Method for extracting bromine in brine

Abstract

The invention belongs to the technical field of inorganic matter preparation methods, and particularly provides a method for extracting bromine in brine, which comprises the following steps: S1, acidification and oxidation pretreatment of brine; s2, bromine molecules are blown out through air; s3, absorbing sulfur dioxide and fresh water; s4, distilling and purifying bromine; s3, a method for adjusting the bromine concentration C in the finished liquid in the absorption process of sulfur dioxide and fresh water is included, and S300, a high-pressure atomization nozzle array with the pore diameter being 1.0-2.0 mm is adopted, the distance between nozzles is matched with the sectional area of a blowing and suction tower, and a three-dimensional atomization field is formed; s301, controlling the volume flow ratio of gas to liquid in the absorption tower; s302, the high-pressure atomization nozzle is provided with a high-pressure pump set, and the high-pressure pump set can establish a dynamic pressure compensation model; and S303, monitoring the bromine concentration C in the finished liquid in real time through an online concentration meter, and adjusting the fresh water flow in real time according to the bromine concentration C in the finished liquid so as to control the bromine concentration in the finished liquid.

Description

Technical Field

[0001] The present invention relates to the technical field of inorganic substance preparation methods, and particularly relates to a method for extracting bromine from brine. Background Art

[0002] Bromine is a resource-dependent product and an important chemical raw material, which is widely used in fields such as high-efficiency flame retardants, refrigerants, petroleum, medicine, fuel intermediates, photosensitive materials, and chemical reagents. At present, there are the following several methods for extracting bromine from brine: steam distillation method, air blowing method, resin adsorption method, extraction method, and precipitation method.

[0003] The air blowing method includes an acid solution absorption method and an alkali solution absorption method. Among them, the acid solution absorption method is to add sulfur dioxide and fresh water in the blowing and absorption tower during the extraction of bromine from brine to capture bromine molecules to form a finished solution of hydrobromic acid, and then perform distillation extraction.

[0004] In the industrial production process, the traditional control method of the sulfur dioxide reduction and absorption process depends on the fixed flow rate adjustment mode or the experience intervention of operators, and it is difficult to dynamically respond to the fluctuation of bromine concentration, which easily causes the over-dilution of the finished solution or the local crystallization due to too high concentration, affecting the subsequent distillation efficiency. Summary of the Invention

[0005] In view of the above defects, the present invention provides a method for extracting bromine from brine, which can reduce the consumption of fresh water and ensure the relative stability of the hydrobromic acid concentration at the same time.

[0006] To achieve the above object, the present invention provides the following technical solution: A method for extracting bromine from brine, comprising: S1: Acidification and oxidation pretreatment of brine, mixing brine with distillation waste liquid or dilute sulfuric acid, adjusting the pH to acidic, and then introducing chlorine gas for reaction; S2: Blowing out bromine molecules, introducing the brine treated in S1 into the blowing tower for spraying, and blowing out through a blower to form bromine-containing air; S3: Absorption of sulfur dioxide and fresh water, blowing the bromine-containing air into the absorption tower, and forming a finished solution including hydrobromic acid and sulfuric acid through contact with the sprayed sulfur dioxide gas and fresh water; S4: Distillation and purification of bromine, introducing the finished solution generated in step S3 into the distillation tower, and introducing steam and chlorine gas for reaction to generate Br2 vapor and discharge it, and obtaining the finished bromine through condensation and separation; The S3 includes a method for adjusting the bromine concentration C in the finished solution during the absorption of sulfur dioxide and fresh water: S300: Adopting a high-pressure atomizing nozzle array with a pore diameter of 1.0 - 2.0 mm, and matching the nozzle spacing with the cross-sectional area of the blowing and absorption tower to form a three-dimensional atomizing field with a coverage rate of 85% - 95%; S301: Control the gas-liquid volume flow ratio in the absorption tower within the range of 1:8 - 1:12; S302: The high-pressure atomizing nozzle is equipped with a high-pressure pump set, and the high-pressure pump set can establish a dynamic pressure compensation model: P = K×(Q / S) + ΔP Where: P is the real-time regulation pressure (MPa), Q is the fresh water flow rate (m3 / h), S is the effective spray area (m 2 ), K is the system resistance coefficient of 0.15 - 0.25, and ΔP is the pressure correction value of 0.05 - 0.12 MPa; S303: Real-time monitor the bromine concentration C in the finished liquid through an on-line concentration meter, and adjust the fresh water flow rate in real time according to the bromine concentration C in the finished liquid, so as to control the bromine concentration C in the finished liquid: 60 kg / m³ ≤ C ≤ 85 kg / m³.

