Electrically-driven membrane device and method for seawater carbon capture and mineralization

Abstract

The invention discloses an electrically-driven membrane device and method for seawater carbon capture and mineralization. The electrically-driven membrane device comprises an acid gas introduction pipeline, an alkali liquor storage unit, a saline water storage unit, an acid liquor storage unit, a polar liquor storage unit and an electrically-driven membrane device electrodialysis membrane stack, the electrically driven membrane device and method for seawater carbon capture and mineralization comprises the following steps: respectively and independently adjusting the pH values of alkali liquor and saline water; the alkali liquor, the saline water, the acid liquor and the polar liquor are independently and circularly operated, and seed crystals are added into the settling chamber. The electrically-driven membrane device provided by the invention is simple in method, Ca < 2 + > in seawater is removed outside the membrane stack of the electrically-driven membrane device, the risk of membrane pollution is effectively reduced, the decalcification rate is greater than or equal to 80%, the carbon sequestration rate is greater than or equal to 30%, and the desulfurization rate is greater than or equal to 98%.

Description

Technical Field

[0001] This disclosure generally relates to seawater decalcification and carbon fixation, and specifically to an electrically driven membrane device and method for seawater carbon capture and mineralization. Background Technology

[0002] Seawater contains various hard ions, such as Ca2+. 2+ Mg 2+ and SO4 2- etc., of which C a 2+ The concentration is approximately 0.4 g / L. Due to Ca... 2+ With SO4 2- The solubility product constant of the formed calcium sulfate is very small, only 7.1 × 10⁻⁶. -7 Furthermore, its solubility increases with temperature; therefore, at high seawater concentration ratios, Ca... 2+ With SO4 2- It easily crystallizes and precipitates as calcium sulfate, forming calcium scale that is difficult to clean and causing some pollution.

[0003] In distillation-based seawater desalination, calcium scale deposits on the heat transfer interface, reducing heat transfer efficiency. In membrane-based seawater desalination, calcium scale deposits on the membrane surface, severely affecting membrane lifespan and desalination efficiency. To prevent calcium scale formation, existing seawater desalination technologies typically employ low water recovery rates, generally not exceeding 50%, while distillation-based seawater desalination achieves rates even lower than 40%.

[0004] Therefore, developing an effective method for seawater decalcification, which removes most calcium ions through pretreatment before seawater desalination, is of great significance for improving the efficiency of the seawater desalination process, increasing water recovery rate, reducing desalination costs, and promoting the development of the seawater desalination industry. The purpose of this invention is to provide an electro-driven membrane device and method for seawater decalcification. The electro-driven membrane stack used in this device does not contain a cation exchange membrane, thus avoiding contact between calcium and magnesium ions in seawater and the electro-driven membrane. (The last sentence appears to be incomplete and possibly refers to the removal of calcium ions from the membrane.) 2+ Precipitation in the settling chamber as calcium carbonate, rather than precipitation in the electro-driven membrane stack, reduces the risk of membrane fouling and improves the efficiency of the electro-driven membrane; this method can not only remove Ca from seawater 2+ It can also achieve the function of carbon fixation and has good prospects for industrial application. Summary of the Invention

[0005] In view of the above-mentioned defects or deficiencies in the prior art, it is desirable to provide an electrically driven membrane device and method for seawater carbon capture and mineralization.

[0006] In a first aspect, the present invention provides an electrically driven membrane device for seawater decalcification, the device comprising an acid gas inlet pipe, an alkaline solution storage unit, a brine storage unit, an acid solution storage unit, an electrode solution storage unit, and an electrically driven membrane stack.

[0007] The alkali outlet of the alkali storage unit is connected to the alkali chamber inlet of the electrically driven membrane stack, and the alkali chamber outlet of the electrically driven membrane stack is connected to the alkali inlet of the alkali storage unit, forming a circulation loop for the alkali.

[0008] The brine storage unit is divided into a brine chamber and a settling chamber by a partition. The brine outlet of the brine chamber is connected to the brine chamber inlet of the electrically driven membrane stack, while the brine chamber outlet of the electrically driven membrane stack is connected to the brine inlet of the settling chamber. After sedimentation, the brine in the settling chamber overflows back into the brine chamber.

