Method and system for removing ferrous ions in titanium dioxide solution

Abstract

The invention discloses a method and a system for removing ferrous ions in a titanium dioxide solution, relates to the technical field of titanium dioxide preparation, and solves the technical problems that water resources are wasted and the subsequent concentration cost is increased due to the fact that a titanium solution is diluted through water in an existing device. The method comprises the following steps: S1, continuous crystallization: continuously crystallizing a titanium dioxide solution to be crystallized through a vacuum crystallizing tank and a cooling crystallizing tank in sequence; S2, filtering ferrous crystals: pumping the crystallized titanium dioxide solution in S1 into a disc filtering assembly; s3, filtrate circulation: the filtrate in the step S2 is circulated into the disc filtering assembly through a circulation assembly and mixed with the titanium dioxide solution crystallized in the step S1, and the method has the advantages of being low in production cost, good in filtering effect and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of titanium dioxide preparation, and in particular relates to a method and a system for removing ferrous ions in a titanium dioxide solution. Background Art

[0002] In the traditional sulfuric acid method titanium dioxide production process, the iron element in the raw material will be dissolved and converted into ferrous sulfate, resulting in a large amount of ferrous ions in the acid hydrolysis slurry. These ferrous ions need to be removed before the subsequent titanium liquid hydrolysis stage, otherwise it will affect the quality of titanium dioxide. In order to remove ferrous ions, the solubility of ferrous sulfate often decreases sharply with decreasing temperature, and the vacuum low-temperature evaporation crystallization method is used to precipitate ferrous crystals, and then the solid-liquid separation is carried out through a disc filter to remove the ferrous sulfate. Since a large amount of water is evaporated after evaporation and crystallization, the concentration of the titanium liquid is increased and the viscosity is increased, thereby shortening the disc filtration cycle and affecting the output. Therefore, it is usually necessary to add water to dilute during solid-liquid separation. After adding water to dilute, not only water resources are wasted, but also the concentration of the titanium liquid is reduced, increasing the subsequent concentration cost.

[0003] In view of the problems existing in the existing devices, it is necessary to study a low-cost device for separating ferrous ions in titanium dioxide liquid. Summary of the invention

[0004] The present invention provides a method and system for removing ferrous ions in a titanium dioxide solution, and is intended to solve the technical problem that the existing device dilutes the titanium solution with water, which not only wastes water resources but also increases the subsequent concentration cost.

[0005] In order to solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] A method for removing ferrous ions from a titanium dioxide solution comprises the following steps:

[0007] S1. Continuous crystallization

[0008] The titanium dioxide solution to be crystallized passes through a vacuum crystallization tank and a cooling crystallization tank in sequence for continuous crystallization.

[0009] S2. Filtering ferrous crystals

[0010] The crystallized titanium dioxide solution in S1 is pumped into the disc filter assembly, and ferrous crystals and filtrate are obtained by filtering through the disc filter assembly.

[0011] S3, filtrate circulation

[0012] The filtrate in step S2 is circulated to the disc filter assembly through the circulation assembly and mixed with the titanium dioxide solution crystallized in step S1.

[0013] Preferably, step S1 further includes:

[0014] S1.1. During the crystallization process in the vacuum crystallization tank and the cooling crystallization tank, the stirring motor is started to allow the stirring blades to stir the titanium dioxide solution.

[0015] Preferably, step S3 further includes:

[0016] S3.1 controls the ratio of the filtrate to the amount of the titanium dioxide solution after crystallization in step S1 to be 0.03-0.05.

[0017] Preferably, the speed of the stirring motor in the vacuum crystallization tank in step S1.1 is 50-100 r / min;

[0018] The speed of the stirring motor in the cooling crystallization tank in step S1.1 is 100-150 r / min.

[0019] Preferably, the vacuum crystallization temperature of the vacuum crystallization tank in step S1 is 55-65°C;

[0020] The cooling crystallization temperature of the cooling crystallization tank in step S1 is 18-24°C.

[0021] Preferably, the crystallization time of the vacuum crystallization tank and the cooling crystallization tank in step S1 is 80-120 min.

[0022] A system for removing ferrous ions from a titanium dioxide solution comprises a crystallization component, a disc filter component and a circulation component.

[0023] The disc filter assembly comprises a tank body, a driving assembly and a filter disc. The filter disc is arranged in the tank body, the driving assembly is arranged on the tank body, and the driving assembly drives the filter disc to rotate.

[0024] The crystallization assembly comprises a vacuum crystallization tank and a cooling crystallization tank, and the vacuum crystallization tank, the cooling crystallization tank and the tank body are connected in sequence.

[0025] The filter disc is communicated with one end of the circulation component, and the other end of the circulation component is communicated with the tank body.

[0026] In the present invention, a large amount of ferrous crystals exist in the crystallized titanium liquid. The ferrous crystals are filtered through a filtering component, and the filtrate re-enters the tank body through a circulation component to mix with the crystallized titanium liquid, and dilute the crystallized titanium liquid to reduce the viscosity of the crystallized titanium liquid. In addition, the main components of the filtrate are titanium sulfate and titanyl sulfate, so the concentration of the crystallized titanium liquid can be kept relatively stable by diluting the crystallized titanium liquid with the filtrate. Therefore, in the present invention, the crystallized titanium liquid is diluted with the filtrate instead of water, which can effectively reduce the use cost;

[0027] In addition, in the present invention, continuous crystallization of the titanium liquid through vacuum crystallization and cooling crystallization can further increase the concentration of the titanium liquid and reduce the ferrous ions in the titanium liquid, which is helpful to obtain higher quality titanium dioxide products and ferrous crystals. The ferrous crystals can be collected for resource utilization.