[0007] As a further improvement of the present invention, the control method for the bromine concentration C in S303 is: When C < 60 kg / m³: Start the throttle valve and gradually reduce the fresh water flow rate in a gradient of 0.5% - 1.5% of the current flow reference value Q 0 until the concentration rises above 60 kg / m³; When 60 kg / m³ ≤ C ≤ 85 kg / m³: Maintain the current flow rate unchanged, and the system is in a stable operation range to avoid fluctuations caused by frequent regulation; When C > 85 kg / m³: Link the proportional valve and increase the fresh water flow rate in a gradient of 2% - 4% of the current flow reference value Q 0 until the concentration drops below 85 kg / m³.

[0008] As a further improvement of the present invention, the adjustment period of the fresh water flow rate in S303 is 30 s.

[0009] As a further improvement of the present invention, if C continuously > 90 kg / m³ for more than 4 adjustment periods in S303, trigger a three-level acceleration to adjust the fresh water flow rate change gradient ΔQ = +0.06Q 0 / time.

[0010] As a further improvement of the present invention, S303 further includes: Non-linearly compensate and adjust the fresh water flow rate change gradient ΔQ according to the concentration change rate dC / dt of bromine in the finished liquid, specifically: The calculation formula for the concentration change rate dC / dt of bromine in the finished liquid is:

[0011] When C < 60 kg / m³ and dC / dt > 0, reduce the fresh water flow rate change gradient ΔQ; When C > 85 kg / m³ and dC / dt < 0, increase the fresh water flow rate change gradient ΔQ.

[0012] As a further improvement of the present invention, in the non-linear compensation adjustment of the fresh water flow rate change gradient ΔQ, the calculation formula of the correction coefficient α is:

[0013] Correct the fresh water flow rate change gradient ΔQ through the correction coefficient α.

[0014] As a further improvement of the present invention, when C < 60 kg / m³ and dC / dt > 0, the specific calculation formula of the fresh water flow rate change gradient ΔQ is: .

[0015] As a further improvement of the present invention, when C > 85 kg / m³ and dC / dt < 0, the specific calculation formula of the fresh water flow rate change gradient ΔQ is: .

[0016] As a further improvement of the present invention, the S301 further includes: generating a negative pressure difference of 150 - 250 Pa through the Venturi effect, so that the bromine vapor and the atomized droplets form a vortex contact.

[0017] Advantages of the present invention: 1. Through the synergistic effect of the dynamic pressure compensation model and the Venturi negative pressure, the atomization pressure and the flow rate change are matched in real time, the atomization field coverage rate and the droplet uniformity are maintained, the gas-liquid contact efficiency is enhanced, and the bromine escape is reduced.

[0018] 2. The bromine concentration is monitored in real time through an on-line concentration meter, and combined with the gradient adjustment mechanism, the concentration of the finished liquid is dynamically stabilized within a specified range, effectively avoiding the risk of excessive increase or crystallization caused by out-of-control concentration in the traditional process. At the same time, a non-linear compensation design is introduced, and the fresh water flow rate adjustment gradient is dynamically adjusted according to the concentration change rate (dC / dt), significantly improving the anti-disturbance ability of the system and avoiding the concentration fluctuation caused by adjustment lag. Specific embodiments

[0019] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0020] The present invention provides a method for extracting bromine from brine, and the steps are as follows: S1: Acidification and oxidation pretreatment of brine.

