A method for recycling of pre-kiln pressing water in sulfuric acid method titanium dioxide production and a production process of sulfuric acid method titanium dioxide

Abstract

The present application relates to the chemical industry, in particular to a kind of sulphuric acid method titanium white before kiln squeezing water recycling method and sulphuric acid method titanium white production process.The present application collects and recycles before kiln squeezing water in sulphuric acid method titanium white process, specifically recycling to bleaching and two washing procedures respectively, by the above-mentioned recycling, the collected before kiln squeezing water can be recycled completely, save bleaching pulp water while the percolation metatitanic acid is recycled to the flow, because the pulp after bleaching is washed by two washing, the soluble salt carried in before kiln squeezing water can be washed, so it will not affect subsequent salt treatment and calcination.In addition, by the recycling method of the present application, 1.5-2.0 t of water can be saved per ton of titanium dioxide, according to this calculation, 150-200 thousand tons of water can be saved in a 100,000-ton-per-year titanium dioxide production line, greatly saving the cost.

Description

Technical Field

[0001] This invention relates to the chemical industry, and in particular to a method for recycling pressing water before the kiln in the sulfuric acid process for titanium dioxide production, as well as the production process of titanium dioxide using the sulfuric acid process. Background Technology

[0002] Titanium dioxide (TiO2) is mainly produced through two processes: the sulfuric acid process and the chloride process. The sulfuric acid process for titanium dioxide production is roughly as follows: ilmenite → sulfuric acid decomposition → reduction → sedimentation → crystallization → fine filtration → concentration → hydrolysis → washing → filtration → calcination → pulverization → surface treatment → three washings → flash drying → steam drying → finished product. The specific process is as follows:

[0003] (1) Acid hydrolysis (acid hydrolysis leaching and reduction): Iron-titanium ore is mixed with concentrated sulfuric acid. The strong acid decomposes the main component of titanium concentrate, ilmenite (FeTiO3), into soluble titanium salts. At the same time, various impurities in the ore powder are also dissolved to form corresponding soluble sulfates, which enter the solution along with the soluble titanium salts during leaching, forming black titanium solution. Then, metallic iron is added for reduction (specifically, to remove iron, metallic iron is added to reduce the high-valent iron in the titanium solution to ferrous iron. At the same time, to prevent the ferrous iron from oxidizing again, an excess of metallic iron must be used to reduce a certain amount of tetravalent titanium to trivalent titanium).

[0004] (2) Sedimentation: The system after acid leaching and reduction contains soluble and insoluble impurities. Most of the insoluble impurities (such as undecomposed titanium ore, sand particles, etc.) can settle naturally by gravity. The other part of the insoluble impurities (such as colloidal compounds of silicon and aluminum, etc.) need to be settled by adding a sedimentation agent.

[0005] (3) Crystallization: Crystallize the settled titanium liquid (usually by freeze crystallization) to form FeSO4·7H2O crystals, which are then separated and removed.

[0006] (4) Fine filtration and concentration: The titanium liquid obtained after the crystallization process still contains some suspended impurities that are invisible to the naked eye, which will affect the color of the finished product. These insoluble impurities are further removed by using a filter press with the aid of a filter aid, thereby purifying the titanium liquid. Then, taking advantage of the principle that the boiling point of a solution decreases under vacuum, the titanium liquid is boiled at a low temperature to evaporate the water and increase the concentration of the titanium liquid to about 200 g / L (i.e., concentration) to meet the requirements of hydrolysis.

[0007] (5) Hydrolysis: Hydrolysis of titanium liquid is the process of converting the titanium dioxide component in the titanium liquid from the liquid phase back into the solid phase, thereby separating it from the soluble impurities in the mother liquor and extracting pure titanium dioxide. Taking the seed crystal method as an example, the process generally includes: preheating, adding seed crystals to the titanium liquid, stirring the mixture and introducing saturated steam to raise the temperature of the titanium liquid to a slight boiling point to carry out the hydrolysis reaction, forming hydrated titanium dioxide (also known as "metatitanic acid") particles in the system, and obtaining a slurry containing hydrated titanium dioxide particles (i.e., hydrolyzed metatitanic acid slurry).

