Process method and system for extracting iodine from calcium-magnesium-sodium type brine

Abstract

The invention belongs to the technical field of brine extraction, and particularly relates to a process method and system for extracting iodine from calcium-magnesium-sodium type brine, the process comprises an iodine enrichment process and an iodine refining process, the first process comprises the following steps: firstly, removing organic matters and solid phase impurities in the raw material brine, then removing calcium ions, and then carrying out acidification and oxidation; finally, iodine-containing air and iodine-extracted brine are obtained through air blowing; meanwhile, after iodine-containing air is subjected to primary demisting and primary purification, alkali liquor is added for primary absorption and secondary absorption, and iodine-enriched liquid is obtained; and 2, acidifying the iodine enrichment liquid, separating out iodine crystals, separating the crystallized iodine from the mother liquor, adding purified water for washing, melting the crystallized iodine at high temperature, purifying and refining, and finally cooling and crushing to obtain the finished product iodine. The method provided by the invention fully realizes recovery and utilization of iodine resources, ensures the comprehensive utilization rate of the resources, absorbs free iodine in iodine-containing air twice by using the alkali liquor, avoids the use of sulfur dioxide, reduces the process risk, and improves the quality of iodine products.

Description

Technical Field

[0001] The invention belongs to the technical field of brine extraction, and in particular relates to a process and system for extracting iodine from calcium-magnesium-sodium type brine by using an air-blowing alkali absorption method. Background Art

[0002] Brine not only contains minerals and a small amount of organic matter, but also contains trace amounts of iodine. It is possible to consider extracting useful iodine from brine.

[0003] In the traditional air blowing method for preparing iodine, chlorine is introduced into the iodine-containing stock solution to oxidize the iodine ions into free iodine. The free iodine-containing stock solution is sprayed from the top of the desorption tower, and air is blown into the tower from the bottom to make it contact with the stock solution in reverse, and the iodine is blown out. The iodine-containing air enters the SO 2 The free iodine exists in the absorption liquid in the form of hydroiodic acid. After multiple cycles, when the iodine concentration reaches about 20 degrees Baume, the absorption liquid enters the iodine analyzer and solid iodine is precipitated after oxidation. The use of toxic gas sulfur dioxide cannot be avoided when preparing iodine using the traditional air blowing method. Not only is the process risk high, but the quality of the iodine product is also poor.

[0004] Therefore, based on the above problems, a process method and system for extracting iodine from calcium-magnesium-sodium brine by air-blowing alkali absorption method is designed, which does not require the use of toxic gas sulfur dioxide to absorb free iodine, can reduce process risks and improve the quality of iodine products. Summary of the invention

[0005] The purpose of the present invention is to address the deficiencies in the current technology in this field and to propose a process and system for extracting iodine from calcium-magnesium-sodium brine using an air-blowing alkali absorption method that can reduce process risks and improve the quality of iodine products.

[0006] The specific technical solutions provided by the present invention are as follows:

[0007] A process for extracting iodine from raw brine, the process mainly includes two steps, namely, an iodine enrichment step and an iodine refining step, wherein:

[0008] The iodine enrichment process includes the following steps: first, removing organic matter and solid impurities in the raw brine, then removing calcium ions, then acidifying and oxidizing, and finally blowing out through air to obtain iodine-containing air and iodine-extracted brine; at the same time, the iodine-containing air is subjected to primary demisting and primary purification, and then alkaline solution is added for primary absorption and secondary absorption to obtain iodine-enriched liquid;

[0009] The iodine refining process includes the following steps: first, the iodine-enriched liquid is acidified to allow iodine to crystallize, then the crystalline iodine is separated from the mother liquor, purified water is added for washing, then the crystalline iodine is melted at high temperature for purification, and finally cooled and crushed to obtain the finished iodine.

