Method and device for preparing sodium bromide from potassium salt old brine

Abstract

The invention relates to the technical field of brine resource utilization, and discloses a method and device for preparing sodium bromide from potassium salt old brine, after the old brine is pretreated, bromide ions in the old brine are oxidized into elemental bromine in an electrolytic bath, and the old brine circulates to a flowing electrode capacitance deionization device in the oxidation process to remove chloride ions; the method comprises the following steps: dissolving and extracting an oxidized bromine simple substance, reacting with a sodium-containing solution, adding activated carbon into a reaction solution, concentrating and evaporating the solution to dryness, adding desalted water, leaching, filtering, and concentrating and drying a sodium bromide filtrate to obtain a sodium bromide product. According to the method, electrooxidation and extraction processes are used for potassium salt old halogen bromine extraction for the first time, an electrooxidation method is coupled with an existing extraction method, excellent bromine extraction efficiency is achieved, and green and environment-friendly processes are achieved. And the problems of low efficiency, chlorine and acid use risks and environmental risks in the current old brine acidification oxidation reaction system can be solved, and the possibility of later industrialization can be realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of brine resource utilization, and particularly relates to a method for preparing sodium bromide from old brine of potassium salt and a device thereof. BACKGROUND

[0002] Bromine is rare in the earth's crust, but it is widely distributed. It is a volatile liquid and a strong dispersion element. Bromine has chemical properties similar to chlorine. Compounds formed by bromine and alkali metals or alkaline earth metals are soluble in water and various organic solvents, have the characteristics of easy melting, low boiling point, and strong dispersion. Due to these characteristics, the distribution of bromine in the earth's crust is mainly in the form of various bromide ions, which are scattered in the water layer of the earth's crust. Places in nature with relatively high bromine concentration are underground salt brine in oil and gas fields, salt lake brine, and MgCl, NaCl type concentrated salt brine and brine in potassium salt mine.

[0003] At present, the industrialized production methods for extracting bromine are steam distillation and air blowing. Among them, air blowing is widely used. Steam distillation is the earliest method for extracting bromine in chemical applications. The brine is acidified and enters a packed column, where the bromide ions are oxidized to free bromine by countercurrent chlorine. Then, in the condensation tower, bromine is distilled out by using the difference in volatility between water and bromine. The bromine product can be obtained by static layering of the distillate. The disadvantage of this method is that the bromine content in the brine cannot be less than 5-24 g / L. At the same time, due to the high temperature in the distillation process, many side reactions occur, such as dissociation of free bromine and reaction of bromine with excess chlorine, which ultimately affect the oxidation rate and blowing rate. Air blowing is the main method for producing bromine in China at present, and it is very suitable for extracting bromine from solutions with low bromine content, such as concentrated seawater in the salt production process and underground brine. The principle is as follows: first, the bromide ions in the brine are oxidized to bromine by chlorine, and then the bromine is blown out of the brine by air. After being absorbed by the absorbent, chlorine is added, and free bromine is separated out under the action of water vapor, and bromine is obtained by condensation. The disadvantage is that the brine temperature needs to be controlled in the range of 15-20℃, the equipment required is large, the product purity needs to be further improved by distillation, and the industrial blowing rate is low and the energy consumption is large. The current bromine extraction process requires the use of chlorine and acid for pretreatment of the brine, and the acidification and oxidation efficiency is low. Chlorine and acid are dangerous chemicals, and there are great safety hazards and the possibility of environmental pollution in the production and use process. SUMMARY

[0004] The purpose of the present application is to provide a method for preparing sodium bromide from old brine of potassium salt and a device thereof, which solves the problems of low efficiency, safety and pollution in the prior art.

