A heterogeneous nucleation-induced atmospheric pressure hydrolysis method in the industrial production process of titanium dioxide by hydrochloric acid method

Abstract

The present invention discloses a method for heterogeneous nucleation-induced atmospheric pressure hydrolysis in the industrial production process of titanium dioxide by hydrochloric acid method, which comprises the following steps: (1) Pump the concentrated titanium liquid into the hydrolysis pot, start the stirrer to stir, and heat the concentrated titanium liquid to 85-90 °C; (2) Weigh NaOH and the chloride salt of the heterogeneous nucleating agent with the same mass according to the proportion of 0.05%-0.1% of tetravalent titanium, add them to the heterogeneous nucleating colloid preparation tank, add water, and stir to dissolve; (3) Immediately and rapidly add the above-mentioned stirred and dissolved solution to the concentrated titanium liquid heated in step (1), and use steam to heat up to make the hydrolysis solution slightly boil and keep warm; (4) Detect that the hydrolysis rate reaches 99%, and the hydrolysis is completed; (5) Add wood cellulose to the hydrolysis pot and stir evenly; (6) The hydrolyzed titanium dioxide hydrate slurry enters the titanium dioxide hydrate storage tank, and after natural cooling, it enters the washing process for treatment. The hydrolysis rate of the present invention is greater than 97%, the initial product of rutile titanium dioxide obtained by calcination has a particle diameter of 0.2-0.34 μm, the rutile content is greater than 99%, and the titanium dioxide content reaches 99.9%, meeting the requirements for the initial product of high-quality rutile-type titanium dioxide.

Description

Background Art

[0001] In the reported patents and research literatures on the preparation of titanium dioxide by hydrochloric acid method, there are two methods for preparing titanium liquid: one is to decompose titanium raw materials with hydrochloric acid and separate the insoluble residues. The leaching solution is subjected to reduction of ferric iron to ferrous iron, and ferrous chloride is cooled and crystallized. After separating ferrous chloride, the titanium-containing leaching solution is subjected to solvent extraction (liquid-liquid separation) to extract and separate impurities such as iron and calcium to obtain refined titanium liquid; the other is that the titanium-containing leaching solution after separating ferrous chloride is concentrated by evaporation to obtain concentrated titanium liquid. There are two methods for preparing solid-phase hydrated titanium dioxide from titanium liquid: one is that the refined titanium liquid obtained by solvent extraction (liquid-liquid separation) to extract and separate impurities such as iron and calcium is prepared into hydrated titanium dioxide by spray heating hydrolysis method; the other is that the hydrolysis process of the refined titanium liquid obtained by extraction method or the concentrated titanium liquid obtained by separating ferrous chloride and concentrating by evaporation is similar to the hot hydrolysis process of concentrated titanium liquid in sulfuric acid method, so that the titanium component is transformed from the liquid-phase titanium complex to the solid-phase hydrated titanium dioxide, thereby separating from the soluble impurities in the mother liquor, and pure hydrated titanium dioxide is obtained after washing.

[0002] The hydrated titanium dioxide is calcined, wet-ground, inorganically coated, filtered and washed, dried, air-powdered and packaged to obtain titanium dioxide products. At present, only Fujian Kuncai Materials Technology Co., Ltd. uses hydrochloric acid extraction process to produce pearlescent pigments of titanium dioxide. The rest are all in the process of experimental research and pilot-scale research.

[0003] In the existing processes of hydrolyzing and precipitating metatitanic acid in sulfuric acid process titanium white and hydrochloric acid process titanium white, in order to obtain an ideal micellized particle product of precipitated primary microcrystals, a nucleating agent, that is, hydrolysis seed crystal, needs to be added in the precipitation reaction during hydrolysis. If the self-seed hydrolysis process is adopted, the seed crystal is generated during the addition of titanium liquid. The early titanium liquid is mixed with the pre-added bottom water, and the seed crystal is generated when it is diluted; if the external seed crystal hydrolysis process is adopted, generally, an alkaline material is used to neutralize and produce titanium liquid to prepare hydrolysis seed crystal, and then added to the hydrolyzed titanium liquid. In a certain period of time at the beginning of the reaction, due to the regional inhomogeneity of the system reaction conditions, both of the above two methods have different nucleation times and growth times of crystal nuclei, resulting in different crystal nucleus particle sizes, and ultimately affecting the particle size distribution and quality of hydrated titanium dioxide. The defect of the existing hydrochloric acid titanium liquid atmospheric pressure hydrolysis technology is that the nucleation rate, particle growth rate and coagulation and agglomeration of hydrated titanium dioxide are difficult to control, the self-seed and external seed technologies are immature, the generated hydrated titanium dioxide particles are too fine, and washing and filtration are difficult, ultimately resulting in too fine titanium dioxide particles in the product, high impurity content and poor pigment performance. Summary of the Invention

