A method and device for recycling waste gypsum resources based on CO2 mineralization

Abstract

The application provides a waste gypsum resource utilization method and device based on CO2 mineralization, and belongs to the technical field of solid waste resource utilization. The waste gypsum is mixed with sulfuric acid for impurity removal treatment, the obtained impurity removal slurry is subjected to first solid-liquid separation, the obtained impurity removal waste gypsum is mixed with an amino auxiliary agent solution, CO2-rich gas is introduced into the obtained gypsum slurry for mineralization reaction, the obtained mineralization slurry is subjected to second solid-liquid separation, and calcium carbonate and mineralization filtrate are obtained; sodium sulfate solution containing high-valence metal complexes and sodium sulfate solution containing low-valence metal complexes are used as circulating electrode solutions, the mineralization filtrate is subjected to bipolar membrane electrodialysis treatment, and regenerated amino auxiliary agent solution and sulfuric acid by-products are obtained; the regenerated amino auxiliary agent solution is used for the mineralization reaction; and the sulfuric acid by-products are used for the impurity removal treatment. In the method, the amino auxiliary agent can be regenerated and recycled, and the treatment cost of waste gypsum resource utilization is low.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization technology, specifically to a method and apparatus for the resource utilization of waste gypsum based on CO2 mineralization. Background Technology

[0002] The greenhouse effect is currently the biggest environmental problem facing the international community. Compared with other carbon-emitting sectors in industry, the thermal power industry is one of the main sources of CO2 emissions. Therefore, from the perspective of controlling CO2 emissions, it is urgent to control CO2 emissions generated during power production, especially from coal-fired power plants. Industrial by-product gypsum is one of the by-products of power plant operation, possessing higher alkalinity and reactivity. However, the actual utilization rate of waste gypsum is currently less than 65%, resulting in resource waste. Against this backdrop, waste gypsum CO2 mineralization technology has attracted much attention. This technology can not only effectively fix CO2 but also generate carbon-rich materials to achieve product value-added, thereby promoting the resource utilization of waste gypsum.

[0003] However, the CO2 mineralization reaction system of waste gypsum is a continuously acidifying process, resulting in a low conversion rate of waste gypsum. Therefore, it is necessary to introduce exogenous alkaline reagents (such as sodium hydroxide solution) to regulate the pH value of the mineralization reaction process. However, during the mineralization reaction, the alkaline reagent is continuously consumed, and this process is irreversible and non-recyclable, increasing the processing cost of waste gypsum resource utilization. Summary of the Invention

[0004] The purpose of this invention is to provide a method and apparatus for the resource utilization of waste gypsum based on CO2 mineralization. In the method provided by this invention, the amino auxiliaries can be regenerated and recycled, and the processing cost of waste gypsum resource utilization is low.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for the resource utilization of waste gypsum based on CO2 mineralization, comprising the following steps:

[0007] Waste gypsum is mixed with sulfuric acid for impurity removal treatment to obtain impurity-removed slurry;

[0008] The impurity-removed slurry is subjected to a first solid-liquid separation to obtain impurity-removed waste gypsum;

[0009] The waste gypsum with impurities removed is mixed with an amino additive solution, and a gas rich in CO2 is introduced into the resulting gypsum slurry to carry out a mineralization reaction, thereby obtaining a mineralized slurry.

[0010] The mineralized slurry was subjected to a second solid-liquid separation to obtain calcium carbonate and mineralized filtrate, respectively.

[0011] Using sodium sulfate solutions containing high-valence metal complexes and low-valence metal complexes as circulating electrode solutions, the mineralized filtrate was subjected to bipolar membrane electrodialysis to obtain a regenerated amino auxiliary solution and sulfuric acid byproduct, respectively.

[0012] The regenerated amino auxiliary solution is reused in the mineralization reaction; the sulfuric acid byproduct is reused in the impurity removal treatment.

[0013] Preferably, the process further includes pretreating the mineralized filtrate by passing it through a resin column to remove impurity ions from the mineralized filtrate before the bipolar membrane electrodialysis treatment.

[0014] The pretreatment process further includes: using a portion of the sulfuric acid byproduct to perform a rinsing and regeneration treatment on the pretreated resin column to obtain a rinsing solution containing the impurity ions.

[0015] Preferably, the concentration of the amino auxiliary in the amino auxiliary solution is 0.1–2.0 mol / L; and the molar ratio of sulfur to amino auxiliary in the waste gypsum is 0.25–0.5:1.

[0016] Preferably, the amino auxiliary is an amino acid-based amino auxiliary and / or a non-amino acid-based amino auxiliary; the amino acid-based amino auxiliary includes glycine and / or alanine; the non-amino acid-based amino auxiliary includes one or more of primary amines, secondary amines, and tertiary amines; the primary amine includes one or more of ethanolamine, 3-aminopropanol, and 1,3-propanediamine; the secondary amine includes diethanolamine and / or piperazine; and the tertiary amine includes triethanolamine and / or diethylaminoethanol.

[0017] Preferably, the volume fraction of CO2 in the CO2-rich gas is 10-100%; the CO2-rich gas includes flue gas or biogas.

[0018] Preferably, the conditions for the mineralization reaction include: a temperature of 15–50°C and a time of 90–120 min.

[0019] Preferably, the high-valence metal complex and the low-valence metal complex contain the same type of metal element and the same type of ligand; the high-valence metal complex and the low-valence metal complex include any of the following:

[0020] Case 1: Fe 3+ -EDTA and Fe 2+ -EDTA;

[0021] Case 2: Fe 3+ -Cl and Fe 2+ -Cl;

[0022] Case 3: [Fe(CN)6] 3-With [Fe(CN)6] 4- ;

[0023] The concentrations of high-valence metal complexes and low-valence metal complexes in the circulating electrode solution are independently 0.05–0.15 mol / L, and the concentration of sodium sulfate is 0.1–0.5 mol / L. The conditions for the bipolar membrane electrodialysis treatment include: a voltage of 10–30 V and a current density of 10–50 mA / cm². 2 .

[0024] This invention provides a waste gypsum resource utilization device, comprising a purification reactor 1, a first solid-liquid separation device 2, a mineralization reaction vessel 3, a second solid-liquid separation device 4, and a bipolar membrane electrodialysis device 7 connected in sequence.

