A process for extracting bromide ions from brine using the flue gas method

Abstract

The present application relates to the technical field of extracting sodium bromide in high nitrate concentrate, and particularly relates to a process for extracting bromide ions in brine by using flue gas method. The content of bromide ions in high nitrate concentrate produced by evaporation salt system is high, and the high nitrate concentrate is directly reused to the evaporation salt system. In the evaporation and crystallization concentration process of industrial salt, the residual content of bromide ions is high, which seriously affects the quality of industrial salt. In view of the above problems, the present application provides a production process for comprehensive salt production and nitrate production by using high nitrate brine. In the process, compressed flue gas is used to blow Br2 in the solution in the hot blowing tank, and the efficiency is high. In addition to having high gas pressure, the flue gas also has high temperature heat, which makes it easier to separate Br2 in the hot blowing tank from the solution, greatly improving the bromine removal efficiency of the high nitrate concentrate.

Description

Technical Field

[0001] This invention relates to the field of sodium bromide extraction technology from high-nitrate concentrates, specifically to a process for extracting bromide ions from brine using flue gas extraction. Background Technology

[0002] In evaporative salt production systems, after sodium chloride is precipitated from the salt solution through evaporation and crystallization, the remaining high-nitrate concentrate contains a large amount of unseparated impurities. Due to the mother liquor's cyclical concentration characteristics, the content of bromide ions (Br⁻), sulfate ions (SO₂⁻), and other impurities in this concentrate is 20-30 times higher than in the original salt system. Current processes typically treat this high-nitrate concentrate in two ways: one is by directly reusing it back into the salt production system, but long-term circulation leads to the continuous accumulation of bromide ions within the system, which in turn causes sodium bromide (NaBr) to co-precipitate with industrial salt during subsequent crystallization, severely affecting the purity of the finished salt; the other is by direct discharge, however, the discharge of high-concentration bromine (in the form of Br⁻) not only results in a huge waste of bromine resources but may also pose environmental risks, especially the potential harm to aquatic ecosystems, which cannot be ignored.

[0003] Currently, there is a lack of technologies for the efficient separation and recovery of bromide ions from high-nitrate concentrates, as well as for the comprehensive utilization of these concentrates. While traditional salt chemical processes exist for bromine extraction (such as air blowing and ion exchange), these methods are primarily suited to low-salinity, low-impurity environments, and involve high equipment investment and operating costs, making them unsuitable for the complex high-salinity, high-impurity systems of high-nitrate concentrates. Furthermore, the competitive separation of sulfate and bromide ions in the concentrate remains a challenge, and existing technologies cannot achieve selective extraction of bromide ions and material balance in industrial salt systems under low-cost conditions.

[0004] Therefore, developing an integrated process that can effectively separate bromide ions from high-nitrate concentrates, avoid enrichment within the system, and simultaneously achieve bromine resource recovery and harmless reuse of the concentrate has become a critical technical bottleneck that urgently needs to be addressed in the field of clean production and efficient resource utilization of industrial salt. Summary of the Invention

[0005] The problem with existing technologies is that the high-nitrate concentrate produced by the evaporation salt production system has a high bromide ion content. Direct reuse in the evaporation salt production system results in high residual bromide ions during the evaporation, crystallization, and concentration process of industrial salt, severely affecting the quality of the industrial salt. To address these problems, this invention provides a comprehensive salt production process using high-nitrate brine, comprising the following steps:

[0006] (1) The bromide ions in the high-nitrate concentrate in the mother liquor concentration tank are converted into Br2 by chemical reaction in the reaction tank 1 (by adding sodium hypochlorite and hydrochloric acid as chemical reaction conversion agents to the reaction tank 1). The gas at the top of the reaction tank 1 enters the Br2 absorption system, and the liquid in the reaction tank 1 is pumped into the hot blowing tank from the liquid inlet opened on the side wall of the hot blowing tank.