[0008] (6) Washing with water:

[0009] 6.1) First wash:

[0010] Hydrolyzed metatitanic acid slurry contains sulfuric acid and metal ions (such as iron, aluminum, manganese, copper, nickel, vanadium, lead, etc.). If these ions enter the rotary kiln along with hydrated titanium dioxide, they will generate corresponding oxides during calcination, displaying various colors and contaminating the product. Therefore, they must be separated and removed. Hydrated titanium dioxide is insoluble in water, while sulfuric acid and the aforementioned metal ions are soluble in water. Therefore, these substances can be removed by washing with water. Specifically, the hydrolyzed metatitanic acid slurry is vacuum filtered using a leaf filter. The filter cake is sent to a washing tank for washing with warm water. After passing the washing test, it is discharged into a discharge tank for pulping to obtain washed metatitanic acid.

[0011] 6.2) Bleaching:

[0012] The washed metatitanic acid is sent to a bleaching tank / bleaching vessel, where calcined seed crystals and bleaching agent are added for bleaching and pulping.

[0013] 6.3) Second wash:

[0014] The bleached metatitanic acid slurry is vacuum filtered using a leaf filter. The filter cake is sent to a secondary washing tank for rinsing with warm water (i.e., secondary washing). After passing the rinsing, it is unloaded into a discharge tank for pulping. The pulped metatitanic acid is then sent to a large metatitanic acid storage tank.

[0015] (7) Salt treatment: The metatitanic acid slurry after water washing is sent to the salt treatment tank, and salt treatment agents (including potassium salt and phosphoric acid) are added for salt treatment, thereby improving the pigment properties of the subsequent calcined products (such as making the calcined products soft, white, and tinting strength).

[0016] (8) Pre-kiln pressing: The metatitanic acid after salt treatment is sent to the pressing plate frame for dehydration, and the filter cake after pre-kiln pressing (metatitanic acid filter cake) and pre-kiln pressing water are obtained respectively.

[0017] (9) Calcination: The filter cake after pressing in front of the kiln is sent to the rotary kiln for calcination. Calcination is the process of dehydrating and desulfurizing hydrated titanium dioxide to transform it into anatase or rutile titanium dioxide. Specifically, at high temperature, free water, bound water, sulfur trioxide, etc. are removed from hydrated titanium dioxide, and then the crystal form is adjusted and transformed in the high-temperature zone to form titanium dioxide granules.

[0018] (10) Surface treatment: After calcination, the material is crushed, wet ball milled, and sand milled and then sent to the surface treatment process for surface treatment. After surface treatment, the material is washed three times and pressed by diaphragm to obtain the three-wash filter cake.

[0019] (11) Flash drying, steam powdering and packaging: After flash drying and steam powdering, the three-wash filter cake is sent to the finished product silo and packaged to become the finished product.

[0020] In the sulfuric acid process for titanium dioxide production, approximately 60 m³ of water is consumed to produce 1 ton of titanium dioxide, with the washing process consuming the largest amount of water. To reduce water consumption, some of the water used in the production process is often reused. After salt treatment, the metatitanic acid is pressed before the kiln, and the resulting filter cake is calcined in a rotary kiln. The resulting pre-kiln pressing water can be reused (approximately 1.5–2.0 tons of pressing water are generated per ton of titanium dioxide produced). This pre-kiln pressing water contains some metatitanic acid and salt treatment agent that has passed through the filter, but their content fluctuates. Therefore, directly reusing it in the salt treatment process can easily cause fluctuations in the salt treatment agent content, leading to corresponding fluctuations in the quality of the calcined titanium dioxide. Summary of the Invention

[0021] In view of this, the present invention provides a method for recycling pressing water before the kiln in the sulfuric acid process for titanium dioxide production, as well as a production process for the sulfuric acid process for titanium dioxide. The present invention can effectively save water, reduce water consumption, and will not have an adverse effect on the quality of titanium dioxide.

