Resourceful treatment method of desulfurization wastewater

Abstract

The invention relates to the technical field of desulfurization wastewater treatment, in particular to a resourceful treatment method for desulfurization wastewater. The resourceful treatment method of the desulfurization wastewater comprises the following steps: (1) sequentially carrying out coagulation and filter pressing on the desulfurization wastewater to obtain a filter cake and a clear solution, (2) sequentially carrying out ozonization treatment, ultrafiltration and electrolysis on the clear solution to obtain a chlorine-rich solution and a salt solution, and (3) carrying out deamination treatment on the salt solution to obtain an ammonium sulfate solution and a sodium sulfate solution. The method disclosed by the invention is simple and efficient in process, can be used for recovering the desulfurized gypsum raw material, effectively removing chloride ions and recovering ammonia, and can also be used for extracting sodium sulfate from the desulfurized wastewater, so that the desulfurized wastewater is fully recycled.

Description

Technical Field

[0001] This invention relates to the field of desulfurization wastewater treatment technology, and in particular to a resource-based treatment method for desulfurization wastewater. Background Technology

[0002] Desulfurization wastewater from thermal power plants is characterized by high salinity (up to 60 g / L), high hardness (over 2 g / L as CaCO3), and high suspended solids (10-30 g / L) generated by the limestone-gypsum wet desulfurization process. It also contains heavy metals such as mercury and lead, as well as soluble salts like chloride ions. Direct discharge of untreated desulfurization wastewater into the natural environment poses a serious threat to soil and aquatic ecosystems, and heavy metal ions can accumulate through the food chain, ultimately impacting human health. Recycling desulfurization wastewater from thermal power plants avoids discharge and effectively conserves water resources. Currently, efficient water-salt separation is crucial for zero discharge of desulfurization wastewater during its conversion into circulating water. However, conventional zero-discharge technologies for desulfurization wastewater often focus on water recycling, treating salt components primarily as mixed salts and disposing of them as solid waste, failing to achieve resource recovery. This not only wastes resources but also increases the environmental burden on enterprises.

[0003] In existing technologies, patent CN117720242A uses a multi-stage electrodialysis process to dechlorinate desulfurization wastewater and prepares chlorine into a snow-melting agent, but it does not utilize other elements for resource recovery; patent CN118978291A recovers sodium sulfate and ammonium sulfate from desulfurization wastewater and condenses and recovers the water produced by salt evaporation and crystallization, but it does not consider chloride ions in the wastewater, and the long-term accumulation of chloride ions in the solution can lead to pipeline corrosion and reduce the service life of hardware equipment; patent CN115259490A adopts a nanofiltration-RO-electrodeionization + electrodialysis technical route to convert salts in desulfurization wastewater into corresponding acids and alkalis. In the electrodialysis acid and alkali production stage of this process, NH4 may also be present. + and Na + The reaction of two cations results in the release of ammonia, leading to nitrogen loss and air pollution. Patent CN112573720A provides a technical route of ultrafiltration-nanofiltration-ozone oxidation-ammonia removal membrane, converting ammonia nitrogen into nitrogen fertilizer, with concentrated brine sent to a chlor-alkali plant. However, this process causes sulfate ions to re-enter the influent tank, affecting the efficiency of nanofiltration per unit time, and the process flow does not address the ammonia release issue. It is evident that existing technologies do not fully achieve resource recovery of desulfurization wastewater. Therefore, there is an urgent need to provide a resource recovery method for desulfurization wastewater, improving resource recovery efficiency and reducing the generation of gaseous pollutants. Summary of the Invention

[0004] In view of this, the present invention provides a method for the resource-based treatment of desulfurization wastewater. This method can recover desulfurization gypsum raw materials, effectively remove chloride ions and recover ammonia, and also extract sodium sulfate from desulfurization wastewater, so as to fully utilize the desulfurization wastewater as a resource.

[0005] This invention provides a method for the resource-based treatment of desulfurization wastewater, comprising the following steps:

[0006] (1) The desulfurization wastewater is subjected to coagulation and pressure filtration in sequence to obtain filter cake and clear liquid.

