A method and system for concentrating and reducing the volume of a short-process evaporation pond

Abstract

The present invention relates to the technical field of high-salt water treatment, and provides a method and system for concentration and reduction of a short-process evaporation pond, the method comprising the following steps: S1. Preliminary treatment of wastewater from the evaporation pond using a sand filtration system and a composite scale inhibitor; S2. The wastewater after preliminary treatment is concentrated using a primary concentration system, and then enters a secondary concentration system to concentrate the wastewater; S3. After the wastewater is concentrated, the water produced by the secondary concentration system is returned to the water inlet of the primary concentration system, and the water produced by the primary concentration system is sent to a secondary reverse osmosis filtration system, and the water produced by the secondary reverse osmosis filtration system meets the standards and is discharged or reused; wherein, the membrane material in the primary concentration system is a modified polysulfone membrane. The present invention realizes short-process evaporation concentration and reduction through a sand filtration system + a composite scale inhibitor + a multi-stage membrane filtration system. This method is simple and convenient, and can realize low-pressure and high-fold concentration of wastewater.

Description

Technical Field

[0001] The invention belongs to the technical field of high-salt water treatment, and in particular relates to a method and system for concentrating and reducing the volume of a short-process evaporation pond. Background Art

[0002] Evaporation ponds are a technology for treating high-salinity water. They use natural conditions such as solar energy and wind energy to gradually evaporate water, while organic matter and other pollutants are concentrated and solidified in the evaporation ponds. Evaporation pond wastewater has the characteristics of high hardness and high salt. Long-term storage will cause groundwater, air, and soil pollution.

[0003] Reverse osmosis is a commonly used concentration and reduction method, but conventional reverse osmosis is quite demanding on the hardness of the incoming water, requiring the total hardness to be less than 500 mg / L. However, the total hardness of conventional evaporation pond brine often exceeds 1000 mg / L, or even higher, which requires front-end softening and hardness removal for better concentration and desalination. The softening and hardness removal methods currently available on the market are relatively complex and have long process routes, which are not conducive to promotion and use.

[0004] Chinese patent CN 208055142 U uses a combination of a softening reaction tank + a sedimentation tank + a PCF pore-adjustable fiber filter + a DTRO disc-tube reverse osmosis device + an intermediate water tank + a second security filter + an RO water treatment device to concentrate and reduce the evaporation pond wastewater. This invention can quickly capture micro-magnetic flocs. However, this invention has the problems of a long process route and a low concentration end point.

[0005] Therefore, there is an urgent need for a method and system for concentrating and reducing the volume of evaporation ponds in a short process, which can shorten the process while ensuring the desalination rate. Summary of the invention

[0006] In view of the existing technical problems, the purpose of the present invention is to provide a method and system for short-process evaporation pond concentration and reduction. The present invention realizes short-process evaporation concentration and reduction through sand filtration system + composite scale inhibitor + multi-stage membrane filtration system. This method is simple and convenient, can realize low-pressure high-multiple concentration of wastewater, and has good application value.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] On the one hand, the present invention provides a method for concentrating and reducing the amount of water in a short-process evaporation pond, and the method for concentrating and reducing the amount of water in a short-process evaporation pond comprises the following steps:

[0009] S1. Preliminary treatment of wastewater from evaporation ponds using sand filtration system and antiscalant;

[0010] S2. The wastewater after preliminary treatment is concentrated by the primary concentration system, and then enters the secondary concentration system to concentrate the wastewater;

[0011] S3. After the wastewater is concentrated, the water produced by the second-stage concentration system is returned to the water inlet of the first-stage concentration system, and the water produced by the first-stage concentration system is sent to the second-stage reverse osmosis filtration system. The water produced by the second-stage reverse osmosis filtration system meets the standards and is discharged or reused; among them, the membrane material in the first-stage concentration system is a modified polysulfone membrane;

[0012] The method can be divided into a short-process evaporation pond concentration and reduction method with low calcium hardness and a short-process evaporation pond concentration and reduction method with high calcium hardness; wherein, low calcium hardness corresponds to brine calcium hardness less than 1500 mg / L, and high calcium hardness corresponds to brine calcium hardness greater than 1500 mg / L.

[0013] The reaction mechanism and effects of the present invention are as follows:

[0014] 1. Phosphorus-containing scale inhibitors and synthetic polymer scale inhibitors are currently the most widely used scale inhibitors in the commercial market, but they have problems such as secondary pollution and poor biodegradability. The development of degradable, non-toxic and harmless green scale inhibitors is one of the research hotspots in the field of water treatment agents. Chitin is a nitrogen-containing polysaccharide. In addition to hydroxyl groups, chitin also contains acetylamino and amino functional groups in its molecules. There are many groups available for structural modification. New functional groups can be introduced into chitin through chemical modification, which can improve the properties and application performance of chitin and broaden its application range.

