Device for treating sodium hypochlorite waste liquid in chlorination process titanium dioxide oxidation process

Abstract

The utility model discloses a sodium hypochlorite waste liquid treatment device for a chlorination process titanium dioxide oxidation process, which relates to the technical field of titanium dioxide production waste liquid recovery and treatment and comprises a sodium hypochlorite storage tank, a thick slurry tank, filtering equipment and a clear liquid tank. An outlet of the filtering device is connected with an inlet of the clear liquid tank, the filtering device is a filter press, an outlet is formed in the bottom of the thick slurry tank and connected with an inlet of the filter press, and the clear liquid tank is used for storing qualified filtrate filtered out by the filter press. When the device is used, a natural settling process does not need to be waited, sodium hypochlorite waste liquid collected in the sodium hypochlorite storage tank can be directly fed into the thick slurry tank through the bottom outlet, and solid-liquid separation operation is performed by using the filter press, so that complete recovery treatment of waste alkali liquid in a titanium dioxide tail gas oxidation process is realized; the clarified sodium hypochlorite solution and the titanium dioxide filter cake after filter pressing can be sold as products.

Description

Technical Field

[0001] The utility model relates to the technical field of recycling and treating waste liquid from titanium dioxide production, in particular to the technical field of a treatment device for sodium hypochlorite waste liquid from a titanium dioxide oxidation process using a chloride method. Background Art

[0002] In recent years, my country's high-end titanium industry has developed rapidly, and the main methods for producing titanium dioxide are the sulfuric acid method and the chlorination method. During the oxidation process of titanium dioxide produced by the chloride method, alkaline solution is required to absorb the residual chlorine in the exhaust gas, which will produce sodium hypochlorite. This process includes: the chlorine displaced when taking dry powder samples, the chlorine entering the slurry tank, the chlorine-containing exhaust gas from the chlorine pipeline of the displacement oxidation device, and the unreacted titanium tetrachloride in the early stage of the chlorination process are all fed into the exhaust gas scrubber. Sodium hydroxide solution is used to absorb the chlorine in the exhaust gas to produce sodium hypochlorite until the alkaline solution reaches the specified concentration, resulting in a sodium hypochlorite solution containing titanium dioxide. Because this sodium hypochlorite solution is a solid-containing liquid, its main components are sodium hypochlorite solution, a small amount of sodium hydroxide, and titanium dioxide entering the exhaust system from the slurry tank. Since the solution contains extremely fine titanium dioxide and has a low concentration, ordinary precipitation and filtration are often unable to completely separate the titanium dioxide from the sodium hypochlorite solution. The sodium hypochlorite solution is turbid and does not meet the product sales requirements. Sodium sulfite is usually required for neutralization reaction, which has high environmental treatment costs. In addition, the titanium dioxide slurry containing sodium hypochlorite cannot be recycled, resulting in a waste of resources. In addition, when the amount of sodium hypochlorite produced is large, it will also result in a high inventory, which may lead to problems such as production suspension due to inability to process the solution.

[0003] Chinese patent application number CN202223376671.7 discloses a waste alkali liquor treatment device for the chloride process of titanium dioxide oxidation, comprising a waste alkali liquor settling tank with a concentrated slurry outlet and a suspension outlet, respectively. The concentrated slurry outlet is connected to the inlet of a concentrated slurry storage tank via a pipeline, which is connected to the inlet of a concentrated slurry reaction tank via a pipeline equipped with a first concentrated slurry pump. The concentrated slurry reaction tank is also equipped with a reducing agent inlet. The suspension outlet is connected to the inlet of a raw material tank via a pipeline, and a circulation line of a circulating pump is connected between the outlet of the raw material tank and the inlet of a membrane filtration device. The outlet of the circulating pump is connected to the inlet of the concentrated slurry storage tank via a concentrated liquid recovery pipeline, and the outlet of the membrane filtration device is connected to the inlet of the clear liquid storage tank and the inlet of the raw material tank, respectively. The treatment device first separates the waste alkali liquor into a concentrated slurry at the bottom and a suspended liquid at the top through natural sedimentation. The two are then treated and reused using a reducing agent and a membrane filtration device, respectively, to achieve the recycling of titanium dioxide and sodium hypochlorite solution. However, the application adopts a membrane filtration device to treat sodium hypochlorite, which has high operating costs and low treatment efficiency. It also requires the addition of additional reagents to treat the concentrated slurry. The titanium dioxide recovery process is also more complicated, further increasing the cost.

