Hardness removal and desulfurization and dechlorination device for high-salinity wastewater using carbide slag

Abstract

This utility model relates to a device for desulfurization, dechlorination, and hardening of high-salinity wastewater using calcium carbide slag, belonging to the field of industrial wastewater treatment technology. The method includes steps such as heavy metal removal, magnesium ion removal, two-stage desulfurization and dechlorination, and calcium ion removal, sequentially achieving the removal of heavy metals and magnesium ions from the wastewater. 2+ SO4 2‑ Cl ‑ and Ca 2+ The system achieves efficient removal of calcium carbide slag, and the resulting precipitate is partially recycled for desulfurization after solid-liquid separation. The device includes a neutralization tank, a magnesium precipitation tank, a first reaction tank, a second reaction tank, a calcium precipitation tank, a desulfurization tower, a blower, and multi-stage solid-liquid separation units. It features a compact structure and clear division of labor. This invention fully utilizes calcium carbide slag solid waste resources, achieving high treatment efficiency, low operating costs, and resource-based utilization of byproducts. It possesses good engineering adaptability and economic and environmental benefits.

Description

Technical Field

[0001] This application relates to the field of industrial wastewater treatment technology, and in particular to a method and apparatus for dehardening, desulfurizing and dechlorinating high-salt wastewater using carbide slag. Background Technology

[0002] With increasingly stringent environmental standards, industrial enterprises are placing higher demands on achieving near-zero discharge of high-salinity wastewater. High-salinity wastewater, particularly from power plants and the chemical industry, typically contains large amounts of calcium. 2+ Mg 2+ SO4 2- With Cl - Plasma components not only lead to high water hardness, but may also cause severe scaling and corrosion during subsequent membrane treatment and thermal concentration processes, affecting equipment operational stability and reuse efficiency.

[0003] Several hardening and desalination technologies have been proposed. For example, Chinese invention patent CN119143314A provides a method for hardening using a combination of sodium carbonate and magnesium chloride solutions. This method can effectively precipitate calcium ions, but its removal efficiency for magnesium ions is limited; and although magnesium chloride can accelerate the formation of calcium sulfate precipitation under alkaline conditions, incomplete precipitation still exists. Furthermore, the formed magnesium carbonate colloid interferes with the ion reaction process, making the precipitate difficult to separate or recover, thus limiting its applicability to complex wastewater systems with high loads and high hardness.

[0004] To reduce processing costs, Chinese patent CN117700017A attempted to use low-cost sodium sulfate to replace part of the sodium carbonate to remove calcium ions. While this method is somewhat economical, it is limited to removing hardness and cannot effectively remove SO4. 2- and Cl - Plasmatic components. In high-salinity wastewater, the presence of these anions will severely limit the wastewater concentration ratio and the depth of reuse.

[0005] For SO4 2- and Cl - Currently, SO4 removal mainly relies on membrane concentration followed by evaporation and crystallization, but this process requires high investment and consumes a lot of energy, limiting its industrial-scale application. In addition, while ion exchange and electrochemical technologies can remove SO4, they are not the only methods available. 2- and Cl - However, it has problems such as high operating costs and frequent replacement of resin or electrodes.

[0006] In recent years, studies have proposed the "ultra-high lime-alumina method" for removing Cl. - Anion removal methods, such as those described in patent CN112429877A, involve reacting sodium aluminate with Ca(OH)₂ under high pH conditions to form Freund's salt precipitate, thereby removing chloride ions. However, this method suffers from insufficient sulfate pretreatment, and SO₄²⁻...2- The residue will significantly inhibit the subsequent precipitation reaction of chloride ions. In addition, most of these methods use conventional reagents such as lime and sodium carbonate, which are still costly, and the precipitates are difficult to utilize as resources.