[0005] The scheme of the present application is as follows: A method for preparing sodium bromide from old brine of potassium salt, characterized by comprising the following steps: 1) Pretreatment, the old brine is pretreated by filtering and sedimentation to remove the insoluble particle decomposition mother liquor, enters the storage tank, and then carbon dioxide gas is introduced to carry out impurity removal reaction, and the pH is adjusted to 3-6 to obtain solution D1; 2) Solution D1 is separated by filtration to obtain filter residue M1 and filtrate D2; 3) The filtrate D2 is sent to an electro-oxidation device for oxidation treatment, and in the oxidation process, the brine is pumped into a flow electrode capacitor deionization device for cyclic dechlorination, and finally solution D3 is obtained; 4) Solution D3 is sent to the extraction tower of the extraction and stripping device, and a composite extractant is added to carry out extraction reaction, and after the extraction is completed, the organic phase enters the stripping tower of the extraction and stripping device; 5) After adding a stripping agent, mixed solution D4 is obtained; 6) The mixed solution D4 is added with activated carbon, stirred for 2-4 h, concentrated and evaporated to dryness to obtain material D5; 7) The material D5 is leached with desalted water, stirred for 1-2 h, and then filtered to obtain mother liquor D6 and filter residue M2; 8) After concentration, crystallization and drying of the mother liquor D6, sodium bromide product is obtained.

[0006] Its working principle is: After pretreatment of the old brine, the bromide ions in the old brine are oxidized to bromine in the electrolytic cell, and part of the brine is pumped out of the flow electrode capacitor deionization device for dechlorination before being introduced into the electrolytic cell for oxidation. The bromine is oxidized and then dissolved and extracted, and then reacts with a sodium-containing solution. Then, nano-activated carbon powder is added to the reaction solution, the solution is concentrated and evaporated to dryness, then desalted water is added for leaching, and after filtration, the sodium bromide filtrate is concentrated and dried to obtain sodium bromide product.

[0007] The stripping process occurs as follows: The reaction can be considered as an instantaneous irreversible reaction, so the reaction kinetics resistance can be ignored.

[0008] As a preferred technical solution, the old brine in the 1) step is one of potassium salt mine old brine or evaporated concentrated brine, and the bromide ion content in the old brine is 3.2 g / L-6.5 g / L.

[0009] As a preferred technical solution, the electrolytic cell of the electro-oxidation device in the 3) step comprises an anode tank and a cathode tank, and the anode tank and the cathode tank are separated by an ion-selective membrane; during electro-oxidation, the anode current density is 5-8 A / m 2, electrolyte temperature is 30-40 DEG C; the flow rate of anode electrolyte is 20-22 L / h, temperature is 25-30 DEG C, electrolytic voltage is 1.2-1.6 V; electrolytic time is 40 min-100 min; anode is metal sulfide, cathode is nanometer graphite; the metal sulfide is one of CoS2 / CoS, Cu7S4, CdS, MnS, FeS2, NiS2.

[0010] As a preferred technical scheme, the composite extractant in the 4) step is one or a combination of butyl acetate, phenylmethyl acetate, ethyl butyrate, butyl benzoate, pentylamine, bromo-tetradecyl, carbon disulfide, carbon tetrachloride; the extraction temperature is 35-40 DEG C, and the extraction time is 40-60 min; the mixed solution D4 is a solution containing sodium bromide and sodium bromate; the volume ratio of the composite extractant to the solution D3 is 1:0.3-0.6.

[0011] As a preferred technical scheme, the stripping agent in the 5) step is one or a combination of 30%-40% sodium hydroxide and sodium carbonate aqueous solution; the stripping temperature is 25-30 DEG C, the stripping time is 30-90 min, and the volume ratio of the stripping agent to the organic phase is 5:20-30.

[0012] As a preferred technical scheme, the particle size of the activated carbon in the 6) step is 80 mesh, the specific surface area is 1350 cm 2 / g, and the total pore volume is 0.84 cm 3 / g; the material D5 is a mixture of sodium bromide and sodium bromate.

[0013] As a preferred technical scheme, the carbon dioxide gas purity in the 1) step is 95%; the filter residue M1 in the 2) step is a mixture of magnesium carbonate and calcium carbonate.

[0014] As a preferred technical scheme, the solution D6 in the 7) step is a sodium bromide solution, and the filter residue M2 is a solid mixture rich in sodium bromate and industrial salt.

