Method for utilizing waste acid water

Abstract

The invention discloses a method for utilizing waste acid water, relates to the technical field of titanium dioxide production, and aims to solve the technical problems that treatment of waste acid water generated in the titanium dioxide production process in the prior art is not environment-friendly and high in cost. The method comprises the following steps: S1, collecting acidic wastewater generated in the production process of producing titanium dioxide by a sulfuric acid method, and flocculating and layering the collected acidic wastewater; s2, filtering supernatant liquid of the layered acid wastewater, and conveying the filtered supernatant liquid to a hydrolysis section; s3, taking the acid wastewater as dilution water in a hydrolysis section, and concentrating the acid wastewater; and S4, concentrating the acidic wastewater obtained in S3 again, and returning the concentrated acidic wastewater to an acidolysis section for acidolysis. According to the method, the acid wastewater generated in titanium dioxide production is used as dilution water in the hydrolysis process, so that waste acid water is circulated, raw materials are saved, the production cost is reduced, and economic benefits are increased; the waste acid water is subjected to environment-friendly treatment, and the green production concept is met.

Description

Technical Field

[0001] The invention belongs to the field of titanium dioxide production, and particularly relates to a method for utilizing waste acid water. Background Art

[0002] Titanium dioxide is an important inorganic chemical pigment, the main component of which is titanium dioxide (TiO2). Due to its special properties, titanium dioxide is used in coatings, inks, papermaking, plastics and rubber, chemical fibers, ceramics and other industries. There are two production processes for titanium dioxide: sulfuric acid process and chlorination process.

[0003] When titanium dioxide is produced by the sulfuric acid method, titanium ore is used as raw material, and sulfuric acid is used to acidolyze the titanium element in the titanium ore into a TiOSO4 solution. The insoluble impurities in the titanium liquid are removed by sedimentation, filtration, etc., and then the FeSO47H2O in the titanium liquid is removed by crystallization and solid-liquid separation. After concentration, it is thermally hydrolyzed to obtain titanic acid slurry. Soluble sulfates and heavy metal impurities are removed through water washing, bleaching and other processes. After adding a crystal conversion aid and filtering, calcination, dehydration, desulfurization, conversion, etc. are performed to obtain anatase or rutile primary titanium dioxide. The primary titanium dioxide product is dry-ground to obtain anatase product and an uncoated rutile primary product.

[0004] A large amount of acidic wastewater is generated during the production of titanium dioxide. Currently, the main method for treating this part of acidic wastewater is neutralization. However, the neutralization method for treating acidic wastewater will produce a large amount of titanium gypsum during the treatment process. Titanium gypsum is difficult to stack and has high treatment costs, and it is difficult to achieve comprehensive utilization of titanium gypsum in the short term. Therefore, the neutralization method for treating acidic wastewater is not environmentally friendly and cumbersome in the subsequent treatment of titanium gypsum, and this treatment method requires the use of a neutralizer, which increases the production cost of titanium dioxide. At present, there is also a treatment method of recovering the concentrated waste acid by steam concentration of acidic wastewater, but due to the low acid concentration of acidic wastewater, direct concentration will increase the consumption of steam, thereby increasing production costs. Summary of the invention

[0005] The invention discloses a method for utilizing waste acid water, and is intended to solve the technical problems of the prior art in treating waste acid water generated in the process of titanium dioxide production, which is not environmentally friendly and has high cost.

[0006] In order to solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] A method for utilizing waste acid water comprises the following steps:

[0008] S1: Collect the acidic wastewater generated in the production process of titanium dioxide by sulfuric acid method, and flocculate and stratify the collected acidic wastewater;

[0009] S2: filtering the supernatant of the acidic wastewater after stratification, and transporting the filtered supernatant to the hydrolysis section;

[0010] S3: using the acidic wastewater as dilution water in the hydrolysis section to concentrate the acidic wastewater;

[0011] S4: The acidic wastewater obtained in S3 is concentrated again and then returned to the acid hydrolysis section for acid hydrolysis.

[0012] After adopting this technical solution, the acidic wastewater generated in the production process of titanium dioxide by sulfuric acid method first enters the collection device, and then enters the stratification device through the collection device. Flocculant is added to the stratification device for stratification, and the supernatant produced by stratification enters the filtering device through the overflow port on the stratification device. The filtering device filters out the solid content in the supernatant. The filtered supernatant is transported to the hydrolysis tank and serves as dilution water in the hydrolysis section.

[0013] The amount of acidic wastewater added to the hydrolysis device changes with the concentration of the acidic wastewater, so that the appropriate amount of acidic wastewater added during the hydrolysis process can replace the original dilution water without affecting the hydrolysis rate and product concentration. After hydrolysis, the acidic wastewater increases the acid content in the hydrolysis end material to become concentrated acidic wastewater, which is convenient for re-concentration into waste acid in the subsequent concentration process, and the waste acid returns to the acid hydrolysis process for acid hydrolysis.

