Method for utilizing hydrochloric acid produced as a byproduct of titanium dioxide chloride

Abstract

The invention discloses a method for utilizing hydrochloric acid produced as a byproduct of titanium dioxide chloride, comprising the following steps: S1, placing the hydrochloric acid produced as a byproduct of titanium dioxide chloride in an environment of 4-10 DEG C for sedimentation for 0.5-1 day to obtain a supernatant; S2, filtering the supernatant using a dynamic shallow filter at a filtration rate of 50-150 ml / min to obtain a suspension and a hydrochloric acid supernatant; S3, heating the hydrochloric acid supernatant to 40-50 DEG C, adding a phosphoric acid solution with a mass concentration of 80%-98% and mixing evenly to obtain a solid-liquid mixture; wherein the mass ratio of the phosphoric acid solution in terms of phosphoric acid to the hydrochloric acid produced as a byproduct of titanium dioxide chloride in terms of TiO2 is 2-4:1; S4, solid-liquid separation of the solid-liquid mixture to obtain a filter cake and recycled hydrochloric acid, and the filter cake is washed with pure water, dried, and roasted to obtain a titanium phosphate product. Its advantages are: it realizes the comprehensive utilization of hydrochloric acid produced as a by-product of titanium dioxide chloride, and no wastewater is discharged during the treatment process; the process flow is simple, the reaction conditions are mild, the comprehensive energy consumption is low, and it has good promotion prospects.

Description

Technical Field

[0001] The invention relates to a production technology of titanium dioxide by a chloride process, in particular to a technology for treating byproducts of titanium dioxide by a chloride process. Background Art

[0002] Titanium dioxide (TiO2) is considered to be the best white pigment in the world. It has high hiding power, weather resistance, and decolorization performance. It is widely used in fine chemical industries such as coatings, plastics, papermaking, printing inks, chemical fibers, rubber, ceramics, cosmetics, food, and medicine. Currently, there are two main methods for producing titanium dioxide: sulfuric acid method and chlorination method.

[0003] The sulfuric acid method is to produce titanium sulfate by acid hydrolysis of ferrotitanium powder and concentrated sulfuric acid, and then generate metatitanic acid through hydrolysis, and then obtain titanium dioxide products through calcination and crushing. The advantages of this process are that it can use cheap and easily available ilmenite and sulfuric acid as raw materials, the technology is relatively mature, the equipment is simple, and the anti-corrosion materials are easy to solve. Its disadvantages are that the process is long, it can only be mainly operated intermittently, it is a wet operation, the consumption of sulfuric acid and water is high, there are many wastes and by-products, and it is highly polluting to the environment.

[0004] The chlorination method is to mix rutile, titanium concentrate or high-titanium slag powder with coke and then carry out high-temperature chlorination to produce refined titanium tetrachloride. After distillation and vanadium removal, high-temperature oxidation, classification, surface treatment, and then filtering, washing, drying, and crushing to obtain titanium dioxide products. Its advantages are short process, easy expansion of production capacity, high degree of continuous automation, relatively low energy consumption, less "three wastes", etc. Due to its advantages in environmental protection and product quality, the chlorination method has become the direction of industrial upgrading of the domestic titanium dioxide industry.

[0005] In the production of titanium dioxide chloride, the chlorinated tail gas after three-stage condensation contains N2, TiCl4, HCl, CO, and CO2. When the chlorination furnace condition control is not ideal, the tail gas will inevitably contain Cl2, and the tail gas needs to be treated before it can be discharged. After the tail gas treatment, 20wt% to 30wt% of by-product hydrochloric acid will be obtained, that is, the by-product hydrochloric acid of titanium dioxide chloride described in the present invention. At present, about 0.4 to 0.5t of by-product hydrochloric acid will be produced for every 1t of titanium dioxide chloride produced. Since the by-product hydrochloric acid contains about 1wt% to 2wt% of TiOCl2, TiOCl2 will be hydrolyzed into fine-grained TiO2 during the reduction of acid concentration or long-term placement, making the hydrochloric acid solution appear milky white, which greatly limits the application field of by-product hydrochloric acid of titanium dioxide chloride. In addition, since the by-product hydrochloric acid also contains a small amount of orthosilicic acid, it will block the filter medium when filtering the by-product hydrochloric acid, further limiting the utilization of the by-product hydrochloric acid.

