A method for hydrolyzing high-F-value titanium liquid, and the hydrolyzed material and titanium dioxide.

Abstract

This invention discloses a method for hydrolyzing high-F-value titanium liquid, as well as the hydrolyzed material and titanium dioxide, comprising the following steps: S1. Preparing the hydrolyzed titanium liquid and heating it; preparing seed crystal preparation titanium liquid and alkaline solution; S2. When the hydrolyzed titanium liquid reaches 80-85℃, heating the seed crystal preparation titanium liquid and the alkaline solution to 50-60℃ respectively; S3. Adding the seed crystal preparation titanium liquid to the alkaline solution, heating to 92-95℃, and maintaining the temperature until the final stability of the hydrolyzed seed crystals is 90-100ml, at which point the preparation of the hydrolyzed seed crystals is complete; S4. Stopping the heating when the temperature of the hydrolyzed titanium liquid reaches 92-95℃, adding the prepared hydrolyzed seed crystals, and stirring; S5. Heating the hydrolyzed titanium liquid to boiling, maintaining a gentle boil, and when the hydrolyzed titanium liquid turns white, adding dilution water until the hydrolysis is complete. The prepared hydrolyzed seed crystals have uniform grain size, the hydrolyzed material has uniform particle size, the hydrolysis quality of the high-F-value hydrolyzed titanium liquid is high, and the water washing time is short.

Description

Technical Field

[0001] This invention relates to the field of titanium dioxide production, and in particular to a method for hydrolyzing high-F-value titanium liquid, as well as the hydrolyzed material and titanium dioxide. Background Technology

[0002] Hydrolysis is a crucial step in the production of titanium dioxide using the sulfuric acid process. It directly determines the quality of metatitanic acid and ultimately the quality of the titanium dioxide product. Most manufacturers use an external seed crystal hydrolysis process, which involves reacting alkali with liquid titanium to prepare hydrolyzed seed crystals.

[0003] Titanium liquor is prepared by acid leaching of ilmenite or high-titanium slag. Due to the instability of the ore source, the acid-leached titanium liquor initially produced during the ore change process often exhibits a high F-value. Adjustments to the acid leaching process parameters are necessary to bring the F-value within acceptable limits. Furthermore, the high F-value titanium liquor produced during the initial ore change process, when processed using normal hydrolysis techniques, will result in poor-quality metatitanic acid. This leads to a low hydrolysis rate, finer metatitanic acid particle size, and slow washing speed, all of which negatively impact the washing performance. Additionally, the metatitanic acid prepared by this method is not heat-resistant, consequently affecting the whiteness and decolorizing power of the final product.

[0004] The existing hydrolysis process is as follows: ① Preparation of hydrolytic seed crystals: Prepare titanium liquid and alkaline solution (titanium liquid to alkaline solution weight ratio of 6.4:1). Heat the titanium liquid and alkaline solution to 85℃ respectively. Add the alkaline solution to the titanium liquid within 3-4 minutes, continue heating to 96℃, and maintain the temperature for ripening. The hydrolytic seed crystals are then prepared, and the final stability of the hydrolytic seed crystals is 110-120 ml. ② Titanium liquid hydrolysis: Prepare titanium liquid and heat it to 96℃. Place the prepared hydrolytic seed crystals into a titanium liquid preheating tank. The amount of hydrolytic seed crystals added (based on TiO2) is 2.1%. Stir for 15 minutes, then transfer the titanium liquid from the preheating tank into the hydrolysis tank. Heat to the first boiling point. When the titanium liquid turns bluish-gray, stop heating for 30 minutes, then continue heating to the second boiling point and maintain boiling for 3 hours. Hydrolysis is then complete. Stop heating, add dilution water, and discharge the material into a cooling tank. The parameters of the titanium liquid used in the existing hydrolysis process for seed preparation and hydrolysis are as follows: TiO2: 190-200 g / l, F value: 1.9-2.0, trivalent titanium: 1-4 g / l, Fe / TiO2: 0.25-0.33, and stability: 500 ml.

[0005] Patent CN 111892084 A discloses a method for preparing metatitanic acid by hydrolysis of low-concentration titanium liquid. The method involves preheating the titanium liquid in a high-level tank before placing it into a hydrolysis tank; heating the titanium liquid in a seed crystal metering tank while preheating a sodium hydroxide solution in the seed crystal preparation tank; adding the preheated titanium liquid to the seed crystal preparation tank and stopping heating at a certain temperature; and adding the seed titanium liquid to the hydrolysis tank when its activity is less than a set value. The titanium liquid and seed crystals in the hydrolysis tank are mixed under stirring and then heated to boiling. After color detection, steam is stopped, and the stirring speed is simultaneously reduced. A second heating to boiling is performed, followed by stopping the heating and maintaining the temperature until hydrolysis is complete. The metatitanic acid obtained from the titanium liquid hydrolysis is then processed to obtain crude rutile with pigment properties. This invention targets low-concentration titanium liquid (concentration: 180-185 g / L), controlling its F value at 2.5-2.7 and the iron-titanium mass ratio at 0.5-0.8.

