Titanium dioxide calcination tail gas dust content ultralow emission method

Abstract

The invention discloses a titanium dioxide calcination tail gas dust content ultralow emission method, relates to the technical field of titanium dioxide production tail gas treatment, and solves the technical problem of high tail gas dust content caused by the fact that actual tail gas treatment cannot meet the emission standard in the existing titanium dioxide calcination process. The method comprises the following steps: S1, carrying out primary spraying treatment on tail gas obtained after titanium dioxide is calcined so as to preliminarily remove dust and sulfur dioxide pollutants in the tail gas; s2, the tail gas treated in the step S1 is subjected to secondary water spraying treatment so as to absorb sodium sulfite generated in the step S1; and S3, the tail gas treated in the S2 is subjected to demisting treatment, so that acid mist in the tail gas is removed, and the tail gas reaches the emission standard. The device has the advantages that pollutants generated in the tail gas calcination process can be fully absorbed, and the tail gas dust content is reduced.

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 for ultra-low emission of dust content in tail gas from titanium dioxide calcination. Background Art

[0002] Titanium dioxide is an important inorganic chemical pigment, the main component of which is titanium dioxide. The chemical properties of titanium dioxide are extremely stable, and it is an acidic amphoteric oxide. It hardly reacts with other elements and compounds at room temperature, and has no effect on oxygen, ammonia, nitrogen, hydrogen sulfide, carbon dioxide, and sulfur dioxide. It is insoluble in water, fat, dilute acid, inorganic acid, and alkali, and is only soluble in hydrofluoric acid. However, under the action of light, titanium dioxide can undergo continuous redox reactions and has photochemical activity. This kind of photochemical activity is particularly obvious in anatase titanium dioxide under ultraviolet irradiation. This property makes titanium dioxide both a photosensitive oxidation catalyst for some inorganic compounds and a photosensitive reduction catalyst for some organic compounds. Titanium dioxide is widely used in various structural surface coatings, paper coatings and fillers, plastics and elastomers. Other uses include ceramics, glass, catalysts, coated fabrics, printing inks, roof paving particles and fluxes. There are two production processes for titanium dioxide: the sulfate process and the chloride process. The sulfate process is simpler than the chloride process and can use low-grade and relatively cheap minerals. Today, about 47% of the world's production capacity uses the sulfate process and 53% uses the chloride process, which has important uses in industries such as coatings, inks, papermaking, plastics and rubber, chemical fibers, and ceramics.

[0003] The traditional sulfuric acid method of titanium dioxide is mainly to use titanium ore or titanium slag mixed with sulfuric acid for acid hydrolysis reaction, and use titanium sulfate as the material for hydrolysis to generate titanic acid, and then combine calcination, crushing and other processes to form titanium dioxide. The application advantage of the sulfuric acid method is mainly to achieve the effective refining of iron ore and sulfuric acid at a lower production cost. The production process is relatively mature, and the operation is simple, the production is convenient, the cost is controllable, and it can meet the basic needs of intermittent production. However, the biggest problem of this process is that there is a serious pollution problem in the calcination tail gas, especially the large amount of sulfuric acid, wastewater and other products, and the air pollution, environmental pollution and water pollution are relatively serious. The main raw material for titanium dioxide production is titanic acid. This kind of substance has high temperature and air humidity during calcination, and objectively there are emission conditions for undesirable gases such as titanium dioxide dust, acid mist, and sulfur oxides. According to the data analysis of a titanium dioxide production workshop, it is necessary to emit about 20,000m3 of carbon dioxide for every 1t of titanium dioxide produced. 3 The waste gas, and the temperature of the waste gas is between 200 and 400°C, objectively aggravates the waste gas pollution and deepens the diffusion of the waste gas.

[0004] At present, the main problems of traditional titanium dioxide calcination tail gas treatment technology are excessive production temperature, excessive humidity, and the emission of sulfur dioxide, dust particles, non-condensable gases, water vapor, acid mist and other substances, which will directly or indirectly affect the implementation of the production process. In the cyclone dust collection, Venturi spray system, water washing tower, electric demisting, chimney and other links, due to the influence of various objective factors, the actual tail gas treatment process cannot meet the corresponding emission standards, which leads to a series of emission problems and production risks. Summary of the invention

[0005] The invention discloses a method for ultra-low emission of tail gas dust content during titanium dioxide calcination, which is intended to solve the technical problem that in the existing titanium dioxide calcination process, due to the influence of various objective factors, the actual tail gas treatment process cannot meet the corresponding emission standards, thereby resulting in a high tail gas dust content.

