A method for recycling titanium oxychloride solution by-produced in chlorination process of titanium dioxide

Abstract

The application discloses a recycling method of titanium oxychloride solution by-produced in chlorination method of titanium dioxide, and comprises the following steps: S1, mixing and reacting the titanium oxychloride solution after removing iron with ZnO to generate ZnCl2; S2, beating the metatitanic acid filter cake after two washing and adding alkali to neutralize and remove sulfur; S3, beating the metatitanic acid filter cake after removing sulfur, adding the reaction solution prepared in the step S1 and other salt treatment agents to carry out salt treatment, and then carrying out solid-liquid separation to obtain a filter cake; and S4, calcining the filter cake. The application combines the titanium oxychloride solution with the preparation of the titanium dioxide by sulfuric acid method for the first time, utilizes the reaction of hydrochloric acid and ZnO to prepare the reaction solution containing ZnCl2, replaces the ZnCl2 salt treatment agent in the prior art, is used for the salt treatment of the titanium dioxide by sulfuric acid method, and simultaneously, the pH after the salt treatment makes the titanium oxychloride contained in the reaction solution hydrolyze into titanium dioxide, so that the purpose of recycling titanium in the titanium oxychloride can be achieved.

Description

Technical Field

[0001] This invention belongs to the field of titanium dioxide production technology, and specifically relates to a method for recycling titanium dioxide dichloride solution, a byproduct of the chloride process. Background Technology

[0002] The chlorination process is one of the main methods for producing titanium dioxide. It has gained increasing attention due to its advanced technology, large capacity, simple process, low energy consumption, and superior product performance. During the chlorination process, the tail gas contains a certain amount of titanium tetrachloride. After being absorbed by hydrochloric acid spraying, it forms an acidic titanium oxychloride solution. This solution mainly consists of 25-35% hydrochloric acid and a titanium oxychloride concentration (based on TiO2 content) of 50-120 g / L. It also contains high levels of impurities such as Fe, V, and Si.

[0003] Most methods for treating titanium oxychloride involve neutralization followed by discharge. However, this method increases the cost of wastewater treatment and wastes both acid and titanium resources.

[0004] Some researchers have proposed using it in the coating process of titanium dioxide, but the high Fe and V content in this part of titanium oxychloride will affect the hue of the finished titanium dioxide product, thus affecting the product quality.

[0005] Patent CN109019680A, entitled "A Method for Producing Titanium Dioxide from Hydrochloric Acid Byproduct of Chlorination Process Titanium Dioxide," provides a method for recovering and utilizing hydrochloric acid, a byproduct of the chloride process titanium dioxide production. This method involves reacting the hydrochloric acid (containing TiOCl2) with titanium concentrate via acid hydrolysis. After separating and removing acid-insoluble substances such as silica, the acid-hydrolyzed titanium solution is hydrolyzed to obtain crude titanium dioxide. The crude titanium dioxide is then washed and post-treated to obtain the finished titanium dioxide product. This method is similar to the hydrochloric acid hydrolysis method; on the one hand, the process is long and complex; on the other hand, it requires sophisticated equipment, making it difficult to achieve industrial-scale production.

[0006] Patent CN110589884, "A Method for Recycling Waste Titanium Oxide Dichloride," provides a method for recycling waste titanium oxychloride dichloride. This method involves replacing sulfuric acid with an acidic environment during the metatitanic acid bleaching process, while simultaneously adding a certain amount of aluminum powder. The drawback of this method is that it cannot be determined whether the added aluminum powder has reacted completely. Since aluminum salts are inhibitors of rutile conversion, if the added aluminum powder does not react completely, it remains in the metatitanic acid, which increases the calcination temperature and worsens the particle size and particle size distribution of the product. This results in poor gloss and a tendency for the TiO2 coating to be washed away.

[0007] Special treatment methods can reduce the iron content in titanium oxychloride solution to below 1 ppm. While this solution does not affect the color of the product during the coating process, the high concentration of hydrochloric acid in titanium oxychloride increases the amount of alkali consumed during pH neutralization during coating, thus increasing the coating cost.

