A method for producing sodium bromide using brine as raw material

Abstract

A method for producing sodium bromide by using brine as raw material, comprising the following steps: (1) acidifying the brine containing bromine and adding sodium bromate to obtain mixed brine, and bromine is generated by reaction in the brine; (2) blowing out the bromine in the mixed brine and absorbing it with lye to obtain an absorption completion liquid; (3) evaporating the absorption completion liquid to precipitate sodium bromate, separating and obtaining sodium bromate and filtrate 1; (4) cooling the filtrate 1 to 25-45 DEG C, adding solid sodium hydroxide to the filtrate 1 to precipitate sodium bromide, and separating to obtain sodium bromide product. The method does not need to convert the blown-out bromine into hydrobromic acid, does not need to consume another reducing agent, and greatly reduces the evaporation energy consumption, and is a method for realizing chlorine-free and low-chlorine production of sodium bromide by using self-produced sodium bromate instead of liquid chlorine in the production process. In the method, chlorine is not used as raw material in the blowing-out gas, chlorine gas is not brought out, the obtained sodium bromide basically does not contain sodium chloride, impurities are easy to separate, and after washing, the purity is high, reaching the quality requirements of national standard products.

Description

Technical Field

[0001] This invention relates to a method for producing sodium bromide, and more particularly to a method for producing sodium bromide using brine as a raw material. Background Technology

[0002] There are three main processes for preparing sodium bromide. One is the neutralization method, which involves reacting sodium hydroxide with hydrobromic acid or sodium carbonate with hydrobromic acid to obtain sodium bromide through acid-base neutralization. Another is the reduction method, which uses reducing agents such as urea, hydrogen peroxide, iron filings, sodium oxalate, etc., to carry out a reduction reaction in the presence of bromine to obtain sodium bromide. The third is the ion exchange method.

[0003] The direct production of sodium bromide from brine typically involves steps such as acidification, oxidation, blowing, absorption, and evaporation. Currently operating equipment uses liquid chlorine as the oxidant, employing alkaline solution to absorb urea for reduction, and then evaporating the resulting absorbed liquid. However, the purity of the obtained sodium bromide product is low, containing impurities such as sodium carbonate, sodium bromate, and sodium chloride. Using liquid chlorine as a raw material poses certain safety risks during the production process, and the low purity of the resulting sodium bromide affects the product's selling price. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for producing sodium bromide using brine as raw material, which reduces the use of liquid chlorine, makes the production operation safer, and produces sodium bromide products with higher purity.

[0005] The technical solution adopted by this invention to solve its technical problem is a method for producing sodium bromide using brine as raw material, comprising the following steps: (1) Acidify the brine containing bromine to pH 2-4, add sodium bromate, so that the molar ratio of total bromine to total sodium bromate in the brine containing bromine is 5:1-1.1, and obtain mixed brine. Oxidation reaction occurs in the mixed brine to produce bromine, which is retained in the mixed brine. If too little sodium bromate is added here, the bromine in the brine cannot be effectively extracted; if too much sodium bromate is added, it will be wasted.

[0006] In step (1), the bromine content in the brine containing bromine in the raw material is above 60 mg / L. Underground brine, potassium extraction mother liquor, and sun-dried salt brine are all acceptable. The bromine in the raw material brine exists in the form of bromide ions.

[0007] Furthermore, in step (1), sodium bromate is preferably added as a sodium bromate solution, more preferably with a concentration of 0.5-29 wt%, and even more preferably with a concentration of 20-29 wt%. Studies have shown that adding sodium bromate in solution form is easier to handle. Moreover, a higher solution concentration is more conducive to the reaction.

[0008] Furthermore, the sodium bromate solution added in step (1) is generated in step (3).

[0009] (2) The bromine in the mixed brine obtained in step (1) is blown out by circulating air, and then absorbed by alkaline solution. The alkaline solution reacts with the bromine to obtain the absorption completed liquid. Furthermore, in step (2), the alkaline solution used is a sodium hydroxide solution.

[0010] Furthermore, the alkaline solution used in step (2) is the one produced in step (4).

[0011] Furthermore, in step (2), the hydroxide ion concentration of the remaining alkaline solution in the absorption solution is 0.2-0.4 mol / L.