[0004] In summary, while existing technologies propose treating and recycling sodium hypochlorite from titanium dioxide chloride, the high oxidizing properties of the sodium hypochlorite wastewater after alkali washing make treatment costly, and the fine titanium dioxide particles present in the wastewater difficult to separate make the recovery of the sodium hypochlorite and titanium dioxide difficult, resulting in resource waste. Therefore, how to efficiently treat the sodium hypochlorite from titanium dioxide chloride, reduce environmental costs, and achieve resource recycling has become a pressing technical challenge for those skilled in the art. Utility Model Content

[0005] Aiming at the problem of recovering sodium hypochlorite and titanium dioxide from the sodium hypochlorite waste liquid obtained by using alkaline solution to clean the waste gas during the production of titanium dioxide by the chloride process, the purpose of this application is to provide a titanium dioxide chloride and sodium hypochlorite treatment device that can perform solid-liquid separation on the sodium hypochlorite waste liquid in the production process of titanium dioxide by the chloride process to obtain a clarified sodium hypochlorite solution and titanium dioxide that can be sold.

[0006] The technical solution adopted by the present application to solve its technical problems is: a sodium hypochlorite waste liquid treatment device for the chloride process of titanium dioxide oxidation, comprising a sodium hypochlorite storage tank, a concentrated slurry tank, a filtering device, and a clear liquid tank. The bottom outlet of the sodium hypochlorite storage tank is connected to the inlet of the concentrated slurry tank, the outlet of the filtering device is connected to the inlet of the clear liquid tank, the filtering device is a filter press, the bottom of the concentrated slurry tank is provided with an outlet connected to the inlet of the filter press, and the clear liquid tank is used to store qualified filtrate filtered out by the filter press.

[0007] Since the sodium hypochlorite waste liquid after alkali washing is mixed with fine titanium dioxide, the traditional separation and treatment strategy is often to wait for the suspension to settle naturally. However, this process is not only time-consuming and has poor sedimentation effect, but the upper liquid and lower concentrated slurry still need further treatment to obtain sodium hypochlorite with the required clarity and titanium dioxide that can be sold without sodium hypochlorite. The treatment device of the present application does not need to wait for the natural sedimentation process. The sodium hypochlorite waste liquid collected in the sodium hypochlorite storage tank is directly sent to the concentrated slurry tank through the bottom outlet. A filter press is used for solid-liquid separation operation, which can directly obtain recyclable filtrate and filter cake. The sodium hypochlorite filtrate with qualified clarity is collected in a clear liquid tank for takeout. There is no need to add additional reducing agent to consume sodium hypochlorite. The filter cake can be directly collected and sold.

[0008] The outlets of the sodium hypochlorite storage tank and the concentrated slurry tank of the present application are both arranged at the bottom of the tank body, so that the solid content of the sodium hypochlorite concentrated slurry entering the concentrated slurry tank and the filter press is relatively high. Since the filter press uses filter cloth in combination with mechanically generated pressure for filtration, during the process the filtrate flows out while the solids remain on one side of the filter cloth. The high degree of solid enrichment in the waste liquid can result in more solids remaining on the filter cloth, which can increase the pressure of the filter press. In addition, the fine particles of titanium dioxide also play a certain filtering role. The combination of the two can, to a certain extent, make the early filtration effect of the sodium hypochlorite waste liquid better and improve the recovery efficiency.

