A method and apparatus for iodine recovery

Abstract

The application discloses a method and device for recovering iodine, which is used for removing solid impurities and efficiently recovering iodine. The method comprises the following steps: conveying sulfur-burning furnace generated sulfur dioxide gas containing impurities to a buffer tank, removing solid impurities in the sulfur dioxide gas containing impurities by gravity sedimentation in the buffer tank, and obtaining purified sulfur dioxide gas; conveying the purified sulfur dioxide gas to a SO2 absorption tank to form SO2 absorption liquid; conveying the SO2 absorption liquid to the top of an absorption tower for spraying, and performing an oxidation-reduction reaction with iodine vapor to obtain iodine ion-containing absorption liquid; refluxing the iodine ion-containing absorption liquid to the SO2 absorption tank and cyclically conveying the iodine ion-containing absorption liquid to the absorption tower for reaction; when the content of iodine ions in the iodine ion-containing absorption liquid reaches a preset content threshold, conveying the iodine ion-containing absorption liquid to an oxidation tank to react with an oxidizing agent to obtain iodine-containing material; and conveying the iodine-containing material to a centrifugal machine for solid-liquid separation to obtain iodine product.

Description

Technical Field

[0001] This application relates to the field of chemical technology, and in particular to a method and apparatus for iodine recovery. Background Technology

[0002] With the continuous growth in global demand for iodine from the chemical, pharmaceutical, and food additive industries, the efficient and economical recovery of iodine from various iodine-containing resources has become a major development direction for the iodine chemical industry to increase production capacity and control costs. The sulfur dioxide reduction method, due to its stable reaction efficiency and high technological maturity, is one of the mainstream processes for industrial iodine recovery. In continuous industrial production, the stable and clean transportation of sulfur dioxide gas is a key factor in ensuring the continuous operation of the iodine recovery system and maintaining product purity and recovery rate. The cleanliness and transportation stability of the gas flow directly affect the operating efficiency of the entire production line and the quality of the final product.

[0003] In existing technologies, direct-connection pipeline technology is typically used to supply sulfur dioxide gas from the sulfur incinerator to the iodine absorption reactor. Specifically, after the sulfur incinerator burns sulfur to produce sulfur dioxide gas, the high-temperature sulfur dioxide gas stream is directly and continuously transported through a pipeline to the subsequent iodine absorption tank or absorption tower. The gas stream travels along the pipeline throughout its journey into the reaction system to participate in the iodine reduction reaction.

[0004] However, since the sulfur dioxide gas produced by the sulfur incinerator inevitably carries unreacted sulfur slag and other solid particles, these solid particles will gradually deposit and scale at pipe bends, valves and other parts with large airflow disturbances after being transported directly by this direct pipeline technology. This will form hard slag, continuously reduce the effective diameter of the pipeline, increase the transport resistance and increase the operating energy consumption, and also cause pipeline blockage, resulting in gas supply interruption and unplanned shutdown of the production line. Summary of the Invention

[0005] To address the aforementioned technical problems, this application provides a method and apparatus for iodine recovery.

[0006] The technical solution provided in this application is described below:

[0007] A first aspect of this application provides a method for iodine recovery, the method comprising: The sulfur dioxide gas containing impurities generated by the sulfur incinerator is transported to a buffer tank, where solid impurities are removed by gravity settling to obtain purified sulfur dioxide gas. The purified sulfur dioxide gas is transported to an SO2 absorption tank to form an SO2 absorption liquid; The SO2 absorbent is transported to the top of the absorption tower for spraying and undergoes an oxidation-reduction reaction with iodine vapor to convert the iodine vapor into iodide ions, thus obtaining an iodide-containing absorbent. The iodine-containing absorbent is returned to the SO2 absorption tank to continue absorbing the purified sulfur dioxide gas and is then circulated to the absorption tower for reaction. When the iodine ion content in the iodine ion absorption liquid reaches a preset content threshold, the iodine ion absorption liquid is transported to an oxidation tank to react with an oxidant, so that the iodine ions are converted into elemental iodine, and iodine-containing material is obtained. The iodine-containing material is fed into a centrifuge for solid-liquid separation to obtain the iodine product.

[0008] Optionally, the step of removing solid impurities from the sulfur dioxide gas containing impurities by gravity settling in the buffer tank to obtain purified sulfur dioxide gas includes: When the sulfur dioxide gas containing impurities enters the buffer tank, the flow rate of the sulfur dioxide gas containing impurities is reduced by the buffer tank, so that the solid impurities in the sulfur dioxide gas containing impurities settle to the bottom of the buffer tank under the action of gravity, and the purified sulfur dioxide gas is discharged from the top of the buffer tank.

[0009] Optionally, the buffer tank is provided with an air inlet, an air outlet, and a slag discharge outlet; The air inlet is located in the lower middle part of the buffer tank, and a guide baffle with a tangential air inlet structure is provided at the air inlet to prolong the residence time of the sulfur dioxide gas containing impurities in the buffer tank. The outlet is located at the top of the buffer tank and is used to discharge the purified sulfur dioxide gas. The slag discharge port is located at the bottom of the buffer tank and is used to discharge the solid impurities that have settled to the bottom.