[0006] Patent CN105883913 A discloses a method for atmospheric pressure-induced hydrolysis of high-concentration titanium liquid with added seed crystals. The method involves preparing the added seed crystals and inducing hydrolysis at atmospheric pressure using high-concentration titanium liquid: heating the high-concentration titanium liquid to 95°C, adding the hydrolyzed seed crystals to the concentrated titanium liquid, raising the titanium liquid to a first boil until the liquid turns gray, stopping stirring and heating, allowing it to mature for 30 minutes, resuming stirring and heating, raising the temperature to a second boil within 20 minutes, and maintaining boiling for 20 minutes; maintaining boiling while controlling the flow rate, adding calculated dilution water within 2 hours, and maintaining boiling for another 70 minutes to complete the hydrolysis. Patent CN105883913 A addresses the high-concentration titanium liquid by adding dilution water within 20 minutes after the second boil, resulting in a hydrolyzed material particle size (D50) of 0.6-0.7 μm, which is relatively fine and may affect the washing time of the hydrolyzed material. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a method for hydrolyzing high-F-value titanium liquid and hydrolyzed material, which addresses the shortcomings of the existing technology. The prepared hydrolyzed seed crystals are uniform in size, the hydrolyzed material has uniform particle size, the hydrolysis quality of the high-F-value titanium liquid is high, and the water washing time is short.

[0008] The present invention also provides a titanium dioxide product with good whiteness and bleaching power.

[0009] To solve the above-mentioned technical problems, the technical solution adopted in this invention is a hydrolysis method for high F-value titanium liquid, comprising the following steps:

[0010] S1. Prepare the titanium hydrolysis solution and heat it; also prepare the titanium seed solution and alkaline solution for crystal preparation.

[0011] S2. When the hydrolyzed titanium solution is heated to 80-85°C, the seed titanium solution and the alkaline solution are heated to 50-60°C respectively.

[0012] S3. Add alkaline solution to the titanium solution for seed crystal preparation within 5-8 minutes, heat to 92-95℃, and keep it at this temperature until the final stability of the hydrolyzed seed crystal is 90-100ml. The preparation of the hydrolyzed seed crystal is then complete.

[0013] S4. Stop heating when the temperature of the hydrolyzed titanium solution reaches 92-95℃, add the hydrolyzed seed crystals prepared in S3, stir, and pump the hydrolyzed titanium solution into the hydrolysis tank;

[0014] S5. Heat the hydrolyzed titanium solution in the hydrolysis tank to boiling, maintain a gentle boil, and wait until the hydrolyzed titanium solution turns white. Then add dilution water until the hydrolysis is complete.

[0015] In a preferred embodiment of the present invention, the F-values ​​of both the hydrolyzed titanium solution and the seed-prepared titanium solution in S1 are 2.2-2.8.

[0016] In a preferred embodiment of the present invention, the volume ratio of the hydrolyzed titanium solution and the seed-prepared titanium solution in S1 is 100:(2.3-2.6); the concentration (calculated as TiO2) of both the hydrolyzed titanium solution and the seed-prepared titanium solution in S1 is 195-205 g / L; the alkaline solution in S1 is a sodium hydroxide solution or a potassium hydroxide solution, and the concentration of the alkaline solution is 95-105 g / L.

[0017] In a preferred embodiment of the present invention, the weight ratio of the titanium solution (calculated as TiO2) to the alkaline solution in S1 is (2-5):1. In this invention, if the weight ratio of the titanium solution to the alkaline solution is too high, the number of hydrolyzed seeds prepared will be insufficient, because a high F value in the titanium solution indicates high acidity, resulting in more alkali consumption during the reaction with the acid; consequently, fewer crystal nuclei will form. If the weight ratio of the titanium solution to the alkaline solution is too low, the stability of the prepared hydrolyzed seeds will be affected. An excess of titanium solution also serves to stabilize the seeds.