[0009] It is worth noting that in the conventional process of sodium hydroxide absorbing chlorine to produce sodium hypochlorite, no solid material enters and no filtration is required. However, for the titanium dioxide production industry, the sodium hypochlorite waste liquid contains a certain amount of titanium dioxide solids. The process of recovering sodium hypochlorite requires the control of the solid content. In addition, since sodium hypochlorite is easily decomposed by light, it will produce a strong odor and cause environmental pollution. Conventional means usually do not use filtration to dispose of the sodium hypochlorite waste liquid.

[0010] The technical solution of this application is the first to use a filter press to dispose of waste liquid. Except for the operation of unloading the filter cake, the rest of the process is carried out in a closed environment, which greatly reduces the probability of sodium hypochlorite decomposition. In addition, in the early stage of filtration by the filter press, because the filter cloth contains many holes, the sodium hypochlorite filtrate filtered out is mostly turbid. As the filtration continues, dense titanium dioxide particles (most of the particle size of titanium dioxide is 100-300nm) can be formed on the filter cloth and filtered again, which can ensure the filtration quality of sodium hypochlorite. Secondly, for the treatment of sodium hypochlorite waste liquid produced by titanium dioxide, the single processing capacity of the filter press is large and only the filter cloth needs to be replaced, which can reduce the costs of procurement and maintenance, and the product quality is stable. At the same time, the filter cake obtained is in a solid state, which reduces post-processing operations such as crystallization and is more convenient for recycling.

[0011] Furthermore, the filter press is provided with a turbid liquid outlet, which is connected to the inlet of the thick slurry tank. The filter press is provided with a sight glass for observing the turbidity of the filtrate of the filter press.

[0012] A circulation loop is added between the filter press and the thick liquid tank. Since the liquid flowing out is turbid during the loading of the filter press and the initial stage of filtration, the turbid liquid is first returned to the thick liquid tank for recovery. After the filtrate is observed to be clear in the sight glass, the valve is switched to send the qualified filtrate to the clear liquid tank for continued filtration. This can fully recycle resources, and the secondary filtration makes the filtration and recovery effects better.

[0013] Furthermore, the clear liquid tank is provided with two outlets, which are respectively connected to the inlet of the storage tank and the inlet of the sodium hypochlorite storage tank. The storage tank is used to store the qualified sodium hypochlorite solution in the clear liquid tank.

[0014] A storage tank is set up after the filter press and the clear liquid tank to store the clarified, qualified sodium hypochlorite solution available for sale. The clear liquid tank itself has a buffering effect, preventing the sodium hypochlorite solution from becoming turbid due to damage to the filter cloth, and further controlling the quality of the sodium hypochlorite sold. Due to long-term use of the filter press or puncture of the contents, the filter cloth will be damaged, resulting in turbidity in the filtrate. This turbidity is often difficult to detect with the naked eye through the filter press's pipeline sight glass. The clear liquid tank is used to temporarily store the filtrate from the filter press. After a certain amount of liquid is stored, a sample is taken for testing. If the clarity meets the requirements, the qualified sodium hypochlorite solution is transported to the storage tank. If it becomes turbid, it is returned to the sodium hypochlorite storage tank. The damaged filter cloth is replaced before the filter press operation is carried out.

[0015] In the technical solution of this application, in addition to returning the turbid filtrate caused by filter cloth puncture to the sodium hypochlorite storage tank, this portion of liquid can also be sent to the thick slurry tank for filtration. In actual operation, because sodium hypochlorite storage tanks are often used for storage and have a large capacity, they can provide more time for filter cloth replacement. In addition, the sodium hypochlorite storage tank is designed with a cone structure, which can play a certain role in sedimentation, allowing the high solid content to be filtered, resulting in better filtration effect.

[0016] Use storage tanks to store sodium hypochlorite with qualified clarity, take samples of the solution in the storage tanks for analysis, and sell it out after the sodium hypochlorite and iron content meet the standards. Further quality control can be performed on the sodium hypochlorite sold out, so that the quality of the sodium hypochlorite sold out is better.

[0017] Furthermore, there are two sodium hypochlorite storage tanks, namely sodium hypochlorite storage tank A and sodium hypochlorite storage tank B. The bottom outlet of the sodium hypochlorite storage tank A and the bottom outlet of the sodium hypochlorite storage tank B are both connected to the inlet of the thick slurry tank.

