Ozone oxidation and air blow-out method-based brine iodine extraction system and process method

Abstract

The invention belongs to the technical field of comprehensive utilization of brine resources, and particularly relates to a brine iodine extraction system and process method based on an ozone oxidation and air blow-out method. The brine iodine extraction system comprises a brine pretreatment unit, an acidification and ozone oxidation unit, a multi-stage air stripping unit, an absorption and recycling unit and a tail gas purification unit, the multi-stage stripping unit comprises N stages of stripping towers which are connected in series stage by stage, each stage of stripping tower from the first-stage stripping tower to the N-stage stripping tower adopts a strategy of ozone segmented addition and temperature gradient regulation and control, and the gas-liquid ratio from the first-stage stripping tower to the N-stage stripping tower is reduced stage by stage in each stage of stripping tower; the absorption and recycling unit comprises a multi-stage absorption unit and an absorbent regeneration unit, the multi-stage absorption unit comprises M stages of absorption towers which are connected in series stage by stage, and the absorbent regeneration unit comprises an electrolytic regeneration system. The method is suitable for high-salt and low-iodine brine, is particularly suitable for industrial iodine extraction scenes of low-iodine-concentration and high-salinity brine, and integrates high efficiency, environmental protection property and economical efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of comprehensive utilization of brine resources, and particularly relates to a brine iodine extraction system and process method based on ozone oxidation and air stripping method. Background Art

[0002] Iodine, as an important strategic resource, has indispensable applications in many fields such as medicine, electronics, chemical industry, and agriculture. Extracting iodine from brine is one of the important ways to obtain iodine resources. However, there are many problems to be solved urgently in the existing brine iodine extraction technologies at present. Problem 1: Toxicity problem of oxidants Chlorine method: In traditional iodine extraction processes, chlorine ( ) is often used as an oxidant. However, chlorine has strong toxicity and corrosiveness, and there is a great risk of leakage during use. Once leakage occurs, it will pose a serious threat to the health of operators and the environment. In addition, during the process of chlorine oxidizing iodide ions, iodine monochloride ( ) will be by-produced. Iodine monochloride has special properties and requires additional treatment steps to achieve effective separation, which undoubtedly increases the complexity and cost of the process. At the same time, the tail gas contains hydrogen chloride ( ) gas, which needs to be neutralized, further increasing the treatment cost and operation difficulty. Hydrogen peroxide method: When hydrogen peroxide ( ) is used as an oxidant, its oxidation efficiency is strictly limited by the pH value of the solution. Generally, the pH value of the solution needs to be adjusted to a strong acidic condition of less than 2 to ensure a good oxidation effect. However, in actual operation, adjusting the pH value not only increases the usage amount and cost of chemical reagents, but also reduces the self-stability of hydrogen peroxide in an acidic environment, and it is easy to undergo a decomposition reaction, resulting in waste of the reagent and an increase in the cost of iodine extraction. Nitric acid method: When nitric acid ( ) is used as an oxidant, although its oxidation ability is strong, it will introduce nitrate ions ( ), which will pollute the subsequent iodine products and wastewater. Treating wastewater containing a large amount of nitrate ions requires complex processes and equipment, with high costs, and it is difficult to achieve complete purification, posing a potential hazard to the environment.