[0015] The present invention carboxylates chitin through an etherification reaction, and simultaneously adjusts the mass ratio of chitin, 10-15wt% sodium hydroxide aqueous solution, 3-6wt% urea aqueous solution, and the mass ratio of chitin and sodium chloroacetate to increase the degree of substitution of the carboxyl group, which is helpful for the subsequent grafting of 3,4,5-trihydroxybenzoic acid, thereby significantly improving its scale inhibition performance. Furthermore, the applicant introduces 3,4,5-trihydroxybenzoic acid, and the carboxyl group has the ability to react with Ca in the evaporation pond wastewater. 2+ Mg 2+ At the same time, 3,4,5-trihydroxybenzoic acid also contains phenolic hydroxyl active groups, which can effectively inhibit the growth of microorganisms such as bacteria and reduce the risk of biological contamination. Therefore, the modified chitin provided in this application can effectively alleviate the scaling problem in the treatment process of low and high calcium hardness water through chelation, dispersion and other effects, and reduce biological contamination; in addition, chitin and 3,4,5-trihydroxybenzoic acid are derived from natural animals and plants, and have the characteristics of non-toxicity and safety.

[0016] More importantly, the applicant unexpectedly discovered that adding a specific amount of chitosan biguanide hydrochloride helps to better alleviate the scaling problem in the treatment process of low and high calcium hardness water, and has a synergistic effect with modified chitin.

[0017] 2. The modified polysulfone membrane of the present invention has a moderate desalination rate and good anti-pollution property. On the one hand, the nanomaterial attapulgite is added to the aqueous solution, and octadecyl trimethyl ammonium chloride will electrostatically adsorb or complex with the metal ions in the attapulgite, so that the attapulgite is more evenly dispersed, and the attapulgite shows good stability in high temperature and salt water, and can greatly improve the oxidation resistance of the modified membrane on the basis of maintaining the original membrane separation performance, and has good salt resistance, and can still maintain a high regeneration efficiency even after being affected by pollution and scaling. On the other hand, amine pyraclostrobin is added to the aqueous solution containing m-phenylenediamine, and the amine pyraclostrobin molecular structure contains a thioformate functional group, which increases the amine content and amine diffusion rate in the oil phase, thereby increasing the cross-linking degree of polyamide, so that the polyamide separation layer has a smaller pore size, so that the desalination rate is suitable, which is conducive to achieving low-pressure high-fold concentration; at the same time, amine pyraclostrobin is conducive to antibacterial, achieving an anti-pollution effect, and further improving the life of the modified polysulfone membrane.

[0018] In some embodiments, the specific steps of the short-process evaporation pond concentration and reduction method with low calcium hardness are as follows:

[0019] A1. The wastewater from the evaporation pond is discharged to a two-stage sand filtration system for filtration, and a composite antiscalant is added for preliminary treatment;

[0020] A2. The wastewater after preliminary treatment is discharged to the primary concentration system, where it is concentrated at a pressure of 60-70 bar, and then enters the secondary concentration system where it is concentrated at a pressure of 60-70 bar;

[0021] A3. After the wastewater is concentrated, the water produced by the second-stage concentration system is returned to the water inlet of the first-stage concentration system. The water produced by the first-stage concentration system is sent to the second-stage reverse osmosis filtration system. The water produced by the second-stage reverse osmosis filtration system meets the standards and is discharged or reused.

[0022] In some embodiments, the specific steps of the high calcium hardness short-process evaporation pond concentration and reduction method are as follows:

[0023] B1. Add composite antiscalant before the wastewater from the evaporation pond is discharged into the two-stage sand filtration system, filter it into the two-stage sand filtration system, and then add composite antiscalant for preliminary treatment;

[0024] B2. The wastewater after preliminary treatment is discharged to the nanofiltration system for filtration. The water produced by the nanofiltration system enters the primary concentration system to concentrate the wastewater at a pressure of 60-70 bar, and then enters the secondary concentration system to concentrate the wastewater at a pressure of 60-70 bar;

[0025] B3. After the wastewater is concentrated, the water produced by the second-stage concentration system is returned to the water inlet of the first-stage concentration system. The water produced by the first-stage concentration system is sent to the second-stage reverse osmosis filtration system. The water produced by the second-stage reverse osmosis filtration system meets the standards and is discharged or reused.

[0026] In some embodiments, the composite scale inhibitor is modified chitin and chitosan biguanide hydrochloride, and the mass ratio of the two is (2-4):1.

[0027] In some embodiments, the method for preparing the modified chitin comprises the following steps:

[0028] (1) mixing chitin, a 10-15 wt% sodium hydroxide aqueous solution, and a 3-6 wt% urea aqueous solution, and performing a freeze-thaw process to obtain a chitin solution;

[0029] (2) adding the chitin solution and sodium chloroacetate obtained in step (1) into a reaction kettle, stirring and reacting at 5-15° C. for 72-96 hours, adjusting the pH value to neutral, dialyzing, and drying to obtain carboxymethyl chitin;

[0030] (3) The carboxymethyl chitin, 3,4,5-trihydroxybenzoic acid and water obtained in step (2) are added to a reactor, an inert gas is introduced, a 25-40 wt% aqueous solution of hydrogen peroxide is added, the mixture is stirred at 65-80° C. for 4-6 h, anhydrous ethanol is added for precipitation and separation, and the mixture is dried to obtain modified chitin.

[0031] In some embodiments, the mass ratio of chitin, 10-15 wt % sodium hydroxide aqueous solution, and 3-6 wt % urea aqueous solution in step (1) is 1: (4-7): (3-4).