[0018] Two storage tanks are used to collect waste alkali and sodium hypochlorite. In addition to increasing the storage capacity of sodium hypochlorite, one of the tanks can be used as a backup tank. Normally, only one tank is used. This can be used to increase storage capacity in special situations, such as when hazardous chemicals cannot be transported on holidays. Similarly, multiple storage tanks can be installed or their capacity can be expanded based on the process.

[0019] Furthermore, the filter press has a diaphragm pressing function and uses an antioxidant filter cloth.

[0020] The filter press used in the treatment device of this application is equipped with a diaphragm pressing function, which can significantly remove moisture from the filter cake, achieving excellent filtration results, ensuring a low moisture content in the filter cake, and reducing the decomposition of sodium hypochlorite. Furthermore, due to the strong oxidizing properties of sodium hypochlorite, the use of ordinary filter cloth will result in significant wear and tear over time. Choosing an anti-oxidation filter cloth can reduce the frequency of replacement and extend the service life.

[0021] Compared with the existing technology, the beneficial effects of the utility model are: it can realize the complete recovery and treatment of the waste alkali liquid in the titanium dioxide tail gas oxidation process, and the clarified sodium hypochlorite solution and the titanium dioxide filter cake after filtration can be sold as products, achieving zero discharge of waste liquid in the oxidation process while converting the negative expenditure of waste liquid treatment into positive income, thereby reducing costs and increasing efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following is a brief introduction to the drawings required for use in the embodiments and comparative examples. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 This is a schematic diagram of a titanium dioxide sodium hypochlorite treatment device according to an embodiment of the present application.

[0024] Icon: 1-sodium hypochlorite storage tank; A and B are sodium hypochlorite storage tank A and sodium hypochlorite storage tank B respectively; 2-thick slurry tank; 3-clear liquid tank; 4-filter press; 5-storage tank; 6-turbid liquid outlet. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical scheme and advantages of the embodiment of the present application clearer, the technical scheme in the embodiment of the present application will be clearly and completely described below in conjunction with the accompanying drawings of the application. Obviously, the described embodiment is only a part of the embodiment of the application, rather than all of the embodiments. The components of the embodiment of the present application described and shown in the accompanying drawings can be arranged and designed in various configurations. If specific conditions are not specified in the embodiment, proceed according to the conditions recommended by normal conditions or manufacturers. If the manufacturer is not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0026] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The technical solution of this application will be described in detail below with reference to specific embodiments.

[0027] A sodium hypochlorite waste liquid treatment device for a titanium dioxide oxidation process using a chloride process, comprising a sodium hypochlorite storage tank 1, a concentrated slurry tank 2, a filtering device, and a clear liquid tank 3. The bottom outlet of the sodium hypochlorite storage tank 1 is connected to the inlet of the concentrated slurry tank 2, the outlet of the filtering device is connected to the inlet of the clear liquid tank 3, the filtering device is a filter press 4, an outlet is provided at the bottom of the concentrated slurry tank 3 and is connected to the inlet of the filter press 4, and the clear liquid tank 3 is used to store qualified filtrate filtered out by the filter press 4.

[0028] The waste alkali liquid used to treat the exhaust gas from titanium dioxide production flows through the sodium hypochlorite storage tank 1, the thick slurry tank 2, and the filter press 4 in sequence. After the solid-liquid separation is completed by the filter press, the qualified filtrate is sent to the clear liquid tank 3.

[0029] The filter press 4 is provided with a turbid liquid outlet 6 , which is connected to the inlet of the thick slurry tank 2 . The filter press 4 is provided with a sight glass for observing the turbidity of the filtrate of the filter press 4 .

[0030] During the loading and initial filtration of the filter press 4, use a sight glass to observe that the outflowing liquid is usually turbid. First, open the turbid liquid outlet 6 to allow the turbid liquid to return to the thick slurry tank 2 for recovery. After the filtrate of the filter press 4 is observed to be clear through the sight glass, switch the valve to connect the filtrate outlet of the filter press 4 to the clear liquid tank 3, and continue the filtration operation. The qualified filtrate obtained will be sent to the clear liquid tank 3 for temporary storage.