[0021] Feed the brine (containing Br ions) into a static mixer, mix it with distillation waste liquid or dilute sulfuric acid, and adjust the pH to acidic (2 < pH < 3). Pass chlorine gas (Cl 2 ) into the acidified brine to oxidize bromide ions to free bromine molecules (Br 2 ).

[0022] As a further explanation of this embodiment, the purpose of acidifying the brine in S1 is to avoid the hydrolysis loss of bromine in an alkaline environment during subsequent chlorination oxidation.

[0023] S2: Air stripping of bromine molecules.

[0024] Spray the brine treated in S1 from the top of the stripping tower downwards. At the same time, a blower blows air from the bottom of the tower, flowing countercurrently to the brine, and the free Br 2 is stripped and blown out by the air to form bromine-containing air.

[0025] S3: Absorption by sulfur dioxide and fresh water.

[0026] Blow the bromine-containing air from the top of the stripping tower into the absorption tower, and make it flow in the same direction as the sprayed sulfur dioxide (SO 2 ) gas and fresh water. SO 2 and Br 2 undergo a reduction reaction in an acidic environment to generate a finished liquid including hydrobromic acid (HBr) and sulfuric acid (H 2 SO 4 ).

[0027] S4: Distillation and purification of bromine.

[0028] Feed the finished liquid containing hydrobromic acid (HBr) and sulfuric acid (H 2 SO 4 ) generated in step S3 from the top of the distillation tower, and at the same time, pass steam and chlorine gas from the bottom of the tower. Chlorine re-oxidizes HBr to Br 2 , generating Br 2 vapor. The Br 2 vapor is discharged from the top of the tower, cooled to liquid bromine by a condenser, and then the moisture and impurities are removed through a separator to finally obtain the finished product bromine.

[0029] As a further explanation of this embodiment, step S3 also includes a method for adjusting the bromine concentration C in the finished liquid during the absorption by sulfur dioxide and fresh water: S300: Use a high-pressure atomizing nozzle array with a pore diameter of 1.0 - 2.0 mm, and set the nozzle spacing to match the cross-sectional area of the blowing and suction tower to form a three-dimensional atomizing field with a coverage rate of 85 - 95%.

[0030] S301: Control the gas-liquid volume flow ratio in the absorption tower within the range of 1:8 - 1:12, generate a negative pressure difference of 150 - 250 Pa through the Venturi effect, and form a vortex contact between the bromine vapor and the atomized droplets.

[0031] S302: The high-pressure atomizing nozzle is equipped with a high-pressure pump group, and the high-pressure pump group can establish a dynamic pressure compensation model: P = K×(Q / S) + ΔP Where: P is the real-time regulated pressure (MPa), Q is the fresh water flow rate (m 3 / h), S is the effective spraying area (m 2 ), K is the system resistance coefficient (0.15 - 0.25), and ΔP is the pressure correction value (0.05 - 0.12 MPa).

[0032] S303: Real-time monitor the bromine concentration C in the finished liquid through an on-line concentration meter, and adjust the fresh water flow rate in real time according to the bromine concentration C in the finished liquid, so as to control the bromine concentration C in the finished liquid: 60 kg / m³ ≤ C ≤ 85 kg / m³.

[0033] When C < 60 kg / m³: Start the throttle valve, and gradually reduce the fresh water flow rate in a gradient of 0.5% - 1.5% of the current flow rate reference value (Q 0 ), until the concentration rises above 60 kg / m³. 0 ~ -0.015Q 0 )

[0034] Adjustment period: Detect once every 30 seconds, and the single adjustment amplitude does not exceed 1.5%.

[0035] When 60 kg / m³ ≤ C ≤ 85 kg / m³: Maintain the current flow rate unchanged, and the system is in a stable operation range to avoid fluctuations caused by frequent adjustments.

[0036] When C > 85 kg / m³: Link the proportional valve, and increase the fresh water flow rate in a gradient of 2% - 4% (ΔQ = +0.02Q 0 ~ +0.04Q 0 ), until the concentration drops below 85 kg / m³.

[0037] Adjustment period: Detect once every 30 seconds, and the single adjustment amplitude does not exceed 4%.

