Optimization method for hardness removal of strong brine based on double-alkali hardness removal method

Abstract

The invention belongs to the technical field of strong brine hardness removal, and particularly relates to an optimization method for strong brine hardness removal based on a double-alkali hardness removal method. The method comprises the following steps: (1) introducing to-be-treated strong brine containing a scale inhibitor into a destabilization pool for destabilization; the destabilizing agent is selected from one or more of nano zero-valent iron, metal oxyhydroxide, potassium permanganate, persulfate and hydrogen peroxide; (2) introducing the effluent of the destabilization tank into a reaction tank 1 added with an alkali agent for treatment; (3) introducing the effluent of the reaction tank 1 into a reaction tank 2 added with sodium carbonate for treatment; (4) introducing effluent of the reaction tank 2 into a reaction tank 3 added with a coagulant aid and a flocculating agent for treatment; and carrying out solid-liquid separation and concentration to obtain the effluent after the hardness of the strong brine is removed. According to the method, stable complex bonds between the scale inhibitor and hardness ions can be broken, scale inhibitor components in the strong brine with complex components are removed, the subsequent softening and hardness removal efficiency is improved, and the addition amount of a strong brine softening agent and the generation amount of sludge are reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of concentrated brine hardness removal, and particularly relates to a concentrated brine hardness removal optimization method based on a double-alkali hardness removal method. BACKGROUND

[0002] The concentrated brine softening and hardness removal methods in the field include a double-alkali softening method, an ion exchange resin method and an induced crystallization method. The double-alkali softening method is to add calcium hydroxide or sodium hydroxide and sodium carbonate into water, and simultaneously add a coagulant, so as to remove Ca 2+ , Mg 2+ ions through chemical precipitation and flocculation. The ion exchange resin method removes hardness by exchanging Ca 2+ , Mg 2+ ions on the surface of the resin with other cations. The induced crystallization method is to add crystal seeds on the basis of the precipitation method, so that calcium and magnesium crystals are attached to the surface of the induced crystal carrier, and the crystal seeds are separated after growing.

[0003] Concentrated brine is generated in the process of high-ratio multi-stage concentration of mine water, and the concentrations of Ca 2+ , Mg 2+ ions in the original mine water also increase with the concentration. In order to avoid the scaling and precipitation of Ca 2+ , Mg 2+ ions in the membrane system, a scale inhibitor is usually added into the water before entering the membrane system. The addition of the scale inhibitor effectively avoids scaling, but increases the difficulty of deep hardness removal of the concentrated brine. In the existing mine water zero discharge process, it is found that the actual amount of the added agent in the deep hardness removal process is greater than the theoretical value, which is related to the complexation of the scale inhibitor with Ca 2+ , Mg 2+ .

[0004] The existing double-alkali softening method and ion exchange hardness removal method do not consider the hindering effect of the scale inhibitor in the concentrated brine on the conversion of Ca 2+ , Mg 2+ into precipitates, and in the actual engineering application, the consumption of the double-alkali agent in the hardness removal of the concentrated brine with complex components is greater than the theoretical value, the hardness removal effect is unstable, and a large amount of sludge is produced, which is related to the complexation hindering effect of the scale inhibitor.

[0005] In the high-mineralization high-hardness mine water concentration and desalination process, in order to ensure the stable operation of the reverse osmosis system, the mine water is simply pretreated and a scale inhibitor is added, and the scale inhibitor remains in the concentrated brine. Therefore, how to solve the adverse effect of the residual scale inhibitor in the concentrated brine softening and hardness removal process on the treatment effect is a direction worthy of research. SUMMARY

[0006] The present application aims at solving the technical problem of difficulty in deep hardness removal of concentrated brine caused by complexation of scale inhibitors with calcium and magnesium ions, and provides a method for softening and removing hardness of concentrated brine with complex components, and proposes adding a destabilization process before softening and removing hardness of concentrated brine, breaking the stable complex bond between scale inhibitors and hardness ions (Ca 2+ , Mg 2+ ), removing scale inhibitor components in concentrated brine with complex components, improving the efficiency of subsequent softening and hardness removal, and effectively reducing the addition amount of softening agent and sludge production of concentrated brine.