[0018] Because the hydrolyzed titanium solution has a large volume and a long heating time, while the seed crystal preparation time is short, to ensure smooth transitions during production and maintain the seed crystal activity, in this invention, during step S2, when the hydrolyzed titanium solution reaches 80-85°C, the seed crystal preparation titanium solution and the alkaline solution are respectively heated to 50-60°C to prepare hydrolyzed seed crystals. At this point, after the hydrolyzed seed crystal preparation is complete, the preheated temperature of the hydrolyzed titanium solution is just right for adding the seed crystals. The preheating temperature of the seed crystal preparation titanium solution and the alkaline solution to 50-60°C is crucial; the temperature cannot be too high because the high-F-value seed crystal preparation titanium solution has a high acid concentration, and a high temperature will increase the intensity of the reaction and accelerate the reaction rate, resulting in excessively rapid formation of hydrolyzed seed crystals, leading to excessively fine and unevenly sized seed crystals. Conversely, if the seed crystal preparation temperature is too low, the reaction rate during seed crystal preparation will be slow, affecting production efficiency.

[0019] In this invention, in step S3, the titanium solution for seed crystal preparation is added to the alkaline solution within 5-8 minutes. If the time for adding the alkaline solution to the titanium solution for seed crystal preparation is too short, the reaction rate is too fast, especially in high-F value titanium solution where the acid concentration is high, resulting in an overly vigorous reaction and the formation of irregular hydrolyzed seed crystals. If the time for adding the alkaline solution to the titanium solution for seed crystal preparation is too long, the seed crystals will have varying sizes due to differences in the concentrations of the titanium solution and alkaline solution at different stages.

[0020] In this invention, the final stability of the hydrolyzed seed crystals in S3 is 90-100 ml. When hydrolyzing titanium liquid with a high F value, the hydrolyzed seed crystals with a stability of 90-100 ml have the best activity.

[0021] In a preferred embodiment of the present invention, the weight ratio of the hydrolyzed seed crystals to the hydrolyzed titanium solution (calculated as TiO2) in S4 is (2.3-2.6):100, to ensure the hydrolysis quality of the high F-value hydrolyzed titanium solution.

[0022] In this invention, during the hydrolysis of the high-F-value hydrolyzed titanium solution in step S5, the high acidity inhibits the hydrolysis of TiOSO4, resulting in a slow hydrolysis rate. Therefore, the hydrolyzed titanium solution continues to boil after the first boil. To accelerate the hydrolysis of the high-F-value hydrolyzed titanium solution, dilution water (deionized water in this invention) is added after the solution turns white. This is to promote the hydrolysis of TiOSO4 in the solution and ensure the hydrolysis rate of the high-F-value hydrolyzed titanium solution. (In this invention, water is added after the solution turns white to promote the hydrolysis of TiOSO4; if water is added before step S5, the concentration of the solution will decrease, resulting in coarse metatitanic acid particles that affect the pigment performance of the final product). The rate of water addition in step S5 should not be too fast, otherwise material overflow may occur. In a preferred embodiment of this invention, the dilution water is added in step S5 for 3 hours, and the volume ratio of the dilution water to the hydrolyzed titanium solution in step S5 is 1:(6-10).

[0023] In a preferred embodiment of the present invention, the temperature for maintaining a slight boiling point in S5 is 105-107°C.

[0024] The present invention also discloses a hydrolyzed material prepared by the high F-value titanium liquid hydrolysis method, wherein the particle size D50 of the hydrolyzed material is 1.8-1.9 μm and the hydrolysis rate of the hydrolyzed material is 95.5-97%.

[0025] This invention also discloses a titanium dioxide produced using the aforementioned hydrolyzed material, characterized in that the quality index of the titanium dioxide is: L * :98.70—98.80、b * 1.36-1.50, tinting strength: >110%.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] (1) By adjusting the weight ratio of the hydrolyzed seed crystals to the alkali solution, the quantity and quality of the high-F-value seed crystals used to prepare the titanium solution and the alkali solution used to prepare the hydrolyzed seed crystals are ensured.

[0028] (2) Control the time when the seed crystal preparation titanium solution is added to the alkaline solution. This can control the reaction rate between the high F value seed crystal preparation titanium solution TiOSO4 and the alkaline solution, so that the prepared hydrolyzed seed crystals are uniform.

[0029] (3) Reduce the preheating temperature of the titanium solution and alkali solution for seed preparation, control the reaction rate of the titanium solution and alkali solution for high F-value seed preparation, ensure that the prepared hydrolyzed seed particles are uniform in size, and thus control the particle size of the hydrolyzed material.

[0030] (4) After the hydrolyzed titanium solution boils once, continue to boil gently until the hydrolyzed titanium solution turns white. Then add dilution water. This is to promote the hydrolysis of TiOSO4 by adding dilution water, in order to improve the hydrolysis quality of high F value hydrolyzed titanium solution. Detailed Implementation

[0031] Example 1

[0032] (1) Take 80m 3 Hydrolyzed titanium solution, 1.84m 3 Titanium liquid prepared by seed crystal, 0.818m 3 NaOH solution. The parameters for the hydrolyzed titanium solution and the seed-prepared titanium solution are: TiO2: 200 g / L, F value: 2.2, trivalent titanium 2.3 g / L, Fe / TiO2: 0.30, stability (500 ml).