[0008] On the other hand, the main process flow for producing titanium dioxide using the sulfuric acid process is: acid hydrolysis → hydrolysis, first washing → bleaching, second washing → salt treatment → calcination → post-treatment. ZnCl2 is a commonly used zinc salt treatment agent in the salt treatment process; it is prepared by reacting ZnO with hydrochloric acid. The reaction formula is: ZnO + 2HCl = ZnCl2 + H2O. Summary of the Invention

[0009] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for recycling titanium oxychloride solution, a byproduct of the chloride process for titanium dioxide production. This method applies the titanium oxychloride solution to the preparation process of the sulfuric acid process for titanium dioxide, thereby achieving high-value utilization of the titanium oxychloride solution.

[0010] The objective of this invention is achieved through the following technical solution:

[0011] A method for recycling titanium oxychloride solution, a byproduct of the titanium dioxide production process via the chloride process, includes the following steps:

[0012] S1. Take the iron-removed titanium oxychloride solution and react it with ZnO to generate ZnCl2;

[0013] S2. Take the qualified metatitanic acid filter cake after two washes and slurry it. Control the TiO2 content in the slurry to be 210-250 g / L, raise the temperature to 85-90℃, add alkali to neutralize and remove sulfur, control the final pH to be 8-8.5, and perform solid-liquid separation after the reaction is completed.

[0014] S3. The desulfurized metatitanic acid filter cake is slurried, and the TiO2 content in the slurry is controlled to be 210-250 g / L. The reaction solution obtained in step S1 and other salt treatment agents are added for salt treatment, and then the solid and liquid are separated to obtain the filter cake. The amount of the reaction solution added is to maintain the ZnO mass percentage in the calcined titanium dioxide base material at 0.25-0.29%.

[0015] S4. The filter cake obtained in step S3 is calcined to obtain titanium dioxide base material, and the rutile conversion rate of the titanium dioxide base material is controlled to be 98.7-99.2%.

[0016] Preferably, the titanium oxychloride solution after iron removal in step S1 contains 25-35% hydrochloric acid by mass and 50-120 g / L titanium oxychloride concentration based on TiO2 content.

[0017] Preferably, the titanium oxychloride solution after iron removal in step S1 contains 28-32% hydrochloric acid by mass and 100-120 g / L titanium oxychloride concentration based on TiO2 content.

[0018] Preferably, in step S1, the ZnO is first dissolved in a small amount of water, and then mixed with the titanium dichloride solution for a reaction time of 40 to 90 minutes. The concentration of ZnCl2 in the prepared reaction solution, calculated as ZnO, is 180 to 200 g / L.

[0019] Preferably, the amount of ZnO added is less than the theoretical amount required to completely react the hydrochloric acid in the dichloride solution, and the pH of the solution after the reaction is controlled to be 0.8-2.

[0020] Preferably, the reaction time in step S2 is 1.5 to 2.5 hours.

[0021] Preferably, the other salt treatment agents in step S3 are potassium hydroxide and phosphoric acid.

[0022] Preferably, the amount of potassium hydroxide added is such that the K2O content in the calcined base material is 0.17-0.19%, and the amount of phosphoric acid added is such that the P2O5 content in the calcined base material is 0.20-0.22%.

[0023] Preferably, the highest calcination temperature in step S3 is 915–925°C, and the total calcination time is [not specified].

[0024] Preferably, the alkali in step S2 is selected from one or more combinations of ammonia, sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, potassium carbonate, and potassium bicarbonate.

[0025] This invention is the first to combine titanium oxychloride solution with the preparation of titanium dioxide using the sulfuric acid process. The hydrochloric acid in the solution reacts with ZnO to prepare a reaction solution containing ZnCl2, which replaces the ZnCl2 salt treatment agent in the prior art for the treatment of titanium dioxide using the sulfuric acid process. At the same time, the pH after salt treatment causes the titanium oxychloride in the reaction solution to hydrolyze into titanium dioxide, thereby achieving the purpose of recovering titanium from titanium oxychloride.