[0010] The second invention object of the present invention is to provide a process for extracting iodine from calcium-magnesium-sodium brine, including an iodine enrichment process and an iodine refining process, wherein the process steps are as follows:

[0011] Iodine enrichment process:

[0012] S1. Sand filtration: The raw calcium-magnesium-sodium brine is filtered through a sand filter to remove some organic matter and solid impurities;

[0013] S2, decalcification: After sand filtration, the brine enters the sulfuric acid removal tank, and sulfuric acid is added to remove calcium ions;

[0014] S3, Acidification and oxidation: Hydrochloric acid and chlorine are passed into the brine after impurities and calcium removal, and iodine ions undergo oxidation reaction: 2I - +Cl 2 →I 2 +2Cl - , generating free iodine;

[0015] S4, Blowing out: The oxidized brine is sent to the top of the blowing tower through a pipeline and then sprayed to penetrate the packing layer from top to bottom. The circulating air is introduced from the bottom of the tower through a fan to bring free iodine into the air from bottom to top;

[0016] S5, primary demisting: passing iodine-containing air through the packing to remove droplets;

[0017] S6, primary purification: purify the iodine-containing air to remove chlorine;

[0018] S7, primary absorption, secondary absorption: using alkaline solution to absorb iodine in iodine-containing air twice to obtain iodine-enriched liquid, which enters the iodine refining process;

[0019] Iodine refining process:

[0020] S8, acidification: adding acid to the obtained iodine-enriched solution for acidification, and iodine crystals are precipitated;

[0021] S9, solid-liquid separation: the absorption liquid containing crystallized iodine is discharged to a separator to separate the crystallized iodine from the mother liquor;

[0022] S10, washing and drying: adding purified water prepared by removing anions and cations through an ion exchange column for washing, and filtering and drying;

[0023] S11. Refined finished product: The crystalline iodine is melted at high temperature for purification and refinement, and finally cooled and crushed into finished iodine.

[0024] In the above technical solution, the calcium-magnesium-sodium brine in step S1 contains minerals, a small amount of organic matter and a trace amount of iodine, wherein the iodine ion content is 20-400 mg / L.

[0025] In the above technical solution, in step S7, free iodine in iodine-containing air is absorbed twice by alkaline solution, thereby enriching iodine-enriched liquid with high iodine content, and controlling the chloride ion content below 0.1%.

[0026] In the above technical solution, in step S8, hydrochloric acid or sulfuric acid is added to the iodine-enriched liquid for acidification, thereby precipitating crystalline iodine, and a separator is used for solid-liquid separation and drying.

[0027] In the above technical solution, in step S11, crystalline iodine and concentrated sulfuric acid are added to a reaction kettle for high-temperature melting and purification, and finally cooled and crushed into finished iodine.

[0028] The third invention object of the present invention is to provide an air blowing alkali method iodine extraction system, including an iodine enrichment system and an iodine refining system, wherein:

[0029] The iodine enrichment system comprises a sand filter, a decalcification device, an acidification oxidation device, a blow-out tower and a purification absorption device connected in sequence. The raw brine is passed through the sand filter to remove organic matter and solid impurities, and then passed through the decalcification device to remove calcium ions. It is then acidified and oxidized by the acidification oxidation device. After that, the air is blown out through the blow-out tower to obtain iodine-containing air and iodine-extracted brine. Finally, the iodine-containing air is purified and absorbed by the purification absorption device to obtain iodine-enriched liquid.

[0030] The iodine refining system comprises an acidification device, a separation device, a purification and refining device and a refined iodine crushing device which are connected in sequence. The iodine-enriched liquid is acidified by the acidification device to precipitate iodine crystals, and then the crystalline iodine and the mother liquor are separated by the separation device. The crystalline iodine is then purified and refined by the purification and refining device. Finally, the purified and refined iodine is cooled and crushed by the refined iodine crushing device to obtain finished iodine.