[0007] (2) The liquid inlet on the side wall of the hot blowing tank is located above the maximum set liquid level of the hot blowing tank. The gas above the liquid surface of the hot blowing tank is purged by the second gas purging of the purification flue and enters the Br2 absorption system through the gas outlet on the side wall of the hot blowing tank located above the maximum set liquid level of the hot blowing tank. When the liquid height in the hot blowing tank reaches the maximum set liquid level, the liquid at the bottom of the hot blowing tank is pumped into the residual bromine treatment system. At the same time, the liquid level in the hot blowing tank is always not lower than the liquid level corresponding to 40% of the maximum effective volume of the hot blowing tank. The maximum set liquid level of the hot blowing tank does not exceed the liquid level corresponding to 75% of the maximum effective volume of the hot blowing tank.

[0008] (3) The gas entering the Br2 absorption system reacts with the Br2 absorption liquid to obtain a sodium bromide solution, and the sodium bromide solution is evaporated and crystallized to obtain sodium bromide crystals;

[0009] (4) The liquid entering the residual bromine treatment system is transferred to the concentrate tank after being treated by the purified flue gas. The liquid in the concentrate tank is reused in the evaporation salt production system.

[0010] (5) The gas in the Br2 absorption system and the residual bromine treatment system is discharged into the air after being treated by the tail gas absorption system.

[0011] Preferably, the Br2 absorption system includes a second reaction tank, a third reaction tank, a seventh reaction tank, and a Br2 absorbent tank. The Br2 absorbent tank continuously pumps Br2 absorbent into the second reaction tank. When the liquid level in the second reaction tank reaches its maximum set level, the liquid in the second reaction tank is pumped into the third reaction tank. Simultaneously, the absorbent in the Br2 absorbent tank is pumped into the third reaction tank at the same flow rate. When the liquid level in the third reaction tank reaches its maximum set level, the liquid in the third reaction tank overflows into the seventh reaction tank. When the liquid level in the seventh reaction tank reaches its maximum set level, the liquid in the seventh reaction tank is emptied from the bottom. The liquid inside is pumped into the evaporator crystallizer for evaporation and crystallization to obtain sodium bromide. The liquid level in reaction tanks 2, 3, and 7 shall not be lower than the liquid level corresponding to 30% of the maximum effective volume of the corresponding tank. The maximum set liquid level in reaction tanks 2, 3, and 7 shall not exceed the liquid level corresponding to 80% of the maximum effective volume of the corresponding tank. The gas above the liquid surface in reaction tank 7 enters the tail gas absorption system through a pipe. The gas entering the Br2 absorption system enters the Br2 absorption system through an independent gas pipe that connects to the top of reaction tank 2 and extends to the bottom of reaction tank 2.

[0012] Preferably, the purified flue gas is connected to the top of the hot blowing tank through a pipe, and the gas inside the hot blowing tank is purged from the top of the hot blowing tank downwards.

[0013] Preferably, the residual bromine treatment system includes reaction tank four, reaction tank five, and reaction tank six. Liquid from the bottom of the hot blowing tank is pumped into reaction tank four through a pipeline. Liquid in reaction tank four overflows into reaction tank five, and liquid in reaction tank five overflows into reaction tank six. When the liquid level in reaction tank four and reaction tank five is not lower than the liquid level corresponding to 30% of the maximum effective volume of the corresponding tank, purified flue gas one is introduced into reaction tank four and reaction tank five respectively. Purified flue gas one is introduced upward from the vent at the bottom of the reaction tank. Finally, the liquid in reaction tank six is ​​transferred to the concentrate tank. The overflow liquid level of reaction tank four and reaction tank five does not exceed the liquid level corresponding to 80% of the maximum effective volume of the corresponding tank. The gas above reaction tank four, reaction tank five, and reaction tank six enters the tail gas treatment system through the gas outlet at the top of the corresponding reaction tank.

[0014] Preferably, the liquid in reaction vessel six is ​​transferred to a concentrate tank via a liquid transfer pump.

