Method and device for treating tail gas in acidolysis process of titanium dioxide

Abstract

The invention discloses a method and a device for treating tail gas in a titanium dioxide acidolysis process, relates to the technical field of tail gas treatment in titanium dioxide production, and solves the technical problem of high dust content of tail gas caused by the fact that actual tail gas treatment cannot meet the emission standard in the existing titanium dioxide calcination process. The tail gas generated after acidolysis reaction is subjected to primary water spraying, so that dust and sulfur dioxide pollutants in the tail gas are preliminarily removed; the pH value of the production wastewater is adjusted to be neutral through an alkaline substance, reclaimed water is obtained after primary clarification and secondary clarification, the reclaimed water is subjected to gas blowing, and then secondary water spraying is conducted on the tail gas obtained after spraying treatment, so that sulfur dioxide and dust in the tail gas are further removed; and the sprayed tail gas is sequentially pumped for primary electric demisting and secondary electric demisting, so that acid mist in the tail gas is removed. The method has the advantages that the production cost is reduced, the tail gas emission index is ensured to reach the standard, the consumption of water resources is reduced, the cost is reduced, the efficiency is improved, and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of tail gas treatment in titanium dioxide production, and specifically relates to a method and a device for treating tail gas in the process of titanium dioxide acid decomposition. Background Art

[0002] Titanium dioxide (also known as titanium dioxide) has stable chemical properties and does not react with most substances under normal circumstances. In nature, titanium dioxide has three types of crystals: brookite, anatase and rutile. The brookite type is an unstable crystal form with no industrial utilization value. The anatase type (Anatase) is referred to as type A, and the rutile type (Rutile) is referred to as type R. Both have stable lattices and are important white pigments and porcelain glazes. Compared with other white pigments, they have superior whiteness, tinting power, hiding power, weather resistance, heat resistance, and chemical stability, especially non-toxicity. Titanium dioxide is widely used in coatings, plastics, rubber, ink, paper, chemical fiber, ceramics, daily chemicals, medicine, food and other industries.

[0003] There are two methods for manufacturing titanium dioxide: sulfuric acid process and chlorination process. 56% of them are chlorination products, and more than 70% of these products are produced by large titanium dioxide manufacturers such as DuPont in the United States. Titanium dioxide factories in other countries, including China, still mainly use sulfuric acid process. The sulfuric acid process is to produce titanium dioxide sulfate by acid hydrolysis of ferrotitanium powder and concentrated sulfuric acid, and then generate metatitanic acid through hydrolysis, and then obtain titanium dioxide products through calcination and crushing. This method can produce anatase and rutile titanium dioxide. The advantages of the sulfuric acid process are that it can use cheap and easily available ilmenite and sulfuric acid as raw materials, the technology is relatively mature, the equipment is simple, and anti-corrosion materials are easy to solve. Its disadvantages are that the process is long, it can only be mainly operated intermittently, wet operation, high consumption of sulfuric acid and water, a lot of waste and by-products, and great pollution to the environment. The chlorination method uses titanium-containing raw materials to react high-titanium chloride slag, artificial rutile, or natural rutile with chlorine to generate titanium tetrachloride, which is purified by distillation and then oxidized in gas phase; after rapid cooling, TiO2 is obtained by gas-solid separation. The TiO2 absorbs a certain amount of chlorine, which needs to be removed by heating or steam treatment. The process is simple, but there are many chemical engineering problems such as high corrosion of chlorine, chlorine oxide, and titanium tetrachloride that need to be solved when chlorinating at 1000°C or higher. In addition, the raw materials used are special, so the cost is higher than that of the sulfuric acid method.

[0004] In the acid hydrolysis reaction, titanium concentrate reacts with high-concentration sulfuric acid at high temperature to generate titanium sulfate and titanyl sulfate. In this process, other substances in the titanium concentrate will also react with sulfuric acid to generate a large amount of sulfur dioxide, hydrogen sulfide, sulfur dust and other pollutants that pollute the atmosphere. In order to prevent these pollutants from entering the atmosphere and polluting the environment, it is necessary to treat the tail gas generated during the acid hydrolysis process. The conventional treatment method is to spray with sand-filtered water, which consumes a lot of water resources in the process. Summary of the invention

[0005] The invention discloses a method and device for treating tail gas during the acidolysis of titanium dioxide, and is intended to solve the technical problem that a large amount of sulfur dioxide, hydrogen sulfide, sulfur dust and other pollutants that pollute the atmosphere are generated during the acidolysis reaction in the production of titanium dioxide, so the tail gas generated during the acidolysis process needs to be treated, and a large amount of water resources are consumed during the sand-filtered water spraying process.

