A method for efficiently extracting bromine from concentrated seawater using waste heat

Abstract

The present invention belongs to the field of resource utilization of waste heat and components in industrial by-product water, and particularly relates to a method for efficiently extracting bromine from concentrated seawater by using waste heat. Take the concentrated seawater by-produced from thermal seawater desalination and the concentrated seawater by-produced from membrane seawater desalination, mix them after pretreatment to form mixed concentrated seawater; the mixed concentrated seawater passes through a nanofiltration membrane device to remove most of the Ca 2+ , Mg 2+ and SO4 2‑ and then form mixed nanofiltration product water; the mixed nanofiltration product water passes through a reverse osmosis membrane device to increase the NaCl concentration and then form concentrated brine; sulfuric acid is added to the concentrated brine to form acidified concentrated brine; the acidified concentrated brine is sent to a bromine extraction device to extract bromine. The present invention increases the bromine concentration in the raw water of the acid method bromine extraction device and the temperature of the raw water of the acid method bromine extraction device in winter at low temperature, thereby increasing the bromine extraction rate; when the external environmental temperature is high, it can keep the system water temperature within the safe operating temperature range of the reverse osmosis membrane, and enable the bromine extraction device to continuously operate at a relatively high level of bromine extraction rate.

Description

Technical Field

[0001] The present invention belongs to the field of resource utilization of waste heat and components in industrial by - product water, and particularly relates to a method for efficiently extracting bromine from concentrated seawater by using waste heat. Background Technique

[0002] Bromine is an important chemical raw material and has wide applications in industries such as flame retardants, fire extinguishing agents, refrigerants, photosensitive materials, medicine, pesticides, and oil fields. Industrially, bromine products are generally extracted from underground brine, salt field solar evaporation brine, seawater, concentrated seawater by - product from membrane - method seawater desalination, and warm wastewater by - product after seawater heat exchange in thermal power plants. The extraction rate of bromine from these raw waters is greatly affected by the temperature of the raw water and the bromine concentration in the raw water. Under normal conditions, the higher the temperature and bromine concentration of the above - mentioned raw water, the higher the extraction rate.

[0003] The bromine concentration in underground brine is about in the range of 0.15 - 0.4 g / l, the bromine concentration in salt field solar evaporation brine is about in the range of 0.08 - 0.12 g / l, the bromine concentration in seawater is about in the range of 0.03 - 0.04 g / l, the bromine concentration in concentrated seawater by - product from membrane - method seawater desalination is about in the range of 0.05 - 0.08 g / l, and the bromine concentration in warm wastewater by - product after seawater heat exchange in thermal power plants is about in the range of 0.05 - 0.06 g / l.

[0004] In winter, bromine - producing enterprises in northern China are often in a shutdown state due to the objective condition of low temperature. The devices for extracting bromine using underground brine, salt field solar evaporation brine, seawater, and concentrated seawater by - product from membrane - method seawater desalination as raw water are more significantly affected by the low temperature in winter. The device for extracting bromine using warm wastewater by - product after seawater heat exchange in thermal power plants has a water temperature about 8 - 15 °C higher than the ambient water temperature in winter, but the bromine concentration in the bromine - extraction raw water is still only approximately equal to the bromine concentration in ordinary seawater, and it is still difficult to improve the bromine - extraction efficiency.

[0005] Before bromine extraction, using a reverse osmosis membrane to concentrate the salt - containing raw brine or seawater to enrich bromine is an effective pre - treatment measure to increase the bromine concentration in the raw water. However, the reverse osmosis membrane generally cannot operate at a temperature higher than 42 °C for a long time, otherwise it will cause irreversible damage to the membrane elements.

[0006] Therefore, in bromine - extraction production, in order to improve the bromine extraction rate, a method is needed to achieve: 1. Concentrate the bromine in the raw water to increase the concentration to facilitate the improvement of the bromine extraction rate; 2. When the temperature of the raw water is low, increase the temperature of the raw water to facilitate the improvement of the bromine extraction rate. When the temperature of the raw water is high, without reducing the bromine concentration, cool the raw water to make the operating temperature of the membrane equipment not exceed the safety limit of 42 °C, and provide stable raw water for the bromine - extraction device to maintain a high and stable bromine extraction rate. However, in the content disclosed in the following retrieved documents: CN111573955A, CN117923427A, the problems of how to solve or handle the low environmental temperature are not disclosed. Summary of the Invention