[0014] The method can save the raw materials needed in the process of producing titanium dioxide by sulfuric acid method, such as the amount of dilution water and acid, thereby reducing the production cost and increasing the economic benefits. At the same time, the method is used to treat acidic wastewater, which can reduce the difficult-to-treat additional products produced in the neutralization treatment method, has less impact on the environment, and is more environmentally friendly.

[0015] The acidic wastewater collected in S1 is secondary washing wastewater with an acid concentration of 4-7% produced by secondary washing in the water washing section.

[0016] After adopting this technical solution, the first wash in the water washing section produces a first wash waste acid with an acid concentration of 18-20%. The first wash waste acid is collected in the first collecting tank and can be directly concentrated in the concentration program after filtering and other solid removal treatments. It can quickly reach the concentration of the acidic waste water that needs to be concentrated again in S4, and improve the speed of acid waste acid treatment; the first wash waste acid can also enter the hydrolysis program after the same treatment as the second wash waste water produced by the second wash, but the effect of hydrolysis on the concentration of the first wash waste acid is not high and will affect the hydrolysis rate of hydrolysis. Therefore, this method considers concentrating the second wash waste water produced by the second wash; the acid concentration of the second wash waste water produced by the second wash is low, which is close to the concentration of the original dilution water. After treatment, it can be directly transported to the hydrolysis program for hydrolysis. After increasing the acid concentration of the second wash waste water, it is then transported to the concentration program for concentration, which can save raw materials.

[0017] Among them, the acidic wastewater in S1 is flocculated and stratified in the thickener.

[0018] After adopting this technical solution, the secondary wash wastewater is collected in the second collecting tank, and the secondary wash wastewater in the second collecting tank is transported to the thickener, where flocculant is added for stratification, and the upper clear liquid after stratification passes through the overflow port on the thickener and overflows into the filter device.

[0019] The first wash waste acid produced by the first wash is collected in the first collection tank and treated separately from the second wash waste water produced by the second wash, which can improve the treatment efficiency of the first wash waste acid and the second wash waste water. Flocculants are added to the thickener to directly stratify and precipitate the waste water by flocculation, and the supernatant produced by stratification is transported to the filter device by overflow for filtration. This method of first flocculating and stratifying, and then filtering and removing impurities can improve the production efficiency of the supernatant while effectively reducing the solid content in the supernatant. Finally, the production efficiency of acidic waste water that can be used in the hydrolysis process is improved, achieving the purpose of saving water.

[0020] Among them, in S2, a CN filter is used to filter the supernatant.

[0021] After adopting this technical solution, the stratified upper clear liquid is filtered through a CN filter, and the solid content in the filtered upper clear liquid is between 0.002% and 0.007%, which effectively reduces the solid matter in the upper clear liquid and thus reduces the amount of fixed matter generated as undesirable products in the subsequent hydrolysis process.

[0022] The acidic wastewater is a mixture of first-wash waste acid produced by the first wash and second-wash wastewater produced by the second wash, and the concentration of the mixture is 8-15%.

[0023] After adopting this technical solution, when the production site is limited by space, the first wash waste acid and the second wash waste water can be mixed to produce a mixture with an acid concentration of 8-15%, and then the mixture is also layered and filtered, and the upper clear liquid after filtration is taken and sent to the hydrolysis process to participate in hydrolysis, saving space in the production process. The method for recycling the waste acid water described in this method can also be realized in a small space. Therefore, the mixing of the first wash waste acid and the second wash waste water improves the practicality of this method.

[0024] In S4, the concentrated acidic wastewater obtained in S3 is added to the maturation process of the hydrolysis section.

[0025] After adopting this technical scheme, the hydrolysis process is carried out in a hydrolysis pot. The bottom of the hydrolysis pot is provided with pipelines, delivery pumps, valves, switches and other necessary transportation devices for transporting hydrolysis products. The material to be hydrolyzed is first added to the hydrolysis pot, and acidic wastewater is added during the maturation process of hydrolysis. After the hydrolysis is completed, the titanium dioxide (TiO2), concentrated acidic wastewater and molten metal salt produced in the hydrolysis pot are all removed from the hydrolysis pot through pipelines and delivery pumps to a first washing filter press for washing. Clean water is added to the washed titanium dioxide (TiO2) again and enters a second washing filter press for washing. The above process is repeated to hydrolyze and wash new materials.

[0026] The materials added are titanium liquid and seed crystals, and the amounts of titanium liquid and seed crystals added are 75m3 and 1.68m3 respectively. After the hydrolysis is completed, titanium dioxide (TiO2) and concentrated acidic wastewater are generated in the hydrolysis pot. The concentration of titanium dioxide (TiO2) is 155-169g / L. The concentration of the first waste acid generated after the hydrolysis material is washed and filtered is 20%-24%.