[0010] Optionally, the step of conveying the SO2 absorbent to the top of the absorption tower for spraying and reacting it with iodine vapor in a redox reaction includes: The SO2 absorbent is sprayed down from the top of the absorption tower, while iodine vapor is introduced from the bottom of the absorption tower, so that the SO2 absorbent and the iodine vapor come into countercurrent contact in the absorption tower and undergo an oxidation-reduction reaction.

[0011] Optionally, when the iodine ion content in the iodine-containing absorbent reaches a preset content threshold, the iodine-containing absorbent is transported to an oxidation tank to react with an oxidant, converting the iodine ions into elemental iodine to obtain an iodine-containing material, including: The content of iodine ions in the iodine-containing absorption solution returned to the SO2 absorption tank is detected; When the detected iodine ion content reaches a preset content threshold, the circulation of the iodine ion-containing absorbent is stopped, and the iodine ion-containing absorbent is transported to the oxidation tank. An oxidizing agent is added to the oxidation tank to oxidize the iodide ions in the iodide-containing absorption liquid into elemental iodine, thereby obtaining an iodine-containing material.

[0012] Optionally, the method further includes: When there is residual SO2 absorbent in the SO2 absorption tank and / or iodine-containing absorbent that has been returned to the SO2 absorption tank, the newly supplied purified sulfur dioxide gas is introduced into the SO2 absorption tank to mix with the liquid already present in the SO2 absorption tank, so as to continue to participate in the absorption process.

[0013] Optionally, after conveying the iodine-containing material to a centrifuge for solid-liquid separation to obtain the iodine product, the method further includes: Collect the mother liquor produced after solid-liquid separation; The mother liquor is returned to the SO2 absorption tank and continues to participate in the absorption process of the purified sulfur dioxide gas in the SO2 absorption tank to form the SO2 absorption liquid, thereby realizing the recycling of materials.

[0014] A second aspect of this application provides an apparatus for iodine recovery, the apparatus comprising: A buffer tank is provided with an air inlet and an air outlet. The air inlet is used to receive sulfur dioxide gas containing impurities, and the buffer tank is used to remove solid impurities from the sulfur dioxide gas containing impurities by gravity settling. The SO2 absorption tank is equipped with a gas inlet and a liquid outlet. The gas inlet is connected to the gas outlet of the buffer tank and is used to absorb purified sulfur dioxide gas to form SO2 absorption liquid. The absorption tower is equipped with a spray inlet, a gas inlet, and a liquid outlet. The spray inlet is connected to the liquid outlet of the SO2 absorption tank. The liquid outlet of the absorption tower is connected to the SO2 absorption tank through a reflux pipeline. The gas inlet of the absorption tower is used to introduce iodine vapor so that the iodine vapor reacts with the SO2 absorbent in the absorption tower to obtain an iodine-containing absorbent. An oxidation tank is provided with an inlet and an outlet. The inlet is connected to the liquid outlet of the SO2 absorption tank or the absorption tower. It is used to oxidize iodine ions in the iodine-containing absorption liquid to obtain iodine-containing material. The centrifuge is equipped with a feed inlet, a solid phase outlet, and a liquid phase outlet. The feed inlet is connected to the discharge outlet of the oxidation tank and is used for solid-liquid separation of the oxidized iodine-containing material.

[0015] Optionally, the buffer tank is also provided with a slag discharge port; The air inlet is located in the lower middle part of the buffer tank, the air outlet is located at the top of the buffer tank, and the slag discharge port is located at the bottom of the buffer tank. The buffer tank is equipped with a flow guide baffle to form a gravity settling zone within the buffer tank.

[0016] Optionally, the reflux line is equipped with a content detector and a control valve; The content detector is used to detect the content of iodine ions in the iodine-containing absorption liquid in the reflux pipeline or the SO2 absorption tank; The control valve is communicatively connected to the content detector and is used to cut off the reflux pipeline and divert the liquid in the SO2 absorption tank or the liquid in the absorption tower to the oxidation tank when the iodide ion content reaches a preset content threshold.

[0017] As can be seen from the above technical solutions, this application has the following advantages: 1. The sulfur dioxide gas containing impurities generated by the sulfur incinerator is transported to the buffer tank. The solid impurities such as sulfur slag carried in the gas flow are removed in advance by gravity settling, resulting in purified sulfur dioxide gas. Large solid particles are intercepted by gravity settling, which blocks solid particles from entering the subsequent conveying pipeline and reaction system from the source. This avoids the deposition and scaling of impurities at pipe bends and valves, effectively preventing the risk of pipe diameter reduction, increased conveying resistance and blockage. 2. The purified sulfur dioxide gas is transported to the SO2 absorption tank to form SO2 absorbent liquid. The SO2 absorbent liquid is then transported to the top of the absorption tower for spraying, where it undergoes an oxidation-reduction reaction with iodine vapor to convert iodine vapor into iodide ions. The iodide-containing absorbent liquid after the reaction is returned to the SO2 absorption tank for repeated absorption and reaction. Since the sulfur dioxide gas entering the reaction system has been purified, no solid impurities will be introduced to contaminate the absorbent liquid, ensuring the cleanliness of the reaction system and avoiding impurities from interfering with the reduction reaction process. Furthermore, the countercurrent contact mode of circulating and spraying the absorbent liquid significantly improves the sufficiency of gas-liquid contact and reaction efficiency, thereby increasing the absorption and conversion rate of iodine vapor. 3. When the iodine ion content of the iodine ion absorption liquid reaches the preset threshold, it is transported to the oxidation tank to react with the oxidant to convert the iodine ions into elemental iodine. Then, it is sent to the centrifuge to complete the solid-liquid separation and obtain the finished elemental iodine product. Throughout the process, foreign impurities such as sulfur residue are avoided from mixing into the reaction materials. Finally, the iodine product obtained by centrifugation has higher purity, eliminating the negative impact of solid impurities on product quality and achieving a dual improvement in iodine recovery efficiency and product purity. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the accompanying drawings required in the description of the embodiments or the prior art. Obviously, the drawings described below are only some embodiments of the present application, and for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without any creative effort.