[0031] In the above technical solution, the purification and absorption device includes a first-level demisting chamber, a first-level purification chamber, a first-level absorption chamber, a second-level absorption chamber and a storage tank which are connected in sequence. The input end of the first-level demisting chamber is connected to the air blowing end of the blowing tower through a pipeline. The first-level absorption chamber and the second-level absorption chamber are respectively connected to alkali solution adding devices. The output end of the storage tank is branched into two stages, one branch is connected to the second-level absorption chamber through a reflux pipeline, and the other branch is connected to the input end of the acidification device through a drainage pipeline.

[0032] In the above technical solution, the acidification device includes a free cylinder, and the free cylinder is connected to a hydrochloric acid or sulfuric acid adding device.

[0033] In the above technical scheme, the separation device includes a separator, the absorption liquid containing crystallized iodine from the free cylinder is added to the separator to separate the crystallized iodine from the mother liquor, and then pure water is added for washing, and the mother liquor is filtered and dried, the mother liquor is discharged, and the crystallized iodine enters the purification and refining device for purification and refining.

[0034] In the above technical scheme, the purification and refining device includes a refining kettle, the crystallized iodine from the separator and the concentrated sulfuric acid from the concentrated sulfuric acid storage tank are added to the reaction kettle, and are purified and refined by high-temperature melting, the waste sulfuric acid is discharged into the waste sulfuric acid storage tank, and the refined iodine is discharged into the refined iodine crushing device.

[0035] In the above technical solution, the refined iodine crushing device includes a refined iodine crusher.

[0036] The advantages and positive effects of the present invention are:

[0037] 1. Compared with the traditional air blowing iodine extraction method, the process method of the present invention uses sodium hydroxide alkali solution instead of sulfur dioxide to absorb free iodine, then adds acid to precipitate solid iodine, and then obtains high-quality solid iodine through sublimation and crystallization after solid-liquid separation, washing and drying. The refining process steps are simpler, the use of toxic gas sulfur dioxide is avoided, the process risk is reduced, and the iodine product quality is higher.

[0038] 2. The process method of the present invention extracts iodine resources from brine, fully realizes the recovery and utilization of iodine resources, and ensures the comprehensive utilization rate of resources; alkali solution is used to absorb free iodine in iodine-containing air twice, thereby enriching iodine-enriched liquid with high iodine content, and the chloride ion content is controlled below 0.1%, ensuring that high-quality iodine is obtained in the later stage, reaching more than 99%.

[0039] 3. The process method of the present invention is applicable to brine with an iodine ion concentration of 20-400 mg / L and has a wide range of application. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The technical solution of the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments, but it should be understood that these drawings are designed only for explanation purposes and are not intended to limit the scope of the present invention. In addition, unless otherwise specified, these drawings are intended only to conceptually illustrate the structural configurations described herein and are not necessarily drawn to scale.

[0041] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0042] First of all, it should be noted that the specific structure, features and advantages of the present invention will be specifically described below by way of example, but all descriptions are only for illustration and should not be understood as limiting the present invention in any way. In addition, any single technical feature described or implied in the embodiments mentioned herein, or any single technical feature displayed or implied in the drawings, can still be combined or deleted between these technical features (or their equivalents) to obtain more other embodiments of the present invention that may not be directly mentioned in this document. In addition, in order to simplify the drawings, the same or similar technical features may be marked only in one place in the same drawing.

[0043] In the present invention, unless otherwise clearly specified and limited, the terms "installation", "setting", "connection", "fixation", "screwing" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined, for ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances. The present invention is described in detail below with reference to the accompanying drawings.