[0009] The acid gas inlet pipes are connected to the alkali storage unit and the brine chamber respectively, so as to introduce acid gas into both.

[0010] The acid outlet of the acid storage unit is connected to the acid chamber inlet of the electrically driven membrane stack, and the acid chamber outlet of the electrically driven membrane stack is connected to the acid inlet of the acid storage unit, forming a circulation loop for the acid.

[0011] The electrode outlet of the electrode storage unit is connected to the electrode chamber inlet of the electrically driven membrane, and the electrode chamber inlet of the electrically driven membrane is connected to the electrode inlet of the electrode storage unit, forming a circulation loop for the electrode liquid.

[0012] The electro-driven membrane stack consists of an anode, a cathode, and at least one set of three-compartment electrodialysis units located between the anode and cathode. Each set of three-compartment electrodialysis units is composed of an electro-driven membrane, an anion membrane, an anion membrane, and an electro-driven membrane arranged in sequence, and two adjacent sets of three-compartment electrodialysis units share one electro-driven membrane.

[0013] During operation, anions from the alkali solution in the alkali chamber enter the salt chamber through the anion exchange membrane and react with Ca in the salt chamber. 2+ A precipitate forms. The brine is then returned to the settling chamber, where it settles under the influence of seed crystals, resulting in calcium carbonate precipitate in the lower layer of the settling chamber. The supernatant in the settling chamber overflows back into the brine chamber, where it is recycled again. When the Ca in the brine... 2+ The electro-driven membrane process ends when the concentration no longer changes.

[0014] The apparatus of this invention provides the alkali source required for seawater decalcification via an electro-driven membrane, overcoming the high cost and heavy subsequent treatment load associated with adding white mud. Compared to methods using sodium hydroxide as the alkali source, the process cost of this invention is lower. Furthermore, since calcium ion removal occurs outside the electro-driven membrane stack, calcium ions do not come into contact with the electro-driven membrane during the entire electrodialysis process, thereby improving the service life of the electro-driven membrane.

[0015] Preferably, the alkali storage unit can be any type of container used for storing alkali, whether it is a regular or irregular container. Technicians can choose according to actual needs.

[0016] The cathode of the electro-driven membrane stack can be titanium electrodes and / or stainless steel electrodes. These materials also have good conductivity and corrosion resistance, which can meet the requirements of electro-driven membranes.

[0017] The acidic gases described in this invention include, but are not limited to, the types of gases mentioned above. When the acidic gas is flue gas, the electrically driven membrane device of this invention can not only achieve decalcification of seawater, but also effectively remove carbon dioxide and sulfur dioxide from the flue gas.

[0018] To reduce the risk of anion exchange membrane fouling and improve the service life of the electro-driven membrane stack, a filtration unit is preferably installed in the brine chamber. This ensures that the brine in the brine chamber is filtered before entering the brine chamber of the electro-driven membrane stack, removing impurities and precipitated particles.

[0019] The electrically driven membrane stack contains at least one set of three-compartment electrodialysis units, the specific number of which can be rationally selected according to the initial concentration of calcium ions in the brine. For example, different numbers of three-compartment electrodialysis units, such as 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15, can be selected to meet different decalcification requirements.

[0020] Secondly, the present invention provides a method for seawater decalcification using an electrically driven membrane device as described in the first aspect. The method includes the following steps:

[0021] (1) Adjust the pH values ​​of the alkaline solution and the salt solution independently;

[0022] (2) Start the circulation operation of alkaline solution, brine, acid solution and polar solution, and add seed crystals in the settling chamber;

[0023] (3) After the alkaline solution, brine, acid solution, and electrode solution begin circulating as described in step (2), acidic gas is introduced into the alkaline solution, and then electricity is applied to start the electro-driven membrane. When the calcium ion concentration in the brine solution remains stable, the electricity is stopped, and the electro-driven membrane operation ends.

[0024] Preferably, in step (1), the pH values ​​of the alkaline solution and the brine are adjusted to 7-9 independently using acidic gas.