[0019] Figure 1 is a schematic flowchart of an embodiment of the iodine recovery method provided by the present application; Figure 2 is a schematic flowchart of another embodiment of the iodine recovery method provided by the present application; Figure 3 is a schematic structural diagram of an embodiment of the iodine recovery apparatus provided by the present application. Detailed Description of the Embodiments

[0020] It should be noted that the iodine recovery method and apparatus provided by the present application are applicable to various industrial production scenarios that generate iodine vapor, such as fine chemical industry, pharmaceutical manufacturing, pesticide synthesis, and iodine resource regeneration, for example, the recovery and purification treatment of elemental iodine in scenarios such as iodine recovery production lines supporting sulfur burning processes, tail gas treatment of iodine-containing organic synthesis reactions, resource purification of waste iodine liquid, and recycling of iodine resources in iodination reaction processes, and are particularly suitable for iodine resource recovery scenarios of sulfur furnace gas entrained with solid impurities, continuous large-scale production, and high purity requirements for finished elemental iodine products.

[0021] Please refer to Figure 1 , the present application first provides an embodiment of the iodine recovery method, and this embodiment includes: S101. Convey the impurity-containing sulfur dioxide gas generated by the sulfur burning furnace to a buffer tank, and remove solid impurities in the impurity-containing sulfur dioxide gas through gravity sedimentation in the buffer tank to obtain purified sulfur dioxide gas; In this embodiment, the impurity-containing sulfur dioxide gas that is generated by burning sulfur in the sulfur burning furnace and carries solid particles such as incompletely reacted sulfur slag needs to be introduced into the buffer tank through a conveying pipeline in advance.

[0022] After the impurity-containing sulfur dioxide gas enters the buffer tank, since the internal flow cross-sectional area of the buffer tank is much larger than that of the conveying pipeline, the gas flow velocity will be greatly reduced, so the carrying capacity of the gas flow for solid particles is greatly decreased. As a result, solid impurities such as sulfur slag with a density much higher than that of sulfur dioxide gas will gradually separate from the gas flow, thereby completing the separation of solid impurities from the gas phase and obtaining purified sulfur dioxide gas.

[0023] S102. Convey the purified sulfur dioxide gas into a SO2 absorption tank to form a SO2 absorption liquid; After being purified in the buffer tank, the sulfur dioxide gas is introduced into the liquid medium of the SO2 absorption tank through the gas distribution device. The purified sulfur dioxide gas comes into full contact with the liquid in the SO2 absorption tank in the form of microbubbles. The purified sulfur dioxide gas gradually dissolves and diffuses into the liquid to form SO2 absorption liquid with reducing activity.

[0024] This utilizes the property that sulfur dioxide gas is easily soluble in liquid. Through gas-liquid contact, the gaseous sulfur dioxide is transferred to the liquid phase, transforming the gaseous reducing agent into a liquid form that is easy to transport and circulate.

[0025] S103. The SO2 absorbent is transported to the top of the absorption tower for spraying and undergoes an oxidation-reduction reaction with iodine vapor to convert the iodine vapor into iodide ions, thus obtaining an iodide-containing absorbent. After the SO2 absorbent is formed, the prepared SO2 absorbent in the SO2 absorption tank is sprayed onto the top spray layer of the absorption tower.

[0026] Meanwhile, iodine vapor is introduced from the bottom of the absorption tower and forms a countercurrent contact with the downward sprayed SO2 absorbent. The gas and liquid phases are fully contacted on the packing surface and undergo a redox reaction. Sulfur dioxide in the SO2 absorbent acts as a reducing agent, reducing the iodine vapor in the gas phase to iodide ions and transferring them to the liquid phase, resulting in an absorbent rich in iodide ions.

[0027] S104. The iodide-containing absorbent is returned to the SO2 absorption tank to continue absorbing the purified sulfur dioxide gas and is then circulated to the absorption tower for reaction. The iodide-containing absorbent solution, after completing the reaction inside the absorption tower, flows out from the bottom of the tower and is returned to the SO2 absorption tank via a reflux pipeline. The returned SO2 absorbent solution then comes into full contact again with the newly introduced purified sulfur dioxide gas in the SO2 absorption tank, replenishing the consumed sulfur dioxide components in the liquid phase and restoring the reducing activity of the absorbent solution.