[0038] Emergency mode: If C continuously > 90 kg / m³ for more than 2 minutes, trigger a three-level acceleration adjustment (ΔQ = +0.06Q 0 / time).

[0039] As a further explanation of this embodiment, S303 further includes non-linearly compensating and adjusting the fresh water flow rate change gradient ΔQ according to the change rate of bromine concentration dC / dt in the completion liquid, specifically: Calculate the concentration change rate (dC / dt) through the continuous sampling data of the on-line concentration meter

[0040] When dC / dt > 0, it means the concentration is rising. When dC / dt < 0, it means the concentration is falling.

[0041] Then establish a mathematical model of the gradient correction coefficient (α). The calculation formula of the correction coefficient α is:

[0042] Specifically, through non-linear compensation design, the correction coefficient α corrects the fresh water flow rate change gradient ΔQ: When C < 60 kg / m³ and dC / dt > 0, the concentration rises rapidly, and it is necessary to slow down the reduction and reduce the fresh water flow rate change gradient ΔQ to avoid excessive rise of the completion liquid.

[0043]

[0044] When C > 85 kg / m³ and dC / dt < 0, the concentration drops rapidly, and it is necessary to accelerate dilution and increase the fresh water flow rate change gradient ΔQ to prevent crystallization risk.

[0045] .

[0046] Example 1 S1: Acidification and oxidation pretreatment of brine.

[0047] Feed the brine (containing Br ions) into a static mixer, mix it with the distillation waste liquid or dilute sulfuric acid, and adjust the pH to 2.5. Feed chlorine gas (Cl 2 ) into the acidified brine.

[0048] S2: Air stripping of bromine molecules.

[0049] Spray the brine treated in S1 from the top of the stripping tower. At the same time, blow air from the bottom of the tower by a blower, which flows countercurrently to the brine to form bromine-containing air.

[0050] S3: Sulfur dioxide and fresh water absorption.

[0051] Blow the bromine-containing air from the top of the stripping tower into the absorption tower, and make it flow in the same direction as the sprayed sulfur dioxide (SO 2 ) gas and fresh water in contact.

[0052] The device for spraying fresh water adopts a high-pressure atomizing nozzle array with a pore diameter of 1.0 mm, and is configured with the nozzle spacing matching the cross-sectional area of the blow-suction tower to form a three-dimensional atomization field with a coverage rate of 85%.

[0053] With the reference flow rate Q of fresh water 0 being 12 m 3 / h, fresh water is injected into the absorption tower, and the gas-liquid volume flow ratio in the absorption tower is controlled at 1:12 to obtain the flow rate Q 2 of gas SO q0 as follows: Q q0 = Q 0 × 1 / 12 = 1 m 3 / h The negative pressure difference generated inside the absorption tower through the Venturi effect is controlled at 150 Pa.

[0054] Meanwhile, it is known that the effective spraying area S of the absorption tower is 7 m 2 , and taking the system resistance absorption K as 0.25 and the pressure correction value ΔP as 0.12 MPa, the working pressure P 0 of the high-pressure pump group can be obtained through calculation as follows: P 0 = K × (Q 0 / S) + ΔP = 0.25 × (12 / 7) + 0.12 ≈ 0.549 Pa Under this operating condition, according to the detection period Δt = 30 s, the bromine concentration in the finished liquid is detected in real time by an on-line concentration meter.

[0055] After a certain periodic detection, it is found that the bromine concentration C 0 in the finished liquid = 58 kg / m³ (lower than the lower limit of 60 kg / m³); The system triggers the bromine concentration C adjustment mechanism: 1. First adjustment (t = 0).

[0056] Concentration change: The initial concentration C 0 = 58 kg / m³, triggering the adjustment condition (C 0 < 60 kg / m³).

[0057] Adjustment action: Using the reference gradient ΔQ 1 = -1.2% × Q 0 = -0.144 m³ / h Q 1 = Q 0 + ΔQ 1 = 12 - 0.144 = 11.856 m³ / h.

