as lime to neutralize acidity, generating a large amount of titanium gypsum solid waste. This not only results in the permanent waste of valuable resources such as titanium and iron but also introduces new storage and environmental risks. Concentration / recovery requires a large amount of energy to evaporate moisture, making it uneconomical and causing severe equipment corrosion and high operating costs. Both methods treat waste acid as end-use waste, failing to fully utilize its still valuable acidity and effective components. There is a need for a low-cost, high-efficiency new method that can reduce waste acid production at the source and achieve direct recycling of waste acid resources within the process. This is crucial for reducing the production cost of sulfuric acid-process titanium dioxide, improving resource utilization, and reducing environmental pollution, and is also an urgent technological need in the industry. Therefore, there is a need to improve existing methods for recycling waste acid from the sulfuric acid process in titanium dioxide production. Summary of the Invention

[0004] In view of this, the purpose of this invention is to propose a method for recycling waste acid from the sulfuric acid process for titanium dioxide. The waste acid is used in the leaching process of the solid phase of titanium concentrate acid hydrolysis. By improving the process parameters of the solid phase leaching process, the problems of high viscosity and low leaching efficiency of the waste acid system are overcome, and the efficient utilization of waste acid from titanium dioxide is achieved.

[0005] To achieve the above objectives, this invention provides a method for recycling waste acid from the sulfuric acid process for titanium dioxide production, comprising the following steps: S1 involves solid-liquid separation of the products generated during the sulfuric acid process for titanium dioxide hydrolysis to obtain titanium dioxide waste acid. S2 reuses waste acid from titanium dioxide in the leaching process of the acid-hydrolyzed solid phase of titanium concentrate or titanium slag, controlling the leaching temperature, leaching time, and stirring speed to carry out the leaching reaction. S3 performs solid-liquid separation on the system after the leaching reaction to obtain titanium-containing leachate and leaching residue. The titanium-containing leachate is returned to the subsequent process of sulfuric acid process titanium dioxide production.

[0006] In some embodiments, in S1, the solid-liquid separation method is any one of gravity sedimentation, centrifugal separation, or filtration.

[0007] In some embodiments, in S1, the titanium dioxide waste acid includes sulfuric acid and ferrous sulfate.

[0008] In some embodiments, the mass concentration of sulfuric acid in the titanium dioxide waste acid is 15% to 25%, and the mass concentration of ferrous sulfate is 5% to 15%.

[0009] In some embodiments, the leaching temperature in S2 is 40°C to 70°C.

[0010] In some implementations, the leaching time in S2 is 300 to 420 minutes.

[0011] In some embodiments, the stirring speed in S2 is 250 r / min to 350 r / min.

[0012] In some embodiments, in S2, the acid-hydrolyzed solid is the solid produced by acid hydrolysis and aging of titanium concentrate with sulfuric acid.

[0013] In some embodiments, in S2, the liquid-to-solid mass ratio (ml / g) of titanium dioxide waste acid and acid-hydrolyzed solids during the leaching reaction is (3~6):1.

[0014] In another aspect, the present invention provides an application of the method described above for reducing the consumption of fresh sulfuric acid and the discharge of waste acid in the sulfuric acid process for titanium dioxide production.

[0015] The present invention has at least the following beneficial technical effects: This invention addresses the problems of titanium dioxide waste acid generated during the sulfuric acid process for treating titanium dioxide, including waste of titanium resources, high costs, and new environmental pollution risks. It proposes a method for recycling waste acid from the sulfuric acid process. The method involves simply filtering the hydrolysis product to remove solid impurities, obtaining liquid-phase titanium dioxide waste acid. This waste acid is then used in the leaching process of the solid phase from the acidolysis of titanium concentrate. Further improvements to the process parameters of the acidolysis solid phase leaching process overcome the problems of high viscosity and low leaching efficiency in the titanium dioxide waste acid system, achieving highly efficient utilization of the waste acid. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other embodiments can be obtained based on these drawings without creative effort.

[0017] Figure 1 A flowchart illustrating an embodiment of the sulfuric acid process for titanium dioxide hydrolysis provided by this invention; Figure 2 A flowchart illustrating an embodiment of the method for recycling waste acid from the sulfuric acid process for titanium dioxide production provided by the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific examples and the accompanying drawings.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. For example, terms such as “length,” “width,” “upper,” “lower,” “left,” “right,” “front,” “rear,” “vertical,” “horizontal,” “top,” “bottom,” “inner,” and “outer” indicate orientations or positions based on the orientations or positions shown in the accompanying drawings and are for ease of description only, and should not be construed as limiting the technical solution.