[0007] (2) The clarified liquid is subjected to ozonation, ultrafiltration and electrolysis in sequence to obtain chlorine-rich solution and salt solution.

[0008] (3) The salt solution is subjected to deammoniation treatment to obtain ammonium sulfate solution and sodium sulfate solution.

[0009] Optionally, the following steps are also included:

[0010] The gas generated by coagulation is absorbed into water to obtain ammonia-rich water.

[0011] The ammonia-rich water is mixed with the salt solution for subsequent deammoniation treatment.

[0012] Optionally, the mass concentration of ammonia in the ammonia-rich water is 12-18%.

[0013] Optionally, the coagulation method is the dual-alkali method, which specifically involves first adding sodium hydroxide to adjust the pH of the desulfurization wastewater to 11.5, then stopping the addition of sodium hydroxide, waiting for 3-5 minutes, and then adding sodium carbonate with a calcium ion molar concentration of 1.1-1.2 times, and letting it stand for 50-70 minutes.

[0014] Optionally, the filter cloth used for the pressure filtration has a mesh size of 300-500, the pressure filtration pressure is 0.8-1.2 MPa, and the pressure filtration time is 15-20 min.

[0015] Optionally, the mass ratio of ozone to COD during the ozonation process is 1.1-1.3:1, and the ozonation time is 15-25 min.

[0016] Optionally, the ultrafiltration is performed in a hollow fiber membrane module with a membrane pore size ≤ 0.2 μm.

[0017] Optionally, the electrolysis is carried out in a monovalent anion exchange membrane electrolytic cell. The initial anolyte in the anode chamber is a hydrochloric acid aqueous solution with a concentration of 0.1-0.3 mol / L, and the initial catholyte in the cathode chamber is ultrafiltration wastewater. The anode uses a DSA electrode, and the cathode uses a gas diffusion electrode. The current density is 75-85 A / m. 2The cathode solution in the cathode chamber should be replaced every 25-35 minutes of electrolysis. The anolyte solution in the anode chamber should be replaced when the chloride ion concentration reaches 45-55 g / L.

[0018] Optionally, the deammoniation treatment is carried out in a deammoniation membrane module, wherein the absorbent inside the deammoniation membrane module is an aqueous solution of H2SO4 with a mass concentration of 25%, and the outside is the salt solution, which is preheated to 38-42°C.

[0019] Optionally, the method further includes concentrating and crystallizing the ammonium sulfate solution and the sodium sulfate solution and drying them respectively, and recovering the water vapor during the concentration and crystallization process to obtain ammonium sulfate and sodium sulfate.

[0020] The resource-based treatment method for desulfurization wastewater provided by this invention firstly coagulates the desulfurization wastewater, softens and removes hardness, and removes flocculants from the flocculated wastewater by pressure filtration, obtaining filter cake and clear liquid. The filter cake can be used to prepare desulfurization gypsum, while the clear liquid undergoes ozonation treatment to remove organic matter, followed by ultrafiltration to remove residual particulate matter and further remove organic matter. The filtrate obtained from ultrafiltration is then electrolyzed, yielding a chlorine-rich solution (mainly composed of HCl, which can be used to prepare hydrochloric acid solution) in the anode chamber, thereby recovering chloride ions, and a salt solution in the cathode chamber. The salt solution undergoes subsequent deammoniation treatment to obtain ammonium sulfate solution and sodium sulfate solution, thereby recovering ammonia and sodium sulfate, achieving the recovery of ammonium sulfate and sodium sulfate. As can be seen from the embodiments described in this application, the method of the present invention can fully utilize desulfurization wastewater for resource recovery. The resulting filter cake has low water content and high calcium content (15-21%), and can be used as a raw material for desulfurization gypsum. At the same time, it can also generate chlorine-rich liquid, which can be used as a raw material for preparing hydrochloric acid. Furthermore, it can fully recover ammonia nitrogen and sulfate ions to prepare ammonium sulfate and sodium sulfate byproducts, thereby obtaining additional economic benefits. Attached Figure Description

[0021] The above and other objects, features, and advantages of the invention will be apparent from the following description of preferred embodiments illustrating the gist of the invention and its use, and the accompanying drawings, in which:

[0022] Figure 1 This is a process flow diagram of the desulfurization wastewater resource utilization treatment method in an embodiment of the present invention. Detailed Implementation

[0023] The present invention will be described below through specific embodiments. Those skilled in the art will understand that the specific embodiments described below are for illustrative purposes only and do not limit the scope of the invention in any way. Furthermore, in the following embodiments, unless otherwise specified, the reagents and equipment used are commercially available. If specific processing conditions and methods are not explicitly described in the following embodiments, conditions and methods known in the art can be used for processing.