[0028] Furthermore, the circulation component includes a first circulation pipe, a liquid storage tank and a second circulation pipe, the first circulation pipe and the second circulation pipe are respectively connected to the liquid storage tank, the first circulation pipe is connected to the filter plate, the second circulation pipe is connected to the trough body, and the lower part of the liquid storage tank is also connected to a liquid outlet pipe.

[0029] In the present invention, it should be noted that the crystallized titanium liquid is filtered through the disc filter assembly, the filtrate enters the liquid storage cylinder through the first circulation pipe, enters the second circulation pipe through the liquid storage cylinder, and re-enters the disc filter assembly through the second circulation pipe to realize the circulation of the filtrate, and the crystallized titanium liquid is diluted by the filtrate to reduce its viscosity, which is convenient for subsequent filtration;

[0030] In addition, a discharge valve is provided on the liquid outlet pipe, and the filtrate is allowed to enter the next process by opening the discharge valve.

[0031] Furthermore, the upper end of the vacuum crystallization tank is connected to a negative pressure pump through a pipeline, the lower part of the vacuum crystallization tank is connected to a first feed pump through a pipeline, and the first feed pump is connected to the cooling crystallization tank through a pipeline.

[0032] The cooling crystallization tank is connected to a cooler through a pipeline, a cooling pipe is arranged in the cooling crystallization tank, the inlet end of the cooling pipe is connected to the outlet end of the cooler through a pipeline, the outlet end of the cooling pipe is connected to the inlet end of the cooler through a cooling circulation pipe, the lower part of the cooling crystallization tank is connected to a second feed pump through a pipeline, and the second feed pump is connected to the tank body through a liquid inlet pipe.

[0033] In the present invention, it should be noted that the inlet end of the cooler is connected with a cooling liquid inlet pipe, the cooling circulation pipe is communicated with the cooling liquid inlet pipe, a valve is provided on the first feed pump and the cooling crystallization tank connecting pipeline, during the feeding process of the vacuum crystallization tank, the first feed pump and the valve are in a closed state, the vacuum crystallization tank and the cooling crystallization tank are both prior art, a heating device is provided inside the vacuum crystallization tank, after the titanium liquid enters the vacuum crystallization tank, the negative pressure pump is started to reduce the pressure in the tank, thereby reducing the boiling point of water, and then the titanium liquid is heated by the heating device, the water evaporates, and ferrous crystals are precipitated, and after a period of time, the first feed pump and the valve are opened to pump the titanium liquid after the primary crystallization into the cooling crystallization tank, Then close the first feed pump and valve, then start the cooler, inject coolant from the cooler inlet, cool it down through the cooler, and transport it to the cooling pipe through the pipeline. The coolant flowing out from the tail end of the cooling pipe enters the cooler through the cooling circulation pipe to realize circulation. The titanium liquid after the first crystallization is cooled through the cooling pipe, and the residual ferrous sulfate crystals are precipitated by relying on the characteristic that the solubility of ferrous sulfate drops sharply with the decrease of temperature to realize secondary crystallization. After two crystallizations, the ferrous ions in the titanium liquid are basically removed, which is helpful to obtain high-quality titanium dioxide products later. After two crystallizations, the titanium liquid enters the tank through the second feed pump for the next step of filtration.

[0034] Preferably, a stirring assembly is provided in both the vacuum crystallization tank and the cooling crystallization tank, and the stirring assembly includes a stirring motor and a stirring blade. The stirring motor is arranged at the upper end of the vacuum crystallization tank and the cooling crystallization tank, and at least one stirring blade is connected to the output shaft of the stirring motor.

[0035] In the present invention, the stirring motor is electrically connected to an external power source, and the stirring motor drives the stirring blades to stir the titanium liquid, which is beneficial to the uniform precipitation of crystals and the recovery and utilization of ferrous sulfate crystals.

[0036] Preferably, three stirring blades are provided, and the three stirring blades are respectively located at the upper part, the middle part and the lower part of the vacuum crystallization tank and the cooling crystallization tank.

[0037] In the present invention, three stirring blades are provided to stir the titanium liquid in the vacuum crystallization tank or the cooling crystallization tank more evenly, thereby obtaining ferrous sulfate crystals of higher quality.

[0038] Furthermore, the disc filter assembly also includes a filter shaft, the filter disc is connected to the filter shaft, the interior of the filter disc is connected to the interior of the filter shaft, the first circulation pipe is connected to the interior of the filter shaft, and the drive assembly drives the filter shaft to rotate.

[0039] In the present invention, the driving assembly includes a driving motor, which is arranged on the side of the trough body. Sprockets are provided on the output shaft of the driving motor and the filter shaft. A chain is meshed on the sprocket. The filter shaft is driven to rotate by a chain transmission, thereby driving the filter plate to rotate. Both ends of the filter shaft are rotatably connected to the side wall of the trough body.

[0040] Furthermore, the driving motor, the first circulation pump, the second circulation pump, the first electronic valve, the second electronic valve, the first transfer pump, the second transfer pump and the negative pressure pump are all connected to an external power supply.

[0041] In the present invention, the first circulation pump is used to accelerate filtration. When the first circulation pump is started, suction will be generated inside the filter shaft and the filter disc, thereby sucking the titanium liquid in the tank body into the filter disc, accelerating the filtration of the titanium liquid, and pumping the filtered filtrate into the liquid storage tank. The second circulation pump is used to pump the filtrate in the liquid storage tank back into the tank body through the second circulation pipe to mix with the crystallized titanium liquid; the first electronic valve and the second electronic valve are respectively used to control the ratio of the filtrate entering the tank body and the crystallized titanium liquid.