[0007] In order to achieve the above-mentioned purpose, the present application provides the following technical scheme:

[0008] An optimization method for removing hardness of concentrated brine based on a double-alkali hardness removal method, comprising the following steps:

[0009] (1) passing the concentrated brine to be treated containing scale inhibitors into a destabilization tank, and adding a destabilization agent in the tank for destabilization treatment; the destabilization agent (a compound having adsorption, complexation, oxidation or reduction effect on scale inhibitors) is selected from one or more of nano zero-valent iron, metal hydroxyl oxide, potassium permanganate, persulfate and hydrogen peroxide;

[0010] (2) passing the effluent of the destabilization tank into a reaction tank 1 for treatment; an alkali agent is added in the reaction tank 1;

[0011] (3) passing the effluent of the reaction tank 1 into a reaction tank 2 for treatment; sodium carbonate is added in the reaction tank 2, so that Ca 2+ , Mg 2+ , scale inhibitors and destabilization agents in the concentrated brine form a co-precipitate;

[0012] (4) passing the effluent of the reaction tank 2 into a reaction tank 3 for treatment; a coagulant and a flocculant are added in the reaction tank 3, so that the precipitate in the concentrated brine forms large floc particles; after solid-liquid separation and concentration, the concentrated brine containing large floc particles obtains effluent after hardness removal.

[0013] In this paper, a dosing system can be arranged in the destabilization tank, for example, including: a reagent storage tank, a dosing pipe and a matching instrument valve, etc., and the type of destabilization agent is selected according to the main component characteristics of scale inhibitors.

[0014] The main components of scale inhibitors contained in the concentrated brine to be treated include one or more of organic phosphate substances, inorganic phosphate substances, nitrite substances and natural easily degradable dispersants.

[0015] In the present application, the destabilization agent is a compound having adsorption, complexation, oxidation, reduction and other effects on scale inhibitors, and the destabilization agent in liquid or suspension form can be selected for addition. In the destabilization tank, due to the addition of the destabilization agent, the scale inhibitors and Ca 2+, Mg 2+ The chemical bond between Ca

[0016] According to the optimization method provided by the application, in some embodiments, the metal hydroxyl oxide is selected from one or more of FeOOH, AlOOH, LaOOH, Mg(OH)2, and a metal organic framework material. For example, the metal hydroxyl oxide can also be an aluminum-iron composite hydroxyl oxide composed of FeOOH and AlOOH, an aluminum-magnesium composite hydroxyl oxide composed of AlOOH and Mg(OH)2, or a magnesium-iron composite hydroxyl oxide composed of FeOOH and Mg(OH)2. The metal organic framework material can be a Fe-Zr bimetallic organic framework.

[0017] In some embodiments, in step (1), the residence time of the concentrated brine to be treated in the destabilization tank is 20-60 min, for example, 22 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, or 55 min.

[0018] The amount of the destabilization agent is controlled according to the content of the scale inhibitor or characteristic functional group in the concentrated brine, so that the destabilization agent adsorbs the scale inhibitor and breaks the chemical bond between Ca 2+ , Mg 2+ In some embodiments, in step (1), the molar ratio of the amount of the destabilization agent to the total amount of phosphonic groups and carboxylic groups in the concentrated brine to be treated is 0.8-2, for example, 0.9, 1.0, 1.2, 1.4, 1.5, 1.6, or 1.8.

[0019] According to the optimization method provided by the application, the reaction tank 1 can be provided with a dosing system, including a reagent storage tank, a dosing pipe, and a matching instrument valve, etc. One dosing port is arranged to add the alkaline reagent to the concentrated brine. A stirring device can also be arranged in the reaction tank 1 to fully mix the reagent and the concentrated brine.

[0020] In some embodiments, in step (2), the alkaline reagent is an alkaline substance, which is preferably selected from calcium hydroxide and / or sodium hydroxide.

[0021] In some embodiments, in step (2), the pH value of the system is controlled to be in the range of 10.5-11.7, for example, 10.8, 11, 11.2, 11.4, 11.5, or 11.6, by adding the amount of the alkaline reagent.

