Emission reduction and consumption reduction process and device for reducing ferric iron in titaniferous solution by using rotary kiln calcination tail gas sulfur dioxide

Abstract

The invention discloses an emission reduction and consumption reduction process and device for reducing ferric iron in a titaniferous solution by using rotary kiln calcination tail gas sulfur dioxide, and relates to the technical field of sulfuric acid method titanium dioxide production. The device comprises a cyclone dust collector, a multi-stage spray tower and the like, the ferric iron-containing titanium solution obtained by acidolysis leaching is used for secondary spraying of the rotary kiln calcination tail gas, so that sulfur dioxide in the tail gas is dissolved and captured by the titanium solution and is subjected to redox reaction with ferric iron ions in the titanium solution, the ferric iron is reduced into ferrous iron, and the secondary spraying of the tail gas is realized. Sulfur dioxide is oxidized into sulfur trioxide and fixed into sulfuric acid. Resource utilization of waste gas sulfur dioxide is achieved, consumption of reduced iron powder and caustic soda is remarkably reduced, the tail gas purification effect is improved, and waste gas resource utilization, cost reduction and efficiency improvement are achieved.

Description

Technical Field

[0001] This invention relates to the field of sulfuric acid process titanium dioxide production technology, and in particular to a process and apparatus for reducing emissions and energy consumption by using sulfur dioxide from rotary kiln calcination tail gas to reduce trivalent iron in titanium liquid. Background Technology

[0002] In the sulfuric acid process for titanium dioxide production using ilmenite as raw material, the titanium liquor leached from the acidolysis reaction contains a high concentration of ferric ions (Fe3+), which need to be converted to ferrous ions (Fe2+) through reduction treatment. The industry's conventional method uses reduced iron powder for reduction, consuming 60-142 kg of iron powder per ton of titanium dioxide produced, resulting in high costs. Simultaneously, the flue gas from the rotary kiln calcination contains a large amount of sulfur dioxide, requiring neutralization by spraying with caustic soda solution, consuming 29-40 kg of caustic soda per ton of titanium dioxide, also significantly increasing costs. Existing technologies mostly focus on flue gas purification or dust treatment, but fail to achieve the resource utilization of sulfur dioxide, resulting in limited cost reduction. For example, patent CN110479058A discloses a device and method for purifying flue gas from the acidolysis of titanium dioxide produced using the sulfuric acid process. This method uses a three-stage spraying process—a scrubbing tower, a venturi scrubbing tower, and an alkali scrubbing tower—to achieve water-alkali separation and pollutant removal from the flue gas. However, this technology targets acid hydrolysis tail gas and has a weak correlation with the treatment of rotary kiln calcination tail gas, and it does not involve the resource utilization of sulfur dioxide, so the cost reduction effect is not obvious.

[0003] Patent CN211025756U relates to a device for treating the tail gas from the acidolysis reaction in the preparation of titanium dioxide, which uses a complexed iron solution to react with sulfur dioxide to generate water and elemental sulfur. This technology, while also targeting the tail gas from acidolysis, does not utilize sulfur dioxide to reduce ferric ions in the titanium solution, thus failing to achieve resource utilization and cost reduction.

[0004] Patent CN119588116A proposes a method for ultra-low dust emission from titanium dioxide calcination tail gas, which reduces dust and pollutant content through multi-stage spraying and demisting treatment. Although this technology involves calcination tail gas, its focus is on dust control, without addressing the resource utilization of sulfur dioxide, nor does it help reduce the production cost of titanium dioxide.

[0005] Patent CN119701578A discloses a method and apparatus for treating tail gas during the acidolysis of titanium dioxide. It employs a combination of water spraying, wastewater reuse, and electrostatic precipitator processes to achieve compliant tail gas emissions and water conservation. However, this technology is still targeted at acidolysis tail gas and has low relevance to the treatment of rotary kiln calcination tail gas. Furthermore, it does not achieve the resource utilization of sulfur dioxide, resulting in limited cost reduction.

[0006] In summary, existing technologies primarily focus on exhaust gas purification or dust treatment, failing to utilize sulfur dioxide from rotary kiln calcination exhaust gas for reducing ferric ions in molten titanium, thus failing to simultaneously reduce the consumption of iron powder and caustic soda. Therefore, developing a process that can achieve resource utilization of waste gas while simultaneously reducing emissions and energy consumption is of significant practical importance.

[0007] The above background information is provided only to aid in understanding the inventive concept and technical solution of this invention. It does not necessarily belong to the prior art of this patent application. In the absence of clear evidence that the above information was disclosed on the filing date of this patent application, the above background information should not be used to evaluate the novelty and inventiveness of this application. Summary of the Invention

[0008] The purpose of this invention is to propose a process and device for reducing emissions and energy consumption by using sulfur dioxide from rotary kiln calcination tail gas to reduce ferric iron in titanium liquid. By utilizing sulfur dioxide from rotary kiln calcination tail gas to reduce ferric ions in titanium liquid, the waste gas can be recycled, thereby solving the technical problems existing in the prior art.

[0009] Therefore, the present invention adopts the following technical solution:

[0010] A device for reducing emissions and energy consumption by using sulfur dioxide from rotary kiln calcination tail gas to reduce ferric iron in titanium liquid includes a cyclone dust collector, a No. 1 spray tower, a No. 2 spray tower, a No. 3 spray tower, an electrostatic precipitator, a venturi separator, a cyclone separator, an induced draft fan, and a fiberglass chimney. The inlet of the cyclone dust collector is flush with the outlet of the rotary kiln tail gas, and it has an outlet at the top and a discharge port at the bottom. The bottom inlet of the No. 1 spray tower is connected to the outlet of the cyclone dust collector, and it has a nozzle and an exhaust port at the top. The bottom inlet of the No. 2 spray tower is connected to the exhaust port of the No. 1 spray tower, and it has a titanium liquid nozzle and an exhaust port at the top. The No. 3 spray tower... The bottom air inlet connects to the exhaust port of spray tower #2, and the top is equipped with a low-temperature water nozzle and an exhaust port; the bottom air inlet of the electrostatic precipitator connects to the exhaust port of spray tower #3, and the top is equipped with an air outlet; the top of the venturi is equipped with an air inlet and a low-temperature alkaline nozzle, the top air inlet of the venturi connects to the top air outlet of the electrostatic precipitator, and the bottom is equipped with an air outlet; the air inlet of the cyclone separator is located tangentially to the upper circumference and connects to the bottom air outlet of the venturi, the air outlet is located at the top, and the liquid discharge port is located at the bottom; the air inlet of the induced draft fan connects to the air outlet of the cyclone separator; the air inlet of the fiberglass chimney connects to the air outlet of the induced draft fan.

