CN113830740A

CN113830740A - A method for preparing acid and alkali by bipolar membrane based on electrodialysis technology

Info

Publication number: CN113830740A
Application number: CN202111180011.9A
Authority: CN
Inventors: 王大新; 施小林; 杨鹏
Original assignee: Zhejiang Zhicheng Environmental Resources Technology Co ltd
Current assignee: Hangzhou Jiangrongdao Environmental Technology Co ltd
Priority date: 2021-10-11
Filing date: 2021-10-11
Publication date: 2021-12-24
Anticipated expiration: 2041-10-11
Also published as: CN113830740B

Abstract

The invention relates to a method for preparing acid and alkali by a bipolar membrane based on electrodialysis technology, which belongs to the technical field of ion exchange membranes. In the present invention, pure water is injected into the hydrochloric acid concentrated solution tank and the sodium hydroxide concentrated solution tank, respectively, and an initial 5% concentration sodium bicarbonate solution is respectively configured in the sodium bicarbonate desalination solution tank and the bicarbonate concentrated solution tank, and the lifting pump is used to remove the sodium bicarbonate solution. The high-concentration sodium chloride desalination liquid tank is injected into the high-concentration sodium chloride desalination liquid tank through the security filter. The bipolar membrane electrodialysis adopts a five-channel module with a special structure. membrane assembled. The method uses high-content sodium chloride concentrated water and sodium bicarbonate as raw materials, realizes the resource utilization of salt, and avoids divalent cations entering the alkali chamber to form scaling and fouling during bipolar membrane alkali production. Valence-selective negative membrane to improve the purity of hydrochloric acid.

Description

Method for preparing acid and base by bipolar membrane based on electrodialysis technology

Technical Field

The invention relates to a method, in particular to a bipolar membrane acid-base preparation method based on an electrodialysis technology, and aims to avoid scaling, fouling and blockage caused by divalent cations entering an alkali chamber during alkali preparation by using a bipolar membrane, and reduce maintenance cost, and belongs to the technical field of ion exchange membranes.

Background

The ion exchange membrane is a "heart" of an electromembrane process, and is generally composed of a membrane-like material composed of a skeleton-like organic high-molecular polymer or inorganic high-molecular polymer and fixed ionic groups attached to the skeleton. When the ionic group is an anion, the cation can be combined with the anion group in the anion group to enter the membrane, under the action of a direct current electric field, the cation can migrate in the membrane along the direction of the electric field to the cathode direction and further reach the other side of the membrane, while the anion cannot enter and pass through the membrane due to the principle of same electric repulsion, in short, only the cation is allowed to pass through, so the membrane is called a cation exchange membrane, and in contrast, when the ionic group is a cation, only the anion is allowed to pass through, so the membrane is called an anion exchange membrane.

The bipolar membrane is formed by a same ion exchange membrane, wherein one side of the membrane is provided with fixed anion groups (called a cation exchange layer), and the other side of the membrane is provided with fixed cation groups (called an anion exchange layer), and the structure of the bipolar membrane endows the membrane with special properties. On the one hand, neither anions nor cations can pass through the membrane, and on the other hand, it dissociates water molecules into H⁺And OH^-And respectively migrate out of the cation exchange layer and the anion exchange layer under the action of a direct current electric field, and the membrane is called a bipolar membrane.

The ion exchange membrane is discovered from 1890 to have more than 100 years of development history, a plurality of varieties have been developed at home and abroad, and the ion exchange membrane is widely applied to the aspects of chemical production, comprehensive utilization of seawater, desalination and the like, particularly the industrialization of bipolar membranes in the eighties of the last century, so that the application field of the ion exchange membrane is greatly widened, the application economy, rationality and comprehensiveness of the ion exchange membrane are realized to realize breakthrough development, and the application of the ion exchange membrane brings revolutionary changes to a plurality of fields of chemical product production, wastewater treatment of chemical and metallurgical industries, biochemistry, organic electrochemistry, industrial waste gas and the like; the application of the method changes the industrial structure of basic chemical raw materials; the application of the method can make the cyclic utilization of acid and alkali in industries which use a large amount of acid and alkali possible; the application of the method plays a unique key role in the progress of chemical and metallurgical clean production technology, and when the enterprise thoroughly treats the sewage and the waste gas, the method not only can not increase the burden of the enterprise, but also can reduce the production cost of the product, improve the product quality, bring higher economic benefit to the enterprise, and ensure that the enterprise really achieves zero emission. In a word, the application of the bipolar membrane has great and profound strategic significance for saving energy, reducing emission, developing circular economy, saving resources, improving the utilization rate of resources and solving the contradiction between environmental protection and economy development.