[0033] 80m 3 The hydrolyzed titanium solution was pumped into the preheating tank, and stirring was started. The temperature was raised after the pumping was complete. Simultaneously, 1.84 m³ of the solution was pumped in. 3 The titanium solution for seed crystal preparation is transferred to the titanium solution tank, and 0.818 ml of a 100 g / L NaOH solution is pumped in. 3 Pour the solution into the alkali tank and start stirring.

[0034] (2) When the temperature of the hydrolyzed titanium solution in the preheating tank reaches 83°C, the seed titanium solution and NaOH solution are heated to 60°C respectively.

[0035] (3) Add the titanium solution for seed crystal preparation to the alkaline solution tank at 5 minutes and 30 seconds, heat it to 95°C, and maintain this temperature. When the final stability of the hydrolyzed seed crystal is 90 ml, the preparation of the hydrolyzed seed crystal is completed.

[0036] (4) When the temperature of the hydrolyzed titanium liquid in the preheating tank reaches 95°C, stop heating, add all the hydrolyzed seed crystals prepared in step 3, stir for 15 minutes, and then pump the hydrolyzed titanium liquid into the hydrolysis tank.

[0037] (5) Heat the titanium hydrolysate in the hydrolysis tank to boiling, and maintain it at 105℃ until it turns white. Add 10m 3 Diluent was added, and the dilution time was 3 hours. Hydrolysis was then complete, and the hydrolyzed material was obtained. The total hydrolysis time was 5.5 hours.

[0038] (6) Place the hydrolyzed material in a cooling tank. Take a sample of the hydrolyzed material for testing. The hydrolysis rate is 96.1%. The particle size of the hydrolyzed material is tested, and the D50 is 1.85 μm. Filter the hydrolyzed material through a Buchner funnel using a vacuum pump. After the hydrolyzed material forms a filter cake, add 1000 ml of deionized water to wash it and remove impurities. The washing time is 20 minutes and 30 seconds. Press the filter cake dry after removing impurities, add deionized water, slurry it, bleach it, add a salt treatment agent, calcine it, and pulverize it to obtain titanium dioxide. The color index of titanium dioxide is: L. * 98.72,b * :1.36, tinting strength: 112%.

[0039] Example 2

[0040] (1) Take 80m 3 Hydrolyzed titanium solution, 1.84m 3 Titanium liquid prepared by seed crystal preparation, 1.05m 3 KOH solution. The parameters for the hydrolyzed titanium solution and the seed-prepared titanium solution are: TiO2: 200 g / L, F value: 2.4, trivalent titanium 2.3 g / L, Fe / TiO2: 0.30, stability (500 ml).

[0041] 80m 3 The hydrolyzed titanium solution was pumped into the preheating tank, and stirring was started. The temperature was raised after the pumping was complete. Simultaneously, 1.84 m³ of the solution was pumped in. 3 The titanium solution for seed crystal preparation is transferred to the titanium solution tank, and 1.05 ml of a 100 g / L KOH solution is pumped in. 3 Pour the solution into the alkali tank and start stirring.

[0042] (2) When the temperature of the hydrolyzed titanium solution in the preheating tank reaches 83°C, the seed titanium solution and KOH solution are heated to 55°C respectively.

[0043] (3) Add the titanium solution for seed crystal preparation to the alkaline solution tank at 6 minutes and 18 seconds, heat it to a constant temperature of 95°C, and maintain this temperature. When the final stability of the hydrolyzed seed crystal is 90 ml, the preparation of the hydrolyzed seed crystal is completed.

[0044] (4) When the temperature of the hydrolyzed titanium liquid in the preheating tank reaches 95°C, stop heating, add all the hydrolyzed seed crystals prepared in step 3, stir for 15 minutes, and then pump the hydrolyzed titanium liquid into the hydrolysis tank.

[0045] (5) Heat the titanium hydrolysate in the hydrolysis tank to boiling, and maintain it at 105℃ until it turns white. Add 13m 3 Diluent was added, and the dilution time was 3 hours. Hydrolysis was then complete, and the hydrolyzed material was obtained. The total hydrolysis time was 5.5 hours.