[0007] To address the aforementioned issues, this application optimizes and upgrades the traditional dual-alkali process, proposing a method and apparatus for the overall dehardening, desulfurization, and dechlorination of high-salinity wastewater using an ultra-high lime-aluminate process with calcium carbide slag. This method removes key pollutants such as heavy metals, magnesium ions, sulfate ions, chloride ions, and calcium ions sequentially through a staged reaction. During the reaction, calcium carbide slag replaces traditional lime, significantly reducing treatment costs; a two-stage calcium carbide slag-sodium aluminate reaction unit is introduced to reduce SO4 levels. 2- The calcium ions react with C1 to form ettringite and Fraunhofer salt precipitates, effectively avoiding reaction inhibition. CO2 gas is introduced at the end, supplemented with Na2CO3 for adjustment, to achieve complete removal of calcium ions, while simultaneously reducing the system pH and conductivity, thus lessening the burden on subsequent treatment. This method also achieves solid-liquid separation through plate and frame filtration or centrifugation. The resulting ettringite and Fraunhofer salt precipitates can be used as components of cementitious materials or for the stabilization treatment of heavy metal / salt pollutants, demonstrating good economic and environmental performance. It is particularly suitable for the deep treatment and zero-discharge transformation of high-salinity wastewater in power plants, coal chemical industries, and other fields. Utility Model Content

[0008] To address the aforementioned problems, this application provides a device for desulfurization, dechlorination, and hardening of high-salinity wastewater using calcium carbide slag. This device can achieve multiple purification treatments of high-salinity wastewater using industrial waste calcium carbide slag, and features a simple structure and strong adaptability. To achieve the objectives of this application, the following technical solution is provided:

[0009] This application provides a device for dehardening, desulfurization, and dechlorination of high-salinity wastewater using carbide slag, comprising the following components connected in sequence:

[0010] The neutralization tank is used to add carbide slag and TMT-15. It is equipped with a pH adjustment and stirring device to adjust the pH value to 9.0-9.5 in order to remove heavy metal ions from the wastewater.

[0011] Magnesium precipitation tank, used for adding carbide slag and precipitating Mg. 2+ It is equipped with a stirring system to adjust the pH value to 11.0–12.5, so that Mg… 2+ The precipitate, in the form of magnesium hydroxide, was removed;

[0012] The first reaction tank is used to add carbide slag and sodium aluminate to remove SO4. 2- With some Cl - It is equipped with a stirring and reagent dosing device to control the pH value between 11.5 and 13.5, so that SO42- can be controlled. 2- With Ca 2+Al 3+ The reaction produces ettringite precipitate and removes some Cl. -

[0013] The second reaction tank is used to add carbide slag and sodium aluminate for further removal of Cl. - It is equipped with a stirring and reagent dosing device, and the pH value is controlled at 11.5–13.5 to allow Cl to form. - With Ca 2+ Al 3+ The reaction produces Freund's salt precipitate;

[0014] Calcium precipitation tank, used to introduce CO2 and add Na2CO3 to precipitate Ca. 2+ It is equipped with a CO2 bubbling device, a Na2CO3 dosing system, and a pH control device to adjust the pH to 9.0–9.5, so that Ca... 2+ The precipitate, in the form of calcium carbonate, is removed;

[0015] Desulfurization towers are used to receive the treated supernatant and some precipitates.

[0016] A blower, a CO2 bubbling device connecting the desulfurization tower outlet to the calcium precipitation tank;

[0017] The solid-liquid separation unit group includes a first plate and frame filter press, a first centrifuge, a second plate and frame filter press, and a second centrifuge;

[0018] in:

[0019] The first plate and frame filter press is connected to the bottom sediment outlet of the magnesium sedimentation tank;

[0020] The first centrifuge is connected to the sediment outlet at the bottom of the first reaction tank;

[0021] The second plate and frame filter press is connected to the bottom sediment outlet of the second reaction tank;

[0022] The second centrifuge is connected to the bottom sediment outlet of the calcium precipitation tank.

[0023] In one possible implementation, the supernatant outlet of the magnesium precipitation tank is connected to the desulfurization tower via a pipeline;

[0024] The outlet of the first plate and frame filter press is connected to the desulfurization tower.

[0025] In one possible implementation, the solid-liquid separation unit group includes:

[0026] The first plate and frame filter press is used to separate magnesium hydroxide precipitate from the magnesium precipitation tank;

[0027] The first centrifuge is used to separate ettringite and Freund's salt precipitate from the first reaction tank;

[0028] The second plate and frame filter press is used to separate the Freund's salt precipitate from the second reaction tank;

[0029] The second centrifuge is used to separate calcium carbonate precipitate from the calcium precipitation tank.