[0025] The bipolar membrane electrodialysis device 7 is connected to the mineralization reactor 3 through a regenerated amino auxiliary agent solution conveying pipeline, and the bipolar membrane electrodialysis device 7 is connected to the impurity removal reactor 1 through a first sulfuric acid by-product conveying pipeline.

[0026] Preferably, the waste gypsum resource utilization device further includes a resin column 6; the second solid-liquid separation device 4, the resin column 6 and the bipolar membrane electrodialysis device 7 are connected in sequence, and the bipolar membrane electrodialysis device 7 is connected to the resin column 6 through a second sulfuric acid by-product conveying pipeline.

[0027] Preferably, the waste gypsum resource utilization device further includes a miniature air cannon 5, which is connected to the second solid-liquid separation device 4.

[0028] This invention provides a method for the resource utilization of waste gypsum based on CO2 mineralization, comprising the following steps: mixing waste gypsum with sulfuric acid for impurity removal treatment to obtain a purified slurry; performing a first solid-liquid separation on the purified slurry to obtain purified waste gypsum; mixing the purified waste gypsum with an amino auxiliary agent solution, and introducing a CO2-rich gas into the resulting gypsum slurry to conduct a mineralization reaction to obtain a mineralized slurry; performing a second solid-liquid separation on the mineralized slurry to obtain calcium carbonate and a mineralized filtrate; using sodium sulfate solutions containing high-valence metal complexes and low-valence metal complexes as circulating electrode solutions, treating the mineralized filtrate with bipolar membrane electrodialysis to obtain a regenerated amino auxiliary agent solution and a sulfuric acid byproduct; reusing the regenerated amino auxiliary agent solution in the mineralization reaction; and reusing the sulfuric acid byproduct in the impurity removal treatment. The amino auxiliary agent in the method provided by this invention can be regenerated and recycled, resulting in low processing costs for the resource utilization of waste gypsum. Furthermore, this method enables efficient treatment of waste gypsum and effective CO2 sequestration.

[0029] Meanwhile, the present invention provides a waste gypsum resource utilization device. The waste gypsum resource utilization device provided by the present invention can realize the valuable conversion of waste gypsum, has low energy consumption, and can be built in solid waste production sites such as coal-fired power plants to realize the real-time production and disposal of waste gypsum. Attached Figure Description

[0030] Figure 1 This is a flowchart of the waste gypsum resource utilization method in an embodiment of the present invention;

[0031] Figure 2 This is a schematic diagram of the waste gypsum resource utilization device in an embodiment of the present invention, wherein 1 is a purification reactor, 2 is a first solid-liquid separation device, 3 is a mineralization reaction vessel, 4 is a second solid-liquid separation device, 5 is a micro air cannon, 6 is a resin column, and 7 is a bipolar membrane electrodialysis device.

[0032] Figure 3 This is another structural schematic diagram of the waste gypsum resource utilization device in an embodiment of the present invention (the connection relationship of the bipolar membrane electrodialysis equipment is not limited);

[0033] Figure 4 This is a diagram showing the membrane stack configuration of the bipolar membrane electrodialysis device in an embodiment of the present invention;

[0034] Figure 5 The graph shows the test results of liquid phase CO2 absorption, solid phase CO2 absorption and CO2 sequestration in gypsum slurry.

[0035] Figure 6 XRD patterns of calcium carbonate prepared in the examples and comparative examples;

[0036] Figure 7 The graph shows the purity test results of calcium carbonate prepared in the examples and comparative examples.

[0037] Figure 8 SEM images of calcium carbonate prepared in the examples and comparative examples;

[0038] Figure 9 The graph shows the changes in conductivity and pH value of the feed tank and the pH value of the acid tank during the electrodialysis treatment of the mineralized filtrate in Example 1.

[0039] Figure 10 This is a graph showing the change in current efficiency of the mineralized filtrate during electrodialysis treatment in Example 1;

[0040] Figure 11 This is a graph showing the changes in index parameters during the electrodialysis treatment process in Example 8;

[0041] Figure 12 This is a graph showing the changes in index parameters during the electrodialysis treatment process in the cyclic experiment of Example 9. Detailed Implementation

[0042] This invention provides a method for the resource utilization of waste gypsum based on CO2 mineralization, comprising the following steps:

[0043] Waste gypsum is mixed with sulfuric acid for impurity removal treatment to obtain impurity-removed slurry;

[0044] The impurity-removed slurry is subjected to a first solid-liquid separation to obtain impurity-removed waste gypsum;

[0045] The waste gypsum with impurities removed is mixed with an amino additive solution, and a gas rich in CO2 is introduced into the resulting gypsum slurry to carry out a mineralization reaction, thereby obtaining a mineralized slurry.

[0046] The mineralized slurry was subjected to a second solid-liquid separation to obtain calcium carbonate and mineralized filtrate, respectively.

[0047] Using sodium sulfate solutions containing high-valence metal complexes and low-valence metal complexes as circulating electrode solutions, the mineralized filtrate was subjected to bipolar membrane electrodialysis to obtain a regenerated amino auxiliary solution and sulfuric acid byproduct, respectively.

[0048] The regenerated amino auxiliary solution is reused in the mineralization reaction; the sulfuric acid byproduct is reused in the impurity removal treatment.

[0049] In this invention, unless otherwise specified, all raw materials used are commercially available products well known to those skilled in the art or prepared using methods well known to those skilled in the art.