[0015] As a preferred technical scheme, the electro-oxidation device comprises a treatment part and an electro-oxidation part, the treatment part comprises an acidification settling tank, a carbon dioxide gas inlet pipe extends into the acidification settling tank and is communicated with a carbon dioxide gas distribution pipe, a plurality of stirring paddles are arranged in the acidification settling tank, one end of the bottom of the acidification settling tank is communicated with a decomposition mother liquor inlet pipe, and an overflow port of the acidification settling tank is communicated with the top of a premixing tank of the electro-oxidation part through a pipeline.

[0016] As a preferred technical scheme, the extraction and stripping device comprises two towers, a plurality of Pall rings filled with fillers are arranged in the bottom of the tower, a reverse tapered tray is arranged above the fillers, tray fixing rods are arranged around the tray, the tray fixing rods are located in the tower, the two towers are an extraction tower and a stripping tower respectively, an electrolyte inlet is arranged at the upper portion of the extraction tower, an extractant inlet is arranged at the bottom of the extraction tower, an extractant outlet at one side of the upper portion of the extraction tower is communicated with the liquid inlet of an extractant circulating pump through a pipeline, the liquid outlet of the extractant circulating pump is communicated with an extraction static mixer and a stripping tower liquid inlet through pipelines respectively, the bottom of the extraction tower is communicated with the extraction static mixer through an electrolyte circulating pump, and the extraction static mixer is communicated with the extractant inlet.

[0017] Advantages of the present application: (1) The method for preparing sodium bromide from potassium salt old brine by combining the electro-oxidation method with the extraction separation method, realizes chlorine-free oxidation, and has strong environmental protection.

[0018] (2) The method for preparing sodium bromide from potassium salt old brine by the present application, passes in carbon dioxide gas, precipitates magnesium and calcium ions in the decomposition mother liquor, adjusts the pH value of the solution, and removes impurities in the mother liquor.

[0019] (3) The method for preparing sodium bromide from potassium salt old brine by the present application has a high extraction efficiency for high-content bromine in the potassium salt mine old brine, and the extraction rate of bromine is 85-95%. In view of the characteristics of high chlorine in the old brine, the flow electrode capacitive deionization technology (FCDI) is used to remove chlorine ions, the generation of chlorine gas is inhibited in the electro-oxidation process, it is green and environmental protection, and the obtained sodium bromide product has high purity.

[0020] (4) The method for preparing sodium bromide from potassium salt old brine according to the application, the anode material used in the electro-oxidation is not easy to be corroded, and the anode surface is not corroded after the method according to the application is continuously operated for one month.

[0021] (5) The method for preparing sodium bromide from potassium salt old brine according to the application, the high oxidation efficiency can be achieved at a low electrode potential.

[0022] (6) The device used in the method for preparing sodium bromide from potassium salt old brine according to the application is combined by an electro-oxidation device and an extraction and stripping device, the electro-oxidation and extraction processes are used for potassium salt old brine bromine extraction for the first time, the electro-oxidation method is coupled with the existing extraction method, the excellent bromine extraction efficiency is achieved, and the process is green and environmentally friendly; the low efficiency, the use risk of chlorine gas and acid, and the environmental risk in the current old brine acidification and oxidation reaction system can be solved, and the possibility of industrialization in the later period is realized. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical means, creative features, purposes and effects realized by the application, the following will further describe the application with reference to the specific embodiments.