[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 treating tail gas during the acid decomposition of titanium dioxide comprises the following steps:

[0008] S1: Stirring and mixing the crushed titanium concentrate with the acid solution, and the evenly mixed mixture undergoes an acid hydrolysis reaction;

[0009] S2: spray the tail gas produced after the acid hydrolysis reaction with water to preliminarily remove dust and sulfur dioxide pollutants in the tail gas;

[0010] S3: The pH of the production wastewater is adjusted to neutral by alkaline substances, and after the neutral water is precipitated, it enters the primary clarifier. Through gravity sedimentation, the upper clear liquid in the primary clarifier overflows to the secondary clarifier, and the overflow clear liquid in the secondary clarifier is used as reclaimed water;

[0011] S4: The reclaimed water obtained in S3 is used to spray the tail gas after the spraying treatment in S2 for a second time after blowing gas, so as to further remove sulfur dioxide and dust in the tail gas;

[0012] S5: The exhaust gas after S4 spraying is pumped for primary and secondary electrostatic demisting in sequence to remove the acid mist in the exhaust gas.

[0013] The present invention takes into account that during the acid hydrolysis reaction of titanium concentrate, other impurities in the titanium concentrate will also react with sulfuric acid to generate a large amount of sulfur dioxide, hydrogen sulfide and particulate sulfur. If the above acid hydrolysis tail gas is directly discharged into the atmosphere, it will cause serious environmental pollution. Therefore, it needs to be purified. The conventional purification method is to use water spray, but it will consume a lot of water resources, affecting the cost.

[0014] The present invention is based on the consideration of reducing water resource consumption, achieving the goal of reducing costs and increasing efficiency, and ensuring that the exhaust gas emission index meets the standard. The technical method adopted by the present invention is as follows: titanium concentrate and acidic solution are stirred and mixed, and the mixture after being evenly mixed undergoes a subsequent acid hydrolysis reaction. The exhaust gas generated during the acid hydrolysis process contains a large amount of sulfur dioxide, hydrogen sulfide and particulate sulfur. The exhaust gas passes through a flue and undergoes a spray tower to preliminarily remove dust and sulfur dioxide pollutants in the exhaust gas. After the first spraying, a second spraying is performed. The second spraying adopts reclaimed water spraying. The reclaimed water is obtained by the production wastewater being subjected to gravity sedimentation after pH adjustment, and the upper clear liquid overflows. In addition, due to the gas being blown during the spraying, more gas can be absorbed in the reclaimed water. When the exhaust gas is sprayed for the second time, the internal air pressure is increased, so that it is convenient to quickly enter the subsequent electric demisting treatment. The exhaust gas after spraying is pumped by the exhaust fan for electric demisting. In the process of electric demisting, the exhaust gas concentration is reduced due to the increase of air, so the demisting efficiency will be further improved.

[0015] The present invention preferably provides a method for treating tail gas during the acidolysis of titanium dioxide, wherein the acid solution is concentrated sulfuric acid, and the concentration of the concentrated sulfuric acid is 85%-98%.

[0016] Sulfuric acid can completely degrade most of the minerals in titanium concentrate, thereby obtaining the required titanium dioxide raw materials. Since the sulfuric acid method for producing titanium dioxide has a long history, its production method is relatively mature, and the equipment used is simple and has strong replicability. At the same time, due to the improvement of many technologies, it has also achieved good results in product production. By using 85%-98% sulfuric acid, the amount of sulfuric acid can be reduced, the reaction is the fastest, the heating time can be reduced, the production cycle can be shortened, the equipment utilization rate and output can be improved, and fuel can be saved. Not only is the acidolysis rate high, but the solution F value is also relatively low, which is conducive to the subsequent hydrolysis.

[0017] The present invention preferably provides a method for treating tail gas during the acidolysis of titanium dioxide, wherein the acidolysis reaction temperature in S1 is 150°C-250°C.