[0015] Preferably, the exhaust gas absorption system includes exhaust gas absorption device one, exhaust gas absorption device two, exhaust gas absorption device three, and a lime slurry tank. The lime slurry tank continuously pumps lime slurry into exhaust gas absorption device one. When the liquid level in exhaust gas absorption device one reaches the maximum set level, the liquid in exhaust gas absorption device one and the lime slurry in the lime slurry tank are pumped into exhaust gas absorption device two at the same flow rate. When the liquid level in exhaust gas absorption device two reaches the maximum set level, the liquid in exhaust gas absorption device two and the lime slurry in the lime slurry tank are pumped into exhaust gas absorption device three at the same flow rate. When the liquid level in exhaust gas absorption device three reaches the maximum set level... When in position, the liquid overflowing from the third exhaust gas absorption device enters the lime slurry overflow tank or overflows to the outside. The gas above the liquid surface in the third exhaust gas absorption device is directly vented. The gas entering the exhaust gas absorption system enters the exhaust gas absorption system through an independent pipe connected to the first exhaust gas absorption device and extending to the bottom of the first exhaust gas absorption device. The gas above the liquid surface in the first exhaust gas absorption device enters the second exhaust gas absorption device through a gas pipe connected to the top of the second exhaust gas absorption device and extending to the bottom of the second exhaust gas absorption device. The gas above the liquid surface in the second exhaust gas absorption device enters the third exhaust gas absorption device through a gas pipe connected to the top of the third exhaust gas absorption device and extending to the bottom of the third exhaust gas absorption device.

[0016] Preferably, the high-nitrate concentrate in the mother liquor concentration tank comes from the evaporation salt production system, and the high-nitrate concentrate has a pH of 10-11.5 and a temperature of 40-80℃, and includes the following main components:

[0017] NaCl: 275~295g / L, SO4 2-40~52g / L, Br - 300~1200 mg / L, OH - 0.05~0.3g / L, CO3 2- 1.0-3.6 g / L, Ca 2+ 2.0~6.0 mg / L, Mg 2+ : 0.5~3.0mg / L.

[0018] Preferably, the Br2 absorbent is a mixture of urea, sodium carbonate and water, with the mass concentration of urea being 10-12% and the molar ratio of sodium carbonate to urea being 3.8:1 to 4.6:1.

[0019] Preferably, the first purified flue gas is the flue gas generated from coal-fired power generation after removing nitrogen oxides, and the second purified flue gas is the compressed flue gas after removing sulfur oxides from the first purified flue gas.

[0020] In the above process, the reaction principle inside the reaction vessel is as follows:

[0021] ClO - + 2Br - + 2H + → Cl - + Br2+ H2O

[0022] ClO - + Cl - + 2H + → Cl2+ H2O

[0023] Cl2+ 2Br - → 2Cl - + Br2

[0024] The reaction principle inside reaction vessel two is as follows:

[0025] 3Br2+ 3Na2CO3+ NH2CONH2→ 6NaBr+ 4CO2↑+ N2↑+ 2H2O

[0026] The reaction principles inside reaction vessels four and five are as follows:

[0027] SO2 + 2H2O + Br2 → H2SO4 + 2HBr

[0028] Reaction vessel six: The pH of the liquid in the vessel is adjusted to ≥7.5 using caustic soda or lime slurry. The principle of adjusting the reaction using lime slurry is as follows:

[0029] H₂SO₄ + Ca(OH)₂ → CaSO₄ + 2H₂O

[0030] 2HBr + Ca(OH)₂ → CaBr₂ + 2H₂O

[0031] In the above process, the flue gas produced by coal-fired power generation mainly consists of N2, O2, CO2, SOx, and NO. X Dust, moisture, and heat are removed from the flue gas. The first step in purifying flue gas from coal-fired power plants is to remove NOx from the flue gas through a nitrogen oxide removal device. X The gas obtained after dust removal is treated with a nitrogen oxide removal device that uses ammonia as a reducing agent to remove NO from the flue gas. X The gas obtained after reduction to N2 and water has a denitrification rate of 85-92%. The reduction reaction is as follows:

[0032] 4NH3 + 4NO + O2 = 4N2 + 6H2O;

[0033] 4NH3 + 2NO2 + O2 = 3N2 + 6H2O;

[0034] The main components of the purified flue gas are N2, O2, CO2, and SOx (600-950 mg / m³). 3 (800-1400mg / m²) 3 ), moisture, heat (95-135℃), heat after flue gas cooling (78-88℃), trace NO X .