[0024] Figure 1 The process flow chart of the application; Figure 2 The electro-oxidation device structure schematic diagram of the embodiment of the application; Figure 3 The extraction and stripping device structure schematic diagram of the embodiment of the application; 1-acidification settling tank; 2-carbon dioxide inlet pipe; 3-decomposition mother liquor inlet pipe; 4-carbon dioxide gas distribution pipe; 5-multistage stirring paddle; 6-overflow port; 7-premixing tank; 8-anode tank; 9-anode stirring paddle; 10-ion selective permeation membrane; 11-cathode tank; 12-cathode; 13-electrolysis voltage; 14-outlet; 15-anode; 16-premixing stirring paddle; 17-packing; 18-tray; 19-tray fixing rod; 20-extraction column; 21-stripping column; 22-electrolyte inlet; 23-extraction agent inlet; 24-extraction agent circulating pump; 25-extraction static mixer; 26-electrolyte circulating pump; 27-sodium bromide circulating pump; 28-stripping static mixer; 29-stripping agent circulating pump; 30-stripping agent inlet; 31-sodium bromide solution; 32-oxidized brine. DETAILED DESCRIPTION

[0025] In order to make the technical means, creative features, purposes and effects realized by the application easy to understand, the following will further describe the application with reference to the specific embodiments.

[0026] The following examples are analyzed and tested for the Laos potash Laohuo, and the following results are obtained: Table 1 Analysis and detection of Laohuo composition Example 1 Step 1, the Laos potash Laohuo, after filtering and settling pretreatment to remove insoluble particles, the decomposition mother liquor is put into a storage tank, then 95% pure carbon dioxide gas is introduced for purification reaction, the stirring reaction time is 1 h, the pH of the solution is 3.0, and a solution D1 after impurity removal is obtained.

[0027] Step 2, after the solution D1 after impurity removal is filtered, a filter residue M1 and a filtrate D2 are obtained. The filter residue M1 is a mixture of magnesium carbonate and calcium carbonate, the filter residue M1 is discharged, and the filtrate D2 is put into an electro-oxidation device for oxidation. The anode current density is 5.5 A / m 2 , the electrolysis temperature is 30℃, the electrolysis voltage is 1.2V, and the electrolysis time is 40min. The flow rate of the anode electrolyte is 20L / h.

[0028] During the oxidation process, part of the brine is pumped out, dechlorinated in a flow electrode capacitor deionization device, and then introduced into the electrolytic tank for oxidation, and the flow electrode capacitor deionization device is added with 0.6% activated carbon, the specific surface area of the activated carbon is less than 450m 2 / g, the mesh number is 340, the applied voltage is 2.6V, the brine circulation amount is 38.5mL / min, the flow rate of the electrode liquid in the anode and cathode chambers is 53 mL / min, and the removal rate of chloride ions is 83.65%.

[0029] Step 3, the solution D3 after electrolysis is introduced into an extraction tower, and a composite extractant is added for extraction reaction. The extractant is mixed by volume ratio of butyl acetate: phenylmethyl acetate: carbon tetrachloride = 12:7:4, the volume ratio of the composite extractant and the solution D3 is 1:0.35, the extraction temperature is 35℃, and the time is 40min.

[0030] Step 4, after the extraction is completed, the oil phase of the extraction liquid is introduced into a back extraction tower, a back extraction agent is added, the back extraction agent is 35% sodium hydroxide solution, and back extraction is carried out. The back extraction temperature is 25℃, the time is 30min, and the volume ratio of the back extraction agent to the organic phase is 5:20.

[0031] Step 5, the water phase mixed solution D4 after back extraction is added with activated carbon, stirred and mixed for 2h, and then concentrated and evaporated.

[0032] Step 6: Add desalted water to the evaporated material D5 in a mass ratio of 10:1, stir and react for 1 hour, and then filter and separate to obtain sodium bromide mother liquor D6 and filter residue M2. The filter residue M2 is a solid mixture of enriched sodium bromate and industrial salt.

[0033] Step 7: After the sodium bromide mother liquor D6 is concentrated, crystallized, and dried, a sodium bromide product is obtained, and the bromine extraction rate is 88.34%. The sodium bromide product analysis is shown in Table 2 below: Table 2 Example 2 Step 1: Laotian potassium salt brine is filtered and sedimented to remove insoluble particles from the decomposition mother liquor, which enters a storage tank. Then, 95% pure carbon dioxide gas is introduced for purification reaction. The stirring reaction time is 1 hour, and the pH of the solution is adjusted to 6 to obtain a decontaminated solution.

