Method for purifying iodide ions in refined brine in ionic membrane chlor-alkali production process

Abstract

The invention provides a method for purifying iodide ions in refined salt water in an ionic membrane chlor-alkali production process. The purification method comprises the following steps: S1, dissolving industrial salt in water to obtain crude brine; s2, adding sodium carbonate and sodium hydroxide into the crude brine, adding ferric trichloride, stirring, standing, and filtering to obtain primary brine; s3, sodium sulfite is added into the primary saline water for reduction, then a hydrochloric acid solution is added, finally, the primary saline water is introduced into ion exchange resin for adsorption, and the ion exchange resin comprises D541 cationic resin and anion resin. According to the invention, the anion resin is added on the basis of the original D541 cation resin, so that iodide ions in the saline water can be effectively reduced, even the iodide ions in the saline water can be reduced to 0.1 mg / L or below, and furthermore, periodate can be effectively prevented from being generated and the service life of an ionic membrane can be prolonged in the electrolysis process of an electrolytic bath; the problem of salt resource waste caused by replacement of salt seeds or discharge of part of salt in a traditional method is effectively solved.

Description

Technical Field

[0001] The invention relates to the technical field of iodine removal from brine in the chlor-alkali industry, and in particular to a method for purifying iodine ions in refined brine in an ion membrane chlor-alkali production process. Background Art

[0002] The chlor-alkali process refers to the method of using saturated salt water to prepare chlorine, hydrogen and caustic soda. With the rapid development of my country's economy, the production capacity of the chlor-alkali industry has expanded rapidly. The main production methods of the chlor-alkali process include the diaphragm process and the ion membrane process. Due to the high energy consumption demand, poor product quality, and serious environmental pollution of the diaphragm process, by the end of 2015, the diaphragm process had been completely eliminated. Compared with the diaphragm process, the ion membrane process has lower energy consumption, less pollution, and good product quality, and has become the mainstream chlor-alkali process production method. However, the ion membrane process has higher requirements on the quality of the brine used for electrolysis. When the iodine content is too high, once it enters the alkaline environment of the ion membrane, the iodine will be oxidized into periodate, forming an insoluble precipitate, resulting in reduced current efficiency and greatly reduced service life of the ion membrane.

[0003] At present, the main method to solve the problem of excessive iodine content in salt water is to discharge it. When the concentration of iodine ions is too high, part of the salt water is usually discharged or the salt type is changed. Although this solution can barely control the iodine content, it seriously wastes salt resources.

[0004] Therefore, the chlor-alkali process using the ion membrane method still requires a method to fundamentally solve the problem of excessive iodine content in brine. Summary of the invention

[0005] 1. Technical issues to be solved

[0006] In view of the deficiencies in the prior art, the present invention provides a method for purifying iodine ions in refined brine in an ion membrane chlor-alkali production process, which uses a renewable ion exchange resin to adsorb iodine ions and solves the problems raised in the above-mentioned background technology.

[0007] (II) Technical solution

[0008] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0009] According to a first aspect of the present invention, there is provided a method for purifying iodine ions in refined brine in an ion-exchange membrane chlor-alkali production process, comprising the following steps:

[0010] S1. Dissolving industrial salt in water to obtain crude brine;

[0011] S2, adding sodium carbonate and sodium hydroxide to the crude brine, then adding ferric chloride and stirring, standing, and filtering to obtain primary brine;

[0012] S3, first adding sodium sulfite to the primary brine for reduction, then adding hydrochloric acid solution, and finally passing the primary brine into an ion exchange resin for adsorption, wherein the ion exchange resin includes D541 cationic resin and anionic resin;

[0013] The regeneration process of the ion exchange resin is as follows: draining - acid soaking regeneration - draining - water washing - draining - alkali regeneration - draining - acid neutralization - draining - water washing - draining - salt water soaking - completion.

[0014] Preferably, the content of anion resin in the ion exchange resin is 2-7%.

[0015] More preferably, the content of anion resin in the ion exchange resin is 5-6%.