[0044] Embodiment 1:

[0045] A process for extracting iodine from raw brine, comprising an iodine enrichment process and an iodine refining process, wherein:

[0046] The iodine enrichment process includes the following steps: first, removing organic matter and solid impurities in the raw brine, then removing calcium ions, then acidifying and oxidizing, and finally blowing out through air to obtain iodine-containing air and iodine-extracted brine; at the same time, the iodine-containing air is subjected to primary demisting and primary purification, and then alkaline solution is added for primary absorption and secondary absorption to obtain iodine-enriched liquid;

[0047] The iodine refining process includes the following steps: first, the iodine-enriched liquid is acidified to allow iodine to crystallize, then the crystalline iodine is separated from the mother liquor, purified water is added for washing, then the crystalline iodine is melted at high temperature for purification, and finally cooled and crushed to obtain the finished iodine.

[0048] Compared with the traditional air blowing iodine extraction method, the above process method uses sodium hydroxide alkali solution instead of sulfur dioxide to absorb free iodine, then adds acid to precipitate solid iodine, and then obtains high-quality solid iodine through sublimation and crystallization after solid-liquid separation, washing and drying. The refining process steps are simpler, avoids the use of toxic gas sulfur dioxide, reduces process risks, and the iodine product quality is higher.

[0049] Embodiment 2:

[0050] A process for extracting iodine from calcium-magnesium-sodium brine includes an iodine enrichment process and an iodine refining process, wherein the process steps are as follows:

[0051] Iodine enrichment process

[0052] 1) Sand filtration: The raw calcium-magnesium-sodium brine contains not only minerals and a small amount of organic matter, but also trace amounts of iodine, with an iodine ion content of 20-400 mg / L. First, it is filtered through a sand filter to remove some of the organic matter and solid impurities;

[0053] 2) Decalcification: After sand filtration, the brine enters the sulfuric acid removal tank and sulfuric acid is added to remove calcium ions;

[0054] 3) Acidification and oxidation: Hydrochloric acid and chlorine are passed into the brine after impurities and calcium removal, and iodine ions undergo oxidation reaction: 2I - +Cl 2 →I 2 +2Cl - , generating free iodine;

[0055] 4) Blowing out: The oxidized brine is sent to the top of the blowing tower through a pipeline and then sprayed to penetrate the packing layer from top to bottom. The circulating air is introduced from the bottom of the tower through a fan, and the free iodine is brought into the air from bottom to top;

[0056] 5) Primary demisting: passing iodine-containing air through the packing to remove droplets;

[0057] 6) Primary purification: purify the iodine-containing air to remove chlorine;

[0058] 7) Primary absorption and secondary absorption: Alkaline solution is used to absorb iodine in the air twice to obtain enriched liquid, which enters the iodine refining process. Raw brine is used to perform primary demisting and primary purification on the iodine-containing air to ensure the quality of subsequent products; then alkali solution is used to absorb free iodine in the iodine-containing air twice, thereby enriching iodine-enriched water with high iodine content to ensure that the chloride ion content is controlled below 0.1%.

[0059] Iodine refining process:

[0060] 8) Acidification: adding hydrochloric acid or sulfuric acid to the obtained iodine-enriched solution to precipitate crystalline iodine;

[0061] 9) Solid-liquid separation: using a separator to separate the solid and liquid and dry, the absorption liquid containing the crystallized iodine is discharged into the separator to separate the crystallized iodine from the mother liquor;

[0062] 10) Washing and drying: adding purified water prepared by removing anions and cations such as calcium, magnesium, chloride and sulfate through an ion exchange column for washing, and then filtering and drying;

[0063] 11) Refined products: Add crystalline iodine and concentrated sulfuric acid into a reactor, melt at high temperature for purification, and finally cool and crush to obtain finished iodine.

[0064] This embodiment provides a process for extracting iodine from calcium-magnesium-sodium brine. The process mainly includes two steps, namely, an iodine enrichment step and an iodine refining step. Specifically:

[0065] Iodine enrichment process: First, the raw brine is filtered through a sand filter to remove organic matter and solid impurities, then sulfuric acid is added to remove calcium ions, and then acidified and oxidized by hydrochloric acid and chlorine, and then blown out through air to obtain iodine-containing air and iodine-extracted brine. At the same time, the iodine-containing air is subjected to primary demisting and primary purification, and then alkali solution is added for primary absorption and secondary absorption. After hydrochloric acid or sulfuric acid is added to the absorption liquid, an absorption liquid containing solid-phase crystallized iodine is obtained.