[0034] Step 2: After the impurities are removed, the solution is filtered to obtain a filter residue and a filtrate. The filter residue is discharged and the filtrate enters the electro-oxidation tank for oxidation. The anode current density is 6.8A / m 2 , the electrolysis temperature is 30℃, the electrolysis voltage is 1.6V, and the electrolysis time is 100min.

[0035] During the oxidation process, part of the brine is pumped out and dechlorinated in the flow electrode capacitor deionization device before entering the electrolytic cell for oxidation. The cycle of oxidation and dechlorination is carried out. 0.6% activated carbon is added to the flow electrode capacitor deionization device. The specific surface area of ​​the activated carbon is less than 450m 2 / g, mesh size is 340 mesh, applied voltage is 2.6V, brine circulation volume is 38.5mL / min, and electrode liquid flow rate in the anode and cathode chambers is 53 mL / min.

[0036] In step 3, the electrolyzed solution enters an extraction tower, where a composite extractant is added to initiate an extraction reaction. The extractant is a mixture of ethyl butyrate, amylamine, and carbon disulfide in a volume ratio of 18:9:15. The volume ratio of the extractant to the electrolyzed solution is 1:0.6. The extraction temperature is 40°C, and the extraction time is 60 minutes.

[0037] In step 4, after the extraction is complete, the oil phase of the extract enters a stripping tower, where a stripping agent (40% sodium carbonate solution) is added and stripping is performed with stirring. The stripping temperature is 30°C and the stripping time is 90 minutes. The volume ratio of stripping agent to organic phase is 5:30.

[0038] Step 5: Add activated carbon to the aqueous phase after stripping, stir and mix for 2 hours, and then concentrate and evaporate to dryness.

[0039] Step 6, add desalted water to the evaporated material, the mass ratio of desalted water to material is 15:1, after stirring for 1 h, filter separation to obtain sodium bromide mother liquor and filter residue.

[0040] Step 7, after concentration, crystallization and drying of the sodium bromide mother liquor, the sodium bromide product is obtained, and the extraction rate of bromine is 93.40%. The sodium bromide product is analyzed as shown in Table 3: Table 3 Example 3 Step 1, the old Laos potash old brine is pretreated by filtration and sedimentation to remove insoluble particles in the decomposition mother liquor, and then enters the storage tank, and then 95% pure carbon dioxide gas is introduced for purification reaction, the stirring reaction time is 1 h, the pH of the solution is 4.0, and the impurity-removed solution is obtained.

[0041] Step 2, after the impurity-removed solution is filtered, filter residue and filtrate are obtained. The filter residue is discharged, and the filtrate enters the electro-oxidation tank for oxidation. The anode current density is 8 A / m 2 , the electrolysis temperature is 40℃, the electrolysis voltage is 1.5V, and the electrolysis time is 100min.

[0042] During the oxidation process, part of the brine is pumped out, dechlorinated in a flow electrode capacitive deionization device, and then oxidized in the electrolysis tank. The flow electrode capacitive deionization device adds 0.6% activated carbon, the specific surface area of the activated carbon is less than 450m 2 / g, the mesh number is 340 mesh, the applied voltage is 2.6V, the brine circulation amount is 38.5mL / min, and the anode and cathode chamber electrode liquid flow rate is 53 mL / min.

[0043] Step 3, the electrolysis completed solution enters the extraction tower, and a composite extractant is added for extraction reaction. The volume ratio of the extractant is benzylic acid butyl ester: brominated fourteen stubborn: carbon disulfide = 18:3:20, the volume ratio of the extractant and the electrolysis completed liquid is 1:0.55, the extraction temperature is 38℃, and the time is 55min.

[0044] Step 4, after the extraction is completed, the oil phase of the extraction liquid enters the back extraction tower, and a back extraction agent is added, which is 38% sodium hydroxide solution, for stirring back extraction. The back extraction temperature is 28℃, the time is 65min, and the volume ratio of the back extraction agent to the organic phase is 5:25.