[0007] The problem to be solved by the present invention is: the problem of low bromine extraction rate in the air blowing acid process for bromine extraction from raw water under natural temperature conditions; thus, a method combining reverse osmosis membrane concentration of concentrated seawater and air blowing acid process for bromine extraction is provided. By pre-treating and proportioning the concentrated seawater by-products from thermal seawater desalination and membrane seawater desalination, on the one hand, taking advantage of the fact that the bromine concentration in both concentrated seawaters is higher than that in ordinary seawater, the bromine concentration is further increased after reverse osmosis membrane concentration. The concentrated brine produced after the concentration of concentrated seawater is acidified and then sent to the bromine extraction device to improve the bromine extraction rate; on the other hand, using the heat energy and temperature difference carried by the concentrated seawater by-products from membrane method and thermal method seawater desalination, through water volume proportioning, the temperature of the raw water of the bromine extraction device is higher than the ambient water temperature when the external temperature is low, thus facilitating the improvement of the bromine extraction rate; when the external temperature is high, the water temperature in the reverse osmosis membrane is lower than the upper limit of the safe operating temperature of the membrane, ensuring that concentrated brine with relatively stable temperature, flow rate and concentration is provided for the subsequent bromine extraction device, and facilitating the continuous operation of the device with the bromine extraction rate maintained at a relatively high level.

[0008] To solve the above technical problems, the present invention adopts the following technical solutions:

[0009] A method for efficiently extracting bromine from concentrated seawater using waste heat is carried out according to the following steps:

[0010] S1. Take the concentrated seawater by-products from thermal seawater desalination and membrane seawater desalination, mix them after pre-treatment to make mixed concentrated seawater;

[0011] S2. The mixed concentrated seawater passes through a nanofiltration membrane device to remove most of the Ca 2+ , Mg 2+ and SO4 2- and then make mixed nanofiltration product water;

[0012] S3. The mixed nanofiltration product water passes through a reverse osmosis membrane device to increase the NaCl concentration and then make concentrated brine;

[0013] S4. Sulfuric acid is added to the concentrated brine to make acidified concentrated brine;

[0014] S5. The acidified concentrated brine is sent to a bromine extraction device to extract bromine.

[0015] Compared with the prior art, the present invention adopting the above technical solutions has the following advantages and effects:

[0016] (1) It can increase the bromine concentration in the raw water of the air blowing acid process for bromine extraction, thereby improving the bromine extraction rate;

[0017] (2) When the temperature is low, it can increase the temperature of the raw water of the air blowing acid process for bromine extraction, thereby improving the bromine extraction rate;

[0018] When the temperature is high, it can keep the system water temperature within the safe operating temperature range of the reverse osmosis membrane, enabling the bromine extraction rate of the air blowing acid process bromine extraction device to continuously operate at a relatively high level.

[0019] It can make full use of the heat energy and bromine resources carried by the concentrated seawater by-products of both the membrane method and the thermal method of seawater desalination for bromine production.

[0020] The concentrated brine after bromine extraction can be used for salt chemical production such as soda ash and chlor-alkali, or for salt field salt drying, realizing the comprehensive utilization of resources. At the same time, it provides a channel for the disposal of the concentrated seawater by-products of membrane method and thermal method seawater desalination enterprises, reducing the environmental negative impact caused by the discharge of concentrated seawater into the sea.

[0021] The present invention adopts the following preferred solutions:

[0022] In step S1, the concentrated seawater by-product of thermal seawater desalination, after passing through a sand filter in sequence, is mixed with the concentrated seawater by-product of membrane method seawater desalination and then enters a multi-media filter to remove impurities, and then enters the pretreatment production water tank after being filtered by an ultrafiltration membrane device.

[0023] In step S1, the mixed concentrated seawater is made, and the turbidity is stable and lower than 1 NTU.

[0024] The pH of the mixed concentrated seawater is adjusted to 6 - 6.5 with hydrochloric acid, a scale inhibitor is added at 2 - 3 ppm, and at a pressure of 2.2 - 3 MPa, more than 90% of Ca 2+ , Mg 2+ and SO4 2- are removed, and then the mixed nanofiltration product water is made.

[0025] The volume ratio of the concentrated seawater by-product of thermal seawater desalination to the concentrated seawater by-product of membrane method seawater desalination described in step S1 is 1:0.5 - 2.