[0003] Problem 2: Low stripping efficiency Iodine molecules ( ) has a certain solubility in brine, about 0.3 g / L. When the traditional air stripping method is used to treat iodine-containing brine, due to the solubility of iodine in brine, in order to blow out the iodine element as much as possible, an extremely high gas-liquid ratio is required, usually greater than 200:1. Such a high gas-liquid ratio means that a large amount of air is consumed, which not only increases energy consumption, but also places extremely high performance requirements on equipment such as fans, resulting in a substantial increase in equipment investment. At the same time, a high gas-liquid ratio will also make the blowing tower bulky and increase the floor space, further increasing the overall operating costs. Problem 3: Absorbent limitations In the absorption process of iodine, sulfur dioxide ( ) Reduction method to absorb iodine ( However, this method has obvious limitations. During the absorption process, hydroiodic acid ( ), hydroiodic acid is highly corrosive and has extremely high requirements on equipment materials. It is necessary to use special corrosion-resistant materials to manufacture equipment, which greatly increases the equipment cost. In addition, unreacted sulfur dioxide often remains in the tail gas, and the tail gas needs to be specially treated to prevent sulfur dioxide emissions from polluting the environment, which further increases the processing cost and process complexity. With the continuous development and utilization of brine resources, the demand for efficient, environmentally friendly and low-cost brine iodine extraction technology is becoming increasingly urgent. Therefore, the development of a new type of efficient brine iodine extraction system and process based on ozone oxidation and air blowing has important practical significance and broad application prospects. Summary of the invention

[0004] In order to solve the problems existing in the above-mentioned prior art, the present invention provides a brine iodine extraction system and process method based on ozone oxidation and air blowing method. The present invention is particularly suitable for industrial iodine extraction scenarios of low iodine concentration (50-200 mg / L) and high salinity brine (such as oilfield water and salt lake brine). Through the multi-stage oxidation-stripping-absorption coupling design, the iodine recovery rate ≥ 95%, the ozone utilization rate ≥ 85%, and the tail gas emission meet the standards, which are both efficient, environmentally friendly and economical.

[0005] The present invention adopts the following technical solutions: The brine iodine extraction system based on ozone oxidation and air blowing method includes a brine pretreatment unit, an acidification and ozone oxidation unit, a multi-stage stripping unit, an absorption and resource recovery unit, and an exhaust gas purification unit, wherein: A multi-stage stripping unit, comprising N-stage blow-out towers connected in series, N being greater than or equal to 3, each blow-out tower from the first stage to the N stage adopts a strategy of ozone segmentation addition and temperature gradient control, and the gas-liquid ratio in each blow-out tower from the first stage to the N stage decreases step by step; An absorption and resource utilization unit, which includes a multi-stage absorption unit and an absorbent regeneration unit. The multi-stage absorption unit includes M-stage absorption towers connected in series step by step, where M is greater than or equal to 2. The absorption liquid of the first-stage absorption tower is solution, and the absorption liquid of the M-stage absorption tower is NaOH solution. The absorbent regeneration unit includes an electrolytic regeneration system for regenerating the solution generated by the multi-stage absorption unit back into solution.

[0006] In the above technical solution, the brine pretreatment unit includes a sedimentation tank and a filtering device.

[0007] In the above technical solution, the acidification and ozone oxidation unit includes an acidification reaction tank, an ozone generator, and a cyclone mixer. In the cyclone mixer, ozone gas contacts the brine in a countercurrent manner.

[0008] In the above technical solution, the multi-stage stripping unit includes three-stage stripping towers connected in series step by step. From the first-stage stripping tower, the second-stage stripping tower to the third-stage stripping tower, ozone is added in three sections. From the first-stage stripping tower, the second-stage stripping tower to the third-stage stripping tower, the temperature decreases in a gradient manner in each stripping tower, and the gas-liquid ratio decreases step by step in each stripping tower.

[0009] In the above technical solution, the ozone dosage of the first-stage stripping tower accounts for 70% of the total amount, the ozone dosage of the second-stage stripping tower accounts for 20% of the total amount, and the ozone dosage of the third-stage stripping tower accounts for 10% of the total amount; each stripping tower is equipped with a microporous aerator and a gradient temperature control system. The gas-liquid ratio of the first-stage stripping tower is 80:1 and the temperature is 40 °C, and the gas-liquid ratio of the third-stage stripping tower is 20:1 and the temperature is 25 °C.