[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 ultra-low emission of dust content in tail gas from calcining titanium dioxide comprises the following steps:

[0008] S1: The tail gas after calcination of titanium dioxide is sprayed once to preliminarily remove dust and sulfur dioxide pollutants in the tail gas;

[0009] S2: The tail gas after treatment in S1 is subjected to secondary water spray treatment to absorb the sodium sulfite produced in S1;

[0010] S3: The tail gas treated by S2 is subjected to demisting treatment to remove the acid mist in the tail gas so that the tail gas meets the emission standards.

[0011] By adopting this technical method, since the main raw material for titanium dioxide production is titanic acid, the temperature and air humidity of this type of substance are high during calcination, there will be emissions of titanium dioxide dust, acid mist, sulfur oxides and other undesirable gases. Through dust removal and deacidification treatment, the tail gas can be pre-removed from the dust and sulfur oxides in the tail gas after calcination after one spray treatment, and the exhaust temperature of the tail gas can be effectively reduced during the spraying process. The tail gas after spraying is subjected to a secondary water spray treatment to absorb the sodium sulfite produced in S1, further reducing the exhaust gas pollution, and then the tail gas is demisted. After the dual cooling effect of the first spray treatment and the secondary water spray treatment on the tail gas, the demisting effect of the subsequent tail gas demisting process is fully improved, the corresponding tail gas emission standards are met, the pollution to the environment is reduced, and the tail gas treatment effect in the titanium dioxide production process is further improved.

[0012] The present invention preferably provides a method for ultra-low emission of dust content in tail gas from calcining titanium dioxide, wherein the tail gas treated with S2 is subjected to circulating cooling treatment.

[0013] By adopting this technical method, the exhaust gas after calcining titanium dioxide can be fully cooled down, which can not only fully absorb the sodium sulfite in the exhaust gas, but also reduce the treatment temperature of the exhaust gas and improve the effect of subsequent demisting treatment, thereby fully removing the acid mist in the exhaust gas and making the exhaust gas meet the emission standards.

[0014] The present invention preferably provides an ultra-low emission method for tail gas dust content during calcination of titanium dioxide. When the tail gas temperature after S2 treatment is above 50°C±3°C, circulating cooling is required. When the tail gas temperature after S2 treatment is below 50°C±3°C, demisting treatment is directly performed.

[0015] By adopting this technical method, the tail gas after calcining titanium dioxide is sufficiently cooled after undergoing the first spray treatment and the second water spray treatment in sequence. When the tail gas temperature is above 50℃±3℃, it needs to be subjected to cyclic cooling treatment to improve the subsequent demisting treatment effect. When the tail gas temperature is below 50℃±3℃, it can directly enter the subsequent demisting treatment to improve the subsequent demisting treatment effect.

[0016] The present invention preferably provides an ultra-low emission device for exhaust dust content in titanium dioxide calcining tail gas, comprising an exhaust gas spray assembly, a water-cooled spray tower and an exhaust gas demister assembly which are connected in sequence through a vent pipe, the exhaust gas spray assembly comprising a cyclone dust collector, an acid mist spray tower, a water wash spray tower and an alkali solution spray tower which are connected in sequence, the exhaust gas demister assembly comprising a first electric demister and a second electric demister which are connected in sequence, one end of the water-cooled spray tower is connected to the alkali solution spray tower, and the other end of the water-cooled spray tower is connected to the first electric demister.

[0017] By adopting this technical method, the tail gas spray component, the water-cooled spray tower and the tail gas demisting component are connected in sequence. After the tail gas in the titanium dioxide production process passes through the tail gas spray component, the dust and oxysulfide in the tail gas can be removed while the exhaust temperature of the tail gas can be reduced. Then, the tail gas passes through the cooling spray of the water-cooled spray tower, which can improve the subsequent demisting effect of the tail gas. It is a coherent process flow. The cyclone dust collector subjects the tail gas to the centrifugal force and separates the dust particles from the gas, which has a high dust removal efficiency. The acid mist spray tower uses an acidifier to effectively reduce tail gas pollutants such as sulfur dioxide and nitrogen oxides. The water washing spray tower further absorbs sulfur dioxide and dust in the tail gas to reduce the tail gas temperature. The alkali solution spray tower removes sulfur dioxide by alkaline water washing. Sodium hydroxide and sulfur dioxide react to produce sodium sulfite solution or sodium bisulfite solution to remove sulfur dioxide in the exhaust gas. The exhaust gas is discharged after dust removal and deacidification treatment in the cyclone dust collector, the acid mist spray tower, the water wash spray tower and the alkali solution spray tower along the ventilation pipe, meeting the exhaust gas emission standards. After the alkali solution is sprayed on the exhaust gas, the exhaust gas enters the water-cooled spray tower through the ventilation pipe for cooling treatment. Cold water is sprayed on the exhaust gas inside the water-cooled spray tower, so that the by-products such as sodium sulfite generated after the exhaust gas spray component are absorbed by the spray water, and it can be ensured that the temperature entering the exhaust gas demisting component can improve the subsequent demisting effect and meet the exhaust gas emission standards. The multi-stage demisting of the first electrostatic precipitator and the second electrostatic precipitator can further calcine the dust content in the exhaust gas.