[0024] This solution provides a resource-based treatment method for desulfurization wastewater, including the following steps:

[0025] (1) The desulfurization wastewater is subjected to coagulation and pressure filtration in sequence to obtain filter cake and clear liquid.

[0026] (2) The clarified liquid is subjected to ozonation, ultrafiltration and electrolysis in sequence to obtain chlorine-rich solution and salt solution.

[0027] (3) The salt solution is subjected to deammoniation treatment to obtain ammonium sulfate solution and sodium sulfate solution.

[0028] The method of this invention achieves hardening removal by coagulating and pressure filtering desulfurization wastewater. The resulting filter cake can be used as raw material for desulfurization gypsum. The resulting clarified liquid is further subjected to ozonation to remove organic matter, followed by ultrafiltration to remove residual particles and organic matter. The resulting filtrate is then further electrolyzed to enrich chloride ions in a chloride-rich solution for use as a raw material for hydrochloric acid. Simultaneously, ammonia nitrogen, sulfate, and sodium ions are enriched in a salt solution. The salt solution is then subjected to deammoniation treatment to obtain ammonium sulfate and sodium sulfate solutions, thereby achieving the recovery of ammonium sulfate and sodium sulfate. This method achieves full resource utilization of desulfurization wastewater.

[0029] The present invention first performs coagulation and pressure filtration on desulfurization wastewater in sequence to obtain filter cake and clear liquid.

[0030] This invention does not specifically limit the source of the desulfurization wastewater; general desulfurization wastewater from thermal power plants can be treated. In this embodiment of the invention, the desulfurization wastewater is desulfurization wastewater from a thermal power plant, wherein the desulfurization process employs the limestone-lime slurry method.

[0031] In some embodiments of the present invention, the coagulation method is a dual-alkali method. Specifically, the dual-alkali method involves first adding sodium hydroxide to adjust the pH of the desulfurization wastewater to 11.5-11.7, preferably 11.5, then stopping the addition of sodium hydroxide and waiting for 3-5 minutes. Then, sodium carbonate with a calcium ion molar concentration of 1.1-1.2 times is added, and the mixture is allowed to stand for 50-70 minutes, preferably 60 minutes. In this invention, during the addition of sodium hydroxide, the pH of the desulfurization wastewater will stabilize at 10.5-11.0 for a certain period, generating calcium hydroxide and magnesium hydroxide. After the reaction is complete, the pH will suddenly jump to 11.5-11.7. Therefore, when the pH reaches 11.5-11.7, the addition of sodium hydroxide is stopped, and after waiting 3-5 minutes for the pH to stabilize, sodium carbonate is added to further remove calcium ions.

[0032] In some embodiments of the present invention, the resource recovery method further includes the following steps:

[0033] The gas generated by coagulation is absorbed into water to obtain ammonia-rich water.

[0034] The ammonia-rich water is mixed with the salt solution for subsequent deammoniation treatment.

[0035] This invention absorbs the gas generated by coagulation with water and then performs subsequent ammonia removal treatment, thus avoiding the release of ammonia and air pollution. At the same time, after mixing with salt solution for ammonia removal treatment, ammonia can be converted into ammonium sulfate for recovery, generating additional economic benefits.

[0036] In some embodiments of the invention, the coagulation is carried out in a coagulation apparatus equipped with a gas collection device, thereby enabling the gas generated during coagulation to be collected and transported to water for absorption.

[0037] In some embodiments of the present invention, the water used to absorb the gas generated by coagulation is distilled water; the absorption is carried out in a gas absorption tank or gas absorption vessel, and a pressure gauge and an ammonia concentration meter may be installed on the gas absorption tank or absorption vessel to detect the pressure and ammonia concentration during the absorption process.