[0010] In the above technical solution, the multi-stage absorption unit is a two-stage absorption unit. The two-stage absorption unit includes a first-stage absorption tower with an absorption liquid of solution and a second-stage absorption tower with an absorption liquid of NaOH solution. The absorbent regeneration unit includes an electrolytic regeneration system for regenerating the solution generated by the first-stage absorption tower back into solution.

[0011] In the above technical solution, the absorption liquid in the first-stage absorption tower is a solution with a spraying concentration of 10%, and the pH value of the solution is controlled at 8-9; the absorption liquid in the second-stage absorption tower is a NaOH solution with a spraying concentration of 5%.

[0012] In the above technical solution, the electrolytic regeneration system includes an electrolytic cell for electrolytically regenerating into , and the electrolytic current density is 150-250 A / m².

[0013] In the above technical solution, the tail gas purification unit includes an activated carbon adsorption-thermal desorption tower and an alkaline solution scrubbing tower. The desorption temperature of the activated carbon adsorption-thermal desorption tower is 100-150°C, and the recovered ozone and iodine are recycled to the blowing tower.

[0014] The second object of the present invention is to provide a process for extracting iodine from brine based on ozone oxidation and air blowing method, which includes the following steps: S1. The iodine-containing brine is preliminarily pretreated through a brine pretreatment unit to remove suspended solids, impurities and some interfering examples in the brine; S2. The iodide ions in the brine are oxidized to iodine by an acidification and ozone oxidation unit; S3. The iodine in the oxidized brine is blown out through a multi-stage stripping unit, wherein: in each stage of the multi-stage stripping unit, ozone is added in segments, the temperature gradient is regulated, and the gas-liquid ratio is gradually optimized; S4. The iodine in the iodine-containing air is absorbed through an absorption and resource utilization unit, and the recycling of the absorption liquid is realized; S5. The generated tail gas is purified through a tail gas purification unit, and the unreacted ozone and iodine are recycled to the multi-stage stripping unit.

[0015] Combining all the above technical solutions, the advantages and positive effects of the present invention are as follows: By means of technologies such as ozone addition in segments, gradient temperature-controlled stripping, recycling of absorbent regeneration, and recycling of tail gas ozone, through a multi-stage oxidation-stripping-absorption coupling design, an iodine recovery rate of ≥95%, an ozone utilization rate of ≥85%, and a 40% reduction in operating costs are achieved, and high-purity by-products can be resourcefully utilized. This system is suitable for high-salt and low-iodine brines, especially suitable for industrial iodine extraction scenarios with low iodine concentration (50-200 mg / L) and high salinity brines (such as oilfield water, salt lake brine), integrating high efficiency, environmental protection and economy.

[0016] In addition, as the creative auxiliary evidence of the present invention, it is also reflected in the following important aspects: 1. The expected benefits and commercial value after the transformation of the technical solution of the present invention are as follows: ①. Direct economic benefits: Improvement of iodine recovery rate: The iodine recovery rate is increased from 80-85% of the traditional process to ≥95%. Calculated based on an annual output of 1000 tons of iodine, the iodine output can be increased by 100-150 tons, and the annual income can be increased by about 50-75 million yuan (calculated at the market price of iodine of 500,000 yuan / ton).

[0017] Cost reduction: The operating cost is reduced from 18,000 yuan / ton of iodine to 11,000 yuan / ton, and the annual cost savings is 7 million yuan (calculated based on an annual output of 1000 tons).

[0018] By - product value - added: The by - product (purity ≥ 99%) can be sold to the disinfection and electronics industries, with an annual income increase of about 6 million yuan (calculated based on the market price of 15,000 yuan / ton and 0.8 tons of by - product iodine per ton of iodine).

[0019] ②. The technical solution of the present invention is aimed at brines with low iodine (50 - 200 mg / L) and high salt (TDS ≤ 250 g / L), and can be extended to resources such as oil - field water and salt - lake brines, covering more than 80% of the iodine extraction scenarios from brines in China.