[0045] Step 5, the back-extracted water phase is added with activated carbon, stirred and mixed for 2 h, and then concentrated and evaporated.

[0046] Step 6, add desalted water to the evaporated material, the mass ratio of desalted water to material is 15:1, after stirring for 1 h, filter separation to obtain sodium bromide mother liquor and filter residue.

[0047] Step 7, the sodium bromide mother liquor was concentrated, crystallized and dried to obtain sodium bromide product, the extraction rate of bromine was 95.45%. The sodium bromide product was analyzed as shown in Table 4: Table 4 Example 4 The electro-oxidation device structure used in the above examples is shown in Figure 2 The acidification settling tank 1, the carbon dioxide gas inlet pipe 2 extending into the acidification settling tank 1 and communicating with the carbon dioxide gas distribution pipe 4, the acidification settling tank 1 provided with multiple stirring paddles 5, one end of the bottom of the acidification settling tank 1 communicating with the decomposition mother liquor inlet pipe 3, the overflow port 6 of the acidification settling tank 1 communicating with the top of the premixing tank 7 of the electro-oxidation part through a pipeline, the electro-oxidation part including the premixing tank 7, the anode tank 8 and the cathode tank 11, the overflow channel provided between the premixing tank 7 and the anode tank 8, the ion-selective permeation membrane 10 provided at the communication part of the anode tank 8 and the cathode tank 11, the premixing stirring paddle 16 provided at the top of the premixing tank 4, the positive electrode stirring paddle 9 provided at the top of the anode tank 8, the anode electrode plate 15 provided in the anode tank 8, the discharge port 14 provided at the bottom of the anode tank 8, and the cathode electrode plate 12 provided in the cathode tank 11. The anode is a metal sulfide, and the cathode is nano graphite; the metal sulfide is one of CoS2 / CoS, Cu7S4, CdS, MnS, FeS2 and NiS2.

[0048] Working principle: old brine enters the acidification settling tank 1, 95% carbon dioxide gas is introduced for acidification and impurity removal, under the action of the stirring paddle, the carbon dioxide gas distribution pipe 4 is divided into 4 branches and deeply penetrates into the acidification settling tank 1, and the pipe is full of gas holes. The acidification settled brine enters the premixing tank 7 through the overflow port 6, the catalyst is added to the premixing tank 7 and mixed fully, and the solid slag is discharged through the tank bottom. The brine is subjected to oxidation in the electro-oxidation tank, which is divided into an anode tank 8 and a cathode tank 11, each tank has multiple stacked electrode plates, and the electrode plates are square, with a size of 30*20 cm and a thickness of 2 cm. There is stirring above the anode tank 8 and the cathode tank 11 to make the electrolyte mixed uniformly, and ion exchange is performed through the ion-selective permeation membrane 10 between the anode tank 8 and the cathode tank 11.

[0049] The extraction column and the stripping column used in the above embodiment constitute an extraction and stripping device, the bottom of the column is provided with a Pall ring filled with packing 17, the upper part of the packing 17 is provided with an inverted conical tray 18, the periphery of the tray 18 is respectively provided with a tray fixing rod 19, the tray fixing rod 19 is located in the column, the two columns are an extraction column 20 and a stripping column 21, the upper part of the extraction column 20 is provided with an electrolyte inlet 22, the bottom of the extraction column 20 is provided with an extractant inlet 23, the extractant outlet on one side of the upper part of the extraction column 20 is communicated with the liquid inlet of an extractant circulating pump 24 through a pipeline, the liquid outlet of the extractant circulating pump 24 is respectively communicated with an extraction static mixer 25 and a stripping column liquid inlet through a pipeline, the bottom of the extraction column 20 is communicated with the extraction static mixer 25 through an electrolyte circulating pump 26, the extraction static mixer 25 is communicated with the extractant inlet 23; the upper part of the stripping column 21 is provided with a stripping agent inlet 30, the bottom of the stripping column 21 is communicated with a stripping static mixer 28 through a sodium bromide circulating pump 27, the upper part of the stripping column 21 is communicated with the stripping static mixer 28 through a stripping agent circulating pump 29, the stripping static mixer 28 is communicated with the stripping column liquid inlet 21 through a pipeline.