[0038] In some embodiments of the present invention, the mass concentration of ammonia in the ammonia-rich water is 12-18%, that is, when the ammonia concentration is 12-18%, the ammonia-rich water is mixed with a salt solution for subsequent deammoniation treatment; the mass concentration of ammonia in the ammonia-rich water can specifically be 12%, 13%, 15%, 18%, etc.

[0039] In some embodiments of the present invention, the filter cloth used for pressure filtration has a mesh size of 300-500 mesh, specifically 300 mesh, 400 mesh, 500 mesh, etc.; the pressure filtration is 0.8-1.2 MPa, specifically 0.8 MPa, 1.0 MPa, 1.2 MPa; and the filtration time is 15-20 min, specifically 15 min, 18 min, 20 min, etc. In the present invention, using a filter cloth with a smaller pore size and performing high-pressure filtration for a short time can retain most of the precipitate, resulting in a clearer filtrate and a sludge cake with a lower water content.

[0040] In this invention, the filter cake obtained by pressure filtration contains a large amount of calcium carbonate, which can be used to prepare desulfurization gypsum, specifically by adsorbing sulfur dioxide gas in desulfurization flue gas to generate calcium sulfate.

[0041] After obtaining the clear liquid, the present invention sequentially performs ozonolysis, ultrafiltration and electrolysis on the clear liquid to obtain chlorine-rich liquid and salt solution.

[0042] In some embodiments of the present invention, the mass ratio of ozone to COD during the ozonation process is 1.1-1.3:1, specifically 1.1:1, 1.2:1, 1.3:1, etc., and the ozonation time is 15-25 min, specifically 15 min, 20 min, 25 min, etc.; wherein the mass ratio of ozone to COD refers to the mass ratio of ozone required per unit volume of wastewater to the mass ratio of organic matter per unit volume, wherein the mass of organic matter is expressed as chemical oxygen demand per unit volume.

[0043] In some embodiments of the present invention, the ultrafiltration is performed in a hollow fiber membrane module, wherein the membrane pore size of the hollow fiber membrane module is ≤0.2μm, such as 0.1μm.

[0044] In some embodiments of the present invention, the electrolysis is carried out in a monovalent anion exchange membrane electrolytic cell. The initial anolyte in the anode chamber is an aqueous hydrochloric acid solution with a concentration of 0.1-0.3 mol / L (specifically, it can be 0.1 mol / L, 0.15 mol / L, 0.3 mol / L, etc.), and the initial catholyte in the cathode chamber is ultrafiltration wastewater. The current density is 75-85 A / m. 2 Specifically, it can be 75A / m 2 80A / m 2 85A / m 2The cathode solution in the cathode chamber is replaced every 25-35 minutes of electrolysis, specifically after 25, 30, or 35 minutes. The discharged cathode solution is a salt solution. When the chloride ion concentration in the anolyte in the anode chamber reaches 45-55 g / L (specifically 45 g / L, 50 g / L, or 55 g / L), the anolyte solution is replaced. The discharged anolyte solution is a chloride-rich solution. The anode uses a DSA electrode (i.e., a size-stabilized anode), and the cathode uses a gas diffusion electrode. In this invention, the monovalent anion exchange membrane electrolytic cell is a closed electrolytic cell. In this invention, during electrolysis, chloride ions accumulate in the anode chamber, partially electrolyzing to form chlorine gas. This chlorine gas dissolves in the anode solution to form hypochlorous acid and hydrochloric acid, reaching equilibrium and thus forming a chloride-rich solution. Sodium, sulfate, and ammonium ions accumulate in the cathode chamber, forming a salt solution there, thereby achieving chloride ion recovery. Furthermore, electrolysis in the cathode chamber generates hydroxide ions, which can subsequently combine with ammonium ions to form ammonia, promoting subsequent deammoniation treatment. The chloride-rich solution can then be used to prepare hydrochloric acid solution, further realizing resource utilization.

[0045] After obtaining the salt solution, the present invention performs ammonia removal treatment on the salt solution to obtain ammonium sulfate solution and sodium sulfate solution.