[0046] (6) Place the hydrolyzed material into a cooling tank. Take a sample of the hydrolyzed material for testing. The hydrolysis rate is 95.9%. The particle size of the hydrolyzed material is measured; D50: 1.86 μm. Filter the hydrolyzed material through a Buchner funnel using a vacuum pump. Once the hydrolyzed material forms a filter cake, add 1000 ml of deionized water to wash it and remove impurities. The washing time is 21 minutes. Press the filter cake dry after removing impurities, and add deionized water...

[0047] Titanium dioxide is produced by pulping, bleaching, adding salt treatment agent, calcining, and pulverizing. The color index of titanium dioxide is: L. * 98.73,b * :1.46, tinting strength: 112%.

[0048] Example 3

[0049] (1) Take 80m 3 Hydrolyzed titanium solution, 1.84m 3 Titanium liquid prepared by seed crystal preparation, 1.47m 3 NaOH solution. The specifications for the hydrolyzed titanium solution and the seed-prepared titanium solution are: TiO2: 200 g / L, F value: 2.6, trivalent titanium 2.3 g / L, Fe / TiO2: 0.30, stability (500 ml).

[0050] 80m 3 The hydrolyzed titanium solution was pumped into the preheating tank, and stirring was started. The temperature was raised after the pumping was complete. Simultaneously, 1.84 m³ of the solution was pumped in. 3 The titanium solution for seed crystal preparation was transferred to the titanium solution tank, and a 100 g / L NaOH solution was pumped in at a concentration of 1.47 m. 3 Pour the solution into the alkali tank and start stirring.

[0051] (2) When the temperature of the titanium hydrolysis solution in the preheating tank reaches 83°C, the titanium solution for seed crystal preparation and the NaOH solution are heated to 50°C respectively.

[0052] (3) Add the titanium solution for seed crystal preparation to the alkaline solution tank at 7 minutes and 12 seconds, heat it to a constant temperature of 95°C, and maintain this temperature. When the final stability of the hydrolyzed seed crystal is 90 ml, the preparation of the hydrolyzed seed crystal is completed.

[0053] (4) When the temperature of the hydrolyzed titanium solution in the preheating tank reaches 95°C, stop heating, add all the hydrolyzed seed crystals prepared in step 3, stir for 15 minutes, and then put the hydrolyzed titanium solution into the hydrolysis tank.

[0054] (5) Heat the titanium hydrolysate in the hydrolysis tank to boiling, and maintain it at 107°C until it turns white. Add 8mg of the solution. 3 Diluent was added, and the dilution time was 3 hours. Hydrolysis was then complete, and the hydrolyzed material was obtained. The total hydrolysis time was 5.5 hours.

[0055] (6) Place the hydrolyzed material into a cooling tank. Take a sample of the hydrolyzed material for testing. The hydrolysis rate is 95.5%. The particle size of the hydrolyzed material is tested; D50: 1.82 μm. Filter the hydrolyzed material through a Buchner funnel using a vacuum pump. Once the hydrolyzed material forms a filter cake, add 1000 ml of deionized water to wash it and remove impurities. The washing time is 21 minutes and 10 seconds. Press the filter cake dry, add deionized water, slurry, bleach, add a salt treatment agent, calcine, and pulverize to obtain titanium dioxide. The color index of titanium dioxide is: L. * 98.70,b * :1.48, tinting strength: 112%.

[0056] Comparative Example 1

[0057] (1) Take 80m 3 Hydrolyzed titanium solution, 1.68m 3 Titanium liquid prepared by seed crystal, 0.525m 3 NaOH solution. The parameters for the hydrolyzed titanium solution and the seed-prepared titanium solution are: TiO2: 200 g / L, F value: 2.2, trivalent titanium 2.3 g / L, Fe / TiO2: 0.30, stability (500 ml).

[0058] 80m 3 The hydrolyzed titanium solution was pumped into the preheating tank, and stirring was started. The temperature was raised after the pumping was complete. Simultaneously, 1.68m³ of the solution was pumped in. 3 The titanium solution for seed crystal preparation is transferred to the titanium solution tank, and 0.525 ml of a 100 g / L NaOH solution is pumped in. 3 Pour the solution into the alkali tank and start stirring.

[0059] (2) When the temperature of the titanium hydrolysis solution in the preheating tank reaches 80°C, the titanium solution for seed crystal preparation and the NaOH solution are heated to 85°C respectively.

[0060] (3) Add the titanium solution for seed crystal preparation to the alkaline solution tank at 3 minutes and 40 seconds, heat it to a constant temperature of 95°C, and maintain this temperature. When the final stability of the hydrolyzed seed crystal is 110 ml, the preparation of the hydrolyzed seed crystal is completed.

[0061] (4) When the temperature of the hydrolyzed titanium liquid in the preheating tank reaches 95°C, stop heating, add all the hydrolyzed seed crystals prepared in step 3, stir for 15 minutes, and then pump the hydrolyzed titanium liquid into the hydrolysis tank.