[0031] The clear liquid tank 3 is provided with two outlets, which are respectively connected to the inlet of the storage tank 5 and the inlet of the sodium hypochlorite storage tank 1. The storage tank 5 is used to store the qualified sodium hypochlorite solution in the clear liquid tank 3.

[0032] The qualified filtrate filtered out by the filter press 4 enters the clear liquid tank 3. After the liquid level in the clear liquid tank 3 reaches 80% of the tank body, the sodium hypochlorite in the clear liquid tank 3 is sampled. If the filter cloth is not perforated, the sodium hypochlorite solution is clear and transparent (suspended matter in the sodium hypochlorite clear liquid is less than 20 mg / L). If the filter cloth is perforated, resulting in turbid sodium hypochlorite, the turbid sodium hypochlorite is returned to the sodium hypochlorite storage tank 1, the filter cloth is replaced, and the filter press is performed again.

[0033] Sodium hypochlorite with qualified clarity is stored in the storage tank 5. The solution in the storage tank 5 is sampled and analyzed, and the solution is sold out after the sodium hypochlorite and iron content are qualified.

[0034] There are two sodium hypochlorite storage tanks 1 , namely sodium hypochlorite storage tank A and sodium hypochlorite storage tank B. The bottom outlet of sodium hypochlorite storage tank A and the bottom outlet of sodium hypochlorite storage tank B are both connected to the inlet of the thick slurry tank 2 .

[0035] Use sodium hypochlorite storage tank A or B to collect the sodium hypochlorite waste liquid to be filtered, and the bottom thick slurry is input into the thick slurry tank 2.

[0036] The filter press 4 has a diaphragm pressing function and uses an antioxidant filter cloth.

[0037] Regarding filter press 4, when the filtration flow rate decreases, the filter press 4 is opened to discharge the cake and collect the dried filter cake. Furthermore, if the filter cloth becomes perforated after long-term use, the filter press 4 is similarly discharged to check for leaks. The damaged filter cloth is then replaced before resuming the filtration operation. The filter cake discharged from filter press 4 contains a large amount of titanium dioxide, which is collected and processed, stored separately, and sold out after a certain storage volume is reached.

[0038] The technical solution of the present application is further described below with reference to the accompanying drawings and embodiments.

[0039] Example

[0040] like Figure 1 As shown, Figure 1 This is a schematic diagram of a titanium dioxide sodium hypochlorite treatment device according to an embodiment of the present application.

[0041] The titanium dioxide sodium hypochlorite treatment device of this embodiment is used according to the following steps: a diaphragm filter press is selected, model: XAZGF10 / 450-UK, filter cloth: polypropylene, encrypted 108C.

[0042] S1. The sodium hypochlorite waste liquid containing titanium dichloride generated in a certain titanium dioxide chloride production line is transported to the sodium hypochlorite storage tank A and sodium hypochlorite storage tank B in the sodium hypochlorite storage tank area 1 through a pump.

[0043] S2. The sodium hypochlorite in the sodium hypochlorite tanks A and B is sent into the thick slurry tank 2 through the valve set at the bottom outlet, and then the thick slurry is transported to the filter press 4 by a pneumatic pump. The dust of the pneumatic pump is set to more than 50m and the pressure is 0.8Mpa to perform the filter press operation.

[0044] S3. The waste liquid slurry is fed to the filter press 4. At the initial stage of filtration, the outlet mirror of the filter press 4 shows that the outflowing liquid is turbid. The turbid liquid is first returned to the slurry tank 2 through the turbid liquid outlet 6 for recovery. After the outflowing liquid in the mirror becomes clear, the liquid outlet of the filter press 4 is switched to the clear liquid tank 3 through the valve to continue filtration.