[0042] Preferably, the liquid inlet pipe is connected to a mixing cylinder, and the second circulation pipe is communicated with the mixing cylinder.

[0043] Preferably, a mixing chamber is provided in the mixing barrel, and the mixing chamber is arranged along the axial direction of the mixing barrel. A connecting portion is provided on the side wall of the mixing barrel, and a connecting hole is provided on the connecting portion. The connecting hole is arranged along the radial direction of the mixing barrel, and the connecting hole is connected to the mixing chamber through an inclined channel. The end of the second circulation pipe is connected to the connecting hole, and the liquid inlet pipe is connected to the mixing chamber.

[0044] In the present invention, the mixing cylinder is used to mix the filtered filtrate with the crystallized titanium liquid, so that the filtrate with low viscosity and the crystallized titanium liquid with high viscosity are fully mixed before entering the tank body for filtration, so that when filtering on the filter disc, the evenly mixed liquid makes the filtering effect better, and the filter residue formed on the surface of the filter disc is more uniform, preventing the excessive local filter residue of the filter disc from affecting the filtering quality;

[0045] After the filtrate in the circulation pipe enters the connecting hole, the filtrate will accelerate into the mixing chamber in the inclined channel. Due to the inclined setting of the inclined channel, the filtrate flowing into the mixing chamber through the inclined channel forms a greater impact in the mixing chamber and generates a vortex. At this time, the crystallized titanium liquid flowing in from the liquid inlet pipe collides with the filtrate in the mixing chamber to form a vortex and mix evenly, so that the viscosity of the newly crystallized viscous titanium liquid in the mixing chamber is reduced, thereby making the viscosity of the slurry discharged into the tank body more uniform, and the filtering effect is better.

[0046] Preferably, an expansion cavity is provided in the connecting hole, and two of the inclined channels are provided on a side of the expansion cavity close to the mixing cavity.

[0047] In the present invention, by setting up an expansion chamber, the difference in cross-sectional area when the expansion chamber enters the inclined channel is increased, so that the filtrate speed entering the inclined channel is further increased and the pressure is increased, thereby achieving more efficient and more uniform mixing with the titanium liquid entering the mixing chamber from the feed pipe. The setting of the two inclined channels is also to increase the mixing efficiency and quality.

[0048] Furthermore, one filter disc is formed by enclosing a plurality of sub-filter discs, and the interior of each sub-filter disc is hollow and communicated with the interior of the filter shaft.

[0049] Furthermore, a partition is provided in the tank body, the partition is provided with multiple bending parts, one side of the filter disc is placed in the bending part, a scraper is provided on the bending part, the partition divides the tank body into a filtering tank and a scraping tank, and the scraping tank has multiple discharge ports at the lower end.

[0050] In the present invention, during the process of the filter disc being driven to rotate by the driving shaft, the ferrous sulfate crystals attached to the surface of the filter disc have a certain thickness. During the continuous rotation of the turntable, since one side of the filter disc is always in the recessed part of the bent portion, the scrapers on both sides of the bent portion will continuously scrape off the ferrous sulfate crystals attached to both sides of the filter disc. The scraped ferrous sulfate crystals fall into the scraping groove and are discharged through the discharge port. A collecting device or a conveyor belt can be arranged at the lower end of the discharge port to transport the ferrous sulfate crystals.

[0051] Furthermore, the driving motor, the first water pump, the second water pump, the first electronic valve, the second electronic valve and the negative pressure pump are all connected to an external power supply.

[0052] Furthermore, a liquid inlet is provided at the upper end of the vacuum crystallization tank, and an air outlet is provided at the upper ends of the vacuum crystallization tank and the cooling crystallization tank.

[0053] In the present invention, the liquid inlet is connected to the previous process, the titanium liquid to be crystallized enters the vacuum crystallization tank from the liquid inlet, and the gas outlet is used to connect to the exhaust device.

[0054] Preferably, a support column is provided at the lower end of the trough body.

[0055] The process of the present invention:

[0056] Continuous crystallization: add the titanium dioxide solution to be crystallized into the vacuum crystallization tank through the liquid inlet. During this process, keep the valve and the first feed pump closed. After adding the titanium liquid, the vacuum crystallization tank will start to heat the titanium liquid, and then start the negative pressure pump to create a vacuum environment in the vacuum crystallization tank. The solvent evaporates and ferrous sulfate crystals are precipitated. After a period of time, turn off the negative pressure pump, open the first feed pump and the valve, turn off the second feed pump, and let the titanium liquid and crystal mixed solution of the first crystallization enter the cooling crystallization tank. Then turn off the first feed pump and the valve. Under the action of the cooler, the temperature of the coolant is reduced, and the temperature in the cooling crystallization tube is reduced through the cooling circulation pipe. The titanium liquid is crystallized for the second time to achieve continuous crystallization. During the cooling crystallization process of a batch of titanium liquid, the next batch of liquid can be added through the liquid inlet.

[0057] Filtering ferrous crystals: control the second electronic valve to open, pump the crystallized titanium dioxide solution into the mixing cylinder through the second feed pump, and then enter the filter tank through the mixing cylinder. The filter shaft is driven by the drive assembly, i.e., the drive motor, thereby driving the filter disc to rotate. The first circulation pump generates suction on the filter disc, and the ferrous ion crystals are adsorbed on the surface of the filter disc. The filtrate enters the filter disc and enters the first circulation pipe through the inside of the filter shaft. As the filter disc rotates, the filter disc and the scraper cooperate to scrape off the attached ferrous sulfate crystals and discharge them through the discharge port.