[0004] The technical problems to be solved by the present invention are as follows: (1) Solve the nucleation technology to effectively control the growth rate and coagulation and agglomeration of hydrated titanium dioxide particles, and meet the requirements of pigment titanium white for the particle size and particle size distribution of hydrated titanium dioxide; (2) Solve the technical problems of difficult filtration, difficult washing, and high impurity content of hydrated titanium dioxide; (3) Propose an efficient and environmentally friendly acid recovery technology.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is: a heterogeneous nucleation-induced atmospheric pressure hydrolysis method in the industrial production process of hydrochloric acid process titanium dioxide, which includes the following steps: (1) Pump concentrated titanium liquid with Ti 3+ > 2.7 g / L, TiO 2 250 - 270 g / L, and an acidity coefficient F value of 0.72 - 0.78 into the hydrolysis pot, start the stirrer to stir, and directly heat with saturated steam to heat the concentrated titanium liquid to 85 - 90 °C; (2) Weigh NaOH and a chloride salt of a heterogeneous crystal nucleating agent of the same mass according to 0.05% - 0.1% of tetravalent titanium, add them to the heterogeneous crystal nucleus colloid preparation tank, add water, and stir to dissolve; (3) Immediately and quickly add the above-mentioned stirred and dissolved liquid to the concentrated titanium liquid heated in step (1), and use steam to heat up to make the hydrolysis liquid slightly boil and keep warm; (4) Regularly keep warm to ensure that the solid product of titanium continuously hydrolyzed - hydrated titanium dioxide (TiO 2 ·2H 2 O) reaches the hydrolysis rate required by the process, detect that the hydrolysis rate reaches 99%, and the hydrolysis is completed; (5) Add wood cellulose to the hydrolysis pot and stir evenly; (6) Stop heating, open the discharge valve of the hydrolysis pot, and the hydrolyzed hydrated titanium dioxide slurry enters the hydrated titanium dioxide storage tank, cools naturally to 60 - 65 °C, and then enters the washing process for treatment.

[0006] Preferably, the indexes of the concentrated titanium liquid are as follows: Ti 3+ : 2.73 g / L, TiO 2 : 260.18 g / L, Fe 2+ : 62.40 g / L, effective acid: 195.63 g / L, Cl - : 336.38 g / L, and the acidity coefficient F value is 0.75.

[0007] Preferably, the concentrated titanium liquid is heated to 85 °C; weigh NaOH and a chloride salt of a heterogeneous crystal nucleating agent of the same mass according to 0.05% of tetravalent titanium, and use steam to heat up to make the hydrolysis liquid slightly boil and keep warm for 30 min.

[0008] The hydrogen chloride gas and water vapor generated during the hydrolysis process are pumped to the falling film absorption system for tail gas absorption treatment, and the generated clean condensed acid is used as absorption acid in the hydrochloric acid regeneration system.

[0009] Beneficial effects

[0010] The main innovation points and effects of the present invention include:

[0011] (1) Application of heterogeneous crystal seed nucleation inducer

[0012] According to the heterogeneous nucleation theory of crystal growth in liquid phase, the present invention adopts adding a heterogeneous (non-titanium dioxide component) colloidal inducer prepared by the process of the present invention at the beginning of the hydrolysis of titanium liquid. The colloidal nanoparticles of the heterogeneous colloidal inducer have uniform particle size and high surface energy, which can effectively reduce the nucleation potential barrier of the titanium hydrolysis reaction and accelerate nucleation. The formed crystal seeds have uniform particle size, meeting the further growth requirements of hydrated titanium dioxide particles.

[0013] (2) Control technology of acidity coefficient F value (the ratio of the effective acid concentration in titanium liquid to the TiO 2 concentration: HCl / TiO 2 ) and titanium liquid concentration The F value and titanium liquid concentration affect the existence form of titanium complexes, and further affect the hydrolysis process. They are important parameters affecting the hydrolysis rate and hydrolysis rate of titanium liquid. The research of the present invention shows that: free acid can be efficiently recovered during the evaporation of the clarified titanium liquid in the previous process, while increasing the concentration of TiO 2 (TiO 2 : 250 - 270 g / L), controlling the HCl concentration in the concentrated titanium liquid to ensure the F value (0.72 - 0.78) required by the process, so that the hydrolysis reaction is very rapid. The hydrolysis rate can reach 85% in 3 - 5 minutes, and the particle size distribution of the secondary aggregates of the whole hydrated titanium dioxide is concentrated. According to the research of this process and the solution chemical analysis, it is first proposed that the suitable hydrolysis condition in the production of titanium dioxide by hydrochloric acid method is that the chloro-oxygen complex of titanium is Ti O 8 Cl 13 6 , and the hydrolysis reaction equation is:

[0014] Ti 8 O 13 Cl 6 +19H 2 O 8H 4 TiO 4 ↓+6HCl

[0015] Generating hydrated titanium dioxide solid: metatitanic acid H 4 TiO 4 (TiO 2 ·2H 2 O).