[0026] The temperature of the concentrated seawater by-product of thermal seawater desalination described in step S1 is 40 - 45 °C.

[0027] The NaCl concentration of the concentrated brine made in step S3 is 110 - 120 g / l, the Br ion concentration is 0.2 - 0.24 g / l, and the temperature is 20 - 28 °C.

[0028] The pH value of the acidified concentrated brine described in step S4 is 2.5 - 3.5.

[0029] The bromine extraction device adopted in step S5 is an air blowing acid process bromine extraction device, and the main process flow includes oxidation, blowing, absorption and enrichment, distillation, condensation, washing and bromine water separation. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a schematic process flow diagram of the present invention. Detailed implementation mode

[0031] The present invention will be described in detail below in conjunction with the process flow schematic diagram and embodiments:

[0032] A method for efficiently extracting bromine from concentrated seawater by using waste heat is carried out according to the following steps:

[0033] S1. The concentrated seawater by-produced from thermal seawater desalination is successively passed through a sand filter, and then mixed with the concentrated seawater by-produced from membrane seawater desalination and enters a multi-media filter to remove impurities. After passing through an ultrafiltration membrane device for filtration, it enters a pre-treatment production water tank.

[0034] The concentrated seawater by-produced from thermal seawater desalination and the concentrated seawater by-produced from membrane seawater desalination after pre-treatment remove impurities such as colloidal substances, particulate matters, and macromolecular substances, and are mixed to form mixed concentrated seawater, making the turbidity stable and lower than 1 NTU. The pre-treatment is successively composed of a sand filter, a multi-media filter, and an ultrafiltration membrane.

[0035] S2. In the mixed concentrated seawater in the previous step S1, hydrochloric acid is used to adjust the pH to the range of 6-6.5, and a scale inhibitor is added at 2-3 ppm. Under the pressure of 2.2-3 MPa, after removing more than 90% of Ca2+, Mg2+, and SO42- through a nanofiltration membrane device, mixed nanofiltration produced water is made.

[0036] S3. The mixed nanofiltration produced water in the previous step S2 is in the pressure range of 5-8 MPa and the temperature range of 20-28 °C. After passing through a reverse osmosis membrane device, concentrated brine with a NaCl concentration in the range of 110-120 g / l, a Br ion concentration in the range of 0.2-0.24 g / l, and a temperature in the range of 20-28 °C is made.

[0037] S4. Sulfuric acid is added to the concentrated brine in the previous step S3 to adjust the pH to the range of 2.5-3.5 to make acidified concentrated brine.

[0038] S5. The acidified concentrated brine in the previous step S4 is sent to an air-blowing acid method bromine extraction device to extract bromine. The main process flow of the device includes oxidation, blowing, absorption and enrichment, distillation, condensation, washing, and bromine water separation.

[0039] In the solution of the present invention, the amount of the concentrated seawater by-produced from membrane seawater desalination taken in step S1 is 0.5-2 times the volume of the concentrated seawater by-produced from thermal seawater desalination. When the external environmental temperature is low, the volume ratio of the concentrated seawater by-produced from thermal seawater desalination is higher. When the external environmental temperature is high, the volume ratio of the concentrated seawater by-produced from thermal seawater desalination is lower, and dynamic adjustment of the ratio can be carried out according to needs.

[0040] The main equipment in this embodiment includes a sand filter, a multi-media filter, an ultrafiltration membrane device, a nanofiltration membrane device, a reverse osmosis membrane device, and an air-blowing acid method bromine extraction device.