[0058] At this time, SO2 The flow rate Q q1 for: Q q1 = Q 1 ×1 / 12=11.856×1 / 12=0.988m 3 / h The working pressure P of the high-pressure pump group can be obtained by calculation 1 for: P 1 =K×(Q 1 / S)+ΔP=0.25×(11.856 / 7)+0.12≈0.543Pa.

[0059] 2. Second detection and adjustment (t=30 seconds).

[0060] Concentration changes: After the first adjustment, the bromine concentration in the finished solution was detected to be C 1 =59kg / m³, C 1 <60kg / m³, Adjustment action: Calculate the concentration change rate

[0061] Gradient Correction

[0062] Because the concentration change rate dC / dt>0 (concentration rising trend), but C 1 Still below the lower limit, excessive reduction needs to be suppressed:

[0063] Actual adjustment: To prevent response lag, the actual adjustment amount Q 2 should be slightly higher than the calculated value, so ΔQ 2 Should be slightly smaller than the calculated value (but ΔQ 2 Should not exceed the range of change and always be within -0.005Q 0 ~-0.015Q 0 between), Take the safe value ΔQ 2 = -0.8% × Q 0 = -0.096m³ / h Q 2 =Q 1 +ΔQ 2 =11.76m³ / h.

[0064] At this time SO 2 The flow rate Q q2 for: Q q2 = Q 2 ×1 / 12 = 0.98m 3 / h The working pressure P of the high-pressure pump set can be obtained through calculation 2 as follows: P 2 = K × (Q 2 / S) + ΔP = 0.25 × (11.76 / 7) + 0.12 = 0.54Pa.

[0065] 3. Third detection and adjustment.

[0066] Concentration change: The detected concentration C 3 = 61 kg / m³, enters the safe zone (60 - 85 kg / m³), and stops the adjustment of the fresh water flow rate.

[0067] S4: Distillation and purification of bromine.

[0068] Add the finished liquid containing hydrobromic acid (HBr) and sulfuric acid (H 2 SO 4 ) generated in step S3 from the top of the distillation column, and at the same time, introduce steam and chlorine gas from the bottom of the column. Chlorine re-oxidizes HBr to Br 2 to generate Br 2 vapor. The Br 2 vapor is discharged from the top of the column, cooled to liquid bromine by a condenser, and then the moisture and impurities are removed through a separator to finally obtain the finished bromine.

[0069] Example 2 S1: Acidification and oxidation pretreatment of brine.

[0070] Introduce the brine (containing Br ions) into a static mixer, mix it with the distillation waste liquid or dilute sulfuric acid, and adjust the pH to 2.5. Introduce chlorine gas (Cl 2 ) into the acidified brine.

[0071] S2: Air blowing out bromine molecules.

[0072] Spray the brine treated in S1 from the top of the blowing column downwards. At the same time, a blower blows air from the bottom of the column, flowing countercurrently to the brine to form bromine-containing air.

[0073] S3: Absorption by sulfur dioxide and fresh water.

[0074] Blow the bromine-containing air from the top of the blowing column into the absorption column to make it flow in the same direction as the sprayed sulfur dioxide (SO 2 ) gas and fresh water in contact.

[0075] Device for spraying fresh water, using a high-pressure atomizing nozzle array with a pore diameter of 2.0 mm, and setting the nozzle spacing to match the cross-sectional area of the blow-suction tower to form a three-dimensional atomization field with a coverage rate of 95%.

[0076] Taking the reference flow rate Q of fresh water 0 as 12 m 3 / h, inject fresh water into the absorption tower, and control the gas-liquid volume flow ratio in the absorption tower at 1:8 to obtain the flow rate Q of gas SO 2 as: q0 Q Q q0 = Q 0 × 1 / 8 = 1.5 m 3 / h Control the negative pressure difference generated by the Venturi effect inside the absorption tower to be 250 Pa.