[0020] The terms "comprising" and "having," and any variations thereof, used in the specification, claims, and accompanying drawings of this invention are intended to cover non-exclusive inclusion; the terms "first," "second," etc., used in the specification, claims, and accompanying drawings are used to distinguish different objects, not to describe a particular order. "A plurality of" means two or more, unless otherwise explicitly specified.

[0021] Furthermore, the reference to "embodiment" herein means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0022] like Figure 1 As shown, the waste acid from the current sulfuric acid process for titanium dioxide production is generated during the hydrolysis of titanium dioxide. The current sulfuric acid process for titanium dioxide production includes the following steps: (1) Acid hydrolysis: Acid hydrolysis is carried out using titanium concentrate or titanium slag and concentrated sulfuric acid (usually 98 wt.%) as the main raw materials under forced stirring and initiation reaction. The main reaction is the reaction of ilmenite with sulfuric acid to produce soluble titanium oxysulfate and ferrous sulfate, etc. After the reaction, a viscous acid hydrolysis solid phase is obtained.

[0023] (2) Leaching and Reduction: The acid-hydrolyzed solid is leached with water or dilute sulfuric acid to dissolve the soluble sulfates, forming a titanium-containing solution. Iron filings are usually added to remove Fe from the solution. 3+ Reduced to Fe 2+ This is to facilitate subsequent separation.

[0024] (3) Purification and sedimentation: By controlling the conditions (such as heating, adding seed crystals, etc.), most of the impurities in the titanium liquid (such as silicon, aluminum, etc.) are hydrolyzed to form precipitates, which are then removed by sedimentation and filtration to obtain purified titanium liquid.

[0025] (4) Hydrolysis: This is the core process for generating waste acid from titanium dioxide. The purified titanium liquid is heated to boiling or seed crystals are added to induce hydrolysis. At this time, the titanium oxysulfate in the solution undergoes a hydrolysis reaction, generating a white hydrated titanium dioxide precipitate, while releasing sulfuric acid.

[0026] (5) Filtration and washing: The hydrolyzed slurry is filtered to achieve solid-liquid separation. Solid phase: Hydrated titanium dioxide (metatinic acid) filter cake is obtained, which is then washed, calcined, and other processes to produce titanium dioxide products. Liquid phase: The filtered acidic liquid is titanium dioxide waste acid. Its main components are about 15-25% free sulfuric acid and about 5-15% ferrous sulfate, as well as a small amount of incompletely hydrolyzed titanium and other metal sulfates.

[0027] Titanium dioxide waste acid is a direct byproduct of the core chemical reaction in the sulfuric acid process, where titanium liquor is hydrolyzed to produce metatitanic acid; its generation is inevitable. This application recycles titanium dioxide waste acid for upstream processes, such as... Figure 2 As shown, the specific steps include: S1 involves solid-liquid separation of the products generated during the sulfuric acid process for titanium dioxide hydrolysis to obtain titanium dioxide waste acid. S2 reuses waste acid from titanium dioxide in the leaching process of the acid-hydrolyzed solid phase of titanium concentrate or titanium slag, controlling the leaching temperature, leaching time, and stirring speed to carry out the leaching reaction. S3 performs solid-liquid separation on the system after the leaching reaction to obtain titanium-containing leachate and leaching residue. The titanium-containing leachate is returned to the subsequent process of sulfuric acid process titanium dioxide production.

[0028] Furthermore, in S1, the solid-liquid separation method is any one of gravity sedimentation, centrifugal separation, or filtration. The core purpose of this step is to remove solid suspended impurities entrained in the titanium dioxide waste acid, such as incompletely hydrolyzed fine particles and small amounts of silica-alumina precipitates, ensuring that the recycled waste acid is a relatively clean liquid phase and preventing the accumulation of solid impurities in subsequent leaching processes, which could affect mass transfer efficiency or contaminate the product. Using physical solid-liquid separation methods is simple to operate, low in cost, and does not alter the chemical properties of the waste acid. Employing conventional physical separation methods eliminates the need for chemical reagents, aligning with the technical route of "direct reuse" rather than "chemical conversion," which lays the foundation for the direct use of the waste acid as a leaching agent in subsequent processes.

[0029] Furthermore, the waste acid from titanium dioxide includes sulfuric acid and ferrous sulfate, wherein the mass concentration of sulfuric acid in the waste acid from titanium dioxide is 15%~25% and the mass concentration of ferrous sulfate is 5%~15%.