[0011] Preferably, the device further includes a slurry conveying pump, a thick slurry storage tank, a cyclone thickener, a primary spray pump, and a primary spray tank; the primary spray tank is connected to the nozzle at the top of the No. 1 spray tower via the primary spray pump, the discharge port at the bottom of the No. 1 spray tower is connected to the tangential material inlet at the top of the cyclone thickener, the dilute phase discharge port at the top of the cyclone thickener is connected to the primary spray tank, the thickening discharge port at the bottom is connected to the thick slurry storage tank, and the discharge port at the bottom of the thick slurry storage tank is connected to the slurry conveying pump; the cyclone thickener separates the spray liquid containing titanium dioxide dust particles discharged from the No. 1 spray tower into a dilute phase and a dense phase through rotational centrifugation, the dilute phase is returned to the primary spray tank for recycling, and the dense phase enters the thick slurry storage tank for sedimentation and thickening; the slurry conveying pump transports the slurry after sedimentation and thickening in the thick slurry storage tank to the slurry recovery station; the primary spray tank is equipped with a heat exchange coil and a stirring device.

[0012] Preferably, the device further includes a titanium liquid transfer pump, a low-ferric titanium liquid storage tank, a secondary spray pump, and a high-ferric titanium liquid storage tank; the high-ferric titanium liquid storage tank is connected to the titanium liquid nozzle at the top of the No. 2 spray tower via the secondary spray pump, the discharge port at the bottom of the No. 2 spray tower is connected to the low-ferric titanium liquid storage tank, and the discharge port at the bottom of the low-ferric titanium liquid storage tank is connected to the titanium liquid transfer pump; both the high-ferric titanium liquid storage tank and the low-ferric titanium liquid storage tank are provided with overflow ports at the top and discharge ports at the bottom; the high-ferric titanium liquid storage tank is equipped with a heat exchange coil and a stirring device.

[0013] Preferably, the device further includes a three-stage spray pump, a three-stage spray tank, a three-stage air-cooled tower, a three-stage cooling pump, a three-stage hot water tank, and a desalination liquid transfer pump; the three-stage spray tank is connected to the low-temperature water nozzle of the No. 3 spray tower via the three-stage spray pump, the bottom discharge port of the No. 3 spray tower is connected to the three-stage hot water tank, the three-stage hot water tank is connected to the bottom inlet of the three-stage air-cooled tower via the three-stage cooling pump, and the bottom outlet of the three-stage air-cooled tower is connected to the three-stage spray tank; the lower part of the three-stage hot water tank is provided with two discharge ports, one of which is connected to the three-stage cooling pump, and the other discharge port is connected to the desalination liquid transfer pump.

[0014] Preferably, the device further includes an alkali spray tank and an alkali spray pump; the alkali spray tank is connected to a low-alkaline nozzle in a Venturi via the alkali spray pump, and the bottom discharge port of the Venturi is connected to the alkali spray tank; the lower part of the alkali spray tank is provided with a discharge port, and a heat exchange coil and a stirring device are installed inside.

[0015] This invention also provides a process for reducing emissions and energy consumption of ferric iron in titanium liquid using sulfur dioxide from rotary kiln calcination tail gas, according to the above-described device for reducing emissions and energy consumption of ferric iron in titanium liquid using sulfur dioxide from rotary kiln calcination tail gas, comprising the following steps:

[0016] (1) Titanium liquid pretreatment and supply: The titanium liquid obtained by acid hydrolysis leaching with a titanium dioxide concentration of 125g / l-132g / l, a ferric ion concentration of 16g / l-37g / l, and a temperature of 58℃-63℃ is added to the high ferric titanium liquid storage tank and pressurized by a secondary spray pump in the No. 2 spray tower for secondary spraying of the kiln calcination tail gas;

[0017] (2) Multi-stage treatment of rotary kiln calcination tail gas: The rotary kiln calcination tail gas is treated by a multi-stage spray system. The first stage uses dilute acid water spray to cool down and remove dust. The second stage uses the titanium liquid spray to absorb sulfur dioxide and reduce ferric iron. The third stage uses clean water spray to recover titanium liquid droplets. The fourth stage uses dilute caustic soda solution spray to neutralize residual acidic substances.

[0018] (3) Subsequent treatment of titanium liquid: When the titanium liquid is circulated in the secondary spray until the concentration of ferric ions drops from the initial 16g / l-37g / l to 10g / l-31g / l, the titanium liquid is returned to the reduction tank and iron powder is added for complete reduction.

[0019] Preferably, during the secondary spraying process, the titanium liquid is kept at a temperature of 58°C-63°C by using 50°C-55°C warm water through coil heat exchange; after multiple cycles of spraying, the concentration of ferric ions in the titanium liquid is reduced by 5g / l-8g / l, thereby achieving complete absorption and utilization of sulfur dioxide generated during rotary kiln calcination.

[0020] Preferably, in the process of treating the exhaust gas from the rotary kiln calcination, the first-stage spray reduces the exhaust gas temperature from 260℃-280℃ to 55℃-65℃, the second-stage spray keeps the exhaust gas temperature at 56℃-62℃, and the third-stage spray uses clean water at 23℃-28℃ and maintains the spray liquid temperature at 26℃-32℃.

[0021] Preferably, after the titanium liquid undergoes two-stage spray reduction, when the concentration of ferric ions drops to 10 g / l-31 g / l, it is returned to the reduction tank, where excess iron powder is used for complete reduction, so that tetravalent titanium is partially reduced to trivalent titanium. The reduction operation is completed when the concentration of trivalent titanium reaches 0.5 g / l-1.5 g / l.

[0022] Preferably, the clean water used in the third-stage spray is recycled, and when the concentration of titanium dioxide in it reaches 20g / l-30g / l, it is returned to the acid leaching process; the concentration of the dilute caustic soda solution used in the fourth-stage spray is 5g / l-10g / l, and tap water is used to maintain the temperature of the caustic soda solution at 28℃-35℃ through coil heat exchange.

[0023] The beneficial effects of this invention compared to the prior art include:

[0024] (i) Resource utilization of waste gas to turn waste into treasure

[0025] Existing technologies mostly target the purification of acid hydrolysis tail gas, removing sulfur dioxide only through alkaline neutralization or complexation reactions, without realizing its resource utilization, and the treatment cost is high. This invention focuses on sulfur dioxide in rotary kiln calcination tail gas, utilizing its oxidizing properties to react with ferric ions in titanium liquid to undergo a redox reaction, converting sulfur dioxide into sulfuric acid and fixing it in the titanium liquid, while simultaneously reducing ferric ions to ferrous ions required for production. No additional oxidizing or reducing agents are needed, realizing high-value resource utilization of waste gas and breaking the traditional end-of-pipe treatment model.

[0026] Compared to existing technologies, this invention deeply couples exhaust gas treatment with titanium liquid reduction process, making "pollutants" a "raw material supplement" in the production process, reducing dependence on purchased reduced iron powder and reducing production costs from the source.