[0077] At the same time, it is known that the effective spraying area S of the absorption tower is 10 m 2 , and taking the system resistance absorption K as 0.15 and the pressure correction value ΔP as 0.05 MPa, the working pressure P of the high-pressure pump group can be obtained through calculation as: 0 P P 0 = K × (Q 0 / S) + ΔP = 0.15 × (12 / 10) + 0.05 = 0.23 Pa Under this working condition, according to the detection period Δt = 30 s, the bromine concentration in the finished liquid is detected in real time by an on-line concentration meter.

[0078] After a certain periodic detection, it is found that the bromine concentration C in the finished liquid 0 = 88 kg / m³ (higher than the upper limit of 85 kg / m³); 1. First adjustment (t = 0).

[0079] The concentration changes to the initial concentration C 0 = 88 kg / m³, triggering the adjustment condition (C 0 > 85 kg / m³).

[0080] Adjustment action: Using the reference gradient ΔQ 1 = 3% × Q 0 = 0.36 m³ / h, Q 1 = Q 0 + ΔQ 1 = 12 + 0.36 = 12.36 m³ / h At this time, the flow rate Q of SO 2 is: q1 Q Q q1 = Q 1×1 / 8 = 12.36×1 / 8 = 1.545 m 3 / h By calculation, the working pressure P of the high-pressure pump set can be obtained as follows: 1 is: P 1 = K×(Q 1 / S) + ΔP = 0.15×(12.36 / 10) + 0.05 ≈ 0.235 Pa.

[0081] 2. Second detection and adjustment (t = 30 seconds).

[0082] Concentration change: After the first adjustment, the bromine concentration change in the finished liquid is detected as C 21 = 86 kg / m³, C 1 > 85 kg / m³, Adjustment action: Calculate the concentration change rate

[0083] Gradient correction

[0084] Since the concentration change rate dC / dt < 0 (concentration decreasing trend), but C 1 is still greater than the upper limit, to prevent crystallization, it is necessary to accelerate dilution:

[0085] Actual adjustment: To prevent response lag, the actual adjustment amount Q 2 should be slightly higher than the calculated value. Therefore, ΔQ 2 should be slightly higher than the calculated value (but ΔQ 2 should not exceed the change range and is always between +0.02Q 0 ~ +0.04Q 0 ), Take the safety value ΔQ 2 = 3.5%×Q 0 = 0.42 m³ / h Q 2 = Q 1 + ΔQ 2 = 12.36 + 0.42 = 12.78 m³ / h.

[0086] At this time, the flow rate Q of SO 2 is: q2 is: Q q2 = Q 2 ×1 / 8 ≈ 1.60 m 3 / h The working pressure P of the high-pressure pump set can be obtained by calculation 2 as follows: P 2 = K × (Q 2 / S) + ΔP = 0.15 × (12.78 / 10) + 0.05 ≈ 0.242 Pa.

[0087] 3. Third detection and adjustment.

[0088] Concentration change: The detected concentration C 3 = 84 kg / m³, enters the safe zone (60 - 85 kg / m³), and stops the adjustment of the fresh water flow rate.

[0089] S4: Distill and purify bromine.

[0090] Add the finished liquid containing hydrobromic acid (HBr) and sulfuric acid (H 2 SO 4 ₄) generated in step S3 from the top of the distillation column, and at the same time, introduce steam and chlorine gas from the bottom of the column. The chlorine gas re-oxidizes HBr to Br 2 , generating Br 2 vapor. The Br 2 vapor is discharged from the top of the column, cooled to liquid bromine by a condenser, and then the moisture and impurities are removed through a separator, and finally the finished bromine is obtained.