[0028] Afterwards, the SO2 absorbent, replenished with reducing agent, is pressurized again by a transfer pump and sent to the top of the absorption tower to participate in a new round of iodine vapor reduction reaction, thus forming a cycle. During the repeated cycles, iodine vapor is continuously converted into iodide ions, gradually increasing the concentration of iodide ions in the SO2 absorbent.

[0029] S105. When the content of iodine ions in the iodine ion absorption liquid reaches the preset content threshold, the iodine ion absorption liquid is transported to the oxidation tank to react with the oxidant, so that the iodine ions are converted into elemental iodine, and iodine-containing material is obtained. In this embodiment, the concentration change of the iodine ion absorbent in the circulating system is monitored in real time. When the iodine ion content in the iodine ion absorbent reaches the preset content threshold, the circulating absorption process is terminated, and the iodine ion absorbent that has reached the preset content threshold is transported to the oxidation tank. The preset content threshold is the optimal concentration point determined by combining the optimal feed concentration of the oxidation reaction, production efficiency and cost, etc. It can be set to 80% content, and the specific value is determined according to actual needs, which is not limited here.

[0030] Then, the corresponding oxidant is added to the oxidation tank. Under the condition of stirring and mixing, the oxidant comes into full contact with the iodine ions in the iodine ion absorption liquid and undergoes an oxidation reaction. The iodine ions lose electrons and are oxidized into elemental iodine, which precipitates out in the form of solid particles to form iodine-containing material.

[0031] S106. The iodine-containing material is fed to a centrifuge for solid-liquid separation to obtain the iodine product.

[0032] In this embodiment, the iodine-containing material that has completed its reaction in the oxidation tank is pumped into a centrifuge. After the centrifuge is started, the high-speed rotation generates a strong centrifugal force field. The solid iodine particles, whose density is much greater than that of the liquid phase in the iodine-containing material, are thrown against the inner wall of the drum under the action of centrifugal force and gradually aggregate and compact. The liquid phase is separated and discharged through the filter medium. After sufficient centrifugal separation, a finished iodine product with a low water content is obtained.

[0033] In this embodiment, sulfur dioxide gas containing impurities generated by a sulfur incinerator is transported to a buffer tank. Gravity settling is used to pre-remove solid impurities such as sulfur slag from the gas stream, resulting in purified sulfur dioxide gas. Gravity settling also traps large solid particles, preventing them from entering subsequent pipelines and the reaction system at the source. This avoids scale buildup at pipe bends and valves, effectively preventing narrowing of pipe diameter, increased transport resistance, and blockage risks. The purified sulfur dioxide gas is then transported to an SO2 absorption tank to form SO2 absorbent. The SO2 absorbent is then sprayed at the top of the absorption tower, where it undergoes an oxidation-reduction reaction with iodine vapor, converting the iodine vapor into iodide ions. The resulting iodide-containing absorbent is then returned to the SO2 absorption tank for further absorption and reaction. Since the sulfur dioxide gas entering the reaction system has been purified, no solid impurities will be introduced to contaminate the absorbent, ensuring the cleanliness of the reaction system and preventing impurities from interfering with the reduction reaction process. Furthermore, the countercurrent contact mode of circulating spraying of the absorbent significantly improves the sufficiency of gas-liquid contact and reaction efficiency, thereby increasing the absorption and conversion rate of iodine vapor. When the iodine ion content of the iodine-containing absorbent reaches the preset threshold, it is transported to the oxidation tank to react with the oxidant to convert iodine ions into elemental iodine. Then, it is sent to a centrifuge to complete solid-liquid separation to obtain the finished elemental iodine product. Throughout the process, foreign impurities such as sulfur residue are avoided from mixing into the reaction materials. The final iodine product obtained by centrifugation has higher purity, eliminating the negative impact of solid impurities on product quality and achieving a dual improvement in iodine recovery efficiency and product purity.

[0034] Please see Figure 2 This application also provides another embodiment of a method for iodine recovery, which includes: S201. The sulfur dioxide gas containing impurities generated by the sulfur incinerator is transported to the buffer tank; In this embodiment, step S201 is similar to step S101 in the previous embodiment, and will not be described again here.

[0035] S202. When sulfur dioxide gas containing impurities enters the buffer tank, the flow rate of the sulfur dioxide gas containing impurities is reduced by the buffer tank so that the solid impurities in the sulfur dioxide gas containing impurities settle to the bottom of the buffer tank under the action of gravity, and the purified sulfur dioxide gas is discharged from the top of the buffer tank. In this embodiment, after the sulfur dioxide gas containing impurities enters the buffer tank, the cross-sectional area of ​​the internal cavity of the buffer tank is much larger than that of the front-end delivery pipeline. This sudden expansion of the airflow space significantly reduces the gas velocity, consequently decreasing the airflow's ability to carry solid particles from the sulfur dioxide gas. Therefore, solid impurities such as sulfur slag, whose density is much greater than that of sulfur dioxide gas, lose the support of the high-speed airflow and gradually settle downwards under their own gravity, accumulating at the bottom of the buffer tank. Meanwhile, the purified sulfur dioxide gas, freed from solid impurities, is discharged from the top exhaust port of the buffer tank and enters the subsequent delivery pipeline. This method utilizes the density difference between solid impurities and the gaseous medium to weaken the airflow's carrying capacity through expansion and deceleration, allowing gravity to become the dominant force for impurity settling.