[0018] With this technical solution, the reaction temperature is the main factor affecting the acid hydrolysis process of titanium concentrate. When the reaction temperature is controlled at 150°C-250°C, the acid hydrolysis reaction rate of titanium concentrate can be increased, and the heat treatment and utilization of the tail gas temperature can be achieved.

[0019] The present invention preferably provides a method for treating tail gas during the acid hydrolysis of titanium dioxide, wherein the alkaline substance is calcium carbonate.

[0020] By adopting this technical solution, calcium carbonate is used as an alkaline substance to adjust the pH, and it can also react with production wastewater to generate calcium sulfate precipitation, so that sulfate ions in the production wastewater are precipitated, and the production wastewater is further desulfurized, which can facilitate the control of the pH of the wastewater treatment while saving the cost of tail gas treatment.

[0021] The present invention preferably provides a method for treating tail gas during the acid decomposition of titanium dioxide, wherein the flow rate of the water spray in S4 is controlled to be 40 to 110 m 3 / h.

[0022] By adopting this technical solution, the amount of reclaimed water sprayed can be controlled to fully improve the exhaust gas treatment effect, ensure that the exhaust gas emissions meet national environmental protection standards, and enable it to be subsequently converted into low-grade water through primary slag slurry and reused in acid hydrolysis without affecting the sedimentation effect due to impurity ions therein.

[0023] The present invention preferably provides a method for treating tail gas during the acid decomposition of titanium dioxide, wherein the gas flow rate of the blown gas in S4 is 30m 3 / h.

[0024] After adopting this technical solution, the gas is blown through the medium water, and the medium water can accommodate more gas. When the medium water mixed with gas enters the secondary spray tower, firstly, the contact area between the medium water and the tail gas can be increased, so that the water-soluble impurities in the tail gas can be quickly dissolved in the medium water, and the water-soluble impurities can be removed; secondly, the setting of the medium water blowing gas can reduce the volume of the internal space when entering the secondary spray tower, thereby increasing the internal pressure of the secondary spray tower, and squeezing the tail gas that has been removed of water-soluble impurities into the primary electric demisting device faster; in addition, there are a large number of solid impurities in the tail gas, which are easily adsorbed in the secondary spray tower, causing the transportation channel to be blocked, and the setting of blowing gas in the medium water can clean the inside of the secondary spray tower through gas, reducing the blockage problem caused by the large amount of fixed matter in the tail gas. Therefore, the setting of medium water blowing gas can improve the processing speed and efficiency of tail gas.

[0025] A device for treating tail gas during the acidolysis of titanium dioxide comprises a premixing tank, an acidolysis tank, a primary spray tower, a secondary spray tower, a primary electric demister and a secondary electric demister connected in sequence, wherein the acidolysis tank, the primary spray tower, the secondary spray tower, the primary electric demister and the secondary electric demister are connected via a flue, and further comprises a regulating tank, a primary clarifier, a secondary clarifier and a reclaimed water aeration chamber connected in sequence, wherein one end of the reclaimed water aeration chamber is connected to the secondary clarifier, and the other end of the reclaimed water aeration chamber is connected to the secondary spray tower, and the air inlets of the primary electric demister and the secondary electric demister are both provided with tail gas fans.

[0026] By adopting this technical solution, titanium concentrate and acid solution are introduced into a premixing tank for stirring and mixing, and the evenly mixed mixture enters the acidolysis tank for acidolysis reaction. The tail gas generated during the acidolysis process enters the primary spray tower, the secondary spray tower, the primary electrostatic demister and the secondary electrostatic demister in sequence through the flue, and the original spray sand filtered water is replaced with the deeply treated reclaimed water. When the tail gas is sprayed for the second time, the supernatant overflowing from the secondary clarification tank is aerated through the reclaimed water aeration chamber to increase the internal air pressure of the secondary spray tower, so as to facilitate the rapid entry into the subsequent electrostatic demister treatment. The tail gas after spraying is pumped by the tail gas fan for electrostatic demister. In the process of electrostatic demister, the tail gas concentration is reduced due to the increase of air, thereby further improving the demisting efficiency. The primary spray tower and the secondary spray tower are both used to remove dust and sulfide in the tail gas, and the tail gas can be cooled to further improve the demisting effect of the primary electrostatic demister and the secondary electrostatic demister.