[0027] After adopting this technical solution, the seed crystal is made of 1.68m3 of titanium liquid and 0.5m3 of sodium hydroxide, the concentration of sodium hydroxide is 32%, and the quantitative addition of titanium liquid and seed crystals, sodium hydroxide and acidic wastewater can ensure that the hydrolysis rate is above 96% without reducing the concentration of the generated titanium dioxide (TiO2). The final output of titanium dioxide (TiO2) is 80-83m3, and the concentration of acidic wastewater can also be increased. Reduce the waste of raw materials, thereby improving production quality and efficiency.

[0028] After hydrolysis, the materials in the first hydrolysis pot are transported to the first washing filter press through the pipe and pump at the bottom of the hydrolysis pot for squeezing to remove the waste acid and molten metal salt in the hydrolysis product. This structure can simplify the transportation of the hydrolysis product and is more convenient to use. The titanium dioxide (TiO2) solid produced after washing in the first washing filter press is sent to the third collecting tank, clean water is added to the third collecting tank for slurrying, and then the slurry is transported to the second washing filter press for filtration to remove other impurities in the titanium dioxide (TiO2). This water washing and filtration method can gradually reduce impurities in the product and reduce pollution.

[0029] The concentration of the acidic wastewater obtained in S3 is 20-24%, and the concentration of the waste acid obtained after further concentration in S4 is 30%-33%.

[0030] After adopting this technical solution, the acidic wastewater in S3 is concentrated in S4, and the concentrated acidic wastewater is transported to the acid hydrolysis process to participate in acid hydrolysis, which can reduce the amount of acid originally required to participate in the acid hydrolysis process, thereby achieving the purpose of saving acid usage and reducing production costs.

[0031] Among them, in S4, the acidic wastewater is re-concentrated in the form of steam concentration, and the steam comes from boiler steam and thermal power steam.

[0032] After adopting this technical solution, excess steam will be generated in the boilers of other processes such as acid hydrolysis, hydrolysis and calcination. The excess steam generated becomes the steam required in the concentration process, which can save energy.

[0033] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0034] (1) The acidic wastewater in the titanium dioxide production process is used to replace the dilution water in the hydrolysis process, which saves water usage, reduces the cost consumption in the production process, and thus improves economic benefits.

[0035] (2) The acidic wastewater in the titanium dioxide production process is used to replace the dilution water in the hydrolysis process, thereby realizing the comprehensive utilization of resources and the green treatment of the acidic wastewater, which is in line with the green production concept.

[0036] (3) The acidic wastewater after hydrolysis and concentration is concentrated and returned to the acid hydrolysis section for acid hydrolysis, thereby realizing the recycling of resources and improving economic benefits.

[0037] (4) The collected acidic wastewater is filtered and precipitated, and then the supernatant is hydrolyzed, which can increase the rate of acidic wastewater treatment and achieve production capacity optimization. DETAILED DESCRIPTION

[0038] To make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. Usually the embodiments of the present application can be arranged and designed in various configurations. Therefore, the detailed description of the embodiments of the present application below is not intended to limit the scope of the application claimed for protection, but merely represents the selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application.

[0039] In the description of the embodiments of the present application, it should be noted that the terms "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. indicate positions or positional relationships based on the shown positions or positional relationships, or the positions or positional relationships in which the invented product is usually placed when in use, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0040] The technical solution of the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0041] In the following examples, the acidic wastewater is produced from the sulfuric acid process to produce titanium dioxide, and the mixture is a mixture of the second wash wastewater collected during the second wash process and the first waste acid produced by the first wash and the second wash wastewater. The acid concentration of the first wash waste acid produced by the first wash is 18-20%, the acid concentration of the second wash wastewater produced by the second wash is 4-7%, and the acid concentration of the mixture obtained by mixing the two is 8-15%. First, the hydrolyzate is transported to the first wash press through a pump and a pipeline to remove the waste acid and molten metal salts, and the remaining titanium dioxide (TiO2) fixed matter is added with new clean water and input into the second wash filter press for second washing, thereby obtaining the second wash wastewater and the cleaned titanium dioxide (TiO2) solid matter. All the secondary wash wastewater is transported to the second collecting tank, and all the secondary wash wastewater is transported to the thickener to add flocculants for stratification. The upper clear liquid after stratification overflows through the filter holes on the thickener and enters the CN filter to be filtered. The solid content of the filtered upper clear liquid is between 0.002% and 0.007%. The upper clear liquid is then returned to the hydrolysis pot to participate in the hydrolysis in the maturation stage of hydrolysis.