[0026] Moreover, the method of the present invention is simple to operate, has a short process flow, and is easy to industrialize, thus realizing the effective recovery and utilization of hydrochloric acid and titanium resources in titanium oxychloride solution. Detailed Implementation

[0027] The method for recycling titanium oxychloride solution, a byproduct of the titanium dioxide production process via the chloride process, provided by this invention, includes the following steps:

[0028] S1. Take the iron-removed titanium oxychloride solution (iron content less than 1 ppm) and react it with ZnO to generate ZnCl2;

[0029] S2. Take the qualified metatitanic acid filter cake after two washes and slurry it. Control the TiO2 content in the slurry to be 210-250 g / L. Heat it to 85-90℃, add alkali for neutralization and desulfurization, control the final pH to be 8-8.5, and perform solid-liquid separation after the reaction is completed.

[0030] S3. The desulfurized metatitanic acid filter cake is slurried, and the TiO2 content in the slurry is controlled to be 210-250 g / L. The reaction solution obtained in step S1 and other salt treatment agents are added for salt treatment, and then the solid and liquid are separated to obtain the filter cake. The amount of reaction solution added is to maintain the ZnO mass percentage in the calcined titanium dioxide base material at 0.25-0.29%.

[0031] In step S2, during the desulfurization process, the sulfate ions adsorbed on the surface of metatitanic acid and the sulfate ions bound to metatitanic acid will depolymerize with the metatitanic acid, causing the viscosity of the material to increase. Therefore, in order to make the alkali neutralization reaction more complete, the concentration of the metatitanic acid slurry after the second washing should not be too high, preferably 210-250 g / L. Compared with the metatitanic acid slurry before conventional salt treatment, the viscosity of the material after desulfurization increases. Therefore, in order to make the reaction with the salt treatment agent more complete, the concentration of the metatitanic acid slurry after desulfurization should not be too high, preferably 210-250 g / L.

[0032] S4. Calcine the filter cake obtained in step S2 to obtain titanium dioxide base material; control the rutile conversion rate of titanium dioxide base material to be 98.7-99.2%.

[0033] Titanium oxychloride solution not only contains a large amount of hydrochloric acid, but also produces TiO2 after hydrolysis. In order to realize the high-value utilization of titanium oxychloride solution, this invention combines it with the preparation of titanium dioxide by the sulfuric acid method for the first time, so as to effectively recover and utilize both hydrochloric acid and titanium resources in titanium oxychloride solution.

[0034] Specifically, conventional salt treatment agent ZnCl2 is prepared by reacting ZnO and hydrochloric acid. However, this invention first reacts titanium oxychloride solution with ZnO, and then uses the hydrochloric acid in the solution to react with ZnO to generate ZnCl2. This reaction solution replaces ZnCl2 in the prior art as a salt treatment agent, realizing the recovery and utilization of hydrochloric acid in titanium oxychloride solution.

[0035] In addition, the pH of the metatitanic acid slurry after conventional second washing before salt treatment is 1-2. Under this pH range, titanium oxychloride will not hydrolyze. After neutralization with alkali, the sulfur in the metatitanic acid slurry can be further removed (the surface of metatitanic acid contains a large number of sulfate ions, which are acidic. Alkaline reagents can react with the sulfate ions in metatitanic acid to generate water-soluble compounds such as ammonium sulfate, sodium sulfate, and potassium sulfate. Most of the sulfate ions in metatitanic acid can be removed by subsequent solid-liquid separation steps such as pressure filtration and water washing). The pH of the metatitanic acid slurry after second washing is adjusted to 8-8.5, which can meet the conditions for the hydrolysis of titanium oxychloride. Therefore, this application first desulfurizes the second-washed metatitanic acid and then performs salt treatment.