[0022] This invention provides a method for reusing press water before the sulfuric acid process titanium dioxide kiln, comprising the following steps:

[0023] S1. Collect the pre-kiln press water in the sulfuric acid titanium dioxide process into a press water storage tank.

[0024] S2. Connect the press water storage tank to the bleaching tank and the second washing water tank in the sulfuric acid titanium dioxide process, respectively.

[0025] S3. In the bleaching process of the washing section of the sulfuric acid process for titanium dioxide, the kiln-front press water is first sent to the bleaching tank and mixed with the first-wash metatitanic acid slurry from the first washing process. Then, calcined seed crystals and bleaching agent are added for bleaching to obtain bleached slurry.

[0026] S4. In the second washing process of the water washing section of the sulfuric acid titanium dioxide process, the pre-kiln press water is first sent to the second washing water tank to wash the bleached slurry from the bleaching process until the pre-kiln press water is used up, and then the second washing water is used to continue the second washing.

[0027] Preferably, in step S2, the press water storage tank is connected to the bleaching tank in the sulfuric acid titanium dioxide process using pipes and water pumps.

[0028] Preferably, in step S2, the press water storage tank is connected to the second washing water tank in the sulfuric acid titanium dioxide process using pipes and water pumps.

[0029] Preferably, in step S2, the press water storage tank is connected to the inlet pipe of the second washing water tank in the sulfuric acid titanium dioxide process using pipes and water pumps.

[0030] Preferably, in step S3, the solid content of the first-washed metatitanic acid slurry is 30% to 38%.

[0031] Preferably, in step S3, the concentration of the pulp obtained by pulping is 300-400 g / L.

[0032] Preferably, in step S3, the specific gravity of the pulp obtained by pulping is 1.25 to 1.34.

[0033] Preferably, the present invention adds 1.5 to 2.0 mg per ton of titanium dioxide. 3 A proportion of the pressed water is reused, of which 0.3–1.4 m³ is consumed in the bleaching process. 3 The remaining portion is used for the second washing process.

[0034] Preferably, the pre-kiln press water is obtained by pressing and dehydrating metatitanic acid after salt treatment in the sulfuric acid process for titanium dioxide production.

[0035] This invention also provides a process for producing titanium dioxide using the sulfuric acid process, comprising the following steps:

[0036] Titanium dioxide is produced using the sulfuric acid process, in which the pre-kiln pressing water is reused during the production process.

[0037] The reuse method described in the above technical solution is employed in this process.

[0038] This invention provides a method for reusing pre-kiln press water in the sulfuric acid process for titanium dioxide production. The method collects and reuses the pre-kiln press water in the sulfuric acid process, specifically in the bleaching and secondary washing stages. This reuse method allows for the complete recycling of the collected pre-kiln press water, saving water used in bleaching and pulping while also recycling the filtered metatitanic acid back into the process. Since the secondary washing of the bleached pulp removes soluble salts from the pre-kiln press water, it does not affect subsequent salt treatment and calcination. Furthermore, this method saves 1.5–2.0 tons of water per ton of titanium dioxide produced. Based on this calculation, a 100,000-ton-per-year titanium dioxide production line can save 150,000–200,000 tons of water, significantly reducing costs. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0040] Figure 1 This is a schematic diagram illustrating the reuse of pressing water before the sulfuric acid process titanium dioxide kiln according to the present invention. Detailed Implementation

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0042] In this article, the technical features described in an open-ended manner include both closed technical solutions composed of the listed features and open technical solutions that include the listed features.

[0043] The term “and / or” as used herein includes any and all combinations of one or more of the related listed items.

[0044] In this document, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when a range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0045] In this article, when referring to units for data ranges, if the unit is only followed by the right endpoint, it indicates that the units for the left and right endpoints are the same. For example, 300~400g / L means that the units for the left endpoint "300" and the right endpoint "400" are both g / L.