[0012] Using recirculated air for air blowing can improve the bromine blowing rate. Retaining the alkalinity in the absorbent is beneficial for the stable production of sodium bromate.

[0013] (3) Evaporate the absorption liquid obtained in step (2) until sodium bromate precipitates, separate it, and obtain sodium bromate and filtrate 1; Furthermore, in step (3), evaporation is carried out under normal or reduced pressure. The absorbed liquid is evaporated to a sodium bromide content of 44-48 wt%. Excessive evaporation will result in the precipitation of a mixture of sodium bromate and sodium bromide, causing a loss of sodium bromide product.

[0014] Furthermore, in step (3), the obtained sodium bromate is dissolved in water to a concentration of 0.5-29 wt%, which is a sodium bromate solution used as an oxidant in step (1).

[0015] Furthermore, in step (3), the sodium bromide content in filtrate 1 is 44-48 wt%.

[0016] (4) Cool the filtrate 1 to 25-45℃, add sodium hydroxide solid to the filtrate 1, sodium bromide precipitates, and separate sodium bromide and filtrate 2. The product is obtained after washing with sodium bromide.

[0017] Furthermore, in step (4), filtrate 2 is an alkaline solution containing sodium bromide and sodium bromate, which is used as an alkaline solution and absorbent in step (2).

[0018] Furthermore, in step (4), the amount of sodium hydroxide solid added is calculated based on the concentration of sodium hydroxide in filtrate 2 being 13-27 wt%. If too much sodium hydroxide is added, a mixture of sodium hydroxide and sodium bromide will precipitate; if too little is added, sodium bromide will not be fully precipitated.

[0019] In this step, theoretically, the precipitation temperature of sodium bromide is 50.2℃. Below this temperature, sodium bromide dihydrate will precipitate. However, due to the presence of sodium hydroxide, sodium bromide can also precipitate at 25℃. Therefore, cooling to 25-45℃ will precipitate sodium bromide.

[0020] Evaporation can partially separate sodium bromide and sodium bromate, but the solubility of both decreases with temperature, making conventional cooling-based separation unsuitable for this system. This invention provides a simple method to separate relatively pure sodium bromide as the product and enables the effective reuse of sodium bromate.

[0021] In bromine production, the alkaline absorption process involves the coexistence of sodium bromide and sodium bromate. Sodium bromide is purified and used as the product, while sodium bromate is recycled back into the raw brine to adjust the pH, thus converting it into bromine. Air is blown out, alkaline solution absorbs the bromine, and after separation, the sodium bromate is recycled. This process is more economical, replacing the conventional oxidant liquid chlorine. Production operations are safer, and the blown-out air does not contain chlorine, preventing the introduction of excessive chloride ions into the absorption liquid. Furthermore, because sodium bromate is separated from sodium bromide, the purity of the sodium bromide product is improved, meeting national standards. This invention utilizes self-produced sodium bromate to replace liquid chlorine as an oxidant in the production of sodium bromide, improving the environmental safety and greenness of the production process and resulting in high-quality products.

[0022] The principle of this invention is as follows: Under acidic conditions, sodium bromate reacts with sodium bromide to produce bromine (reaction process shown in reaction formula 1). During absorption, sodium hydroxide converts the bromine into a mixture of sodium bromate and sodium bromide (reaction process shown in reaction formula 2). During the evaporation of the absorption liquid, due to the high solubility of sodium bromide and the low solubility of sodium bromate, the difference in solubility between sodium bromate and sodium bromide is utilized to partially precipitate and reuse sodium bromate. The crystallization temperature of filtrate 1 is controlled, and sodium hydroxide is added as a salting-out agent to precipitate sodium bromide. After washing and drying, the product is obtained.

[0023] The reaction formulas involved are as follows:

[0024] Compared with the prior art, the present invention has the following beneficial effects: (1) Compared with the neutralization method, it is not necessary to convert bromine into hydrobromic acid; compared with the reduction method, it is not necessary to consume a reducing agent; compared with the ion exchange method, the evaporation amount is greatly reduced. A method for producing sodium bromide with self-produced sodium bromate instead of liquid chlorine to achieve chlorine-free or low-chlorine production.