[0036] After desulfurization, the pH of the secondary washing metatitanic acid slurry is between 8 and 8.5. With the addition of ZnCl2, a salt treatment agent prepared from titanium oxychloride solution, and other salt treatment agents (preferably KOH and phosphoric acid in this application), the pH of the secondary washing metatitanic acid slurry decreases from the original 8-8.5 to 7.5-8. Since titanium oxychloride will hydrolyze at pH > 2, after adding ZnCl2, a salt treatment agent prepared from titanium oxychloride solution, titanium oxychloride will hydrolyze to generate solid titanium dioxide. Analysis shows that the titanium dioxide content in the filtrate after salt treatment is less than 10 ppm, indicating that the titanium in titanium oxychloride has been fully recovered and utilized.

[0037] The reaction formulas for ZnO and hydrochloric acid are shown in Formula 1, and the reaction formulas for the hydrolysis of titanium oxychloride are shown in Formula 2.

[0038] ZnO + 2HCl → ZnCl2 + H2O (Equation 1)

[0039] TiOCl2 + nH2O → TiO2·(n+1)H2O + HCl (Equation 2)

[0040] Analysis of the crystal structure of TiO2 after hydrolysis of titanium oxychloride revealed that the TiO2 produced after hydrolysis is primarily anatase, with approximately 20% rutile. This rutile TiO2 acts as a seed crystal during the later calcination process. With the same amount of seed crystal added in the initial stage, adding a ZnCl2 salt treatment agent prepared from titanium oxychloride solution during the salt treatment process is equivalent to adding a small amount of additional seed crystals, which can lower the calcination temperature and shorten the calcination time. Furthermore, the predominantly anatase TiO2 crystal form after hydrolysis can transform into rutile TiO2 during the later calcination process, without affecting the final product quality.

[0041] Therefore, the method of this application can realize the recovery and utilization of hydrochloric acid and titanium dioxide in titanium oxychloride, reducing the cost of wastewater treatment; moreover, the present invention is simple to operate, has a short process flow, and is easy to realize industrial production.

[0042] To ensure stability during the production process, the hydrochloric acid and titanium oxychloride content in the selected titanium oxychloride solution must be within a certain range. Preferably, the hydrochloric acid mass percentage is 25-35%, and the titanium oxychloride concentration (based on TiO2 content) is 50-120 g / L. More preferably, the hydrochloric acid mass percentage in the titanium oxychloride solution is 28-32%, and the titanium oxychloride concentration (based on TiO2 content) is 100-120 g / L.

[0043] Preferably, in step S1, ZnO is first dissolved in a small amount of water, and then mixed with a titanium dichloride solution for reaction. Preparing ZnO as a solution before reacting with the titanium dichloride solution reduces the intensity of the reaction and minimizes dust generation. Furthermore, it ensures sufficient contact between ZnO and hydrochloric acid, facilitating the formation of zinc chloride. The preferred reaction time is 40–90 min. The ZnCl2 concentration in the prepared reaction solution, calculated as ZnO, is preferably 180–200 g / L. Within this concentration range, it facilitates thorough mixing with the secondary titanate slurry for salt treatment.

[0044] Preferably, to ensure complete reaction of zinc oxide, the amount of ZnO added is less than the theoretical amount required for complete reaction of hydrochloric acid in the titanium dioxide solution, and the pH of the solution after the reaction is controlled to be 0.8–2 (the original titanium dioxide solution has a high acidity and a negative pH). If ZnO is in excess, incomplete reaction of zinc oxide may occur, resulting in precipitation. This further makes it difficult to control the amount added during salt treatment, leading to large fluctuations in the zinc oxide content in the base material after calcination, which in turn affects the calcination process and product quality.

[0045] Preferably, the reaction time in step S2 is 1.5 to 2.5 hours.

[0046] Preferably, in step S2, to reduce the amount of ammonia nitrogen-containing wastewater, the filter cake after solid-liquid separation does not need to be washed with water.

[0047] Step S3, the salt treatment, except that a ZnCl2 reaction solution is used instead of the conventional ZnCl2 treatment agent, can be performed using conventional methods. Other salt treatment agents can be conventional salt treatment agents, preferably potassium hydroxide and phosphoric acid.