[0027] The present invention preferably provides a device for treating tail gas during the acidolysis of titanium dioxide, wherein the secondary spray tower is configured as a closed structure.

[0028] By adopting this technical solution, after the exhaust gas enters the secondary spray tower from the primary spray tower, the volume of the internal space is continuously reduced during the process of spraying the exhaust gas with the recycled water, thereby increasing the internal pressure of the secondary spray tower. The internal gas can only accelerate the flue gas through the exhaust port to the subsequent primary electric precipitator, thereby speeding up the exhaust gas treatment efficiency. At the same time, more gas can enter the subsequent primary electric precipitator together, thereby diluting the concentration of the exhaust gas entering the primary electric precipitator and improving the electric precipitator efficiency.

[0029] The present invention preferably provides a device for treating tail gas during the acidolysis of titanium dioxide, wherein a one-way control valve is provided between the primary spray tower and the secondary spray tower.

[0030] By adopting this technical solution, since water is introduced into the secondary spray tower while being blown during the spraying process, more air will also enter the secondary spray tower. The one-way control valve prevents the increase of internal air pressure from affecting the air intake. The internal air pressure can only accelerate the flue gas to be transported to the first-level electrostatic precipitator through the exhaust port, and since the internal pressure increases and enters the electrostatic precipitator, the efficiency of the electrostatic precipitator will be improved.

[0031] The present invention preferably provides a device for treating tail gas during the acidolysis of titanium dioxide, wherein a reclaimed water spray delivery pump is further provided between the secondary spray tower and the reclaimed water blast chamber.

[0032] By adopting this technical solution, the clarity of the reclaimed water after deep treatment meets the standard, and the water quality reaches the fourth-level surface water standard. In order to reduce water resource consumption and achieve the goal of reducing costs and increasing efficiency, reclaimed water can be used instead of the original acid solution spray sand filter water to treat the tail gas and save water resources. The reclaimed water spray delivery pump can not only transport the reclaimed water to the secondary spray tower, but also adjust the spraying amount of the reclaimed water, which can fully improve the treatment effect of the tail gas and ensure that the tail gas emissions meet the national environmental protection standards.

[0033] The present invention preferably provides a device for processing tail gas during the acidolysis of titanium dioxide, wherein a distributed control system is provided on the acidolysis tank, and the tail gas fan and the reclaimed water spray delivery pump are both electrically connected to the distributed control system.

[0034] By adopting this technical solution, when the thermometer in the acid hydrolysis tank rises to 75°C, the distributed control system automatically starts the exhaust gas fan and the reclaimed water spray delivery pump. Through the distributed control system, the automated control of exhaust gas treatment in the titanium dioxide production process can be realized, saving manpower and material resources, realizing the intelligence of the production process, and facilitating operation and control.

[0035] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0036] 1. The reclaimed water is obtained by adjusting the pH of the production wastewater and subjecting it to gravity sedimentation, and the supernatant overflows. During the spraying, the gas is blown, so that the reclaimed water can absorb more gas. When the tail gas is sprayed for the second time, the internal air pressure is increased, which is convenient for rapid entry into the subsequent electric demisting treatment. The tail gas after spraying is pumped by the tail gas fan for electric demisting. During the electric demisting process, the tail gas concentration is reduced due to the increase of air, which will further improve the demisting efficiency;

[0037] 2. The concentration of concentrated sulfuric acid is 85%-98%. Sulfuric acid in this concentration range can reduce the amount of sulfuric acid used, has the fastest reaction, can reduce the heating time, shorten the production cycle, improve equipment utilization and output, save fuel, not only has a high acid hydrolysis rate, but also a relatively low solution F value, which is conducive to the subsequent hydrolysis;

[0038] 3. When the thermometer in the acid hydrolysis pot rises to 75°C, the distributed control system automatically starts the tail gas fan and the reclaimed water spray delivery pump. The distributed control system can realize the automatic control of tail gas treatment in the titanium dioxide production process, save manpower and material resources, realize the intelligence of the production process, and facilitate operation and control;

[0039] 4. Control the flow rate of reclaimed water to 40~110m 3 / h, the blowing gas flow rate is 30m 3 / h, by controlling the amount of recycled water spraying, the exhaust gas treatment effect and speed can be fully improved to ensure that the exhaust gas emissions meet national environmental protection standards. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 The figure is a flow chart of tail gas treatment of the present invention. DETAILED DESCRIPTION

[0041] 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.