[0050] This invention involves mixing waste gypsum with sulfuric acid for impurity removal, yielding a purified slurry. The waste gypsum described in this invention may include one or more of desulfurized gypsum, phosphogypsum, citric acid gypsum, titanium dioxide gypsum, and fluorogypsum, specifically desulfurized gypsum, phosphogypsum, citric acid gypsum, titanium dioxide gypsum, or fluorogypsum. The desulfurized gypsum is generated along with CO2 in the flue gas desulfurization unit of a coal-fired power plant after combustion, thus eliminating the need for additional transportation costs. In an embodiment of this invention, desulfurized gypsum is used as an example to verify the feasibility of the method. The chemical composition (mass percentage) of the desulfurized gypsum specifically includes: 46.9% CaO, 47.1% SO3, 2.8% SiO3, 1.7% MgO, 0.7% Al2O3, 0.2% Fe2O3, 0.2% K2O, and 0.1% Na2O. In this embodiment of the invention, the particle size of the waste gypsum can be 100–500 μm, specifically 100–150 μm. In this embodiment, the waste gypsum can be sequentially dried, ball-milled, and sieved, then mixed with sulfuric acid for impurity removal. The drying temperature can be 55–65°C, specifically 60°C, and the time can be 20–30 h, specifically 24 h. In this invention, the concentration of the sulfuric acid can be 0.1–0.5 mol / L, specifically 0.25 mol / L; the ratio of waste gypsum to sulfuric acid can be 50–80 g / L, specifically 60–68 g / L. In this invention, the sulfuric acid can be a sulfuric acid byproduct generated in the subsequent bipolar membrane electrodialysis treatment process. In this invention, the conditions for impurity removal include: a temperature of 25–45°C, specifically 25–30°C; and a time of 30–60 min, specifically 30–40 min. In this embodiment of the invention, the impurity removal process can remove impurity ions such as Al, As, Ba, Fe, Mn, and Zn from waste gypsum, which is beneficial to improving product purity.

[0051] After obtaining the purified slurry, the present invention performs a first solid-liquid separation on the purified slurry to obtain purified waste gypsum. The present invention does not have a special limitation on the method of the first solid-liquid separation, and filtration can be used to achieve solid-liquid separation.

[0052] After obtaining the purified waste gypsum, this invention mixes the purified waste gypsum with an amino auxiliary agent solution, and introduces a CO2-rich gas into the resulting gypsum slurry to carry out a mineralization reaction, obtaining a mineralized slurry. In this invention, the volume fraction of CO2 in the CO2-rich gas can be 10-100%, specifically 40-50%; the CO2-rich gas can include flue gas or biogas; in the embodiments of this invention, a CO2 and N2 mixture is specifically used as a simulated gas to verify the feasibility of the method of this invention. In this invention, the concentration of the amino auxiliary agent in the amino auxiliary agent solution can be 0.1-2.0 mol / L, specifically 0.5-1 mol / L, and further 0.8-1 mol / L; the molar ratio of sulfur to amino auxiliary agent in the waste gypsum can be 0.25-0.5:1, specifically 0.3-0.45:1, and further 0.4:1. The amino auxiliaries described in this invention can be amino acid-based amino auxiliaries and / or non-amino acid-based amino auxiliaries; the amino acid-based amino auxiliaries may include glycine and / or alanine; the non-amino acid-based amino auxiliaries may include one or more of primary amines, secondary amines, and tertiary amines; the primary amines may include one or more of ethanolamine (MEA), 3-aminopropanol (MPA), and 1,3-propanediamine (DAP); the secondary amines include diethanolamine (DEA) and / or piperazine (PZ); the tertiary amines include triethanolamine (TEA) and / or diethylaminoethanol (DEEA). In this invention, the above-mentioned types of amino auxiliaries are used as the alkaline medium, which has the following advantages: compared with NH4OH, they are less prone to volatilization at high temperatures; they can promote the growth of Ca in alkaline minerals. 2+ The leaching process can regulate the nucleation and growth of CaCO3 crystals.

[0053] In this embodiment of the invention, waste gypsum (after impurity removal) is mixed with an amino additive solution, and then a CO2-rich gas is introduced into the resulting gypsum slurry to carry out a mineralization reaction, yielding a mineralized slurry. In this invention, the introduction rate of the CO2-rich gas can be 100–1000 mL / min / L of gypsum slurry, specifically 833 mL / min / L of gypsum slurry. In this invention, the conditions for the mineralization reaction include: a temperature of 15–50°C, specifically 20–30°C; a time of 90–120 min, specifically 110–120 min; and the mineralization reaction can be carried out under stirring conditions, with a stirring rate of 250–350 rpm, specifically 300 rpm. In this embodiment of the invention, a pH meter and a gas analyzer can be used to monitor the pH value of the slurry and the concentration of CO2 in the CO2-containing gas in real time during the mineralization reaction. The amino auxiliaries can increase the solubility of calcium ions through complexation, control the progress of the mineralization reaction through a protection mechanism, and simultaneously dissolve all heavy metal ions in the solution. The protection mechanism refers to the organic amine auxiliaries reconstructing the CaSO4 mineral phase during the CO2 mineralization process, controlling the progress of the mineralization reaction by regulating the CO2 absorption and CaCO3 precipitation reaction (specifically, through the complexation of the amino auxiliaries, calcium ions are protected, preventing them from undergoing early mineralization). Simultaneously, the amino auxiliaries allow CaCO3 to nucleate independently, without encapsulating SiO2 and Al2O3 impurities. In this invention, during the mineralization reaction, the amino auxiliaries are protonated, simultaneously dissolving waste gypsum (mainly composed of calcium sulfate), resulting in a solution containing sulfate ions, protonated amino auxiliaries, and CO3. 2- / HCO3 - And a mixture of impurity heavy metal ions.

[0054] After obtaining the mineralized slurry, this invention performs a second solid-liquid separation to obtain calcium carbonate and mineralized filtrate. This invention does not specifically limit the method of the second solid-liquid separation; any method that achieves solid-liquid separation is acceptable. Specifically, the solid-liquid separation of the mineralized filtrate and calcium carbonate mixture can be performed online using a pulse-type backwashing electromagnetic control system. The solid-liquid separation method can be filtration; the filtration equipment can be a ceramic membrane filter (a sand core filter can be used in the laboratory). When using a ceramic membrane filter for filtration, the filter cake remaining on the ceramic membrane after filtration can be crushed and reused in the mineralization reaction; the crushing equipment can be a miniature air cannon. The calcium carbonate obtained by the second solid-liquid separation in this invention has a particle size smaller than SiO2 and Al2O3, therefore, a spiral separator can be used to separate SiO2 and Al2O3 from calcium carbonate, thereby obtaining high-purity calcium carbonate.