[0046] In some embodiments of the present invention, the ammonia removal treatment is carried out in an ammonia removal membrane module. The absorbent inside the membrane module is an aqueous solution of H2SO4 with a mass concentration of 20-30% (e.g., 20%, 25%, 30%), and the outside is the salt solution, which is preheated to 38-42°C (e.g., 38°C, 40°C, 42°C). During the ammonia removal process, an ammonium sulfate solution is formed inside the membrane module, and a sodium sulfate solution is formed outside the membrane module, thereby achieving the separation of ammonium sulfate and sodium sulfate, which can be further recovered. Furthermore, preheating the salt solution to 38-42°C promotes the formation of ammonia (NH3), causing ammonia to overflow from the salt solution and enter the membrane module for absorption.

[0047] In some embodiments of the present invention, the resource recovery method further includes concentrating and crystallizing the ammonium sulfate solution and the sodium sulfate solution separately, and drying them, while recovering the water vapor from the concentration and crystallization process to obtain ammonium sulfate and sodium sulfate; the water vapor can be recycled for the absorption step of the gas generated by condensation. The present invention does not specifically limit the method of concentration and crystallization; conventional methods for producing ammonium sulfate and sodium sulfate can be used. The present invention also does not specifically limit the drying method; drying to a moisture content of ≤1.0% for ammonium sulfate and ≤0.5% for sodium sulfate is sufficient. In embodiments of the present invention, the drying temperature for ammonium sulfate is 65°C, and the drying temperature for sodium sulfate is 120°C.

[0048] like Figure 1The diagram shows a process flow chart of the resource-based treatment method for desulfurization wastewater in an embodiment of the present invention. Specifically, the desulfurization wastewater is subjected to coagulation, pressure filtration, ozone oxidation, ultrafiltration, electrolysis, and deammoniation treatment in sequence to obtain ammonium sulfate solution and sodium sulfate solution. The ammonium sulfate solution and sodium sulfate solution are concentrated and crystallized to obtain ammonium sulfate and sodium sulfate, respectively. The gas generated by coagulation is absorbed by water, and the resulting ammonia water can be combined with the salt solution generated by electrolysis for subsequent deammoniation steps. The filter cake generated by compression can be used to produce desulfurization gypsum, and the chlorine-rich solution generated by electrolysis can be used to prepare hydrochloric acid solution.

[0049] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. The embodiments of this application are only examples, and all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0050] Example 1

[0051] (1) The desulfurization wastewater treated in this embodiment is desulfurization wastewater from a thermal power plant, with a suspended solids (SS) concentration of 7.5 g / L and NH4+ concentration of 40 g / L. + -N concentration 0.11 g / L, Ca 2+ Concentration 0.68 g / L, Mg 2+ Concentration 0.74 g / L, Cl - Concentration 2.8 g / L, SO4 2- Concentration 0.26 g / L, flow rate 8 m³ / L 3 / h.

[0052] (2) The desulfurization wastewater was coagulated to remove hardness using a double-alkali method (specifically, sodium hydroxide was added to adjust the pH to the range of 10.5-11.0, and after the pH jumped to 11.5 and stopped decreasing, waited for 3 minutes, then sodium carbonate with a calcium ion molar concentration of 1.1 times was added, and the mixture was allowed to stand for 60 minutes). The coagulated mixture was then passed into a filter press and filtered at 1.0 MPa for 15 minutes to obtain a clear liquid (containing Na+). + Cl - NH4 + and SO4 2- The gas generated by coagulation is fed into distilled water, and when the concentration of ammonia in the water reaches 15%, it is fed into the deammoniation membrane module together with the salt solution generated by subsequent electrolysis for deammoniation treatment.