[0036] S203. The purified sulfur dioxide gas is transported to the SO2 absorption tank to form SO2 absorption liquid; In this embodiment, step S203 is similar to step S102 in the previous embodiment, and will not be described again here.

[0037] S204. The SO2 absorbent is sprayed down from the top of the absorption tower, while iodine vapor is introduced from the bottom of the absorption tower. This allows the SO2 absorbent and iodine vapor to come into countercurrent contact and undergo an oxidation-reduction reaction in the absorption tower, converting the iodine vapor into iodide ions, thus obtaining an absorbent containing iodide ions. In this embodiment, the SO2 absorbent liquid prepared in the SO2 absorption tank is pressurized and transported to the top spray layer of the absorption tower by a transfer pump. After being dispersed into fine droplets by the atomizing nozzles of the top spray layer, it is sprayed down from top to bottom.

[0038] Meanwhile, iodine vapor is introduced from the bottom of the absorption tower and passes through the packing layer inside the absorption tower from bottom to top, forming a countercurrent contact with the downward sprayed absorbent. The gas and liquid phases fully transfer mass on the surface of the packing and undergo a redox reaction. Sulfur dioxide in the absorbent acts as a reducing agent, reducing the iodine vapor in the gas phase to iodide ions and transferring them to the liquid phase. Finally, the iodide-containing absorbent is collected from the bottom of the absorption tower.

[0039] S205. The iodide-containing absorbent is returned to the SO2 absorption tank to continue absorbing the purified sulfur dioxide gas and is then circulated to the absorption tower for reaction. In this embodiment, step S205 is similar to step S104 in the previous embodiment, and will not be described again here.

[0040] S206. Detect the iodine ion content in the iodine ion-containing absorption liquid returned to the SO2 absorption tank; During the circulation of the absorbent, if the iodide ion content is too low, the oxidation reaction efficiency will be low and the oxidant will be wasted. If the iodide ion content is too high, problems such as iodide ion supersaturation and precipitation will occur, affecting the stability of the reaction. Therefore, this embodiment requires periodic sampling and testing. The test object can be the iodide ion-containing absorbent liquid that is returned to the SO2 absorption tank, or the iodide ion-containing absorbent liquid in the return pipeline during the return process.

[0041] Specifically, iodine-containing absorbent is obtained from the reflux to the SO2 absorption tank or the reflux pipeline during the reflux process. The content of iodine ions in the obtained iodine-containing absorbent is detected by the detection equipment, and the upward trend of the iodine ion content with the increase of the number of cycles is monitored.

[0042] S207. When the detected iodine ion content reaches the preset content threshold, stop the circulation of the iodine ion absorption liquid and transfer the iodine ion absorption liquid to the oxidation tank. When the iodine ion content in the iodine ion absorbent reaches a preset threshold, the circulation of the iodine ion absorbent between the SO2 absorption tank and the absorption tower is stopped. The pipeline flow direction is switched, and the iodine ion absorbent that has reached the preset threshold is completely transferred to the oxidation tank via a transfer pump, completing the process transfer of the reactants. Switching processes when the preset threshold is reached ensures both the efficiency of the oxidation reaction and the utilization rate of the oxidant, while also avoiding a decrease in production efficiency due to excessively long circulation times.

[0043] S208. Add an oxidizing agent to the oxidation tank to oxidize the iodide ions in the iodide ion absorption liquid into elemental iodine, and obtain the iodine-containing material.

[0044] In this embodiment, after the iodide-containing absorbent is fed into the oxidation tank, the corresponding oxidant is added to the oxidation tank, and the stirring device in the oxidation tank is started at the same time to make the materials fully mixed. The oxidant and the iodide ions in the iodide-containing absorbent are fully in contact and undergo an oxidation reaction in a uniformly mixed state. The iodide ions lose electrons and are oxidized into elemental iodine, which is precipitated from the iodide-containing absorbent in the form of solid particles and dispersed in the liquid to form a solid-liquid mixed iodine-containing material.

[0045] S209. The iodine-containing material is fed to a centrifuge for solid-liquid separation to obtain the iodine product.

[0046] In this embodiment, step S209 is similar to step S106 in the previous embodiment, and will not be described again here.

[0047] S210. Collect the mother liquor produced after solid-liquid separation; Since the mother liquor after centrifugation still contains trace amounts of iodine ions that have not been completely precipitated, small amounts of unreacted sulfur dioxide components, and other soluble media, it still has a certain degree of absorption and reaction activity and is not a completely worthless waste liquid. Therefore, after the centrifuge completes the solid-liquid separation, the separated mother liquor is collected into the mother liquor collection device through a collection pipeline to complete the centralized collection of the mother liquor after separation, avoiding direct discharge of mother liquor that would cause material waste and environmental burden.

[0048] S211. The mother liquor is returned to the SO2 absorption tank and continues to participate in the absorption process of purified sulfur dioxide gas in the SO2 absorption tank to form SO2 absorption liquid, so as to realize the recycling of materials.