[0048] More preferably, the amount of potassium hydroxide added is such that the K2O content in the calcined base material is 0.17-0.19%, and the amount of phosphoric acid added is such that the P2O5 content in the calcined base material is 0.20-0.22%.

[0049] After adding the salt treatment agent, the mixture is stirred evenly and then filtered to obtain a filter cake with a solid content of ≥57%.

[0050] Example 1

[0051] (1) Take titanium oxychloride after iron removal in the workshop, in which the mass fraction of hydrochloric acid is 32% and the concentration of titanium oxychloride (based on TiO2 content) is 115 g / L;

[0052] (2) Add 135 mL of softened water to a 500 mL three-necked flask, add 57 g of ZnO powder while stirring, then add 148 mL of titanium oxychloride solution. After reacting for 60 min, set aside for later use. The ZnCl2 concentration (calculated as ZnO) was 191.92 g / L, and the titanium oxychloride concentration (calculated as TiO2) was 57.31 g / L.

[0053] (3) Take the qualified metatitanic acid filter cake after two washes and slurry it. Keep the TiO2 content in the slurry at 230g / L, raise the temperature to 85℃, add ammonia water for neutralization, and keep the pH at the endpoint at 8.5. After the reaction is completed, perform solid-liquid separation.

[0054] (4) Take the desulfurized metatitanic acid filter cake, slurry it with deionized water, keep the TiO2 content in the slurry at 210 g / L and the slurry volume at 500 mL, add 0.55% potassium hydroxide, 0.2% phosphoric acid and 0.85% of the prepared ZnCl2 solution according to the mass of TiO2 in the metatitanic acid slurry respectively, stir evenly, filter and obtain filter cake, ensure that the K2O content in the base material after calcination is 0.17%, the P2O5 content is 0.21% and the ZnO content is 0.29%; analyze the titanium dioxide content in the filtrate after salt treatment is 5 ppm.

[0055] (5) Calcine the filter cake. The specific operation is as follows: First, raise the temperature to 350℃ within 30 minutes, then raise the temperature to 650℃ within 30 minutes, then raise the temperature to 780℃ within 20 minutes and keep it at that temperature for 1 hour. Finally, raise the temperature to 830℃ within 30 minutes. Take a sample every 20 minutes to test its rutile conversion rate. If the conversion rate is lower than 98.7%, raise the temperature by 10℃ and continue to keep it at that temperature. Repeat the above operation until the conversion rate is between 98.7% and 99.2% (when the conversion rate is close to the target value, the detection frequency can be increased and the temperature can be kept constant or increased slightly for the time being). Record the calcination temperature and time.

[0056] Example 2

[0057] (1) Take titanium oxychloride after iron removal in the workshop, in which the mass fraction of hydrochloric acid is 28% and the concentration of titanium oxychloride (based on TiO2 content) is 110 g / L;

[0058] (2) Add 120 mL of softened water to a 500 mL three-necked flask, add 61.8 g of ZnO powder while stirring, then add 180 mL of titanium oxychloride solution. After reacting for 60 min, set aside for later use. The ZnCl2 concentration (calculated as ZnO) was 196.19 g / L, and the titanium oxychloride concentration (calculated as TiO2) was 62.86 g / L.

[0059] (3) Take the qualified metatitanic acid filter cake after two washes and slurry it. Keep the TiO2 content in the slurry at 245g / L, raise the temperature to 90℃, add ammonia water for neutralization, and keep the pH at the endpoint at 8.0 for 2 hours. After the reaction is completed, perform solid-liquid separation.

[0060] (4) Take the desulfurized metatitanic acid filter cake, slurry it with deionized water, keep the TiO2 content in the slurry at 240 g / L and the slurry volume at 500 mL, add 0.48% potassium hydroxide, 0.2% phosphoric acid and 0.76% of the prepared ZnCl2 solution according to the mass of TiO2 in the metatitanic acid slurry respectively, stir evenly, filter and obtain filter cake, ensure that the K2O content in the base material after calcination is 0.19%, the P2O5 content is 0.20% and the ZnO content is 0.27%; analyze the titanium dioxide content in the filtrate after salt treatment is 7 ppm.