[0018] The present invention preferably provides an ultra-low emission device for exhaust dust content in titanium dioxide calcination tail gas, wherein the vent pipe comprises a first vent pipe, a second vent pipe, a third vent pipe, a fourth vent pipe, a fifth vent pipe and a sixth vent pipe, and the first vent pipe, the second vent pipe, the third vent pipe, the fourth vent pipe, the fifth vent pipe and the sixth vent pipe are respectively arranged between the cyclone dust collector, the acid mist spray tower, the water washing spray tower, the alkali solution spray tower, the water-cooled spray tower, the first electric precipitator and the second electric precipitator.

[0019] By adopting this technical solution, the tail gas from the calcination of titanium dioxide can be subjected to a primary spray treatment by the cyclone dust collector, the acid mist spray tower, the water wash spray tower, and the alkali solution spray tower, and then subjected to a secondary water spray treatment by the water-cooled spray tower, so that the tail gas temperature is reduced and the sodium sulfite produced by the alkali solution spray tower treatment is effectively absorbed. Finally, the first electrostatic precipitator and the second electrostatic precipitator are used for defog treatment to reduce the dust content of the tail gas, thereby forming a complete and effective tail gas treatment system.

[0020] The present invention preferably provides an ultra-low emission device for exhaust dust content from the calcination of titanium dioxide, wherein a three-way air outlet pipe is arranged at the upper end of the water-cooled spray tower, one end of the three-way air outlet pipe is connected to the fourth air pipe through a circulation pipe, and the other end of the three-way air outlet pipe is connected to the fifth air pipe.

[0021] By adopting this technical method, the tail gas treated by the alkali solution spray tower will produce sodium sulfite, so the tail gas is passed through the fourth ventilation pipe into the water-cooled spray tower to absorb the sodium sulfite. At the same time, the temperature of the tail gas is reduced through the secondary water spray treatment. For the tail gas with a lower temperature, it directly enters the first electric demister through the fifth ventilation pipe for defog treatment. For the tail gas with a higher temperature, it can enter the water-cooled spray tower again through the circulation pipe along the fourth ventilation pipe for cooling and absorption treatment, thereby realizing a cycle process of tail gas cooling and dust removal.

[0022] The present invention preferably provides an ultra-low emission device for exhaust dust content in the calcination of titanium dioxide, wherein a first controller and a temperature sensor are arranged at the upper end of the water-cooled spray tower, a first three-way solenoid valve is arranged on the three-way air outlet pipe, and the first three-way solenoid valve and the temperature sensor are both electrically connected to the first controller.

[0023] By adopting this technical method, the three-way air outlet pipe is respectively connected to the exhaust gas demisting assembly and the exhaust gas spray assembly, so that after passing through the water-cooled spray tower, the exhaust gas enters different processing equipment according to the temperature. When the temperature sensor senses that the rising exhaust gas temperature is less than 50℃±3℃, the first three-way solenoid valve is opened by the first controller, and the exhaust gas enters the subsequent demisting treatment through the three-way air outlet pipe. When the temperature sensor senses that the rising exhaust gas temperature is greater than 50℃±3℃, the flow direction of the first three-way solenoid valve is changed by the first controller, and the exhaust gas enters the fourth ventilation pipe through the circulation pipe and enters the water-cooled spray tower together with the exhaust gas treated by the alkali solution spray tower for circulation cooling treatment.

[0024] The present invention preferably provides an ultra-low emission device for dust content in tail gas from calcining titanium dioxide, wherein a first liquid outlet pipe, a first pH sensor and a second controller are arranged at the lower end of the water-cooled spray tower, the first liquid outlet pipe is arranged as a three-way structure, and one end of the first liquid outlet pipe is connected to the spray layer of the water-cooled spray tower, the other end of the first liquid outlet pipe is connected to the spray layer of the alkali solution spray tower, a second three-way solenoid valve is arranged on the first liquid outlet pipe, and the first pH sensor and the second three-way solenoid valve are both electrically connected to the second controller.

[0025] By adopting this technical method, when the tail gas moves from the bottom to the top of the water-cooled spray tower, water is sprayed downward from the top of the water-cooled spray tower, so that the tail gas is fully sprayed and absorbed. The water sprayed from the water-cooled spray tower can flow to the water-cooled spray tower or the alkali solution spray tower through the first liquid outlet pipe for recycling and spraying, saving the use of spray water and improving the utilization rate of spray water. When the spray water after spraying the tail gas falls to the bottom of the water-cooled spray tower, the first pH sensor monitors the pH value of the spray water at the bottom. When the pH is greater than 9, the flow direction of the second three-way solenoid valve is adjusted by the second controller, so that the spray water flows into the alkali solution spray tower to act as alkali solution for spraying; when the pH is less than 9, the second controller controls the second three-way solenoid valve to change the flow direction, so that the spray water flows back to the water-cooled spray tower for circulating cooling and spraying.