[0055] After obtaining the mineralized filtrate, this invention uses a sodium sulfate solution containing a high-valent metal complex and a sodium sulfate solution containing a low-valent metal complex as circulating electrode solutions to treat the mineralized filtrate by bipolar membrane electrodialysis, respectively obtaining a regenerated amino auxiliary agent solution and a sulfuric acid byproduct. In embodiments of this invention, the high-valent metal complex and the low-valent metal complex can contain the same type of metal element and the same type of ligand; the high-valent metal complex and the low-valent metal complex can include any of the following:

[0056] Case 1: Fe 3+ -EDTA and Fe 2+ -EDTA;

[0057] Case 2: Fe 3+ -Cl and Fe 2+ -Cl;

[0058] Case 3: [Fe(CN)6] 3- With [Fe(CN)6] 4- .

[0059] In this invention, the concentrations of high-valence metal complexes and low-valence metal complexes in the circulating electrode solution can be independently 0.05–0.15 mol / L, specifically 0.1 mol / L; the concentration of sodium sulfate can be 0.1–0.5 mol / L, specifically 0.3 mol / L. In this invention, the conditions for the bipolar membrane electrodialysis treatment include: a voltage of 10–30 V, specifically 15–20 V; and a current density of 10–50 mA / cm². 2 Specifically, it can be 15–22 mA / cm 2 In this embodiment of the invention, the membrane stack in the bipolar membrane electrodialysis treatment equipment can be a two-chamber configuration built from a bipolar membrane and anion exchange membrane, and the feeding mode can be a circulating feed. This invention can achieve desalination and regeneration of mineralized filtrate through bipolar membrane electrodialysis treatment. Specifically, during the bipolar membrane electrodialysis treatment process, the bipolar membrane dissociates water to provide OH-. - Protonated amino auxiliaries, while SO4 2- The desalination process is completed by separating the amino auxiliary agent from the anion exchange membrane, ultimately regenerating the amino auxiliary agent. This invention utilizes an amino auxiliary agent with two unique characteristics: firstly, it continuously accepts H₂ during the mineralization reaction. + When it is completely converted into protonated amino auxiliaries, it no longer absorbs CO2, ensuring that the subsequent mineralization filtrate has a low liquid-phase CO2 absorption rate. On the other hand, the regenerated amino auxiliaries produced during the bipolar membrane electrodialysis process capture more OH-. - It has strong buffering properties and can not only inhibit Ca 2+ Precipitation can also reduce OH groups. -The transmembrane migration of sulfate ions indirectly promotes the transmembrane migration of sulfate ions.

[0060] After obtaining the regenerated amino auxiliary agent solution, this invention reuses the regenerated amino auxiliary agent solution in the mineralization reaction. In this invention, the concentration of the regenerated amino auxiliary agent solution can be 0.1–2.0 mol / L, specifically 1.0–1.5 mol / L. When reusing the regenerated amino auxiliary agent solution in the mineralization reaction, some of the lost water (including water lost during the second solid-liquid separation and water lost during bipolar membrane electrodialysis) can be replenished. Taking 1L of regenerated amino auxiliary agent solution as an example, the amount of water replenished can be 40–80 mL.

[0061] After obtaining the sulfuric acid byproduct, the present invention reuses the sulfuric acid byproduct in the impurity removal treatment. The concentration of the sulfuric acid byproduct can be controlled by adjusting the initial feed ratio (mineralized filtrate) to the initial feed ratio (pure water) of the alkali tank in the bipolar membrane electrodialysis equipment; in the present invention, the concentration of the sulfuric acid byproduct can be 0.1–0.5 mol / L, specifically 0.25 mol / L.

[0062] The bipolar membrane electrodialysis treatment described in this invention may further include: pretreating the mineralized filtrate by passing it through a resin column to remove impurity ions from the mineralized filtrate. In this invention, the packing material in the resin column may be an ion-exchange resin. In this invention, the impurity ions may include one or more of Al, As, Ba, Fe, Mn, and Zn.

[0063] The pretreatment described in this invention may further include: rinsing and regenerating the pretreated resin column using a portion of the sulfuric acid byproduct. This invention does not specifically limit the specific operation method of the rinsing and regeneration treatment; methods well-known to those skilled in the art can be used.

[0064] This invention provides a waste gypsum resource utilization device, comprising a purification reactor 1, a first solid-liquid separation device 2, a mineralization reactor 3, a second solid-liquid separation device 4, and a bipolar membrane electrodialysis device 7 connected in sequence; the bipolar membrane electrodialysis device 7 is connected to the mineralization reactor 3 through a regenerated amino auxiliary agent solution conveying pipeline, and the bipolar membrane electrodialysis device 7 is connected to the purification reactor 1 through a first sulfuric acid by-product conveying pipeline.

[0065] The waste gypsum resource utilization device provided by the present invention includes a purification reactor 1 for removing impurities from waste gypsum. As an embodiment of the present invention, the waste gypsum resource utilization device further includes a drying oven, a ball mill, and a screen connected in sequence, with the discharge port of the screen connected to the purification reactor 1.

[0066] The waste gypsum resource utilization device provided by the present invention includes a first solid-liquid separation device 2 connected to a purification reactor 1, used for performing a first solid-liquid separation. As an embodiment of the present invention, the first solid-liquid separation device 2 may specifically be a filter.

[0067] The waste gypsum resource utilization device provided by the present invention includes a mineralization reaction vessel 3 connected to a first solid-liquid separation device 2 for carrying out a mineralization reaction. As an embodiment of the present invention, the mineralization reaction vessel 3 may specifically be a round-bottom reaction vessel. As an embodiment of the present invention, the waste gypsum resource utilization device further includes a blower connected to the mineralization reaction vessel 3 for blowing CO2-containing gas into the mineralization reaction vessel 3.

[0068] The waste gypsum resource utilization device provided by this invention includes a second solid-liquid separation device 4 connected to a mineralization reactor 3 for performing a second solid-liquid separation. In one embodiment of this invention, the second solid-liquid separation device 4 can specifically be a ceramic membrane filter. In another embodiment, the mineralization reactor 3 is connected to the second solid-liquid separation device 4 via a mineralization slurry conveying pipeline, and a mineralization slurry conveying pump is installed on the mineralization slurry conveying pipeline. In yet another embodiment, the waste gypsum resource utilization device further includes a miniature air cannon 5 connected to the second solid-liquid separation device 4. In yet another embodiment, a first solenoid valve is installed between the second solid-liquid separation device 4 and the miniature air cannon 5. This invention uses the miniature air cannon 5 to break up the filter cake accumulated on the ceramic membrane, and then conveys it to the mineralization reactor 3 through a powder conveying pipeline for mineralization reaction.