[0025] Preferably, the acidic gas includes any one or a combination of at least two of carbon dioxide, sulfur dioxide, or flue gas. Typical but non-limiting combinations include combinations of carbon dioxide and sulfur dioxide, sulfur dioxide and flue gas, carbon dioxide and flue gas, or carbon dioxide, sulfur dioxide, and flue gas.

[0026] Preferably, the volume fraction of carbon dioxide in the acidic gas is 5-15%, for example, it can be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14% or 15%.

[0027] Preferably, the concentration of sulfur dioxide in the acidic gas is 500-10000 ppm, for example, it can be 500 ppm, 1000 ppm, 1500 ppm, 2000 ppm, 2500 ppm, 3000 ppm, 3500 ppm, 4000 ppm, 4500 ppm, 5000 ppm, 5500 ppm, 6000 ppm, 6500 ppm, 7000 ppm, 7500 ppm, 8000 ppm, 8500 ppm, 9000 ppm, 9500 ppm or 10000 ppm, preferably 2000-5000 ppm.

[0028] Preferably, the alkaline solution can be any one or a combination of at least two of NaOH solution, NaHCO3 solution, or Na2CO3 solution. Typical but non-limiting combinations include the combination of NaOH solution and Na2CO3 solution or the combination of NaHCO3 solution and Na2CO3.

[0029] Preferably, the brine is seawater.

[0030] Preferably, the salt water contains Ca 2+ The concentration is 0.2-0.6 mg / g, for example 0.2 mg / g, 0.3 mg / g, 0.4 mg / g, 0.5 mg / g or 0.6 mg / g.

[0031] Preferably, the acid solution can be any one or a combination of at least two of hydrochloric acid solution, nitric acid solution, or sulfuric acid solution. Typical but non-limiting combinations include combinations of hydrochloric acid solution and nitric acid solution, combinations of nitric acid solution and sulfuric acid solution, combinations of hydrochloric acid solution and sulfuric acid solution, or combinations of hydrochloric acid solution, nitric acid solution, and sulfuric acid solution.

[0032] Preferably, the pH value of the acid solution is 0-2, for example, it can be 0, 0.5, 1, 1.5 or 2.

[0033] Preferably, the polar liquid can be a sodium nitrate solution and / or a sodium chloride solution.

[0034] Preferably, the concentration of the polar liquid is 5-25 g / L, for example, it can be 5 g / L, 10 g / L, 15 g / L, 20 g / L or 25 g / L, and more preferably 10-20 g / L.

[0035] Preferably, the seed crystal in step (2) is calcium carbonate. The addition of the seed crystal can accelerate the precipitation process of calcium carbonate and improve the efficiency of decalcification of seawater.

[0036] Preferably, the amount of seed crystals added in step (2) is 0-20% of the mass of calcium ions in the brine, but not 0%, for example, it can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20%.

[0037] Preferably, the acidic gas in step (3) can be any one or a combination of at least two of carbon dioxide, sulfur dioxide, or flue gas. Typical but non-limiting combinations include combinations of carbon dioxide and sulfur dioxide, sulfur dioxide and flue gas, carbon dioxide and flue gas, or carbon dioxide, sulfur dioxide, and flue gas.

[0038] Preferably, the circulation flow rate of the alkaline solution in step (3) is 0.75-3 to the liquid-to-gas ratio of the acidic gas, for example, it can be 0.75, 1, 1.5, 2, 2.5 or 3.

[0039] Preferably, in step (3), the current density of the electrically driven membrane is 3-25 A / m. 2 For example, it could be 3A / m 2 5A / m 2 10A / m 2 15A / m 2 20A / m 2 Or 25A / m 2 Preferably 5-20A / m 2 .

[0040] Preferably, when the electro-driven membrane is used in step (3), the flow rate on the membrane surface is 0.1-2 cm / s, for example, it can be 0.1 cm / s, 0.2 cm / s, 0.3 cm / s, 0.4 cm / s, 0.5 cm / s, 0.6 cm / s, 0.7 cm / s, 0.8 cm / s, 0.9 cm / s, 1 cm / s, 1.1 cm / s, 1.2 cm / s, 1.3 cm / s, 1.4 cm / s, 1.5 cm / s, 1.6 cm / s, 1.7 cm / s, 1.8 cm / s, 1.9 cm / s or 2 cm / s, preferably 0.5-1.5 cm / s.