[0026] The present invention preferably provides an ultra-low emission device for dust content in tail gas from the calcination of titanium dioxide, wherein a second liquid outlet pipe, a second pH sensor and a third controller are arranged at the lower end of the water washing spray tower, the second liquid outlet pipe is arranged as a three-way structure, and one end of the second liquid outlet pipe is connected to the spray layer of the water washing spray tower, the other end of the second liquid outlet pipe is connected to the spray layer of the acid mist spray tower, a third three-way solenoid valve is arranged on the second liquid outlet pipe, and the second pH sensor and the third three-way solenoid valve are both electrically connected to the third controller.

[0027] By adopting this technical method, the spray water in the water-washing spray tower absorbs sulfur dioxide in the tail gas after spraying the tail gas, thereby making the spray liquid acidic. The spray water can flow to the water-washing spray tower through the second liquid outlet pipe for repeated spraying, or flow into the acid mist spray tower to act as acid liquid to purify the tail gas, making full use of the spray water and saving water resources. In the process of spraying the tail gas after calcination, with the absorption of the tail gas and the addition of new spray water, the spray water at the bottom of the water-washing spray tower will present different pH values. The pH sensor is used to monitor the pH value of the spray water at the bottom. When the pH value is less than 5, the third controller adjusts the flow direction of the third three-way solenoid valve so that the spray water flows into the acid mist spray tower to act as acid liquid for spraying; when the pH value is greater than 5, the third controller controls the third three-way solenoid valve to change the flow direction so that the spray water flows back to the water washing spray tower for circulating cooling and spraying. The third controller controls the third three-way solenoid valve to automatically adjust the automatic operation of the spray water, so that the exhaust gas emission is automated and manpower is fully saved.

[0028] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0029] 1. The tail gas spray assembly, the water-cooled spray tower and the tail gas demisting assembly are connected in sequence. After the tail gas in the titanium dioxide production process passes through the tail gas spray assembly, the dust and oxysulfide in the tail gas can be removed while reducing the exhaust temperature of the tail gas. Subsequently, the tail gas passes through the cooling spray of the water-cooled spray tower, which can improve the subsequent demisting effect of the tail gas;

[0030] 2. After passing through the water-cooled spray tower, the exhaust gas flows into different treatment equipment according to the temperature. When the temperature sensor senses that the rising exhaust gas temperature is less than 50°C±3°C, the first three-way solenoid valve is opened through the first controller, and the exhaust gas enters the subsequent defogger through the three-way outlet pipe. When the temperature sensor senses that the rising exhaust gas temperature is greater than 50°C±3°C, the flow direction of the first three-way solenoid valve is changed through the first controller, and the exhaust gas enters the fourth ventilation pipe through the circulation pipe, and enters the water-cooled spray tower together with the exhaust gas treated by the alkali solution spray tower for cooling treatment, thereby ensuring that the temperature entering the exhaust gas defogger assembly can improve the subsequent defogger effect and meet the exhaust gas emission standards;

[0031] 3. The third controller controls the third three-way solenoid valve to adjust the spray water, and the second controller controls the second three-way solenoid valve to adjust the spray water automatically, so that the exhaust emission is automated and manpower is fully saved. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The present invention will now be described by way of example with reference to the accompanying drawings, in which:

[0033] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0034] Figure 2 This is a side structural perspective view of a water-cooled spray tower;

[0035] Figure 3 This is a side structural perspective view of the water washing spray tower.

[0036] Reference numerals

[0037] 1-cyclone dust collector, 2-acid mist spray tower, 3-water washing spray tower, 4-alkali solution spray tower, 5-water cooling spray tower, 6-first electric demister, 7-second electric demister, 8-three-way air outlet pipe, 9-first three-way solenoid valve, 10-second three-way solenoid valve, 11-third three-way solenoid valve, 12-circulation pump, 13-first liquid outlet pipe, 14-second liquid outlet pipe, 15-ventilation pipe, 151-first ventilation pipe, 152-second ventilation pipe, 153-third ventilation pipe, 154-fourth ventilation pipe, 155-fifth ventilation pipe, 156-sixth ventilation pipe, 16-temperature sensor, 17-first pH sensor, 18-second pH sensor, 19-first controller, 20-second controller, 21-third controller, 22-circulation pipe. DETAILED DESCRIPTION

[0038] To make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in 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.

[0039] 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.

[0040] 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.

