Method and device for hardness removal, desulfurization and dechlorination of high-salinity wastewater by using carbide slag

Abstract

The invention relates to a method and a device for hardness removal, desulfurization and dechlorination of high-salinity wastewater by using carbide slag, and belongs to the technical field of industrial wastewater treatment. The method comprises the steps of heavy metal removal, magnesium ion removal, two-stage desulfurization and dechlorination, calcium ion removal and the like, heavy metals, Mg < 2 + >, SO4 < 2->, Cl <-> and Ca < 2 + > in the wastewater are sequentially and efficiently removed, and generated precipitates are subjected to solid-liquid separation and then partially reused for desulfurization. The device comprises a neutralization tank, a magnesium sedimentation tank, a first reaction tank, a second reaction tank, a calcium sedimentation tank, a desulfurization tower, a fan and a multi-stage solid-liquid separation unit, and is compact in structure and clear in division of labor. According to the method, carbide slag solid waste resources are fully utilized, the treatment efficiency is high, the operation cost is low, by-products can be recycled, and the method has good engineering adaptability and economic and environmental benefits.

Description

Technical Field

[0001] The present application relates to the technical field of industrial wastewater treatment, and in particular to a method and device for removing hardness, desulfurization and dechlorination of high-salt wastewater using carbide slag. Background Art

[0002] As environmental protection standards become increasingly stringent, industrial enterprises have put forward higher requirements for achieving near-zero discharge of high-salinity wastewater. High-salinity wastewater, represented by power plants and chemical industries, usually contains a large amount of Ca 2+ Mg 2+ 、SO4 2- With Cl - Plasma components not only lead to high water hardness, but may also cause serious scaling and corrosion in subsequent membrane treatment and thermal concentration processes, affecting equipment operation stability and reuse efficiency.

[0003] Currently, a variety of hardness removal and desalination technologies have been proposed. For example, Chinese invention patent publication number CN119143314A provides a hardness removal method that combines sodium carbonate solution and magnesium chloride solution. This method can effectively precipitate calcium ions, but the removal efficiency of magnesium ions is limited. Moreover, although magnesium chloride can accelerate the formation of calcium sulfate precipitation under alkaline conditions, the problem of incomplete precipitation still exists. In addition, the formed magnesium carbonate colloid interferes with the ion reaction process, and the precipitate is difficult to separate or recover, making it difficult to apply to complex wastewater systems with high load and high hardness.

[0004] In order to reduce the treatment cost, Chinese patent CN117700017A attempts to use low-cost sodium sulfate to replace part of sodium carbonate to achieve the removal of calcium ions. Although it has certain economic benefits, it is limited to removing hardness and still cannot effectively remove SO4 2- and Cl - Plasma components. In high-salt wastewater, the presence of such anions will severely limit the wastewater concentration multiple and reuse depth.

[0005] For SO4 2- and Cl - The current technology mainly relies on membrane concentration + evaporation crystallization route, but this process has high investment and high energy consumption, which limits its promotion on an industrial scale. In addition, although ion exchange and electrochemical technology can remove SO4 2- and Cl - , but there are problems such as high operating costs and frequent replacement of resins or electrodes.

[0006] In recent years, studies have proposed the “ultra-high lime aluminum method” for the removal of Cl - Such as patent CN112429877A, which adds sodium aluminate and reacts with Ca(OH)2 under high pH conditions to form Freund's salt precipitation to achieve the removal of chloride ions. However, this method has the problem of insufficient sulfate pretreatment, SO42- The residue will significantly inhibit the subsequent chloride ion precipitation reaction. In addition, most of these methods use conventional reagents such as lime and sodium carbonate, which are still costly and difficult to recycle the precipitate.

[0007] In order to solve the above problems, the present invention optimizes and upgrades the traditional double alkali method, and proposes a method and device for overall de-hardening, desulfurization and dechlorination of high-salt wastewater using an ultra-high lime aluminum method using carbide slag. This method removes key pollutants such as heavy metals, magnesium ions, sulfate, chloride ions and calcium ions in sequence through a graded reaction method. During the reaction process, carbide slag is used to replace traditional lime, which greatly reduces the processing cost; a two-stage carbide slag-sodium aluminate reaction unit is introduced to make SO4 2- With Cl - Calcium aluminate and Freund's salt precipitates are formed respectively, effectively avoiding reaction inhibition. CO2 gas is introduced at the end, supplemented by Na2CO3 regulation, to achieve complete removal of calcium ions, while reducing the system pH and conductivity, reducing the burden of subsequent treatment. This method also achieves solid-liquid separation through plate and frame filter pressing or centrifugation. The produced Calcium aluminate and Freund's salt precipitates can be used as components of cementitious materials or for stabilization of heavy metal / salt pollutants. It has good economic and environmental performance and is particularly suitable for deep treatment of high-salt wastewater and zero-emission transformation in power plants, coal chemical industry and other fields. Summary of the Invention