[0061] (5) Calcine the filter cake and record the calcination temperature and time. The specific operation is the same as in Example 1.

[0062] Example 3

[0063] (1) Take titanium oxychloride after iron removal in the workshop, in which the mass fraction of hydrochloric acid is 30% and the concentration of titanium oxychloride (based on TiO2 content) is 120 g / L;

[0064] (2) Add 140 mL of softened water to a 500 mL three-necked flask, add 59.4 g of ZnO powder while stirring, then add 165 mL of titanium oxychloride solution. After reacting for 60 min, set aside for later use. The ZnCl2 concentration (calculated as ZnO) was 185.63 g / L, and the titanium oxychloride concentration (calculated as TiO2) was 61.88 g / L.

[0065] (3) Take the qualified metatitanic acid filter cake after two washes and slurry it. Keep the TiO2 content in the slurry at 210g / L, raise the temperature to 85℃, add ammonia water for neutralization, and keep the pH at the endpoint at 8.3. After 2 hours, perform solid-liquid separation.

[0066] (4) Take the desulfurized metatitanic acid filter cake, slurry it with deionized water, keep the TiO2 content in the slurry at 220 g / L and the slurry volume at 500 mL, add 0.53% potassium hydroxide, 0.2% phosphoric acid and 0.73% of the prepared ZnCl2 solution according to the mass of TiO2 in the metatitanic acid slurry respectively, stir evenly, filter and obtain filter cake, ensure that the K2O content in the base material after calcination is 0.18%, the P2O5 content is 0.22% and the ZnO content is 0.25%; analyze the titanium dioxide content in the filtrate after salt treatment is 8 ppm.

[0067] (5) Calcine the filter cake and record the calcination temperature and time. The specific operation is the same as in Example 1.

[0068] Comparative Example 1

[0069] (1) Take the desulfurized metatitanic acid filter cake, slurry the filter cake with deionized water, keep the TiO2 content in the slurry at 210 g / L and the slurry volume at 500 mL, add 0.55% potassium hydroxide, 0.2% phosphoric acid and 0.85% conventional ZnCl2 solution (ZnCl2 concentration is 191.92 g / L) according to the mass of TiO2 in the slurry, stir evenly, filter, and obtain filter cake, ensuring that the K2O content in the base material after calcination is 0.17%, the P2O5 content is 0.21% and the ZnO content is 0.29%;

[0070] (2) Calcine the filter cake and record the calcination temperature and time. The specific operation is the same as in Example 1.

[0071] Comparative Example 2

[0072] (1) Take the desulfurized metatitanic acid filter cake, slurry it with deionized water, keep the TiO2 content in the slurry at 220 g / L and the slurry volume at 500 mL, add 0.53% potassium hydroxide, 0.2% phosphoric acid and 0.73% ZnCl2 solution (ZnCl2 concentration is 185.63 g / L) according to the mass of TiO2 in the slurry, stir evenly, filter and obtain filter cake, ensure that the K2O content in the base material after calcination is 0.18%, the P2O5 content is 0.22% and the ZnO content is 0.25%;

[0073] (2) Calcine the filter cake and record the calcination temperature and time. The specific operation is the same as in Example 1.

[0074] The ZnCl2 solution prepared in this invention was used in salt treatment. The results of calcination temperature and calcination time are compared with those of the comparative example, as shown in Table 1.

[0075] Table 1

[0076]

[0077] The data comparison above shows that using titanium oxychloride solution to prepare ZnCl2 salt treatment agent, and then using it in the sulfuric acid process for titanium dioxide treatment, utilizes the hydrochloric acid in titanium oxychloride while the rutile phase TiO2 formed by the hydrolysis of titanium oxychloride can act as a seed crystal for calcination. Under the premise of consistent base material conversion rate, the calcination temperature is reduced and / or the calcination time is shortened, thereby achieving the goal of reducing calcination energy consumption. The method of this invention is simple, low-cost, and has good prospects for industrialization.