[0041] The pre-treatment stage is successively composed of three main devices: a sand filter, a multi-media filter, and an ultrafiltration membrane device. The brine by-produced from thermal seawater desalination is connected to the water inlet of the sand filter through a pipeline. A valve is set at the water inlet of the sand filter to control the water inflow rate of the brine by-produced from thermal seawater desalination. The sand filter is filled with quartz sand of Φ0.5 - 8 with a thickness of 1300 mm. The brine by-produced from membrane seawater desalination is connected to the outlet pipeline of the sand filter through a pipeline. A valve is set at the connection position to control the water inflow rate of the brine by-produced from membrane seawater desalination. The two kinds of brines are merged into the water inlet of the multi-media filter through a pipeline. The working pressure of the multi-media filter is 0.6 MPa, and the filtration accuracy is 2 - 5 μm. The outlet of the multi-media filter is connected to the water inlet of the ultrafiltration membrane device through a pipeline. The ultrafiltration membrane is made of hollow fiber external pressure type polyvinylidene fluoride material, and the working pressure is 0.06 MPa. Before the mixed brine made after pre-treatment enters the nanofiltration membrane device, through the control of the flow valve, hydrochloric acid is added to adjust the pH of the mixed brine to 6.5, and then 2 ppm of scale inhibitor is added. The mixed brine added with hydrochloric acid and BASF Sokalan PM 15I scale inhibitor is sent to the water inlet of the nanofiltration membrane device through a pipeline. The nanofiltration membrane is made of poly(piperazine) composite material, and the working pressure is 2.2 - 3 MPa. The nanofiltration product water is connected to the water inlet of the reverse osmosis membrane through a pipeline. The reverse osmosis membrane is made of aromatic polyamide material, and the working pressure is 6.5 MPa. The nanofiltration product water is separated by the reverse osmosis membrane device to produce concentrated brine with a NaCl concentration of 110 - 120 g / l, a Br ion concentration of 0.2 - 0.24 g / l, and a temperature of 20 - 28 °C. The concentrated brine is transported through a pipeline, and sulfuric acid is added through the control of the flow valve on the pipeline to adjust the pH to 2.5 - 3.5. After making acidified concentrated brine, it is sent to the air blowing acid method bromine extraction device.

[0042] Based on the above content, the following will further combine specific data for more detailed description: Example 1:

[0043] The average value of the water intake index during the operation cycle is shown in Table 1 below:

[0044]

[0045] Table 1

[0046] Through valve control, take concentrated seawater by-products from thermal seawater desalination and concentrated seawater by-products from membrane seawater desalination with a volume ratio of 1:1. After the concentrated seawater by-products from thermal seawater desalination pass through a sand filter, they are combined with the concentrated seawater by-products from membrane seawater desalination and pass through a multi-media filter and an ultrafiltration membrane device. Then, the pH value is adjusted to 6.5 with 37% hydrochloric acid, and 2 ppm of scale inhibitor is added. The mixed concentrated seawater after adjusting the pH value and adding BASF Sokalan PM 15I scale inhibitor, that is, the pre-treated product water, passes through a nanofiltration membrane device under a pressure of 2.5 MPa. The nanofiltration product water enters a reverse osmosis membrane device under a pressure of 6.5 MPa to produce concentrated brine. 15% dilute sulfuric acid is added to the concentrated brine to adjust the pH to 3. After making acidified concentrated brine, it is sent to an air-blowing acid process bromine extraction device.

[0047] Since the device starts operating according to the above parameters, the water intake temperature, concentrated brine temperature, and bromine extraction rate are sampled and detected every 4 hours. 30 days is recorded as one operation cycle, and the operation indicators are shown in Table 1 above. The average bromine extraction rate of the bromine extraction device within the 30-day cycle is 74%. Example 2:

[0048] The average value of the water intake indicators within the operation cycle is shown in Table 2 below:

[0049]

[0050] Table 2

[0051] Through valve control, take concentrated seawater by-products from thermal seawater desalination and concentrated seawater by-products from membrane seawater desalination with a volume ratio of 1:1.5. After the concentrated seawater by-products from thermal seawater desalination pass through a sand filter, they are combined with the concentrated seawater by-products from membrane seawater desalination and pass through a multi-media filter and an ultrafiltration membrane device. Then, the pH value is adjusted to 6.5 with 37% hydrochloric acid, and 2 ppm of scale inhibitor is added. The mixed concentrated seawater after adjusting the pH value and adding BASF Sokalan PM 15I scale inhibitor, that is, the pre-treated product water, passes through a nanofiltration membrane device under a pressure of 2.5 MPa. The nanofiltration product water enters a reverse osmosis membrane device under a pressure of 6.5 MPa to produce concentrated brine. 15% dilute sulfuric acid is added to the concentrated brine to adjust the pH to 3. After making acidified concentrated brine, it is sent to an air-blowing acid process bromine extraction device.