[0030] In one possible implementation, the fan pressurizes and delivers the CO2-containing flue gas from the desulfurization tower outlet to the CO2 bubbling device in the calcium precipitation tank.

[0031] Beneficial effects:

[0032] (1) This application uses carbide slag as the main alkaline neutralizing agent and calcium source to replace traditional chemical reagents, which not only reduces the treatment cost, but also realizes the resource utilization of solid waste, and has good environmental and economic benefits.

[0033] (2) This application utilizes a multi-stage reaction system to remove heavy metals and magnesium from high-salt wastewater in steps. 2+ SO4 2- Cl - and Ca 2+ With optimized conditions at each stage, high removal efficiency, and a significant improvement in the final effluent quality, it is suitable for recycling or compliant discharge in desulfurization systems.

[0034] (3) This application utilizes a two-stage reaction tank to add calcium carbide slag and sodium aluminate in stages, synergistically generating Freund's salt under alkaline conditions, effectively solving the problem of Cl... - The problem is difficult to remove, so we can avoid the risk of corrosion to the subsequent desulfurization system.

[0035] (4) This application effectively removes Ca by introducing CO2 gas into a calcium precipitation tank to selectively react with Na2CO3. 2+ At the same time, the CO2-containing tail gas from the desulfurization tower outlet is recovered and reused by the fan, reducing carbon emissions and reflecting the characteristics of green and low-carbon technology.

[0036] (5) The reaction unit, dosing system and solid-liquid separation equipment of this application are reasonably matched, the process is continuous, and it is convenient for layout, operation and maintenance in actual engineering.

[0037] (6) The device described in this application is equipped with corresponding equipment according to the processing functions of each stage, such as a stirring device, pH control system, bubbling system and multi-channel solid-liquid separation unit, which can flexibly adapt to different types of saline wastewater and treatment volume requirements, and has strong engineering adaptability.

[0038] (7) The solid products such as magnesium hydroxide, ettringite, Freund’s salt, and calcium carbonate generated in this application can be reused in the desulfurization process or further utilized for resource recovery after solid-liquid separation, thereby improving the overall resource utilization efficiency of the entire system. Attached Figure Description

[0039] The accompanying drawings are provided to further understand this application and form part of the specification. They are used together with the embodiments of this application to explain this application and do not constitute a limitation thereof.

[0040] Figure 1 A schematic diagram of a method and apparatus for dehardening, desulfurizing, and dechlorinating high-salt wastewater using carbide slag, provided in this application embodiment;

[0041] Figure 2 This is a schematic diagram illustrating the change in solution hardness in a magnesium precipitation tank with the amount of calcium carbide slag added, provided in an embodiment of this application.

[0042] Figure 3 This is a schematic diagram illustrating the change in pH of the solution in the magnesium precipitation tank with the amount of calcium carbide slag added, provided in an embodiment of this application.

[0043] Figure 4 SO4 in the first reaction tank provided in the embodiments of this application 2- Schematic diagram of removal rate change;

[0044] Figure 5 Cl in the second reaction tank provided in the embodiments of this application - Schematic diagram of removal rate change.

[0045] The components include: 1. Desulfurization tower; 2. Fan; 3. Neutralization tank; 4. Magnesium precipitation tank; 5. First plate and frame filter press; 6. First reaction tank; 7. First centrifuge; 8. Second reaction tank; 9. Second plate and frame filter press; 10. Calcium precipitation tank; 11. Second centrifuge. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0047] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature; in the description of this application, unless otherwise stated, "multiple" means two or more.

[0048] Example 1

[0049] Figure 1A process flow for desulfurization and dechlorination of high-salinity wastewater using carbide slag, provided in this application embodiment, includes the following steps:

[0050] S1. Heavy metal removal: High-salt wastewater is introduced into a neutralization tank (3), and carbide slag and TMT-15 are added to adjust the pH value to 9.0-9.5 in order to remove heavy metal ions in the wastewater.