[0016] Preferably, the flow rate of the primary brine is 0.008-0.015 m / s, and the residence time is 270-500 s.

[0017] Further preferably, the flow rate of the primary brine is 0.008-0.011 m / s, and the residence time is 400-500 s.

[0018] Preferably, the post-treatment process of the alkaline wastewater generated during the regeneration of the ion exchange resin is: adding an oxidant to the alkaline wastewater for oxidation, heating it to 100°C by steam, and then blowing off iodine by compressed air to make the iodine in the alkaline wastewater less than 0.3 mg / L for reuse.

[0019] Preferably, the oxidant is selected from sodium hypochlorite or hydrogen peroxide.

[0020] Preferably, the concentration of the crude brine is 250-350 mg / L.

[0021] Preferably, sodium bicarbonate and sodium hydroxide are added to the crude brine to adjust the pH of the crude brine to 12-13.

[0022] Preferably, the standing time is 4 to 8 hours.

[0023] Preferably, hydrochloric acid solution is added to the first brine to adjust the pH of the first brine to 8-9.

[0024] (III) Beneficial effects

[0025] The present invention provides a method for purifying iodine ions in refined brine in an ion membrane chlor-alkali production process. It has the following beneficial effects:

[0026] (1) This scheme provides a method for purifying iodine ions in refined brine in an ion membrane chlor-alkali production process. An anion resin is added to the original D541 cationic resin, which can effectively reduce the iodine ions in the brine and even reduce the iodine ions in the brine to below 0.1 mg / L. In addition, during the electrolysis process in the electrolytic cell, the generation of periodate can be effectively avoided, thereby increasing the service life of the ion membrane.

[0027] (2) This scheme provides a method for purifying iodine ions in refined brine in an ion-exchange membrane chlor-alkali production process. The ion exchange resin used can be regenerated, and the alkaline wastewater produced can be reused after being oxidized to remove iodine, thereby reducing the discharge of alkaline wastewater.

[0028] (3) This scheme provides a method for purifying iodine ions in refined brine in an ion membrane chlor-alkali production process, which can solve the problem of salt resource waste caused by changing salt types or discharging part of the salt in traditional methods. DETAILED DESCRIPTION

[0029] In order to better illustrate the content of the present invention, a detailed description is given below in conjunction with specific embodiments.

[0030] Example 1

[0031] A method for purifying iodine ions in refined brine in an ion-exchange membrane chlor-alkali production process comprises the following steps:

[0032] Step 1: Add industrial salt and water into the salt tank and mix them to obtain a crude brine with a concentration of 300 mg / L, and analyze the Ca content in the crude brine. 2+ and Mg 2+ content;

[0033] Step 2: First, according to the Ca content in the crude brine 2+ and Mg 2+ Add slightly excess sodium carbonate and sodium hydroxide to the crude brine to adjust the pH of the crude brine to 12, then add the dust-aiding agent ferric chloride to react by stirring, let stand for 4 hours, filter to remove the salt mud, and obtain primary brine;

[0034] Step 3, adding excess sodium sulfite to the primary brine for reduction, then adding hydrochloric acid to adjust the pH of the primary brine to 7, and finally passing the primary brine into an ion exchange resin for adsorption, wherein the ion exchange resin includes D541 cationic resin and 2% anionic resin, and adjusting the flow rate of the primary brine to 0.01 m / s, and staying in the ion exchange resin for 400 s to obtain I - Refined saline with a concentration of 0.35 mg / L;

[0035] The saturated ion exchange resin is regenerated by draining - acid soaking regeneration - draining - water washing - draining - alkali regeneration - draining - acid neutralization - draining - water washing - draining - brine soaking - ion exchange resin regeneration, the generated alkaline waste liquid is treated by adding hydrogen peroxide - The iodine is removed by oxidation through steam heating to 100°C and compressed air blowing to reduce the iodine ion concentration in the alkaline wastewater to less than 0.3 mg / L for reuse.