[0041] As a preferred embodiment of the second aspect of the present invention, an electrically driven membrane device and method for seawater carbon capture and mineralization includes the following steps:

[0042] (1) Use acidic gas to independently adjust the pH of the alkaline solution and the brine to 6-8;

[0043] (2) The alkaline solution, brine, acid solution, and polar solution are circulated independently. The Ca in the brine solution... 2+ The concentration is 0.2-0.6 mg / g, and seed crystals with a mass of 0-30% of the calcium ion mass in the brine are added in the settling chamber;

[0044] (3) After the alkaline solution, brine, acid solution, and electrode liquid mentioned in step (2) begin circulating, acidic gas is introduced into the alkaline solution. The circulation flow rate of the alkaline solution to the liquid-to-gas ratio of the acidic gas is 0.75-3. At the same time, the electro-driven membrane is started by applying electricity with a current density of 3-25 A / m. 2 The flow rate at the membrane surface is 0.1-2 cm / s. When the calcium ion concentration in the brine remains stable, the current is stopped, and the electro-driven membrane is terminated.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] (1) The electro-driven membrane stack in the electro-driven membrane device provided by the present invention is composed of a three-compartment electrodialysis unit, and each three-compartment electrodialysis unit is composed of an electro-driven membrane, an anion membrane, anion membrane, and an electro-driven membrane. This structure improves upon the traditional three-compartment structure of electro-driven membrane, anion membrane, cation membrane, and electro-driven membrane, avoiding direct contact between calcium ions in the brine and the electro-driven membrane, thereby effectively preventing membrane fouling and improving the efficiency of the electro-driven membrane.

[0047] (2) The electro-driven membrane method provided by this invention is simple and easy to implement. The removal of calcium ions from seawater takes place outside the membrane stack of the electrodialysis electro-driven membrane, effectively reducing the risk of membrane fouling. Applying the electro-driven membrane device for seawater decalcification provided by this invention for decalcification, carbon fixation, and desulfurization, the decalcification rate is ≥80%, the carbon fixation rate is ≥30%, and the desulfurization rate is ≥98%, achieving significant results. Further features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings. Attached Figure Description

[0048] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0049] Figure 1 The diagram shown is a schematic of an electrically driven membrane device for seawater carbon capture and mineralization.

[0050] The diagram is labeled as follows: 1. Alkali storage unit; 2. Brine storage unit; 3. Acid storage unit; 4. Electrolytic liquid storage unit; 5. Electro-driven membrane; 6. Anion exchange membrane; 7. Cation exchange membrane; 8. Electro-driven membrane. Detailed Implementation

[0051] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0052] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0053] Application Example 1

[0054] This application example provides a method for decalcifying seawater using an electrically driven membrane device provided in an application implementation, comprising the following steps:

[0055] (1) The pH of the sodium hydroxide solution in the alkaline storage unit 2 and the simulated seawater in the brine storage unit 3 were adjusted to 7.5 independently using acidic gas. The acidic gas was flue gas with a volume fraction of 14% carbon dioxide and 2000 ppm sulfur dioxide. The concentration of Ca2+ in the simulated seawater was 0.50 mg / g.

[0056] (2) The alkali solution in the alkali storage unit 2 after pH adjustment, the simulated seawater in the brine storage unit 3 after pH adjustment, the nitric acid solution with a pH of 1.5 in the acid storage unit 4, and the NaCl solution with a concentration of 20 g / L in the polar liquid storage unit 5 are circulated independently, and calcium carbonate seed crystals with a mass of 15% of the calcium ions in the simulated seawater are added in the settling chamber.

[0057] (3) After the liquids in the alkali storage unit 2, brine storage unit 3, acid storage unit 4, and electrode storage unit 5 begin to circulate, flue gas is continuously introduced into the alkali storage unit 2. The volume fraction of carbon dioxide in the flue gas is 12%, and the volume fraction of sulfur dioxide is 2000 ppm. The liquid-to-gas ratio of the circulating flow rate of the alkali solution to the flue gas is 2.5. At the same time, an electric current is applied to drive the membrane, with a current density of 20 A / m. 2 The flow velocity on the membrane surface is 0.5 cm / s. When the calcium ion concentration in the simulated seawater in the brine storage unit 3 remains constant, the power supply is stopped, and the electro-driven membrane is terminated.