[0020] 2. The present invention realizes the efficient iodine extraction from high - salt and low - iodine brines: The treatment efficiency of traditional technologies for brines with TDS > 200 g / L drops sharply. The present invention realizes the efficient extraction of iodine from high - salt brines (recovery rate ≥ 95%) for the first time through gradient temperature - controlled stripping (40°C → 25°C) and micro - bubble aeration technology.

[0021] 3. The technical solution of the present invention also solves the following technical problems: ①. The contradiction between iodine recovery efficiency and environmental protection: Traditional problem: The chlorine method has a relatively high iodine recovery rate but serious pollution, and the hydrogen peroxide method is environmentally friendly but has low efficiency (strong pH - dependence).

[0022] Breakthrough of the present invention: Adopting ozone oxidation (no secondary pollution) combined with absorbent regeneration ( electrolytic cycle) to achieve the dual goals of high efficiency (recovery rate ≥ 95%) and environmental protection (zero wastewater discharge).

[0023] ②. The bottleneck problem of high - salt brine treatment: Traditional problem: High salinity leads to a decrease in the activity of iodide ions, and the stripping efficiency is less than 50%.

[0024] Breakthrough of the present invention: Through micro - bubble aeration (the gas - liquid contact area is increased by 3 times) and gradient temperature control (inhibiting salt crystallization), the stripping efficiency is increased to 98%, overcoming the mass transfer limitation in a high - salt environment.

[0025] ③. The problem of uneconomical iodine extraction from high - salt brines: Traditional problem: The treatment of high - salt brines requires high pretreatment costs (such as electrodialysis desalination), and the economy is poor.

[0026] Breakthrough of the present invention: Directly treat high - salt brines (TDS ≤ 250 g / L). Through the reuse of mother liquor (the reuse rate of NaCl / NaOH is 100%) and the reuse of ozone (the utilization rate ≥ 85%), the cost per ton of iodine is reduced to 11,000 yuan, proving the feasibility of economical iodine extraction in a high - salt environment.

[0027] ④. The cost problem of ozone oxidation: Traditional problem: High energy consumption of ozone generators (≥8 kWh / kg ), making large-scale application difficult.

[0028] Breakthrough of the present invention: Using dielectric barrier discharge (DBD) technology (energy consumption ≤6 kWh / kg ), combined with a segmented dosing strategy (total amount reduced by 40%), the comprehensive ozone cost is reduced by 50% compared with the traditional chlorine method. Description of the Drawings

[0029] The drawings herein are incorporated into and constitute a part of this specification, showing embodiments consistent with the present disclosure, and are used together with the specification to explain the principles of the present disclosure; Figure 1 is the system flow chart of the iodine extraction system from brine based on ozone oxidation and air stripping method in the present invention. Detailed Description of the Invention

[0030] To make the above objects, features and advantages of the present invention more obvious and understandable, the following detailed description of the specific embodiments of the present invention is provided with reference to the drawings. Many specific details are set forth in the following description to fully understand the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0031] The following further details the present invention with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. Embodiment

[0032] The iodine extraction system from brine based on ozone oxidation and air stripping method includes a brine pretreatment unit, an acidification and ozone oxidation unit, a multi-stage stripping unit, an absorption and resource utilization unit (including a two-stage absorption unit and an absorbent regeneration unit), and a tail gas purification unit, wherein: Brine pretreatment unit: This unit is mainly used for the preliminary treatment of iodine-containing brine to remove suspended solids, impurities and some interfering ions in the brine, creating good conditions for subsequent iodine extraction operations. The brine pretreatment unit includes a sedimentation tank and a filtration device.