[0016] (3) Waste acid gas absorption and utilization technology

[0017] ​The hydrogen chloride gas and water vapor generated during the hydrolysis process are treated for tail gas through a falling film absorption system, which can fully achieve 100% up-to-standard discharge, and a small amount of clean condensed acid is generated and returned to the hydrochloric acid regeneration system for use as absorption acid.

[0018] (4) The hydrolysis rate is greater than 97%. After the washed hydrated titanium dioxide passes through calcination without the addition of external crystal seeds and salt treatment, the primary rutile titanium dioxide product is obtained, with a particle diameter of 0.2 - 0.34 μm, a rutile content greater than 99%, and a titanium dioxide content reaching 99.9%, meeting the requirements for the primary product of high-quality rutile-type titanium dioxide. Specific implementation mode

[0019] Example 1

[0020] The indicators of the concentrated titanium liquid are as follows, Ti 3+ : 2.73 g / L, TiO 2 : 260.18 g / L, Fe 2+ : 62.40 g / L, effective acid: 195.63 g / L, Cl - : 336.38 g / L. The acidity coefficient F value is 0.75.

[0021] Open the discharge valve of the concentrated titanium liquid storage tank and the feed liquid pump, and pump 1500 L of concentrated titanium liquid into the 2 m 3 hydrolysis pot.

[0022] Turn on the stirrer, with a rotation speed of 30 r / min, and directly heat by introducing saturated steam to heat the concentrated titanium liquid to 90 °C.

[0023] Weigh 200 g of NaOH and the same mass of chloride salt of heterogeneous crystal nuclei agent according to the proportion of 0.05% of tetravalent titanium, add them to the heterogeneous crystal nucleus colloid preparation tank with a volume of 10 L, add 2000 ml of water, and immediately and quickly add the stirred and dissolved solution to the concentrated titanium liquid at 90 °C.

[0024] Use steam to heat up to make the hydrolysis liquid slightly boil and keep it warm for 30 min; regularly keep warm to ensure that the solid product of titanium continuously generated by hydrolysis - hydrated titanium dioxide (TiO 2 ·2H 2 O) reaches the hydrolysis rate required by the process, and it is detected that the hydrolysis rate reaches 99%, and the hydrolysis is completed.

[0025] Add 200 g of wood cellulose to the hydrolysis pot and stir evenly.

[0026] Stop heating, open the discharge valve of the hydrolysis pot, and the hydrolyzed hydrated titanium dioxide slurry enters the hydrated titanium dioxide storage tank and is cooled naturally to 60 - 65 °C. Wait for the subsequent washing process to handle.

[0027] The hydrogen chloride gas and water vapor generated during the hydrolysis process are pumped to a falling film absorption system for tail gas absorption treatment, and the generated clean condensed acid is returned to the hydrochloric acid regeneration system for use as absorption acid.

[0028] In Example 1, the hydrolysis rate of titanium was 99.1%. After being washed qualified, the hydrated titanium dioxide was calcined without adding external seeds and salt treatment to obtain the primary rutile titanium dioxide product, with a particle diameter of 0.2 - 0.32 μm, a rutile content greater than 99%, and a titanium dioxide content of 99.92%, meeting the requirements for the primary product of high-quality rutile type titanium dioxide.

[0029] Example 2

[0030] The indicators of the concentrated titanium liquid are as follows: Ti 3+ : 2.73 g / L, TiO 2 : 260.18 g / L, Fe 2+ : 62.40 g / L, effective acid: 195.63 g / L, Cl - : 336.38 g / L. The acidity coefficient F value is 0.75.

[0031] Open the discharge valve of the concentrated titanium liquid storage tank and the liquid pump, and pump 1500 L of concentrated titanium liquid into the 2 m 3 hydrolysis pan.

[0032] Start the stirrer at a speed of 30 r / min, and directly heat by introducing saturated steam to heat the concentrated titanium liquid to 85 °C.

[0033] Weigh 400 g of NaOH and the same mass of chloride salt of heterogeneous nucleating agent according to the proportion of 0.1% of tetravalent titanium, add them to a heterogeneous nucleating colloid preparation tank with a volume of 10 L, add 2000 ml of water, and immediately and quickly add the mixture to the concentrated titanium liquid at 85 °C after stirring and dissolving.