[0058] Application Example 2

[0059] This application example provides a method for decalcifying seawater using the electro-driven membrane device for seawater decalcification provided in Example 2, comprising the following steps:

[0060] (1) The pH of the sodium hydroxide solution in the alkaline storage unit 2 and the simulated seawater in the brine storage unit 3 is adjusted to 8 independently using acidic gas. The acidic gas is flue gas with a volume fraction of 5% carbon dioxide and 500 ppm sulfur dioxide. The concentration of Ca2+ in the simulated seawater is 0.61 mg / g.

[0061] (2) The alkaline solution after pH adjustment in the alkaline solution storage unit 2, the simulated seawater after pH adjustment in the brine storage unit 3, the hydrochloric acid solution with pH value of 2 in the acid solution storage unit 4, and the sodium nitrate solution with a concentration of 25 g / L in the polar solution storage unit 5 are circulated independently, and calcium carbonate seed crystals with a mass of 20% of the calcium ions in the simulated seawater are added in the sedimentation chamber.

[0062] (3) After the liquids in the alkali storage unit 2, brine storage unit 3, acid storage unit 4, and electrode storage unit 5 begin to circulate, flue gas is continuously introduced into the alkali storage unit 2. The volume fraction of carbon dioxide in the flue gas is 5%, and the volume fraction of sulfur dioxide is 10,000 ppm. The liquid-to-gas ratio of the circulating flow rate of the alkali solution to the flue gas is 3. Simultaneously, the membrane is electrically driven with a current density of 25 A / m. 2 The flow velocity on the membrane surface is 2 cm / s. When the calcium ion concentration in the simulated seawater in the brine storage unit 3 remains unchanged, the power supply is stopped, and the electro-driven membrane is terminated.

[0063] Application Example 3

[0064] This application example provides a method for decalcifying seawater using the electro-driven membrane device for seawater decalcification provided in Example 2, comprising the following steps: (1) using acidic gas to independently adjust the pH of the sodium hydroxide solution in the alkali storage unit 2 and the simulated seawater in the brine storage unit 3 to 7, wherein the acidic gas is flue gas, the volume fraction of carbon dioxide in the flue gas is 15%, the volume fraction of sulfur dioxide is 5000ppm, and the simulated seawater contains Ca 2+The concentration is 0.22 mg / g; (2) The pH value of the alkaline solution in the alkaline solution storage unit 2 after adjustment, the pH value of the simulated seawater in the brine storage unit 3 after adjustment, the pH value of the sulfuric acid solution in the acid solution storage unit 4 with a pH value of 0, and the concentration of the sodium nitrate solution in the polar liquid storage unit 5 with a concentration of 5 g / L are circulated independently, and calcium carbonate seed crystals with a mass of 1% of the calcium ions in the simulated seawater are added in the settling chamber; (3) After the liquids in the alkaline solution storage unit 2, brine storage unit 3, acid solution storage unit 4 and polar liquid storage unit 5 begin to circulate, flue gas is continuously introduced into the alkaline solution storage unit 2. The volume fraction of carbon dioxide in the flue gas is 15%, the volume fraction of sulfur dioxide is 4000 ppm, the circulation flow rate of the alkaline solution and the liquid-gas ratio of the flue gas are 0.75, and the membrane is electrically driven at a current density of 3 A / m 2 The flow velocity on the membrane surface is 0.1 cm / s. When the calcium ion concentration in the simulated seawater in the brine storage unit 3 remains constant, the power supply is stopped, and the electro-driven membrane is terminated.