[0066] Iodine refining process: discharge the absorption liquid containing crystalline iodine into the separator, separate the crystalline iodine from the mother liquor, add pure water prepared by removing anions and cations such as calcium, magnesium, chloride and sulfate through an ion exchange column for washing, then add the crystalline iodine and concentrated sulfuric acid into the reactor for high-temperature melting and purification, and finally cool and crush into finished iodine. The quality of the finished iodine produced by this process is improved to more than 99%.

[0067] The process of the present invention extracts iodine resources from brine, and uses alkali liquor to absorb free iodine in iodine-containing air twice, thereby enriching and obtaining an iodine-enriched liquid with high iodine content, and the chloride ion content is controlled below 0.1%, thereby ensuring that high-quality iodine is obtained in the later stage. The raw material brine is used to perform a first-level demisting and a first-level purification on the iodine-containing air, thereby ensuring the quality of subsequent products. In the iodine refining stage, the iodine-enriched liquid is acidified by adding hydrochloric acid or sulfuric acid to precipitate crystalline iodine, and a separator is used for solid-liquid separation and drying. The crystalline iodine and concentrated sulfuric acid are added to a reactor for high-temperature melting and purification, and finally cooled and crushed into finished iodine, and the quality of the finished iodine is improved by more than 99%.

[0068] The process innovation of the present invention is:

[0069] 1. Extract iodine from calcium-magnesium-sodium brine, fully realize the recovery and utilization of iodine resources, and ensure the comprehensive utilization rate of resources;

[0070] 2. This method is applicable to brine with an iodine ion concentration of 20-400 mg / L, and has a wide range of applications;

[0071] 3. The first-stage demisting and first-stage purification ensure the quality of the later products;

[0072] 4. The alkaline calcium-magnesium-sodium brine with high iodine content is obtained by air blowing out the alkaline absorption and enrichment method. The chloride ion content is controlled below 0.1%, ensuring high-quality iodine products in the later stage;

[0073] 5. Sodium hydroxide lye is used instead of sulfur dioxide to absorb free iodine, and then acid is added to precipitate solid iodine. After solid-liquid separation, washing and drying, high-quality solid iodine is obtained by sublimation and crystallization. Compared with the traditional air blowing method, its refining process is simpler, avoiding the use of toxic gas sulfur dioxide and reducing process risks.

[0074] Embodiment 3:

[0075] An air-blowing alkali-method iodine extraction system comprises an iodine enrichment system and an iodine refining system, wherein:

[0076] The iodine enrichment system comprises a sand filter, a decalcification device, an acidification oxidation device, a blow-out tower and a purification absorption device connected in sequence. The raw brine is passed through the sand filter to remove organic matter and solid impurities, and then passed through the decalcification device to remove calcium ions. It is then acidified and oxidized by the acidification oxidation device. After that, the air is blown out through the blow-out tower to obtain iodine-containing air and iodine-extracted brine. Finally, the iodine-containing air is purified and absorbed by the purification absorption device to obtain iodine-enriched liquid.

[0077] The iodine refining system comprises an acidification device, a separation device, a purification and refining device and a refined iodine crushing device which are connected in sequence. The iodine-enriched liquid is acidified by the acidification device to precipitate iodine crystals, and then the crystalline iodine and the mother liquor are separated by the separation device. The crystalline iodine is then purified and refined by the purification and refining device. Finally, the purified and refined iodine is cooled and crushed by the refined iodine crushing device to obtain finished iodine.

[0078] Furthermore, in this embodiment, it can also be considered that the decalcification device includes a sulfuric acid impurity removal tank.