[0006] At present, the treatment method of hydrochloric acid produced as a byproduct of titanium dioxide chloride is usually lime neutralization, that is, using alkaline substances such as calcium hydroxide, such as calcium carbide slag or lime powder, to neutralize the byproduct hydrochloric acid and then landfill; this method causes waste of resources and environmental pollution, and does not meet the national goal of "harmless, reduced, and resource-based" byproduct waste resources. Therefore, it is necessary to develop relevant technologies to solve the problem of the difficulty in recycling hydrochloric acid produced as a byproduct of titanium dioxide chloride. Summary of the invention

[0007] In order to solve the problem that hydrochloric acid produced as a by-product of titanium dioxide chloride is difficult to recycle, the present invention provides a method for utilizing hydrochloric acid produced as a by-product of titanium dioxide chloride.

[0008] The technical solution adopted by the present invention is: a method for utilizing hydrochloric acid produced as a by-product of titanium dioxide chloride, comprising the following steps:

[0009] S1. Place the measured amount of hydrochloric acid produced as a by-product of titanium dioxide chloride in an environment of 4 to 10° C. and let it settle for 0.5 to 1 day to obtain a supernatant;

[0010] S2, filtering the supernatant using a dynamic shallow filter at a filtration rate of 50 to 150 ml / min to obtain a suspension and a hydrochloric acid clear solution;

[0011] S3, heating the hydrochloric acid solution to 40-50° C., adding a phosphoric acid solution with a mass concentration of 80%-98% and mixing evenly to obtain a solid-liquid mixture; wherein the mass ratio of the phosphoric acid solution in terms of phosphoric acid to the hydrochloric acid produced as a byproduct of titanium dioxide chloride in terms of TiO2 is 2-4:1;

[0012] S4, solid-liquid separation of the solid-liquid mixture to obtain a filter cake and recycled hydrochloric acid, the filter cake is washed with pure water, dried and roasted to obtain a titanium phosphate product.

[0013] Analysis of hydrochloric acid produced as a byproduct of titanium dioxide chloride shows that it contains 1wt% to 2wt% of TiOCl2 and a small amount of orthosilicic acid, which limits the utilization of hydrochloric acid. The present invention reduces the solid matter content in hydrochloric acid by low-temperature sedimentation, further reduces the solid matter content by a dynamic shallow filter, and finally prepares titanium phosphate by the reaction of phosphoric acid and TiOCl2 in hydrochloric acid. The hydrochloric acid after impurity removal is used to prepare artificial rutile or acid-hydrolyzed titanium liquid, thereby realizing the comprehensive utilization of byproduct hydrochloric acid. The present invention is realized by the following principles:

[0014] The hydrochloric acid produced as a by-product of titanium dioxide chloride settles in a low-temperature environment for 0.5 to 1 day, and titanic acid and hydrolyzed TiO2 will gradually settle in the lower layer of the tank. The clear liquid in the upper layer is pumped to a dynamic shallow filter by a diaphragm pump for fine filtration to further remove solid matter in the acid (mainly titanic acid, TiO2, and orthosilicic acid); the filtered hydrochloric acid clear liquid is heated and added with a phosphoric acid solution, and stirred to obtain a solid-liquid mixture, which is then filtered conventionally to obtain recycled hydrochloric acid and a filter cake. The filter cake can be washed with pure water, dried, and roasted to obtain titanium phosphate; the recycled hydrochloric acid can be used for acid leaching of titanium concentrate to prepare artificial rutile or titanium-containing mother liquor due to its greatly reduced solid content.

[0015] As a further improvement of the present invention, the dynamic shallow filter adopts a variable aperture filter disc with a pore size of 10μm to 0.1μm from the outside to the inside. The dynamic shallow filter used in the present invention can filter the by-product hydrochloric acid well because the device combines the swirl shear mechanism and the microporous filtration method, and its internal parts adopt a variable aperture filter disc with a pore size of 10μm to 0.1μm from the outside to the inside, which has the characteristics of small holes and multiple holes that change along the flow direction and a large specific surface area; under the action of mechanical stirring, the filter residue on the surface of the filter material is automatically cleaned by flow field shear, thereby maintaining the filtering activity of the filter material. At the same time, the variable aperture design of the internal material can intercept particulate matter in the shallow layer of the filter material, and then through backwashing, it is easy to achieve the purpose of deep cleaning of the filter material.