[0041] Example 1

[0042] A method for ultra-low emission of dust content in tail gas from calcining titanium dioxide comprises the following steps:

[0043] S1: The tail gas after calcination of titanium dioxide is sprayed once to preliminarily remove dust and sulfur dioxide pollutants in the tail gas;

[0044] S2: The tail gas after treatment in S1 is subjected to secondary water spray treatment to absorb the sodium sulfite produced in S1;

[0045] S3: The tail gas treated by S2 is subjected to demisting treatment to remove the acid mist in the tail gas so that the tail gas meets the emission standards.

[0046] By adopting this technical method, since the main raw material for titanium dioxide production is titanic acid, the temperature and air humidity of this type of substance are high during calcination, there will be emissions of titanium dioxide dust, acid mist, sulfur oxides and other undesirable gases. Through dust removal and deacidification treatment, the tail gas can be pre-removed from the dust and sulfur oxides in the tail gas after calcination after one spray treatment, and the exhaust temperature of the tail gas can be effectively reduced during the spraying process. The tail gas after spraying is subjected to a secondary water spray treatment to absorb the sodium sulfite produced in S1, further reducing the exhaust gas pollution, and then the tail gas is demisted. After the dual cooling effect of the first spray treatment and the secondary water spray treatment on the tail gas, the demisting effect of the subsequent tail gas demisting process is fully improved, the corresponding tail gas emission standards are met, the pollution to the environment is reduced, and the tail gas treatment effect in the titanium dioxide production process is further improved.

[0047] The tail gas treated by S2 is circulated and cooled.

[0048] By adopting this technical method, the exhaust gas after calcining titanium dioxide can be fully cooled down, which can not only fully absorb the sodium sulfite in the exhaust gas, but also reduce the treatment temperature of the exhaust gas and improve the effect of subsequent demisting treatment, thereby fully removing the acid mist in the exhaust gas and making the exhaust gas meet the emission standards.

[0049] When the temperature of the exhaust gas after S2 treatment is above 50℃±3℃, circulating cooling is required. When the temperature of the exhaust gas after S2 treatment is below 50℃±3℃, demisting treatment is directly carried out.

[0050] By adopting this technical method, the tail gas after calcining titanium dioxide is sufficiently cooled after undergoing the first spray treatment and the second water spray treatment in sequence. When the tail gas temperature is above 50℃±3℃, it needs to be subjected to cyclic cooling treatment to improve the subsequent demisting treatment effect. When the tail gas temperature is below 50℃±3℃, it can directly enter the subsequent demisting treatment to improve the subsequent demisting treatment effect.

[0051] A device for ultra-low emission of dust content in tail gas from calcining titanium dioxide, comprising a tail gas spray assembly, a water-cooled spray tower 5 and a tail gas demister assembly which are connected in sequence through a vent pipe 15, wherein the tail gas spray assembly comprises a cyclone dust collector 1, an acid mist spray tower 2, a water wash spray tower 3 and an alkali solution spray tower 4 which are connected in sequence, and the tail gas demister assembly comprises a first electric demister 6 and a second electric demister 7 which are connected in sequence, one end of the water-cooled spray tower 5 is connected to the alkali solution spray tower 4, and the other end of the water-cooled spray tower 5 is connected to the first electric demister 6.

[0052] By adopting this technical method, the tail gas spray component, the water-cooled spray tower 5 and the tail gas demisting component are connected in sequence. After the tail gas in the titanium dioxide production process passes through the tail gas spray component, the dust and oxysulfide in the tail gas can be removed while reducing the exhaust temperature of the tail gas. Then, the tail gas passes through the cooling spray of the water-cooled spray tower 5, which can improve the subsequent demisting effect of the tail gas. It is a coherent process flow. The cyclone dust collector 1 makes the tail gas subject to centrifugal force to separate the dust particles from the gas, and has a high dust removal efficiency. The acid mist spray tower 2 uses an acidifier to effectively reduce tail gas pollutants such as sulfur dioxide and nitrogen oxides. The water washing spray tower 3 further absorbs sulfur dioxide and dust in the tail gas to reduce the tail gas temperature. The alkali solution spray tower 4 removes sulfur dioxide by alkaline water washing, and adopts hydrogen hydroxide Sodium and sulfur dioxide react to produce sodium sulfite solution or sodium bisulfite solution to remove sulfur dioxide in the exhaust gas. The exhaust gas is discharged after dust removal and deacidification treatment in the cyclone dust collector 1, the acid mist spray tower 2, the water washing spray tower 3 and the alkali solution spray tower 4 along the ventilation pipe 15, which meets the exhaust gas emission standards. After the alkali solution is sprayed on the exhaust gas, the exhaust gas enters the water-cooled spray tower 5 through the ventilation pipe 15 for cooling treatment. Cold water is sprayed on the exhaust gas inside the water-cooled spray tower 5, so that the by-products such as sodium sulfite generated after the exhaust gas spray component are absorbed by the spraying water, and it can be ensured that the temperature entering the exhaust gas demisting component can improve the subsequent demisting effect and meet the exhaust gas emission standards. The multi-stage demisting of the first electrostatic precipitator 6 and the second electrostatic precipitator 7 can further calcine the dust content in the exhaust gas.