The preparation method of caustic soda (sodium hydroxide) includes two methods: causticizing and electrolysis. The modern industry produces caustic soda mainly by electrolysis of saturated NaCl solutions. The electrolytic method is divided into a mercury method, a diaphragm method and an ion membrane method, wherein the diaphragm method and the ion membrane method are mainly adopted in China at present, the two methods are mainly different in that the evaporation process of alkali preparation by the diaphragm method is more complicated than the ion membrane method, and the ion membrane method is added with light brine dechlorination and brine secondary refining processes. At present, the production of caustic soda in China mainly adopts an ion membrane electrolysis method to produce caustic soda, and a caustic soda preparation method can be divided into seven processes such as rectification, brine refining, brine electrolysis, liquid caustic soda evaporation, chlorine-hydrogen treatment, solid caustic soda production and waste gas absorption.

A bipolar membrane electrodialysis method features that its bipolar membrane is a new composite ion exchange membrane composed of cation exchange layer, anion exchange layer and hydrophilic interface layer, when voltage is applied to it, the charged ions can migrate from the transition region of two ion exchange layers to the main solutions at both sides, the interface layers of anion and cation membranes form high potential gradient due to ion exhaustion, and the water molecules dissociate to generate H⁺And OH^-. Compared with the traditional ionic membrane electrolysis, the method has the advantages of low operation energy consumption, low equipment investment and capability of directly preparing acid and alkali. But during the alkali making process, divalent cations such as Ca can enter the alkali chamber²⁺、Mg²⁺Will react with OH^-Binding to form Ca (OH)₂And Mg (OH)₂Precipitation, scaling and fouling of the membrane pile.

Disclosure of Invention

The invention aims to overcome the defects in the prior art, and provides the method for preparing the acid and the alkali by using the bipolar membrane based on the electrodialysis technology, which has reasonable structural design, realizes the resource utilization of salt, avoids scale formation and fouling blockage caused by the fact that divalent cations enter an alkali chamber during the preparation of the alkali by using the bipolar membrane, selects a divalent selective anion membrane and improves the purity of hydrochloric acid (HCl).