[0042] 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 are the positions or positional relationships that are usually placed when the invention is used. 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 operate 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.

[0043] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0044] The tail gas produced in the process of producing titanium dioxide by sulfuric acid method needs to be treated by two sand filtrations with a total flow rate of 90m 3 / h flow rate to treat the tail gas, the sand filter water consumption is high and the cost is high. The main purpose of this application is to use reclaimed water instead of sand filter water to spray the tail gas generated in the sulfuric acid process of titanium dioxide production to reduce the consumption of sand filter water. The concentration of sulfur dioxide and sulfuric acid mist in the treated tail gas should meet the national standard, that is, the concentration of sulfur dioxide ≤550mg / m 3 , the concentration of sulfuric acid mist ≤45mg / m 3 In order to further increase the speed of the tail gas spraying treatment with the reclaimed water, the present application also blows gas into the reclaimed water to increase the contact speed and contact area between the reclaimed water and the tail gas, thereby achieving the purpose of improving the tail gas treatment efficiency.

[0045] Example 1

[0046] A method for treating tail gas during the acid decomposition of titanium dioxide comprises the following steps:

[0047] S1: Stirring and mixing the crushed titanium concentrate with the acid solution, and the evenly mixed mixture undergoes an acid hydrolysis reaction;

[0048] S2: spray the tail gas produced after the acid hydrolysis reaction with water to preliminarily remove dust and sulfur dioxide pollutants in the tail gas;

[0049] S3: The pH of the production wastewater is adjusted to neutral by alkaline substances, and after the neutral water is precipitated, it enters the primary clarifier. Through gravity sedimentation, the upper clear liquid in the primary clarifier overflows to the secondary clarifier, and the overflow clear liquid in the secondary clarifier is used as reclaimed water;

[0050] S4: The reclaimed water obtained in S3 is used to spray the tail gas after the spraying treatment in S2 for a second time after blowing gas, so as to further remove sulfur dioxide and dust in the tail gas;

[0051] S5: The exhaust gas after S4 spraying is pumped for primary and secondary electrostatic demisting in sequence to remove the acid mist in the exhaust gas.

[0052] The present invention takes into account that during the acid hydrolysis reaction of titanium concentrate, other impurities in the titanium concentrate will also react with sulfuric acid to generate a large amount of sulfur dioxide, hydrogen sulfide and particulate sulfur. If the above acid hydrolysis tail gas is directly discharged into the atmosphere, it will cause serious environmental pollution. Therefore, it needs to be purified. The conventional purification method is to use water spray, but it will consume a lot of water resources, affecting the cost.

[0053] The present invention is based on the consideration of reducing water resource consumption, achieving the goal of reducing costs and increasing efficiency, and ensuring that the exhaust gas emission index meets the standard. The technical method adopted by the present invention is as follows: titanium concentrate and acidic solution are stirred and mixed, and the mixture after being evenly mixed undergoes a subsequent acid hydrolysis reaction. The exhaust gas generated during the acid hydrolysis process contains a large amount of sulfur dioxide, hydrogen sulfide and particulate sulfur. The exhaust gas passes through a flue and undergoes a spray tower to preliminarily remove dust and sulfur dioxide pollutants in the exhaust gas. After the first spraying, a second spraying is performed. The second spraying adopts reclaimed water spraying. The reclaimed water is obtained by the production wastewater being subjected to gravity sedimentation after pH adjustment, and the upper clear liquid overflows. In addition, due to the gas being blown during the spraying, more gas can be absorbed in the reclaimed water. When the exhaust gas is sprayed for the second time, the internal air pressure is increased, so that it is convenient to quickly enter the subsequent electric demisting treatment. The exhaust gas after spraying is pumped by the exhaust fan for electric demisting. In the process of electric demisting, the exhaust gas concentration is reduced due to the increase of air, so the demisting efficiency will be further improved.

[0054] In this embodiment, the primary spray water is sand-filtered water, and the flow rate of the sand-filtered water used for the primary spray is 40m 3 / h.

[0055] The acid solution is concentrated sulfuric acid, and the concentration of the concentrated sulfuric acid is 85%-98%.