[0032] In some embodiments, the mass ratio of chitin to sodium chloroacetate in the chitin solution in step (2) is 1:(2-3).

[0033] In some embodiments, the mass ratio of carboxymethyl chitin to 3,4,5-trihydroxybenzoic acid in step (3) is 1:(0.8-1.6).

[0034] In some embodiments, the method for preparing chitosan biguanide hydrochloride comprises the following steps:

[0035] ① Add chitosan to 0.2-0.5 mol / L hydrochloric acid aqueous solution, stir, precipitate with anhydrous ethanol, and vacuum dry to obtain chitosan hydrochloride powder;

[0036] ② Disperse the chitosan hydrochloride powder obtained in step ① in water, add dicyandiamide, heat to 100-120° C., stir to react, cool, and filter under reduced pressure to obtain a filtrate;

[0037] ③ The filtrate obtained in step ② is precipitated with anhydrous ethanol, filtered, and then the filter cake is washed with anhydrous ethanol, and vacuum dried to obtain chitosan biguanide hydrochloride.

[0038] In some embodiments, the mass ratio of the chitosan hydrochloride powder to dicyandiamide in step ② is 1:(1.5-5).

[0039] In some embodiments, the method for preparing the modified polysulfone membrane comprises the following steps:

[0040] Q1. Mix attapulgite and water, ultrasonically disperse for 24-48 hours, add octadecyltrimethylammonium chloride and sodium dodecyl sulfate, ultrasonically disperse for 30-60 minutes, centrifuge, and take the supernatant to obtain a solution;

[0041] Q2. Mix m-phenylenediamine, fenpyraclostrobin, camphorsulfonic acid and water, add an organic base to adjust the pH to 9-10.5, stir to obtain a liquid; add the solution obtained in step Q1, ultrasonically treat to obtain an aqueous phase solution, and set aside; mix the aromatic polyacyl chloride and the organic solvent, ultrasonically treat to obtain an oil phase solution, and set aside;

[0042] Q3. Take out the polysulfone membrane and fix it on a flat plate, pour the aqueous solution obtained in step Q2 on the surface of the polysulfone membrane and soak it for 3-8 minutes, pour out the excess aqueous solution, dry it, then pour the oil solution obtained in step Q2 on the surface of the polysulfone membrane and soak it for 0.5-1.5 minutes, pour out the excess oil solution, let it stand vertically to drain for 15-30 seconds, and dry it to obtain a modified polysulfone membrane.

[0043] In some embodiments, the mass ratio of m-phenylenediamine, fenpyraclostrobin and camphorsulfonic acid in step Q2 is 10:(1.5-3):(18-25).

[0044] In some embodiments, the mass ratio of attapulgite, octadecyltrimethylammonium chloride and sodium dodecyl sulfate in step Q1 is 1: (0.4-0.6): (0.03-0.08).

[0045] In some embodiments, the aromatic polyacyl chloride in step Q2 is selected from any one of 1,3-benzenedisulfonyl chloride, 1,3,5-benzenetrisulfonyl chloride and trimesoyl chloride.

[0046] In some embodiments, the mass ratio of m-phenylenediamine to aromatic polyacyl chloride in step Q2 is 1:(0.02-0.04).

[0047] On the other hand, the present invention provides a short-process evaporation pond concentration and reduction system. The short-process evaporation pond concentration and reduction with low calcium hardness includes the following systems: a sand filtration system, a primary concentration system, a second-stage concentration system, and a second-stage reverse osmosis filtration system; the short-process evaporation pond concentration and reduction with high calcium hardness includes the following systems: a sand filtration system, a nanofiltration system, a primary concentration system, a second-stage concentration system, and a second-stage reverse osmosis filtration system.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] 1. The present invention realizes short-process evaporation concentration reduction through sand filtration system + composite scale inhibitor + multi-stage membrane filtration system. This method is simple and convenient, can realize low-pressure and high-fold concentration of wastewater, and has good application value.

[0050] 2. The modified chitin of the present invention can effectively alleviate the scaling problem in the high calcium hardness water treatment process and reduce biological pollution through chelation, dispersion and other effects; in addition, the applicant unexpectedly discovered that adding a specific amount of chitosan biguanide hydrochloride helps to better alleviate the scaling problem in the low and high calcium hardness water treatment process, and has a synergistic effect with modified chitin.

[0051] 3. The modified polysulfone membrane of the present invention has less pollutants attached to the surface, has a moderate desalination rate, good anti-pollution performance and long-term stability, which increases the service life of the membrane and is also conducive to achieving low-pressure high-multiple concentration.

[0052] 4. The present invention uses the method of adding scale inhibitors to prevent scale, which is simple, convenient and has the advantages of low cost of chemicals compared to the traditional double-alkali chemical softening method.

[0053] 5. The present invention utilizes the characteristics of reverse osmosis semi-desalination rate to achieve the characteristics of low-pressure and high-multiple concentration of wastewater. DETAILED DESCRIPTION

[0054] The present invention will be described below in conjunction with specific embodiments. It should be noted that the following embodiments are examples of the present invention and are only used to illustrate the present invention, rather than to limit the present invention. Other combinations and various modifications within the concept of the present invention may be performed without departing from the spirit or scope of the present invention.