[0008] In view of the above problems, the present application provides a method and device for removing hardness, desulfurization and dechlorination of high-salt wastewater using carbide slag, which can solve the problems of high reagent cost, fragmentation of hardness removal, desulfurization and dechlorination process, SO4 2- 、Cl - To address the problems of low removal rate and difficulty in resource utilization of sediments, this application takes into account both technical economy and engineering feasibility, and is suitable for deep treatment of wastewater and near-zero emission scenarios in power plants, coal chemical industry and other industries.

[0009] To achieve the purpose of this application, this application provides the following technical solutions:

[0010] In a first aspect, the present application provides a method for removing hardness, desulfurization and dechlorination of high-salt wastewater using carbide slag, comprising the following steps:

[0011] S1. Heavy metal removal: The high-salt wastewater is introduced into the neutralization tank, carbide slag and TMT-15 are added, and the pH value is adjusted to 9.0-9.5 to remove heavy metal ions in the wastewater;

[0012] S2, magnesium ion removal: the neutralized wastewater is introduced into the magnesium precipitation tank, and calcium carbide slag is added to adjust the pH value to 11.0-12.5 to make the Mg 2+ It is removed as a precipitate of magnesium hydroxide;

[0013] S3, the first stage of desulfurization and dechlorination: the supernatant of the magnesium precipitation tank is introduced into the first reaction tank, carbide slag and sodium aluminate are added, and the pH value is controlled at 11.5-13.5 to make SO4 2- With Ca 2+ 、Al 3+ The reaction generates ettringite precipitation and removes part of the Cl - ;

[0014] S4, the second stage of dechlorination: the effluent from the first reaction tank is introduced into the second reaction tank, and calcium carbide slag and sodium metaaluminate are continuously added to control the pH value to 11.5-13.5, so that Cl - With Ca 2+ 、Al 3+ The reaction generates a precipitate of Freund's salt;

[0015] S5. Calcium ion removal: The effluent from the second reaction tank is introduced into the calcium precipitation tank, CO2 gas is introduced and Na2CO3 is selectively added, and the pH is adjusted to 9.0-9.5 to make Ca 2+ It is removed as a precipitate of calcium carbonate;

[0016] S6. Solid-liquid separation unit group: The precipitates produced in each step are separated into solid and liquid through a plate and frame filter press or a centrifuge, and the obtained solids are used in the desulfurization process or resource utilization.

[0017] In a possible implementation, the amount of TMT-15 added to the neutralization tank in step S1 is 10 to 100 mg / L.

[0018] In a possible implementation, the dosage of carbide slag in the magnesium precipitation tank in step S2 is 3-6 g / L, and the reaction time is 45-60 min.

[0019] In a possible implementation, in step S3, in the first reaction tank, the carbide slag can release Ca 2+ The molar amount of Cl in wastewater - and SO4 2- The molar ratio of the total molar amount is 2.5:1, and the amount of sodium metaaluminate added is proportional to the amount of Cl in the solution. - and SO4 2- The weighted molar concentration C1 satisfies the molar ratio of 1:1, and the weighted molar concentration

[0020] In a possible implementation, in step S4, the carbide slag and Cl in the second reaction tank - The molar ratio of sodium metaaluminate and Cl is 8-14:1. - The molar ratio is 2-2.25:1.

[0021] In a possible implementation, in step S5, CO2 with a mass fraction of 10 to 20% is introduced into the calcium precipitation tank, and the reaction time is 10 to 20 minutes.

[0022] In a second aspect, the present application provides a high-salinity wastewater desulfurization and dechlorination device using carbide slag, comprising:

[0023] Neutralization tank, used for adding carbide slag and TMT-15, equipped with pH adjustment and stirring device;

[0024] Magnesium precipitation tank, used to add calcium carbide slag and precipitate Mg 2+ , equipped with a stirring system;

[0025] The first reaction tank is used to add carbide slag and sodium aluminate to react and remove SO4 2- With some Cl - , equipped with stirring and chemical dosing devices;

[0026] The second reaction tank is used to add calcium carbide slag and sodium aluminate to further remove Cl - , equipped with stirring and chemical dosing devices;

[0027] Calcium precipitation tank, used to introduce CO2 and add Na2CO3 to precipitate Ca 2+ , equipped with CO2 bubbling device, Na2CO3 dosing system and pH control device;

[0028] Desulfurization tower, used to receive the treated supernatant and part of the sediment;