[0049] In this embodiment, the collected mother liquor is returned to the SO2 absorption tank through a return pipeline to replace part of the fresh absorption medium. As a component of the absorption liquid, it continues to participate in the dissolution and absorption process of the purified sulfur dioxide gas in the SO2 absorption tank, replenishing the liquid phase volume in the system. The small amount of residual components in the mother liquor can also participate in subsequent recycling reactions.

[0050] By returning the collected mother liquor to the SO2 absorption tank for recycling, the utilization rate of the liquid medium can be greatly improved, the amount of fresh absorbent liquid to be replenished can be reduced, and the material costs and environmental pressure of production can be further reduced.

[0051] In an optional embodiment, when there is residual SO2 absorbent in the SO2 absorption tank and / or iodine-containing absorbent that has been returned to the SO2 absorption tank, newly supplied purified sulfur dioxide gas is introduced into the SO2 absorption tank to mix with the liquid already present in the SO2 absorption tank, so as to continue to participate in the absorption process.

[0052] When there is residual SO2 absorbent that has not been completely discharged in the SO2 absorption tank, or iodine-containing absorbent that has been returned from the absorption tower, these absorbents are not emptied. Instead, newly supplied purified sulfur dioxide gas is continuously introduced into the SO2 absorption tank, allowing the newly introduced gas to fully contact and mix with the absorbent already present in the tank. Sulfur dioxide is continuously dissolved and replenished into the liquid phase, replenishing the reducing agent components consumed in the reaction. This ensures that the liquid in the SO2 absorption tank maintains its reducing and absorption activity and continues to participate in the subsequent cyclic reaction process transported to the absorption tower.

[0053] In one optional embodiment, the buffer tank is provided with an air inlet, an air outlet, and a slag discharge outlet; The air inlet is located in the lower middle part of the buffer tank, and a guide baffle with a tangential air inlet structure is provided at the air inlet to prolong the residence time of sulfur dioxide gas containing impurities in the buffer tank. The outlet is located at the top of the buffer tank and is used to discharge the purified sulfur dioxide gas; The slag discharge port is located at the bottom of the buffer tank and is used to discharge solid impurities that have settled to the bottom.

[0054] In this embodiment, the buffer tank is provided with an air inlet, an air outlet, and a slag discharge port. The sulfur dioxide gas containing impurities enters from the air inlet located in the lower middle part of the buffer tank. The guide baffle of the tangential air inlet structure at the air inlet guides the airflow to spiral and rotate along the inner wall of the tank, which greatly prolongs the flow path and residence time of the sulfur dioxide gas containing impurities in the buffer tank. Under the combined action of centrifugal force and gravity, these impurities gradually move towards the tank wall and bottom and settle.

[0055] After impurities are removed, the sulfur dioxide gas flows upward along the buffer tank, is discharged from the gas outlet at the top, and is transported to the subsequent process. Meanwhile, the solid impurities that settle and accumulate at the bottom of the buffer tank are periodically discharged from the tank through the slag discharge port at the bottom of the buffer tank.

[0056] Please see Figure 3 This application also provides an embodiment of an iodine recovery apparatus, which includes: The buffer tank 301 is provided with an air inlet and an air outlet. The air inlet is used to receive sulfur dioxide gas containing impurities, and the buffer tank 301 is used to remove solid impurities from the sulfur dioxide gas containing impurities by gravity settling. The SO2 absorption tank 302 is equipped with a gas inlet and a liquid outlet. The gas inlet is connected to the gas outlet of the buffer tank 301 and is used to absorb purified sulfur dioxide gas to form SO2 absorption liquid. The absorption tower 303 is equipped with a spray inlet, a gas inlet and a liquid outlet. The spray inlet is connected to the liquid outlet of the SO2 absorption tank 302. The liquid outlet of the absorption tower 303 is connected to the SO2 absorption tank 302 through a reflux pipeline. The gas inlet of the absorption tower 303 is used to introduce iodine vapor so that the iodine vapor and the SO2 absorbent can undergo an oxidation-reduction reaction in the absorption tower 303 to obtain an iodine-containing absorbent. Oxidation tank 304 is equipped with a liquid inlet and a discharge outlet. The liquid inlet is connected to the liquid outlet of SO2 absorption tank 302 or absorption tower 303. It is used to oxidize iodine ions in iodine-containing absorption liquid to obtain iodine-containing material. Centrifuge 305 is equipped with a feed inlet, a solid phase outlet and a liquid phase outlet. The feed inlet is connected to the discharge outlet of oxidation tank 304 and is used for solid-liquid separation of oxidized iodine-containing materials.

[0057] In this embodiment, the inlet of the buffer tank 301 is connected to the sulfur dioxide gas containing impurities generated by the sulfur incinerator, and the outlet is connected to the gas inlet of the SO2 absorption tank 302. The purified gas can be directly sent into the absorption tank. The liquid outlet of the SO2 absorption tank 302 is connected to the spray inlet at the top of the absorption tower 303 via a transfer pump. The liquid outlet at the bottom of the absorption tower 303 is connected back to the SO2 absorption tank 302 via a return pipeline. The gas inlet at the bottom of the absorption tower 303 is used to introduce iodine vapor to be treated. The liquid inlet of the oxidation tank 304 can be switched to connect to the liquid outlet of the absorption tank or the absorption tower 303. The discharge outlet is connected to the feed inlet of the centrifuge 305. The centrifuge 305 is provided with a solid phase outlet and a liquid phase outlet to discharge the iodine elemental product and the mother liquor, respectively.