[0091] The above is only the preferred implementation mode of the present invention. The protection scope of the present invention is not limited to the above implementation measures. All technical solutions falling within the idea of the present invention belong to the protection scope of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for extracting bromine from brine, characterized in that: include: S1: Acidification and oxidation pretreatment of brine: mix brine with distillation waste liquid or dilute sulfuric acid, adjust pH to acidic, and then introduce chlorine gas for reaction; S2: Blow out the bromine molecules with air, pass the brine treated by S1 into the blowing tower for spraying, and blow it out through the blower to form bromine-containing air; S3: Absorption of sulfur dioxide and fresh water, blowing bromine-containing air into the absorption tower, and forming a finished liquid including hydrobromic acid and sulfuric acid through contact with the sprayed sulfur dioxide gas and fresh water; S4: Distill and purify bromine, pass the finished liquid generated in step S3 into a distillation tower, and pass water vapor and chlorine gas into the distillation tower for reaction, generate Br2 vapor and discharge it, and obtain finished bromine by condensation and separation; S3 includes a method for adjusting the bromine concentration C in the finished liquid during the absorption process of sulfur dioxide and fresh water: S300: It uses a high-pressure atomizing nozzle array with an aperture of 1.0-2.0mm, and matches the nozzle spacing with the cross-sectional area of ​​the blowing and absorption tower to form a three-dimensional atomization field with a coverage rate of 85%-95%; S301: Control the gas-liquid volume flow ratio in the absorption tower within the range of 1:8-1:12; S302: The high-pressure atomizing nozzle is equipped with a high-pressure pump group, which can establish a dynamic pressure compensation model: P=K×(Q / S)+ΔP Where: P is the real-time control pressure (MPa), Q is the fresh water flow (m 3 / h), S is the effective spraying area (m 2 ), K is the system resistance coefficient 0.15-0.25, ΔP is the pressure correction value 0.05-0.12MPa; S303: The bromine concentration C in the finished liquid is monitored in real time by an online concentration meter, and the fresh water flow rate is adjusted in real time according to the bromine concentration C in the finished liquid, so as to control the bromine concentration C in the finished liquid: 60kg / m³ ≤ C ≤85kg / m³.

2. The method for extracting bromine from brine according to claim 1, characterized in that: The control method for the bromine concentration C in S303 is: When C < 60kg / m³: Start the throttle valve and gradually reduce the fresh water flow rate by 0.5%-1.5% of the current flow rate reference value Q0 until the concentration rises back to above 60kg / m³; When 60kg / m³ ≤ C ≤85kg / m³: Maintain the current flow rate unchanged, keep the system in a stable operating range, and avoid fluctuations caused by frequent adjustments; When C >85kg / m³: Link the proportional valve to increase the fresh water flow rate by 2%-4% of the current flow reference value Q0 until the concentration drops below 85kg / m³.

3. The method for extracting bromine from brine according to claim 2, characterized in that: The adjustment period of the fresh water flow in S303 is 30s.

4. The method for extracting bromine from brine according to claim 3, characterized in that: In the above S303, if C continues to be >90kg / m³ for more than 4 adjustment cycles, the third-level accelerated adjustment of the fresh water flow rate change gradient ΔQ = +0.06Q0 / time is triggered.

5. The method for extracting bromine from brine according to claim 2, characterized in that: The S303 further includes: According to the concentration change rate dC / dt of bromine in the finished liquid, the nonlinear compensation adjustment of the fresh water flow gradient ΔQ is carried out, specifically: The calculation formula of the concentration change rate dC / dt of bromine in the finished solution is: When C <60kg / m³ and dC / dt >0, reduce the freshwater flow gradient ΔQ; When C >85kg / m³ and dC / dt< 0, increase the freshwater flow gradient ΔQ.

6. The method for extracting bromine from brine according to claim 5, characterized in that: In the nonlinear compensation adjustment of the fresh water flow gradient ΔQ, the calculation formula of the correction coefficient α is: The freshwater flow gradient ΔQ is corrected by the correction coefficient α.

7. The method for extracting bromine from brine according to claim 6, characterized in that: When C <60 kg / m³ and dC / dt>0, the calculation formula for the freshwater flow gradient ΔQ is: 。 8. The method for extracting bromine from brine according to claim 6, characterized in that: When C >85kg / m³ and dC / dt<0, the calculation formula for the freshwater flow gradient ΔQ is: 。 9. The method for extracting bromine from brine according to claim 1, characterized in that: The S301 further includes: generating a negative pressure difference of 150-250 Pa by using the Venturi effect, so that the bromine vapor and the atomized liquid droplets form a vortex contact.

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