[0056] Sulfuric acid can completely degrade most of the minerals in titanium concentrate, thereby obtaining the required titanium dioxide raw materials. Since the sulfuric acid method for producing titanium dioxide has a long history, its production method is relatively mature, and the equipment used is simple and has strong replicability. At the same time, due to the improvement of many technologies, it has also achieved good results in product production. By using 85%-98% sulfuric acid, the amount of sulfuric acid can be reduced, the reaction is the fastest, the heating time can be reduced, the production cycle can be shortened, the equipment utilization rate and output can be improved, and fuel can be saved. Not only is the acidolysis rate high, but the solution F value is also relatively low, which is conducive to the subsequent hydrolysis.

[0057] The acid hydrolysis reaction temperature in S1 is 150°C-250°C.

[0058] Reaction temperature is the main factor affecting the acid hydrolysis process of titanium concentrate. When the reaction temperature is controlled at 150℃-250℃, the acid hydrolysis reaction rate of titanium concentrate can be increased, and the heat treatment and utilization of the tail gas temperature can be achieved.

[0059] The alkaline substance is calcium carbonate.

[0060] Calcium carbonate is used as an alkaline substance to adjust the pH. It can also react with production wastewater to form calcium sulfate precipitate, so that sulfate ions in the production wastewater form precipitation, and further desulfurize the production wastewater. This can facilitate the control of the pH of the wastewater treatment while saving the cost of tail gas treatment.

[0061] In this embodiment, the gas flow rate in S4 is 30m 3 / h.

[0062] The gas in this embodiment will not react with the components in the tail gas. The gas is blown through the medium water, and the medium water can accommodate more gas. When the medium water mixed with gas enters the secondary spray tower, firstly, the contact area between the medium water and the tail gas can be increased, so that the water-soluble impurities in the tail gas can be quickly dissolved in the medium water, and the water-soluble impurities can be removed; secondly, the setting of the medium water blowing gas can reduce the volume of the internal space when entering the secondary spray tower, thereby increasing the internal pressure of the secondary spray tower, and squeezing the tail gas from which the water-soluble impurities have been removed into the primary electric demisting device faster; in addition, there are a large number of solid impurities in the tail gas, which are easily adsorbed in the secondary spray tower, causing the transportation channel to be blocked, and the setting of blowing gas in the medium water can clean the inside of the secondary spray tower through gas, reducing the blockage problem caused by the large amount of fixed matter in the tail gas. Therefore, the setting of medium water blowing gas can improve the processing speed and efficiency of the tail gas.

[0063] A device for treating tail gas during the acidolysis of titanium dioxide comprises a premixing tank, an acidolysis tank, a primary spray tower, a secondary spray tower, a primary electric demister and a secondary electric demister connected in sequence, wherein the acidolysis tank, the primary spray tower, the secondary spray tower, the primary electric demister and the secondary electric demister are connected via a flue, and further comprises a regulating tank, a primary clarifier, a secondary clarifier and a reclaimed water aeration chamber connected in sequence, wherein one end of the reclaimed water aeration chamber is connected to the secondary clarifier, and the other end of the reclaimed water aeration chamber is connected to the secondary spray tower, and the air inlets of the primary electric demister and the secondary electric demister are both provided with tail gas fans.

[0064] Titanium concentrate and acid solution are introduced into a premixing tank for stirring and mixing. The evenly mixed mixture enters the acidolysis tank for acidolysis reaction. The tail gas generated during the acidolysis process enters the primary spray tower, the secondary spray tower, the primary electrostatic demister and the secondary electrostatic demister in sequence through the flue. The original spray sand filtered water is replaced with the deeply treated reclaimed water. When the tail gas is sprayed for the second time, the supernatant overflowing from the secondary clarifier is aerated through the reclaimed water aeration chamber to increase the internal air pressure of the secondary spray tower, so as to facilitate the rapid entry into the subsequent electrostatic demister treatment. The tail gas after spraying is pumped by the tail gas fan for electrostatic demister. In the process of electrostatic demister, the tail gas concentration is reduced due to the increase of air, thereby further improving the demisting efficiency. The primary spray tower and the secondary spray tower are both used to remove dust and sulfide in the tail gas, and the tail gas can be cooled to further improve the demisting effect of the primary electrostatic demister and the secondary electrostatic demister.