[0069] The waste gypsum resource utilization device provided by the present invention includes a bipolar membrane electrodialysis device 7 connected to a second solid-liquid separation device 4 for performing bipolar membrane electrodialysis treatment. As an embodiment of the present invention, the electrodialysis unit of the bipolar membrane electrodialysis device 7 includes a cathode electrode chamber, an alkali chamber, an acid chamber, and an anode electrode chamber. The alkali chamber and acid chamber are repeatable units, specifically configured as cathode electrode chamber-alkali chamber-acid chamber-anode electrode chamber, cathode electrode chamber-alkali chamber-acid chamber-alkali chamber-acid chamber-anode electrode chamber, or cathode electrode chamber-alkali chamber-acid chamber-alkali chamber-acid chamber-alkali chamber-acid chamber-anode electrode chamber, etc. The cathode electrode chamber and anode electrode chamber contain high-valence metal complexes (such as Fe). 3+ -EDTA) and low-valent metal complexes (such as Fe) 2+A sodium sulfate solution containing EDTA is used as the circulating electrode solution. The initial solution in the anode chamber can be a sodium sulfate solution containing low-valence metal complexes, the initial solution in the cathode chamber can be a sodium sulfate solution containing high-valence metal complexes, the initial solution in the alkali chamber can be mineralized filtrate, and the initial solution in the acid chamber can be deionized water or 0.1 mol / L dilute sulfuric acid. During the bipolar membrane electrodialysis process, the cathode and anode chambers are interconnected, using high-valence metal complexes as Fe... 3+ Taking EDTA as an example, Fe in the cathode electrode solution 3+ -EDTA accepts electrons and transforms into Fe. 2+ -EDTA, rich in Fe 2+ -EDTA cathode electrode solution is rapidly circulated to the anode chamber, Fe 2+ -EDTA loses electrons in the anode chamber and is regenerated as Fe. 3+ -EDTA and return to the cathode; the regeneration reaction of the protonated amino auxiliary agent and the migration of sulfate ions mainly occur in the alkali chamber. Furthermore, the protonated amino auxiliary agent receives OH generated by the bipolar membrane. - Free amines are generated, and sulfate ions in the base chamber continuously migrate across the membrane; the acid chamber mainly undergoes the sulfuric acid formation reaction. Furthermore, sulfate ions migrating from the base chamber continuously combine with H+ generated by the bipolar membrane. + After bipolar membrane electrodialysis treatment, the anolyte chamber, cathode chamber, alkali chamber, and acid chamber respectively produce complexes containing high-valence metals (such as Fe). 3+ Sodium sulfate solution containing EDTA, and complexes containing low-valent metals (such as Fe). 2+ The invention comprises a sodium sulfate solution of EDTA, a regenerated amino auxiliary agent solution, and sulfuric acid byproducts. Through the cyclic conversion of high-valence metal complexes and low-valence metal complexes, the occurrence of H2 and O2 production reactions from water splitting can be suppressed, thereby increasing the system current efficiency by 20-30%.

[0070] As an embodiment of the present invention, the waste gypsum resource utilization device further includes green electricity that provides power to the bipolar membrane electrodialysis equipment 7, an anode electrode chamber storage tank and a cathode electrode chamber storage tank connected to the bipolar membrane electrodialysis equipment 7; the green electricity can specifically be surplus electricity generated by wind power or hydropower.

[0071] In one embodiment of the present invention, the waste gypsum resource utilization device further includes a resin column 6; the second solid-liquid separation device 4, the resin column 6, and the bipolar membrane electrodialysis device 7 are sequentially connected (the resin column 6 is connected to the bipolar membrane electrodialysis device 7 via a mineralized filtrate delivery pipeline), and the bipolar membrane electrodialysis device 7 is connected to the resin column 6 via a second sulfuric acid by-product delivery pipeline. In one embodiment of the present invention, a second solenoid valve and a mineralized filtrate delivery pump are sequentially arranged between the second solid-liquid separation device 4 and the resin column 6. In one embodiment of the present invention, a third solenoid valve is arranged between the resin column 6 and the bipolar membrane electrodialysis device 7.

[0072] In the waste gypsum resource utilization device provided by this invention, waste gypsum can be processed to obtain calcium carbonate product and dilute sulfuric acid byproduct, without the need for large-scale consumption of external heat energy and external chemicals. In this invention, the amino auxiliaries and sodium sulfate solution containing high and low valence cation complexes can be regenerated and recycled, and the waste gypsum resource utilization process does not require large-scale consumption of external chemicals.

[0073] Figure 1 This is a flowchart of the waste gypsum resource utilization method in an embodiment of the present invention. Figure 2 This is a schematic diagram of the waste gypsum resource utilization device in an embodiment of the present invention. Figure 3 This is another structural schematic diagram of the waste gypsum resource utilization device in an embodiment of the present invention (the connection relationship of the bipolar membrane electrodialysis equipment is not limited). Figure 4 This is a diagram showing the membrane stack configuration of the bipolar membrane electrodialysis device in an embodiment of the present invention. The method of the present invention will now be described in detail:

[0074] Waste gypsum is dried in an oven, ball-milled, and sieved. It is then mixed with sulfuric acid in a purification reactor 1 for impurity removal. The resulting purified slurry undergoes a first solid-liquid separation in a first solid-liquid separation device 2 to obtain purified waste gypsum. The purified waste gypsum is then mixed with an amino auxiliary solution in a mineralization reactor 3, and air is blown in using an aerator to carry out a mineralization reaction, yielding a mineralized slurry. This mineralized slurry is then pumped to a second solid-liquid separation device 4 (specifically a ceramic membrane filter) for a second solid-liquid separation (simultaneously, the filter cake accumulated on the membrane is broken up using a micro air cannon 5 and then transported to the mineralization reactor 3), yielding calcium carbonate and mineralized filtrate respectively. Finally, the second solenoid valve is opened, and the mineralized filtrate is passed through a mineralization filter... The liquid is pumped to the resin column 6 for pretreatment to remove impurity ions (such as Al, As, Ba, Fe, Mn, Zn, etc.) from the mineralized filtrate. The third solenoid valve is opened, and the pretreated mineralized filtrate is pumped to the bipolar membrane electrodialysis device 7 for bipolar membrane electrodialysis treatment to obtain a regenerated amino auxiliary agent solution and sulfuric acid by-product. The regenerated amino auxiliary agent solution is pumped to the mineralization reactor 3 for mineralization reaction. Part of the sulfuric acid by-product is pumped to the impurity removal reactor 1 for impurity removal treatment. The remaining sulfuric acid by-product is pumped to the resin column 6 for rinsing and regeneration treatment to obtain a rinsing solution containing the impurity ions (such as Al, As, Ba, Fe, Mn, Zn, etc.).