[0055] According to the methods specified in the following examples and comparative examples, various composite antiscalants and modified polysulfone membranes were prepared and applied to a method for concentration and reduction of short-process evaporation ponds.

[0056] In order to facilitate those skilled in the art to implement the present invention, some raw material manufacturers of the embodiments and comparative examples are described as follows:

[0057] Chitosan: purchased from Guangdong Hongyou Biotechnology Co., Ltd.;

[0058] Chitin: purchased from Shandong Poly Chemical Co., Ltd.;

[0059] Amide-based gemini quaternary ammonium salt surfactant: purchased from Jining Fangyu Chemical Co., Ltd., model GS-A6;

[0060] Polyamide membrane: purchased from Beijing Innogreen Technology Co., Ltd.;

[0061] Other raw materials are not specially specified and can be purchased from the market.

[0062] Preparation Example 1

[0063] The preparation method of modified chitin A comprises the following steps:

[0064] (1) 10 g of chitin, 55 g of a 12 wt% sodium hydroxide aqueous solution, and 35 g of a 5 wt% urea aqueous solution were mixed and stirred for 1 h, frozen at -40°C for 4 h, thawed at room temperature, and stirred for 1 h to obtain a chitin solution;

[0065] (2) adding the chitin solution obtained in step (1) and 25 g of sodium chloroacetate to a reaction kettle, stirring and reacting at 10° C. for 96 h, adjusting the pH value to neutral with a 1 mol / L hydrochloric acid aqueous solution, dialyzing, and freeze-drying at -45° C. for 8 h to obtain carboxymethyl chitin;

[0066] (3) 10 g of carboxymethyl chitin and 12 g of 3,4,5-trihydroxybenzoic acid and 220 ml of water obtained in step (2) are added to a reactor, nitrogen is introduced, 20 ml of a 30 wt% aqueous hydrogen peroxide solution is added, the mixture is stirred at 75° C. for 5 h, anhydrous ethanol is added until no more precipitation occurs, the precipitate is separated, and the mixture is dried at 60° C. to a constant weight to obtain modified chitin A.

[0067] Preparation Example 2

[0068] The preparation method of modified chitin B is the same as that of Preparation Example 1, except that the amount of sodium chloroacetate added in step (2) is 18 g.

[0069] Preparation Example 3

[0070] The preparation method of modified chitin C is the same as that of Preparation Example 1, except that the amount of 3,4,5-trihydroxybenzoic acid added in step (3) is 7 g.

[0071] Preparation Example 4

[0072] The preparation method of chitosan biguanide hydrochloride comprises the following steps:

[0073] ① Add 15g chitosan to 150ml 0.4mol / L hydrochloric acid aqueous solution, stir for 3h, precipitate with anhydrous ethanol, and vacuum dry at 70℃ for 12h to obtain chitosan hydrochloride powder;

[0074] ② Disperse 10 g of chitosan hydrochloride powder obtained in step ① in 1 L of water, add 32 g of dicyandiamide, heat to 120° C., stir and react for 5 h, cool to room temperature, and filter under reduced pressure to obtain a filtrate;

[0075] ③ The filtrate obtained in step ② was precipitated with anhydrous ethanol, and the filter cake was washed with anhydrous ethanol for 3 times after suction filtration, and vacuum dried at 80° C. for 24 h to obtain chitosan biguanide hydrochloride.

[0076] Preparation Example 5

[0077] The preparation method of modified polysulfone membrane A comprises the following steps:

[0078] Q1. Mix 1g of attapulgite and 1L of water, disperse by ultrasonic for 36h, add 0.5g of octadecyltrimethylammonium chloride and 0.05g of sodium dodecyl sulfate, ultrasonic for 45min, centrifuge at 8000rpm for 30min, take the supernatant and obtain a solution;

[0079] Q2. 45 g of m-phenylenediamine, 10 g of fenpyraclostrobin, 96.8 g of camphorsulfonic acid, and 2000 mL of water were mixed, triethylamine was added to adjust the pH to 10, and the mixture was stirred for 2 h to obtain a liquid; the solution obtained in step Q1 was added in a volume ratio of solution to liquid of 1:3, and the mixture was ultrasonically treated for 60 min to obtain an aqueous phase solution for standby use; 1.35 g of trimesoyl chloride and 800 mL of Isopar-G solvent were mixed, and the mixture was ultrasonically treated for 60 min to obtain an oil phase solution for standby use;

[0080] Q3. Take out the polysulfone membrane and fix it on a flat plate, pour the aqueous solution obtained in step Q2 on the surface of the polysulfone membrane and soak it for 5 minutes, pour out the excess aqueous solution, blow the membrane surface with a nitrogen air knife to remove water droplets and liquid droplets, and when there is just no aqueous solution visible on the membrane surface, pour the oil solution obtained in step Q2 on the surface of the polysulfone membrane and soak it for 1 minute, pour out the excess oil solution, let it stand vertically to drain for 20 seconds, and dry at 95°C for 8 minutes to obtain a modified polysulfone membrane.

[0081] Preparation Example 6

[0082] The preparation method of modified polysulfone membrane B is the same as that of Preparation Example 5, except that the amount of interphenylenediamine added in step Q2 is 37.5 g.