[0052] Since the device starts operating according to the above parameters, the water intake temperature, concentrated brine temperature, and bromine extraction rate are sampled and detected every 4 hours. 30 days is recorded as one operation cycle, and the operation indicators are shown in Table 2 above. The average bromine extraction rate of the bromine extraction device within the 30-day cycle is 71%. Example 3:

[0053] The average value of the water intake indicators within the operation cycle is shown in Table 3 below:

[0054]

[0055] Table 3

[0056] Through valve control, concentrated brine by-products from thermal seawater desalination and concentrated brine by-products from membrane seawater desalination with a volume ratio of 1:0.5 are taken. After the concentrated brine by-products from thermal seawater desalination pass through a sand filter, they are combined with the concentrated brine by-products from membrane seawater desalination, and after passing through a multi-media filter and an ultrafiltration membrane device, the pH value is adjusted to 6.5 with 37% hydrochloric acid, and 2 ppm of scale inhibitor is added. The mixed concentrated brine with the pH value adjusted and the BASF Sokalan PM 15I scale inhibitor added, that is, the pre-treated product water, passes through a nanofiltration membrane device under a pressure of 2.5 MPa, and the nanofiltration product water enters a reverse osmosis membrane device under a pressure of 6.5 MPa to produce concentrated brine. 15% dilute sulfuric acid is added to the concentrated brine to adjust the pH to 3, and after making acidified concentrated brine, it is sent to an air-blowing acid method bromine extraction device.

[0057] Since the device is put into operation according to the above parameters, the water intake temperature, concentrated brine temperature and bromine extraction rate are sampled and detected every 4 hours. 30 days is recorded as an operation cycle, and the operation indicators are shown in Table 3 above.

[0058] The average bromine extraction rate of the bromine extraction device within a 30-day cycle is 78%. Example 4:

[0059] The average value of the water intake indicators within the operation cycle is shown in Table 4 below:

[0060]

[0061] Table 4

[0062] Through valve control, concentrated brine by-products from thermal seawater desalination and concentrated brine by-products from membrane seawater desalination with a volume ratio of 1:2 are taken. After the concentrated brine by-products from thermal seawater desalination pass through a sand filter, they are combined with the concentrated brine by-products from membrane seawater desalination, and after passing through a multi-media filter and an ultrafiltration membrane device, the pH value is adjusted to 6.5 with 37% hydrochloric acid, and 2 ppm of scale inhibitor is added. The mixed concentrated brine with the pH value adjusted and the BASF Sokalan PM 15I scale inhibitor added, that is, the pre-treated product water, passes through a nanofiltration membrane device under a pressure of 2.5 MPa, and the nanofiltration product water enters a reverse osmosis membrane device under a pressure of 6.5 MPa to produce concentrated brine. 15% dilute sulfuric acid is added to the concentrated brine to adjust the pH to 3, and after making acidified concentrated brine, it is sent to an air-blowing acid method bromine extraction device.

[0063] Since the device is put into operation according to the above parameters, the water intake temperature, concentrated brine temperature and bromine extraction rate are sampled and detected every 4 hours. 30 days is recorded as an operation cycle, and the operation indicators are shown in Table 4 above. The average bromine extraction rate of the bromine extraction device within a 30-day cycle is 68%. Example 5:

[0064] The average value of the water intake indicators within the operation cycle is shown in Table 5 below:

[0065]

[0066] Table 5

[0067] Through valve control, concentrated brine by - products of thermal seawater desalination and concentrated brine by - products of membrane seawater desalination with a volume ratio of 1:2 are taken. After the concentrated brine by - products of thermal seawater desalination pass through a sand filter, they are combined with the concentrated brine by - products of membrane seawater desalination and then pass through a multi - media filter and an ultra - filtration membrane device. Then, the pH value is adjusted to 6.5 with 37% hydrochloric acid, and 2 ppm of scale inhibitor is added. The mixed concentrated brine with the pH value adjusted and the BASF Sokalan PM 15I scale inhibitor added, that is, the pre - treated product water, passes through a nanofiltration membrane device under a pressure of 2.5 MPa. The nanofiltration product water enters a reverse osmosis membrane device under a pressure of 6.5 MPa to produce concentrated brine. 15% dilute sulfuric acid is added to the concentrated brine to adjust the pH to 3. After the acidified concentrated brine is made, it is sent to an air - blowing acid - process bromine extraction device.

[0068] Since the device is put into operation according to the above parameters, the water intake temperature, concentrated brine temperature, and bromine extraction rate are sampled and detected every 4 hours. 30 days is recorded as one operation cycle, and the operation indicators are as shown in Table 4 above. The average bromine extraction rate of the bromine extraction device within a 30 - day cycle is 76%.