[0034] Use steam to heat up to make the hydrolysis liquid slightly boil and keep it warm for 30 min; regularly keep warm to ensure that the solid product of titanium continuously generated by hydrolysis - hydrated titanium dioxide (TiO 2 ·2H 2 O) reaches the hydrolysis rate required by the process, and it is detected that the hydrolysis rate reaches 99%, and the hydrolysis is completed.

[0035] Add 200 g of wood cellulose to the hydrolysis pan and stir evenly.

[0036] Stop heating, open the discharge valve of the hydrolysis pan, and the slurry of hydrated titanium dioxide after hydrolysis enters the hydrated titanium dioxide storage tank and is cooled naturally to 60 - 65 °C. Wait for subsequent washing process treatment.

[0037] The hydrogen chloride gas and water vapor generated during the hydrolysis process are pumped to a falling film absorption system for tail gas absorption treatment, and a small amount of clean condensed acid is generated and returned to the hydrochloric acid regeneration system for use as absorption acid.

[0038] In Example 2, the hydrolysis rate of titanium is 99.3%. After the washed and qualified hydrated titanium dioxide is calcined without adding external seeds and salt treatment, the primary rutile titanium dioxide product is obtained, with a particle diameter of 0.2 - 0.34 μm, a rutile content of more than 99%, and a titanium dioxide content of 99.90%, meeting the requirements for the primary product of high-quality rutile-type titanium dioxide.

[0039] The temperatures at which the heterogeneous nucleating agent is added to the hydrolysis system in Comparative Example 1 and Example 2 are different. The temperature in Example 1 is 90 °C, and the temperature in Example 2 is 85 °C.

[0040] The addition amounts of NaOH and the heterogeneous nucleating agent in Example 1 and Example 2 are different. The addition amounts in Example 1 are 0.05% of tetravalent titanium respectively, and the addition amounts in Example 2 are 0.1% of tetravalent titanium respectively.

[0041] The above are only the embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent process transformation made using the content of the specification of the present invention, or directly or indirectly applied in other related technical fields, shall be similarly included in the patent protection scope of the present invention.

Claims

1. A method of heterogeneous nucleation-induced atmospheric pressure hydrolysis in the industrial production process of titanium dioxide by hydrochloric acid method, which comprises the following steps: (1) Pump the concentrated titanium solution with Ti 3+ > 2.7 g / L, TiO 2 250 - 270 g / L and an acidity coefficient F value of 0.72 - 0.78 into the hydrolysis pot, start the agitator to stir, and directly heat by introducing saturated steam to heat the concentrated titanium solution to 85 - 90 °C; (2) Weigh NaOH and the chloride salt of the same mass of heterogeneous nucleating agent according to the ratio of 0.05% - 0.1% of tetravalent titanium, add them to the heterogeneous nucleating colloid preparation tank, add water, and stir to dissolve; (3) Immediately and rapidly add the stirred and dissolved solution to the concentrated titanium solution heated in step (1), and use steam to heat up to the hydrolysis solution boiling slightly and keep it warm; (4) Keep the temperature constant regularly to ensure that the solid product of titanium produced by continuous hydrolysis - hydrated titanium dioxide reaches the hydrolysis rate required by the process, detect that the hydrolysis rate reaches 99%, and the hydrolysis is completed; (5) Add wood cellulose to the hydrolysis pot and stir evenly; (6) Stop heating, open the discharge valve of the hydrolysis pot, and the hydrolyzed hydrated titanium dioxide slurry enters the hydrated titanium dioxide storage tank, cools naturally to 60 - 65 °C, and then enters the washing process for treatment.

2. The method according to claim 1, wherein the indexes of the thick titanium solution are as follows: Ti 3+ : 2.73 g / L, TiO 2 : 260.18 g / L, Fe 2+ : 62.40 g / L, effective acid: 195.63 g / L, Cl - : 336.38 g / L, and the acidity coefficient F value is 0.

75.

3. For the method according to claim 1, the concentrated titanium solution is heated to 85 °C.

4. For the method according to claim 1, NaOH is weighed according to 0.05% of tetravalent titanium and the chloride salt of the same mass of heterogeneous nucleating agent.

5. For the method according to claim 1, it is heated to boiling slightly and kept warm for 30 min by using steam.

6. For the method according to claim 1, the hydrogen chloride gas and water vapor generated during the hydrolysis process are pumped to the falling film absorption system for tail gas absorption treatment, and the generated clean condensed acid is used as absorption acid in the hydrochloric acid regeneration system.

7. For the method according to claim 6, the hydrated titanium dioxide after qualified washing is calcined to obtain the primary rutile titanium dioxide product, with a particle diameter of 0.2 - 0.34 μm, rutile content greater than 99%, and titanium dioxide content of 99.90%.

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