The technical scheme adopted by the invention for solving the problems is as follows: the method for preparing acid and alkali by using the bipolar membrane based on the electrodialysis technology is characterized by comprising the following steps: the method comprises the following specific steps: respectively injecting pure water into hydrochloric acid (HCl) concentrated solution tank and sodium hydroxide (NaOH) concentrated solution tank, and adding sodium bicarbonate (NaHCO)₃) The desalting solution tank and the bicarbonate concentrate tank are respectively provided with initial 5% concentration sodium bicarbonate (NaHCO)₃) The solution is filled with concentrated sodium chloride (NaCl) -containing water through a lift pump and a cartridge filter to a high-concentration sodium chloride (NaCl) desalting solution tank, the bipolar membrane electrodialysis adopts a five-channel module with a special structure and is formed by assembling a bipolar membrane, a divalent selective negative membrane and a standard positive membrane, and 5% concentration sodium bicarbonate (NaHCO) is added into a C channel of a bipolar membrane electrodialysis unit while the concentrated sodium chloride (NaCl) -containing water enters a C channel of the bipolar membrane electrodialysis unit₃) The solution enters from the bipolar membrane electrodialysis unit D, E channel respectively, after the power supply is turned on, five channels of the bipolar membrane electrodialysis form two desalted liquid channels C and D and three concentrated liquid channels A, B and E respectively, and the solution is circulated in the electrodialysis unit all the time through the circulating pump; the salt content of the concentrated water with high sodium chloride (NaCl) content in the channel C is continuously reduced, and the concentrated water overflows from the water tank to a next-stage treatment unit for treatment after reaching a set target value; 5% strength sodium bicarbonate (NaHCO) in D channel₃) The concentration of the solution also continuously decreases, and after the concentration of the solution reaches a set target value, the solution overflows from the water tank to return to sodium bicarbonate (NaHCO)₃) A box filled with sodium bicarbonate (NaHCO)₃) The box is pumped through a lift pump and filtered through a cartridge filter to sodium bicarbonate (NaHCO)₃) The desalting solution tank is supplied with high-concentration sodium bicarbonate (NaHCO)₃) A solution; three concentrates were formed in A, B and E channels, respectively, wherein the A channel is formed by Cl in the C channel^-With H dissociated from channel A⁺The combined hydrochloric acid (HCl) chamber is concentrated to 8 percent concentration and overflows to the next stage of treatment from a hydrochloric acid (HCl) concentrated solution tank(ii) a Wherein the B channel is formed by Na in the D channel⁺With OH dissociated from the B channel^-The combined sodium hydroxide (NaOH) chamber is concentrated to 8 percent concentration and overflows to the next stage of treatment by a sodium hydroxide (NaOH) concentrated solution tank; wherein the E channel is formed by Na in the C channel⁺With HCO in the D channel₃ ^-Combined sodium bicarbonate (NaHCO)₃) The chamber, worth mentioning, may also contain a certain amount of Ca in the concentrated water containing high sodium chloride (NaCl)²⁺、Mg²⁺Thus, Ca is also present in the C channel²⁺、Mg²⁺Then the E channel is composed of Na in the C channel⁺、Ca²⁺、Mg²⁺With HCO in the D channel₃ ^-Combined sodium bicarbonate (NaHCO)₃) Calcium bicarbonate (Ca (HCO)₃)₂) And magnesium bicarbonate (Mg (HCO)₃)₂) A bicarbonate chamber of (a); concentrating to 10% concentration, overflowing from bicarbonate concentrate tank, adjusting pH to 9 with sodium hydroxide (NaOH), heating for decomposition, and adding sodium bicarbonate (NaHCO)₃) Calcium bicarbonate (Ca (HCO)₃)₂) And magnesium bicarbonate (Mg (HCO)₃)₂) Decomposed into sodium carbonate (Na)₂CO₃) Calcium carbonate (CaCO)₃) And magnesium carbonate (MgCO)₃) Flows into a settling tank, and the sediment in the settling tank is calcium carbonate (CaCO)₃) And magnesium carbonate (MgCO)₃) The supernatant is sodium carbonate (Na)₂CO₃) Solution, introduction of CO₂Conversion to sodium bicarbonate (NaHCO)₃) Overflow to sodium bicarbonate (NaHCO)₃) And (7) a box.

Preferably, five solutions in the five-channel module of the bipolar membrane electrodialysis are respectively separated by ion exchange membranes and are not in contact with each other; under the action of an external direct current electric field, the five-channel electrodialysis prepares high-purity hydrochloric acid and sodium hydroxide solution.

Preferably, the invention adopts a divalent selective negative film to remove sulfate radical (SO) in concentrated water containing high content of sodium chloride (NaCl)₄ ^2-) And (5) intercepting and improving the purity of hydrochloric acid (HCl).

Preferably, the present invention is directed to the treatment of high sodium sulfate (Na) content₂SO₄) When concentrating waterThe sulfuric acid (H) can be obtained by replacing a divalent selective cathode membrane with a common cathode membrane₂SO₄) With sodium hydroxide (NaOH) solution.

Compared with the prior art, the invention has the following advantages and effects: using concentrated water with high content of sodium chloride (NaCl) and sodium bicarbonate (NaHCO)₃) As a raw material, the method realizes resource utilization of salt, avoids scale formation and fouling caused by divalent cations entering an alkali chamber during the preparation of alkali by using the bipolar membrane, and improves the purity of hydrochloric acid (HCl) by selecting a divalent selective negative membrane.

Drawings

FIG. 1 is a simplified flow chart of acid and alkali preparation by a bipolar membrane based on an electrodialysis technology in an embodiment of the invention.

FIG. 2 is a schematic diagram of acid-base preparation according to an embodiment of the present invention.

FIG. 3 is a schematic diagram of a system for preparing acid and base according to an embodiment of the present invention.