[0033] Sedimentation tank: The iodine-containing brine first enters the sedimentation tank, and through natural sedimentation, the larger particulate suspended solids in the brine settle to the bottom of the tank. An appropriate amount of flocculant, such as polyacrylamide (PAM), can be added to the sedimentation tank to accelerate the sedimentation process of suspended solids. The flocculant aggregates fine particles into larger flocs through adsorption bridging, thereby improving the sedimentation efficiency. Filtration device: The brine after preliminary treatment in the sedimentation tank enters the filtration device, and the filtration device can adopt methods such as sand filtration, activated carbon filtration or membrane filtration. Sand filtration can remove fine particle impurities in the brine, activated carbon filtration can further adsorb organic substances and some heavy metal ions in the brine, and membrane filtration such as ultrafiltration membrane or nanofiltration membrane can intercept colloidal particles and macromolecular substances in the brine, ensuring that the brine entering the subsequent unit is clear and has a low impurity content. Acidification and ozone oxidation unit: This unit is the key part of the whole system and is responsible for oxidizing iodide ions in the brine into iodine. The acidification and ozone oxidation unit includes an acidification reaction tank, an ozone generator and a vortex mixer.

[0034] Acidification reaction tank: It is made of corrosion-resistant materials such as titanium alloy / PP materials. An online pH monitoring and automatic acid addition system is equipped in the tank, which can accurately adjust the pH value of the brine to 1.5 - 2.5, providing a suitable acidic environment for the subsequent ozone oxidation reaction. Ozone generator: Using dielectric barrier discharge (DBD) technology, it can generate ozone gas with a concentration of 100 - 150 mg / L. According to the content of iodide ions in the brine, accurately control the ozone dosage at 0.5 - 1.2 kg / kg to achieve efficient oxidation. Vortex mixer: Ozone gas and brine contact countercurrently in the vortex mixer, and the contact residence time is 10 - 15 seconds. Under this efficient mixing method, the oxidation efficiency can reach ≥98%, ensuring that iodide ions are fully oxidized into iodine. The chemical reaction equation is: .

[0035] Multi-stage stripping unit: This unit uses the air stripping method to strip iodine from the oxidized brine, realizing the preliminary separation of iodine and brine. Taking this implementation as an example, the multi-stage stripping unit adopts a series design of three towers, and a unique structure is set in each tower. Ozone is added in three stages, with the dosage in the first tower accounting for 70% of the total amount, the second tower accounting for 20%, and the third tower accounting for 30%. Each tower is equipped with a microporous aerator and a gradient temperature control system. The gas-liquid ratio of the first tower is 80:1 and the temperature is 40°C, and the gas-liquid ratio of the third tower is 20:1 and the temperature is 25°C.

[0036] Microporous aerator: The pore diameter is 10 - 20μm, and it can generate tiny bubbles with a diameter of 0.5 - 1mm. The gas-liquid ratio gradually decreases in each tower, from 80:1 in the first tower to 20:1 in the third tower. This design can effectively reduce energy consumption while ensuring the stripping effect. Gradient temperature control system: The temperature of the first tower is controlled at 40°C, and a higher temperature is conducive to promoting volatilization; the temperature of the third tower is controlled at 25°C, and a lower temperature can reduce the entrainment of water vapor and improve the purity of the stripped iodine.

[0037] Absorption and resource recovery unit: This unit is used to absorb iodine in iodine-containing air and realize the recycling of resources. Taking this embodiment as an example, the absorption and resource recovery unit includes a two-stage absorption tower and an electrolytic regeneration system.