[0027] (II) Significantly reduce costs and increase efficiency to enhance corporate competitiveness

[0028] For every ton of titanium dioxide produced, the consumption of reduced iron powder can be reduced by 20-26 kg. Based on an iron powder price of 3 yuan / kg, this translates to a cost reduction of 60-78 yuan per ton. The consumption of caustic soda per ton of titanium dioxide is reduced by 32-37 kg. Based on a caustic soda price of 2.8 yuan / kg, this translates to a cost reduction of 89.6-103.6 yuan per ton. Combined with optimizations in other processes, the technology described in this invention can achieve cost savings of over 150 yuan per ton of titanium dioxide. For large-scale titanium dioxide production enterprises, this translates to annual cost reductions of tens of millions of yuan, significantly improving product profit margins and market competitiveness.

[0029] In terms of equipment technology, this invention uses heat exchange coils inside the high-ferric titanium liquid storage tank 18 to stably control the temperature of the titanium liquid at 58-63℃. The concentration of ferric iron can be reduced by 5-8g / L after three cycles of spraying. Compared with traditional processes, this shortens the titanium liquid reduction cycle and improves production efficiency.

[0030] (iii) Upgrade exhaust emission quality to meet environmental protection requirements

[0031] Multi-stage purification guarantee: Existing technologies mostly use 2-3 stages of spray treatment to treat exhaust gas. This invention innovatively designs a combined process of "cyclone dust removal + four-stage spray (dilute acid water + titanium liquid + clean water + dilute alkali solution) + electrostatic precipitator + cyclone liquid removal", wherein:

[0032] The No. 1 spray tower achieves exhaust gas cooling and deep dust removal; the No. 2 spray tower completes the resource absorption of sulfur dioxide; the No. 3 spray tower and electrostatic precipitator recover titanium liquid droplets, further cool and remove mist droplets; the Venturi and cyclone separator neutralize residual acidic substances and remove alkaline droplets. The final exhaust gas sulfur dioxide concentration is ≤33ppm and acid mist concentration is ≤21ppm, which are far lower than the emission indicators after treatment by existing technologies, avoiding the risk of production shutdown due to non-compliance with emission standards.

[0033] With dual temperature control of the No. 3 spray tower and the alkali spray tank, as well as droplet capture by the cyclone separator, the exhaust gas temperature is lower and carries fewer droplets, which can effectively reduce the white smoke phenomenon during emission and improve the company's environmental image.

[0034] (iv) Resource recycling and reuse to reduce waste

[0035] The circulating clean water in the No. 3 spray tower can capture titanium liquid droplets carried in the exhaust gas. When the titanium dioxide concentration in the clean water reaches 20-30 g / L, it is returned to the acid leaching process. At the same time, the titanium-containing dust in the No. 1 spray tower is treated by a cyclone thickener and a thick slurry storage tank, and then recovered to the slurry station by a slurry conveying pump. This maximizes the utilization of titanium resources, reduces the titanium loss rate, and improves the titanium dioxide yield.

[0036] The dilute acid water in the primary spray tank and the dilute alkali solution in the alkali spray tank are both circulated and sprayed, with only the loss replenished. Compared with existing technologies, this reduces the consumption of water resources and reagents, lowers the amount of wastewater to be treated, and conforms to the concept of circular economy development. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the emission reduction and energy saving process and equipment for reducing trivalent iron in titanium liquid using sulfur dioxide from rotary kiln calcination tail gas, as described in this invention; wherein the numbers in the diagram are: 01-Cyclone dust collector, 02-Spray tower #1, 03-Spray tower #2, 04-Spray tower #3, 05-Electrostatic precipitator, 06-Venturi, 07-Cyclone condenser, 08-Exhaust fan, 09-Fiberglass chimney, 10-Slurry conveying pump, 11-Thick slurry storage 12-Swirl thickener, 13-First-stage spray pump, 14-First-stage spray tank, 15-Titanium liquid transfer pump, 16-Low-Fe3O4 titanium liquid storage tank, 17-Second-stage spray pump, 18-High-Fe3O4 titanium liquid storage tank, 19-Third-stage spray pump, 20-Third-stage spray tank, 21-Third-stage air-cooling tower, 22-Third-stage cooling pump, 23-Third-stage hot water tank, 24-Desalinated liquid transfer pump, 25-Alkali spray pump, 26-Alkali spray tank;

[0038] Figure 2 This is a schematic diagram of the process flow and equipment for the three-stage spray electrostatic precipitator for removing mist droplets, which is commonly used in the industry as described in Comparative Example 1. Detailed Implementation

[0039] The foregoing has broadly described the features and technical advantages of the invention to facilitate a better understanding of its detailed description. Other features and advantages of the invention will be described below. Those skilled in the art will understand that the disclosed concepts and specific embodiments can be readily used as a basis for modifying or designing other structures to achieve the same objectives of the invention. Those skilled in the art will also recognize that such equivalent constructions do not depart from the spirit and scope of the invention. The novel features considered characteristic of the invention, its structure and operation, as well as further objects and advantages, will be better understood from the following description in conjunction with the accompanying drawings. However, it should be clearly understood that each feature provided is for description and illustration only and is not intended to limit the definition of the invention.

[0040] Non-limiting and non-exclusive embodiments will be described with reference to the following figures. It should be understood that the terminology used herein is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included within the invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range. The terms “comprising,” “including,” “having,” “containing,” etc., as used herein are open-ended, meaning they include but are not limited to.

[0041] Figure 1 This is a schematic diagram of the emission reduction and energy consumption reduction process and equipment for reducing ferric iron in titanium liquid using sulfur dioxide from rotary kiln calcination tail gas, as described in this invention. In this embodiment, the emission reduction and energy consumption reduction device for reducing ferric iron in titanium liquid using sulfur dioxide from rotary kiln calcination tail gas includes: 01-Cyclone dust collector, 02-Spray tower #1, 03-Spray tower #2, 04-Spray tower #3, 05-Electrostatic precipitator, 06-Venturi precipitator, 07-Cyclone condenser, 08-Exhaust fan, 09-Fiberglass chimney. 10-Slurry transfer pump, 11-Thick slurry storage tank, 12-Swirl thickener, 13-First-stage spray pump, 14-First-stage spray tank, 15-Titanium liquid transfer pump, 16-Low-ferric titanium liquid storage tank, 17-Second-stage spray pump, 18-High-ferric titanium liquid storage tank, 19-Third-stage spray pump, 20-Third-stage spray tank, 21-Third-stage air-cooling tower, 22-Third-stage cooling pump, 23-Third-stage hot water tank, 24-Desalinated liquid transfer pump, 25-Alkali spray pump, 26-Alkali spray tank;

[0042] The air inlet of the cyclone dust collector 01 is horizontally positioned with the exhaust outlet of the rotary kiln. An exhaust outlet is located at the top of the equipment, and a discharge port is located at the bottom. Its working principle is as follows: After the exhaust gas from the rotary kiln calcination enters the cyclone dust collector 01, it forms a rotating airflow. Under centrifugal force, the small amount of titanium dioxide dust particles carried in the exhaust gas are separated. The separated titanium dioxide dust particles are periodically discharged from the discharge port of the cyclone dust collector 01, while the preliminarily purified exhaust gas is discharged from the outlet of the cyclone dust collector 01 and enters the No. 1 spray tower 02 for further treatment.