[0046] This invention provides a method for reusing press water before the sulfuric acid process titanium dioxide kiln, comprising the following steps:

[0047] S1. Collect the pre-kiln press water in the sulfuric acid titanium dioxide process into a press water storage tank.

[0048] S2. Connect the press water storage tank to the bleaching tank and the second washing water tank in the sulfuric acid titanium dioxide process, respectively.

[0049] S3. In the bleaching process of the washing section of the sulfuric acid process for titanium dioxide, the kiln-front press water is first sent to the bleaching tank and mixed with the first-wash metatitanic acid slurry from the first washing process. Then, calcined seed crystals and bleaching agent are added for bleaching to obtain bleached slurry.

[0050] S4. In the second washing process of the water washing section of the sulfuric acid titanium dioxide process, the pre-kiln press water is first sent to the second washing water tank to wash the bleached slurry from the bleaching process until the pre-kiln press water is used up, and then the second washing water is used to continue the second washing.

[0051] In this invention, steps that are sequentially related are performed in that order, while steps that are not sequentially related have no special restrictions on their order. "Steps that are not sequentially related" refers to steps that do not necessarily have a sequential relationship. For example, steps S1 and S2 are not sequentially related, therefore, their order is not particularly restricted.

[0052] See Figure 1 , Figure 1 This is a schematic diagram illustrating the reuse of pressing water before the sulfuric acid process titanium dioxide kiln according to the present invention.

[0053] According to this invention, the pre-kiln press water from the sulfuric acid process in titanium dioxide production is first collected in a press water storage tank. The sulfuric acid process for titanium dioxide production is not particularly limited and can be any conventional process in the field. The pre-kiln press water is obtained by pressing and dehydrating metatitanic acid after salt treatment in the sulfuric acid process. The pressing and dehydration process yields filter cake and press water. The obtained filter cake is sent to a rotary kiln for calcination, and the obtained press water is collected and reused according to this invention.

[0054] According to this invention, the press water storage tank is connected to the bleaching tank and the secondary washing water tank in the sulfuric acid process titanium dioxide production. Specifically, pipes and pumps are used to connect the press water storage tank to the bleaching tank in the sulfuric acid process titanium dioxide production, and pipes and pumps are used to connect the press water storage tank to the secondary washing water tank in the sulfuric acid process titanium dioxide production. Preferably, when connected to the secondary washing water tank, it is connected to the inlet pipe of the secondary washing water tank. This invention adds a press water storage tank to the conventional sulfuric acid process titanium dioxide production equipment and connects the press water storage tank to the bleaching tank and the secondary washing water tank in the conventional process equipment, thereby realizing the collection of press water before the kiln and its reuse in the bleaching and secondary washing processes.

[0055] According to the present invention, a portion of the pre-kiln press water collected in the press water storage tank is reused in the bleaching process. Specifically, in the bleaching process of the washing section of the sulfuric acid process for titanium dioxide, the pre-kiln press water is first sent to the bleaching tank and mixed with the first-wash metatitanic acid slurry from the first washing process. Then, calcined seed crystals and bleaching agents are added for bleaching to obtain a bleached slurry.

[0056] The first-wash metatitanic acid slurry is derived from the first washing step in the water washing section of the sulfuric acid process for titanium dioxide production, and this invention does not impose any special restrictions on it. In this invention, the solid content of the first-wash metatitanic acid slurry is preferably 30%–38%, specifically 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, or 38%. In this invention, the kiln pre-press water and the first-wash metatitanic acid slurry are mixed and stirred evenly before pulping. The concentration of the resulting slurry is preferably 300–400 g / L, specifically 300 g / L, 310 g / L, 320 g / L, 330 g / L, 340 g / L, 350 g / L, 360 g / L, 370 g / L, 380 g / L, 390 g / L, or 400 g / L. The specific gravity of the obtained slurry is preferably 1.25 to 1.34, specifically 1.25, 1.252, 1.294, 1.336, or 1.34.

[0057] After obtaining a homogeneous slurry through the above mixing and pulping process, calcined seed crystals and a bleaching agent are added for bleaching. There are no special restrictions on the calcined seed crystals, bleaching agent, or bleaching operation; they can be carried out according to the relevant procedures of the conventional sulfuric acid process for titanium dioxide production.