[0053] The ventilation pipe 15 includes a first ventilation pipe 151, a second ventilation pipe 152, a third ventilation pipe 153, a fourth ventilation pipe 154, a fifth ventilation pipe 155 and a sixth ventilation pipe 156. The first ventilation pipe 151, the second ventilation pipe 152, the third ventilation pipe 153, the fourth ventilation pipe 154, the fifth ventilation pipe 155 and the sixth ventilation pipe 156 are respectively arranged between the cyclone dust collector 1, the acid mist spray tower 2, the water washing spray tower 3, the alkali solution spray tower 4, the water-cooled spray tower 5, the first electric precipitator 6 and the second electric precipitator 7.

[0054] By adopting this technical solution, the exhaust gas from the calcination of titanium dioxide can be subjected to a primary spray treatment by the cyclone dust collector 1, the acid mist spray tower 2, the water washing spray tower 3, and the alkali solution spray tower 4, and then subjected to a secondary water spray treatment by the water-cooled spray tower 5, so that the exhaust gas temperature is reduced and the sodium sulfite produced by the alkali solution spray tower 4 is effectively absorbed. Finally, the exhaust gas is subjected to a defog treatment by the first electrostatic precipitator 6 and the second electrostatic precipitator 7, so as to reduce the dust content of the exhaust gas and form a complete and effective exhaust gas treatment system.

[0055] A three-way air outlet pipe 8 is provided at the upper end of the water-cooled spray tower 5 , one end of the three-way air outlet pipe 8 is connected to the fourth air pipe 154 through the circulation pipe 22 , and the other end of the three-way air outlet pipe 8 is connected to the fifth air pipe 155 .

[0056] By adopting this technical method, the exhaust gas treated by the alkali solution spray tower 4 will produce sodium sulfite, so the exhaust gas is passed through the fourth ventilation pipe 154 into the water-cooled spray tower 5 to absorb the sodium sulfite. At the same time, the exhaust gas temperature is reduced through the secondary water spray treatment. For the exhaust gas with a lower temperature, it directly enters the first electric precipitator 6 through the fifth ventilation pipe 155 for defog treatment. For the exhaust gas with a higher temperature, it can pass through the circulation pipe 22 and enter the water-cooled spray tower 5 again along the fourth ventilation pipe 154 for cooling and absorption treatment, thereby realizing a cycle process of exhaust gas cooling and dust removal.

[0057] A first controller 19 and a temperature sensor 16 are disposed at the upper end of the water-cooled spray tower 5 , a first three-way solenoid valve 9 is disposed on the three-way air outlet pipe 8 , and both the first three-way solenoid valve 9 and the temperature sensor 16 are electrically connected to the first controller 19 .

[0058] By adopting this technical method, the three-way air outlet pipe 8 is respectively connected to the exhaust gas demisting component and the exhaust gas spray component, so that after passing through the water-cooled spray tower 5, the exhaust gas enters different treatment equipment according to the temperature. When the temperature sensor 16 senses that the rising exhaust gas temperature is less than 50℃±3℃, the first three-way solenoid valve 9 is opened through the first controller 19, and the exhaust gas enters the subsequent demisting treatment through the three-way air outlet pipe 8. When the temperature sensor 16 senses that the rising exhaust gas temperature is greater than 50℃±3℃, the flow direction of the first three-way solenoid valve 9 is changed through the first controller 19, and the exhaust gas enters the fourth ventilation pipe 154 through the circulation pipe 22 and enters the water-cooled spray tower 5 together with the exhaust gas treated by the alkali solution spray tower 4 for circulation cooling treatment.

[0059] A first liquid outlet pipe 13, a first pH sensor 17 and a second controller 20 are provided at the lower end of the water-cooled spray tower 5. The first liquid outlet pipe 13 is configured as a three-way structure, and one end of the first liquid outlet pipe 13 is connected to the spray layer of the water-cooled spray tower 5, and the other end of the first liquid outlet pipe 13 is connected to the spray layer of the alkali solution spray tower 4. A second three-way solenoid valve 10 is provided on the first liquid outlet pipe 13, and the first pH sensor 17 and the second three-way solenoid valve 10 are both electrically connected to the second controller 20.