[0038] Primary absorption tower: Spray a solution with a concentration of 10%, and control the pH value of the solution at 8-9. In this tower, iodine reacts with the solution to generate and, and the chemical reaction equation is: solution, and the pH value of the solution is controlled at 8-9. In this tower, iodine reacts with the solution to generate and , and the chemical reaction equation is: . Secondary absorption tower: Spray 5% NaOH solution, which is mainly used to capture residual I2 and by-product, which can be used as a disinfectant, realizing the effective utilization of resources. , which can be used as a disinfectant, realizing the effective utilization of resources. Electrolytic regeneration system: It includes an electrolytic cell. Pass the solution generated by the primary absorption tower through the electrolytic regeneration system to regenerate the solution for recycling, further reducing costs. The electrolytic current density is controlled at 150-250 A / m². Tail gas purification unit: This unit purifies the tail gas generated by the system to ensure up-to-standard discharge. The activated carbon adsorption-thermal desorption technology is adopted, the desorption temperature is 100-150 °C, and the recovered ozone is reused in the stripping tower. The tail gas purification unit includes an activated carbon adsorption tower and an alkali solution scrubbing tower. solution through the electrolytic regeneration system to regenerate the solution for recycling, further reducing costs. The electrolytic current density is controlled at 150-250 A / m². Tail gas purification unit: This unit purifies the tail gas generated by the system to ensure up-to-standard discharge. The activated carbon adsorption-thermal desorption technology is adopted, the desorption temperature is 100-150 °C, and the recovered ozone is reused in the stripping tower. The tail gas purification unit includes an activated carbon adsorption tower and an alkali solution scrubbing tower.

[0039] Activated carbon adsorption tower: Used to adsorb unreacted and trace, with a decomposition rate of ≥99%, effectively removing harmful components in the tail gas. and trace , with a decomposition rate of ≥99%, effectively removing harmful components in the tail gas. Alkali solution scrubbing tower: Use 10% NaOH solution to neutralize acidic gases that may exist in the tail gas, such as (if nitrate is contained in the raw material brine), to avoid environmental pollution.

[0040] The iodine extraction system from brine based on ozone oxidation and air stripping method in this embodiment applies the following innovative technologies: 1. Apply ozone-gradient temperature control synergistic oxidation technology Ozone is added in segments: During the oxidation process, an ozone addition strategy in segments is adopted. 70% of the ozone is added to the primary tower, and its strong oxidizing property is used to quickly oxidize most of the iodide ions into iodine; 10% of the ozone is added to the tertiary tower for deep oxidation to ensure the full conversion of iodide ions, while avoiding the waste of excessive ozone and effectively reducing the ozone usage cost. Temperature gradient regulation: Through precise temperature gradient regulation, in the high-temperature section (such as 35 - 40 °C), it promotes the oxidation reaction of iodide ions ( ), to iodine molecules ( ), accelerating the reaction rate; in the low-temperature section (such as 20 - 25 °C), it inhibits the disproportionation reaction of iodine molecules ( ), reducing iodine loss, thereby improving the iodine extraction rate and product yield. 2. Application of microbubble - multi-stage countercurrent stripping technology Micro-aerator: In the stripping tower, a micro-aerator is used to generate microbubbles in the sub-millimeter range. Compared with traditional aeration methods, the gas-liquid contact area is increased by 3 times, greatly enhancing the gas-liquid mass transfer effect, making the stripping efficiency 40% higher than that of traditional aeration, effectively improving the stripping efficiency of iodine molecules from brine. Gradual optimization of gas-liquid ratio: A gas-liquid separator is set between stages of the multi-stage stripping tower, and the gas volume is dynamically adjusted according to the stripping conditions at each stage. Through this method of gradually optimizing the gas-liquid ratio, the comprehensive energy consumption is reduced by 25%, significantly reducing energy consumption while ensuring the stripping effect. 3. Creation of an absorbent recycling and regeneration system Electrolytic regeneration of sodium thiosulfate: For sodium thiosulfate in the absorbent solution, an electrolytic regeneration technology is adopted. Its electrolytic reaction is: , and the regeneration efficiency is ≥90%. Through this technology, the efficient recycling of the absorbent is achieved, the chemical agent cost is reduced by 70%, significantly reducing the production cost. By-product High-value utilization: For the by-products generated during the absorption process , through crystallization separation technology, a product with a purity of up to 99% can be obtained. This not only realizes the effective utilization of resources, but also expands the industrial chain and increases the product added value. 4. Application of tail gas ozone recycling technology Activated carbon is used to adsorb ozone in the tail gas, and then through thermal desorption (120 °C), the adsorbed ozone is desorbed and recycled to the stripping tower. Through this technology, the comprehensive ozone utilization rate is ≥85%, further improving the ozone usage efficiency and reducing the operating cost.