[0058] According to this invention, a portion of the pre-kiln press water collected in the press water storage tank is reused in the bleaching process, while the remaining pre-kiln press water is reused in the secondary washing process. Specifically, in the secondary washing process of the sulfuric acid titanium dioxide process, the pre-kiln press water is first sent to the secondary washing tank to perform a secondary washing of the bleached slurry from the bleaching process until the pre-kiln press water is used up, and then the secondary washing water is used to continue the secondary washing process.

[0059] The phrase "sending the pre-kiln press water to the secondary washing tank" refers to sending the remaining pre-kiln press water after the bleaching process to the secondary washing tank. In this invention, the pre-kiln press water is first sent to the secondary washing tank to perform a secondary washing of the bleached slurry from the bleaching process. That is, the initial secondary washing utilizes the pre-kiln press water until it is completely reused, then conventional secondary washing water is used to continue the secondary washing until the washing is satisfactory. After the secondary washing is completed, subsequent processes can be carried out according to the conventional sulfuric acid titanium dioxide process.

[0060] As can be seen from the above, this invention collects the press water before the kiln in a press water storage tank and then reuses it in the sulfuric acid process for titanium dioxide production. This invention adds 1.5–2.0 mg / ton of [amount missing] per ton of titanium dioxide. 3 The pressed water is reused at a ratio of 1.5m. 3 1.6m 3 1.7m 3 1.79m 3 1.8m 3 1.9m 3 2.0m 3 This invention reuses the pre-kiln press water collected in the press water storage tank in two parts: one part is reused in the bleaching process, and the other part is reused in the secondary washing process. Specifically, the bleaching process consumes 0.3–1.4 m³ of press water. 3 Specifically, it can be 0.3m 3 Specifically, it can be 0.4m 3 0.5m 3 0.6m 3 0.7m 3 0.8m 3 0.84m 3 0.9m 3 1.0m 3 1.1m 3 1.2m 3 1.32m 3 1.4m 3 The remaining portion is recycled for the secondary washing process. Through this recycling method, all the collected pre-kiln press water can be reused. Furthermore, while saving water used for bleaching and pulping, the filtered metatitanic acid is recycled back into the process. Since the soluble salts in the pre-kiln press water are washed away during the secondary washing of the bleached pulp, it will not affect subsequent salt treatment and calcination. This avoids the problem of fluctuations in the salt treatment agent content, which can easily occur when directly recycled to the salt treatment process, leading to corresponding fluctuations in the quality of calcined titanium dioxide. Using this recycling method, 1.5–2.0 tons of water can be saved per ton of titanium dioxide produced. Based on this calculation, a titanium dioxide production line with an annual output of 100,000 tons can save 150,000–200,000 tons of water, significantly reducing costs.

[0061] This invention also provides a process for producing titanium dioxide using the sulfuric acid process, comprising the following steps:

[0062] Titanium dioxide is produced using the sulfuric acid process, in which the pre-kiln pressing water is reused during the production process.

[0063] The reuse method described in the preceding technical solution is employed.

[0064] In this invention, the sulfuric acid process for titanium dioxide production is not particularly limited and can be carried out according to conventional sulfuric acid process titanium dioxide production processes in the field. During the production process, the pre-kiln pressing water is reused, specifically according to the reuse method described in the preceding technical solution, which will not be repeated here.

[0065] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0066] Example 1

[0067] S1. Collect the pre-kiln press water in the sulfuric acid titanium dioxide process into a press water storage tank.

[0068] S2. Use pipes and water pumps to connect the press water storage tank to the bleaching tank and the second washing water tank in the sulfuric acid titanium dioxide process, respectively.

[0069] S3. In the bleaching process of the washing section of the sulfuric acid process for titanium dioxide, the pre-kiln press water is first sent to the bleaching tank and mixed with the first-wash metatitanic acid slurry (solid content of about 35%) from the first washing process. The mixture is stirred evenly and pulped into a slurry of about 300 g / L (slurry specific gravity of 1.252). Then, calcined seed crystals and bleaching agent are added for bleaching to obtain bleached slurry.