[0043] The air inlet at the bottom of spray tower 02 is connected to the outlet of cyclone dust collector 01 via a curved pipe. The exhaust gas, after most of the titanium dioxide dust particles have been removed by the cyclone dust collector 01, enters spray tower 02 from the bottom, flows upwards, and exits from the top exhaust port. Washing water is sprayed downwards from the top of spray tower 02, creating a counter-current contact between the exhaust gas and the water mist. During this process, the water mist performs two functions: cooling the exhaust gas and further capturing and removing residual dust. After spray washing, the exhaust gas temperature drops from 280℃-320℃ to 55℃-65℃, and the dust content drops to below 5ppm.

[0044] The air inlet of spray tower #2 (03) is located at the bottom, and the air outlet is located at the top. Titanium liquid nozzles are evenly distributed at the top of spray tower #2 (03). The exhaust gas, cooled to 55℃-65℃ by spraying and washing in spray tower #1 (02), enters the tower from the bottom inlet of spray tower #2 (03). Titanium liquid containing 16g / L-37g / L of ferric ions is evenly sprayed downwards from the top of spray tower #2 (03). The titanium liquid first dissolves and captures sulfur dioxide in the exhaust gas. The sulfur dioxide dissolved in the titanium liquid undergoes a redox reaction with the ferric ions in the titanium liquid: ferric ions are reduced to ferrous ions, and sulfur dioxide is oxidized to sulfur trioxide. The sulfur trioxide dissolves in the titanium liquid to form sulfuric acid, which is then fixed.

[0045] The air inlet of spray tower #3 (04) is located at the bottom, and the air outlet is located at the top. Low-temperature water nozzles are evenly distributed at the top of spray tower #3. The exhaust gas (temperature approximately 55℃-60℃) after being dissolved and absorbed by titanium liquid in spray tower #2 (03) enters the tower from the bottom air inlet of spray tower #3 (04). Low-temperature water containing 0-30g / L of titanium dioxide and at a temperature of approximately 20℃-28℃ is evenly sprayed downwards from the top of spray tower #3 (04). The low-temperature water fully contacts the exhaust gas, further reducing its temperature to 25℃-42℃ and simultaneously washing and collecting any small amount of titanium liquid carried in the exhaust gas, thus achieving titanium liquid recovery.

[0046] The air inlet of the electrostatic precipitator 05 is located at the bottom, and the air outlet is located at the top. The exhaust gas (temperature approximately 25℃-42℃) after being cooled and washed by low-temperature water spray from spray tower 3 04 enters the equipment from the bottom air inlet of the electrostatic precipitator 05. The exhaust gas containing mist droplets is subjected to electrowinning by the electrodes of the electrostatic precipitator 05, and most of the mist droplets are captured and eliminated, creating conditions for subsequent exhaust gas to meet emission standards.

[0047] The Venturi 06 has its inlet at the top and its outlet at the bottom, with low-alkaline solution nozzles evenly distributed at the top. The exhaust gas, after the electrostatic precipitator 05 removes droplets, enters the equipment through the top inlet of the Venturi 06 and then flows downwards to the outlet. A low-alkaline solution containing 5%-10% caustic soda is evenly sprayed downwards from the top of the Venturi 06, creating a counter-current contact with the exhaust gas. This alkaline solution further neutralizes acidic substances in the exhaust gas, ensuring that the pH value of the exhaust gas meets the required emission standards.

[0048] The air inlet of the cyclone separator 07 is located tangentially to the upper circumference, the air outlet is located at the top, and the drain outlet is located at the bottom. The exhaust gas, thoroughly neutralized by the alkaline spray of the Venturi 06, enters the equipment through the air inlet of the cyclone separator 07. Within the cyclone separator 07, the exhaust gas forms a rotating airflow, and under centrifugal force, the small amount of alkaline droplets carried by the exhaust gas are separated. The separated alkaline liquid is discharged from the lower drain outlet of the cyclone separator 07, while the drier exhaust gas that meets the specifications is discharged from the air outlet of the cyclone separator 07 and enters the induced draft fan 08.

[0049] The air inlet of the induced draft fan 08 receives the exhaust gas discharged from the outlet of the cyclone separator 07; after being centrifugally accelerated inside the induced draft fan 08, the exhaust gas is discharged from the exhaust outlet of the induced draft fan 08 and enters the fiberglass chimney 09, and finally achieves qualified emission into the upper atmosphere.

[0050] The air inlet of the fiberglass chimney 09 is located at the bottom, and the exhaust outlet is located at the top. Its air inlet receives the exhaust gas discharged at high speed from the exhaust outlet of the induced draft fan 08, and the tall fiberglass chimney 09 dissipates the exhaust gas into the upper atmosphere for qualified emission. ##2 Material Recovery and Recycling System Equipment and Process

[0051] The tail culvert of the slurry conveying pump 10 is connected to the bottom discharge port of the thick slurry storage tank 11, and the upper culvert pipe leads to the slurry recycling station. Its function is to: collect the titanium dioxide slurry collected by spraying from the No. 1 spray tower 02, concentrate and separate it through the cyclone thickener 12, and then send it into the thick slurry storage tank 11. The slurry, after sedimentation and concentration, is periodically transported to the slurry recycling station for recycling.

[0052] The slurry storage tank 11 is equipped with an overflow port at the top and a discharge port at the bottom. The thickened slurry separated by the cyclone thickener 12 enters the tank from the surface of the slurry storage tank 11. The slurry further settles and thickens in the slurry storage tank 11, and the supernatant returns from the overflow port to the primary spray tank 14 for circulating spraying. The slurry that has further settled and thickened is periodically transported to the slurry recovery station by the slurry transfer pump 10 for recovery.

[0053] The cyclone thickener 12 has a dilute phase outlet at the top, a material inlet along the upper circumferential tangential direction, and a thickening slurry outlet at the bottom. The mixture of titanium dioxide dust particles captured by spraying from spray tower 02 enters the equipment through the feed inlet of the cyclone thickener 12. Under the action of centrifugal separation, the mixture is separated into a dilute phase and a dense phase: the dilute phase is discharged from the dilute phase outlet at the top of the cyclone thickener 12 and returned to the primary spray tank 14 for circulating spraying; the dense phase is discharged from the thickening outlet at the bottom of the cyclone thickener 12 and enters the thick slurry storage tank 11 for further sedimentation and thickening.