[0029] Fan, CO2 bubbling device connecting the desulfurization tower outlet and the calcium precipitation tank;

[0030] a solid-liquid separation unit group, comprising a first plate-frame filter press, a first centrifuge, a second plate-frame filter press, and a second centrifuge;

[0031] in:

[0032] The first plate and frame filter press is connected to the sediment outlet at the bottom of the magnesium precipitation tank;

[0033] The first centrifuge is connected to the sediment outlet at the bottom of the first reaction tank;

[0034] The second plate-and-frame filter press is connected to the sediment outlet at the bottom of the second reaction tank;

[0035] The second centrifuge is connected to the sediment outlet at the bottom of the calcium precipitation tank.

[0036] In a possible implementation, the supernatant outlet of the magnesium precipitation tank is connected to a desulfurization tower via a pipeline;

[0037] The outlet of the first plate and frame filter press is connected to a desulfurization tower.

[0038] In a possible implementation, in the solid-liquid separation unit group:

[0039] The first plate and frame filter press is used to separate magnesium hydroxide precipitates from the magnesium precipitation tank;

[0040] The first centrifuge is used to separate the ettringite and Freund's salt precipitates in the first reaction tank;

[0041] The second plate and frame filter press is used to separate the Freund's salt precipitate in the second reaction tank;

[0042] The second centrifuge is used to separate calcium carbonate precipitates from the calcium precipitation tank.

[0043] In a possible implementation, the blower pressurizes and transports the CO2-containing flue gas at the outlet of the desulfurization tower to the CO2 bubbling device of the calcium precipitation tank.

[0044] Beneficial effects:

[0045] (1) The present invention uses carbide slag as the main alkaline neutralizer and calcium source to replace traditional chemical reagents, which not only reduces the processing cost but also realizes the resource utilization of solid waste, and has good environmental protection and economic benefits.

[0046] (2) The present invention removes heavy metals, Mg and Mg in high-salt wastewater step by step through a multi-stage reaction system. 2+ 、SO4 2- 、Cl - and Ca 2+ The conditions at each stage are optimized, the removal efficiency is high, and the final effluent water quality is greatly improved, which is suitable for recycling or standard emission in the desulfurization system.

[0047] (3) The present invention adds carbide slag and sodium aluminate in two stages through a two-stage reaction pool, and synergistically generates Freund's salt under alkaline conditions, which effectively solves the problem of Cl - It is difficult to remove the problem and avoid the risk of corrosion to the subsequent desulfurization system.

[0048] (4) The present invention sets up a calcium precipitation tank to introduce CO2 gas and Na2CO3 to selectively react, effectively removing Ca 2+ At the same time, the fan is used to recover and reuse the CO2 tail gas at the outlet of the desulfurization tower to reduce carbon emissions, reflecting the characteristics of green and low-carbon technology.

[0049] (5) The process method of the present invention corresponds closely to the device structure, the reaction unit, the dosing system and the solid-liquid separation equipment are reasonably coordinated, the process continuity is good, and it is convenient for layout, operation and maintenance in actual engineering.

[0050] (6) The device described in the present invention is configured with corresponding equipment according to the processing functions of each stage, such as a stirring device, a pH control system, a bubbling system and a multi-channel solid-liquid separation unit, which can flexibly adapt to different salt-type wastewaters and processing volume requirements, and has strong engineering adaptability.

[0051] (7) The solid products such as magnesium hydroxide, ettringite, Freund's salt, and calcium carbonate generated by the present invention can be reused in the desulfurization process or further utilized as resources after solid-liquid separation, thereby improving the comprehensive resource utilization efficiency of the entire system. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] The accompanying drawings are used to provide a further understanding of the present application and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the present application and do not constitute a limitation of the present application.

[0053] Figure 1 A schematic diagram of a process flow of a method and apparatus for removing hardness, desulfurization, and dechlorination from high-salt wastewater using carbide slag provided in an embodiment of the present application;

[0054] Figure 2 A schematic diagram showing the change in solution hardness with carbide slag dosage in a magnesium precipitation tank according to an embodiment of the present application;

[0055] Figure 3 Schematic diagram of the change of solution pH in the magnesium precipitation tank with the amount of carbide slag added provided in the embodiment of the present application;

[0056] Figure 4 The SO4 in the first reaction tank provided in the embodiment of the present application 2- Schematic diagram of removal rate changes;

[0057] Figure 5 The Cl in the second reaction tank provided in the embodiment of the present application - Schematic diagram of removal rate changes.

[0058] Among them, 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 DESCRIPTION

[0059] To make the objectives, technical solutions, and advantages of this application more clear, the technical solutions of this application will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments of this application, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of this application.