[0035] Purified flue gas II is the gas obtained after purified flue gas I has undergone desulfurization and deoxidation to remove SOx and dust, and compression. The main components of purified flue gas II are N2, O2, CO2, moisture, heat (56-75℃), and trace amounts of NO. X (20-45mg / m 3 ) and SOx (20-45 mg / m²) 3 The desulfurization of oxides uses a wet desulfurization process with calcium carbonate, which mainly converts SO2 into calcium sulfate through three steps: absorption, neutralization, and oxidation. The specific steps are as follows:

[0036] Absorption: SO2 + H2O → H2SO3;

[0037] Neutralization: CaCO3 + H2SO3 → CaSO3 + CO2↑ + H2O;

[0038] Oxidation: 2CaSO3 + O2 → 2CaSO4↓;

[0039] The function of the compression device is to further purify the flue gas to obtain purified flue gas II, which removes trace amounts of SOx and NO from the flue gas. X The main components of the purified flue gas are N2, O2, CO2, and heat (55-65℃).

[0040] The present invention has the following beneficial effects:

[0041] (1) At room temperature, compressed air is used to blow Br2 into the solution of high nitrate concentrate after reaction with hydrochloric acid and sodium hypochlorite. The efficiency is very low. Only about 40% of the Br2 in the solution is separated into the second reaction tank. The solution obtained in the fourth reaction tank still contains a high concentration of bromide ions. If it is directly reused in the evaporation salt production system, it will still significantly affect the quality of industrial salt. In this invention, compressed flue gas is used to blow Br2 into the solution in the hot blowing tank. The efficiency is higher. In addition to having a high gas pressure, flue gas also has a high temperature (55-65℃), which makes it easier to blow Br2 in the hot blowing tank into the second reaction tank, greatly improving the bromine removal efficiency.

[0042] (2) Conventional methods all use sodium hydroxide aqueous solution to absorb Br2. In addition to generating sodium bromide, sodium bromate is also generated. The crystals of sodium bromide and sodium bromate are difficult to separate and the separation energy consumption is high. However, the present invention uses a mixture of urea, sodium carbonate and water as the Br2 absorption liquid. The reaction product is only sodium bromide. Pure sodium bromide crystals, a high-value byproduct, can be easily obtained through a simple evaporation crystallization process. The principle involved is as follows:

[0043] 3Br2+6NaOH→5NaBr+NaBrO3+3H2O;

[0044] 3Br2+3Na2CO3+NH2CONH2→6NaBr+4CO2↑+N2↑+2H2O;

[0045] (3) After removing bromide ions from the high-nitrate concentrate using the process of this invention, a high-nitrate liquid is obtained with a bromide extraction rate (%) ≥98%. The concentration of bromide ions in the liquid in the concentrate tank is less than 15 mg / L. The high-nitrate and high-salt liquid in the concentrate tank is effectively utilized, saving costs. This solves the problem of continuous enrichment of bromide ions in the evaporation salt production system caused by long-term recycling of high-nitrate liquid containing bromide. This effectively avoids co-precipitation of NaBr with industrial salt in the subsequent crystallization process. While avoiding resource waste, it effectively ensures the quality of salt.

[0046] (4) In addition to producing steam and electricity, thermal power plants also generate a large amount of flue gas. The main components of flue gas are N2, O2, and NO. X SO X Flue gas, including CO2, H2O, and heat, is directly emitted into the atmosphere, causing environmental pollution and wasting resources and energy. Currently, the utilization efficiency of flue gas is low. Applying flue gas from thermal power plants to the bromine extraction process of this invention improves the efficiency of bromine removal, saves energy, and reduces the environmental impact of flue gas. Attached Figure Description

[0047] Figure 1 This is a schematic diagram of a process for extracting bromide ions from brine using a flue gas method, provided by the present invention. Detailed Implementation

[0048] The present invention will be described in detail below with reference to embodiments. However, it should be understood that the following embodiments are merely illustrative examples of implementation of the present invention and are not intended to limit the scope of the present invention.