[0054] The tail duct of the primary spray pump 13 is connected to the bottom discharge port of the primary spray tank 14, and the upper duct pipe is connected to the spray nozzle at the top of the No. 1 spray tower 02. Its function is to pressurize the spray liquid in the primary spray tank 14 and spray it into the No. 1 spray tower 02, on the one hand to cool the flue gas, and on the other hand to spray and capture titanium dioxide dust particles in the exhaust gas. The spray liquid that has completed the exhaust gas cooling and dust capture flows out from the bottom discharge port of the No. 1 spray tower 02 and flows through the cyclone thickener 12; the separated dilute phase is discharged from the dilute phase discharge port at the top of the cyclone thickener 12 and returns to the primary spray tank 14 for cooling and recirculation spraying; the dense phase is discharged from the thickening discharge port at the bottom of the cyclone thickener 12 and enters the thick slurry storage tank 11 for further sedimentation and thickening.

[0055] The primary spray tank 14 has an overflow port at the top and a discharge port at the bottom. It contains heat exchange coils and a stirring device to enhance heat exchange capacity. The third wash water is first evenly added to the primary spray tank 14 for spraying in spray tower 02 (No. 1). After being sprayed by spray tower 02, the spray liquid absorbs heat, causing its temperature to rise, and simultaneously captures titanium dioxide dust particles. It then flows into the cyclone thickener 12 and is separated into a dilute phase and a dense phase. The dense phase enters the slurry storage tank 11, while the dilute phase returns to the primary spray tank 14, where it is cooled by heat exchange in the coils and then used for circulating spraying.

[0056] The tail culvert of the titanium liquid transfer pump 15 is connected to the bottom discharge port of the low-ferric titanium liquid storage tank 16, and the upper culvert pipeline leads to the black section iron powder reduction station. Its function is to periodically transport the low-ferric titanium liquid, which is generated by the reduction of high-ferric titanium liquid after sulfur dioxide is captured by spraying in No. 2 spray tower 03, to the black section iron powder reduction station for complete reduction.

[0057] The low-ferric iron titanium liquid storage tank 16 is equipped with an overflow port at the top and a discharge port at the bottom. After sulfur dioxide is captured by spraying in spray tower 03, the low-ferric iron titanium liquid generated by the reduction of high-ferric iron titanium liquid overflows from the high-ferric iron titanium liquid storage tank 18 into the low-ferric iron titanium liquid storage tank 16 for storage. When the content of ferric iron ions in the titanium liquid drops to 10g / L-31g / L, the titanium liquid transfer pump 15 periodically sends the low-ferric iron titanium liquid back to the black section iron powder reduction station to achieve complete reduction.

[0058] The tail duct of the secondary spray pump 17 is connected to the bottom discharge port of the high-ferric iron titanium liquid storage tank 18, and the upper duct pipe is connected to the spray nozzle at the top of the No. 2 spray tower 03. Its function is to pressurize and spray the high-ferric iron titanium liquid in the high-ferric iron titanium liquid storage tank 18 into the No. 2 spray tower 03, dissolve and capture sulfur dioxide in the tail gas, and use sulfur dioxide to reduce ferric iron to ferrous iron; when the ferric iron ion content in the titanium liquid drops to 10g / L-31g / L, the process task at this node is completed.

[0059] The high-ferric iron titanium liquid storage tank 18 is equipped with an overflow port at the top and a discharge port at the bottom. The tank contains heat exchange coils and a stirring device to enhance heat exchange capacity. The high-ferric iron titanium liquid obtained from the acid leaching process is first evenly added to the high-ferric iron titanium liquid storage tank 18 for spraying in spray tower 03 (No. 2). After being sprayed by spray tower 03, the high-ferric iron titanium liquid dissolves and absorbs sulfur dioxide from the exhaust gas, which reduces the high-ferric iron titanium liquid to low-ferric iron titanium liquid. After the titanium liquid is circulated and sprayed three times, if the ferric iron ion content drops to 10g / L-31g / L, the titanium liquid overflows into the low-ferric iron titanium liquid storage tank 16, and is then periodically returned to the black iron powder reduction station by the titanium liquid transfer pump 15 for complete reduction.

[0060] The tail duct of the three-stage spray pump 19 is connected to the bottom discharge port of the three-stage spray tank 20, and the upper duct is connected to the spray nozzle at the top of the No. 3 spray tower 04. Its function is to pressurize the low-temperature water in the three-stage spray tank 20 and spray it into the No. 3 spray tower 04 to dissolve and capture titanium liquid droplets in the tail gas; the low-temperature water is recycled after multiple cycles of spraying and returned to the black section acid leaching process for use.

[0061] The lower part of the three-stage spray tank 20 is equipped with a discharge port. The low-temperature water (from the spraying process of the No. 3 spray tower 04) after being cooled by the three-stage air-cooling tower 21 enters the three-stage spray tank 20, and is then pressurized and sprayed into the No. 3 spray tower 04 by the three-stage spray pump 19, circulating to dissolve and capture the titanium liquid droplets carried by the tail gas from the previous titanium liquid spraying process.

[0062] The liquid inlet and outlet of the three-stage air-cooled tower 21 are both located at the bottom, and it has a built-in high-volume fan. Its function is to circulate and cool the low-temperature water used for spraying in the No. 3 spray tower 04, thereby reducing the exhaust gas temperature and reducing the water vapor carried in the exhaust gas.

[0063] The tail duct of the third-stage cooling pump 22 is connected to the bottom discharge port of the third-stage hot water tank 23, and the upper duct is connected to the liquid inlet of the third-stage air-cooled tower 21. Its function is to pressurize the low-temperature spray water in the third-stage hot water tank 23 and spray it into the third-stage air-cooled tower 21. After being cooled by forced air, it is used for circulating spraying in the No. 3 spray tower 04.

[0064] Two discharge ports are provided at the bottom of the tertiary hot water tank 23. The low-concentration water sprayed by the No. 3 spray tower 04 and the droplets collected by the electrostatic precipitator 05 flow together into the tertiary hot water tank 23. One discharge port at the bottom of the tertiary hot water tank 23 is connected to the tertiary cooling pump 22, which pressurizes the low-concentration water sprayed in the tank and sprays it into the tertiary air-cooled tower 21. After being cooled by forced air, it is supplied to the No. 3 spray tower 04 for circulation spraying. The other discharge port is connected to the desalination liquid transfer pump 24. When the titanium dioxide concentration of the desalination liquid in the tank reaches 20g / L-30g / L, the desalination liquid transfer pump 24 periodically sends the desalination liquid back to the black section acid leaching process for use.

[0065] The tail culvert of the desalination pump 24 is connected to a bottom discharge port of the tertiary hot water tank 23, and the upper culvert pipe leads to the acid leaching station in the black section. Its function is to periodically transport the titanium liquid droplets captured by the spray washing of the No. 3 spray tower 04 to the black section acid leaching station for use after multiple circulation sprays to increase the concentration.