[0075] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0076] The chemical composition (mass percentage) of the desulfurized gypsum used in the following examples includes: 46.9% CaO, 47.1% SO3, 2.8% SiO3, 1.7% MgO, 0.7% Al2O3, 0.2% Fe2O3, 0.2% K2O and 0.1% Na2O.

[0077] Example 1

[0078] (1) The desulfurized gypsum was dried in an oven at 60°C for 24 hours, ground finely with a ball mill, and sieved. The sieved material (100-150 μm) was collected and mixed with sulfuric acid at a concentration of 0.25 mol / L at a ratio of 0.069 kg: 1 L. The mixture was then subjected to impurity removal treatment at 25°C for 30 minutes to obtain impurity-removed slurry. The impurity-removed slurry was filtered to obtain impurity-removed waste gypsum. The impurity-removed waste gypsum was mixed with an organic amine auxiliary agent (specifically MEA) solution at a concentration of 1 mol / L to obtain gypsum slurry. The molar ratio of sulfur to organic amine auxiliary agent in the desulfurized gypsum was 0.4:1.

[0079] (2) A mixture of 40 vol% CO2 and 60 vol% N2 gas was introduced into the gypsum slurry prepared in step (1) at a ventilation rate of 0.833 mL / min. The mineralization reaction was carried out for 120 min under sealed conditions at a temperature of 30 °C and a stirring rate of 300 rpm (the gas was continuously ventilated during the reaction, and the chemical characteristics of the slurry system were monitored online using a pH meter and an infrared gas analyzer. The pH value of the slurry system was maintained at 7-8 at the end of the reaction) to ensure that the mineralization reaction reached equilibrium and a mineralized slurry was obtained.

[0080] (3) After filtering the mineralized slurry prepared in step (2) through a filter (specifically a sand core filter), calcium carbonate and mineralized filtrate are obtained respectively. The pH value of the mineralized filtrate is 7.81, the conductivity is 32mS / cm, and the total concentration of calcium ions and magnesium ions is 370mg / L.

[0081] (4) The mineralized filtrate is passed into a bipolar membrane electrodialysis system for electrodialysis treatment. Specifically, the mineralized filtrate is placed in an alkali tank, 1L of pure water is added to an acid tank, and 0.5L of Fe-containing solution is added to an acid tank. 2+ -EDTA sodium sulfate solution (Fe 2+ (EDTA concentration of 0.1 mol / L and sodium sulfate concentration of 0.3 mol / L) are placed in the anode tank, and 0.5 L of Fe-containing solution is taken. 3+ -EDTA sodium sulfate solution (Fe 3+A solution with EDTA concentration of 0.1 mol / L and sodium sulfate concentration of 0.3 mol / L is placed in the cathode tank. The bipolar membrane electrodialysis system is connected to the four tanks via pipelines, using a bottom-in, top-out solution inflow / outflow method. The membrane stack is a two-compartment stack, with the internal components consisting of a cathode plate, a circulation unit, a bipolar membrane, and an anode plate. There are five circulation units, each consisting of a bipolar membrane, a two-channel partition, an anion exchange membrane, and a two-channel partition, with the cathode plate as the reference. The circulating electrode solution between the bipolar membrane and the cathode plate, and between the bipolar membrane and the anode plate, is a 0.3 mol / L sodium sulfate solution. The peristaltic pump is turned on, and the circulation flow rate of the solution in each tank is controlled at 20 L / h. After the air bubbles in the bipolar membrane electrodialysis system are completely expelled, i.e., after the solution in each tank has circulated for 20 minutes, the DC power supply is turned on, and the operating voltage is controlled at 20V and the current density at 22 mA / cm². 2 Electrodialysis is performed; when the conductivity of the alkali tank drops to 3 mS / cm, the current is reduced in stages, then the current output is turned off, and then the peristaltic pump is turned off, to obtain a regenerated organic amine auxiliary solution and sulfuric acid by-product respectively; the regenerated organic amine auxiliary solution is reused in the mineralization reaction; the sulfuric acid by-product is reused in the impurity removal treatment.

[0082] Examples 2-7

[0083] The procedure was performed according to Example 1, except that the organic amine auxiliaries were replaced with MPA, TEA, DEEA, DEA, PZ and DAP, respectively.

[0084] Comparative Example 1

[0085] The procedure was followed as in Example 1, except that the organic amine auxiliaries were replaced with NaOH.

[0086] Comparative Example 2

[0087] The procedure is the same as in Example 1, except that the organic amine auxiliaries are omitted.

[0088] Test Example 1

[0089] The calcium carbonate prepared in the examples and comparative examples was washed three times with water and then dried in an oven at 80°C. The purity, crystal form, morphology and CO2 sequestration of the products were then tested.

[0090] Figure 5The graph shows the test results of liquid-phase CO2 absorption, solid-phase CO2 absorption, and CO2 sequestration capacity of gypsum slurry. The results show that the CO2 sequestration capacity of desulfurized gypsum after 120 min of mineralization reactions with MEA, MPA, TEA, DEEA, DEA, PZ, and DAP are 355.4 g / kg-FGD (i.e., 1 kg of desulfurized gypsum can sequester 355.4 g of CO2), 354.4 g / kg-FGD, 220.5 g / kg-FGD, 346.4 g / kg-FGD, 343.7 g / kg-FGD, 341.2 g / kg-FGD, and 348.5 g / kg-FGD, respectively. This indicates that the CO2 sequestration capacity of gypsum is significantly increased under the condition of using organic amine additives.