[0058] Filtrate circulation: The filtrate enters the liquid storage tank through the first circulation pump, controls the first electronic valve to open, and pumps the filtrate in the liquid storage tank into the mixing drum through the second circulation pump. The filtrate and the titanium dioxide solution pumped out of the cooling tank are mixed and diluted in the mixing drum, and then re-enters the filter tank. In this process, the first electronic valve and the second electronic valve control the ratio of the circulating filtrate entering the mixing drum to the titanium dioxide solution pumped out of the cooling tank to be 0.03-0.05.

[0059] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0060] 1. The present invention provides a system for removing ferrous ions from a titanium dioxide solution. By setting a circulation component, the filtrate enters a liquid storage tank from a first circulation pipe, and then returns to the interior of the tank through a second circulation pipe to mix with the titanium liquid after crystallization. The viscosity of the titanium liquid is reduced while avoiding a decrease in the concentration of titanium, thereby preventing the viscosity of the titanium liquid from affecting the filtration quality and reducing the production cost.

[0061] 2. The present invention provides a system for removing ferrous ions from titanium dioxide solution, which continuously crystallizes the titanium liquid through vacuum crystallization and cooling crystallization, thereby further increasing the concentration of the titanium liquid and reducing the ferrous ions in the titanium liquid, thereby helping to obtain higher quality titanium dioxide products and ferrous crystals. The ferrous crystals can be collected for resource utilization.

[0062] 3. The present invention provides a system for removing ferrous ions in titanium dioxide solution. A mixing cylinder is provided, and the mixing cylinder is used to mix the filtered filtrate with the crystallized titanium liquid, so that the filtrate with low viscosity and the crystallized titanium liquid with high viscosity formed due to the increase in the concentration of the titanium liquid are fully mixed before entering the tank body for filtration. When filtering on the filter disc, the evenly mixed liquid makes the filtration effect better, and the filter residue formed on the surface of the filter disc is more uniform, preventing excessive local filter residue from affecting the filtration quality.

[0063] 4. The system for removing ferrous ions from a titanium dioxide solution provided by the present invention is conducive to the rapid and uniform precipitation of crystals by setting a stirring component, and is conducive to the recycling of ferrous sulfate crystals. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] The present invention will now be described by way of example with reference to the accompanying drawings, in which:

[0065] Figure 1 It is the overall system diagram of the present invention;

[0066] Figure 2 This is a schematic diagram of the structure of the disc filter assembly of the present invention;

[0067] Figure 3 It is a schematic diagram of the structure of the mixing cylinder of the present invention;

[0068] Figure 4 This is a schematic diagram of the internal structure of the mixing cylinder of the present invention;

[0069] Figure 5 A schematic diagram of one embodiment of the present invention;

[0070] Figure 6 It is a schematic diagram of the tank structure of the present invention.

[0071] Reference numerals:

[0072] 1-vacuum crystallization tank, 2-cooling crystallization tank, 3-disc filter assembly, 301-tank, 4-stirring motor, 5-stirring blade, 6-liquid inlet, 7-gas outlet, 8-cooler, 9-cooling pipe, 10-first feed pump, 11-negative pressure pump, 12-second feed pump, 13-valve, 14-drive assembly, 15-filter disc, 1501-sub-filter disc, 16-circulation assembly, 1601-first circulation pipe, 1602 -liquid storage tank, 1603-second circulation pipe, 17-mixing cylinder, 1701-connecting hole, 1702-inclined channel, 1703-mixing chamber, 1704-expansion chamber, 18-first electronic valve, 19-second electronic valve, 20-first circulation pump, 21-second circulation pump, 22-cooling liquid inlet pipe, 23-cooling circulation pipe, 24-liquid inlet pipe, 25-liquid outlet pipe, 26-partition, 27-scraper, 28-discharge port. DETAILED DESCRIPTION

[0073] 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 combination with the embodiments of the present application and the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application usually described and indicated in the accompanying drawings here can be arranged and designed in various configurations. Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings 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.

[0074] In the description of the embodiments of the present application, it should be noted that the terms "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or the positions or positional relationships in which the practical product is usually placed when in use. They 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 orientation, be constructed and operated in a specific orientation, 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.

[0075] Combine the following Figure 1-Figure 6 The present invention is described in detail.

[0076] Example 1

[0077] A method for removing ferrous ions in a titanium dioxide solution, characterized in that it comprises the following steps:

[0078] S1. Continuous crystallization

[0079] The titanium dioxide solution to be crystallized passes through the vacuum crystallization tank 1 and the cooling crystallization tank 2 in sequence for continuous crystallization;

[0080] S2. Filtering ferrous crystals

[0081] The crystallized titanium dioxide solution in S1 is pumped into the disc filter assembly 3, and filtered through the disc filter assembly 3 to obtain ferrous crystals and filtrate.

[0082] S3, filtrate circulation

[0083] The filtrate in step S2 is circulated to the disc filter assembly 3 through the circulation assembly 16 and mixed with the titanium dioxide solution crystallized in step S1.

[0084] Step S1 also includes: S1.1, during the crystallization process of the vacuum crystallization tank 1 and the cooling crystallization tank 2, starting the stirring motor 4 to enable the stirring blades 5 to stir the titanium dioxide solution.