Labeling and ranking in the figure: a: a divalent selective anion exchange membrane; c: a cation exchange membrane; cl^-: chloride ions; ca²⁺: calcium ions; HCO₃ ^-: a bicarbonate ion; na (Na)⁺: sodium ions; BM: bipolar membrane; mg (magnesium)²⁺: magnesium ions; h⁺: hydrogen ions; OH group^-: hydroxyl ions; CO 2₂: carbon dioxide.

Detailed Description

The present invention will be described in further detail below by way of examples with reference to the accompanying drawings, which are illustrative of the present invention and are not to be construed as limiting the present invention.

Examples are given.

Referring to fig. 1 to 3, the specific steps of preparing acid and base by using the bipolar membrane based on the electrodialysis technology in the embodiment are as follows: respectively injecting pure water into hydrochloric acid (HCl) concentrated solution tank and sodium hydroxide (NaOH) concentrated solution tank, and adding sodium bicarbonate (NaHCO)₃) The desalting solution tank and the bicarbonate concentrate tank are respectively provided with initial 5% concentration sodium bicarbonate (NaHCO)₃) The solution is pumped by a lift pump and then is injected into a high-concentration sodium chloride (NaCl) desalting solution tank through a cartridge filter, and the bipolar membrane electrodialysis adopts a special knotThe five-channel module is assembled by a bipolar membrane, a divalent selective negative membrane and a standard positive membrane, and sodium bicarbonate (NaHCO) with the concentration of 5 percent enters a C channel of the bipolar membrane electrodialysis unit while concentrated water with high sodium chloride (NaCl) enters the C channel₃) The solution enters from the bipolar membrane electrodialysis unit D, E channel respectively, after the power supply is turned on, five channels of the bipolar membrane electrodialysis form two desalted liquid channels C and D and three concentrated liquid channels A, B and E respectively, and the solution is circulated in the electrodialysis unit all the time through the circulating pump; the salt content of the concentrated water with high sodium chloride (NaCl) content in the channel C is continuously reduced, and the concentrated water overflows from the water tank to a next-stage treatment unit for treatment after reaching a set target value; 5% strength sodium bicarbonate (NaHCO) in D channel₃) The concentration of the solution also continuously decreases, and after the concentration of the solution reaches a set target value, the solution overflows from the water tank to return to sodium bicarbonate (NaHCO)₃) A box filled with sodium bicarbonate (NaHCO)₃) The box is pumped through a lift pump and filtered through a cartridge filter to sodium bicarbonate (NaHCO)₃) The desalting solution tank is supplied with high-concentration sodium bicarbonate (NaHCO)₃) A solution; three concentrates were formed in A, B and E channels, respectively, wherein the A channel is formed by Cl in the C channel^-With H dissociated from channel A⁺The combined hydrochloric acid (HCl) chamber is concentrated to 8 percent of concentration and overflows to the next stage of treatment from a hydrochloric acid (HCl) concentrated solution tank; wherein the B channel is formed by Na in the D channel⁺With OH dissociated from the B channel^-The combined sodium hydroxide (NaOH) chamber is concentrated to 8 percent concentration and overflows to the next stage of treatment by a sodium hydroxide (NaOH) concentrated solution tank; wherein the E channel is formed by Na in the C channel⁺With HCO in the D channel₃ ^-Combined sodium bicarbonate (NaHCO)₃) The chamber, worth mentioning, may also contain a certain amount of Ca in the concentrated water containing high sodium chloride (NaCl)²⁺、Mg²⁺Thus, Ca is also present in the C channel²⁺、Mg²⁺Then the E channel is composed of Na in the C channel⁺、Ca²⁺、Mg²⁺With HCO in the D channel₃ ^-Combined sodium bicarbonate (NaHCO)₃) Calcium bicarbonate (Ca (HCO)₃)₂) And magnesium bicarbonate (Mg (HCO)₃)₂) A bicarbonate chamber of (a); concentrating to 10% concentration, concentrating with bicarbonateOverflowing the liquid-extracting tank, adjusting pH to 9 with sodium hydroxide (NaOH), heating for decomposition, and adding sodium bicarbonate (NaHCO)₃) Calcium bicarbonate (Ca (HCO)₃)₂) And magnesium bicarbonate (Mg (HCO)₃)₂) Decomposed into sodium carbonate (Na)₂CO₃) Calcium carbonate (CaCO)₃) And magnesium carbonate (MgCO)₃) Flows into a settling tank, and the sediment in the settling tank is calcium carbonate (CaCO)₃) And magnesium carbonate (MgCO)₃) The supernatant is sodium carbonate (Na)₂CO₃) Solution, introduction of CO₂Conversion to sodium bicarbonate (NaHCO)₃) Overflow to sodium bicarbonate (NaHCO)₃) And (7) a box.