[0066] The tail duct of the alkali spray pump 25 is connected to the bottom discharge port of the alkali spray tank 26, and the upper duct pipe is connected to the top spray nozzle of the venturi 06. Its function is to pressurize the alkali solution in the alkali spray tank 26 and spray it into the venturi 06 to neutralize the small amount of acid mist in the tail gas; the tail gas finally passes through the cyclone separator 07 to remove liquid droplets and achieve qualified discharge.

[0067] The alkaline spray tank 26 has a discharge port at the bottom and is equipped with heat exchange coils and a stirring device to enhance heat exchange capacity. Low-concentration alkaline solution from the Venturi 06 spray enters the alkaline spray tank 26, and is then pressurized and sprayed into the Venturi 06 by the alkaline spray pump 25. This circulates and dissolves acidic substances in the exhaust gas and absorbs heat from the exhaust gas, resulting in lower acid mist content and lower temperature in the exhaust gas, meeting emission standards. The circulating spray alkaline solution is heated by tap water through the coils, maintaining the temperature between 28℃ and 35℃.

[0068] Example 1

[0069] A process for reducing emissions and energy consumption of ferric iron in titanium liquid using sulfur dioxide from rotary kiln calcination tail gas includes the following steps:

[0070] (1) Titanium liquid pretreatment and supply: The titanium liquid obtained by acid hydrolysis leaching with a titanium dioxide concentration of 125g / l-132g / l, a ferric ion concentration of 16g / l-37g / l, and a temperature of 58℃-63℃ is added to the high ferric titanium liquid storage tank 18 and pressurized by the secondary spray pump 17 to carry out secondary spraying of the kiln calcination tail gas in the No. 2 spray tower 03;

[0071] After an average of three cycles of spraying, the concentration of ferric ions in the titanium liquid can be reduced by 5 g / L to 8 g / L, theoretically enabling the complete absorption and utilization of sulfur dioxide generated during rotary kiln calcination. To ensure that the temperature of the titanium liquid remains stable at 58℃-63℃ during the circulating spraying process, warm water at 50℃-55℃ is used for heat exchange through the coils inside the high-ferric iron titanium liquid storage tank 18, achieving precise temperature regulation of the titanium liquid.

[0072] (2) Multi-stage treatment of rotary kiln calcination tail gas: The rotary kiln calcination tail gas is treated by a multi-stage spray system. The first stage uses dilute acid water spraying to cool and remove dust. The rotary kiln calcination tail gas, after most of the titanium dioxide dust particles have been removed by the cyclone dust collector 01, enters the No. 1 spray tower 02 for the first stage of spraying treatment. On the one hand, the dilute acid water after the third wash is used to spray the tail gas at a temperature of 260℃-280℃, reducing the tail gas temperature to 55℃-65℃; on the other hand, the spray washing further removes the residual titanium dioxide dust particles in the tail gas, creating favorable conditions for the subsequent spraying process, and improving the recovery rate of titanium dioxide.

[0073] After the first-stage spray treatment, the titanium dioxide dust particles in the exhaust gas have been fully removed, and the temperature has dropped to 55℃-65℃. The exhaust gas then enters spray tower 03 (No. 2) for the second-stage spray. This stage uses the titanium liquid described in step (1). Two core reactions occur during the spray process: First, sulfur dioxide in the exhaust gas is dissolved and captured by the titanium liquid; second, the dissolved sulfur dioxide reacts with ferric ions in the titanium liquid in a redox reaction, reducing ferric ions to ferrous ions and oxidizing sulfur dioxide to sulfur trioxide. The sulfur trioxide dissolves in the titanium liquid to form sulfuric acid, which is then fixed in the liquid phase. When the titanium liquid completes three cycles of spraying and its internal ferric ion concentration drops to 10g / L-31g / L, the titanium liquid can be returned to the subsequent process for complete reduction using iron powder.

[0074] After the second-stage titanium liquid spraying, most of the sulfur dioxide in the exhaust gas has been captured, absorbed, and fixed, and the exhaust gas temperature is maintained at 56℃-62℃, but it still carries a small amount of titanium liquid droplets. A third-stage spraying treatment is performed on the exhaust gas using spray tower #3 (04) to recover these titanium liquid droplets and further reduce the exhaust gas temperature. This stage of spraying first uses clean water at a temperature of 23℃-28℃. The sprayed liquid then enters a circulating spraying system, where it is forcibly cooled by a three-stage air-cooled tower (21) to stabilize the temperature at 26℃-32℃. When the titanium dioxide concentration in the sprayed liquid reaches 20g / L-30g / L, the sprayed liquid is returned to the acid leaching process for reuse to improve the titanium dioxide recovery rate. The sprayed exhaust gas then enters an electrostatic precipitator (05) to remove droplets. The droplets collected by the electrostatic precipitator (05) are returned to the three-stage hot water tank (23), and the exhaust gas then enters the next stage of alkaline spraying treatment.

[0075] The exhaust gas, after being treated by the third-stage spray and electrostatic precipitator 05 to remove most of the droplets, enters the venturi 06 for the fourth-stage spray treatment. This stage of spraying uses a dilute caustic soda solution with a concentration of 5g / L-10g / L. The dilute caustic soda solution enters the circulating spray system and is cooled by heat exchange with tap water through the coils in the caustic soda spray tank 26. The sprayed exhaust gas then enters the cyclone separator 07 to remove droplets, and the removed droplets are returned to the caustic soda spray tank 26 for reuse. The exhaust gas after droplet removal is then pressurized by the induced draft fan 08 and finally discharged into the atmosphere through the fiberglass chimney 09, achieving emission standards.

[0076] (3) Subsequent treatment of titanium liquid: After the titanium liquid undergoes secondary spray treatment of the calcination tail gas in the rotary kiln, the ferric ions inside are reduced by the sulfur dioxide that is captured. When the concentration of ferric ions in the titanium liquid drops to 10 g / L-31 g / L, the titanium liquid is returned to the reduction tank in the process. Iron powder is added to the reduction tank for further reduction. To ensure that the ferric ions are completely reduced to ferrous ions, the amount of iron powder used needs to be controlled to be slightly excessive. Excessive iron powder will reduce a small amount of tetravalent titanium to ferric titanium. When the concentration of ferric titanium in the titanium liquid reaches 0.5 g / L-1.5 g / L, the titanium liquid reduction operation is completed, and then it enters the next process.