[0016] As a further improvement of the present invention, the calcination temperature of step S4 is 400-500° C., and the calcination time is 0.5-1.5 h.

[0017] The invention also discloses a method for producing titanium dioxide chloride, which is characterized by comprising a method for utilizing the by-product hydrochloric acid produced by the titanium dioxide chloride of the invention.

[0018] The beneficial effects of the present invention are as follows: 1) by cooling down, the precipitation of metatitanic acid and orthosilicic acid is promoted, the solid impurity content in hydrochloric acid during filtration is reduced, and the single use time of the filter is extended; 2) the fine filtration device adopts a dynamic shallow filter, and its internal filter material adopts a variable aperture filter disc with an aperture of 10μm to 0.1μm from the outside to the inside, so as to achieve the gradual interception of solid particulate matter of different particle sizes; the filter disc is driven to rotate by a variable frequency motor with a frequency of 30HZ to 40HZ, and the rotation shear force is used to reduce the adhesion of solid particles, thereby increasing the single use time of the fine filtration device. 3) For the first time, a dynamic shallow filter is used to treat hydrochloric acid produced as a byproduct of titanium dioxide chloride, and the impurity content in the byproduct hydrochloric acid is further reduced by fine treatment; 4) by adding phosphoric acid to the hydrochloric acid after fine filtration to react and prepare titanium phosphate, titanium recovery is achieved; 5) the process flow of the present invention is simple, the reaction conditions are mild, and it is extensive, which can effectively solve the problem of the utilization of hydrochloric acid produced as a byproduct of titanium dioxide chloride, and has good promotion prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0020] The present invention is further described below in conjunction with embodiments.

[0021] Embodiment 1:

[0022] The hydrochloric acid produced as a byproduct of 1# titanium dioxide chloride is recycled as follows:

[0023] S1. Place 15L of hydrochloric acid produced as a byproduct of titanium dioxide chloride with a mass concentration of 23% in a refrigerator fresh-keeping room at 5°C for 1 day;

[0024] S2. Use a diaphragm pump to draw the upper clear liquid at a speed of 50 mL / min into a dynamic shallow filter. The motor rotates at a frequency of 30 Hz to filter the upper clear liquid to obtain a suspension and a hydrochloric acid clear liquid. The dynamic shallow filter uses a variable aperture filter disc with an aperture of 10 μm to 0.1 μm from the outside to the inside.

[0025] S3, heating the hydrochloric acid solution to 40°C, adding a phosphoric acid solution with a mass concentration of 80%, stirring for 10 minutes, and obtaining a solid-liquid mixture; wherein the mass ratio of the phosphoric acid solution in terms of phosphoric acid to the hydrochloric acid produced as a byproduct of titanium dioxide chloride in terms of TiO2 is 4:1;

[0026] S4, solid-liquid separation of the solid-liquid mixture to obtain a filter cake and recycled hydrochloric acid, the filter cake is washed with pure water, dried, and calcined at 450° C. for 1 h to obtain a titanium phosphate product.

[0027] The components of the recycled hydrochloric acid and titanium phosphate products were tested, and the results are shown in Table 1.

[0028] Embodiment 2:

[0029] The hydrochloric acid produced as a byproduct of 2# titanium dioxide chloride is recycled as follows:

[0030] S1. Place 15L of hydrochloric acid produced as a byproduct of titanium dioxide chloride with a mass concentration of 27% in a refrigerator fresh-keeping room at 5°C for 1 day;

[0031] S2. Use a diaphragm pump to draw the upper clear liquid at a speed of 100 mL / min into a dynamic shallow filter. The motor rotates at a frequency of 40 Hz to filter the upper clear liquid to obtain a suspension and a hydrochloric acid clear liquid. The dynamic shallow filter uses a variable aperture filter disc with an aperture of 10 μm to 0.1 μm from outside to inside.