[0085] In step S1.1, the speed of the stirring motor 4 in the vacuum crystallization tank 1 is 50-100 r / min;

[0086] In step S1.1, the rotation speed of the stirring motor 4 in the cooling crystallization tank 2 is 100-150 r / min.

[0087] The crystallization time of the vacuum crystallization tank and the cooling crystallization tank in step S1 is 80-120 minutes.

[0088] Step S3 also includes:

[0089] S3.1 Control the ratio of the amount of the titanium dioxide solution after crystallization to the filtrate in step S1 to be 0.03-0.05.

[0090] The vacuum crystallization temperature of the vacuum crystallization tank in step S1 is 55-65°C;

[0091] The cooling crystallization temperature of the cooling crystallization tank in step S1 is 18-24°C

[0092] In this embodiment, the ferrous crystals are filtered through the disc filter assembly 3, and the filtrate re-enters the tank body 301 through the circulation assembly 16 to mix with the crystallized titanium liquid, dilute the crystallized titanium liquid, and reduce the viscosity of the crystallized titanium liquid. In addition, the main components of the filtrate are titanium sulfate and titanyl sulfate. Therefore, the concentration of the titanium liquid can be kept relatively stable by diluting the crystallized titanium liquid with the filtrate, thereby reducing the use of water and reducing costs.

[0093] In this embodiment, since ferrous ions are precipitated by cooling crystallization, the concentration of titanium in the titanium liquid is not directly affected. Therefore, by measuring the concentration of the titanium dioxide solution after continuous crystallization, the concentration of the titanium dioxide solution is 185-190 g / L after continuous crystallization. By measuring the concentration of the material after the filtrate and the crystallized titanium dioxide solution are mixed, the concentration of the material at this time is 163-167 g / L. Therefore, diluting the crystallized titanium dioxide solution with the filtrate does not cause a sharp decrease in the concentration of the titanium liquid, reducing the cost of subsequent concentration.

[0094] In this embodiment, continuous crystallization of the titanium liquid by vacuum crystallization and cooling crystallization can further increase the concentration of the titanium liquid and reduce the ferrous ions in the titanium liquid, which is helpful to obtain higher quality titanium dioxide products and ferrous crystals. The ferrous crystals can be collected for resource utilization;

[0095] In addition, in this embodiment, when the ratio of the amount of the circulating filtrate to the amount of the titanium dioxide solution after crystallization is 0.03, the iron-titanium ratio in the mixed titanium liquid is 0.25-0.27, and when the ratio of the amount of the circulating filtrate entering the mixing cylinder 17 to the amount of the titanium dioxide solution pumped out of the cooling tank is 0.05, the iron-titanium ratio in the mixed titanium liquid is 0.27-0.29, so that the iron-titanium ratio is in a stable state and within the specified index range for a long time, so that the product quality is stable;

[0096] It should be noted that the iron-titanium ratio refers to the ratio of the total mass of iron in the filtrate to the total mass of titanium in the filtrate, and the specified index range of the iron-titanium ratio is ≤0.33.

[0097] Example 2

[0098] The difference between this embodiment and embodiment 1 is that:

[0099] In step S1.1, the speed of the stirring motor 4 in the vacuum crystallization tank 1 is 50 r / min;

[0100] In step S1.1, the rotation speed of the stirring motor 4 in the cooling crystallization tank 2 is 100 r / min.

[0101] In this embodiment, the stirring motor 4 drives the stirring blade 5 to stir the titanium liquid, which is beneficial to the uniform precipitation of crystals, improves the crystallization efficiency, and is beneficial to the recycling of ferrous sulfate crystals;

[0102] In this embodiment, during the vacuum crystallization process, a lower stirring speed is conducive to the growth of crystals, so that the crystals can grow under relatively stable conditions, avoiding crystal breakage or uneven growth caused by overly intense stirring; and during the cooling crystallization process, a higher stirring speed is conducive to the uniform distribution of the solute in the solution. As the temperature decreases, the solubility of the solute decreases, and stirring can prevent local supersaturation from being too high, thereby avoiding spontaneous nucleation and uneven crystal size.

[0103] Example 3

[0104] The difference between this embodiment and embodiment 2 is that the ratio of the amount of the titanium dioxide solution after crystallization to the filtrate in step S1 is controlled to be 0.04 by S3.1.

[0105] In this embodiment, when the ratio of the circulating filtrate to the amount of the titanium dioxide solution after crystallization is 0.04, the iron-titanium ratio in the mixed titanium liquid is 0.27, so that the iron-titanium ratio is in a stable state and within the specified index range for a long time, so that the product quality is stable;

[0106] Example 4

[0107] A system for removing ferrous ions from a titanium dioxide solution, such as Figure 1As shown, it includes a crystallization component, a disc filter component 3 and a circulation component 16,

[0108] The disc filter assembly 3 includes a tank body 301, a driving assembly 14 and a filter disc 15. The filter disc 15 is arranged in the tank body 301. The driving assembly 14 is arranged on the tank body 301. The driving assembly 14 drives the filter disc 15 to rotate.

[0109] The crystallization assembly includes a vacuum crystallization tank 1 and a cooling crystallization tank 2, and the vacuum crystallization tank 1, the cooling crystallization tank 2 and the tank body 301 are connected in sequence.

[0110] The filter disc 15 is communicated with one end of the circulation component 16 , and the other end of the circulation component 16 is communicated with the tank body 301 .