[0060] 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 quantity of the technical features indicated. Thus, features specified as "first" or "second" may explicitly or implicitly include one or more of such features; and in the description of this application, unless otherwise specified, "plurality" means two or more.

[0061] Example 1

[0062] Figure 1 The process flow of a method for removing hardness, desulfurization and dechlorination of high-salt wastewater using carbide slag provided in an embodiment of the present application includes the following steps:

[0063] S1. Heavy metal removal: The high-salt wastewater is introduced into the neutralization tank (3), carbide slag and TMT-15 are added, and the pH value is adjusted to 9.0-9.5 to remove heavy metal ions in the wastewater;

[0064] S2, magnesium ion removal: the neutralized wastewater is introduced into the magnesium precipitation tank (4), and calcium carbide slag is continuously added to adjust the pH value to 11.0-12.5 to make Mg 2+ The magnesium hydroxide precipitate is removed; the mixed precipitate containing magnesium hydroxide at the bottom of the magnesium precipitation tank (4) is filtered through the first plate and frame filter press (5) and then returned to the desulfurization tower (1) for desulfurization;

[0065] S3, the first stage of desulfurization and dechlorination: the supernatant of the magnesium precipitation tank (4) is diluted 10 times and then introduced into the first reaction tank (6), carbide slag and sodium aluminate are added, and the pH value is controlled to be 11.5-13.5, so that SO4 2- With Ca 2+ 、Al 3+ The reaction generates ettringite precipitation and removes part of the Cl - The sediment at the bottom of the first reaction tank (6) is dehydrated by the first centrifuge (7) and then discharged;

[0066] S4, the second stage of dechlorination: the effluent from the first reaction tank (6) is introduced into the second reaction tank (8), and calcium carbide slag and sodium metaaluminate are continuously added to control the pH value to 11.5-13.5, so that Cl - With Ca 2+ 、Al 3+ The reaction generates a Freund's salt precipitate; the precipitate at the bottom of the second reaction tank (8) is filtered through a second plate-and-frame filter press (9) and then discharged;

[0067] 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, and the pH is adjusted to 9.0-9.5 to make Ca 2+The precipitate is removed in the form of CaCO3; the precipitate at the bottom of the calcium precipitation tank (10) is recovered after centrifugation in the second centrifuge (11) to achieve resource utilization.

[0068] In one possible embodiment, the amount of TMT-15 added to the neutralization tank (3) in step S1 is 10 to 100 mg / L.

[0069] In a possible embodiment, the dosage of carbide slag in the magnesium precipitation tank (4) in step S2 is 3-6 g / L, and the reaction time is 45-60 min.

[0070] In a possible embodiment, in the first reaction tank (6) of step S3, the calcium carbide slag can release Ca 2+ The molar amount of Cl in wastewater - and SO4 2- The molar ratio of the total molar amount is 2.5:1, and the amount of sodium metaaluminate added is proportional to the amount of Cl in the solution. - and SO4 2- The weighted molar concentration C1 satisfies the molar ratio of 1:1, and the weighted molar concentration

[0071] In one possible embodiment, in step S4, the carbide slag and Cl in the second reaction tank (8) - The molar ratio of sodium aluminate to Cl is 12:1, and the molar ratio of sodium metaaluminate to Cl is 2.25:1.

[0072] In a possible embodiment, in step S5, CO2 with a mass fraction of 10 to 20% is introduced into the calcium precipitation tank (10), and the reaction time is 10 to 20 minutes.

[0073] The technical problem of the present invention is achieved by the following technical solutions.

[0074] A device for removing hardness, desulfurization and dechlorination of high-salt wastewater using carbide slag, comprising:

[0075] Neutralization tank (3), used for adding calcium carbide slag and TMT-15, equipped with pH adjustment and stirring device;

[0076] Magnesium precipitation tank (4), used to add calcium carbide slag and precipitate Mg 2+ , equipped with a stirring system;

[0077] The first reaction tank (6) is used to add calcium carbide slag and sodium aluminate to react and remove SO4 2- With some Cl - , equipped with stirring and chemical dosing devices;

[0078] The second reaction tank (8) is used to add calcium carbide slag and sodium aluminate to further remove Cl -, equipped with stirring and chemical dosing devices;

[0079] Calcium precipitation tank (10), used to introduce CO2 and add Na2CO3 to precipitate Ca 2+ , equipped with CO2 bubbling device, Na2CO3 dosing system and pH control device;

[0080] A desulfurization tower (1) is used to receive the treated supernatant and part of the precipitate;

[0081] A blower (2) is connected to the outlet of the desulfurization tower (1) and the CO2 bubbling device of the calcium precipitation tank (10);