[0065] like Figure 1 As shown: The electro-driven membrane device for seawater decalcification provided by this invention achieves a decalcification rate ≥80%, a carbon fixation rate ≥30%, and a desulfurization rate ≥98% when performing decalcification, carbon fixation, and desulfurization. The applicant declares that the above description is merely a specific embodiment of this invention, but the scope of protection of this invention is not limited thereto. Those skilled in the art should understand that any variations or substitutions easily conceived by those skilled in the art within the technical scope disclosed in this invention fall within the scope of protection and disclosure of this invention.

[0066] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, technical solutions formed by substituting the above features with, but not limited to, technical features disclosed in this application that have similar functions.

Claims

1. An electrically driven membrane device and method for seawater carbon capture and mineralization, characterized in that, The electro-driven membrane device includes an acidic gas inlet pipe, an alkaline liquid storage unit, a brine storage unit, an acidic liquid storage unit, a polar liquid storage unit, and an electro-driven membrane stack. The alkaline liquid outlet of the alkaline liquid storage unit is connected to the alkaline chamber inlet of the electro-driven membrane stack, and the alkaline chamber outlet of the electro-driven membrane stack flows back to the alkaline liquid inlet of the alkaline liquid storage unit. The brine storage unit is divided into a brine chamber and a settling chamber by a partition. The brine outlet of the brine chamber is connected to the brine chamber inlet of the electro-driven membrane stack, and the brine chamber outlet of the electro-driven membrane stack is connected to the brine inlet of the settling chamber. The brine in the settling chamber overflows into the brine chamber. Acidic gas inlet pipes are independently connected to the alkali storage unit and the brine chamber, respectively. The acid outlet of the acid storage unit is connected to the acid chamber inlet of the electrically driven membrane stack, and the acid chamber outlet of the electrically driven membrane stack flows back to the acid inlet of the acid storage unit. The electrode outlet of the electrode storage unit is connected to the electrode chamber inlet of the electrically driven membrane, and the electrode chamber outlet of the electrically driven membrane flows back to the electrode inlet of the electrode storage unit. Furthermore, the electrically driven membrane stack consists of a positive electrode, a negative electrode, and at least one set of three-compartment electrodialysis units located between the positive and negative electrodes. Each set of three-compartment electrodialysis units consists of an electrically driven membrane, an anion membrane, and another anion membrane and another electrically driven membrane arranged sequentially.

2. An electro-driven membrane device and method for seawater carbon capture and mineralization as claimed in claim 1, comprising the following steps: (1) the pH values ​​of the alkaline solution and the brine can be adjusted independently; (2) the alkaline solution, brine, acidic liquid and electrode liquid can be circulated independently, and seed crystals are added in the settling chamber; (3) after the alkaline liquid, brine, acidic liquid and electrode liquid in step (2) start circulating, carbon dioxide gas is introduced into the alkaline liquid, and then the electro-driven membrane experiment is started after power is turned on. When the calcium ion concentration in the brine remains unchanged or changes little, the power is turned off, the gas valve is closed, and the electro-driven membrane experiment ends.

3. The electrically driven membrane device and method for seawater carbon capture and mineralization according to claim 1, characterized in that, The volume fraction of carbon dioxide in the acidic gas is 5-20%, and the concentration of carbon dioxide in the acidic gas is 800-15000 ppm.

4. The electrically driven membrane device and method for seawater carbon capture and mineralization according to claim 1, characterized in that, The steps include: (1) using carbon dioxide gas to independently adjust the pH of the alkaline solution and the brine to 7-9; (2) the alkaline solution, brine, acid solution, and polar solution can be independently circulated, and the Ca in the brine is... 2+ The concentration is 0.1-0.7 mg / g. Seed crystals with a mass of 0-30% of the calcium ion mass in the brine are added to the settling chamber; (3) After the alkaline solution, brine, acid solution and electrode liquid mentioned in step (2) start circulating, acidic gas is introduced into the alkaline solution. The circulation flow rate of the alkaline solution and the liquid-to-gas ratio of the acidic gas are 0.7-2.

5. At the same time, the electro-driven membrane experiment is started after the current is turned on, and the current density is set to 4-30 A / m. 2 The flow rate on the membrane surface can be adjusted within the range of 0.2-3 cm / s. When the calcium ion concentration in the brine changes little or remains constant, turn off the power supply and close the gas valve to end the electrically driven membrane experiment.

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