[0083] Preparation Example 7

[0084] The preparation method of modified polysulfone membrane C is the same as that of Preparation Example 5, except that amifenpyrad is not added in step Q2.

[0085] Example 1

[0086] The specific steps of a short-process evaporation pond concentration and reduction method with low calcium hardness are as follows:

[0087] A1. The evaporation pond wastewater with a calcium hardness of 400 mg / L, a magnesium hardness of 100 mg / L, and a TDS of 53000 mg / L is discharged to a two-stage sand filtration system for filtration, and a composite scale inhibitor is added at a dosage of 10 ppm for preliminary treatment; wherein the composite scale inhibitor is composed of modified chitin A and chitosan biguanide hydrochloride in a mass ratio of 3:1;

[0088] A2. The wastewater after preliminary treatment is discharged to the primary concentration system (the desalination rate of the primary concentration system is 69.8%), and the wastewater is concentrated to a concentrated water TDS of 105,000 mg / L at a pressure of 60 bar. Then the wastewater enters the secondary concentration system (the desalination rate of the secondary concentration system is 42.9%), and the wastewater is concentrated to a concentrated water TDS of 145,000 mg / L at a pressure of 60 bar.

[0089] A3. After the wastewater is concentrated, the water produced by the second-stage concentration system has a TDS of 60,000 mg / L and is returned to the water inlet of the first-stage concentration system. The water produced by the first-stage concentration system has a TDS of 16,000 mg / L and is sent to the second-stage reverse osmosis filtration system. The water produced by the second-stage reverse osmosis filtration system meets the standards and is discharged or reused. Among them, the membrane material in the first-stage concentration system and the second-stage concentration system is modified polysulfone membrane A.

[0090] Example 2

[0091] The specific steps of a short-process evaporation pond concentration and reduction method with low calcium hardness are as follows:

[0092] A1. The evaporation pond wastewater with calcium hardness of 400mg / L, magnesium hardness of 100mg / L and TDS of 53000mg / L was discharged to a two-stage sand filtration system for filtration, and a composite scale inhibitor was added at a dosage of 9ppm for preliminary treatment; wherein the composite scale inhibitor was composed of modified chitin A and chitosan biguanide hydrochloride in a mass ratio of 2:1;

[0093] A2. The wastewater after preliminary treatment is discharged to the primary concentration system (the desalination rate of the primary concentration system is 69.8%), and the wastewater is concentrated to a concentrated water TDS of 105,000 mg / L at a pressure of 70 bar, and then enters the secondary concentration system (the desalination rate of the secondary concentration system is 42.9%), and the wastewater is concentrated to a concentrated water TDS of 145,000 mg / L at a pressure of 70 bar;

[0094] A3. After the wastewater is concentrated, the water produced by the second-stage concentration system has a TDS of 60,000 mg / L and is returned to the water inlet of the first-stage concentration system. The water produced by the first-stage concentration system has a TDS of 16,000 mg / L and is sent to the second-stage reverse osmosis filtration system. The water produced by the second-stage reverse osmosis filtration system meets the standards and is discharged or reused. Among them, the membrane material in the first-stage concentration system and the second-stage concentration system is modified polysulfone membrane A.

[0095] Example 3

[0096] The specific steps of a high calcium hardness short-process evaporation pond concentration reduction method are as follows:

[0097] B1. Before the evaporation pond wastewater with calcium hardness of 2000mg / L, magnesium hardness of 400mg / L and TDS of 53000mg / L is discharged into the two-stage sand filtration system, a composite antiscalant is added at a dosage of 50ppm, and then filtered into the two-stage sand filtration system, and then a composite antiscalant is added at a dosage of 60ppm for preliminary treatment; wherein the composite antiscalant is composed of modified chitin A and chitosan biguanide hydrochloride in a mass ratio of 3:1;

[0098] B2. The wastewater after preliminary treatment is discharged to the nanofiltration system for filtration. The water produced by the nanofiltration system enters the primary concentration system (the desalination rate of the primary concentration system is 71.6%), and the wastewater is concentrated to a concentrated water TDS of 105,000 mg / L at a pressure of 60 bar. Then, the wastewater enters the secondary concentration system (the desalination rate of the secondary concentration system is 43.8%), and the wastewater is concentrated to a concentrated water TDS of 145,000 mg / L at a pressure of 60 bar.

[0099] B3. After the wastewater is concentrated, the water produced by the second-stage concentration system has a TDS of 59,000 mg / L and is returned to the water inlet of the first-stage concentration system. The water produced by the first-stage concentration system has a TDS of 15,000 mg / L and is sent to the second-stage reverse osmosis filtration system. The water produced by the second-stage reverse osmosis filtration system meets the standards and is discharged or reused. Among them, the membrane material in the first-stage concentration system and the second-stage concentration system is modified polysulfone membrane A.