[0049] like Figure 1 The diagram shown is a schematic of a process for extracting bromide ions from brine using a flue gas extraction method, provided by the present invention. The steps of the process for extracting bromide ions from brine using a flue gas extraction method are as follows:

[0050] (1) Pump the high-nitrate concentrate in the mother liquor concentration tank into the reaction tank one, add hydrochloric acid and sodium hypochlorite with a mass concentration of 30% into the reaction tank one, so that the pH of the solution in the reaction tank one is 2-3, so that the molar ratio of sodium hypochlorite to bromide ions in the solution in the reaction tank one is 1-6:1, so that the bromide ions in the high-nitrate concentrate are chemically converted into Br2 in the reaction tank one, the gas at the top of the reaction tank one enters the Br2 absorption system, and the liquid in the reaction tank one is pumped into the hot blowing tank from the liquid inlet opened on the side wall of the hot blowing tank.

[0051] (2) The liquid inlet on the side wall of the hot blowing tank is located above the maximum set liquid level of the hot blowing tank. The gas above the liquid surface of the hot blowing tank passes through the second purified flue gas (gas flow rate of 30~55m). 3 The gas flow rate is 0.18~0.35Mpa, and the flue gas purification device used can be the flue gas desulfurization tower reported in Chinese Utility Model Patent CN212369907U. The purging gas enters the Br2 absorption system through the outlet on the side wall of the hot blowing tank, which is located above the maximum set liquid level of the hot blowing tank. When the liquid level in the hot blowing tank reaches the maximum set liquid level, the liquid at the bottom of the hot blowing tank is pumped into the residual bromine treatment system. At the same time, the liquid level in the hot blowing tank is always kept at the liquid level corresponding to 40% of the maximum effective volume of the hot blowing tank. The maximum set liquid level of the hot blowing tank is the liquid level corresponding to 75% of the maximum effective volume of the hot blowing tank.

[0052] (3) The gas entering the Br2 absorption system reacts with the Br2 absorption liquid to obtain a sodium bromide solution, and the sodium bromide solution is evaporated and crystallized to obtain sodium bromide crystals;

[0053] (4) The liquid entering the residual bromine treatment system is transferred to the concentrate tank after being treated by the purified flue gas. The liquid in the concentrate tank is reused in the evaporation salt production system.

[0054] (5) The gas in the Br2 absorption system and the residual bromine treatment system is discharged into the air after being treated by the tail gas absorption system.

[0055] In one specific embodiment, the Br2 absorption system includes reaction tank two, reaction tank three, reaction tank seven, and a Br2 absorption liquid tank. The Br2 absorption liquid tank continuously pumps Br2 absorption liquid into reaction tank two. When the liquid level in reaction tank two reaches its maximum set level, the liquid in reaction tank two is pumped into reaction tank three. Simultaneously, the absorption liquid in the Br2 absorption liquid tank is pumped into reaction tank three at the same flow rate. When the liquid level in reaction tank three reaches its maximum set level, the liquid in reaction tank three overflows into reaction tank seven. When the liquid level in reaction tank seven reaches its maximum set level, the liquid overflows from the bottom of reaction tank seven. The liquid in reaction tank 7 is pumped into an evaporator crystallizer for evaporation and crystallization to obtain sodium bromide. The liquid level in reaction tanks 2, 3, and 7 is the liquid level corresponding to 30% of the maximum effective volume of the corresponding tank. The maximum set liquid level in reaction tanks 2, 3, and 7 is the liquid level corresponding to 80% of the maximum effective volume of the corresponding tank. The gas above the liquid surface in reaction tank 7 enters the tail gas absorption system through a pipe. The gas entering the Br2 absorption system enters the Br2 absorption system through an independent gas pipe that connects to the top of reaction tank 2 and extends to the bottom of reaction tank 2.

[0056] In one specific embodiment, the purified flue gas is connected to the top of the hot blowing tank through a pipe, and the gas inside the hot blowing tank is purged from the top of the hot blowing tank downwards.