[0077] In this embodiment 1, the core of the process involves using a titanium solution with a high ferric iron content obtained through acid leaching in the secondary spray stage. This titanium solution absorbs and captures sulfur dioxide in the exhaust gas, causing a redox reaction between the sulfur dioxide and the ferric iron in the titanium solution. The sulfur dioxide is oxidized to sulfur trioxide, which dissolves in the titanium solution and is fixed as sulfuric acid. The ferric iron in the titanium solution is reduced to ferrous iron. Therefore, the iron powder consumption during subsequent iron powder reduction can be reduced by 23 kg. Based on a price of 3 yuan per kg of iron powder, this translates to a reduction of 69 yuan in iron powder cost per ton of titanium dioxide produced. Furthermore, the alkali spray is placed after the electrostatic precipitator. Not only is the sulfur dioxide in the exhaust gas fully absorbed and removed in the preceding secondary spray stage, but other acidic droplets are also thoroughly removed in the electrostatic precipitator. This significantly reduces alkali consumption, reducing alkali consumption by 35 kg per ton of titanium dioxide produced. Based on a price of 2.8 yuan per kg of caustic soda, this translates to a reduction of 98 yuan in alkali consumption cost per ton of titanium dioxide produced.

[0078] Comparative Example 1

[0079] The process employs a commonly used three-stage spraying and electrostatic precipitator for mist removal: the first stage uses a partially circulated acidic water spray after three washes; the second stage uses a circulating clean water spray combined with air cooling tower cooling; and the third stage uses a circulating dilute alkali spray combined with air cooling tower cooling. After mist removal via electrostatic precipitator, the mist is pressurized by an induced draft fan and discharged through a chimney, where it is discharged into the atmosphere in compliance with regulations. The process flow and equipment are described in [link to process details]. Figure 2 .

[0080] In Comparative Example 1, the first and second stage sprays only cool the exhaust gas and capture the dust; they do not absorb or capture sulfur dioxide. Therefore, all the sulfur dioxide in the exhaust gas is absorbed and neutralized by caustic soda in the third stage spray. On average, 38 kg of caustic soda is consumed to produce 1 ton of titanium dioxide. Based on a price of 2.8 yuan per kg of caustic soda, the cost is 106.4 yuan. Table 1 shows the comparison of raw material consumption and cost data between Example 1 and Comparative Example 1.

[0081]

[0082] The sulfur dioxide concentration in the exhaust gas of Comparative Example 1 was 82 ppm and the acid mist concentration was 40 ppm, while the corresponding indicators in Example 1 were reduced to 33 ppm and 21 ppm, respectively. The sulfur dioxide removal rate reached 60.98% and the acid mist removal rate reached 47.5%, indicating that the present invention has a significantly better removal effect on acidic pollutants in exhaust gas than traditional processes, and the exhaust gas emission quality is greatly improved, making it easier to meet stringent environmental emission standards.

[0083] In Comparative Example 1, producing 1 ton of titanium dioxide required 82 kg of iron powder, while in Example 1, only 63 kg was required, a reduction of 23 kg per ton, or 28.05%, directly reducing the procurement cost and inventory pressure of reduced iron powder. In Comparative Example 1, the caustic soda consumption per ton of titanium dioxide was 38 kg, while in Example 1 it was reduced to 3 kg, a reduction of 35 kg per ton, or 92.11%, significantly reducing the use of alkaline neutralizing agents and simultaneously reducing the generation of secondary pollutants such as alkaline slag.

[0084] In Example 1, the electricity cost for the induced draft fan was 32 yuan / ton of titanium dioxide, slightly higher than the 24.7 yuan / ton in Comparative Example 1. This increase is mainly due to the addition of titanium liquid spraying and droplet collection steps in the process of this invention, requiring the induced draft fan to provide higher negative pressure to ensure exhaust gas flow. This represents a reasonable increase in energy consumption due to process optimization. The comprehensive cost per ton of titanium dioxide in Comparative Example 1 (iron powder + caustic soda + induced draft fan electricity cost) was 389.1 yuan, while in Example 1 it was reduced to 229.4 yuan, resulting in a cost saving of 159.7 yuan per ton. Calculated for a company with an annual production of 100,000 tons of titanium dioxide, this translates to an average annual cost saving of 15.97 million yuan, demonstrating significant economic benefits.

[0085] In summary, the process of this invention far surpasses traditional processes in terms of exhaust gas purification effect, effectively reducing the concentration of sulfur dioxide and acid mist emissions, meeting the stringent requirements of current environmental protection policies for industrial exhaust gas emissions, and possessing good environmental benefits.

[0086] Although the invention results in a slight increase in the electricity cost of the induced draft fan due to process optimization, it achieves a significant reduction in overall production costs by greatly reducing the consumption of iron powder and caustic soda. The cost savings far outweigh the increase in energy consumption, demonstrating strong economic feasibility.

[0087] From the perspective of resource utilization, this invention transforms sulfur dioxide, a "pollutant" in the traditional process of rotary kiln calcination tail gas, into a "resource" of ferric iron in the reduced titanium liquid, thereby realizing the resource utilization of waste gas and reducing the consumption of iron powder in the titanium liquid reduction process, forming a virtuous cycle of treating waste with waste and reducing costs and increasing efficiency.

[0088] Although exemplary embodiments of the invention have been described and illustrated, those skilled in the art will understand that various changes and substitutions can be made thereto without departing from the spirit of the invention. Furthermore, many modifications can be made to adapt specific situations to the doctrine of the invention without departing from the central concepts of the invention described herein. Therefore, the invention is not limited to the specific embodiments disclosed herein, but may include all embodiments and equivalents that fall within the scope of the invention.

[0089] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0090] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A device for reducing emissions and energy consumption by using sulfur dioxide from rotary kiln calcination tail gas to reduce trivalent iron in liquid titanium, characterized in that, The system includes a cyclone dust collector, spray tower #1, spray tower #2, spray tower #3, an electrostatic precipitator, a venturi separator, a cyclone separator, an induced draft fan, and a fiberglass chimney. The cyclone dust collector's inlet is flush with the rotary kiln exhaust outlet, and it has an outlet at the top and a discharge port at the bottom. Spray tower #1's bottom inlet connects to the cyclone dust collector's outlet, and it has nozzles and an exhaust port at the top. Spray tower #2's bottom inlet connects to spray tower #1's exhaust port, and it has titanium liquid nozzles and an exhaust port at the top. Spray tower #3's bottom inlet connects to spray tower #2's exhaust port. The top is equipped with a low-temperature water nozzle and an exhaust port; the bottom air inlet of the electrostatic precipitator is connected to the exhaust port of the No. 3 spray tower, and the top is equipped with an air outlet; the top of the venturi is equipped with an air inlet and a low-temperature alkaline nozzle, the top air inlet of the venturi is connected to the top air outlet of the electrostatic precipitator, and the bottom is equipped with an air outlet; the air inlet of the cyclone separator is located tangentially to the upper circumference and is connected to the bottom air outlet of the venturi, the air outlet is located at the top, and the liquid discharge port is located at the bottom; the air inlet of the induced draft fan is connected to the air outlet of the cyclone separator; the air inlet of the fiberglass chimney is connected to the air outlet of the induced draft fan.