[0025] (2) In this invention, when bromine is blown out, chlorine gas is not carried out in the blown gas, and the obtained sodium bromide is basically free of sodium chloride, making it easy to separate impurities. After washing, the purity is high and meets the national standard product quality requirements. Detailed Implementation

[0026] The present invention will be further described below with reference to specific embodiments.

[0027] Table 1 below shows the content requirements for first-grade sodium bromide in the industrial sodium bromide product standard HG / T3809-2023.

[0028] Table 1. Industrial sodium bromide product standard HG / T3809-2023, Class I product contents are as follows: (The main content, calculated as NaBr, must be above a certain value (w%), while other parameters must be below a certain value.)

[0029] In the examples, the analysis and determination of sodium bromide and chloride were performed using potentiometric titration. Example 1

[0030] In this embodiment, potassium extraction mother liquor is used as the raw material, and its composition is shown in Table 2 below: Table 2

[0031] This embodiment describes a method for producing sodium bromide using potassium extraction mother liquor as raw material, including the following steps: (1) Add hydrochloric acid to 5000g of potassium extraction mother liquor to adjust the pH value to 2, and then add 75g of sodium bromate solution with a mass concentration of 5% to obtain mixed brine. Detect the conversion of bromine element into bromine. (2) The bromine in the mixed brine obtained in step (1) is blown out by circulating air and absorbed by a 13wt% sodium hydroxide solution until the sodium hydroxide content is 0.3mol / L (mass concentration 1.2%). The reaction is stopped by circulating the tail gas. The main reaction formula is reaction two, and 42g of the absorption solution of sodium hydroxide, sodium bromate and sodium bromide is obtained. (3) Evaporate 42g of the absorption liquid obtained in step (2) to a sodium bromide content of 48wt%, precipitate solid, filter and separate while hot to obtain 2.6g of sodium bromate, sodium bromate with a water content of about 10%, and obtain filtrate 1; (4) Cool the filtrate 1 to 25°C, add 5g of sodium hydroxide solid, precipitate sodium bromide, filter and separate to obtain 4.6g of sodium bromide with a water content of about 10%, and obtain filtrate 2 with a sodium hydroxide mass concentration of 27wt%; wash the sodium bromide, separate again, collect the wash water for reuse, and test the sodium bromide product.

[0032] Testing showed that the sodium bromide obtained in this example had a purity of 99.1 wt%, which meets the first-class standard for industrial sodium bromide products. Example 2

[0033] In this embodiment, potassium extraction mother liquor was used as the raw material, and its composition is shown in Table 2: This embodiment describes a method for producing sodium bromide using potassium extraction mother liquor as raw material, including the following steps: (1) Add hydrochloric acid to 10 tons of potassium extraction mother liquor to adjust the pH value to 2, and then add 0.38 tons of sodium bromate solution with a mass concentration of 20%. After mixing, the bromine in the potassium extraction mother liquor is converted into bromine. (2) The bromine in the mixed brine obtained in step (1) is blown out by circulating air and absorbed by filtrate 2 (sodium hydroxide solution is used when there is no filtrate 2 at the beginning) until the sodium hydroxide content is 0.3 mol / L (mass concentration 1.2%). The tail gas is circulated for absorption. The absorption reaction formula is reaction 2. The reaction is stopped and 0.92 tons of absorption liquid containing sodium hydroxide, sodium bromate and sodium bromide are obtained. (3) Evaporate the absorption liquid obtained in step (2) to a sodium bromide content of 48wt%, precipitate a solid phase, filter and separate it while hot to obtain 0.075 tons of sodium bromate, the sodium bromate has a water content of about 10%, and obtain filtrate 1; (4) Cool the filtrate 1 to 25°C, add 0.12 tons of sodium hydroxide solid, precipitate sodium bromide, filter and separate to obtain 0.258 tons of sodium bromide with a water content of about 10%, and obtain filtrate 2 with 27 wt% sodium hydroxide in the filtrate; wash the sodium bromide, separate again, collect the wash water for reuse, and test the sodium bromide product.