[0051] S2. Magnesium ion removal: The neutralized wastewater is introduced into the magnesium precipitation tank (4), and carbide slag is added to adjust the pH value to 11.0-12.5, so that Mg... 2+ Magnesium hydroxide precipitate is removed; the mixed precipitate containing magnesium hydroxide at the bottom of the magnesium precipitation tank (4) is returned to the desulfurization tower (1) for desulfurization after being filtered by the first plate and frame filter press (5);

[0052] S3, First stage desulfurization and dechlorination: The supernatant from the magnesium precipitation tank (4) is diluted 10 times and introduced into the first reaction tank (6). Calcium carbide slag and sodium aluminate are added, and the pH is controlled at 11.5–13.5 to reduce SO4 levels. 2- With Ca 2+ Al 3+ The reaction produces ettringite precipitate and removes some Cl. - The sediment at the bottom of the first reaction tank (6) is dehydrated by the first centrifuge (7) and then discharged.

[0053] S4. Second-stage dechlorination: The effluent from the first reaction tank (6) is introduced into the second reaction tank (8), and calcium carbide slag and sodium aluminate are added continuously. The pH value is controlled at 11.5-13.5 to allow the chloride ion to dissolve. - With Ca 2+ Al 3+ The reaction produces Freund's salt precipitate; the precipitate at the bottom of the second reaction tank (8) is discharged after being filtered by the second plate and frame filter press (9);

[0054] S5. Calcium ion removal: The effluent from the second reaction tank (8) is introduced into the calcium precipitation tank (10), CO2 gas is introduced, and Na2CO3 is selectively added to adjust the pH to 9.0-9.5, so that the calcium ions are removed. 2+ The precipitate in the form of CaCO3 is removed; the precipitate at the bottom of the calcium precipitation tank (10) is recovered after centrifugation by a second centrifuge (11) to achieve resource utilization.

[0055] In one possible implementation, the amount of TMT-15 added to the neutralization tank (3) in step S1 is 10 to 100 mg / L.

[0056] In one possible implementation, the amount of carbide slag added to the magnesium precipitation tank (4) in step S2 is 3-6 g / L, and the reaction time is 45-60 min.

[0057] In one possible implementation, in step S3, in the first reaction tank (6), Ca can be released from the carbide slag. 2+ The molar amount of Cl in the wastewater - and SO4 2- The total molar ratio is 2.5:1. The amount of sodium aluminate added is related to the amount of Cl in the solution. - and S04 2- The weighted molar concentration C1 satisfies a molar ratio of 1:1, wherein the weighted molar concentration

[0058] In one possible implementation, in step S4, the calcium carbide slag and Cl in the second reaction tank (8) - The molar ratio of sodium aluminate to Cl is 12:1. - The molar ratio is 2.25:1.

[0059] In one possible implementation, CO2 with a mass fraction of 10-20% is introduced into the calcium precipitation tank (10) in step S5, and the reaction time is 10-20 minutes.

[0060] The technical problem described in this application is solved by the following technical solution.

[0061] A device for dehardening, desulfurization, and dechlorination of high-salinity wastewater using carbide slag, comprising the following components connected in sequence:

[0062] Neutralization tank (3) is used to add carbide slag and TMT-15, and is equipped with pH adjustment and stirring device;

[0063] Magnesium precipitation tank (4) is used to add carbide slag and precipitate Mg. 2+ It is equipped with a stirring system;

[0064] The first reaction tank (6) is used to add carbide slag and sodium aluminate to react and remove SO4. 2- With some Cl - It is equipped with a stirring and reagent dosing device;

[0065] The second reaction tank (8) is used to add carbide slag and sodium aluminate for further removal of Cl. - It is equipped with a stirring and reagent dosing device;

[0066] Calcium precipitation tank (10) is used to introduce CO2 and add Na2CO3 to precipitate Ca. 2+ It is equipped with a CO2 bubbling device, a Na2CO3 dosing system and a pH control device;

[0067] Desulfurization tower (1) is used to receive the supernatant and some precipitate after treatment;

[0068] Fan (2), CO2 bubbling device connected to the outlet of desulfurization tower (1) and calcium precipitation tank (10);

[0069] The solid-liquid separation unit group includes a first plate and frame filter press (5), a first centrifuge (7), a second plate and frame filter press (9), and a second centrifuge (11); wherein:

[0070] The first plate and frame filter press (5) is connected to the bottom sediment outlet of the magnesium sedimentation tank (4);

[0071] The first centrifuge (7) is connected to the bottom sediment outlet of the first reaction tank (6);

[0072] The second plate and frame filter press (9) is connected to the bottom sediment outlet of the second reaction tank (8);

[0073] The second centrifuge (11) is connected to the bottom sediment outlet of the calcium precipitation tank (10).