[0062] (5) Heat the titanium hydrolysate in the hydrolysis tank to a single boil, maintaining a gentle boil; when the titanium hydrolysate turns bluish-gray, stop heating for 30 minutes, then continue heating to a boil, maintaining a gentle boil for 3 hours to complete the hydrolysis. Add 8m 3 The diluted water was used to prepare the hydrolysate. The total hydrolysis time was 6 hours.

[0063] (6) Place the hydrolyzed material in a cooling tank and collect it after cooling. The hydrolysis rate is 93.8%, and the particle size (D50) is 1.28 μm. Filter the hydrolyzed material through a Buchner funnel using a vacuum pump until a filter cake is formed. Add 1000 ml of deionized water to wash away impurities for 35 minutes and 52 seconds. Dry the filter cake, add deionized water, slurry, bleach, add salt treatment agent, calcine, and pulverize to obtain titanium dioxide. The color index of titanium dioxide is: L. * 98.35,b * :1.68, tinting strength: 105%.

[0064] Comparative Example 2

[0065] (1) Take 80m 3 Hydrolyzed titanium solution, 1.68m 3 Titanium liquid prepared by seed crystal, 0.525m 3 KOH solution. The parameters for the hydrolyzed titanium solution and the seed-prepared titanium solution are: TiO2: 200 g / L, F value: 2.4, trivalent titanium 2.3 g / L, Fe / TiO2: 0.30, stability (500 ml).

[0066] 80m 3 The hydrolyzed titanium solution was pumped into the preheating tank, and stirring was started. The temperature was raised after the pumping was complete. Simultaneously, 1.68m³ of the solution was pumped in. 3 The titanium solution for seed crystal preparation is transferred to the titanium solution tank, and 0.525 ml of a 100 g / L KOH solution is pumped in. 3 Pour the solution into the alkali tank and start stirring.

[0067] (2) When the temperature of the titanium hydrolysis solution in the preheating tank reaches 80°C, the titanium solution for seed crystal preparation and the KOH solution are heated to 85°C respectively.

[0068] (3) Add the titanium solution for seed crystal preparation to the alkaline solution tank at 3 minutes and 40 seconds, heat it to a constant temperature of 95°C, and maintain this temperature. When the final stability of the hydrolyzed seed crystal is 110 ml, the preparation of the hydrolyzed seed crystal is completed.

[0069] (4) When the temperature of the hydrolyzed titanium liquid in the preheating tank reaches 95°C, stop heating, add all the hydrolyzed seed crystals prepared in step 3, stir for 15 minutes, and then pump the hydrolyzed titanium liquid into the hydrolysis tank.

[0070] (5) Heat the titanium hydrolysate in the hydrolysis tank to a single boil, maintaining a gentle boil; when the titanium hydrolysate turns bluish-gray, stop heating for 30 minutes, then continue heating to a boil, maintaining a gentle boil for 3 hours to complete the hydrolysis. Add 8m 3 The diluted water was used to prepare the hydrolysate. The total hydrolysis time was 6 hours.

[0071] (6) Place the hydrolysate in a cooling tank and collect it after cooling. The hydrolysis rate is 92.1%, and the particle size (D50) is 1.15 μm. Filter the hydrolysate through a Buchner funnel using a vacuum pump until a filter cake is formed. Add 1000 ml of deionized water to wash away impurities for 42 minutes and 10 seconds. Dry the filter cake, add deionized water, slurry, bleach, add salt treatment agent, calcine, and pulverize to obtain titanium dioxide. The color index of titanium dioxide is: L. * :98.21,b * :1.75, tinting strength: 105%.

[0072] Comparative Example 3

[0073] (1) Take 80m 3 Hydrolyzed titanium solution, 1.68m 3 Titanium liquid prepared by seed crystal, 0.525m 3 NaOH solution. The specifications for the hydrolyzed titanium solution and the seed-prepared titanium solution are: TiO2: 200 g / L, F value: 2.6, trivalent titanium 2.3 g / L, Fe / TiO2: 0.30, stability (500 ml).

[0074] 80m 3 The hydrolyzed titanium solution was pumped into the preheating tank, and stirring was started. The temperature was raised after the pumping was complete. Simultaneously, 1.68m³ of the solution was pumped in. 3 The titanium solution for seed crystal preparation is transferred to the titanium solution tank, and 0.525 ml of a 100 g / L NaOH solution is pumped in. 3 Pour the solution into the alkali tank and start stirring.

[0075] (2) When the temperature of the titanium hydrolysis solution in the preheating tank reaches 80°C, the titanium solution for seed crystal preparation and the NaOH solution are heated to 85°C respectively.