The main creation points of the embodiment are as follows: adopting a specially-structured five-channel bipolar membrane electrodialysis module to remove Cl in concentrated water containing high sodium chloride (NaCl)^-Dissociation from the bipolar membrane to give H⁺To produce hydrochloric acid (HCl) of 8% concentration; sodium bicarbonate (NaHCO)₃) Na in solution⁺Dissociation of OH from bipolar membrane^-Recombining to prepare sodium hydroxide (NaOH) with the concentration of 8%; na in concentrated water containing high content of sodium chloride (NaCl)⁺、Ca²⁺、Mg²⁺With sodium bicarbonate (NaHCO)₃) HCO in solution₃ ^-Recombination was carried out to give sodium bicarbonate (NaHCO) at 10% concentration₃) Calcium bicarbonate (Ca (HCO)₃)₂) And magnesium bicarbonate (Mg (HCO)₃)₂) Adding sodium hydroxide (NaOH) to adjust the pH value to 9, heating and decomposing to obtain calcium bicarbonate (Ca (HCO)) in the solution₃)₂) And magnesium bicarbonate (Mg (HCO)₃)₂) Conversion to calcium carbonate (CaCO)₃) And magnesium carbonate (MgCO)₃) Precipitate and eliminate Ca²⁺、Mg²⁺Sodium bicarbonate (NaHCO) entering the caustic chamber causing fouling₃) Is converted into sodium carbonate (Na) by thermal decomposition₂CO₃) Then introducing CO₂Sodium carbonate (Na)₂CO₃) Conversion to sodium bicarbonate (NaHCO)₃) As sodium bicarbonate (NaHCO)₃) And (4) a supply solution of a desalting solution tank. It is worth mentioning that a divalent selective negative film can be usedSulfate radical (SO) in concentrated water with high content of sodium chloride (NaCl)₄ ^2-) And (5) intercepting and improving the purity of hydrochloric acid (HCl).

Five solutions in the channel of the embodiment are respectively separated by the ion exchange membrane and are not mutually contacted. Under the action of an external direct current electric field, the five-channel electrodialysis prepares high-purity hydrochloric acid and sodium hydroxide solution.

This example uses a divalent selective negative film to increase the purity of hydrochloric acid.

Sodium bicarbonate (NaHCO) at 10% concentration as obtained in this example₃) Calcium bicarbonate (Ca (HCO)₃)₂) And magnesium bicarbonate (Mg (HCO)₃)₂) Adding sodium hydroxide (NaOH) to adjust the pH value to 9, heating and decomposing to obtain calcium bicarbonate (Ca (HCO)) in the solution₃)₂) And magnesium bicarbonate (Mg (HCO)₃)₂) Conversion to calcium carbonate (CaCO)₃) And magnesium carbonate (MgCO)₃) Precipitate and eliminate Ca²⁺、Mg²⁺Sodium bicarbonate (NaHCO) entering the caustic chamber causing fouling₃) Is converted into sodium carbonate (Na) by thermal decomposition₂CO₃) Then introducing CO₂Sodium carbonate (Na)₂CO₃) Conversion to sodium bicarbonate (NaHCO)₃) As sodium bicarbonate (NaHCO)₃) And (4) a supply solution of a desalting solution tank.

This example is for the treatment of high sodium sulfate (Na) content₂SO₄) When concentrating, the second-valence selective cathode membrane is replaced by common cathode membrane to obtain sulfuric acid (H)₂SO₄) With sodium hydroxide (NaOH) solution.

And will be apparent to those skilled in the art from the foregoing description.