[0100] Example 4

[0101] The specific steps of a high calcium hardness short-process evaporation pond concentration reduction method are as follows:

[0102] B1. Before the evaporation pond wastewater with calcium hardness of 2000mg / L, magnesium hardness of 400mg / L and TDS of 53000mg / L is discharged into the two-stage sand filtration system, a composite antiscalant is added at a dosage of 60ppm, and then filtered into the two-stage sand filtration system, and then a composite antiscalant is added at a dosage of 50ppm for preliminary treatment; wherein the composite antiscalant is composed of modified chitin A and chitosan biguanide hydrochloride in a mass ratio of 4:1;

[0103] B2. The wastewater after preliminary treatment is discharged to the nanofiltration system for filtration. The water produced by the nanofiltration system enters the primary concentration system (the desalination rate of the primary concentration system is 71.6%), and the wastewater is concentrated to a concentrated water TDS of 105,000 mg / L at a pressure of 70 bar. Then, the wastewater enters the secondary concentration system (the desalination rate of the secondary concentration system is 43.8%), and the wastewater is concentrated to a concentrated water TDS of 145,000 mg / L at a pressure of 70 bar.

[0104] B3. After the wastewater is concentrated, the water produced by the second-stage concentration system has a TDS of 59,000 mg / L and is returned to the water inlet of the first-stage concentration system. The water produced by the first-stage concentration system has a TDS of 15,000 mg / L and is sent to the second-stage reverse osmosis filtration system. The water produced by the second-stage reverse osmosis filtration system meets the standards and is discharged or reused. Among them, the membrane material in the first-stage concentration system and the second-stage concentration system is modified polysulfone membrane A.

[0105] Example 5

[0106] A short-process evaporation pond concentration and reduction method with low calcium hardness, the specific implementation method is the same as Example 1, the difference is that the modified chitin A is replaced by an equal amount of modified chitin B.

[0107] Example 6

[0108] A short-process evaporation pond concentration and reduction method with low calcium hardness, the specific implementation method is the same as Example 1, the difference is that the modified chitin A is replaced by an equal amount of modified chitin C.

[0109] Example 7

[0110] A short-process evaporation pond concentration and reduction method with low calcium hardness, the specific implementation method is the same as Example 1 except for the specific numerical values, the difference is that the modified polysulfone membrane B is used instead of the modified polysulfone membrane A.

[0111] Example 8

[0112] A short-process evaporation pond concentration and reduction method with low calcium hardness, the specific implementation method is the same as Example 1 except for the specific numerical values, the difference is that modified polysulfone membrane C is used instead of modified polysulfone membrane A.

[0113] Comparative Example 1

[0114] A short-process evaporation pond concentration and reduction method with low calcium hardness, the specific implementation method is the same as Example 1, the difference is that an equal amount of chitin is used to replace the composite scale inhibitor.

[0115] Comparative Example 2

[0116] The specific steps of a short-process evaporation pond concentration and reduction method with low calcium hardness are as follows:

[0117] A1. The evaporation pond wastewater with a calcium hardness of 400 mg / L, a magnesium hardness of 100 mg / L, and a TDS of 53000 mg / L is discharged to a two-stage sand filtration system for filtration, and a composite scale inhibitor is added at a dosage of 10 ppm for preliminary treatment; wherein the composite scale inhibitor is composed of modified chitin A and chitosan biguanide hydrochloride in a mass ratio of 3:1;

[0118] A2. The wastewater after preliminary treatment is discharged to the primary concentration system (the desalination rate of the primary concentration system is 97%), and the wastewater can only be concentrated to a concentrated water TDS of 80,000 mg / L under a pressure of 60 bar. The concentrated water TDS of 80,000 mg / L then enters the secondary concentration system (the desalination rate of the secondary concentration system is 95%), and the wastewater is concentrated to a concentrated water TDS of 1,200,000 mg / L under a pressure of 110 bar.

[0119] A3. After the wastewater is concentrated, the water produced by the secondary concentration system has a TDS of 4000 mg / L and is returned to the water inlet of the primary concentration system. The water produced by the primary concentration system has a TDS of 1590 mg / L and is sent to the secondary reverse osmosis filtration system. The water produced by the secondary reverse osmosis filtration system meets the standards and is discharged or reused. Among them, the membrane materials in the primary concentration system and the secondary concentration system are commercially available polyamide membranes.

[0120] Example 9

[0121] A short-process evaporation pond concentration and reduction method with high calcium hardness, the specific implementation method is the same as Example 3, the difference is that the modified chitin A is replaced by an equal amount of modified chitin B.

[0122] Example 10

[0123] A short-process evaporation pond concentration and reduction method with high calcium hardness, the specific implementation method is the same as Example 3, the difference is that an equal amount of modified chitin C is used to replace modified chitin A.

[0124] Embodiment 11

[0125] A method for concentrating and reducing the amount of calcium hardness in a short-process evaporation pond is disclosed. The specific implementation method is the same as that of Example 3 except for the specific numerical values, and the difference is that the modified polysulfone membrane B is used instead of the modified polysulfone membrane A.

[0126] Example 12

[0127] A method for concentrating and reducing the amount of calcium hardness in a short-process evaporation pond is disclosed. The specific implementation method is the same as that of Example 3 except for the specific numerical values, and the difference is that the modified polysulfone membrane C is used instead of the modified polysulfone membrane A.

[0128] Comparative Example 3

[0129] A method for concentrating and reducing the amount of calcium hardness in a short-process evaporation pond is disclosed. The specific implementation method is the same as that of Example 3, except that an equal amount of chitin is used to replace the composite scale inhibitor.