[0082] The solid-liquid separation unit group comprises a first plate-frame filter press (5), a first centrifuge (7), a second plate-frame filter press (9) and a second centrifuge (11); wherein:

[0083] The first plate-and-frame filter press (5) is connected to the sediment outlet at the bottom of the magnesium precipitation tank (4);

[0084] The first centrifuge (7) is connected to the sediment outlet at the bottom of the first reaction tank (6);

[0085] The second plate-and-frame filter press (9) is connected to the sediment outlet at the bottom of the second reaction tank (8);

[0086] The second centrifuge (11) is connected to the sediment outlet at the bottom of the calcium precipitation tank (10).

[0087] In one possible embodiment, the supernatant outlet of the magnesium precipitation tank (4) is connected to the desulfurization tower (1) via a pipeline;

[0088] The solid outlet of the first plate and frame filter press (5) is connected to the desulfurization tower (1).

[0089] In a possible embodiment, in the solid-liquid separation unit group:

[0090] The first plate and frame filter press (5) is used to separate magnesium hydroxide precipitates in the magnesium precipitation tank (4);

[0091] The first centrifuge (7) is used to separate the ettringite and Freund's salt precipitates in the first reaction tank (6);

[0092] The second plate and frame filter press (9) is used to separate the Freund's salt precipitate in the second reaction tank (8);

[0093] The second centrifuge (11) is used to separate calcium carbonate precipitates in the calcium precipitation tank (10).

[0094] In a possible embodiment, the blower (2) pressurizes and transports the CO2-containing flue gas at the outlet of the desulfurization tower (1) to the CO2 bubbling device of the calcium precipitation tank (10).

[0095] The principle of the present invention is introduced as follows:

[0096] 1. Principle of heavy metal removal:

[0097] Heavy metal ions in high-salt wastewater can harm the ecological environment and corrode equipment. This invention achieves efficient removal of heavy metals through a two-step reaction:

[0098] (1) Alkali precipitation of carbide slag: The carbide slag dissolves and releases OH, causing heavy metals to form hydroxide precipitation. The reaction formula of this process is shown in (1):

[0099] M 2+ +2OH - -→M(OH)2↓(1)

[0100] Among them, M 2+ Represents heavy metal ions.

[0101] (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 equation for this process is shown in (2):

[0102] M 2+ +(TMT15)→MS↓+(other products) (2)

[0103] 2. Principle of magnesium ion removal:

[0104] The wastewater after heavy metal removal enters the magnesium precipitation tank, and calcium carbide slag is added to achieve Mg 2+ Removal:

[0105] The main reaction is to generate magnesium hydroxide precipitation. The reaction formula of this process is shown in (3):

[0106] Mg 2+ +Ca(OH)2→Mg(OH)2↓+Ca 2+ (3)

[0107] At room temperature, Ksp[Mg(OH)2]=1.2×10 -11 <<Ksp[Ca(OH)2]=5.5×10 -6 , Ksp is the solubility; therefore Mg(OH)2 can be removed from wastewater by solid-liquid separation.

[0108] Part of the carbonate and sulfate radicals are removed simultaneously. The reaction equations of this process are shown in (4), (5), and (6):

[0109] HCO 3- +OH - →CO3 2- +H2O (4)

[0110] Ca 2+ +CO3 2- →CaCO3↓ (5)

[0111] Ca 2+ +SO4 2- →CaSO4↓ (6)

[0112] 3. Principle of desulfurization and dechlorination:

[0113] (1) Using carbide slag to provide Ca 2+ and OH - , sodium aluminate provides Al 3+ , generating ettringite and Freund's salt in steps:

[0114] Sodium metaaluminate is hydrolyzed. The reaction equations of this process are shown in (7) and (8):

[0115] 2NaAlO2+4H2O→2Al(OH)3+2NaOH (7)

[0116] Al(OH)3+OH - →Al(OH)4 - (8)

[0117] (2) The first stage of desulfurization and dechlorination: priority removal of sulfur, simultaneous removal of chlorine, SO4 2- Competitive inhibition of Cl - Removed, but still produces a small amount of Freund's salt; SO4 2- With Ca 2+ 、Al(OH)4 - Formation of ettringite (Ca6Al2(SO4)3(OH) 12 ), the reaction equation of this process is shown in (9):

[0118] 6Ca 2+ +2Al(OH)4 - +3SO4 2- +4OH - →Ca6Al2(SO4)3(OH) 12 ↓ (9)

[0119] (3) Second stage deep dechlorination: excessive addition of reagents to make Cl - Generate Freund's salt (Ca4Al2Cl2(OH) 12 ), the reaction equation of this process is shown in (10):