[0111] The circulation component 16 includes a first circulation pipe 1601, a liquid storage tank 1602 and a second circulation pipe 1603. The first circulation pipe 1601 and the second circulation pipe 1603 are respectively connected to the liquid storage tank 1602. The first circulation pipe 1601 is connected to the filter plate 15, and the second circulation pipe 1603 is connected to the tank body 301. The lower part of the liquid storage tank 1602 is also connected to a liquid outlet pipe 25, and a discharge valve 13 is provided on the liquid outlet pipe 25.

[0112] The upper end of the vacuum crystallization tank 1 is connected to a negative pressure pump 11 through a pipeline, and the lower part of the vacuum crystallization tank 1 is connected to a first feed pump 10 through a pipeline, and the first feed pump 10 is connected to the cooling crystallization tank 2 through a pipeline.

[0113] The cooling crystallization tank 2 is connected to the cooler 8 through a pipeline. A cooling pipe 9 is provided in the cooling crystallization tank 2. The inlet end of the cooling pipe 9 is connected to the outlet end of the cooler 8 through a pipeline. The outlet end of the cooling pipe 9 is connected to the inlet end of the cooler 8 through a cooling circulation pipe 23. The lower part of the cooling crystallization tank 2 is connected to a second feed pump 12 through a pipeline. The second feed pump 12 is connected to the tank body 301 through a liquid inlet pipe 24.

[0114] The inlet end of the cooler 8 is connected to a cooling liquid inlet pipe 22 , and a cooling circulation pipe 23 is in communication with the cooling liquid inlet pipe 22 .

[0115] The disc filter assembly 3 also includes a filter shaft, the filter disc 15 is connected to the filter shaft, the interior of the filter disc 15 is connected to the interior of the filter shaft, the first circulation pipe 1601 is connected to the interior of the filter shaft, and the driving assembly 14 drives the filter shaft to rotate.

[0116] The first circulation pipe 1601 is provided with a first circulation pump 20 , the second circulation pipe 1603 is provided with a second circulation pump 21 and a first electronic valve 18 , and the liquid inlet pipe 24 is provided with a second electronic valve 19 .

[0117] One filter disc 15 is formed by enclosing a plurality of sub-filter discs 1501 . The sub-filter discs 1501 are hollow inside and communicated with the inside of the filter shaft.

[0118] A partition 26 is provided in the tank body 301, and the partition 26 has multiple bending parts. One side of the filter disc 15 is placed in the bending part, and a scraper 27 is provided on the bending part. The partition 26 divides the tank body 301 into a filter tank 301 and a scraping tank. Multiple discharge ports 28 are provided at the lower end of the scraping tank.

[0119] The driving motor, the first circulation pump 20, the second circulation pump 21, the first electronic valve 18, the second electronic valve 19, the first transfer pump 10, the second transfer pump 12 and the negative pressure pump 11 are all connected to an external power source.

[0120] The upper end of the vacuum crystallization tank 1 is provided with a liquid inlet 6, and the upper ends of the vacuum crystallization tank 1 and the cooling crystallization tank 2 are both provided with an air outlet 7.

[0121] A support column is disposed at the lower end of the tank body 301 .

[0122] In this embodiment, the titanium liquid is continuously crystallized by vacuum crystallization and cooling crystallization to further increase the concentration of the titanium liquid and reduce the ferrous ions in the titanium liquid;

[0123] The crystallized titanium liquid is filtered through the disc filter assembly 3, and the filtrate passes through the first circulation pipe 1601 into the liquid storage cylinder, and then enters the second circulation pipe 1603 through the liquid storage cylinder, and re-enters the disc filter assembly 3 through the second circulation pipe 1603 to realize the circulation of the filtrate. The crystallized titanium liquid is diluted by the filtrate to reduce its viscosity, which is convenient for subsequent filtration;

[0124] The first circulation pump 20 is used to accelerate filtration. When the first circulation pump 20 is started, suction will be generated inside the filter shaft and the filter disc 15, thereby sucking the titanium liquid in the tank body 301 into the filter disc 15, accelerating the filtration of the titanium liquid, and pumping the filtered filtrate into the liquid storage tank 1602. The second circulation pump 21 is used to pump the filtrate in the liquid storage tank 1602 back into the tank body 301 through the second circulation pipe 1603 to mix with the crystallized titanium liquid; the first electronic valve 18 and the second electronic valve 19 are respectively used to control the ratio of the filtrate entering the tank body 301 and the crystallized titanium liquid.

[0125] Example 5

[0126] The difference between this embodiment and embodiment 4 is that Figure 1As shown, the vacuum crystallization tank 1 and the cooling crystallization tank 2 are both provided with a stirring assembly, and the stirring assembly includes a stirring motor 4 and a stirring blade 5. The stirring motor 4 is arranged at the upper ends of the vacuum crystallization tank 1 and the cooling crystallization tank 2, and at least one stirring blade 5 is connected to the output shaft of the stirring motor 4.

[0127] There are three stirring blades 5 , and the three stirring blades 5 are respectively located at the upper part, the middle part and the lower part of the vacuum crystallization tank 1 and the cooling crystallization tank 2 .

[0128] Example 6

[0129] The difference between this embodiment and embodiment 5 is that Figure 1-Figure 5 As shown, the liquid inlet pipe 24 is connected to a mixing cylinder 17 , and the second circulation pipe 1603 is in communication with the mixing cylinder 17 .

[0130] A mixing chamber 1703 is provided in the mixing barrel 17, and the mixing chamber 1703 is arranged along the axial direction of the mixing barrel 17. A connecting portion is provided on the side wall of the mixing barrel 17, and a connecting hole 1701 is provided on the connecting portion. The connecting hole 1701 is arranged along the radial direction of the mixing barrel 17. The connecting hole 1701 is connected to the mixing chamber 1703 through an inclined channel 1702. The end of the second circulation pipe 1603 is connected to the connecting hole 1701, and the liquid inlet pipe 24 is connected to the mixing chamber 1703.