[0042] In addition, in this embodiment, in order to confirm the role of acidic wastewater in the hydrolysis process, dilution water is added as a comparative example, and in order to determine the effect of acidic wastewater concentration on hydrolysis, a washing waste acid is added as a comparative example. After the hydrolysis is completed, the qualified value of the hydrolysis rate of the sample water is 96%, and the concentration of titanium dioxide (TiO2) is 155-169g / L after the hydrolysis is completed. The acid concentration of the concentrated acidic wastewater that reaches the qualified hydrolysis rate after hydrolysis is 20-24%.

[0043] Comparative Examples and Examples are shown in the following table

[0044]

[0045]

[0046]

[0047] The method of the present invention realizes environmentally friendly treatment of acidic wastewater in the production process of metatitanic acid, reduces environmental pollution, and saves the amount of dilution water. Compared with dilution water, the secondary washing wastewater after secondary washing, such as Example 1 (the concentration is generally about 5%), can achieve the same 96% hydrolysis rate and 167g / L TiO2 concentration as the dilution water added during the hydrolysis process shown in Comparative Example 1 as long as the addition amount reaches 6m3. After the addition amount reaches 11m3, the TiO2 concentration will be lower than 155g / L.

[0048] The mixture of the first wash waste acid and the second wash waste water (the concentration is generally around 5-15%) is added in different amounts depending on the concentration. At concentrations of 10% and 15%, as in Examples 6 and 8, the addition amounts of 9m3 and 11m3, respectively, can achieve a hydrolysis rate of 96% and a TiO2 concentration of 155-169g / L.

[0049] The first wash waste acid produced by the first wash can also be used for hydrolysis, but when the hydrolysis rate reaches 96%, the TiO2 concentration is 152.53g / L, which does not meet the requirements, and when the TiO2 concentration reaches 155g / L, the hydrolysis rate cannot reach 96%. Therefore, it is not considered to directly use the first wash waste acid as dilution water to add it into the hydrolysis process for hydrolysis, and it is preferred to use the second wash waste water and the mixture of the first wash waste acid and the second wash waste water for hydrolysis.

[0050] Therefore, when the acid concentration of the acidic wastewater is between 5-15%, the amount of acidic wastewater added is between 6-12m3, and the qualified value of the hydrolysis rate of the sample water after the hydrolysis is completed can reach 96%, and the concentration of titanium dioxide (TiO2) is 155-169g / L. The same hydrolysis rate as the diluted water is achieved, the concentration of the product is guaranteed, and the acidic wastewater can be concentrated at the same time, thereby improving the treatment rate of the acidic wastewater.

[0051] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for utilizing waste acid water, characterized in that: The following steps are involved: S1: Collect the acidic wastewater generated in the production process of titanium dioxide by sulfuric acid method, and flocculate and stratify the collected acidic wastewater; S2: filtering the supernatant of the acidic wastewater after stratification, and transporting the filtered supernatant to the hydrolysis section; S3: using the acidic wastewater as dilution water in the hydrolysis section to concentrate the acidic wastewater; S4: The acidic wastewater obtained in S3 is concentrated again and then returned to the acid hydrolysis section for acid hydrolysis.

2. The method for utilizing waste acid water according to claim 1, characterized in that: The acidic wastewater collected in S1 is secondary washing wastewater with an acid concentration of 4-7% produced by secondary washing in the water washing section.

3. The method for utilizing waste acid water according to claim 1, characterized in that: The acidic wastewater in S1 is flocculated and stratified in the thickener.

4. The method for utilizing waste acid water according to claim 1, characterized in that: In S2, the supernatant was filtered using a CN filter.

5. The method for utilizing waste acid water according to claim 1, characterized in that: The acidic wastewater is a mixture of first wash waste acid produced by the first wash and second wash wastewater produced by the second wash, and the concentration of the mixture is 8-15%.

6. The method for utilizing waste acid water according to any one of claims 1 to 5, characterized in that: In S4, the concentrated acidic wastewater obtained in S3 is added to the maturation process of the hydrolysis section.

7. The method for utilizing waste acid water according to any one of claims 1 to 5, characterized in that: The concentration of the acidic wastewater obtained in S3 is 20-24%, and the concentration of the waste acid obtained after further concentration in S4 is 30%-33%.

8. The method for utilizing waste acid water according to any one of claims 1 to 5, characterized in that: In S4, the acidic wastewater is concentrated again by steam concentration.

9. The method for utilizing waste acid water according to claim 8, characterized in that: The steam for the steam concentration is derived from thermal power steam and boiler steam.

10. The method for utilizing waste acid water according to any one of claims 1 to 5, characterized in that: When the acid concentration of the acidic wastewater is between 5-15%, the amount of acidic wastewater added is 6-12m3.

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