[0076] (3) Add the titanium solution for seed crystal preparation to the alkaline solution tank at 3 minutes and 40 seconds, heat it to a constant temperature of 95°C, and maintain this temperature. When the final stability of the hydrolyzed seed crystal is 110 ml, the preparation of the hydrolyzed seed crystal is completed.

[0077] (4) When the temperature of the hydrolyzed titanium liquid in the preheating tank reaches 95°C, stop heating, add all the hydrolyzed seed crystals prepared in step 3, stir for 15 minutes, and then pump the hydrolyzed titanium liquid into the hydrolysis tank.

[0078] (5) Heat the titanium hydrolysate in the hydrolysis tank to a single boil, maintaining a gentle boil; when the titanium hydrolysate turns bluish-gray, stop heating for 30 minutes, then continue heating to a boil, maintaining a gentle boil for 3 hours to complete the hydrolysis. Add 8m 3 The diluted water was used to prepare the hydrolysate. The total hydrolysis time was 6 hours.

[0079] (6) Place the hydrolyzed material in a cooling tank and collect it after cooling. The hydrolysis rate is 91.5%, and the particle size (D50) is 0.98 μm. Filter the hydrolyzed material through a Buchner funnel using a vacuum pump until a filter cake is formed. Add 1000 ml of deionized water to wash away impurities for 50 minutes and 6 seconds. Dry the filter cake, add deionized water, slurry, bleach, add salt treatment agent, calcine, and pulverize to obtain titanium dioxide. The color index of titanium dioxide is: L. * :98.19,b * :1.69, tinting strength: 105%.

[0080]

[0081] 1. Hydrolysis rate test:

[0082] Detection of unhydrolyzed residual titanium in hydrolyzed material: Take 100ml of hydrolyzed material, filter it, and use a pipette to draw 1ml of filtrate into a 500ml Erlenmeyer flask. Add 60ml of a mixed acid of sulfuric acid and hydrochloric acid, and 1.5g of aluminum sheet. Stopper the flask with a liquid seal. Add saturated sodium bicarbonate solution to the solution and heat until the aluminum sheet dissolves. After complete dissolution, continue heating until large bubbles appear. Remove the Erlenmeyer flask and cool it with running water. Be careful to add saturated sodium bicarbonate solution to the liquid seal tube as needed. After cooling to room temperature, titrate with ferric ammonium sulfate until colorless. Add 1 drop of ammonium cyanide sulfate indicator and continue titrating until the solution turns orange as the endpoint.

[0083]

[0084] In the formula:

[0085] ρTiO₂ — mass concentration of titanium dioxide, g / L;

[0086] c[NH4Fe(SO4)2] ——— Molar concentration of ferric ammonium sulfate solution, mol / L;

[0087] V — Volume of ferric ammonium sulfate solution consumed, in ml;

[0088] V1 — Volume of the volumetric flask, ml;

[0089] V2 — The volume of the diluted test solution, in ml;

[0090] V3 — The volume of the original concentrated solution, in ml;

[0091] 0.0799 — Molar mass of titanium dioxide, kg / mol.

[0092] 2. Calculation of hydrolysis rate:

[0093] Hydrolysis rate

[0094] a———— represents the total titanium concentration in the titanium solution (g / L);

[0095] ρ ——— represents the residual titanium content (g / l) of hydrolyzed metatitanic acid.

[0096] 3. Particle size detection of hydrolyzed material:

[0097] (1) Particle size analyzer (including matching computer): Model Malvern 2000

[0098] (2) Ultrasonic Cleaning Machine: GA-3200DTD, Wuxi Shangjia Biotechnology Co., Ltd.

[0099] (3) Sodium hexametaphosphate dispersant (0.05%)

[0100] (4) 250ml beaker

[0101] Analysis steps:

[0102] (1) Sample preparation: Add 200ml of distilled water to a beaker, dip a small amount of sample into the 200ml beaker with a glass rod, add dispersant (5 drops for powder, 8-10 drops for slurry, sand-milled, etc.), and place in an ultrasonic cleaner to disperse for 3 minutes, ready for testing.

[0103] (2) Open the machine program, then open the corresponding measurement program (finished product, crude product and intermediate control, etc.), then click "Manual" in "Measurement", and enter the batch number, name and sample source in "Document".

[0104] (3) Add 800ml of tap water to the instrument beaker to clean the machine, turn on the "PUMP" light on the disperser, set the speed to 2500 Rad / min, clean twice, and then add 800ml of distilled water to the beaker for later use.