[0045] S4. After the liquid level in the clear liquid tank 3 reaches 80%, sampling and analysis are performed. When the suspended solids in the clear sodium hypochlorite liquid are less than 20 mg / L, the clarified sodium hypochlorite is transferred to the storage tank 5. If the filter cloth is perforated, the suspended solids in the storage tank 5 will exceed the standard. In this case, the turbid sodium hypochlorite is recovered to the sodium hypochlorite tank A or sodium hypochlorite tank B for further filtration. If the filter cloth is perforated, the filter press 4 is unloaded to check for leaks. The damaged filter cloth is then replaced before resuming filtration.

[0046] S5. The qualified sodium hypochlorite clarified liquid after filter pressing is stored in storage tank 5, and the sodium hypochlorite and iron elements are sampled and analyzed. After the content is qualified, it is sold out.

[0047] S6. The filter cake unloaded from the filter press 4 during the filtration process is collected and processed, stored separately, and sold out after reaching a certain storage volume.

[0048] In this experiment, sodium hypochlorite waste liquid from a total of four production lines was extracted and treated using the above process flow, and the solid content in the sodium hypochlorite waste liquid before and after treatment was tested respectively. The specific test results are shown in Table 1, which shows the solid content in sodium hypochlorite waste liquid of titanium dioxide chloride at different treatment stages.

[0049] Table 1 Solid content of titanium dioxide sodium hypochlorite wastewater at different treatment stages

[0050]

[0051] It can be seen from Table 1 that after being treated by the treatment device of the present invention, the solid content in the titanium dioxide chloride is extremely low, and it is clear and transparent when observed with the naked eye, and is suitable for sale.

[0052] The embodiments described above are part of the embodiments of the present application, rather than all of the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

Claims

1. A sodium hypochlorite waste liquid treatment device for a chloride process titanium dioxide oxidation process, comprising a sodium hypochlorite storage tank (1), a concentrated slurry tank (2), a filtering device, and a clear liquid tank (3), wherein the bottom outlet of the sodium hypochlorite storage tank (1) is connected to the inlet of the concentrated slurry tank (2), and the outlet of the filtering device is connected to the inlet of the clear liquid tank (3), characterized in that: The filtering equipment is a filter press (4); an outlet is provided at the bottom of the concentrated slurry tank (2) and is connected to an inlet of the filter press (4); and the clear liquid tank (3) is used to store qualified filtrate filtered out by the filter press (4).

2. The sodium hypochlorite waste liquid treatment device for the chloride process titanium dioxide oxidation process according to claim 1, characterized in that: The filter press (4) is provided with a turbid liquid outlet (6), which is connected to the inlet of the thick slurry tank (2). The filter press (4) is provided with a sight glass for observing the turbidity of the filtrate of the filter press (4).

3. The sodium hypochlorite waste liquid treatment device for the chloride process titanium dioxide oxidation process according to claim 2, characterized in that: The clear liquid tank (3) is provided with two outlets, which are respectively connected to the inlet of the storage tank (5) and the inlet of the sodium hypochlorite storage tank (1); the storage tank (5) is used to store the qualified sodium hypochlorite solution in the clear liquid tank (3).

4. The sodium hypochlorite waste liquid treatment device for the chloride process titanium dioxide oxidation process according to claim 1, characterized in that: The clear liquid tank (3) is provided with two outlets, which are respectively connected to the inlet of the storage tank (5) and the inlet of the sodium hypochlorite storage tank (1); the storage tank (5) is used to store the qualified sodium hypochlorite solution in the clear liquid tank (3).

5. The sodium hypochlorite waste liquid treatment device for the titanium dioxide oxidation process by the chloride process according to any one of claims 1 to 4, characterized in that: There are two sodium hypochlorite storage tanks (1), namely sodium hypochlorite storage tank A and sodium hypochlorite storage tank B. The bottom outlet of sodium hypochlorite storage tank A and the bottom outlet of sodium hypochlorite storage tank B are both connected to the inlet of the thick slurry tank.

6. The sodium hypochlorite waste liquid treatment device for the titanium dioxide oxidation process by the chloride process according to any one of claims 1 to 4, characterized in that: The filter press (4) has a diaphragm pressing function and uses an antioxidant filter cloth.

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