[0041] Comparing the iodine extraction process from brine using the ozone oxidation and air stripping method with the traditional process, the index data are shown in the following table: The iodine extraction system from brine based on ozone oxidation and air stripping method utilizes technologies such as segmented ozone dosing, gradient temperature-controlled stripping, absorbent recycling and regeneration, and tail gas ozone reuse. Through multi-stage oxidation-stripping-absorption coupling design, it achieves an iodine recovery rate of ≥95%, an ozone utilization rate of ≥85%, a 40% reduction in operating costs, and the by-product high-purity NaIO3 can be resourcefully utilized. This system is suitable for high-salt and low-iodine brines, especially applicable to the industrial iodine extraction scenarios of low-iodine concentration (50 - 200 mg / L) and high-salinity brines (such as oilfield water, salt lake brine), integrating high efficiency, environmental protection and economy.

[0042] Application example: Iodine extraction from a certain oilfield brine ( =150 mg / L) Pretreatment: The brine is filtered through sand to remove suspended solids, and the pH is adjusted to 2.0 (HCl dosage 1.2 kg / m³).

[0043] Ozone oxidation: Ozone is dosed in three segments (0.8 kg / m³ in the first stage, 0.3 kg / m³ in the second stage, 0.1 kg / m³ in the third stage), with a total dosage of 1.2 kg / m³. The detected I2 concentration after oxidation is 142 mg / L, and the conversion rate is 94.7%.

[0044] Stripping operation: First stage tower: gas-liquid ratio 80:1, temperature 40°C, stripping efficiency 65%; second stage tower: gas-liquid ratio 50:1, temperature 30°C, stripping efficiency 25%; third stage tower: gas-liquid ratio 20:1, temperature 25°C, stripping efficiency 8%; total stripping efficiency 98%, tail gas I2 concentration 2800 ppm.

[0045] Absorption and regeneration: First stage absorption tower: 10% solution, absorption rate 99.2%, producing solution (containing 12.5 g / L); electrolytic regeneration: current density 200 A / m², regeneration rate 92%.

[0046] Tail gas treatment: The tail gas after activated carbon adsorption concentration ≤0.1 ppm, ≤5 mg / m³.

[0047] Results: Total iodine recovery rate 95.3%, cost per ton of iodine 10,500 yuan, by-product 0.8 tons / ton .

[0048] The above are only the preferred embodiments of the present invention. It should be understood that the described embodiments are part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention. The present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications, and environments. Changes and modifications made by those skilled in the art without departing from the spirit and scope of the present invention shall fall within the scope of protection of the appended claims of the present invention.

Claims

1. An iodine extraction system from bittern based on ozone oxidation and air stripping method, characterized in that: It includes brine pretreatment unit, acidification and ozone oxidation unit, multi-stage stripping unit, absorption and resource recovery unit and tail gas purification unit, among which: A multi-stage stripping unit, comprising N-stage blow-out towers connected in series, N being greater than or equal to 3, each blow-out tower from the first stage to the N stage adopts a strategy of ozone segmentation addition and temperature gradient control, and the gas-liquid ratio in each blow-out tower from the first stage to the N stage decreases step by step; Absorption and resource recovery unit, which includes a multi-stage absorption unit and an absorbent regeneration unit. The multi-stage absorption unit includes M absorption towers connected in series step by step, where M is greater than or equal to 2. The absorbent solution of the first-stage absorption tower is solution, and the absorbent solution of the M-th stage absorption tower is NaOH solution. The absorbent regeneration unit includes an electrolytic regeneration system for regenerating the solution into solution.