[0022] In some implementations, in step (2), the effluent from the destabilizing tank stays in the reaction tank 1 for 15 to 40 minutes, for example, 16 minutes, 18 minutes, 20 minutes, 25 minutes, 30 minutes, or 35 minutes.

[0023] According to the optimization method provided by the present invention, a dosing system can be set in the reaction tank 2, including: a reagent storage tank, a dosing pipe and supporting instrument valves, etc., and a dosing port is set to add sodium carbonate to the concentrated brine.

[0024] The amount of sodium carbonate added and Ca 2+ Concentration-dependent; by adding sodium carbonate, the Ca in concentrated brine can be reduced. 2+ Mg 2 + Scale inhibitors and destabilizers form co-precipitates. Due to the addition of destabilizers, the amount of sodium carbonate added is lower than the actual amount added during the operation of the dual-alkali process.

[0025] In some implementation schemes, in step (3), the amount of sodium carbonate used is related to the amount of Ca contained in the system. 2+ The molar ratio is 1 to 1.5, for example, 1.1, 1.2, 1.3, 1.4, 1.45.

[0026] Adding coagulant and flocculant to reaction tank 3 can cause the precipitate to form large floc particles; concentrated brine containing large floc particles is separated into solid and liquid in a solid-liquid separator, which can also be designed as an integral part of reaction tank 3.

[0027] In some implementations, in step (4), the coagulant is selected from polyferric sulfate; based on a flow rate of 1L of concentrated brine to be treated, the concentration of the coagulant is 10-200mg / L (e.g., 12mg / L, 15mg / L, 20mg / L, 30mg / L, 50mg / L, 80mg / L, 100mg / L, 120mg / L, 150mg / L, 180mg / L); after adding the coagulant, the residence time of the material in the reaction tank 3 is 5-60min (e.g., 6min, 8min, 10min, 15min, 20min, 30min, 40min, 50min).

[0028] In some embodiments, in step (4), the flocculating agent is selected from polyacrylamide; the amount of the flocculating agent is 1-10 mg / L (e.g., 2 mg / L, 4 mg / L, 5 mg / L, 8 mg / L, 9 mg / L) based on 1 L of the concentrated brine to be treated; and after the flocculating agent is added, the residence time of the material in the reaction tank 3 is 10-180 min (e.g., 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 50 min, 60 min, 80 min, 100 min, 120 min, 150 min).

[0029] In some embodiments, the concentrated brine containing large floc particles is subjected to solid-liquid separation in a solid-liquid separator, and then the filtrate obtained by the solid-liquid separation is subjected to pH adjustment by adding an acid and then enters a subsequent re-concentration process to obtain effluent after hardness removal of the concentrated brine; and the precipitate obtained by the solid-liquid separation is disposed as general solid waste.

[0030] The present application has little modification to the existing double-alkali softening process, and only needs to add a dosing system containing a destabilizing agent at the front end of the original reaction tank to perform a destabilization pretreatment process, so as to break the complexation force between the scale inhibitor and hardness ions (Ca 2+ , Mg 2+ ), eliminate the influence of the scale inhibitor in the complex component concentrated brine in the softening process, and promote the efficient conversion of the hardness ions into a precipitated form. Through the method of the present application, the scale inhibitor added in the concentrated brine is transferred to the precipitate in the double-alkali hardness removal process, and there is no residual agent in the concentrated brine.

[0031] Compared with the conventional double-alkali softening process, the method proposed in the present application can solve the technical problems of large actual consumption of double-alkali agents and unstable hardness removal effect during hardness removal of complex component concentrated brine, break the stable complex bond between the scale inhibitor and hardness ions (Ca 2+ , Mg 2+ ), remove the scale inhibitor component in the complex component concentrated brine, and improve the subsequent softening and hardness removal efficiency; at the same time, the method also effectively reduces the amount of softening sludge and the amount of softening agent added in the concentrated brine, reduces the agent use cost and operation and maintenance cost, and achieves the treatment goal of deep hardness removal of complex component concentrated brine. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 The figure shows the schematic flow of the optimization method for hardness removal of concentrated brine based on the double-alkali hardness removal method according to some embodiments of the present application. DETAILED DESCRIPTION

[0033] In order to enable a detailed understanding of the technical features and content of the present application, preferred embodiments of the present application will be described in more detail below. Although preferred embodiments of the present application are described in the examples, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein.