[0120] 4Ca2+ +2Al(OH)4 - +2Cl - +4OH - →Ca4Al2Cl2(OH) 12 ↓ (10)

[0121] 4. Principle of calcium ion removal

[0122] Excessive Ca in wastewater after deep dechlorination 2+ , using carbonization precipitation removal:

[0123] (1) CO2 acidification conversion. The reaction equations of this process are shown in (11), (12), and (13):

[0124] CO2+H2O→H2CO3 (11)

[0125] H2CO3→HCO3 - +H + (12)

[0126] HCO3 - +OH - →CO3 2- +H2O (13)

[0127] (2) CaCO3 precipitation is generated. The reaction equation of this process is shown in (14):

[0128] Ca 2+ +CO3 2- →CaCO3↓ (14)

[0129] (3) Enhanced decalcification: When CO2 carbonization is insufficient, add Na2CO3 to directly provide CO3 2- , the reaction equation of this process is shown in (15):

[0130] Ca 2+ +Na2CO3→CaCO3↓+2Na + (15)

[0131] Example 2

[0132] This example treats the high-salt wastewater from flue gas desulfurization of an inland thermal power plant. 2+ The concentration is 32mmol / L (1282.56mg / L), Mg 2+ The concentration is 23.9mmol / L (581.01mg / L), SO4 2- The concentration is 11143 mg / L, Cl - The concentration is 8792mg / L. Figure 1The 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), and a matching first plate and frame filter press (5), a first centrifuge (7), a second plate and frame filter press (9), and a second centrifuge (11).

[0133] The specific processing process is as follows:

[0134] Heavy metal removal: The high-salt wastewater is passed into the neutralization tank (3), and calcium carbide slag and TMT-15 are added. The dosage of TMT-15 is 50 mg / L, and the pH is adjusted to 9.2. The reaction removes heavy metal impurities.

[0135] Removal of magnesium ions: The supernatant from the neutralization tank (3) is introduced into the magnesium precipitation tank (4), where carbide slag is added at a dosage of 4 g / L. The pH is adjusted to 12.3, mechanically stirred, and allowed to settle for 1 hour.

[0136] Mg after treatment 2+ The concentration is reduced to 0.024 mmol / L, and the removal rate is 99.9%. The mixed precipitate containing Mg(OH)2 at the bottom is filtered and dehydrated by the first plate and frame filter press (5), and the obtained solid is returned to the desulfurization tower (1) for reuse.

[0137] The first stage of desulfurization and dechlorination: the supernatant of the magnesium precipitation tank (4) is diluted 10 times and then enters the first reaction tank (6), where calcium carbide slag is added. The calcium carbide slag can release Ca 2+ The molar amount of Cl in wastewater - and SO4 2- The molar ratio of the total molar amount is 2.5:1, and the sodium metaaluminate and Cl in the solution - and SO4 2- The comprehensive molar concentration (CCl - +2 / 3CSO4 2- ) Add in a 1:1 ratio;

[0138] After mechanical stirring and settling for 1 hour, SO4 2- The concentration dropped to 16.6 mg / L, with a removal rate of 99.9%;

[0139] The ettringite precipitate at the bottom is dehydrated by the first centrifuge (7) and recovered for use in preparing an adsorbent.

[0140] Second stage dechlorination:

[0141] The supernatant of the first reaction tank (6) enters the second reaction tank (8), and is supplemented with carbide slag and sodium aluminate, wherein the carbide slag and Cl - The molar ratio of sodium metaaluminate and Cl is 8-14:1. - The molar ratio is 2-2.25:1;

[0142] After mechanical stirring and settling for 1 hour, Cl - The concentration dropped to 165.2 mg / L, with a removal rate of 81.21%;

[0143] The Freund's salt precipitate at the bottom is filtered and dehydrated by a second plate and frame filter press (9) and then recovered for use in preparing an ion exchanger.

[0144] Calcium ion removal:

[0145] The supernatant of the second reaction tank (8) enters the calcium precipitation tank (10), and is fed into the desulfurization tower (1) outlet through the blower (2) with a mass fraction of 15% CO2 gas, and the pH is adjusted to 9.2. Na2CO3 is added to remove residual Ca 2+ ;

[0146] The CaCO3 precipitate at the bottom is dehydrated by the second centrifuge (11) and then recycled.

[0147] Treatment effect see Figure 2-Figure 5 .

[0148] The water quality of each unit was sampled and tested as shown in Table 1:

[0149] Table 1 Water quality changes in each treatment unit of high-salt wastewater desulfurization and dechlorination process

[0150]

[0151] From Table 1, we can see that the final Ca 2+ Removal rate 99%; Mg 2+ Removal rate 99.9%; SO4 2- Removal rate 99.9%; Cl - The total removal rate is 81.21%.