[0050] Working principle: the extraction column 20 and the stripping column 21 contain two parts, the bottom is a Pall ring filled with packing 17, the upper part is an inverted conical tray 18, the tray 18 has four tray fixing rods 19 fixed in the column. The electrolyte enters from the upper part of the extraction column 20, the composite extractant enters from the bottom, the extractant and the electrolyte are fully mixed and extracted in the extraction column 20, the bromine enters the extractant, the old brine at the bottom of the extraction column 20 is punched into the extraction static mixer 25 by the sodium bromide circulating pump 27, and the extractant is mixed and extracted for the second time, the extractant circulating pump 24 continuously circulates the extractant and the electrolyte containing bromine to carry out the extraction reaction. The extracted extractant enters the stripping column 21, the stripping liquid enters from the upper part of the extraction column 20, the composite extractant containing bromine enters from the bottom, the extractant and the stripping liquid are fully mixed and extracted in the extraction column 20, the bromine enters the stripping agent, the sodium bromide solution 31 at the bottom of the stripping column 21 is punched into the stripping static mixer 28 by the sodium bromide circulating pump 27, and the composite extractant containing bromine is mixed and extracted for the second time, the stripping agent circulating pump 29 continuously circulates the composite extractant containing bromine and the sodium bromide solution to carry out the stripping.

[0051] The basic principle, main features and advantages of the present application are shown and described above. Those skilled in the art should understand that the present application is not limited to the above embodiments, and the above embodiments and descriptions in the specification are only to illustrate the principles of the present application, and various changes and improvements can be made to the present application without departing from the spirit and scope of the present application, and these changes and improvements all fall within the scope of the present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for preparing sodium bromide by using potassium salt halogen, characterized in that: Including the following steps: 1) Pretreatment: The old brine is filtered and sedimented to remove the insoluble particles of the decomposition mother liquor, which enters the storage tank, and then carbon dioxide gas is introduced to perform impurity removal reaction, while adjusting the pH to 3-6 to obtain solution D1; 2) Solution D1 is filtered and separated to obtain residue M1 and filtrate D2; 3) The filtrate D2 is fed into an electro-oxidation device for oxidation. During the oxidation process, the brine is pumped into a mobile electrode capacitive deionization device for cyclic dechlorination, ultimately obtaining solution D3. 4) Solution D3 is fed into the extraction tower of the extraction and stripping device, where a composite extractant is added to initiate an extraction reaction. After the extraction is complete, the organic phase enters the stripping tower of the extraction and stripping device; 5) Add a stripping agent and obtain a mixed solution D4 after stripping; 6) Add activated carbon to the mixture D4, stir for 2-4 hours, and then concentrate and evaporate to dryness to obtain material D5; 7) Material D5 is leached with desalted water, stirred for 1-2 hours, and then filtered to obtain mother liquor D6 and filter residue M2; 8) The mother liquor D6 is concentrated, crystallized and dried to obtain sodium bromide product.

2. A method for preparing sodium bromide by using potassium salt halogen as claimed in claim 1, characterized in that : The old brine in step 1) is one of the old brine from potassium salt mine or the evaporated concentrated brine, and the bromide ion content in the old brine is 3.2g / L to 6.5g / L.

3. A method for preparing sodium bromide by using potassium salt halogen as claimed in claim 1, characterized in that: The electrolytic cell of the electro-oxidation device in step 3) comprises an anode cell and a cathode cell, which are separated by an ion selective permeable membrane; during the electro-oxidation process, the anode current density is 5 to 8 A / m 2 The electrolysis temperature is 30-40°C; the flow rate of the anolyte is 20-22 L / h, the electrolysis voltage is 1.2-1.6 V; the electrolysis time is 40 min-100 mi; the anode is metal sulfide and the cathode is nanographite.