[0091] Figure 6 The XRD patterns of calcium carbonate prepared in the examples and comparative examples are shown. The results show that the calcium carbonate prepared using DAP has only the aragonite crystal form; the calcium carbonate prepared using MEA has a mixed crystal form of aragonite and calcite; the calcium carbonate prepared using MPA has a mixed crystal form of aragonite, calcite, and aragonite; the calcium carbonate prepared using PZ and DEA has only the calcite crystal form; the calcium carbonate prepared using DEEA has a mixed crystal form of calcite and aragonite; although the gypsum conversion rate is lower when using TEA, the proportion of aragonite crystal form in the product is higher; and only the calcite crystal form of calcium carbonate is obtained when using NaOH.

[0092] Figure 7 The figure shows the purity test results of calcium carbonate prepared in the examples and comparative examples. The results show that the purity of calcium carbonate prepared by using MEA and MPA is 90%, the purity of calcium carbonate prepared by using DEEA and DAP is 88%, the purity of calcium carbonate prepared by using DEA and PZ is 87%, and the purity of calcium carbonate prepared by using TEA is 56%.

[0093] Figure 8 The images show SEM images of calcium carbonate prepared in the examples and comparative examples. The results show that the calcium carbonate prepared by MEA is spherical; the calcium carbonate prepared by MPA is a mixture of spherical, needle-shaped and blocky particles; the calcium carbonate prepared by DEEA is a mixture of square and needle-shaped particles; and the calcium carbonate prepared by DEA is a mixture of rod-shaped and flower-shaped particles.

[0094] Figure 9 The graph shows the changes in conductivity and pH of the material in the alkali tank and the pH of the material in the acid tank during the electrodialysis treatment of the mineralized filtrate in Example 1. The results show that during the electrodialysis treatment, the pH of the material in the alkali tank continuously increases and the conductivity continuously decreases. The final pH of the regenerated organic amine auxiliary solution is 11.11.

[0095] Figure 10 The graph shows the change in current efficiency of the mineralized filtrate during electrodialysis treatment in Example 1. The results show that the current efficiency continuously decreases during the electrodialysis treatment, with a maximum current efficiency of 54.19%. The final recovered concentration of sulfuric acid byproduct (based on sulfate concentration) is 0.26 mol / L, and the energy consumption is 3.36 kWh / kg-H2SO4.

[0096] Example 8

[0097] The procedure is the same as in Example 1, whereby the treated waste gypsum is mixed with a 1 mol / L organic amine auxiliary agent (specifically MEA) solution to obtain a gypsum slurry. The difference lies in that the molar ratio of sulfur to organic amine auxiliary agent in the desulfurized gypsum in Example 8 is 0.45:1, 0.46:1, 0.47:1, 0.48:1, and 0.49:1, respectively (where the molar ratio of sulfur to organic amine auxiliary agent in the desulfurized gypsum is 0.45:1, corresponding to the organic amine auxiliary agent...). The protonation percentage of the agent is 90%. The corresponding protonation percentage of the organic amine auxiliary is 92% when the molar ratio is 0.46:1, 94% when the molar ratio is 0.47:1, 96% when the molar ratio is 0.48:1, and 98% when the molar ratio is 0.49:1. The number of circulation units in the bipolar membrane electrodialysis system is 10.

[0098] Figure 11 This is a graph showing the changes in index parameters during the electrodialysis treatment process in Example 8. Figure 11 (a) in Example 8 shows the changes in pH and conductivity of the material in the alkali tank during the electrodialysis treatment of the mineralized filtrate. It can be clearly seen that the lower the percentage of protonation, the shorter the electrodialysis treatment time. However, this may be because the range of the percentage of protonation in the feed liquid is relatively small, so the time required for solution treatment is not much different. Figure 11 (b) is a graph showing the change in membrane stack voltage during the electrodialysis treatment of the mineralized filtrate in Example 8. The results show that the voltage change trend of the membrane stack is similar within the above-mentioned protonation percentage range. Figure 11 (c) and (d) in Example 8 respectively show the changes in sulfate concentration and current efficiency in the acid tank during the electrodialysis treatment of the mineralized filtrate. It can be seen that the higher the percentage of protonation, the more sulfate is recovered in the end, and the current efficiency is between 20% and 40%.

[0099] Example 9

[0100] Following the method in Example 1, a cyclic experiment was conducted. The experimental process included a cyclic mineralization reaction process and a bipolar membrane electrodialysis treatment process, specifically denoted as M1-R1-M2-R2-M3-R3-M4-R4-M5-R5-M6, where M represents the mineralization reaction process and R represents the bipolar membrane electrodialysis treatment process of the filtrate obtained from M. Specifically, M1 represents the first mineralization reaction process, R1 represents the first bipolar membrane electrodialysis treatment process of the filtrate obtained from M1, and so on. Furthermore, the organic amine additive used in M2, M3, M4, M5, and M6 is a regenerated organic amine additive, and the number of cyclic units in the bipolar membrane electrodialysis system is 7.

[0101] Figure 12 This is a graph showing the changes in index parameters during the electrodialysis treatment process in the cyclic experiment of Example 9. Figure 12 (a) and (b) in the figure show the changes in conductivity of the materials in the alkali and acid tanks over time during five consecutive bipolar membrane electrodialysis treatments, respectively; (c) and (d) show the changes in pH value of the materials in the alkali and acid tanks over time during five consecutive bipolar membrane electrodialysis treatments, respectively. The results show that the protonated organic amine auxiliaries are reacted with OH produced during the bipolar membrane electrodialysis treatment. - Neutralization generates free amine molecules, and the organic amine is regenerated and stabilized. Figure 12 Figure (e) shows the change in sulfate concentration in the acid tank during five consecutive bipolar membrane electrodialysis treatments. The results show that the recovered sulfate concentration in the acid tank was approximately 0.25 mol / L during the five consecutive bipolar membrane electrodialysis treatments, indicating that the sulfuric acid recovery rate was stable. Figure 12 Figure (f) shows the change in current efficiency in the acid tank during five consecutive bipolar membrane electrodialysis treatments. The results show that the current efficiency remained stable at 40-60% during the five consecutive bipolar membrane electrodialysis treatments. Figure 12 Figure (g) shows the voltage change of the membrane stack during five consecutive bipolar membrane electrodialysis treatments. The results show that the voltage in the stable region increased significantly during the fourth and fifth bipolar membrane electrodialysis treatments, indicating that the resistance of the membrane stack increased. Figure 12 The graph in middle (h) shows the energy consumption during the five consecutive bipolar membrane electrodialysis treatments. The results show that the energy consumption during the five consecutive bipolar membrane electrodialysis treatments is 3.3 to 2.7 kWh / kg-H2SO4.