[0079] Furthermore, in this embodiment, it is also conceivable to introduce hydrochloric acid and chlorine into the acidification oxidation device, and the iodine ions undergo oxidation reaction in the brine after impurities and calcium removal.

[0080] In the blowing tower, the oxidized brine is sent to the top of the blowing tower through a pipeline and then sprayed to penetrate the packing layer from top to bottom. Circulating air is introduced from the bottom of the tower through a fan to bring free iodine into the air from bottom to top.

[0081] Furthermore, in the present embodiment, it can also be considered that the purification and absorption device includes a first-level demisting chamber, a first-level purification chamber, a first-level absorption chamber, a second-level absorption chamber and a storage tank which are connected in sequence, the input end of the first-level demisting chamber is connected to the air blowing end of the blowing tower through a pipe, the first-level absorption chamber and the second-level absorption chamber are respectively connected to an alkali solution adding device, the output end of the storage tank is branched into two stages, one branch is connected to the second-level absorption chamber through a reflux pipe, and the other branch is connected to the input end of the acidification device through a discharge pipe. The absorption liquid that does not meet the standards can be returned to the second-level absorption chamber for secondary purification by means of the reflux pipe.

[0082] Furthermore, in this embodiment, it can also be considered that fillers are provided in the first-stage demister, a filter element for removing chlorine is provided in the first-stage purification chamber, and alkaline solution is provided in the first-stage absorption chamber and the second-stage absorption chamber.

[0083] Furthermore, in this embodiment, it can also be considered that the acidification device includes a free cylinder, and the free cylinder is connected to a hydrochloric acid or sulfuric acid adding device.

[0084] Furthermore, in this embodiment, it can also be considered that the separation device includes a separator, the absorption liquid containing crystallized iodine from the free cylinder is added to the separator to separate the crystallized iodine from the mother liquor, and then pure water is added for washing, and the mother liquor is filtered and dried, the mother liquor is discharged, and the crystallized iodine enters the purification and refining device for purification and refining.

[0085] Furthermore, in this embodiment, it can also be considered that the purification and refining device includes a refining kettle, the crystallized iodine from the separator and the concentrated sulfuric acid from the concentrated sulfuric acid storage tank are added to the reactor, and are purified and refined by high-temperature melting, the waste sulfuric acid is discharged into the waste sulfuric acid storage tank, and the refined iodine is discharged into the refined iodine crushing device.

[0086] Furthermore, in this embodiment, it can also be considered that the refined iodine crushing device includes a refined iodine crusher.

[0087] Application examples:

[0088] The iodine is extracted by applying the process for extracting iodine from calcium-magnesium-sodium brine disclosed in the above embodiment, and the extraction process is as follows:

[0089] 1) Sand filtration: The raw material calcium magnesium sodium brine contains minerals, a small amount of organic matter, and an iodine content of 20-400 mg / L. Take 100m 3 The raw brine is first filtered through a sand filter to remove some organic matter and solid impurities to obtain 99.9m 3 Raw material brine;

[0090] 2) Calcium removal: After sand filtration, it enters the sulfuric acid impurity removal tank, adds sulfuric acid to remove calcium ions, and obtains 99.8m 3 Liquid feed;

[0091] 3) Acidification and oxidation: 1.1 kg hydrochloric acid and 3.4 kg chlorine gas are introduced into the brine after impurities and calcium removal, and the iodine ions undergo oxidation reaction: 2I - +Cl 2 →I 2 +2Cl - , generating free iodine;

[0092] 4) Blowing out: The oxidized brine is sent to the top of the blowing tower through a pipeline and then sprayed to penetrate the packing layer from top to bottom. The circulating air is introduced from the bottom of the tower through a fan, and the free iodine is brought into the air from bottom to top;

[0093] 5) Primary demisting: passing iodine-containing air through the packing to remove droplets;

[0094] 6) Primary purification: purify the iodine-containing air to remove chlorine;

[0095] 7) Primary absorption: using 0.05m 3 The 5%-20% alkali solution absorbs the free iodine in the air to obtain about 0.06m 3 Enrichment solution;

[0096] 8) Secondary absorption: Reuse 0.05m 3 The 5%-20% alkali solution absorbs the free iodine in the air in the second stage to obtain 0.12m 3 The enriched liquid enters the iodine refining process.