[0034] The experimental procedures used in the following examples are conventional methods unless otherwise specified.

[0035] The materials, reagents, etc. used in the following examples can be obtained commercially.

[0036] Among them, the concentrated brine containing scale inhibitor is from the concentrated brine produced by reverse osmosis in the zero discharge process of a western mine. The water quality is shown in Table 1. Note: In order to avoid scale formation on the reverse osmosis concentrated water side, the American Dow Acusol 445N scale inhibitor was added at the front end of the reverse osmosis process.

[0037] Table 1 Water quality indicators of the concentrated brine to be treated

[0038]

[0039]

[0040] In the following examples and comparative examples, the destabilizing agent used is self-made.

[0041] Preparation Example 1 of the destabilizing agent:

[0042] Prepare a 3 mol / L Fe(NO3)2 aqueous solution and a 1 mol / L NaOH aqueous solution; add the prepared NaOH aqueous solution to the 500 mL prepared Fe(NO3)2 aqueous solution at a flow rate of 10 ml / min, accompanied by rapid stirring, control the final pH value of the system to be 12 by the amount of NaOH aqueous solution added, then stop adding raw materials and continue stirring for 30 min; then transfer the obtained liquid to a polytetrafluoroethylene lined autoclave, and hydrothermal reaction at 200℃ for 12h; then naturally cool down; take out the yellow product and repeatedly clean to obtain a nanoscale FeOOH suspension.

[0043] Preparation Example 2 of the destabilizing agent:

[0044] A 1 mol / L NaOH aqueous solution was prepared, and a mixed salt aqueous solution containing 1 mol / L Al(NO3)3 and 2 mol / L Fe(NO3)2 was prepared; 500 mL of the prepared mixed salt aqueous solution was taken and heated in a 120°C oil bath, and the prepared 1 mol / L NaOH aqueous solution was slowly added to the mixed salt aqueous solution at a flow rate of 10 ml / min, with rapid stirring; the end-point pH value of the system was controlled to be 11.5 by the amount of the added NaOH aqueous solution, then the addition of the raw material was stopped and stirring was continued for 30 min; after natural cooling, the white product was taken out and repeatedly washed to obtain an aluminum-iron composite hydroxyl oxide suspension.

[0045] Preparation Example 3 of the destabilizing agent:

[0046] A 1 mol / L NaOH aqueous solution was prepared, and a mixed salt aqueous solution containing 1 mol / L Al(NO3)3 and 2 mol / L Mg(NO3)2 was prepared; 500 mL of the mixed salt aqueous solution was taken and heated in a 120°C oil bath, and the prepared 1 mol / L NaOH aqueous solution was slowly added to the mixed salt aqueous solution at a flow rate of 10 ml / min, with rapid stirring; the end-point pH value of the system was controlled to be 11.5 by the amount of the added NaOH aqueous solution, then the addition of the raw material was stopped and stirring was continued for 30 min; after natural cooling, the white product was taken out and repeatedly washed to obtain an aluminum-iron composite hydroxyl oxide suspension.

[0047] Preparation Example 4 of the destabilizing agent:

[0048] FeCl3 and ZrCl4 were dissolved in a N,N'-dimethylformamide solvent to prepare a mixed salt solution, wherein the molar concentrations of FeCl3 and ZrCl4 were both 0.1 mol / L; 500 mL of the prepared mixed salt solution was taken and polyvinylpyrrolidone was added thereto, the concentration of the polyvinylpyrrolidone was controlled to be 50 g / L by controlling the amount of the polyvinylpyrrolidone added, and the mixture was fully stirred to dissolve and ultrasonic dispersed for 10 min; the obtained liquid was transferred to a polytetrafluoroethylene-lined autoclave, and hydrothermal reaction was performed at 160°C for 24 h; after natural cooling, the obtained product was washed with ethanol for 5 times, then the precipitate was taken out and dried at 105°C for 12 h, and the obtained powder was dispersed in pure water to obtain a Fe-Zr bimetallic organic framework suspension with a concentration of 200 g / L.