[0130] Comparative Example 4

[0131] The specific steps of a high calcium hardness short-process evaporation pond concentration reduction method are as follows:

[0132] B1. Before the evaporation pond wastewater with calcium hardness of 2000mg / L, magnesium hardness of 400mg / L and TDS of 53000mg / L is discharged into the two-stage sand filtration system, a composite antiscalant is added at a dosage of 50ppm, and then filtered into the two-stage sand filtration system, and then a composite antiscalant is added at a dosage of 60ppm for preliminary treatment; wherein the composite antiscalant is composed of modified chitin A and chitosan biguanide hydrochloride in a mass ratio of 3:1;

[0133] B2. The wastewater after preliminary treatment is discharged to the nanofiltration system for filtration. The water produced by the nanofiltration system enters the primary concentration system (the desalination rate of the primary concentration system is 97%), and the wastewater is concentrated to a concentrated water TDS of 80,000 mg / L at a pressure of 60 bar. Then, the wastewater enters the secondary concentration system (the desalination rate of the secondary concentration system is 95%), and the wastewater is concentrated to a concentrated water TDS of 1,200,000 mg / L at a pressure of 60 bar.

[0134] B3. After the wastewater is concentrated, the water produced by the second-stage concentration system has a TDS of 4000 mg / L and is returned to the water inlet of the first-stage concentration system. The water produced by the first-stage concentration system has a TDS of 1590 mg / L and is sent to the second-stage reverse osmosis filtration system. The water produced by the second-stage reverse osmosis filtration system meets the standards and is discharged or reused. Among them, the membrane materials in the first-stage concentration system and the second-stage concentration system are commercially available polyamide membranes.

[0135] Effect evaluation:

[0136] The above-mentioned Examples 1-12 and Comparative Examples 1-4 were evaluated and measured, and the specific analysis is as follows.

[0137] Performance Testing:

[0138] 1) It was found through testing that the water production of Examples 1-4, which used scale inhibitors in the short-process evaporation pond concentration and reduction method, did not change significantly after running for 3 weeks, while the water production of Examples 5-6, 9-10 and Comparative Examples 1 and 3, which used scale inhibitors beyond the scope of the present invention, quickly decreased. In Examples 5 and 9, modified chitin B was used to replace modified chitin A in equal amounts, which changed the mass ratio of chitin and sodium chloroacetate in the chitin solution, and the degree of substitution of the carboxyl group was reduced; in Examples 6 and 10, modified chitin C was used to replace modified chitin A in equal amounts, which changed the mass ratio of carboxymethyl chitin and 3,4,5-trihydroxybenzoic acid, and the chelating effect was weakened, so that Examples 5-6 and 9-10 could only maintain the water production unchanged for 10-12 days.

[0139] Comparative Examples 1 and 3 can only last for 3-4 days, and the water production on the fifth day even drops by nearly 30%.

[0140] 2) The modified polysulfone membrane used in Examples 1-4 has a moderate desalination rate and can achieve the purpose of low-pressure high-fold concentration, while Examples 7-8, 11-12 and Comparative Examples 1 and 3 use modified polysulfone membranes beyond the scope of the present invention. In Examples 7 and 11, modified polysulfone membrane B is used to replace modified polysulfone membrane A, and the mass ratio of m-phenylenediamine, fenpyraclostrobin and camphorsulfonic acid is changed, the interfacial polymerization is weakened, and the density is poor. In Examples 8 and 12, modified polysulfone membrane C is used to replace modified polysulfone membrane A, and fenpyraclostrobin modified polysulfone membrane is not added, and biological pollution is significantly increased. The desalination rate of the primary concentration system is less than 50%, which makes the desalination rate substandard and it is difficult to achieve the purpose of low-pressure high-fold concentration.

[0141] Comparative Examples 2 and 4 use unmodified commercially available polyamide membranes to replace modified polysulfone membrane A. From the specific data, the desalination rate is too high and does not meet the demand.

[0142] The above is only a preferred embodiment of the present invention and does not constitute any form of limitation to the present application. Although the present application is disclosed as above in the preferred embodiment, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution.