[0032] S3, heating the hydrochloric acid solution to 40°C, adding a phosphoric acid solution with a mass concentration of 85%, stirring for 10 minutes, and obtaining a solid-liquid mixture; wherein the mass ratio of the phosphoric acid solution in terms of phosphoric acid to the hydrochloric acid produced as a byproduct of titanium dioxide chloride in terms of TiO2 is 3:1;

[0033] S4, solid-liquid separation of the solid-liquid mixture to obtain a filter cake and recycled hydrochloric acid, the filter cake is washed with pure water, dried, and calcined at 450° C. for 1 h to obtain a titanium phosphate product.

[0034] The components of the recycled hydrochloric acid and titanium phosphate products were tested, and the results are shown in Table 1.

[0035] Embodiment three:

[0036] The hydrochloric acid produced as a byproduct of 3# titanium dioxide chloride is recycled as follows:

[0037] S1. Place 15L of hydrochloric acid produced as a byproduct of titanium dioxide chloride with a mass concentration of 24% in a refrigerator fresh-keeping room at 5°C for 1 day;

[0038] S2. Use a diaphragm pump to draw the upper clear liquid at a speed of 150 mL / min into a dynamic shallow filter. The motor rotates at a frequency of 50 Hz to filter the upper clear liquid to obtain a suspension and a hydrochloric acid clear liquid. The dynamic shallow filter uses a variable aperture filter disc with an aperture of 10 μm to 0.1 μm from the outside to the inside.

[0039] S3, heating the hydrochloric acid solution to 40°C, adding a phosphoric acid solution with a mass concentration of 98%, stirring for 10 minutes, and obtaining a solid-liquid mixture; wherein the mass ratio of the phosphoric acid solution in terms of phosphoric acid to the hydrochloric acid produced as a byproduct of titanium dioxide chloride in terms of TiO2 is 3:1;

[0040] S4, solid-liquid separation of the solid-liquid mixture to obtain a filter cake and recycled hydrochloric acid, the filter cake is washed with pure water, dried, and calcined at 450° C. for 1 h to obtain a titanium phosphate product.

[0041] The components of the recycled hydrochloric acid and titanium phosphate products were tested, and the results are shown in Table 1.

[0042] Table 1 Composition test results of recycled hydrochloric acid and titanium phosphate products

[0043]

Claims

1. A method for utilizing hydrochloric acid produced as a byproduct of titanium dioxide chloride, comprising the following steps: S1. Place the measured hydrochloric acid produced as a byproduct of titanium dioxide chloride in an environment of 4 to 10° C. and let it settle for 0.5 to 1 day to obtain a supernatant; the mass concentration of hydrochloric acid in the hydrochloric acid produced as a byproduct of titanium dioxide chloride is 20% to 30%; S2. Filter the supernatant using a dynamic shallow filter at a filtration rate of 50 to 150 ml / min to obtain a suspension and a hydrochloric acid clear solution; S3, heating the hydrochloric acid solution to 40-50°C, adding a phosphoric acid solution with a mass concentration of 80%-98% and mixing evenly to obtain a solid-liquid mixture; wherein, The mass ratio of phosphoric acid solution calculated as phosphoric acid to hydrochloric acid produced as a byproduct of titanium dioxide chloride calculated as TiO2 is 2 to 4:1; S4, solid-liquid separation of the solid-liquid mixture to obtain a filter cake and recycled hydrochloric acid, the filter cake is washed with pure water, dried and roasted to obtain a titanium phosphate product.

2. The method for utilizing hydrochloric acid produced as a byproduct of titanium dioxide chloride according to claim 1, characterized in that: The recycled hydrochloric acid is used for acid leaching of titanium concentrate to prepare artificial rutile or titanium-containing mother liquor.

3. The method for utilizing hydrochloric acid produced as a by-product of titanium dioxide chloride according to claim 1, characterized in that: The dynamic shallow filter uses a variable aperture filter disc with an aperture ranging from 10 μm to 0.1 μm from the outside to the inside.

4. The method for utilizing hydrochloric acid produced as a byproduct of titanium dioxide chloride according to claim 1, characterized in that: The calcination temperature of step S4 is 400-500° C., and the calcination time is 0.5-1.5 h.

5. A method for producing titanium dioxide chloride, characterized in that: A method for utilizing hydrochloric acid produced as a by-product of titanium dioxide chloride as described in any one of claims 1 to 4.

Images