[0070] S4. In the second washing process of the water washing section of the sulfuric acid titanium dioxide process, the remaining kiln-front press water after the bleaching process is first sent to the second washing water tank to wash the bleached slurry from the bleaching process. The second washing is carried out until the kiln-front press water is used up, and then the regular second washing water is used to continue the second washing until the washing is qualified.

[0071] In this embodiment, the TiO2 concentration of the salt-treated slurry is 330 g / L, the solid content of the filter cake from the pre-kiln press is 55%, and approximately 2.0 m³ of press water is generated per ton of titanium dioxide. 3 All of it can be reused. Of which 1.32m 3 It is used in the bleaching and pulping process, accounting for approximately 66%, with the remaining 0.68m. 3 It is reused in the second washing process, accounting for about 34%.

[0072] Example 2

[0073] S1. Collect the pre-kiln press water in the sulfuric acid titanium dioxide process into a press water storage tank.

[0074] S2. Use pipes and water pumps to connect the press water storage tank to the bleaching tank and the second washing water tank in the sulfuric acid titanium dioxide process, respectively.

[0075] S3. In the bleaching process of the washing section of the sulfuric acid process for titanium dioxide, the pre-kiln press water is first sent to the bleaching tank and mixed with the first-wash metatitanic acid slurry (solid content of about 35%) from the first washing process. The mixture is stirred evenly and pulped into a slurry of about 350 g / L (slurry specific gravity of 1.294). Then, calcined seed crystals and bleaching agent are added for bleaching to obtain bleached slurry.

[0076] S4. In the second washing process of the water washing section of the sulfuric acid titanium dioxide process, the remaining kiln-front press water after the bleaching process is first sent to the second washing water tank to wash the bleached slurry from the bleaching process. The second washing is carried out until the kiln-front press water is used up, and then the regular second washing water is used to continue the second washing until the washing is qualified.

[0077] In this embodiment, the TiO2 concentration of the salt-treated slurry is 360 g / L, the solid content of the filter cake from the pre-kiln press is 55%, and approximately 1.79 m³ of press water is generated per ton of titanium dioxide. 3 All of it can be reused. Of which, 0.84m 3 Approximately 47% of the material is recycled for the bleaching and pulping process, with the remaining 0.95m³ used for the rest. 3 It is reused in the second washing process, accounting for about 53%.

[0078] Example 3

[0079] S1. Collect the pre-kiln press water in the sulfuric acid titanium dioxide process into a press water storage tank.

[0080] S2. Use pipes and water pumps to connect the press water storage tank to the bleaching tank and the second washing water tank in the sulfuric acid titanium dioxide process, respectively.

[0081] S3. In the bleaching process of the washing section of the sulfuric acid process for titanium dioxide, the pre-kiln press water is first sent to the bleaching tank and mixed with the first-wash metatitanic acid slurry (solid content of about 35%) from the first washing process. The mixture is stirred evenly and pulped into a slurry of about 400 g / L (slurry specific gravity of 1.336). Then, calcined seed crystals and bleaching agent are added for bleaching to obtain bleached slurry.

[0082] S4. In the second washing process of the water washing section of the sulfuric acid titanium dioxide process, the remaining kiln-front press water after the bleaching process is first sent to the second washing water tank to wash the bleached slurry from the bleaching process. The second washing is carried out until the kiln-front press water is used up, and then the regular second washing water is used to continue the second washing until the washing is qualified.

[0083] In this embodiment, the TiO2 concentration of the salt-treated slurry is 400 g / L, the solid content of the filter cake from the pre-kiln press is 55%, and approximately 1.5 m³ of pressing water is generated per ton of titanium dioxide. 3 All of it can be reused. Specifically, 0.48 m³ of press water is reused in the bleaching process. 3 Approximately 32.0% of the water used in the second washing process was recycled, with 1.02m³ of pressing water reused. 3 This accounts for approximately 78.0%.