[0058] During operation, sulfur dioxide gas containing impurities first undergoes gravity settling in buffer tank 301 to remove solid impurities such as sulfur slag. The purified gas then enters SO2 absorption tank 302 to dissolve and form SO2 absorbent liquid. The SO2 absorbent liquid is then sprayed at the top of absorption tower 303, where it comes into countercurrent contact with iodine vapor introduced from the bottom, undergoing a redox reaction to convert the iodine vapor into iodide ions. The resulting iodide-containing absorbent liquid is then returned to SO2 absorption tank 302 for further enrichment. Once the iodide ion content in the absorbent liquid reaches the standard, it is sent to oxidation tank 304 to react with an oxidant, precipitating elemental iodine and obtaining elemental iodine material. This material is then transported to centrifuge 305 to complete solid-liquid separation.

[0059] In an optional embodiment, the buffer tank 301 is further provided with a slag discharge port; The air inlet is located in the lower middle part of the buffer tank 301, the air outlet is located at the top of the buffer tank 301, and the slag discharge port is located at the bottom of the buffer tank 301. The buffer tank 301 is equipped with a flow guide baffle to form a gravity settling zone within the buffer tank 301.

[0060] In this embodiment, the air inlet is located in the lower middle part of the buffer tank 301, the air outlet is located at the top of the buffer tank 301, and the slag discharge port is located at the bottom of the buffer tank 301. A flow guide baffle is provided inside the buffer tank 301 corresponding to the air inlet position, which can divide a stable gravity settling zone inside the buffer tank 301.

[0061] In practical applications, the inlet receives sulfur dioxide gas containing impurities from the sulfur incinerator, the outlet connects to the gas inlet of the subsequent SO2 absorption tank 302, and the slag discharge port is connected to a slag discharge pipeline with a valve. The sulfur dioxide gas containing impurities enters the buffer tank 301 from the lower middle part. The guide baffle blocks and guides the airflow to change direction, avoiding a short circuit caused by the airflow going straight in and out. This effectively prolongs the residence time of the sulfur dioxide gas containing impurities in the buffer tank 301. After the airflow velocity is further reduced, solid impurities such as sulfur slag gradually settle to the bottom of the tank under the action of gravity. The purified gas flows upward and is discharged from the top outlet. The settled and accumulated solid impurities are periodically discharged through the bottom slag discharge port.

[0062] In an optional embodiment, a content detector and a control valve are provided on the reflux line; The content analyzer is used to detect the content of iodine ions in the iodine ion absorption liquid in the reflux pipeline or SO2 absorption tank 302; The control valve is connected to the content detector and is used to cut off the reflux pipeline and divert the liquid in the SO2 absorption tank 302 or the liquid in the absorption tower 303 to the oxidation tank 304 when the iodide ion content reaches the preset content threshold.

[0063] In this embodiment, a content detector and a control valve are installed on the reflux pipeline from the absorption tower 303 to the SO2 absorption tank 302. The detection end of the content detector is connected to the reflux pipeline or extends into the SO2 absorption tank 302, allowing real-time acquisition of iodine ion content data in the liquid. The control valve is communicatively connected to the content detector, and its pipeline path corresponds to two flow directions: reflux to the SO2 absorption tank 302 and flow to the oxidation tank 304.

[0064] During cyclic operation, the content detector continuously monitors the content of iodide ion-containing absorbent, and the control valve keeps the return pipeline unobstructed. The iodide ion-containing absorbent continuously circulates between the absorption tower 303 and the SO2 absorption tank 302, constantly enriching iodide ions. When the iodide ion content in the iodide ion-containing absorbent reaches the preset content threshold, the control valve automatically performs a switching action, cutting off the return path to the SO2 absorption tank 302 and opening the branch leading to the oxidation tank 304, diverting the qualified absorbent from the SO2 absorption tank 302 or the absorption tower 303 into the oxidation tank 304.

[0065] It should be noted that the above description of the disclosed embodiments enables those skilled in the art to implement or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for iodine recovery, characterized in that, include: The sulfur dioxide gas containing impurities generated by the sulfur incinerator is transported to a buffer tank, where solid impurities are removed by gravity settling to obtain purified sulfur dioxide gas. The purified sulfur dioxide gas is transported to an SO2 absorption tank to form an SO2 absorption liquid; The SO2 absorbent is transported to the top of the absorption tower for spraying and undergoes an oxidation-reduction reaction with iodine vapor to convert the iodine vapor into iodide ions, thus obtaining an iodide-containing absorbent. The iodine-containing absorbent is returned to the SO2 absorption tank to continue absorbing the purified sulfur dioxide gas and is then circulated to the absorption tower for reaction. When the iodine ion content in the iodine ion absorption liquid reaches a preset content threshold, the iodine ion absorption liquid is transported to an oxidation tank to react with an oxidant, so that the iodine ions are converted into elemental iodine, and iodine-containing material is obtained. The iodine-containing material is fed into a centrifuge for solid-liquid separation to obtain the iodine product.