[0034] Testing showed that the sodium bromide obtained in this example had a purity of 98.6 wt%, which meets the first-class standard for industrial sodium bromide products. Example 3

[0035] In this embodiment, underground brine is used as the raw material, with a bromide ion content of 100 mg / L. The production of sodium bromide includes the following steps: (1) Add hydrochloric acid to 600 cubic meters of underground brine to adjust the pH value to 2, then add 0.1 tons of sodium bromate solution with a mass concentration of 25%. After mixing, the bromine in the potassium extraction mother liquor is converted into bromine. (2) The bromine in the mixed brine obtained in step (1) is blown out by circulating air and absorbed by the filtrate 2 returned from the downstream section (sodium hydroxide solution is used when there is no filtrate 2 at the beginning) until the sodium hydroxide content is 0.3 mol / L (mass concentration 1.2%). The tail gas is then circulated for absorption to obtain 2.85 tons of absorption liquid containing a mixture of sodium hydroxide, sodium bromate and sodium bromide. (3) Evaporate the absorption liquid obtained in step (2) to a sodium bromide content of 48wt%, precipitate a solid phase, filter and separate it while hot to obtain 0.233 tons of sodium bromate, the sodium bromate has a water content of about 10%, and obtain filtrate 1; (4) Cool the filtrate 1 to 25°C, add 0.37 tons of sodium hydroxide solid, precipitate sodium bromide, filter and separate to obtain 0.795 tons of sodium bromide with a water content of about 10%, and obtain filtrate 2 with 27 wt% sodium hydroxide in the filtrate; wash the sodium bromide, separate again, collect the wash water for reuse, and test the sodium bromide product.

[0036] Testing showed that the sodium bromide obtained in this example had a purity of 98.9 wt%, which meets the first-class standard for industrial sodium bromide products.

Claims

1. A method for producing sodium bromide from brine, characterized in that, Includes the following steps: (1) Acidify the brine containing bromine to pH 2-4, add sodium bromate, and make the molar ratio of total bromine in the brine containing bromine to the total sodium bromate added 5:1-1.1 to obtain mixed brine. Oxidation reaction occurs in the mixed brine to produce bromine, which is retained in the mixed brine. (2) The bromine in the mixed brine obtained in step (1) is blown out by circulating air, and then absorbed by alkaline solution. The alkaline solution reacts with the bromine to obtain the absorption completed liquid. (3) Evaporate the absorption liquid obtained in step (2) until sodium bromate precipitates, separate it, and obtain sodium bromate and filtrate 1; (4) Cool the filtrate 1 to 25-45℃, add sodium hydroxide solid to the filtrate 1, sodium bromide precipitates, and separate sodium bromide and filtrate 2. The product is obtained after washing with sodium bromide.

2. The method for producing sodium bromide from brine as a raw material according to claim 1, characterized in that, In step (1), the bromine content in the brine containing bromine is above 60 mg / L.

3. The method for producing sodium bromide from brine as a raw material according to claim 1 or 2, characterized in that, In step (1), sodium bromate is added in the form of a sodium bromate solution.

4. The method for producing sodium bromide from brine as a raw material according to claim 3, characterized in that, In step (1), the concentration of sodium bromate solution is 0.5-29 wt%.

5. The method for producing sodium bromide from brine as a raw material according to claim 1 or 2, characterized in that, The sodium bromate solution added in step (1) is generated in step (3); and / or the alkali solution used in step (2) is generated in step (4).

6. The method for producing sodium bromide from brine as a raw material according to claim 1 or 2, characterized in that, In step (2), the alkaline solution used is a sodium hydroxide solution; and / or, in the absorption completion solution of step (2), the hydroxide ion concentration of the remaining alkaline solution is 0.2-0.4 mol / L.

7. The method for producing sodium bromide from brine according to claim 1 or 2, characterized in that, In step (3), evaporation is performed at atmospheric pressure or under reduced pressure; and / or, the absorbent liquid is evaporated to a sodium bromide content of 44-48 wt%.

8. The method for producing sodium bromide from brine according to claim 1 or 2, characterized in that, In step (3), the obtained sodium bromate is dissolved in water to a concentration of 0.5-29 wt%, which is a sodium bromate solution used as an oxidant in step (1).

9. The method for producing sodium bromide from brine according to claim 1 or 2, characterized in that, In step (3), the sodium bromide content in filtrate 1 is 44-48 wt%.

10. The method for producing sodium bromide from brine according to claim 1 or 2, characterized in that, In step (4), the amount of sodium hydroxide solid added is calculated based on the concentration of sodium hydroxide in filtrate 2 being 13-27 wt%.

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