[0131] In this embodiment, the mixing cylinder 17 is used to mix the filtered filtrate with the crystallized titanium liquid, so that the filtrate with low viscosity and the crystallized titanium liquid with high viscosity are fully mixed before entering the tank body 301 for filtration. When the filter disc 15 is filtering, the evenly mixed liquid makes the filtering effect better, and the filter residue formed on the surface of the filter disc 15 is more uniform, which prevents the local filter residue of the filter disc 15 from affecting the filtering quality.

[0132] After the filtrate in the circulation pipe enters the connecting hole 1701, the filtrate will be accelerated to flow into the mixing chamber 1703 in the inclined channel 1702. Due to the inclined setting of the inclined channel 1702, the filtrate flowing into the mixing chamber 1703 through the inclined channel 1702 forms a large impact and generates a vortex in the mixing chamber 1703. At this time, the crystallized titanium liquid flowing in from the liquid inlet pipe 24 collides with the filtrate in the mixing chamber 1703 to form a vortex and mix evenly, so that the viscosity of the newly crystallized viscous titanium liquid in the mixing chamber 1703 is reduced, thereby making the viscosity of the slurry discharged into the tank body 301 more uniform, and the filtering effect is better.

[0133] Example 7

[0134] The difference between this embodiment and embodiment 6 is that Figure 5As shown, an expansion cavity is provided in the connecting hole 1701 , and two inclined channels 1702 are provided on one side of the expansion cavity close to the mixing cavity 1703 .

[0135] In this embodiment, by setting up an expansion chamber, the difference in cross-sectional area when the expansion chamber enters the inclined channel 1702 is increased, so that the filtrate speed entering the inclined channel 1702 is further increased and the pressure is increased, thereby mixing more efficiently and evenly with the titanium liquid entering the mixing chamber 1703 from the feed pipe. The two inclined channels 1702 are also set to improve the mixing efficiency and quality.

[0136] The process of the present invention:

[0137] Continuous crystallization: the titanium dioxide solution to be crystallized is added into the vacuum crystallization tank 1 through the liquid inlet 6. During this process, the valve 13 and the first feed pump 10 are kept closed. After the titanium liquid is added, the vacuum crystallization tank 1 will start to heat the titanium liquid, and then the negative pressure pump 11 is started to create a vacuum environment in the vacuum crystallization tank 1. The solvent evaporates and ferrous sulfate crystals are precipitated. After a period of time, the negative pressure pump 11 is turned off, the first feed pump 10 and the valve 13 are turned on, and the second feed pump 12 is turned off to allow the titanium liquid and the crystal mixed solution of the first crystallization to enter the cooling crystallization tank 2. Then the first feed pump 10 and the valve 13 are turned off. The temperature of the coolant is reduced under the action of the cooler 8, and the temperature in the cooling crystallization tube is reduced through the cooling circulation pipe 23. The titanium liquid is subjected to secondary crystallization to achieve continuous crystallization. During the cooling crystallization process of a batch of titanium liquid, the next batch of liquid can be added through the liquid inlet 6.

[0138] Filtering ferrous crystals: control the second electronic valve 19 to open, pump the crystallized titanium dioxide solution into the mixing drum 17 through the second feed pump 12, and enter the filter tank through the mixing drum 17. The filter shaft is driven to rotate by the driving component 14, i.e., the driving motor, thereby driving the filter disc 15 to rotate. The first circulation pump 20 causes the filter disc 15 to generate suction, and the ferrous ion crystals will be adsorbed on the surface of the filter disc 15. The filtrate enters the filter disc 15 and enters the first circulation pipe 1601 through the inside of the filter shaft; as the filter disc 15 rotates, the filter disc 15 and the scraper 27 cooperate to scrape off the attached ferrous sulfate crystals and discharge them through the discharge port 28.

[0139] Filtrate circulation: the filtrate enters the liquid storage tank 1602 through the first circulation pump 20, the first electronic valve 18 is controlled to open, and the filtrate in the liquid storage tank 1602 is pumped into the mixing drum 17 through the second circulation pump 21. The filtrate and the titanium dioxide solution pumped out of the cooling tank are mixed and diluted in the mixing drum 17, and then re-enter the filter tank. In this process, the first electronic valve 18 and the second electronic valve 19 control the ratio of the circulating filtrate entering the mixing drum 17 to the titanium dioxide solution pumped out of the cooling tank to be 0.03-0.05.

[0140] Comparative Example 1

[0141] The circulation component was removed, and the concentration of the titanium liquid after the crystallization was completed was measured, and the concentration range of the titanium liquid after the crystallization was completed was 185-190g / L;

[0142] After the crystallization was completed, the concentration of the titanium liquid after dilution and mixing with the filtrate circulated through the circulation component was measured, and the concentration range of the mixed titanium liquid was 163-167 g / L.

[0143] Based on the data of Comparative Example 1, it can be seen that circulating the filtrate through the circulation component to dilute the crystallized titanium liquid does not cause a sharp decrease in the concentration of the titanium liquid, thereby reducing the cost of subsequent concentration.