2. The method according to claim 1, characterized in that, The process of removing solid impurities from the sulfur dioxide gas containing impurities by gravity settling within the buffer tank to obtain purified sulfur dioxide gas includes: When the sulfur dioxide gas containing impurities enters the buffer tank, the flow rate of the sulfur dioxide gas containing impurities is reduced by the buffer tank, so that the solid impurities in the sulfur dioxide gas containing impurities settle to the bottom of the buffer tank under the action of gravity, and the purified sulfur dioxide gas is discharged from the top of the buffer tank.

3. The method according to claim 2, characterized in that, The buffer tank is equipped with an air inlet, an air outlet, and a slag discharge outlet; The air inlet is located in the lower middle part of the buffer tank, and a guide baffle with a tangential air inlet structure is provided at the air inlet to prolong the residence time of the sulfur dioxide gas containing impurities in the buffer tank. The outlet is located at the top of the buffer tank and is used to discharge the purified sulfur dioxide gas; The slag discharge port is located at the bottom of the buffer tank and is used to discharge the solid impurities that have settled to the bottom.

4. The method according to claim 1, characterized in that, The step of conveying the SO2 absorbent liquid to the top of the absorption tower for spraying and reacting it with iodine vapor in a redox reaction includes: The SO2 absorbent is sprayed down from the top of the absorption tower, while iodine vapor is introduced from the bottom of the absorption tower, so that the SO2 absorbent and the iodine vapor come into countercurrent contact and undergo an oxidation-reduction reaction in the absorption tower.

5. The method according to claim 1, characterized in that, When the iodine ion content in the iodine ion-containing absorbent reaches a preset content threshold, the iodine ion-containing absorbent is transported to an oxidation tank to react with an oxidant, converting the iodine ions into elemental iodine, thereby obtaining an iodine-containing material, including: The content of iodine ions in the iodine-containing absorption solution returned to the SO2 absorption tank is detected; When the detected iodine ion content reaches a preset content threshold, the circulation of the iodine ion-containing absorbent is stopped, and the iodine ion-containing absorbent is transported to the oxidation tank. An oxidizing agent is added to the oxidation tank to oxidize the iodide ions in the iodide-containing absorption liquid into elemental iodine, thereby obtaining an iodine-containing material.

6. The method according to claim 1, characterized in that, The method further includes: When there is residual SO2 absorbent in the SO2 absorption tank and / or iodine-containing absorbent that has been returned to the SO2 absorption tank, the newly supplied purified sulfur dioxide gas is introduced into the SO2 absorption tank to mix with the liquid already present in the SO2 absorption tank, so as to continue to participate in the absorption process.

7. The method according to any one of claims 1 to 6, characterized in that, After conveying the iodine-containing material to a centrifuge for solid-liquid separation to obtain the iodine product, the method further includes: Collect the mother liquor produced after solid-liquid separation; The mother liquor is returned to the SO2 absorption tank and continues to participate in the absorption process of the purified sulfur dioxide gas in the SO2 absorption tank to form the SO2 absorption liquid, thereby realizing the recycling of materials.

8. An iodine recovery device, characterized in that, include: A buffer tank is provided with an air inlet and an air outlet. The air inlet is used to receive sulfur dioxide gas containing impurities, and the buffer tank is used to remove solid impurities from the sulfur dioxide gas containing impurities by gravity settling. The SO2 absorption tank is equipped with a gas inlet and a liquid outlet. The gas inlet is connected to the gas outlet of the buffer tank and is used to absorb purified sulfur dioxide gas to form SO2 absorption liquid. The absorption tower is equipped with a spray inlet, a gas inlet, and a liquid outlet. The spray inlet is connected to the liquid outlet of the SO2 absorption tank. The liquid outlet of the absorption tower is connected to the SO2 absorption tank through a reflux pipeline. The gas inlet of the absorption tower is used to introduce iodine vapor so that the iodine vapor reacts with the SO2 absorbent in the absorption tower to obtain an iodine-containing absorbent. An oxidation tank is provided with an inlet and an outlet. The inlet is connected to the liquid outlet of the SO2 absorption tank or the absorption tower. It is used to oxidize iodine ions in the iodine-containing absorption liquid to obtain iodine-containing material. The centrifuge is equipped with a feed inlet, a solid phase outlet, and a liquid phase outlet. The feed inlet is connected to the discharge outlet of the oxidation tank and is used for solid-liquid separation of the oxidized iodine-containing material.

9. The apparatus according to claim 8, characterized in that, The buffer tank is also equipped with a slag discharge port; The air inlet is located in the lower middle part of the buffer tank, the air outlet is located at the top of the buffer tank, and the slag discharge port is located at the bottom of the buffer tank. The buffer tank is equipped with a flow guide baffle to form a gravity settling zone within the buffer tank.

10. The apparatus according to claim 9, characterized in that, The reflux pipeline is equipped with a content detector and a control valve; The content detector is used to detect the content of iodine ions in the iodine-containing absorption liquid in the reflux pipeline or the SO2 absorption tank; The control valve is communicatively connected to the content detector and is used to cut off the reflux pipeline and divert the liquid in the SO2 absorption tank or the liquid in the absorption tower to the oxidation tank when the iodide ion content reaches a preset content threshold.

Images