[0065] The secondary spray tower is configured as a closed structure.

[0066] After the exhaust gas enters the secondary spray tower from the primary spray tower, the volume of the internal space is continuously reduced during the process of spraying the exhaust gas with the recycled water, thereby increasing the internal pressure of the secondary spray tower. The internal gas can only be accelerated to transport the flue gas to the subsequent primary electric precipitator through the exhaust port, thereby speeding up the exhaust gas treatment efficiency. At the same time, more gas can be brought into the subsequent primary electric precipitator to dilute the concentration of the exhaust gas entering the primary electric precipitator and improve the electric precipitator efficiency.

[0067] A one-way control valve is arranged between the primary spray tower and the secondary spray tower.

[0068] Since water is introduced into the secondary spray tower while being inflated during the spraying process, more air will also enter the secondary spray tower. The one-way control valve prevents the increase of internal air pressure from affecting the air intake. The internal air pressure can only accelerate the flue gas to be transported to the first-level electrostatic precipitator through the exhaust port, and the flue gas enters the electrostatic precipitator due to the increase of internal pressure, which will increase the efficiency of the electrostatic precipitator.

[0069] A reclaimed water spray delivery pump is also provided between the secondary spray tower and the reclaimed water blast chamber.

[0070] The clarity of the reclaimed water after deep treatment meets the standard, and the water quality meets the fourth-level surface water standard. In order to reduce water resource consumption and achieve the goal of reducing costs and increasing efficiency, reclaimed water can be used instead of the original acid solution spray sand filter water to treat the exhaust gas and save water resources. The reclaimed water spray delivery pump can not only transport the reclaimed water to the secondary spray tower, but also adjust the spraying amount of the reclaimed water, which can fully improve the exhaust gas treatment effect and ensure that the exhaust gas emissions meet national environmental protection standards.

[0071] The acid hydrolysis tank is provided with a distributed control system, and the tail gas fan and the reclaimed water spray delivery pump are both electrically connected to the distributed control system.

[0072] When the thermometer in the acid hydrolysis tank rises to 75° C., the distributed control system automatically starts the exhaust gas fan and the reclaimed water spray delivery pump. The distributed control system can realize automated control of exhaust gas treatment during titanium dioxide production, save manpower and material resources, realize intelligence in the production process, and facilitate operation and control.

[0073] The flow rate of water spray in S4 is controlled to be 40~50m 3 / h, the blowing gas flow rate is 30m 3 / h.

[0074] The secondary spraying of the reclaimed water in S4 can reduce 50m3 per hour. 3 The sand filtration water consumption is calculated based on 8,400 working hours per year. While producing 6,500 tons of products, an average of 420,000 m3 of sand filtration water can be saved each year. 3 .

[0075] In this embodiment, by controlling the amount of water spraying, the exhaust gas treatment effect can be fully improved to ensure that the exhaust gas emissions meet the national environmental protection standards. The sulfur dioxide data detected is 200-350 mg / m 3 , sulfuric acid mist concentration is 30~40mg / m 3 .

[0076] In this actual example, it takes 3 hours to process one ton of tail gas.

[0077] Example 2

[0078] This embodiment is basically the same as Embodiment 1, except that: in this embodiment, the flow rate of water spraying in S4 is controlled to be 90-110 m 3 / h.

[0079] In this embodiment, by controlling the amount of water sprayed, the tail gas treatment effect can be fully improved to ensure that the tail gas emission meets the national environmental protection standards, so that when it is subsequently converted into small-grade water through primary slag slurry and reused for acid hydrolysis, the sedimentation effect will not be affected by the impurity ions therein. The detected sulfur dioxide data is 50-150 mg / m 3 , sulfuric acid mist concentration is 20~30mg / m 3 .

[0080] In this embodiment, it takes 1.36 hours to process one ton of tail gas.

[0081] Comparative Example 1

[0082] This comparative example is a comparative example of Example 1. This comparative example is different from Example 1 in that: in this comparative example, gas blowing is not performed on the water.

[0083] In this embodiment, it takes 6 hours to process one ton of tail gas.

[0084] Comparative Example 2

[0085] This comparative example is a comparative example of Example 2. This comparative example is different from Example 2 in that: in this comparative example, the gas is not blown.