[0152] The beneficial effects of the embodiments of the present application are as follows:

[0153] (1) The present invention utilizes the alkaline conditions provided by carbide slag in a neutralization tank in conjunction with the TMT-15 organic sulfur reagent to achieve synergistic precipitation and removal of heavy metal ions from high-salinity wastewater. This combination effectively reduces heavy metal residues, mitigates the corrosion risk of subsequent treatment systems, and improves the stability and safety of the overall treatment process.

[0154] (2) Utilization of effective components in carbide slag and Mg in wastewater in magnesium precipitation tank 2+ The reaction generates magnesium hydroxide precipitate, which can be combined with plate and frame filter press to achieve solid-liquid separation, which can significantly reduce the Mg content in wastewater. 2+ concentration, providing stable water quality conditions for subsequent reactions.

[0155] (3) The present invention adopts the synergistic reaction of carbide slag and sodium aluminate to promote SO42- 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.

[0156] (4) Part of Cl can be removed simultaneously in the first stage reaction - In the second stage, excessive carbide slag and sodium aluminate are added to form Freund's salt, which effectively removes Cl from the wastewater. - This phased strategy can significantly reduce Cl - concentration, reduce the risk of corrosion to equipment and extend the service life of the system.

[0157] (5) The present invention uses the CO2-containing tail gas recovered by the fan to pass into the calcium precipitation tank, and selectively adds Na2CO3 to promote the Ca precipitation under the controlled pH condition. 2+ It is removed by precipitation in the form of calcium carbonate to avoid Ca 2+ Enrichment improves effluent quality and reduces scaling risk.

[0158] (6) The precipitation products such as magnesium hydroxide, calcium aluminate, Freund's salt and calcium carbonate produced during the treatment process can be used as desulfurizers, adsorbents or ion exchange materials respectively to achieve the coordinated treatment of wastewater and solid waste, reduce secondary pollution, and have good comprehensive resource utilization value.

[0159] (7) The device structure proposed in the present invention is highly consistent with the treatment method. Each unit in the system includes a stirring device, a reagent dosing system, a CO 2 The bubbling unit, pH adjustment system and solid-liquid separation equipment are all coordinated and cooperated, which is convenient for implementation in engineering practice. The system has strong stability and simple operation.

[0160] (8) The results of actual treatment tests on high-salinity wastewater from typical thermal power plants showed that Ca 2+ Mg 2+ 、SO4 2- and Cl - The removal rates of major pollutants such as chlorinated hydrocarbons and chlorinated hydrocarbons reached 99%, 99.9%, 99.9% and 81.21% respectively, with significant treatment effects, which can meet the technical requirements of recycling or standard discharge, indicating that the scheme of the present invention has good application prospects.

[0161] In the several 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 example, the division of units is merely a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of modules or units, which can be electrical, mechanical or other forms.

[0162] The above embodiments are intended only to illustrate the technical solutions of the present application and are not intended to limit them. The present application is not limited to the precise structures described above and illustrated in the accompanying drawings, and it cannot be assumed that the specific implementation of the present application is limited to these descriptions. For those skilled in the art of the present application, any changes and modifications made without departing from the concept of the present application should be deemed to fall within the scope of protection of the present application.

Claims

1. A method for removing hardness, desulfurization and dechlorination of high-salt wastewater using carbide slag, characterized in that: The following steps are involved: S1. Heavy metal removal: The high-salt wastewater is introduced into the neutralization tank, carbide slag and TMT-15 are added, and the pH value is adjusted to 9.0-9.5 to remove heavy metal ions in the wastewater; S2, magnesium ion removal: the neutralized wastewater is introduced into the magnesium precipitation tank, and calcium carbide slag is added to adjust the pH value to 11.0-12.5 to make the Mg 2+ It is removed as a precipitate of magnesium hydroxide; S3, the first stage of desulfurization and dechlorination: the supernatant of the magnesium precipitation tank is introduced into the first reaction tank, carbide slag and sodium aluminate are added, and the pH value is controlled at 11.5-13.5 to make SO4 2- With Ca 2+ 、Al 3+ The reaction generates ettringite precipitation and removes part of the Cl - ; S4, the second stage of dechlorination: the effluent from the first reaction tank is introduced into the second reaction tank, and calcium carbide slag and sodium metaaluminate are continuously added to control the pH value to 11.5-13.5, so that Cl - With Ca 2+ 、Al 3+ The reaction generates a precipitate of Freund's salt; S5. Calcium ion removal: The effluent from the second reaction tank is introduced into the calcium precipitation tank, CO2 gas is introduced and Na2CO3 is selectively added, and the pH is adjusted to 9.0-9.5 to make Ca 2+ It is removed as a precipitate of calcium carbonate; S6. Solid-liquid separation unit group: The precipitates produced in each step are separated into solid and liquid through a plate and frame filter press or a centrifuge, and the obtained solids are used in the desulfurization process or resource utilization.