[0097] Iodine refining process:

[0098] 9) Acidification: Add about 15 kg of 20%-30% hydrochloric acid or sulfuric acid to the obtained iodine-enriched solution for acidification, and iodine crystals are precipitated to obtain about 9.8 kg of crude iodine;

[0099] 10) Solid-liquid separation: the absorption liquid containing crystallized iodine is discharged to a separator to separate the crystallized iodine from the mother liquor;

[0100] 11) Washing and drying: adding pure water prepared by removing anions and cations such as calcium, magnesium, chloride and sulfate through an ion exchange column for washing, and then using a vacuum pump to drain the crystallized iodine;

[0101] 12) Refined finished product: Add crystalline iodine and 98% concentrated sulfuric acid into a reactor and melt at high temperature for purification and refinement, and finally cool and crush into 99% finished iodine, about 9 kg.

[0102] The above embodiments describe the present invention in detail, but the contents are only preferred embodiments of the present invention and cannot be considered to limit the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the present invention.

Claims

1. A process for extracting iodine from raw brine, characterized in that: The method comprises an iodine enrichment process and an iodine refining process, wherein: The iodine enrichment process includes the following steps: first, removing organic matter and solid impurities in the raw brine, then removing calcium ions, then acidifying and oxidizing, and finally blowing out through air to obtain iodine-containing air and iodine-extracted brine; at the same time, the iodine-containing air is subjected to primary demisting and primary purification, and then alkaline solution is added for primary absorption and secondary absorption to obtain iodine-enriched liquid; The iodine refining process includes the following steps: first, the iodine-enriched liquid is acidified to allow iodine to crystallize, then the crystalline iodine is separated from the mother liquor, purified water is added for washing, then the crystalline iodine is melted at high temperature for purification, and finally cooled and crushed to obtain the finished iodine.

2. A process for extracting iodine from calcium-magnesium-sodium brine, characterized in that: The process includes an iodine enrichment process and an iodine refining process, and the process steps are as follows: Iodine enrichment process: S1. Sand filtration: The raw calcium-magnesium-sodium brine is filtered through a sand filter to remove some organic matter and solid impurities; S2, decalcification: After sand filtration, the brine enters the sulfuric acid removal tank, and sulfuric acid is added to remove calcium ions; S3, Acidification and oxidation: Hydrochloric acid and chlorine are passed into the brine after impurities and calcium removal, and iodine ions undergo oxidation reaction: , generating free iodine; S4, Blowing out: The oxidized brine is sent to the top of the blowing tower through a pipeline and then sprayed to penetrate the packing layer from top to bottom. The circulating air is introduced from the bottom of the tower through a fan to bring free iodine into the air from bottom to top; S5, primary demisting: passing iodine-containing air through the packing to remove droplets; S6, primary purification: purify the iodine-containing air to remove chlorine; S7, primary absorption, secondary absorption: using alkaline solution to absorb iodine in iodine-containing air twice to obtain iodine-enriched liquid, which enters the iodine refining process; Iodine refining process: S8, acidification: adding acid to the obtained iodine-enriched solution for acidification, and iodine crystals are precipitated; S9, solid-liquid separation: the absorption liquid containing crystallized iodine is discharged to a separator to separate the crystallized iodine from the mother liquor; S10, washing and drying: adding purified water prepared by removing anions and cations through an ion exchange column for washing, and filtering and drying; S11. Refined finished product: The crystalline iodine is melted at high temperature for purification and refinement, and finally cooled and crushed into finished iodine.