[0105] (4) Click the "Start" button in "Manual" and turn on the ultrasonic (20um) on the disperser. Wait for the computer to prompt you to add the sample to be tested. Then add the sample that has been dispersed in the ultrasonic cleaner to the beaker of the particle size analyzer. The concentration should be between 8 and 12 as indicated.

[0106] (5) After adding the sample, click the "Start" button again to measure the sample. After 1 minute, turn off the ultrasonic machine and measure the sample again until the result is stable (generally, 2 measurements are required).

[0107] (6) Result: D50 indicates.

[0108] 4. Washing the hydrolyzed material: Measure 500ml of the hydrolyzed material and filter it through a vacuum pump using a Buchner funnel. Once the hydrolyzed material forms a filter cake, add 1000ml of deionized water for washing and record the washing time.

[0109] 5. Hydrolyzed material treatment: The filter cake is pressed dry, sampled into a beaker, deionized water is added, and the mixture is pulped. After treatment with bleaching salt, it is calcined to obtain titanium dioxide, which is then crushed and the color index of the titanium dioxide is tested.

[0110] 6. F-value

[0111] The ratio of effective acid to total titanium content in a titanium bath is called the acid ratio. The acid ratio is also called the acidity coefficient, commonly represented by F. In the titanium bath obtained from the leaching of acidolysis products, the acid exists mainly in three different forms:

[0112] (1) Sulfuric acid combined with titanium;

[0113] (2) Sulfuric acid combined with other metals (mainly iron);

[0114] (3) Unbound, excess free acid.

[0115] Since it is impossible to measure the acid bound to titanium and the free acid separately, only their sum can be measured. Therefore, the sum of the two is called the effective acid. Effective acid = Acid bound to titanium + Free acid.

Claims

1. A method for hydrolyzing high-F-value titanium liquid, characterized in that, Includes the following steps: S1. Prepare a heated hydrolyzed titanium solution; also prepare a seed-prepared titanium solution and an alkaline solution; wherein the F-value of both the hydrolyzed titanium solution and the seed-prepared titanium solution is 2.2-2.8; and the weight ratio of the seed-prepared titanium solution to the alkaline solution, based on TiO2, is 2-5:

1. S2. When the hydrolyzed titanium solution is heated to 80-85°C, the seed titanium solution and the alkaline solution are heated to 50-60°C respectively. S3. Add alkaline solution to the titanium solution for seed crystal preparation within 5-8 minutes, heat to 92-95℃, and keep it at this temperature until the final stability of the hydrolyzed seed crystal is 90-100ml. The preparation of the hydrolyzed seed crystal is then complete. S4. Stop heating when the temperature of the hydrolyzed titanium solution reaches 92-95℃, add the hydrolyzed seed crystals prepared in S3, stir, and pump the hydrolyzed titanium solution into the hydrolysis tank; S5. Heat the hydrolyzed titanium solution in the hydrolysis tank to boiling, maintain a gentle boil, and wait for the hydrolyzed titanium solution to turn white. Then add dilution water until the hydrolysis is complete. The dilution water is added to S5 over a period of 3 hours.

2. The method for hydrolyzing high-F-value titanium liquid as described in claim 1, characterized in that, The volume ratio of the hydrolyzed titanium solution and the seed-prepared titanium solution in S1 is 100:2.3-2.

6.

3. The method for hydrolyzing a high-F-value titanium solution as described in claim 1, characterized in that, Based on TiO2, the concentrations of the hydrolyzed titanium solution and the seed-prepared titanium solution in S1 are both 195-205 g / L, and the alkaline solution in S1 is a sodium hydroxide solution or a potassium hydroxide solution with a concentration of 95-105 g / L.

4. The method for hydrolyzing a high-F-value titanium solution as described in claim 1, characterized in that, Based on TiO2, the weight ratio of the hydrolyzed seed crystals in S4 to the hydrolyzed titanium liquid is 2.3-2.6:

100.

5. The method for hydrolyzing a high-F-value titanium solution as described in claim 1, characterized in that, The volume ratio of dilution water to hydrolyzed titanium solution in S5 is 1:6-10.

6. The method for hydrolyzing a high-F-value titanium solution as described in claim 1, characterized in that, The temperature for maintaining a gentle boil in S5 is 105-107℃.

7. A hydrolyzed material prepared by the hydrolysis method of high-F-value titanium liquid according to any one of claims 1-6, characterized in that, The particle size D50 of the hydrolysate is 1.8-1.9 μm, and the hydrolysis rate of the hydrolysate is 95.5-97%.

8. A titanium dioxide prepared using the hydrolyzed material according to claim 7, characterized in that, The quality index of the titanium dioxide is: L * :98.70—98.80、b * 1.36-1.50, tinting strength: >110%.

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