[0049] Example 1:

[0050] Based on the optimization method of the double-alkali softening method, the Ca 2+ , Mg 2+ , refer to Figure 1The process flow shown, the steps are as follows:

[0051] (1) The concentrated brine to be treated shown in Table 1 is added into the destabilization tank at a flow rate of 0.1 m 3 / h, and a destabilizing agent is added into the destabilization tank; the destabilization tank is provided with one set of dosing system, including: a reagent storage tank, a dosing pipe and matching instrument valves, and one dosing port is provided;

[0052] The destabilizing agent is the product (nano FeOOH suspension) prepared in Preparation Example 1 above, which can complex and adsorb the phosphoric acid group and carboxylic acid group containing scale inhibitors in the concentrated brine;

[0053] The molar ratio of the destabilizing agent to the total of the phosphoric acid group and carboxylic acid group in the concentrated brine is 1.8:1; the reaction time for adding the destabilizing agent is 20 minutes (i.e. the residence time of the concentrated brine in the destabilization tank);

[0054] (2) The effluent of the destabilization tank is added into the reaction tank 1, and an aqueous sodium hydroxide solution is added into the concentrated brine in the reaction tank 1; the reaction tank 1 is provided with a dosing system, including: a reagent storage tank, a dosing pipe and matching instrument valves, and one dosing port is provided; a stirring device is further provided in the reaction tank 1 to fully mix the reagent and the concentrated brine;

[0055] The amount of the aqueous sodium hydroxide solution added into the concentrated brine is controlled to adjust the pH of the system to 11.2; the hydraulic residence time in the reaction tank 1 is 20 minutes (i.e. the residence time of the effluent of the destabilization tank in the reaction tank 1);

[0056] (3) The effluent of the reaction tank 1 is added into the reaction tank 2, and sodium carbonate is added into the concentrated brine in the reaction tank 2; the reaction tank 2 is provided with a dosing system, including: a reagent storage tank, a dosing pipe and matching instrument valves, and one dosing port is provided; a stirring device is further provided in the reaction tank 2 to fully mix the reagent and the concentrated brine;

[0057] The molar ratio of the amount of sodium carbonate added to Ca 2+ is 1:1; Ca 2+ , Mg 2+ , scale inhibitors and the destabilizing agent in the concentrated brine form a co-precipitate;

[0058] Without adding the destabilizing agent in the concentrated brine, the amount of the hardening agent (sodium carbonate) added in the concentrated brine is generally 0.2-0.5 times of the excess addition ratio (the molar ratio of the amount of sodium carbonate added to Ca 2+ is 1:1.2-1.5); compared with the amount of the hardening agent added in the actual double-alkali method, the amount of the hardening agent added in this embodiment is reduced due to the addition of the destabilizing agent;

[0059] (4) The effluent of the reaction tank 2 is added into the reaction tank 3; the reaction tank 3 is divided into a coagulation zone and a flocculation zone;

[0060] Polyferric sulfate is first added to the coagulation zone of the reaction tank 3, the dosage concentration of which is 10 mg / L (based on the inflow of the concentrated brine to be treated as 1 L), fast stirring, hydraulic retention time 5 minutes; then polyacrylamide is added to the flocculation zone of the reaction tank 3, the dosage concentration of which is 1.5 mg / L (based on the inflow of the concentrated brine to be treated as 1 L), slow stirring, hydraulic retention time 20 minutes; the complex of the antifouling agent and the scale inhibitor in the concentrated brine, Ca 2+ , Mg 2+ form large floc particles;

[0061] (5) The concentrated brine containing large floc particles enters the solid-liquid separator to realize solid-liquid separation; the clear water obtained after the solid-liquid separation enters the subsequent re-concentration process after being adjusted in pH value (i.e. the pH value of the effluent water quality shown in the table) by adding acid (such as dilute hydrochloric acid), to obtain effluent water after hardness removal; the precipitate obtained after the solid-liquid separation is disposed as general solid waste.