2. The iodine extraction system from bittern based on ozone oxidation and air stripping method according to claim 1, characterized in that: The brine pretreatment unit comprises a sedimentation tank and a filtering device.

3. The iodine extraction system from bittern based on ozone oxidation and air stripping method according to claim 1, wherein: The acidification and ozone oxidation unit comprises an acidification reaction tank, an ozone generator and a cyclone mixer, in which ozone gas is in countercurrent contact with brine.

4. The iodine extraction system from bittern based on ozone oxidation and air stripping method according to claim 1, characterized in that: The multi-stage stripping unit includes three-stage blowing towers connected in series step by step. Ozone is added in three stages from the first-stage blowing tower, the second-stage blowing tower to the third-stage blowing tower. The temperature in each stage of the blowing tower decreases gradually from the first-stage blowing tower, the second-stage blowing tower to the third-stage blowing tower. The gas-liquid ratio in each stage of the blowing tower decreases step by step from the first-stage blowing tower, the second-stage blowing tower to the third-stage blowing tower.

5. The iodine extraction system from bittern based on ozone oxidation and air stripping method according to claim 4, characterized in that: The ozone dosage of the first-stage blowing tower accounts for 70% of the total, the ozone dosage of the second-stage blowing tower accounts for 20% of the total, and the ozone dosage of the third-stage blowing tower accounts for 10% of the total; each stage of the blowing tower is equipped with a microporous aerator and a gradient temperature control system, the first-stage blowing tower has a gas-liquid ratio of 80:1 and a temperature of 40°C, and the third-stage blowing tower has a gas-liquid ratio of 20:1 and a temperature of 25°C.

6. The iodine extraction system from bittern based on ozone oxidation and air stripping method according to claim 1, wherein: The multi-stage absorption unit is a secondary absorption unit, and the secondary absorption unit includes a primary absorption tower with an absorption liquid of solution and a secondary absorption tower with an absorption liquid of NaOH solution. The absorbent regeneration unit includes electrolytic regeneration of the solution generated by the primary absorption tower to regenerate solution system.

7. The iodine extraction system from bittern based on ozone oxidation and air stripping method according to claim 6, wherein: The absorbent liquid in the primary absorption tower is a solution with a spraying concentration of 10% and the pH value of the solution is controlled at 8-9; the absorbent liquid in the secondary absorption tower is a NaOH solution with a spraying concentration of 5%.

8. The iodine extraction system from bittern based on ozone oxidation and air stripping method according to claim 1, characterized in that: The electrolytic regeneration system includes an electrolytic cell, which regenerates into , and the electrolytic current density is 150 - 250 A / m².

9. The iodine extraction system from bittern based on ozone oxidation and air stripping method according to claim 1, wherein: The tail gas purification unit comprises an activated carbon adsorption-thermal desorption tower and an alkali solution washing tower. The desorption temperature of the activated carbon adsorption-thermal desorption tower is 100-150° C., and ozone and iodine are recovered and reused in the blowing tower.

10. A process for extracting iodine from brine in a brine iodine extraction system based on ozone oxidation and air stripping method as described in any one of claims 1-9, characterized in that: The following steps are involved: S1. The iodine-containing brine is pre-treated in a brine pre-treatment unit to remove suspended matter, impurities and some interference examples in the brine; S2, oxidizing the iodine ions in the brine into elemental iodine through an acidification and ozone oxidation unit; S3, blowing out the iodine in the oxidized brine through a multi-stage stripping unit, wherein: each stage of the stripping tower in the multi-stage stripping unit adopts a strategy of ozone segmentation, temperature gradient control, and gas-liquid ratio step-by-step optimization; S4. Absorbing the iodine in the iodine-containing air through the absorption and resource recovery unit, and realizing the recycling of the absorption liquid; S5. Purify the generated tail gas through the tail gas purification unit, and recycle the unreacted ozone and iodine to the multi-stage stripping unit.

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