[0086] In this embodiment, it takes 2.84 hours to process one ton of tail gas.

[0087] In summary, the treated reclaimed water can replace sand filter water and reduce the consumption of sand filter water. 3 / h, the treated sulfur dioxide data is 50~350mg / m 3 , sulfuric acid mist concentration is 30~40mg / m 3The concentration of sulfur dioxide is ≤550mg / m3 and the concentration of sulfuric acid mist is ≤45mg / m3. In addition, it can reduce 50m3 per hour. 3 The sand filtration water consumption is calculated based on 8400 working hours per year, which can save an average of 420000m3 of sand filtration water per year. 3 .

[0088] Aerating the reclaimed water can increase the contact area between the reclaimed water and the exhaust gas, squeeze the treated exhaust gas in the secondary leaching device, and quickly pass the treated exhaust gas into the primary electric demisting device, thereby speeding up the exhaust gas treatment process, which is 1-2 times faster than the speed without aeration.

[0089] 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 treating tail gas during the acidolysis of titanium dioxide, characterized in that: The steps include: S1: Stirring and mixing the crushed titanium concentrate with the acid solution, and the evenly mixed mixture undergoes an acid hydrolysis reaction; S2: spray the tail gas produced after the acid hydrolysis reaction with water to preliminarily remove dust and sulfur dioxide pollutants in the tail gas; S3: The pH of the production wastewater is adjusted to neutral by alkaline substances, and after the neutral water is precipitated, it enters the primary clarifier. Through gravity sedimentation, the upper clear liquid in the primary clarifier overflows to the secondary clarifier, and the overflow clear liquid in the secondary clarifier is used as reclaimed water; S4: The reclaimed water obtained in S3 is used to spray the tail gas after the spraying treatment in S2 for a second time after blowing gas, so as to further remove sulfur dioxide and dust in the tail gas; S5: The exhaust gas after S4 spraying is pumped for primary and secondary electrostatic demisting in sequence to remove the acid mist in the exhaust gas.

2. The method for treating tail gas during the acidolysis of titanium dioxide according to claim 1, characterized in that: The acid solution is concentrated sulfuric acid, and the concentration of the concentrated sulfuric acid is 85%-98%.

3. The method for treating tail gas during the acidolysis of titanium dioxide according to claim 1, characterized in that: The acid hydrolysis reaction temperature in S1 is 150°C-250°C.

4. The method for treating tail gas during the acidolysis of titanium dioxide according to claim 1, characterized in that: The alkaline substance is calcium carbonate.

5. The method for treating tail gas during the acidolysis of titanium dioxide according to claim 1, characterized in that: The flow rate of water spray in S4 is controlled to be 40~110m 3 / h, the blowing gas flow rate is 30m 3 / h.

6. A device for implementing the method for treating tail gas during the acidolysis of titanium dioxide according to any one of claims 1 to 5, characterized in that: The invention comprises a premixing tank, an acidolysis tank, a primary spray tower, a secondary spray tower, a primary electric demister and a secondary electric demister which are connected in sequence, wherein the acidolysis tank, the primary spray tower, the secondary spray tower, the primary electric demister and the secondary electric demister are connected via a flue, and further comprises an adjusting tank, a primary clarifier, a secondary clarifier and a reclaimed water aeration chamber which are connected in sequence, wherein one end of the reclaimed water aeration chamber is connected to the secondary clarifier, and the other end of the reclaimed water aeration chamber is connected to the secondary spray tower, and exhaust fans are provided at the air inlets of the primary electric demister and the secondary electric demister.

7. The device for treating tail gas during the acidolysis of titanium dioxide according to claim 6, characterized in that: The secondary spray tower is configured as a closed structure.

8. The device for treating tail gas during the acidolysis of titanium dioxide according to claim 6, characterized in that: A one-way control valve is arranged between the intermediate water blast chamber and the secondary spray tower.

9. The device for treating tail gas during the acidolysis of titanium dioxide according to claim 8, characterized in that: A reclaimed water spray delivery pump is also provided between the secondary spray tower and the reclaimed water blast chamber.

10. The device for treating tail gas during the acidolysis of titanium dioxide according to claim 9, characterized in that: The acid hydrolysis tank is provided with a distributed control system, and the tail gas fan and the reclaimed water spray delivery pump are both electrically connected to the distributed control system.

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