[0074] In one possible implementation, the supernatant outlet of the magnesium precipitation tank (4) is connected to the desulfurization tower (1) via a pipeline;

[0075] The solid outlet of the first plate and frame filter press (5) is connected to the desulfurization tower (1).

[0076] In one possible implementation, the solid-liquid separation unit group includes:

[0077] The first plate and frame filter press (5) is used to separate magnesium hydroxide precipitate from the magnesium precipitation tank (4);

[0078] The first centrifuge (7) is used to separate the ettringite and Freund's salt precipitate from the first reaction tank (6);

[0079] The second plate and frame filter press (9) is used to separate the Freund's salt precipitate from the second reaction tank (8);

[0080] The second centrifuge (11) is used to separate the calcium carbonate precipitate from the calcium precipitation tank (10).

[0081] In one possible implementation, the blower (2) pressurizes and transports the CO2-containing flue gas from the outlet of the desulfurization tower (1) to the CO2 bubbling device of the calcium precipitation tank (10).

[0082] The principles involved in this application are explained as follows:

[0083] 1. Principle of heavy metal removal:

[0084] Heavy metal ions in high-salinity wastewater can harm the ecological environment and corrode equipment. This application achieves efficient removal of heavy metals through a two-step reaction:

[0085] (1) Alkali precipitation of carbide slag: The carbide slag dissolves and releases OH, causing heavy metals to form hydroxide precipitates. The reaction formula for this process is shown in (1):

[0086] M 2+ +2OH - →M(OH)2↓ (1)

[0087] Where M 2+ Represents heavy metal ions.

[0088] (2) TMT-15 sulfide precipitation: The organic sulfur reagent TMT-15 reacts with residual heavy metal ions to form a more stable sulfide precipitate. The reaction formula for this process is shown in (2):

[0089] M 2+ +(TMT15)→MS↓+(Other products) (2)

[0090] 2. Principle of magnesium ion removal:

[0091] The wastewater after heavy metal removal enters the magnesium precipitation tank, where calcium carbide slag is added to achieve magnesium precipitation. 2+ Remove:

[0092] The main reaction is the formation of magnesium hydroxide precipitate, and the reaction equation for this process is shown in (3):

[0093] Mg 2+ +Ca(OH)₂→Mg(OH)₂↓+Ca 2+ (3)

[0094] At room temperature, Ksp[Mg(OH)2] = 1.2 × 10⁻⁶ -11 < <Ksp[Ca(OH)2]=5.5×10 -6 Ksp is the solubility; therefore, Mg(OH)2 can be removed from wastewater through solid-liquid separation.

[0095] Simultaneous removal of some carbonate and sulfate ions, the reaction equations for this process are shown in (4), (5), and (6):

[0096] HCO 3- +OH - →CO3 2- +H2O (4)

[0097] Ca 2+ +CO3 2- →CaCO3↓ (5)

[0098] Ca 2+ +SO4 2- →CaSO4↓ (6)

[0099] 3. Desulfurization and dechlorination principle:

[0100] (1) Utilizing calcium carbide slag to provide Ca 2+ and OH - Sodium aluminate provides Al 3+ The process involves the stepwise formation of ettringite and Freund's salt.