Claims

1. A method for concentration and reduction of short-process evaporation ponds, characterized in that: The short-process evaporation pond concentration and reduction method comprises the following steps: S1. Preliminary treatment of wastewater from evaporation ponds using sand filtration system and composite antiscalant; S2. The wastewater after preliminary treatment is concentrated by the primary concentration system, and then enters the secondary concentration system to concentrate the wastewater; S3. After the wastewater is concentrated, the water produced by the second-stage concentration system is returned to the water inlet of the first-stage concentration system, and the water produced by the first-stage concentration system is sent to the second-stage reverse osmosis filtration system. The water produced by the second-stage reverse osmosis filtration system meets the standards and is discharged or reused; among them, the membrane material in the first-stage concentration system is a modified polysulfone membrane; The method can be divided into a short-process evaporation pond concentration and reduction method with low calcium hardness and a short-process evaporation pond concentration and reduction method with high calcium hardness; wherein, in the S2 step of the short-process evaporation pond concentration and reduction method with high calcium hardness, the wastewater after preliminary treatment is first discharged to a nanofiltration system for filtration, and the nanofiltration system produces water before entering a primary concentration system for concentration; low calcium hardness corresponds to a brine calcium hardness of less than 1500 mg / L, and high calcium hardness corresponds to a brine calcium hardness of greater than 1500 mg / L; The composite scale inhibitor is modified chitin and chitosan biguanide hydrochloride, and the mass ratio of the two is (2-4): 1; The preparation method of the modified chitin comprises the following steps: (1) mixing chitin, a 10-15 wt% sodium hydroxide aqueous solution, and a 3-6 wt% urea aqueous solution, and performing a freeze-thaw process to obtain a chitin solution; (2) adding the chitin solution and sodium chloroacetate obtained in step (1) into a reaction kettle, stirring and reacting at 5-15° C. for 72-96 hours, adjusting the pH value to neutral, dialyzing, and drying to obtain carboxymethyl chitin; (3) adding the carboxymethyl chitin, 3,4,5-trihydroxybenzoic acid and water obtained in step (2) into a reactor, introducing an inert gas, adding a 25-40 wt% aqueous solution of hydrogen peroxide, stirring and reacting at 65-80° C. for 4-6 h, adding anhydrous ethanol for precipitation and separation, and drying to obtain modified chitin; The preparation method of the modified polysulfone membrane comprises the following steps: Q1. Mix attapulgite and water, ultrasonically disperse for 24-48 hours, add octadecyltrimethylammonium chloride and sodium dodecyl sulfate, ultrasonically disperse for 30-60 minutes, centrifuge, and take the supernatant to obtain a solution; Q2. Mix m-phenylenediamine, fenpyraclostrobin, camphorsulfonic acid and water, add an organic base to adjust the pH to 9-10.5, stir to obtain a liquid; add the solution obtained in step Q1, ultrasonically treat to obtain an aqueous phase solution, and set aside; mix the aromatic polyacyl chloride and the organic solvent, ultrasonically treat to obtain an oil phase solution, and set aside; Q3. Take out the polysulfone membrane and fix it on a flat plate, pour the aqueous solution obtained in step Q2 on the surface of the polysulfone membrane and soak it for 3-8 minutes, pour out the excess aqueous solution, dry it, then pour the oil solution obtained in step Q2 on the surface of the polysulfone membrane and soak it for 0.5-1.5 minutes, pour out the excess oil solution, let it stand vertically to drain for 15-30 seconds, and dry it to obtain a modified polysulfone membrane.

2. The method for concentration and reduction of a short-process evaporation pond according to claim 1, characterized in that: The specific steps of the short-process evaporation pond concentration and reduction method with low calcium hardness are as follows: A1. The wastewater from the evaporation pond is discharged to a two-stage sand filtration system for filtration, and a composite antiscalant is added for preliminary treatment; A2. The wastewater after preliminary treatment is discharged to the primary concentration system, where it is concentrated at a pressure of 60-70 bar, and then enters the secondary concentration system where it is concentrated at a pressure of 60-70 bar; A3. After the wastewater is concentrated, the water produced by the second-stage concentration system is returned to the water inlet of the first-stage concentration system. The water produced by the first-stage concentration system is sent to the second-stage reverse osmosis filtration system. The water produced by the second-stage reverse osmosis filtration system meets the standards and is discharged or reused.

3. The method for concentration and reduction of a short-process evaporation pond according to claim 1, characterized in that: The specific steps of the high calcium hardness short-process evaporation pond concentration and reduction method are as follows: B1. Add composite antiscalant before the wastewater from the evaporation pond is discharged into the two-stage sand filtration system, filter it into the two-stage sand filtration system, and then add composite antiscalant for preliminary treatment; B2. The wastewater after preliminary treatment is discharged to the nanofiltration system for filtration. The water produced by the nanofiltration system enters the primary concentration system to concentrate the wastewater at a pressure of 60-70 bar, and then enters the secondary concentration system to concentrate the wastewater at a pressure of 60-70 bar; B3. After the wastewater is concentrated, the water produced by the second-stage concentration system is returned to the water inlet of the first-stage concentration system. The water produced by the first-stage concentration system is sent to the second-stage reverse osmosis filtration system. The water produced by the second-stage reverse osmosis filtration system meets the standards and is discharged or reused.

4. The method for concentration and reduction of a short-process evaporation pond according to claim 1, characterized in that: The mass ratio of chitin to sodium chloroacetate in the chitin solution in step (2) is 1:(2-3).

5. The method for concentration and reduction of a short-process evaporation pond according to claim 1, characterized in that: The mass ratio of carboxymethyl chitin to 3,4,5-trihydroxybenzoic acid in step (3) is 1:(0.8-1.6).

6. The method for concentration and reduction of a short-process evaporation pond according to claim 1, characterized in that: The mass ratio of m-phenylenediamine, fenpyraclostrobin and camphorsulfonic acid in step Q2 is 10:(1.5-3):(18-25).

7. A system using the method for concentration and reduction of short-process evaporation ponds according to any one of claims 1 to 6, characterized in that: The short-process evaporation pond concentration and reduction with low calcium hardness includes the following systems: sand filtration system, primary concentration system, two-stage concentration system, and two-stage reverse osmosis filtration system; the short-process evaporation pond concentration and reduction with high calcium hardness includes the following systems: sand filtration system, nanofiltration system, primary concentration system, two-stage concentration system, and two-stage reverse osmosis filtration system.