[0030] Furthermore, in S2, the leaching temperature is 40°C to 70°C, and the leaching time is 300 to 420 minutes. The stirring speed is 250 r / min to 350 r / min. This leaching temperature reduces the system viscosity, increases the rate of molecular thermal motion, and promotes reaction kinetics. Within this temperature range, the viscosity of the waste acid decreases significantly, and its fluidity increases, which is beneficial for its penetration and diffusion into the acid-hydrolyzed solid phase. The leaching time ensures the reaction proceeds fully. Since the reactivity of the waste acid may be lower than that of fresh dilute sulfuric acid, and the mass transfer resistance is relatively large, sufficient time is needed to complete the dissolution and diffusion of titanium from the solid phase to the liquid phase. The stirring speed is used to force convection, enhance mass transfer, and prevent local overheating or uneven concentration. Mechanical stirring can break the stagnant layer caused by the high viscosity of the waste acid, continuously renew the solid-liquid interface, transport fresh waste acid to the reaction surface, and remove dissolved products.

[0031] Furthermore, in S2, the acid-hydrolyzed solid is the solid produced after the titanium concentrate is acid-hydrolyzed and matured with sulfuric acid, and the liquid-solid mass ratio (ml / g) of titanium dioxide waste acid and acid-hydrolyzed solid during the leaching reaction is (3~6):1.

[0032] In another aspect, the present invention provides an application of the method described above for reducing the consumption of fresh sulfuric acid and the discharge of waste acid in the sulfuric acid process for titanium dioxide production.

[0033] The present invention will be further explained below with reference to specific embodiments.

[0034] Example 1 A method for recycling waste acid from the sulfuric acid process for titanium dioxide production, comprising the following specific steps: (1) The product obtained from the sulfuric acid process for titanium dioxide hydrolysis is filtered to obtain titanium dioxide waste acid liquid; (2) The obtained titanium dioxide waste acid is recycled for the leaching process of titanium concentrate acid hydrolysis solids, and the leaching process parameters are further improved, wherein the temperature is controlled at 70℃, the time is controlled at 420 min, and the rotation speed is controlled at 350 r / min. (3) By improving the process parameters of the titanium dioxide waste acid leaching system for titanium concentrate acid hydrolysis solid phase, the problems of high viscosity and low leaching efficiency of the titanium dioxide waste acid system were effectively overcome. The titanium leaching rate can reach 97.4%, which is comparable to that of dilute sulfuric acid, thus realizing the efficient utilization of titanium dioxide waste acid.

[0035] Example 2 A method for recycling waste acid from the sulfuric acid process for titanium dioxide production, comprising the following specific steps: (1) The product obtained from the sulfuric acid process for titanium dioxide hydrolysis is filtered to obtain titanium dioxide waste acid liquid; (2) The obtained titanium dioxide waste acid is recycled for the leaching process of titanium concentrate acid hydrolysis solids, and the leaching process parameters are further improved, wherein the temperature is controlled at 55℃, the time is controlled at 400 min, and the rotation speed is controlled at 300 r / min. (3) By improving the process parameters of the titanium dioxide waste acid leaching system for the solid phase of titanium concentrate, the problems of high viscosity and low leaching efficiency of the titanium dioxide waste acid system were effectively overcome. The titanium leaching rate of titanium concentrate can reach 97.1%, which is basically comparable to that of dilute sulfuric acid, thus realizing the efficient utilization of titanium dioxide waste acid.

[0036] Example 3 A method for recycling waste acid from the sulfuric acid process for titanium dioxide production, comprising the following specific steps: (1) The product obtained from the sulfuric acid process for titanium dioxide hydrolysis is filtered to obtain titanium dioxide waste acid liquid; (2) The obtained titanium dioxide waste acid is recycled for the leaching process of titanium concentrate acid hydrolysis solids, and the leaching process parameters are further improved, wherein the temperature is controlled at 40℃, the time is controlled at 380 min, and the rotation speed is controlled at 250 r / min. (3) Improved process parameters for leaching titanium concentrate solids from titanium dioxide waste acid effectively overcome problems such as high viscosity and low leaching efficiency in the titanium dioxide waste acid system. The titanium leaching rate of titanium concentrate can reach 97.2%, almost equivalent to that of dilute sulfuric acid, enabling efficient utilization of titanium dioxide waste acid.

[0037] Example 4 A method for recycling waste acid from the sulfuric acid process for titanium dioxide production, comprising the following specific steps: (1) The product obtained from the sulfuric acid process for titanium dioxide hydrolysis is filtered to obtain titanium dioxide waste acid liquid; (2) The obtained titanium dioxide waste acid is recycled for the leaching process of titanium concentrate acid hydrolysis solids, and the leaching process parameters are further improved, wherein the temperature is controlled at 40℃, the time is controlled at 300 min, and the rotation speed is controlled at 250 r / min. (3) By improving the process parameters of the titanium dioxide waste acid leaching system for the solid phase of titanium concentrate, the problems of high viscosity and low leaching efficiency of the titanium dioxide waste acid system have been effectively overcome. The titanium leaching rate of titanium concentrate can reach 96.8%, which is almost equivalent to that of dilute sulfuric acid, thus realizing the efficient utilization of titanium dioxide waste acid.