[0101] Sodium aluminate undergoes hydrolysis, and the reaction equations for this process are shown in (7) and (8):

[0102] 2NaAlO2+4H2O→2Al(OH)3+2NaOH (7)

[0103] Al(OH)3+OH - →Al(OH)4 - (8)

[0104] (2) First stage desulfurization and dechlorination: priority is given to desulfurization, and chlorination is removed simultaneously. SO4 2- Competitive inhibition Cl - Removed, but still produces a small amount of Freund's salt; SO4 2- With Ca 2+ Al(OH)4 - Erythrite (Ca6Al2(SO4)3(OH) is formed. 12 The reaction equation for this process is shown in (9):

[0105] 6Ca 2+ +2Al(OH)4 - +3SO4 2- +4OH - →Ca6Al2(SO4)3(OH) 12 ↓ (9)

[0106] (3) Second stage deep dechlorination: Excessive addition of reagents causes Cl to... - Freund's salt (Ca4Al2Cl2(OH)) is formed. 12 The reaction equation for this process is shown in (10):

[0107] 4Ca 2+ +2Al(OH)4 - +2Cl - +4OH - →Ca4Al2Cl2(OH) 12 ↓ (10)

[0108] 4. Principle of calcium ion removal

[0109] Wastewater containing excessive Ca after deep dechlorination 2+ Carbonization precipitation method is used to remove:

[0110] (1) CO2 acidification and conversion, the reaction equations for this process are shown in (11), (12), and (13):

[0111] CO2 + H2O → H2CO3 (11)

[0112] H2CO3→HCO3 - +H + (12)

[0113] HCO3 - +OH - →CO3 2- +H2O (13)

[0114] (2) CaCO3 precipitate is formed. The reaction equation for this process is shown in (14):

[0115] Ca 2+ +CO3 2- →CaCO3↓ (14)

[0116] (3) Enhanced calcium removal: When CO2 carbonization is insufficient, adding Na2CO3 directly provides CO3. 2- The reaction equation for this process is shown in (15):

[0117] Ca 2+ +Na₂CO₃→CaCO₃↓+2Na + (15)

[0118] Example 2

[0119] This embodiment treats high-salinity wastewater from flue gas desulfurization at an inland thermal power plant. The wastewater contains Ca... 2+ The concentration was 32 mmol / L (1282.56 mg / L), Mg 2+ The concentration was 23.9 mmol / L (581.01 mg / L), SO4 2- The concentration was 11143 mg / L, Cl - The concentration was 8792 mg / L. [Using...] Figure 1 The process flow shown includes a neutralization tank (3), a magnesium precipitation tank (4), a first reaction tank (6), a second reaction tank (8), a calcium precipitation tank (10) connected in sequence, and a first plate and frame filter press (5), a first centrifuge (7), a second plate and frame filter press (9), and a second centrifuge (11).

[0120] The specific processing procedure is as follows:

[0121] Heavy metal removal: High-salt wastewater is introduced into a neutralization tank (3), and carbide slag and TMT-15 are added. The dosage of TMT-15 is 50 mg / L. The pH is adjusted to 9.2, and the reaction removes heavy metal impurities.

[0122] Magnesium ion removal: The supernatant of the neutralization tank (3) is introduced into the magnesium precipitation tank (4), and calcium carbide slag is added. The amount of calcium carbide slag added is 4g / L. The pH is adjusted to 12.3, mechanically stirred and allowed to settle for 1h.

[0123] Mg after treatment 2+ The concentration was reduced to 0.024 mmol / L, with a removal rate of 99.9%. The mixed precipitate containing Mg(OH)2 at the bottom was dehydrated by the first plate and frame filter press (5), and the resulting solid was returned to the desulfurization tower (1) for reuse.

[0124] First stage desulfurization and dechlorination: The supernatant from the magnesium precipitation tank (4) is diluted 10 times and then enters the first reaction tank (6). Calcium carbide slag is added, and Ca can be released from the calcium carbide slag. 2+ The molar amount of Cl in the wastewater - and SO4 2- The total molar ratio is 2.5:1, with sodium aluminate reacting with Cl in the solution. - and SO4 2- The overall molar concentration (CCl) - +2 / 3CSO4 2- Add according to a 1:1 ratio;

[0125] After mechanical stirring and standing for 1 hour to settle, SO4 2- The concentration was reduced to 16.6 mg / L, with a removal rate of 99.9%.

[0126] The bottom calcite precipitate is dehydrated by the first centrifuge (7) and then recovered for use in the preparation of adsorbents.