2. The emission reduction and energy saving device for reducing trivalent iron in titanium liquid using sulfur dioxide from rotary kiln calcination tail gas according to claim 1, characterized in that, It also includes a slurry conveying pump, a thick slurry storage tank, a cyclone thickener, a primary spray pump, and a primary spray tank. The primary spray tank is connected to the nozzle at the top of the No. 1 spray tower via the primary spray pump. The discharge port at the bottom of the No. 1 spray tower is connected to the tangential material inlet at the top of the cyclone thickener. The dilute phase discharge port at the top of the cyclone thickener is connected to the primary spray tank, and the thickening discharge port at the bottom is connected to the thick slurry storage tank. The discharge port at the bottom of the thick slurry storage tank is connected to the slurry conveying pump. The cyclone thickener separates the spray liquid containing titanium dioxide dust particles discharged from the No. 1 spray tower into a dilute phase and a dense phase through a rotary centrifugal separator. The dilute phase is returned to the primary spray tank for recycling, while the dense phase enters the thick slurry storage tank for sedimentation and thickening. The slurry conveying pump transports the sedimented and thickened slurry from the thick slurry storage tank to the slurry recovery station. The primary spray tank is equipped with a heat exchange coil and a stirring device.

3. The emission reduction and energy saving device for reducing trivalent iron in titanium liquid using sulfur dioxide from rotary kiln calcination tail gas according to claim 1, characterized in that, It also includes a titanium liquid transfer pump, a low-ferric titanium liquid storage tank, a secondary spray pump, and a high-ferric titanium liquid storage tank; the high-ferric titanium liquid storage tank is connected to the titanium liquid nozzle at the top of the No. 2 spray tower via the secondary spray pump, the discharge port at the bottom of the No. 2 spray tower is connected to the low-ferric titanium liquid storage tank, and the discharge port at the bottom of the low-ferric titanium liquid storage tank is connected to the titanium liquid transfer pump; both the high-ferric titanium liquid storage tank and the low-ferric titanium liquid storage tank are equipped with overflow ports at the top and discharge ports at the bottom; the high-ferric titanium liquid storage tank is equipped with a heat exchange coil and a stirring device.

4. The emission reduction and energy saving device for reducing trivalent iron in titanium liquid using sulfur dioxide from rotary kiln calcination tail gas according to claim 1, characterized in that, It also includes a three-stage spray pump, a three-stage spray tank, a three-stage air-cooled tower, a three-stage cooling pump, a three-stage hot water tank, and a desalination liquid transfer pump; the three-stage spray tank is connected to the low-temperature water nozzle of the No. 3 spray tower through the three-stage spray pump, the bottom discharge port of the No. 3 spray tower is connected to the three-stage hot water tank, the three-stage hot water tank is connected to the bottom inlet of the three-stage air-cooled tower through the three-stage cooling pump, and the bottom outlet of the three-stage air-cooled tower is connected to the three-stage spray tank; the lower part of the three-stage hot water tank is provided with two discharge ports, one of which is connected to the three-stage cooling pump and the other is connected to the desalination liquid transfer pump.

5. The emission reduction and energy saving device for reducing trivalent iron in titanium liquid using sulfur dioxide from rotary kiln calcination tail gas according to claim 1, characterized in that, It also includes an alkali spray tank and an alkali spray pump; the alkali spray tank is connected to the low-alkaline solution nozzle of the Venturi via the alkali spray pump, and the bottom discharge port of the Venturi is connected to the alkali spray tank; the alkali spray tank is provided with a discharge port at the bottom and is equipped with a heat exchange coil and a stirring device inside.

6. A process for reducing emissions and energy consumption of ferric iron in titanium liquid using sulfur dioxide reduction of rotary kiln calcination tail gas according to any one of claims 1-5, characterized in that, Includes the following steps: (1) Titanium liquid pretreatment and supply: The titanium liquid obtained by acid hydrolysis leaching with a titanium dioxide concentration of 125g / l-132g / l, a ferric ion concentration of 16g / l-37g / l, and a temperature of 58℃-63℃ is added to the high ferric titanium liquid storage tank and pressurized by a secondary spray pump in the No. 2 spray tower for secondary spraying of the kiln calcination tail gas; (2) Multi-stage treatment of rotary kiln calcination tail gas: The rotary kiln calcination tail gas is treated by a multi-stage spray system. The first stage uses dilute acid water spray to cool down and remove dust. The second stage uses the titanium liquid spray to absorb sulfur dioxide and reduce ferric iron. The third stage uses clean water spray to recover titanium liquid droplets. The fourth stage uses dilute caustic soda solution spray to neutralize residual acidic substances. (3) Subsequent treatment of titanium liquid: When the titanium liquid is circulated in the secondary spray until the concentration of ferric ions drops from the initial 16g / l-37g / l to 10g / l-31g / l, the titanium liquid is returned to the reduction tank and iron powder is added for complete reduction.

7. The emission reduction and energy saving process for reducing trivalent iron in titanium liquid using sulfur dioxide from rotary kiln calcination tail gas according to claim 6, characterized in that, During the secondary spraying process, the titanium liquid is kept at a temperature of 58℃-63℃ by using 50℃-55℃ warm water through coil heat exchange. After multiple cycles of spraying, the concentration of ferric ions in the titanium liquid is reduced by 5g / l-8g / l, thus achieving complete absorption and utilization of sulfur dioxide generated during rotary kiln calcination.

8. The emission reduction and energy saving process for reducing trivalent iron in titanium liquid using sulfur dioxide from rotary kiln calcination tail gas according to claim 6, characterized in that, During the treatment of the tail gas from the rotary kiln calcination, the first-stage spray reduces the tail gas temperature from 260℃-280℃ to 55℃-65℃, the second-stage spray keeps the tail gas temperature at 56℃-62℃, and the third-stage spray uses clean water at 23℃-28℃ and maintains the spray liquid temperature at 26℃-32℃.

9. The emission reduction and energy saving process for reducing trivalent iron in titanium liquid using sulfur dioxide from rotary kiln calcination tail gas according to claim 6, characterized in that, After the titanium liquid undergoes a two-stage spray reduction process, when the concentration of ferric ions drops to 10 g / l-31 g / l, it is returned to the reduction tank. Excess iron powder is then used for complete reduction, partially reducing tetravalent titanium to trivalent titanium. The reduction operation is completed when the concentration of trivalent titanium reaches 0.5 g / l-1.5 g / l.

10. The emission reduction and energy saving process for reducing trivalent iron in titanium liquid using sulfur dioxide from rotary kiln calcination tail gas according to claim 6, characterized in that, The clean water used in the third-stage spray is recycled. When the concentration of titanium dioxide in it reaches 20g / l-30g / l, it is returned to the acid leaching process. The fourth-stage spray uses a dilute caustic soda solution with a concentration of 5g / l-10g / l, and uses tap water to maintain the temperature of the caustic soda solution at 28℃-35℃ through coil heat exchange.

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