[0057] In one specific embodiment, the residual bromine treatment system includes reaction tank four, reaction tank five, and reaction tank six. Liquid from the bottom of the hot blowing tank is pumped into reaction tank four through a pipeline. Liquid in reaction tank four overflows into reaction tank five, and liquid in reaction tank five overflows into reaction tank six. When the liquid level in reaction tank four and reaction tank five is not lower than the liquid level corresponding to 30% of the maximum effective volume of the corresponding tank, purified flue gas one (gas flow rate of 30~55m³) is introduced into reaction tank four and reaction tank five respectively. 3 The gas flow rate is 0.18~0.35 MPa. The purified flue gas is introduced upwards through the vent at the bottom of the reaction tank. Finally, the liquid in reaction tank 6 is transferred to the concentrate tank. The overflow liquid level of reaction tanks 4 and 5 does not exceed the liquid level height corresponding to 80% of the maximum effective volume of the corresponding tank. The gas above the liquid surface of reaction tanks 4, 5 and 6 enters the exhaust gas treatment system through the gas outlet at the top of the corresponding reaction tanks.

[0058] In one specific embodiment, the liquid in reaction vessel six is ​​transferred to a concentrate tank via a liquid transfer pump.

[0059] In one specific embodiment, the exhaust gas absorption system includes exhaust gas absorption device one, exhaust gas absorption device two, exhaust gas absorption device three, and a lime slurry tank. The lime slurry tank continuously pumps lime slurry into exhaust gas absorption device one. When the liquid level in exhaust gas absorption device one reaches the maximum set level, the liquid in exhaust gas absorption device one and the lime slurry in the lime slurry tank are pumped into exhaust gas absorption device two at the same flow rate. When the liquid level in exhaust gas absorption device two reaches the maximum set level, the liquid in exhaust gas absorption device two and the lime slurry in the lime slurry tank are pumped into exhaust gas absorption device three at the same flow rate. When the liquid level in exhaust gas absorption device three reaches the maximum set level... When the liquid level is set, the liquid overflowing from the third tail gas absorption device enters the lime slurry overflow tank or overflows to the outside. The gas above the liquid surface of the third tail gas absorption device is directly vented. The gas entering the tail gas absorption system enters the tail gas absorption system through an independent pipe connected to the first tail gas absorption device and extending to the bottom of the first tail gas absorption device. The gas above the liquid surface of the first tail gas absorption device enters the second tail gas absorption device through a gas pipe connected to the top of the second tail gas absorption device and extending to the bottom of the second tail gas absorption device. The gas above the liquid surface of the second tail gas absorption device enters the third tail gas absorption device through a gas pipe connected to the top of the third tail gas absorption device and extending to the bottom of the third tail gas absorption device.

[0060] In one specific embodiment, the high-nitrate concentrate in the mother liquor concentration tank comes from the evaporation salt production system. The high-nitrate concentrate has a pH of 10-11.5 and a temperature of 40-80°C, and includes the following main components:

[0061] NaCl: 275~295g / L, SO4 2- 40~52g / L, Br - 300~1200 mg / L, OH - 0.05~0.3g / L, CO3 2- 1.0-3.6 g / L, Ca 2+ 2.0~6.0 mg / L, Mg 2+ : 0.5~3.0mg / L.

[0062] In one specific embodiment, the Br2 absorbent is a mixture of urea, sodium carbonate and water, with the mass concentration of urea being 10-12% and the molar ratio of sodium carbonate to urea being 3.8:1 to 4.6:1.

[0063] In one specific embodiment, the first purified flue gas is the flue gas generated by coal-fired power generation after removing nitrogen oxides (the device used to remove nitrogen oxides can be the boiler flue gas SCR denitrification device reported in Chinese Utility Model Patent CN218077253U), and the second purified flue gas is the compressed flue gas after removing sulfur oxides from the first purified flue gas.

[0064] In the process of treating the high-nitrate concentrate produced by the evaporation salt production system using the above-mentioned technology, the bromine extraction rate is calculated based on the change in the molar concentration of bromide ions between the mother liquor concentration tank and the reaction tank. The formula for calculating the bromine extraction rate is as follows:

[0065] Bromine extraction rate (%) = (Concentration of bromide ions in the mother liquor concentration tank - Concentration of bromide ions in reaction tank five) / Concentration of bromide ions in the mother liquor concentration tank × 100%.