[0127] Second stage dechlorination:

[0128] The supernatant from the first reaction tank (6) enters the second reaction tank (8), where calcium carbide slag and sodium aluminate are added. The calcium carbide slag reacts with Cl... - The molar ratio of sodium aluminate to Cl is 8-14:1. - The molar ratio is 2-2.25:1;

[0129] After mechanical stirring and standing for 1 hour to settle, Cl - The concentration decreased to 165.2 mg / L, with a removal rate of 81.21%.

[0130] The bottom Freund's salt precipitate is recovered after being dehydrated by the second plate and frame filter press (9) and used to prepare ion exchangers.

[0131] Calcium ion removal:

[0132] The supernatant from the second reaction tank (8) enters the calcium precipitation tank (10), and is then introduced with 15% CO2 gas via a blower (2) from the outlet of the desulfurization tower (1) to adjust the pH to 9.2. Na2CO3 is then added to remove residual Ca. 2+ ;

[0133] The CaCO3 precipitate at the bottom is dehydrated by a second centrifuge (11) and then utilized as a resource.

[0134] See processing results Figures 2-5 .

[0135] The water quality of each unit's effluent was sampled and tested, as shown in Table 1:

[0136] Table 1. Water quality changes in each treatment unit of the high-salinity wastewater desulfurization and dechlorination process.

[0137]

[0138] As shown in Table 1, the final Ca 2+ Removal rate 99%; Mg 2+ Removal rate 99.9%; SO4 2- Removal rate 99.9%; Cl - The overall removal rate was 81.21%.

[0139] The beneficial effects of using the embodiments of this application are as follows:

[0140] (1) This application utilizes the alkaline conditions provided by carbide slag in a neutralization tank in conjunction with TMT-15 organic sulfur reagent to achieve synergistic precipitation and removal of heavy metal ions from high-salt wastewater. This combination effectively reduces heavy metal residues, minimizes the corrosion risk of subsequent treatment systems, and improves the stability and safety of the overall treatment process.

[0141] (2) In the magnesium precipitation tank, the effective components in the carbide slag are used to react with the Mg in the wastewater. 2+ The reaction produces magnesium hydroxide precipitate, which, combined with plate and frame filtration, achieves solid-liquid separation, significantly reducing the Mg content in wastewater. 2+ Concentration, to provide stable water quality conditions for subsequent reactions.

[0142] (3) This application employs a synergistic reaction of carbide slag and sodium aluminate to promote SO4 in the first reaction tank. 2- With Ca 2+ Al 3 + The formation of stable ettringite precipitate can effectively reduce the sulfate concentration in wastewater, improve water quality, and ensure that the subsequent dechlorination effect is not inhibited.

[0143] (4) Part of Cl can be removed simultaneously in the first stage reaction. -The second stage involves adding excessive amounts of calcium carbide slag and sodium aluminate to form Freund's salt, effectively removing Cl from the wastewater. - This phased strategy can significantly reduce Cl - The concentration can reduce the risk of corrosion to equipment and extend the service life of the system.

[0144] (5) In this application, the CO2-containing exhaust gas recovered by the blower is introduced into the calcium precipitation tank, and Na2CO3 is selectively added to promote the precipitation of calcium under controlled pH conditions. 2+ Removed by precipitation in the form of calcium carbonate, avoiding Ca in the system. 2+ Enrichment improves effluent quality and reduces the risk of scaling.

[0145] (6) The precipitates such as magnesium hydroxide, ettringite, Freund’s salt and calcium carbonate generated during the treatment process can be used as desulfurizing agents, adsorbents or ion exchange materials, respectively, to achieve the synergistic treatment of wastewater and solid waste, reduce secondary pollution and have good comprehensive resource utilization value.

[0146] (7) The device structure and treatment method proposed in this application are highly consistent. All units in the system, including the stirring device, the reagent dosing system, the CO2 bubbling unit, the pH adjustment system and the solid-liquid separation equipment, are coordinated and cooperated, which is convenient to implement in engineering practice. The system has strong stability and is easy to operate.