[0036] Example 2

[0037] A method for purifying iodine ions in refined brine in an ion-exchange membrane chlor-alkali production process comprises the following steps:

[0038] Step 1: Add industrial salt and water into the salt tank and mix them to obtain a crude brine with a concentration of 300 mg / L, and analyze the Ca content in the crude brine. 2+ and Mg 2+ content;

[0039] Step 2: First, according to the Ca content in the crude brine 2+ and Mg 2+ Add slightly excess sodium carbonate and sodium hydroxide to the crude brine to adjust the pH of the crude brine to 12, then add the dust-aiding agent ferric chloride to react by stirring, let stand for 4 hours, filter to remove the salt mud, and obtain primary brine;

[0040] Step 3, adding excess sodium sulfite to the primary brine for reduction, then adding hydrochloric acid to adjust the pH of the primary brine to 7, and finally passing the primary brine into an ion exchange resin for adsorption, wherein the ion exchange resin includes D541 cationic resin and 5% anionic resin, and adjusting the flow rate of the primary brine to 0.01 m / s, and staying in the ion exchange resin for 400 s to obtain I - Refined salt water with a concentration of 0.08 mg / L;

[0041] The saturated ion exchange resin is regenerated by draining - acid soaking regeneration - draining - water washing - draining - alkali regeneration - draining - acid neutralization - draining - water washing - draining - brine soaking - ion exchange resin regeneration, the generated alkaline waste liquid is treated by adding hydrogen peroxide - The iodine is removed by oxidation through steam heating to 100°C and compressed air blowing to reduce the iodine ion concentration in the alkaline wastewater to less than 0.3 mg / L for reuse.

[0042] Example 3

[0043] A method for purifying iodine ions in refined brine in an ion-exchange membrane chlor-alkali production process comprises the following steps:

[0044] Step 1: Add industrial salt and water into the salt tank and mix them to obtain a crude brine with a concentration of 300 mg / L, and analyze the Ca content in the crude brine. 2+ and Mg 2+ content;

[0045] Step 2: First, according to the Ca content in the crude brine 2+ and Mg 2+ Add slightly excess sodium carbonate and sodium hydroxide to the crude brine to adjust the pH of the crude brine to 12, then add the dust-aiding agent ferric chloride to react by stirring, let stand for 4 hours, filter to remove the salt mud, and obtain primary brine;

[0046] Step 3, adding excess sodium sulfite to the primary brine for reduction, then adding hydrochloric acid to adjust the pH of the primary brine to 7, and finally passing the primary brine into an ion exchange resin for adsorption, wherein the ion exchange resin includes D541 cationic resin and 5% anionic resin, and adjusting the flow rate of the primary brine to 0.015 m / s, and staying in the ion exchange resin for 400 s to obtain I - Refined salt water with a concentration of 0.18 mg / L;

[0047] The saturated ion exchange resin is regenerated by draining - acid soaking regeneration - draining - water washing - draining - alkali regeneration - draining - acid neutralization - draining - water washing - draining - brine soaking - ion exchange resin regeneration, the generated alkaline waste liquid is treated by adding hydrogen peroxide - The iodine is removed by oxidation through steam heating to 100°C and compressed air blowing to reduce the iodine ion concentration in the alkaline wastewater to less than 0.3 mg / L for reuse.

[0048] Example 4

[0049] A method for purifying iodine ions in refined brine in an ion-exchange membrane chlor-alkali production process comprises the following steps:

[0050] Step 1: Add industrial salt and water into the salt tank and mix them to obtain a crude brine with a concentration of 300 mg / L, and analyze the Ca content in the crude brine. 2+ and Mg 2+ content;

[0051] Step 2: First, according to the Ca content in the crude brine 2+ and Mg 2+ Add slightly excess sodium carbonate and sodium hydroxide to the crude brine to adjust the pH of the crude brine to 12, then add the dust-aiding agent ferric chloride to react by stirring, let stand for 4 hours, filter to remove the salt mud, and obtain primary brine;