[0102] As can be seen from the above embodiments and test examples, the organic amine auxiliary recycling method of green electricity-driven bipolar membrane electrodialysis provided by the present invention, which enhances the process of capturing CO2 and producing CaCO3 in waste gypsum, co-degrading high oxides, and recovering green hydrogen, can solve the problems of irreversible consumption of alkaline reagents and low resource utilization rate of waste gypsum in existing technologies. Specifically, traditional waste gypsum mineralization technology usually uses inorganic bases such as NaOH and NH4OH, whose main function is to provide OH- for the mineralization reaction process.- However, it is difficult to recycle. This invention introduces an organic amine auxiliary, which can not only provide OH... - Furthermore, it can enhance the CO2 gas-liquid mass transfer process and regulate the crystal form of the product CaCO3. Most importantly, it can recover organic alkalis without introducing exogenous alkaline chemical reagents. This invention, with relatively low energy consumption, not only achieves CO2 emission reduction, resource utilization of waste gypsum, and recycling of organic amine additives, but also obtains high-purity CaCO3. By introducing electrochemistry into the traditional CO2 mineralization method, it provides a new approach to pollution reduction and carbon reduction. While utilizing electrodialysis to regenerate organic amine additives and recover polyvalent heavy metal ions, the anode and cathode chambers of the bipolar membrane electrodialysis system respectively generate and lose electrons, which can synergistically reduce high-valence oxides and recover green hydrogen.

[0103] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for the resource utilization of waste gypsum based on CO2 mineralization, characterized in that, Includes the following steps: Waste gypsum is mixed with sulfuric acid for impurity removal treatment to obtain impurity-removed slurry; The impurity-removed slurry is subjected to a first solid-liquid separation to obtain impurity-removed waste gypsum; The waste gypsum with impurities removed is mixed with an amino additive solution, and a gas rich in CO2 is introduced into the resulting gypsum slurry to carry out a mineralization reaction, thereby obtaining a mineralized slurry. The mineralized slurry was subjected to a second solid-liquid separation to obtain calcium carbonate and mineralized filtrate, respectively. Using sodium sulfate solutions containing high-valence metal complexes and low-valence metal complexes as circulating electrode solutions, the mineralized filtrate is pretreated by passing it through a resin column to remove impurity ions from the mineralized filtrate. Then, it is subjected to bipolar membrane electrodialysis to obtain a regenerated amino auxiliary solution and sulfuric acid byproduct, respectively. The regenerated amino auxiliary solution is reused in the mineralization reaction; the sulfuric acid byproduct is reused in the impurity removal treatment and in the rinsing and regeneration treatment of the pretreated resin column; The high-valence metal complex and the low-valence metal complex contain the same type of metal element and the same type of ligand; the high-valence metal complex and the low-valence metal complex include any of the following: Case 1: Fe 3+ -EDTA and Fe 2+ -EDTA; Case 2: Fe 3+ -Cl and Fe 2+ -Cl; Case 3: [Fe(CN)6] 3- With [Fe(CN)6] 4- ; The concentrations of high-valence metal complexes and low-valence metal complexes in the circulating electrode solution are independently 0.05–0.15 mol / L, and the concentration of sodium sulfate is 0.1–0.5 mol / L. The conditions for the bipolar membrane electrodialysis treatment include: a voltage of 10–30 V and a current density of 10–50 mA / cm². 2 .

2. The method for resource utilization of waste gypsum according to claim 1, characterized in that, The concentration of the amino auxiliary in the amino auxiliary solution is 0.1~2.0 mol / L; the molar ratio of sulfur to amino auxiliary in the waste gypsum is 0.25~0.5:

1.

3. The method for resource utilization of waste gypsum according to claim 2, characterized in that, The amino auxiliaries are amino acid-based amino auxiliaries and / or non-amino acid-based amino auxiliaries; the amino acid-based amino auxiliaries include glycine and / or alanine; the non-amino acid-based amino auxiliaries include one or more of primary amines, secondary amines, and tertiary amines; the primary amines include one or more of ethanolamine, 3-aminopropanol, and 1,3-propanediamine; the secondary amines include diethanolamine and / or piperazine; and the tertiary amines include triethanolamine and / or diethylaminoethanol.

4. The method for resource utilization of waste gypsum according to claim 1, characterized in that, The CO2-rich gas has a CO2 volume fraction of 10-100%; the CO2-rich gas includes flue gas or biogas.

5. The method for resource utilization of waste gypsum according to claim 1, characterized in that, The conditions for the mineralization reaction include: a temperature of 15~50℃ and a time of 90~120min.

6. A device for the resource utilization of waste gypsum based on CO2 mineralization, characterized in that, It includes a sequentially connected impurity removal reactor (1), a first solid-liquid separation device (2), a mineralization reactor (3), a second solid-liquid separation device (4), and a bipolar membrane electrodialysis device (7). The bipolar membrane electrodialysis device (7) is connected to the mineralization reactor (3) through a regenerated amino auxiliary agent solution conveying pipeline, and the bipolar membrane electrodialysis device (7) is connected to the impurity removal reactor (1) through a first sulfuric acid by-product conveying pipeline.

7. The waste gypsum resource utilization device according to claim 6, characterized in that, It also includes a resin column (6); the second solid-liquid separation device (4), the resin column (6) and the bipolar membrane electrodialysis device (7) are connected in sequence, and the bipolar membrane electrodialysis device (7) is connected to the resin column (6) through the second sulfuric acid by-product conveying pipeline.

8. The waste gypsum resource utilization device according to claim 6 or 7, characterized in that, It also includes a miniature air cannon (5), which is connected to the second solid-liquid separation device (4).

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