[0147] (8) Through actual treatment experiments on high-salinity wastewater from typical thermal power plants, the results show that Ca 2+ Mg 2+ SO4 2- and Cl - The removal rates of major pollutants reached 99%, 99.9%, 99.9% and 81.21% respectively, demonstrating significant treatment effects and meeting the technical requirements for recycling or achieving emission standards. This indicates that the proposed solution has good application prospects.

[0148] In the embodiments provided in this application, it should be understood that the disclosed systems, modules, and methods can be implemented in other ways. For example, the module embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces, or indirect coupling or communication connection between modules or units, and may be electrical, mechanical, or other forms.

[0149] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit it. This application is not limited to the exact structures described above and illustrated in the accompanying drawings, and it should not be considered that the specific implementation of this application is limited to these descriptions. For those skilled in the art, various changes and modifications made without departing from the concept of this application should be considered to fall within the protection scope of this application.

Claims

1. A device for dehardening, desulfurizing, and dechlorinating high-salinity wastewater using carbide slag, characterized in that, Including those connected sequentially: The neutralization tank is used to add carbide slag and TMT-15. It is equipped with a pH adjustment and stirring device to adjust the pH value to 9.0-9.5 in order to remove heavy metal ions from the wastewater. Magnesium precipitation tank, used for adding carbide slag and precipitating Mg. 2+ It is equipped with a stirring system to adjust the pH value to 11.0–12.5, so that Mg… 2+ The precipitate, in the form of magnesium hydroxide, was removed; The first reaction tank is used to add carbide slag and sodium aluminate to remove SO4. 2- With some Cl - It is equipped with a stirring and reagent dosing device to control the pH value between 11.5 and 13.5, so that SO42- can be controlled. 2- With Ca 2+ Al 3+ The reaction produces ettringite precipitate and removes some Cl. - The second reaction tank is used to add carbide slag and sodium aluminate for further removal of Cl. - It is equipped with a stirring and reagent dosing device, and the pH value is controlled at 11.5–13.5 to allow Cl to form. - With Ca 2+ Al 3+ The reaction produces Freund's salt precipitate; Calcium precipitation tank, used to introduce CO2 and add Na2CO3 to precipitate Ca. 2+ It is equipped with a CO2 bubbling device, a Na2CO3 dosing system, and a pH control device to adjust the pH to 9.0–9.5, so that Ca... 2+ The precipitate, in the form of calcium carbonate, is removed; Desulfurization towers are used to receive the supernatant and some precipitates after treatment. A blower, a CO2 bubbling device connecting the desulfurization tower outlet to the calcium precipitation tank; The solid-liquid separation unit group includes a first plate and frame filter press, a first centrifuge, a second plate and frame filter press, and a second centrifuge; wherein: The first plate and frame filter press is connected to the bottom sediment outlet of the magnesium sedimentation tank; The first centrifuge is connected to the sediment outlet at the bottom of the first reaction tank; The second plate and frame filter press is connected to the bottom sediment outlet of the second reaction tank; The second centrifuge is connected to the bottom sediment outlet of the calcium precipitation tank.

2. The device for dehardening, desulfurization, and dechlorination of high-salinity wastewater using carbide slag according to claim 1, characterized in that, The supernatant outlet of the magnesium precipitation tank is connected to the desulfurization tower via a pipeline; The outlet of the first plate and frame filter press is connected to the desulfurization tower.

3. The device for dehardening, desulfurization, and dechlorination of high-salinity wastewater using carbide slag according to claim 1, characterized in that, In the solid-liquid separation unit group: The first plate and frame filter press is used to separate magnesium hydroxide precipitate from the magnesium precipitation tank; The first centrifuge is used to separate ettringite and Freund's salt precipitate from the first reaction tank; The second plate and frame filter press is used to separate the Freund's salt precipitate from the second reaction tank; The second centrifuge is used to separate calcium carbonate precipitate from the calcium precipitation tank.

4. The device for dehardening, desulfurization, and dechlorination of high-salinity wastewater using carbide slag according to claim 1, characterized in that, The blower pressurizes and transports the CO2-containing flue gas from the desulfurization tower outlet to the CO2 bubbling device in the calcium precipitation tank.

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