[0053] (3) The clarified liquid was subjected to ozonation treatment (ozone to COD mass ratio of 1.2:1) for 20 min, and then passed into a hollow fiber membrane module (membrane pore size of 0.1 μm) for ultrafiltration to remove residual particulate matter and some organic matter. The ultrafiltration effluent was then passed into the cathode chamber of a monovalent anion exchange membrane electrolysis cell (the anode is a DSA electrode and the cathode is a gas diffusion electrode) at 80 A / m 2Electrolysis was performed at a current density of 0.1 mol / L hydrochloric acid aqueous solution in the anode chamber. When the chloride ion concentration in the anode chamber reached 50 g / L, the electrolyzed anode solution (i.e., chloride-rich solution) was drained and replaced with fresh anode solution. The cathode solution (i.e., the solution in the cathode chamber) was replaced every 30 minutes. The drained electrolyzed cathode solution contained Na+. + NH4 + and SO4 2- A mixed solution, i.e., a salt solution.

[0054] (4) The salt solution is passed into the deammoniation membrane module for deammoniation treatment. Ammonium sulfate solution is obtained inside the membrane module and sodium sulfate solution is obtained outside the membrane module. The two solutions are then evaporated and crystallized separately, and the water vapor in the crystallization process is recovered and concentrated to obtain wet ammonium sulfate and wet sodium sulfate. The wet ammonium sulfate is dried at 65°C to a moisture content of ≤1.0% to obtain ammonium sulfate; the wet sodium sulfate is dried at 120°C to a moisture content of ≤0.5% to obtain sodium sulfate.

[0055] Example 2

[0056] (1) The desulfurization wastewater treated in this embodiment is desulfurization wastewater from a thermal power plant, with a suspended solids (SS) concentration of 8.2 g / L and NH4+ concentration of 40 g / L. + -N concentration 0.21 g / L, Ca 2+ Concentration 1.2 g / L, Mg 2+ Concentration 0.52 g / L, Cl - Concentration 3.2 g / L, SO4 2- Concentration 0.54 g / L, flow rate 10 m³ / L 3 / h.

[0057] (2) The desulfurization wastewater was coagulated to remove hardness using a double-alkali method (specifically, sodium hydroxide was added to adjust the pH to the range of 10.5-11.0, and after the pH jumped to 11.5 and stopped decreasing, waited for 3 minutes, then sodium carbonate with a calcium ion molar concentration of 1.1 times was added, and the mixture was allowed to stand for 60 minutes). The coagulated mixture was then passed into a filter press and filtered at 1.0 MPa for 15 minutes to obtain a clear liquid (containing Na+). + Cl - NH4 + and SO4 2- The gas generated by coagulation is fed into distilled water, and when the concentration of ammonia in the water reaches 15%, it is fed into the deammoniation membrane module together with the salt solution generated by subsequent electrolysis for deammoniation treatment.

[0058] (3) The clarified liquid was subjected to ozonation treatment (ozone to COD mass ratio of 1.2:1) for 20 min, and then passed into a hollow fiber membrane module (membrane pore size of 0.1 μm) for ultrafiltration to remove residual particulate matter and some organic matter. The ultrafiltration effluent was then passed into the cathode chamber of a monovalent anion exchange membrane electrolysis cell (the anode is a DSA electrode and the cathode is a gas diffusion electrode) at 80 A / m 2 Electrolysis was performed at a current density of [insert current density here]. The initial anolyte in the anode chamber was a 0.3 mol / L hydrochloric acid aqueous solution. When the chloride ion concentration in the anode chamber reached 50 g / L, the electrolyzed anolyte (i.e., chloride-rich solution) was drained and replaced with a fresh anolyte. The cathode solution (i.e., the solution in the cathode chamber) was changed every 30 minutes. The drained electrolyzed cathode solution contained Na [insert current density here]. + NH4 + and SO4 2- A mixed solution, i.e., a salt solution.

[0059] (4) The salt solution is passed into the deammoniation membrane module for deammoniation treatment. Ammonium sulfate solution is obtained inside the membrane module and sodium sulfate solution is obtained outside the membrane module. The two solutions are then evaporated and crystallized separately, and the water vapor in the crystallization process is recovered and concentrated to obtain wet ammonium sulfate and wet sodium sulfate. The wet ammonium sulfate is dried at 65°C to a moisture content of ≤1.0% to obtain ammonium sulfate; the wet sodium sulfate is dried at 120°C to a moisture content of ≤0.5% to obtain sodium sulfate.