[0060] With this technical method, when the tail gas moves from the water-cooled spray tower 5 from bottom to top, water is sprayed downward from the top of the water-cooled spray tower 5, so that the tail gas is fully sprayed and absorbed. The water sprayed from the water-cooled spray tower 5 can flow through the first liquid outlet pipe 13 to the water-cooled spray tower 5 or the alkali solution spray tower 4 for recycling and spraying, saving the use of spray water and improving the utilization rate of spray water. Both ends of the first liquid outlet pipe 13 are provided with a circulation pump 12, and the spray water is respectively transmitted to the spray layer of the water-cooled spray tower 5 and the alkali solution spray tower 4 through the circulation pump 12. The spray layer of the alkali solution spray tower 4 is used for recycling. When the spray water after spraying the tail gas falls to the bottom of the water-cooled spray tower 5, the first pH sensor 17 monitors the pH value of the spray water at the bottom. When the pH is greater than 9, the second controller 20 adjusts the flow direction of the second three-way solenoid valve 10 so that the spray water flows into the alkali solution spray tower 4 to act as alkali solution for spraying; when the pH is less than 9, the second controller 20 controls the second three-way solenoid valve 10 to change the flow direction so that the spray water flows back to the water-cooled spray tower 5 for circulating cooling and spraying.

[0061] A second liquid outlet pipe 14, a second pH sensor 18 and a third controller 21 are provided at the lower end of the water washing spray tower 3. The second liquid outlet pipe 14 is configured as a three-way structure, and one end of the second liquid outlet pipe 14 is connected to the spray layer of the water washing spray tower 3, and the other end of the second liquid outlet pipe 14 is connected to the spray layer of the acid mist spray tower 2. A third three-way solenoid valve 11 is provided on the second liquid outlet pipe 14, and the second pH sensor 18 and the third three-way solenoid valve 11 are both electrically connected to the third controller 21.

[0062] By adopting this technical method, the spray water in the water-washing spray tower 3 absorbs sulfur dioxide in the tail gas after spraying the tail gas, thereby making the spray liquid acidic. The spray water can flow to the water-washing spray tower 3 through the second liquid outlet pipe 14 for repeated spraying, or flow into the acid mist spray tower 2 to act as acid liquid to purify the tail gas, making full use of the spray water and saving water resources. The circulating pump 12 is provided at both ends of the second liquid outlet pipe 14, and the spray water is respectively transmitted to the spray layer of the water-washing spray tower 3 and the spray layer of the acid mist spray tower 2 for recycling. In the process of spraying the tail gas after calcination, as the tail gas is absorbed and new spray water is sprayed, the tail gas is purified. In addition, the spray water at the bottom of the water washing spray tower 3 will present different pH values. The second pH sensor 18 is used to monitor the pH value of the spray water at the bottom. When the pH value is less than 5, the third controller 21 adjusts the flow direction of the third three-way solenoid valve 11 so that the spray water flows into the acid mist spray tower 2 to act as acid for spraying; when the pH value is greater than 5, the third controller 21 controls the third three-way solenoid valve 11 to change the flow direction so that the spray water flows back to the water washing spray tower 3 for circulating cooling and spraying. The third controller 21 controls the third three-way solenoid valve 11 to automatically adjust the automatic operation of the spray water, so that the exhaust gas emission is automated and manpower is fully saved.

[0063] The tail gas after calcining titanium dioxide is processed in sequence by the cyclone dust collector 1, the acid mist spray tower 2, the water washing spray tower 3, the alkali solution spray tower 4, the water cooling spray tower 5, the first electrostatic precipitator 6 and the second electrostatic precipitator 7, and the dust content of the tail gas is measured to be 10 mg / m3.

[0064] Example 2

[0065] The difference between this embodiment and embodiment 1 is that the exhaust gas after calcining titanium dioxide is processed by the cyclone dust collector 1, the acid mist spray tower 2, the water washing spray tower 3, the alkali solution spray tower 4, the water-cooled spray tower 5 and the first electrostatic precipitator 6 in sequence, and the dust content of the exhaust gas is measured to be 35 mg / m3.

[0066] Example 3

[0067] The difference between this embodiment and embodiment 1 is that the exhaust gas after calcining titanium dioxide is processed by the cyclone dust collector 1, the acid mist spray tower 2, the water washing spray tower 3, the alkali solution spray tower 4, the first electrostatic precipitator 6 and the second electrostatic precipitator 7 in sequence, and the dust content of the exhaust gas is measured to be 50 mg / m3.

[0068] Comparative Example

[0069] The tail gas after calcination of titanium dioxide passes through the cyclone dust collector 1, the acid mist spray tower 2, the water washing spray tower 3, the alkali solution spray tower 4, and the first electrostatic precipitator 6 in sequence, and the dust content of the tail gas is measured to be 60 mg / m3.