[0078] The titanium dioxide content in the final discharged titanium oxychloride waste liquid (i.e., the salt-treated filtration solution) is less than 10 ppm, indicating that the titanium in the titanium oxychloride has been fully recovered and utilized.

[0079] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if these modifications and modifications of the invention fall within the scope of the claims and their equivalents, the invention is also intended to include these modifications and modifications.

Claims

1. A method for recovering and utilizing titanium oxychloride solution, a byproduct of the titanium dioxide production process via the chloride process, characterized in that... Includes the following steps: S1. Take the iron-removed titanium oxychloride solution and react it with ZnO to generate ZnCl2; the iron-removed titanium oxychloride solution contains 25-35% hydrochloric acid by mass and the titanium oxychloride concentration is 50-120 g / L based on TiO2 content; the amount of ZnO added is less than the theoretical amount required to completely react the hydrochloric acid in the titanium oxychloride solution, and the pH of the solution after the reaction is controlled to be 0.8-2; S2. Take the qualified metatitanic acid filter cake after two washes and slurry it. Control the TiO2 content in the slurry to be 210-250 g / L, raise the temperature to 85-90℃, add alkali to neutralize and remove sulfur, control the final pH to be 8-8.5, and perform solid-liquid separation after the reaction is completed. S3. The desulfurized metatitanic acid filter cake is slurried, and the TiO2 content in the slurry is controlled to be 210-250 g / L. The reaction solution obtained in step S1 and other salt treatment agents are added for salt treatment, and the titanium oxychloride in the titanium oxychloride solution will be hydrolyzed to generate solid titanium dioxide. Then, the solid and liquid are separated to obtain the filter cake. The amount of the reaction solution added is to maintain the ZnO mass percentage in the calcined titanium dioxide base material at 0.25-0.29%. S4. The filter cake obtained in step S3 is calcined to obtain titanium dioxide base material, and the rutile conversion rate of the titanium dioxide base material is controlled to be 98.7-99.2%.

2. The method for recycling titanium oxychloride solution, a byproduct of the titanium dioxide production process via the chloride process, as described in claim 1, is characterized in that... The titanium oxychloride solution after iron removal in step S1 contains 28-32% hydrochloric acid by mass and 100-120 g / L titanium oxychloride concentration based on TiO2 content.

3. The method for recycling titanium oxychloride solution, a byproduct of the titanium dioxide production process via the chloride process, as described in claim 1, is characterized in that... In step S1, ZnO is first dissolved in a small amount of water, and then mixed with the titanium oxychloride solution for a reaction time of 40-90 min. The concentration of ZnCl2 in the prepared reaction solution, calculated as ZnO, is 180-200 g / L.

4. The method for recycling titanium oxychloride solution, a byproduct of the titanium dioxide production process via the chloride process, as described in claim 1, is characterized in that... The reaction time for step S2 is 1.5 to 2.5 hours.

5. The method for recycling titanium oxychloride solution, a byproduct of the titanium dioxide production process via the chloride process, as described in claim 1, is characterized in that... The other salt treatment agents mentioned in step S3 are potassium hydroxide and phosphoric acid.

6. The method for recycling titanium oxychloride solution, a byproduct of the titanium dioxide production process via the chloride process, as described in claim 5, is characterized in that... The amount of potassium hydroxide added is such that the K2O content in the calcined base material is 0.17-0.19%, and the amount of phosphoric acid added is such that the P2O5 content in the calcined base material is 0.20-0.22%.

7. The method for recycling titanium oxychloride solution, a byproduct of the titanium dioxide production process via the chloride process, as described in claim 1, is characterized in that... The maximum calcination temperature in step S3 is 915–925°C, and the total calcination time is 4.5–5.5 h.

8. The method for recycling titanium oxychloride solution, a byproduct of the titanium dioxide production process via the chloride process, as described in claim 1, is characterized in that... The alkali mentioned in step S2 is selected from one or more combinations of ammonia, sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, potassium carbonate, and potassium bicarbonate.

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