4. A method for preparing sodium bromide by using potassium salt halogen as claimed in claim 1, characterized in that: In step 4), the composite extractant is selected from one or a combination of butyl acetate, benzyl acetate, ethyl butyrate, benzyl benzoate, amylamine, tetradecyl bromide, carbon disulfide, and carbon tetrachloride; the extraction temperature is 35-40° C., and the extraction time is 40-60 minutes; the mixed solution D4 is a solution containing sodium bromide and sodium bromate; and the volume ratio of the composite extractant to solution D3 is 1:0.3-0.

6.

5. A method for preparing sodium bromide by using potassium salt halogen as claimed in claim 1, characterized in that: In step 5), the stripping agent is one or a combination of sodium hydroxide or sodium carbonate aqueous solution with a concentration of 30% to 40%; the stripping temperature is 25 to 30° C., the stripping time is 30 to 90 minutes, and the volume ratio of the stripping agent to the organic phase is 5:20 to 30.

6. A method for preparing sodium bromide by using potassium salt halogen as claimed in claim 1, characterized in that: The particle size of the activated carbon in step 6) is 80 mesh and the specific surface area is 1350 cm 2 / g, total pore volume 0.84cm 3 / g; the material D5 is a mixture of sodium bromide and sodium bromate.

7. A method for preparing sodium bromide by using potassium salt halogen as claimed in claim 1, characterized in that: The purity of the carbon dioxide gas in step 1) is 95%; and the filter residue M1 in step 2) is a mixture of magnesium carbonate and calcium carbonate.

8. A method for preparing sodium bromide by using potassium salt halogen as claimed in claim 1, characterized in that: In step 7), the solution D6 is a sodium bromide solution, and the filter residue M2 is a solid mixture of enriched sodium bromate and industrial salt.

9. A method for preparing sodium bromide by using potassium salt halogen as claimed in claim 1, characterized in that: The electro-oxidation device includes a treatment section and an electro-oxidation section. The treatment section includes an acidification sedimentation tank. The carbon dioxide inlet pipe extends into the acidification sedimentation tank and is connected to the carbon dioxide gas distribution pipe. The acidification sedimentation tank is provided with a multi-stage stirring paddle. One end of the bottom of the acidification sedimentation tank is connected to the decomposition mother liquor inlet pipe. The overflow port of the acidification sedimentation tank is connected to the top of the premixing tank of the electro-oxidation section through a pipeline. The electro-oxidation section includes a premixing tank, an anode tank and a cathode tank. An overflow channel is provided between the premixing tank and the anode tank. An ion selective permeable membrane is provided at the connection between the anode tank and the cathode tank. A premixing stirring paddle is provided at the top of the premixing tank. A positive electrode stirring paddle is provided at the top of the anode tank. A discharge port is provided at the bottom of the anode tank.

10. The method for preparing sodium bromide by using potassium salt halogen as claimed in claim 1, wherein: The extraction and stripping device includes two towers, wherein a ball ring filled with filler is provided at the bottom of the tower, an inverted conical tower plate is provided above the filler, and tower plate fixing rods are provided around the tower plates, and the tower plate fixing rods are located in the towers. The two towers are an extraction tower and a stripping tower, respectively. An electrolyte inlet is provided at the top of the extraction tower, and an extractant inlet is provided at the bottom of the extraction tower. The extractant outlet on one side of the upper part of the extraction tower is connected to the liquid inlet of the extractant circulation pump through a pipeline, and the liquid outlet of the extractant circulation pump is connected to the extraction static mixer and the stripping tower inlet through pipelines respectively. The bottom of the extraction tower is connected to the extraction static mixer through the electrolyte circulation pump, and the extraction static mixer is connected to the extractant inlet; a stripping agent inlet is provided at the top of the stripping tower, and the sodium bromide liquid inlet at the bottom of the stripping tower is connected to the stripping static mixer through the sodium bromide circulation pump. The top of the stripping tower is connected to the stripping static mixer through the stripping agent circulation pump, and the stripping static mixer is connected to the stripping tower inlet through a pipeline.

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