In addition, it should be noted that the specific embodiments described in the present specification may be different in the components, the shapes of the components, the names of the components, and the like, and the above description is only an illustration of the structure of the present invention. Equivalent or simple changes in the structure, characteristics and principles of the invention are included in the protection scope of the patent. Various modifications, additions and substitutions for the specific embodiments described may be made by those skilled in the art without departing from the scope of the invention as defined in the accompanying claims.

Claims

1. A method for preparing acid and alkali by using a bipolar membrane based on an electrodialysis technology is characterized by comprising the following steps: the method comprises the following specific steps: pure water is respectively injected into a hydrochloric acid concentrated solution tank and a sodium hydroxide concentrated solution tank, initial 5% concentration sodium bicarbonate solution is respectively configured in a sodium bicarbonate desalting solution tank and a bicarbonate concentrated solution tank, concentrated water with high sodium chloride is injected into a high-concentration sodium chloride desalting solution tank through a cartridge filter by a lift pump, bipolar membrane electrodialysis adopts a five-channel module with a special structure and is assembled by a bipolar membrane, a second-order selective negative membrane and a standard positive membrane, the 5% concentration sodium bicarbonate solution respectively enters from a bipolar membrane electrodialysis unit D, E channel while the concentrated water with high sodium chloride enters a bipolar membrane electrodialysis unit C channel, after a power supply is turned on, the five channels of the bipolar membrane electrodialysis respectively form two desalting solution channels C and D, three concentrated solution channels A, B and E, and the two desalting solution channels C and D and the three concentrated solution channels A, B and E are always circulated in the electrodialysis unit through a circulating pump; the salt content of the high-sodium chloride-content concentrated water in the channel C is continuously reduced, and the high-sodium chloride-content concentrated water overflows from the water tank to a next-stage treatment unit for treatment after reaching a set target value; the concentration of the 5% sodium bicarbonate solution in the channel D is also continuously reduced, the sodium bicarbonate solution overflows from the water tank to the sodium bicarbonate tank after reaching a set target value, and then the high-concentration sodium bicarbonate solution is supplied to the sodium bicarbonate desalting solution tank through the sodium bicarbonate tank, the lift pump and the security filter; three concentrates were formed in A, B and E channels, respectively, wherein the A channel is formed by Cl in the C channel^-With H dissociated from channel A⁺Combined into a hydrochloric acid chamber, and concentrated to 8 percent concentration and then overflows to the next stage of treatment from a hydrochloric acid concentrated solution tank; wherein the B channel is formed by Na in the D channel⁺With OH dissociated from the B channel^-The combined sodium hydroxide chamber is concentrated to 8 percent concentration and overflows to the next stage of treatment by a sodium hydroxide concentrated solution tank; wherein the E channel is formed by Na in the C channel⁺、Ca²⁺、Mg²⁺With HCO in the D channel₃ ^-A bicarbonate chamber of combined sodium bicarbonate, calcium bicarbonate and magnesium bicarbonate; concentrating to 10% concentration, overflowing from bicarbonate concentrate tank, adjusting pH to 9 with sodium hydroxide, heating for decomposition, decomposing sodium bicarbonate, calcium bicarbonate and magnesium bicarbonate into sodium carbonate, calcium carbonate and magnesium carbonate, allowing the precipitate in the precipitation tank to be calcium carbonate and magnesium carbonate, allowing the supernatant to be sodium carbonate solution, introducing CO₂The sodium bicarbonate is turned into sodium bicarbonate and overflows to a sodium bicarbonate tank.

2. The bipolar membrane based on electrodialysis technology of claim 1, wherein: five solutions in the five-channel module of the bipolar membrane electrodialysis are respectively separated by ion exchange membranes and are not mutually contacted; under the action of an external direct current electric field, the five-channel electrodialysis prepares high-purity hydrochloric acid and sodium hydroxide solution.

3. The bipolar membrane based on electrodialysis technology of claim 1, wherein: a divalent selective negative film is adopted to intercept sulfate radicals in the concentrated water containing high-concentration sodium chloride, so that the purity of the hydrochloric acid is improved.

4. The bipolar membrane based on electrodialysis technology of claim 1, wherein: when the concentrated water with high content of sodium sulfate is treated, a divalent selective negative film is replaced by a common negative film, and the sulfuric acid and sodium hydroxide solution can be prepared.