[0060] Example 3

[0061] (1) The desulfurization wastewater treated in this embodiment is desulfurization wastewater from a thermal power plant, with a suspended solids (SS) concentration of 6.6 g / L and NH4+ concentration of 40 g / L. + -N concentration 0.27 g / L, Ca 2+ Concentration 2.5 g / L, Mg 2+ Concentration 1.0 g / L, Cl - Concentration 5.1 g / L, SO4 2- Concentration 6.3 g / L, flow rate 8 m³ / L 3 / h.

[0062] (2) The desulfurization wastewater was coagulated to remove hardness using a double-alkali method (specifically, sodium hydroxide was added to adjust the pH to the range of 10.5-11.0, and after the pH jumped to 11.5 and stopped decreasing, waited for 3 minutes, then sodium carbonate with a calcium ion molar concentration of 1.1 times was added, and the mixture was allowed to stand for 60 minutes). The coagulated mixture was then passed into a filter press and filtered at 1.0 MPa for 15 minutes to obtain a clear liquid (containing Na+). + Cl - NH4 + and SO4 2-The gas generated by coagulation is fed into distilled water, and when the concentration of ammonia in the water reaches 15%, it is fed into the deammoniation membrane module together with the salt solution generated by subsequent electrolysis for deammoniation treatment.

[0063] (3) The clarified liquid was subjected to ozonation treatment (ozone to COD mass ratio of 1.2:1) for 20 min, and then passed into a hollow fiber membrane module (membrane pore size of 0.1 μm) for ultrafiltration to remove residual particulate matter and some organic matter. The ultrafiltration effluent was then passed into the cathode chamber of a monovalent anion exchange membrane electrolysis cell (the anode is a DSA electrode and the cathode is a gas diffusion electrode) at 80 A / m 2 Electrolysis was performed for 30 minutes at a current density of [insert current density here]. The anolyte in the anode chamber was a 0.15 mol / L hydrochloric acid aqueous solution. When the chloride ion concentration in the anode chamber reached 50 g / L, the electrolyzed anolyte (i.e., chloride-rich solution) was drained and replaced with fresh anolyte. The cathode solution (i.e., the solution in the cathode chamber) was replaced every 30 minutes. The drained electrolyzed cathode solution contained Na [insert Na+ content here]. + NH4 + and SO4 2- A mixed solution, i.e., a salt solution.

[0064] (4) The salt solution is passed into the deammoniation membrane module for deammoniation treatment. Ammonium sulfate solution is obtained inside the membrane module and sodium sulfate solution is obtained outside the membrane module. The two solutions are then evaporated and crystallized separately, and the water vapor in the crystallization process is recovered and concentrated to obtain wet ammonium sulfate and wet sodium sulfate. The wet ammonium sulfate is dried at 65°C to a moisture content of ≤1.0% to obtain ammonium sulfate; the wet sodium sulfate is dried at 120°C to a moisture content of ≤0.5% to obtain sodium sulfate.

[0065] The material yield and economic benefits of the methods in Examples 1-3 were calculated using the following method:

[0066] 1. Calculate the filter cake yield and test the calcium content using ICP-OES. The results are shown in Table 1.

[0067] Table 1. Content and recovery rate of each component in the filter cake

[0068]

[0069] As shown in Table 1, the moisture content of the filter cake is less than 30%, and the calcium content is 15-21%. The filter cake can be used as a raw material for desulfurization gypsum. The low moisture content is beneficial to reducing the cost of drying and transportation of raw materials.

[0070] 2. Ion chromatography was used to analyze the NH4+ in the crystallized products ammonium sulfate and sodium sulfate. + -N, SO4 2- and Na +The content was determined, the yield of the substances was obtained, and the recovery rate was calculated. Specifically, the calcium recovery rate % = (calcium ion content in the influent - calcium ion content in the filtered water) / calcium ion content in the influent; the ammonium recovery rate % = mass of ammonium in ammonium sulfate / mass of ammonium in the influent; and the sulfate recovery rate % = mass of sulfate in sodium sulfate / mass of sulfate in the influent. The results are shown in Table 1.