[0052] Step 3, adding excess sodium sulfite to the primary brine for reduction, then adding hydrochloric acid to adjust the pH of the primary brine to 7, and finally passing the primary brine into an ion exchange resin for adsorption, wherein the ion exchange resin includes D541 cationic resin and 5% anionic resin, and adjusting the flow rate of the primary brine to 0.008 m / s, and staying in the ion exchange resin for 400 s to obtain I - Refined saline with a concentration of 0.15 mg / L;

[0053] The saturated ion exchange resin is regenerated by draining - acid soaking regeneration - draining - water washing - draining - alkali regeneration - draining - acid neutralization - draining - water washing - draining - brine soaking - ion exchange resin regeneration, the generated alkaline waste liquid is treated by adding hydrogen peroxide - The iodine is removed by oxidation through steam heating to 100°C and compressed air blowing to reduce the iodine ion concentration in the alkaline wastewater to less than 0.3 mg / L for reuse.

[0054] Example 5

[0055] A method for purifying iodine ions in refined brine in an ion-exchange membrane chlor-alkali production process comprises the following steps:

[0056] Step 1: Add industrial salt and water into the salt tank and mix them to obtain a crude brine with a concentration of 300 mg / L, and analyze the Ca content in the crude brine. 2+ and Mg 2+ content;

[0057] Step 2: First, according to the Ca content in the crude brine 2+ and Mg 2+ Add slightly excess sodium carbonate and sodium hydroxide to the crude brine to adjust the pH of the crude brine to 12, then add the dust-aiding agent ferric chloride to react by stirring, let stand for 4 hours, filter to remove the salt mud, and obtain primary brine;

[0058] Step 3, adding excess sodium sulfite to the primary brine for reduction, then adding hydrochloric acid to adjust the pH of the primary brine to 7, and finally passing the primary brine into an ion exchange resin for adsorption, wherein the ion exchange resin includes D541 cationic resin and 7% anionic resin, and adjusting the flow rate of the primary brine to 0.008 m / s, and staying in the ion exchange resin for 400 s to obtain I - Refined salt water with a concentration of 0.23 mg / L;

[0059] The saturated ion exchange resin is regenerated by draining - acid soaking regeneration - draining - water washing - draining - alkali regeneration - draining - acid neutralization - draining - water washing - draining - brine soaking - ion exchange resin regeneration, the generated alkaline waste liquid is treated by adding hydrogen peroxide -The iodine is removed by oxidation through steam heating to 100°C and compressed air blowing to reduce the iodine ion concentration in the alkaline wastewater to less than 0.3 mg / L for reuse.

[0060] Comparative Example 1 A method for purifying iodine ions in refined brine in an ion-exchange membrane chlor-alkali production process comprises the following steps: Step 1: Add industrial salt and water into the salt tank and mix them to obtain a crude brine with a concentration of 300 mg / L, and analyze the Ca content in the crude brine. 2+ and Mg 2+ content; Step 2: First, according to the Ca content in the crude brine 2+ and Mg 2+ Add slightly excess sodium carbonate and sodium hydroxide to the crude brine to adjust the pH of the crude brine to 12, then add the dust-aiding agent ferric chloride to react by stirring, let stand for 4 hours, filter to remove the salt mud, and obtain primary brine; Step 3, adding excess sodium sulfite to the primary brine for reduction, then adding hydrochloric acid to adjust the pH of the primary brine to 7, and finally passing the primary brine into an ion exchange resin for adsorption, wherein the ion exchange resin is D541 cationic resin, and the flow rate of the primary brine is regulated to 0.01 m / s, and the brine stays in the ion exchange resin for 400 s to obtain I - Refined salt water with a concentration of 0.9 mg / L; The saturated ion exchange resin is regenerated by draining - acid soaking regeneration - draining - water washing - draining - alkali regeneration - draining - acid neutralization - draining - water washing - draining - brine soaking - ion exchange resin regeneration, the generated alkaline waste liquid is treated by adding hydrogen peroxide - The iodine is removed by oxidation through steam heating to 100°C and compressed air blowing to reduce the iodine ion concentration in the alkaline wastewater to less than 0.3 mg / L for reuse.