[0062] The effluent water quality of the concentrated brine after hardness removal is shown in Table 2:

[0063] Table 2 Effluent water quality after hardness removal

[0064]

[0065]

[0066] As can be seen from the effluent water quality, the removal rates of Ca 2+ , Mg 2+ in the concentrated brine after hardness removal are 97.4% and 93.8% respectively, and the removal rates of TOC, total phosphorus and silicon are 95.21%, 98.13% and 76.38% respectively.

[0067] Example 2:

[0068] The optimization method of the concentrated brine hardness removal based on the double-alkali hardness removal method removes Ca 2+ , Mg 2+ in the original concentrated brine, and the process flow is shown in Table 3, and the steps are as follows: Figure 1

[0069] (1) The concentrated brine to be treated shown in Table 1 enters the destabilization tank at a flow rate of 0.1 m 3 / h, and a destabilizing agent is added to the destabilization tank; the destabilization tank is provided with one set of dosing system, including: a reagent storage tank, a dosing pipe and a matching instrument valve, and one dosing port is provided;

[0070] The destabilizing agent is the product (aluminum-iron composite hydroxyl oxide suspension) prepared in Preparation Example 2 above, which can complex and adsorb the phosphoric acid group and carboxylic acid group of the antifouling agent in the concentrated brine; ​

[0071] The molar ratio of the breaker to the total of phosphoric acid groups and carboxylic acid groups in the concentrated brine is 1.0:1; the reaction time for adding the breaker is 20 minutes (i.e., the residence time of the concentrated brine in the breaker tank);

[0072] (2) The effluent of the breaker tank enters the reaction tank 1, and an aqueous sodium hydroxide solution is added to the concentrated brine in the reaction tank 1; wherein the reaction tank 1 is provided with a dosing system, including: a reagent storage tank, a dosing pipe and a matching instrument valve, and one dosing port is provided; the reaction tank 1 is also provided with a stirring device to fully mix the reagent and the concentrated brine;

[0073] By controlling the amount of the aqueous sodium hydroxide solution added to the concentrated brine, the pH of the system is adjusted to 11.0; the hydraulic retention time in the reaction tank 1 is 30 minutes (i.e., the residence time of the effluent of the breaker tank in the reaction tank 1);

[0074] (3) The effluent of the reaction tank 1 enters the reaction tank 2; sodium carbonate is added to the concentrated brine in the reaction tank 2; wherein the reaction tank 2 is provided with a dosing system, including: a reagent storage tank, a dosing pipe and a matching instrument valve, and one dosing port is provided, and the reaction tank 2 is also provided with a stirring device to fully mix the reagent and the concentrated brine;

[0075] The molar ratio of the amount of sodium carbonate to Ca 2+ is 1:1; the Ca 2+ , Mg 2+ , scale inhibitor and breaker in the concentrated brine form a co-precipitate;

[0076] Without the breaker, the dosage of the hardening agent (sodium carbonate) in the concentrated brine is generally 0.2-0.5 times the excess dosage (the molar ratio of the dosage of sodium carbonate to Ca 2+ is 1:1.2-1.5); compared with the dosage during the actual double-alkali method, the dosage of sodium carbonate is reduced in this embodiment due to the addition of the breaker;

[0077] (4) The effluent of the reaction tank 2 enters the reaction tank 3; wherein the reaction tank 3 is divided into a coagulation zone and a flocculation zone;

[0078] First, polymeric ferric sulfate is added to the coagulation zone of the reaction tank 3, and the dosage concentration is 10 mg / L (based on the inflow of 1 L of the concentrated brine to be treated); fast stirring is performed, and the hydraulic retention time is 5 minutes; then, polyacrylamide is added to the flocculation zone of the reaction tank 3, and the dosage concentration is 1.5 mg / L (based on the inflow of 1 L of the concentrated brine to be treated); slow stirring is performed, and the hydraulic retention time is 20 minutes; the breaker and the scale inhibitor complex, Ca 2+ , Mg 2+ in the concentrated brine form large floc particles;

[0079] (5) The concentrated brine containing large floc particles is introduced into a solid-liquid separator to realize solid-liquid separation; the clear water obtained after the solid-liquid separation is introduced into a subsequent re-concentration process after being adjusted in pH value (i.e. the pH value shown in the table for the effluent water quality) by adding acid (e.g. dilute hydrochloric acid) to obtain effluent water after hardness removal; the precipitate obtained after the solid-liquid separation is disposed as general solid waste.