[0066] In the process of treating the high-nitrate concentrate produced by the evaporation salt production system using the above-described process, the concentration of bromide ions in the liquid in the concentrate tank is less than 15 mg / L, and its composition is as follows:

[0067] NaCl: 270~298g / L, SO4 2- 38~55g / L, Br - <15mg / L, pH≥7.5.

[0068] The method of this invention extracts bromide ions from high-nitrate concentrate from a mother liquor concentration tank, achieving a bromine extraction rate (%) ≥98%. The concentration of bromide ions in the concentrate tank is less than 15 mg / L. This method effectively utilizes the high-nitrate, high-salt liquid in the concentrate tank, saving costs and solving the problem of continuous bromide ion enrichment in the evaporation salt production system caused by long-term recycling of bromine-containing high-nitrate liquid. This effectively avoids co-precipitation of NaBr with industrial salt during subsequent crystallization, ensuring the quality of the finished salt. At the same time, it realizes an integrated process for bromine resource recovery and harmless reuse of high-nitrate concentrate, breaking through the technical bottlenecks that urgently need to be solved in the field of clean production and efficient resource utilization of industrial salt.

[0069] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A process for extracting bromide ions from brine using flue gas extraction, characterized in that, Includes the following steps: (1) The bromide ions in the high-nitrate concentrate in the mother liquor concentration tank are converted into Br2 by chemical reaction in the reaction tank 1. The gas at the top of the reaction tank 1 enters the Br2 absorption system, and the liquid in the reaction tank 1 is pumped into the hot blowing tank from the liquid inlet opened on the side wall of the hot blowing tank. (2) The liquid inlet on the side wall of the hot blowing tank is located above the maximum set liquid level of the hot blowing tank. The gas above the liquid surface of the hot blowing tank is purged by the second gas purging of the purification flue and enters the Br2 absorption system through the gas outlet on the side wall of the hot blowing tank located above the maximum set liquid level of the hot blowing tank. When the liquid height in the hot blowing tank reaches the maximum set liquid level, the liquid at the bottom of the hot blowing tank is pumped into the residual bromine treatment system. At the same time, the liquid level in the hot blowing tank is always not lower than the liquid level corresponding to 40% of the maximum effective volume of the hot blowing tank. The maximum set liquid level of the hot blowing tank does not exceed the liquid level corresponding to 75% of the maximum effective volume of the hot blowing tank. (3) The gas entering the Br2 absorption system reacts with the Br2 absorption liquid to obtain a sodium bromide solution, and the sodium bromide solution is evaporated and crystallized to obtain sodium bromide crystals; (4) The liquid entering the residual bromine treatment system is transferred to the concentrate tank after being treated by the purified flue gas. The liquid in the concentrate tank is reused in the evaporation salt production system. (5) The gas in the Br2 absorption system and the residual bromine treatment system is discharged into the air after being chemically absorbed by the tail gas absorption system.

2. The process for extracting bromide ions from brine using flue gas extraction according to claim 1, characterized in that, The Br2 absorption system includes reaction vessel two, reaction vessel three, reaction vessel seven, and Br2 absorption liquid tank. The Br2 absorbent tank continuously pumps Br2 absorbent into reaction tank two. When the liquid level in reaction tank two reaches its maximum set level, the liquid in reaction tank two is pumped into reaction tank three. Simultaneously, the absorbent from the Br2 absorbent tank is pumped into reaction tank three at the same flow rate. When the liquid level in reaction tank three reaches its maximum set level, the liquid overflows into reaction tank seven. When the liquid level in reaction tank seven reaches its maximum set level, the liquid in reaction tank seven is pumped from the bottom into the evaporator crystallizer for evaporation and crystallization to obtain sodium bromide. The liquid levels in reaction tanks two, three, and seven must not be lower than the liquid level corresponding to 30% of the maximum effective volume of the corresponding tank. The maximum set liquid levels in reaction tanks two, three, and seven must not exceed the liquid level corresponding to 80% of the maximum effective volume of the corresponding tank. The gas above the liquid level in reaction tank seven enters the tail gas absorption system through a pipeline. The gas entering the Br2 absorption system is introduced through an independent gas pipe that connects to the top of the second reaction vessel and extends to the bottom of the second reaction vessel.