[0066] By comparing Example 1 with Comparative Example 1, if no anion exchange resin is added, the iodide ion in the brine is still 0.9 mg / L, and the optimal amount of anion exchange resin added is 5%, the flow rate of the primary brine is 0.1 m / s, and the residence time is 400 s.

[0067] The method for purifying iodine ions in refined brine in the ion membrane chlor-alkali production process provided by the present invention can effectively purify iodine ions, thereby avoiding damage to the ion membrane during the electrolysis process and increasing the service life of the ion membrane. In addition, the alkaline wastewater generated during the regeneration of the ion exchange resin does not need to be directly discharged, and the iodine ions in the alkaline wastewater can be removed by an oxidant and blowing, and the alkaline wastewater after iodine removal can repeat the regeneration process of the ion exchange resin.

[0068] The method for purifying iodine ions in refined brine in the ion membrane chlor-alkali production process provided by the present invention has low requirements on the quality of raw salt, is beneficial to the stability during the electrolysis process, and does not require the discharge of alkaline wastewater, thereby fundamentally solving the problem of salt resource waste.

[0069] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for purifying iodine ions from refined brine in an ion-exchange membrane chlor-alkali production process, characterized in that: The following steps are involved: S1. Dissolving industrial salt in water to obtain crude brine; S2, adding sodium carbonate and sodium hydroxide to the crude brine, then adding ferric chloride, stirring, standing, and filtering to obtain primary brine; S3, first adding sodium sulfite to the primary brine for reduction, then adding hydrochloric acid solution, and finally passing the primary brine into an ion exchange resin for adsorption, wherein the ion exchange resin includes D541 cationic resin and anionic resin; The regeneration process of the ion exchange resin is as follows: draining - acid soaking regeneration - draining - water washing - draining - alkali regeneration - draining - acid neutralization - draining - water washing - draining - salt water soaking - completion.

2. The method for purifying iodine ions from refined brine in an ion-exchange membrane chlor-alkali production process according to claim 1, characterized in that: The content of anion resin in the ion exchange resin is 2-7%.

3. The method for purifying iodine ions from refined brine in an ion-exchange membrane chlor-alkali production process according to claim 1, characterized in that: The flow rate of the primary brine is 0.008-0.015 m / s, and the residence time is 270-500 s.

4. The method for purifying iodine ions from refined brine in an ion-exchange membrane chlor-alkali production process according to claim 1, characterized in that: The post-treatment process of the alkaline wastewater generated during the regeneration of the ion exchange resin is as follows: adding an oxidant to the alkaline wastewater for oxidation, heating it to 100° C. by steam, and then blowing off iodine by compressed air to make the iodine in the alkaline wastewater less than 0.3 mg / L for reuse.

5. The method for purifying iodine ions from refined brine in an ion-exchange membrane chlor-alkali production process according to claim 4, characterized in that: The oxidant is selected from sodium hypochlorite or hydrogen peroxide.

6. The method for purifying iodine ions from refined brine in an ion-exchange membrane chlor-alkali production process according to claim 1, characterized in that: The concentration of the crude brine is 250-350 mg / L.

7. The method for purifying iodine ions from refined brine in an ion-exchange membrane chlor-alkali production process according to claim 1, characterized in that: Sodium bicarbonate and sodium hydroxide are added to the crude brine to adjust the pH of the crude brine to 12-13.

8. The method for purifying iodine ions from refined brine in an ion-exchange membrane chlor-alkali production process according to claim 1, characterized in that: The standing time is 4 to 8 hours.

9. The method for purifying iodine ions from refined brine in an ion-exchange membrane chlor-alkali production process according to claim 1, characterized in that: A hydrochloric acid solution is added to the first brine to adjust the pH of the first brine to 8-9.