[0038] This invention transforms titanium dioxide waste acid, traditionally treated as end-of-life waste, into a useful resource in the production process, avoiding the secondary pollution problems of large amounts of titanium gypsum solid waste generated by neutralization or high energy consumption and high corrosion associated with concentration methods. By controlling the leaching temperature (40-70℃), leaching time (300-420 min), stirring intensity (250-350 r / min), and liquid-to-solid ratio, the core technical obstacles of low mass transfer efficiency and poor reactivity caused by the high viscosity and high solid content of waste acid are effectively solved. Replacing more than 70% or even all of the fresh concentrated sulfuric acid required for leaching with waste acid directly reduces the procurement cost of the main raw materials, resulting in significant economic benefits.

[0039] The above are exemplary embodiments disclosed in this invention. However, it should be noted that various changes and modifications can be made without departing from the scope of the embodiments of this invention as defined by the claims. The functions, steps, and / or actions of the methods according to the disclosed embodiments described herein do not need to be performed in any particular order. Furthermore, although the elements disclosed in the embodiments of this invention may be described or claimed individually, they may be understood as multiple unless explicitly limited to a singular number.

[0040] It should be understood that, as used herein, the singular form “a” is intended to include the plural form as well, unless the context clearly supports an exception. It should also be understood that, as used herein, “and / or” refers to any and all possible combinations of one or more of the associated listed items.

[0041] The embodiment numbers disclosed in the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0042] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples. Within the framework of the invention, technical features of the above embodiments or different embodiments can be combined, and many other variations of different aspects of the invention exist, which are not provided in the details for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A method for recycling waste acid from the sulfuric acid process in titanium dioxide production, characterized in that, Includes the following steps: S1 involves solid-liquid separation of the products generated during the sulfuric acid process for titanium dioxide hydrolysis to obtain titanium dioxide waste acid. S2 reuses the waste acid from titanium dioxide in the leaching process of the acid-hydrolyzed solid phase of titanium concentrate or titanium slag, controlling the leaching temperature, leaching time and stirring speed to carry out the leaching reaction. S3 performs solid-liquid separation on the system after the leaching reaction to obtain titanium-containing leachate and leaching residue. The titanium-containing leachate is returned to the subsequent process of sulfuric acid process titanium dioxide production.

2. The method for recycling waste acid from the sulfuric acid process for titanium dioxide production according to claim 1, characterized in that, In S1, the solid-liquid separation method is any one of gravity sedimentation, centrifugal separation, or filtration.

3. The method for recycling waste acid from the sulfuric acid process for titanium dioxide production according to claim 1, characterized in that, In S1, the titanium dioxide waste acid includes sulfuric acid and ferrous sulfate.

4. The method for recycling waste acid from the sulfuric acid process for titanium dioxide production according to claim 3, characterized in that, The mass concentration of sulfuric acid in the titanium dioxide waste acid is 15%~25%, and the mass concentration of ferrous sulfate is 5%~15%.

5. The method for recycling waste acid from the sulfuric acid process for titanium dioxide production according to claim 1, characterized in that, In S2, the leaching temperature is 40°C to 70°C.

6. The method for recycling waste acid from the sulfuric acid process for titanium dioxide production according to claim 1, characterized in that, In S2, the leaching time is 300 to 420 minutes.

7. The method for recycling waste acid from the sulfuric acid process for titanium dioxide production according to claim 1, characterized in that, In S2, the stirring speed is 250 r / min to 350 r / min.

8. The method for recycling waste acid from the sulfuric acid process for titanium dioxide production according to claim 1, characterized in that, In S2, the acid-hydrolyzed solid is the solid produced by acid hydrolysis and aging of titanium concentrate with sulfuric acid.

9. The method for recycling waste acid from the sulfuric acid process for titanium dioxide production according to claim 1, characterized in that, In S2, the liquid-solid mass ratio of the titanium dioxide waste acid to the acid hydrolysis solid during the leaching reaction is (3~6):

1.

10. An application of the method according to any one of claims 1 to 9, characterized in that, This is used to reduce the consumption of fresh sulfuric acid and the discharge of waste acid in the sulfuric acid process for titanium dioxide production.

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