[0071] As can be seen from Table 1, the method of the present invention can efficiently recover ammonium and sodium ions, realizing the resource utilization of ammonium and sodium ions.

[0072] 3. Based on ammonium sulfate at 850 yuan / ton and sodium sulfate at 450 yuan / ton, the economic benefits were calculated, and the results are shown in Table 2.

[0073] Table 2 Results of Economic Benefit Calculation

[0074]

[0075] As shown in Table 2, ammonia was recovered in the form of ammonium sulfate through the ammonia removal module. This method is different from the ammonia treatment mode that converts ammonia nitrogen into nitrogen gas, and it can improve the economic efficiency of ammonia treatment.

[0076] Although preferred embodiments of the invention have been shown and described, it is conceivable that those skilled in the art can devise various modifications to the invention within the spirit and scope of the appended claims.

Claims

1. A method for the resource-based treatment of desulfurization wastewater, comprising the following steps: (1) The desulfurization wastewater is subjected to coagulation and pressure filtration in sequence to obtain filter cake and clear liquid. (2) The clarified liquid is subjected to ozonation, ultrafiltration and electrolysis in sequence to obtain chlorine-rich solution and salt solution. (3) The salt solution is subjected to deammoniation treatment to obtain ammonium sulfate solution and sodium sulfate solution.

2. The method for resource-based treatment of desulfurization wastewater according to claim 1, characterized in that, It also includes the following steps: The gas generated by coagulation is absorbed into water to obtain ammonia-rich water. The ammonia-rich water is mixed with the salt solution for subsequent deammoniation treatment.

3. The method for resource-based treatment of desulfurization wastewater according to claim 2, characterized in that, The ammonia concentration in the ammonia-rich water is 12-18%.

4. The method for resource-based treatment of desulfurization wastewater according to claim 1, characterized in that, The coagulation method is the dual-alkali method. Specifically, the dual-alkali method involves first adding sodium hydroxide to adjust the pH of the desulfurization wastewater to 11.5-11.7, then stopping the addition of sodium hydroxide, waiting for 3-5 minutes, and then adding sodium carbonate at a calcium ion molar concentration of 1.1-1.2 times, and letting it stand for 50-70 minutes.

5. The method for resource-based treatment of desulfurization wastewater according to claim 1, characterized in that, The filter cloth used for the pressure filtration has a mesh size of 300-500, the pressure filtration pressure is 0.8-1.2 MPa, and the pressure filtration time is 15-20 min.

6. The method for resource-based treatment of desulfurization wastewater according to claim 1, characterized in that, The mass ratio of ozone to COD during the ozonation process is 1.1-1.3:1, and the ozonation time is 15-25 minutes.

7. The method for resource-based treatment of desulfurization wastewater according to claim 1, characterized in that, The ultrafiltration is carried out in a hollow fiber membrane module with a membrane pore size ≤0.2μm.

8. The method for resource-based treatment of desulfurization wastewater according to claim 1, characterized in that, The electrolysis is carried out in a monovalent anion exchange membrane electrolytic cell. The initial anolyte in the anode chamber is a hydrochloric acid aqueous solution with a concentration of 0.1-0.3 mol / L, and the initial catholyte in the cathode chamber is ultrafiltration wastewater. The anode uses a DSA electrode, and the cathode uses a gas diffusion electrode. The current density is 75-85 A / m. 2 The cathode solution in the cathode chamber should be replaced every 25-35 minutes of electrolysis. The anolyte solution in the anode chamber should be replaced when the chloride ion concentration reaches 45-55 g / L.

9. The method for resource-based treatment of desulfurization wastewater according to claim 1, characterized in that, The ammonia removal process is carried out in an ammonia removal membrane module. The absorbent inside the ammonia removal membrane module is an aqueous solution of H2SO4 with a mass concentration of 20-30%, and the outside is the salt solution, which is preheated to 38-42°C.

10. The method for resource-based treatment of desulfurization wastewater according to claim 1, characterized in that, It also includes concentrating and crystallizing the ammonium sulfate solution and the sodium sulfate solution separately and drying them, and recovering the water vapor during the concentration and crystallization process to obtain ammonium sulfate and sodium sulfate.

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