[0144] Comparative Example 2

[0145] The cooling crystallization tank was removed, and the ferrous ion content of the titanium liquid slurry flowing out of the vacuum crystallization tank was measured, so that the average iron-titanium ratio in the titanium liquid after vacuum crystallization was 0.35;

[0146] After continuous crystallization in the vacuum crystallization tank and the cooling crystallization tank, the ferrous ion content of the titanium liquid slurry flowing out of the cooling crystallization tank was measured, and the average iron-titanium ratio in the titanium liquid after continuous crystallization was obtained to be 0.27;

[0147] During the production process, the specified index range of the iron-titanium ratio is ≤0.33. Based on the data of Comparative Example 2, it can be seen that after continuous crystallization, the value of the iron-titanium ratio is controlled within 0.33. Compared with the method of vacuum crystallization alone, the average value of the iron-titanium ratio in the titanium liquid is significantly lower. Continuous crystallization helps to obtain better quality titanium dioxide in the subsequent process.

[0148] 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 removing ferrous ions from a titanium dioxide solution, characterized in that: The following steps are involved: S1. Continuous crystallization The titanium dioxide solution to be crystallized is sequentially passed through a vacuum crystallization tank (1) and a cooling crystallization tank (2) for continuous crystallization; S2. Filtering ferrous crystals The crystallized titanium dioxide solution in S1 is pumped into the disc filter assembly (3), and filtered through the disc filter assembly (3) to obtain ferrous crystals and filtrate. S3, filtrate circulation The filtrate in step S2 is circulated to the disc filter assembly (3) through the circulation assembly (16) and mixed with the titanium dioxide solution crystallized in step S1.

2. A method for removing ferrous ions in a titanium dioxide solution according to claim 1, characterized in that: Step S1 also includes: S1.

1. During the crystallization process in the vacuum crystallization tank (1) and the cooling crystallization tank (2), the stirring motor (4) is started to allow the stirring blade (5) to stir the titanium dioxide solution.

3. A method for removing ferrous ions from a titanium dioxide solution according to claim 1, characterized in that: Step S3 also includes: S3.1 controls the ratio of the filtrate to the amount of the titanium dioxide solution after crystallization in step S1 to be 0.03-0.

05.

4. A method for removing ferrous ions in a titanium dioxide solution according to claim 2, characterized in that: In step S1.1, the rotation speed of the stirring motor (4) in the vacuum crystallization tank (1) is 50-100 r / min; In step S1.1, the rotation speed of the stirring motor (4) in the cooling crystallization tank (2) is 100-150 r / min.

5. The method for removing ferrous ions from a titanium dioxide solution according to claim 1, characterized in that: The vacuum crystallization temperature of the vacuum crystallization tank (1) in step S1 is 55-65° C.; The cooling crystallization temperature of the cooling crystallization tank (2) in step S1 is 18-24°C.

6. A system for removing ferrous ions from a titanium dioxide solution, characterized in that: It comprises a crystallization component, a disc filter component (3) and a circulation component (16), The disc filter assembly (3) comprises a tank body (301), a drive assembly (14) and a filter disc (15); the filter disc (15) is arranged in the tank body (301); the drive assembly (14) is arranged on the tank body (301); the drive assembly (14) drives the filter disc (15) to rotate; The crystallization assembly comprises a vacuum crystallization tank (1) and a cooling crystallization tank (2), wherein the vacuum crystallization tank (1), the cooling crystallization tank (2) and the tank body (301) are connected in sequence. The filter disc (15) is in communication with one end of the circulation component (16), and the other end of the circulation component (16) is in communication with the tank body (301).

7. A system for removing ferrous ions from a titanium dioxide solution according to claim 6, characterized in that: The circulation component (16) comprises a first circulation pipe (1601), a liquid storage tank (1602) and a second circulation pipe (1603); the first circulation pipe (1601) and the second circulation pipe (1603) are respectively connected to the liquid storage tank (1602); the first circulation pipe (1601) is connected to the filter disc (15); the second circulation pipe (1603) is connected to the tank body (301); and the lower part of the liquid storage tank (1602) is also connected to a liquid outlet pipe (25).

8. A system for removing ferrous ions from a titanium dioxide solution according to claim 6, characterized in that: The upper end of the vacuum crystallization tank (1) is connected to a negative pressure pump (11) via a pipeline, and the lower part of the vacuum crystallization tank (1) is connected to a first feed pump (10) via a pipeline, and the first feed pump (10) is connected to the cooling crystallization tank (2) via a pipeline. The cooling crystallization tank (2) is connected to a cooler (8) via a pipeline. A cooling pipe (9) is provided inside the cooling crystallization tank (2). The inlet end of the cooling pipe (9) is connected to the outlet end of the cooler (8) via a pipeline. The outlet end of the cooling pipe (9) is connected to the inlet end of the cooler (8) via a cooling circulation pipe (23). The lower part of the cooling crystallization tank (2) is connected to a second feed pump (12) via a pipeline. The second feed pump (12) is connected to the tank body (301) via a liquid inlet pipe (24).

9. A system for removing ferrous ions from a titanium dioxide solution according to claim 6, characterized in that: The vacuum crystallization tank (1) and the cooling crystallization tank (2) are both provided with a stirring assembly, wherein the stirring assembly comprises a stirring motor (4) and a stirring blade (5), wherein the stirring motor (4) is arranged at the upper ends of the vacuum crystallization tank (1) and the cooling crystallization tank (2), and at least one stirring blade (5) is connected to the output shaft of the stirring motor (4).

10. A system for removing ferrous ions from a titanium dioxide solution according to claim 8, characterized in that: The liquid inlet pipe (24) is connected to a mixing cylinder (17), and the second circulation pipe (1603) is in communication with the mixing cylinder (17).

Images