[0084] All of the pressing water in Examples 1-3 above can be reused, saving 1.5 to 2.0 tons of water per ton of titanium dioxide.

[0085] Comparative Example 1

[0086] Implemented according to Example 1, except that the water pressed before the kiln is not reused, and all fresh water is used instead.

[0087] The trace element results of the two-wash metatitanic acid obtained after two washes in each embodiment and comparative example are shown in Table 1.

[0088] Table 1: Trace Elements in Diwashed Metatitanic Acid

[0089] Example 1 ＜0.01 0.026 ＜0.002 ＜0.01 Example 2 ＜0.01 0.027 ＜0.002 ＜0.01 Example 3 ＜0.01 0.028 ＜0.002 ＜0.01 Comparative Example 1 ＜0.01 0.027 ＜0.002 ＜0.01

[0090] As shown in Table 1, the trace element results indicate that after reusing the pre-kiln press water for bleaching, pulping, and secondary washing, the trace element content of metatitanic acid obtained in the secondary washing was not significantly different from that obtained using only fresh water. This demonstrates that reusing the pre-kiln press water does not affect the washing effect. Therefore, this invention effectively saves water, reduces water consumption, and does not adversely affect the quality of titanium dioxide.

[0091] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of these embodiments are merely to aid in understanding the method and core ideas of the present invention, including the best mode, and to enable any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to those expressed in the claims, or if they include equivalent structural elements that are not substantially different from those expressed in the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A method for recycling press water before the sulfuric acid process titanium dioxide kiln, characterized in that, Includes the following steps: S1. Collect the pre-kiln press water in the sulfuric acid titanium dioxide process into a press water storage tank. S2. Connect the press water storage tank to the bleaching tank and the second washing water tank in the sulfuric acid titanium dioxide process, respectively. S3. In the bleaching process of the washing section of the sulfuric acid process for titanium dioxide, the kiln-front press water is first sent to the bleaching tank and mixed with the first-wash metatitanic acid slurry from the first washing process. Then, calcined seed crystals and bleaching agent are added for bleaching to obtain bleached slurry. S4. In the second washing process of the water washing section of the sulfuric acid titanium dioxide process, the pre-kiln press water is first sent to the second washing water tank to wash the bleached slurry from the bleaching process until the pre-kiln press water is used up, and then the second washing water is used to continue the second washing.

2. The reuse method according to claim 1, characterized in that, In step S2, the press water storage tank is connected to the bleaching tank in the sulfuric acid titanium dioxide process using pipes and water pumps.

3. The reuse method according to claim 1, characterized in that, In step S2, the press water storage tank is connected to the second washing water tank in the sulfuric acid titanium dioxide process using pipes and water pumps.

4. The reuse method according to claim 1 or 3, characterized in that, In step S2, the press water storage tank is connected to the inlet pipe of the second washing water tank in the sulfuric acid titanium dioxide process using pipes and water pumps.

5. The reuse method according to claim 1, characterized in that, In step S3, the solid content of the first-washed metatitanic acid slurry is 30% to 38%.

6. The reuse method according to claim 1, characterized in that, In step S3, the concentration of the pulp obtained by pulping is 300-400 g / L.

7. The reuse method according to claim 1, characterized in that, In step S3, the specific gravity of the pulp obtained by pulping is 1.25 to 1.

34.

8. The reuse method according to claim 1, characterized in that, The present application adds 1.5-2.0 m 3 The present application adds 1.5-2.0 m 3 The present application adds 1.5-2.0 m 9. The reuse method according to claim 1, characterized in that, The pre-kiln press water is obtained by pressing and dehydrating metatitanic acid after salt treatment in the sulfuric acid process for titanium dioxide production.

10. A process for producing titanium dioxide using the sulfuric acid process, characterized in that, Includes the following steps: Titanium dioxide is produced using the sulfuric acid process, in which the pre-kiln pressing water is reused during the production process. The reuse method described herein employs any one of claims 1 to 9.

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