[0070] 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 ultra-low emission of dust content in tail gas from calcining titanium dioxide, characterized in that: The steps include: S1: The tail gas after calcination of titanium dioxide is sprayed once to preliminarily remove dust and sulfur dioxide pollutants in the tail gas; S2: The tail gas after treatment in S1 is subjected to secondary water spray treatment to absorb the sodium sulfite produced in S1; S3: The tail gas treated by S2 is subjected to demisting treatment to remove the acid mist in the tail gas so that the tail gas meets the emission standards.

2. The method for ultra-low emission of dust content in tail gas from calcining titanium dioxide according to claim 1, characterized in that: The tail gas treated by S2 is circulated and cooled.

3. The method for ultra-low emission of dust content in tail gas from calcining titanium dioxide according to claim 2, characterized in that: When the temperature of the exhaust gas after S2 treatment is above 50℃±3℃, circulating cooling is required. When the temperature of the exhaust gas after S2 treatment is below 50℃±3℃, demisting treatment is directly carried out.

4. A device for ultra-low emission of tail gas dust content from calcined titanium dioxide, used in a method for ultra-low emission of tail gas dust content from calcined titanium dioxide as claimed in claim 1, characterized in that: The invention comprises an exhaust gas spray assembly, a water-cooled spray tower (5) and an exhaust gas demisting assembly which are connected in sequence through a ventilation pipe (15); the exhaust gas spray assembly comprises a cyclone dust collector (1), an acid mist spray tower (2), a water-wash spray tower (3) and an alkali solution spray tower (4) which are connected in sequence; the exhaust gas demisting assembly comprises a first electric demister (6) and a second electric demister (7) which are connected in sequence; one end of the water-cooled spray tower (5) is connected to the alkali solution spray tower (4); and the other end of the water-cooled spray tower (5) is connected to the first electric demister (6).

5. The device for ultra-low emission of tail gas dust content from calcining titanium dioxide according to claim 4, characterized in that: The ventilation pipe (15) comprises a first ventilation pipe (151), a second ventilation pipe (152), a third ventilation pipe (153), a fourth ventilation pipe (154), a fifth ventilation pipe (155) and a sixth ventilation pipe (156); the first ventilation pipe (151), the second ventilation pipe (152), the third ventilation pipe (153), the fourth ventilation pipe (154), the fifth ventilation pipe (155) and the sixth ventilation pipe (156) are respectively arranged between the cyclone dust collector (1), the acid mist spray tower (2), the water washing spray tower (3), the alkali solution spray tower (4), the water cooling spray tower (5), the first electric precipitator (6) and the second electric precipitator (7).

6. The device for ultra-low emission of dust content in tail gas from calcining titanium dioxide according to claim 4, characterized in that: A three-way air outlet pipe (8) is provided at the upper end of the water-cooled spray tower (5); one end of the three-way air outlet pipe (8) is connected to the fourth air vent pipe (154) through a circulation pipe (22); and the other end of the three-way air outlet pipe (8) is connected to the fifth air vent pipe (155).

7. The device for ultra-low emission of dust content in tail gas from calcining titanium dioxide according to claim 6, characterized in that: A first controller (19) and a temperature sensor (16) are arranged at the upper end of the water-cooled spray tower (5), a first three-way solenoid valve (9) is arranged on the three-way air outlet pipe (8), and the first three-way solenoid valve (9) and the temperature sensor (16) are both electrically connected to the first controller (19).

8. The device for ultra-low emission of tail gas dust from calcining titanium dioxide according to claim 4, characterized in that: A first liquid outlet pipe (13), a first pH sensor (17) and a second controller (20) are arranged at the lower end of the water-cooled spray tower (5); the first liquid outlet pipe (13) is arranged as a three-way structure, and one end of the first liquid outlet pipe (13) is connected to the spray layer of the water-cooled spray tower (5), and the other end of the first liquid outlet pipe (13) is connected to the spray layer of the alkali solution spray tower (4); a second three-way solenoid valve (10) is arranged on the first liquid outlet pipe (13), and the first pH sensor (17) and the second three-way solenoid valve (10) are both electrically connected to the second controller (20).

9. The device for ultra-low emission of tail gas dust from calcining titanium dioxide according to claim 4, characterized in that: A second liquid outlet pipe (14), a second pH sensor (18) and a third controller (21) are arranged at the lower end of the water-wash spray tower (3); the second liquid outlet pipe (14) is arranged as a three-way structure, and one end of the second liquid outlet pipe (14) is connected to the spray layer of the water-wash spray tower (3), and the other end of the second liquid outlet pipe (14) is connected to the spray layer of the acid mist spray tower (2); a third three-way solenoid valve (11) is arranged on the second liquid outlet pipe (14), and the second pH sensor (18) and the third three-way solenoid valve (11) are both electrically connected to the third controller (21).

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