2. The method for removing hardness, desulfurization and dechlorination of high-salt wastewater using carbide slag according to claim 1, wherein: The amount of TMT-15 added to the neutralization tank in step S1 is 10-100 mg / L.

3. A method for removing hardness, desulfurization and dechlorination of high-salt wastewater using carbide slag according to claim 1, characterized in that: In step S2, the dosage of carbide slag in the magnesium precipitation tank is 3-6 g / L, and the reaction time is 45-60 min.

4. The method for removing hardness, desulfurization and dechlorination of high-salt wastewater using carbide slag according to claim 1, wherein: In step S3, in the first reaction tank, calcium carbide slag can release Ca 2+ The molar amount of Cl in wastewater - and SO4 2- The molar ratio of the total molar amount is 2.5:1, and the amount of sodium metaaluminate added is proportional to the amount of Cl in the solution. - and SO4 2- The weighted molar concentration C1 satisfies the molar ratio of 1:1, and the weighted molar concentration 5. The method for removing hardness, desulfurization and dechlorination of high-salt wastewater using carbide slag according to claim 1, characterized in that: Step S4: Ca2+ released from the carbide slag in the second reaction tank 2+ and Cl in wastewater - The molar ratio of sodium metaaluminate and Cl is 8-14:

1. - The molar ratio is 2-2.25:

1.

6. The method for removing hardness, desulfurization and dechlorination of high-salt wastewater using carbide slag according to claim 1, characterized in that: In step S5, CO2 with a mass fraction of 10-20% is introduced into the calcium precipitation tank, and the reaction time is 10-20 minutes.

7. A device for removing hardness, desulfurization and dechlorination of high-salt wastewater using carbide slag, which realizes the method for removing hardness, desulfurization and dechlorination of high-salt wastewater using carbide slag according to any one of claims 1 to 6, characterized in that: Includes the following connected in sequence: Neutralization tank, used for adding carbide slag and TMT-15, equipped with pH adjustment and stirring device; Magnesium precipitation tank, used to add calcium carbide slag and precipitate Mg 2+ , equipped with a stirring system; The first reaction tank is used to add carbide slag and sodium aluminate to react and remove SO4 2- With some Cl - , equipped with stirring and chemical dosing devices; The second reaction tank is used to add carbide slag and sodium aluminate to further remove Cl, and is equipped with a stirring and reagent dosing device; Calcium precipitation tank, used to introduce CO2 and add Na2CO3 to precipitate Ca 2+ , equipped with CO2 bubbling device, Na2CO3 dosing system and pH control device; Desulfurization tower, used to receive the treated supernatant and part of the sediment; Fan, CO2 bubbling device connecting the desulfurization tower outlet and the calcium precipitation tank; The solid-liquid separation unit group includes a first plate-frame filter press, a first centrifuge, a second plate-frame filter press, and a second centrifuge; wherein: The first plate and frame filter press is connected to the sediment outlet at the bottom of the magnesium precipitation 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 sediment outlet at the bottom of the second reaction tank; The second centrifuge is connected to the sediment outlet at the bottom of the calcium precipitation tank.

8. The device for removing hardness, desulfurization and dechlorination of high-salt wastewater using carbide slag according to claim 7, characterized in that: The supernatant outlet of the magnesium precipitation tank is connected to the desulfurization tower through a pipeline; The outlet of the first plate and frame filter press is connected to a desulfurization tower.

9. The device for removing hardness, desulfurization and dechlorination of high-salt wastewater using carbide slag according to claim 7, characterized in that: In the solid-liquid separation unit group: The first plate and frame filter press is used to separate magnesium hydroxide precipitates from the magnesium precipitation tank; The first centrifuge is used to separate the ettringite and Freund's salt precipitates in the first reaction tank; The second plate and frame filter press is used to separate the Freund's salt precipitate in the second reaction tank; The second centrifuge is used to separate calcium carbonate precipitates from the calcium precipitation tank.

10. The device for removing hardness, desulfurization and dechlorination of high-salt wastewater using carbide slag according to claim 7, characterized in that: The blower pressurizes and transports the CO2-containing flue gas at the outlet of the desulfurization tower to the CO2 bubbling device of the calcium precipitation tank.

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