[0069] Control example:

[0070] The average value of the water intake index within the operation cycle is as follows in Table 6:

[0071]

[0072] Table 6

[0073] Through valve control, concentrated brine by - products of membrane seawater desalination are taken. After passing through a multi - media filter and an ultra - filtration membrane device, the pH value is adjusted to 6.5 with 37% hydrochloric acid, and 2 ppm of scale inhibitor is added. The mixed concentrated brine with the pH value adjusted and the BASF Sokalan PM 15I scale inhibitor added, that is, the pre - treated product water, passes through a nanofiltration membrane device under a pressure of 2.5 MPa. The nanofiltration product water enters a reverse osmosis membrane device under a pressure of 6.5 MPa to produce concentrated brine. 15% dilute sulfuric acid is added to the concentrated brine to adjust the pH to 3. After the acidified concentrated brine is made, it is sent to an air - blowing acid - process bromine extraction device.

[0074] Since the device is put into operation according to the above parameters, the water intake temperature, concentrated brine temperature, and bromine extraction rate are sampled and detected every 4 hours. 30 days is recorded as one operation cycle, and the operation indicators are as shown in Table 6 above. The average bromine extraction rate of the bromine extraction device within a 30 - day cycle is 62%.

[0075] The present invention is not limited to the examples listed above. The structures shown in the drawings are only used to cooperate with the content disclosed in the specification for those skilled in this technology to understand and read, and are not used to limit the implementation conditions of the present invention. Any modification in the process method, change in the proportional relationship, or adjustment in size, without affecting the effects that the present invention can produce and the purposes that can be achieved, should still fall within the scope that can be covered by the technical content disclosed in the present invention.

Claims

1. A method for efficiently extracting bromine from concentrated seawater using waste heat is carried out according to the following steps: S1. Take the concentrated seawater by - products from thermal seawater desalination and the concentrated seawater by - products from membrane seawater desalination. After pretreatment, mix them to make mixed concentrated seawater; S2. Most of the Ca 2+ , Mg 2+ and SO4 2- are removed from the concentrated seawater mixture through a nanofiltration membrane device to produce a mixed nanofiltration product water; S3. The mixed nanofiltration product water is made into concentrated brine after the NaCl concentration is increased by a reverse osmosis membrane device; S4. Sulfuric acid is added to the concentrated brine to make acidified concentrated brine; S5. The acidified concentrated brine is sent to a bromine extraction device to extract bromine; In step S1, the concentrated seawater by - products from thermal seawater desalination, after passing through a sand filter in sequence, are mixed with the concentrated seawater by - products from membrane seawater desalination and then enter a multi - media filter to remove impurities, and then enter the pretreatment product water tank after being filtered by an ultra - filtration membrane device; In step S1, the mixed concentrated seawater made has a stable turbidity and is lower than 1 NTU; Adjust the pH of the mixed concentrated seawater to 6 - 6.5 with hydrochloric acid, add a scale inhibitor at 2 - 3 ppm, and remove more than 90% of Ca 2+ , Mg 2+ and SO4 2- through a nanofiltration membrane device under a pressure of 2.2 - 3 MPa to produce mixed nanofiltration product water; In step S1, the amount of the concentrated seawater by - products from membrane seawater desalination taken is 0.5 - 2 times the volume of the concentrated seawater by - products from thermal seawater desalination. When the external environmental temperature is low, the volume ratio of the concentrated seawater by - products from thermal seawater desalination is higher. When the external environmental temperature is high, the volume ratio of the concentrated seawater by - products from thermal seawater desalination is lower, and it is dynamically adjusted according to the required ratio; The temperature of the concentrated seawater by - products from thermal seawater desalination in step S1 is 40 - 45 °C; The NaCl concentration of the concentrated brine made in step S3 is 110 - 120 g / l, the Br ion concentration is 0.2 - 0.24 g / l, and the temperature is 20 - 28 °C.

2. The method for efficiently extracting bromine from concentrated seawater by using waste heat according to claim 1, wherein The pH value of the acidified concentrated brine in step S4 is 2.5 - 3.

5.

3. The method for efficiently extracting bromine from concentrated seawater using waste heat according to claim 1, characterized in that, The bromine extraction device used in step S5 is an air - blowing acid - method bromine extraction device, and its main process flow includes oxidation, blowing, absorption and enrichment, distillation, condensation, washing and bromine water separation.

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