3. The process for extracting bromide ions from brine using flue gas extraction according to claim 1, characterized in that, The second purification flue gas is connected to the top of the hot blowing tank through a pipe, and the gas inside the hot blowing tank is purged from the top down.

4. The process for extracting bromide ions from brine using flue gas extraction according to claim 1, characterized in that, The residual bromine treatment system includes reaction tank four, reaction tank five, and reaction tank six. Liquid from the bottom of the hot blowing tank is pumped into reaction tank four through a pipeline. Liquid in reaction tank four overflows into reaction tank five, and liquid in reaction tank five overflows into reaction tank six. When the liquid level in reaction tank four and reaction tank five is not lower than the liquid level corresponding to 30% of the maximum effective volume of the corresponding tank, purified flue gas one is introduced into reaction tank four and reaction tank five respectively. Purified flue gas one is introduced upward from the vent at the bottom of the reaction tank. Finally, the liquid in reaction tank six is ​​transferred to the concentrate tank. The overflow liquid level of reaction tank four and reaction tank five does not exceed the liquid level corresponding to 80% of the maximum effective volume of the corresponding tank. The gas above the liquid surface in reaction tank four, reaction tank five, and reaction tank six enters the tail gas treatment system through the gas outlet at the top of the corresponding reaction tank.

5. The process for extracting bromide ions from brine using flue gas extraction according to claim 4, characterized in that, The liquid in reaction vessel six is ​​transferred to the concentrate tank via a liquid transfer pump.

6. The process for extracting bromide ions from brine using flue gas extraction according to claim 1, characterized in that, The exhaust gas absorption system includes exhaust gas absorption device one, exhaust gas absorption device two, exhaust gas absorption device three, and a lime slurry tank. The lime slurry tank continuously pumps lime slurry into exhaust gas absorption device one. When the liquid level in exhaust gas absorption device one reaches the maximum set level, the liquid in exhaust gas absorption device one and the lime slurry in the lime slurry tank are pumped into exhaust gas absorption device two at the same flow rate. When the liquid level in exhaust gas absorption device two reaches the maximum set level, the liquid in exhaust gas absorption device two and the lime slurry in the lime slurry tank are pumped into exhaust gas absorption device three at the same flow rate. When the liquid level in exhaust gas absorption device three reaches the maximum set level... The liquid overflowing from the third exhaust gas absorption device enters the lime slurry overflow tank or overflows and is discharged. The gas above the liquid surface in the third exhaust gas absorption device is directly vented. The gas entering the exhaust gas absorption system enters the exhaust gas absorption system through an independent pipe connected to the first exhaust gas absorption device and extending to the bottom of the first exhaust gas absorption device. The gas above the liquid surface in the first exhaust gas absorption device enters the second exhaust gas absorption device through a gas pipe connected to the top of the second exhaust gas absorption device and extending to the bottom of the second exhaust gas absorption device. The gas above the liquid surface in the second exhaust gas absorption device enters the third exhaust gas absorption device through a gas pipe connected to the top of the third exhaust gas absorption device and extending to the bottom of the third exhaust gas absorption device.

7. The process for extracting bromide ions from brine using flue gas extraction according to claim 1, characterized in that, The high-nitrate concentrate in the mother liquor concentration tank comes from the evaporation salt production system. The high-nitrate concentrate has a pH of 10-11.5 and a temperature of 40-80℃, and includes the following main components: NaCl:275~295g / L、SO4 2- :40~52g / L、Br - :300~1200mg / L、OH - :0.05~0.3g / L、CO3 2- :1.0-3.6 g / L、Ca 2+ :2.0~6.0mg / L、Mg 2+ :0.5~3.0mg / L。 8. The process for extracting bromide ions from brine using flue gas extraction according to claim 1, characterized in that, The Br2 absorption solution is a mixture of urea, sodium carbonate and water. The mass concentration of urea is 10-12%, and the molar ratio of sodium carbonate to urea is 3.8:1 to 4.6:1.

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