3. A process for extracting iodine from calcium-magnesium-sodium brine according to claim 2, characterized in that: The calcium-magnesium-sodium brine in step S1 contains minerals, a small amount of organic matter and a trace amount of iodine, wherein the iodine ion content is 20-400 mg / L.

4. A process for extracting iodine from calcium-magnesium-sodium brine according to claim 2, characterized in that: In step S7, free iodine in the iodine-containing air is absorbed twice by alkaline solution, thereby enriching the iodine-enriched liquid with a high iodine content, and controlling the chloride ion content below 0.1%.

5. A process for extracting iodine from calcium-magnesium-sodium brine according to claim 2, characterized in that: In step S8, hydrochloric acid or sulfuric acid is added to the iodine-enriched liquid for acidification, thereby precipitating crystalline iodine, and a separator is used for solid-liquid separation and drying.

6. A process for extracting iodine from calcium-magnesium-sodium brine according to claim 2, characterized in that: In step S11, crystalline iodine and concentrated sulfuric acid are added into a reaction kettle for high temperature melting and purification, and finally cooled and crushed into finished iodine.

7. An iodine extraction system using the process for extracting iodine from calcium-magnesium-sodium type brine as claimed in any one of claims 2 to 6, characterized in that: It includes an iodine enrichment system and an iodine refining system, wherein: The iodine enrichment system comprises a sand filter, a decalcification device, an acidification oxidation device, a blow-out tower and a purification absorption device connected in sequence. The raw brine is passed through the sand filter to remove organic matter and solid impurities, and then passed through the decalcification device to remove calcium ions. It is then acidified and oxidized by the acidification oxidation device. After that, the air is blown out through the blow-out tower to obtain iodine-containing air and iodine-extracted brine. Finally, the iodine-containing air is purified and absorbed by the purification absorption device to obtain iodine-enriched liquid. The iodine refining system comprises an acidification device, a separation device, a purification and refining device and a refined iodine crushing device which are connected in sequence. The iodine-enriched liquid is acidified by the acidification device to precipitate iodine crystals, and then the crystalline iodine and the mother liquor are separated by the separation device. The crystalline iodine is then purified and refined by the purification and refining device. Finally, the purified and refined iodine is cooled and crushed by the refined iodine crushing device to obtain finished iodine.

8. A system for extracting iodine from calcium-magnesium-sodium brine according to claim 7, characterized in that: The purification and absorption device comprises a primary demisting chamber, a primary purification chamber, a primary absorption chamber, a secondary absorption chamber and a storage tank which are connected in sequence. The input end of the primary demisting chamber is connected to the air blowing end of the blowing tower through a pipeline. The primary absorption chamber and the secondary absorption chamber are respectively connected to alkali solution adding devices. The output end of the storage tank is branched into two stages, one branch is connected to the secondary absorption chamber through a reflux pipeline, and the other branch is connected to the input end of the acidification device through a drainage pipeline.

9. A system for extracting iodine from calcium-magnesium-sodium brine according to claim 7, characterized in that: The separation device comprises a separator, and the absorption liquid containing crystallized iodine from the free cylinder is added into the separator to separate the crystallized iodine from the mother liquor, and then pure water is added for washing, and suction filtration and drying are performed, the mother liquor is discharged, and the crystallized iodine enters the purification and refining device for purification and refining.

10. A system for extracting iodine from calcium-magnesium-sodium brine according to claim 7, characterized in that: The purification and refining device comprises a refining kettle, the crystallized iodine from the separator and the concentrated sulfuric acid from the concentrated sulfuric acid storage tank are added into the reaction kettle, and are purified and refined by high-temperature melting, the waste sulfuric acid is discharged into the waste sulfuric acid storage tank, and the refined iodine is discharged into the refined iodine crushing device.

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