[0080] The effluent water quality of the concentrated brine after hardness removal is shown in Table 3:

[0081] Table 3 Effluent water quality after hardness removal

[0082]

[0083]

[0084] As can be seen from the effluent water quality, the removal rates of Ca 2+ and Mg 2+ in the concentrated brine after hardness removal are 97.6% and 94.1% respectively, and the removal rates of TOC, total phosphorus and silicon are 97.75%, 99.2% and 82.7% respectively.

[0085] Example 3:

[0086] The optimization method for removing Ca 2+ and Mg 2+ from the concentrated brine based on the double-alkali hardness removal method, with reference to the process flow shown in Figure 1 , is as follows:

[0087] (1) The concentrated brine to be treated shown in Table 1 is introduced into a destabilization tank at a flow rate of 0.1 m 3 / h, and then a destabilizing agent is added into the destabilization tank; the destabilization tank is provided with one set of dosing system, including: a reagent storage tank, a dosing pipe and a matching instrument valve, and one dosing port;

[0088] The destabilizing agent is the product (aluminum-magnesium composite hydroxyl oxide suspension) prepared in Preparation Example 3 above, which can complex and adsorb the phosphoric acid groups and carboxylic acid groups of the scale inhibitors in the concentrated brine;

[0089] The molar ratio of the destabilizing agent to the total of the phosphoric acid groups and carboxylic acid groups in the concentrated brine is 1.5:1; the reaction time for adding the destabilizing agent is 30 minutes (i.e. the residence time of the concentrated brine in the destabilization tank);

[0090] (2) The effluent from the destabilization tank is introduced into a reaction tank 1, and an aqueous sodium hydroxide solution is added into the concentrated brine in the reaction tank 1; the reaction tank 1 is provided with a dosing system, including: a reagent storage tank, a dosing pipe and a matching instrument valve, and one dosing port; the reaction tank 1 is also provided with a stirring device to make the reagent and the concentrated brine fully mixed;

[0091] The pH of the system is adjusted to 11.5 by controlling the amount of sodium hydroxide aqueous solution added to the concentrated brine; the hydraulic retention time in the reaction tank 1 is 20 minutes (i.e. the residence time of the effluent from the destabilization tank in the reaction tank 1);

[0092] (3) The effluent from the reaction tank 1 enters the reaction tank 2; sodium carbonate is added to the concentrated brine in the reaction tank 2; wherein the reaction tank 2 is provided with a dosing system, including: a reagent storage tank, a dosing pipe and a matching instrument valve, one dosing port is provided, and the reaction tank 2 is also provided with a stirring device to fully mix the reagent and the concentrated brine;

[0093] The molar ratio of the addition amount of sodium carbonate to Ca 2+ is 1:1; Ca 2+ , Mg 2+ , scale inhibitors and destabilizing agents in the concentrated brine form a co-precipitate;

[0094] Without adding a destabilizing agent to the concentrated brine, the addition amount of hardening removal agent (sodium carbonate) in the concentrated brine is generally 0.2-0.5 times the excess addition ratio (the molar ratio of the addition amount of sodium carbonate to Ca 2+ is 1:1.2-1.5); compared with the addition amount during actual operation of the double-alkali method, the addition amount of sodium carbonate is reduced in this embodiment due to the addition of the destabilizing agent;

[0095] (4) The effluent from the reaction tank 2 enters the reaction tank 3; wherein the reaction tank 3 is divided into a coagulation zone and a flocculation zone;

[0096] Polymeric ferric sulfate is first added to the coagulation zone of the reaction tank 3, the addition amount concentration is 10 mg / L (based on the inflow amount of 1 L of concentrated brine to be treated), rapid stirring, hydraulic retention time 5 minutes; then polyacrylamide is added to the flocculation zone of the reaction tank 3, the addition amount concentration is 1.5 mg / L (based on the inflow amount of 1 L of concentrated brine to be treated), slow stirring, hydraulic retention time 20 minutes; the destabilizing agent and scale inhibitor complex, Ca 2+ , Mg 2+ in the concentrated brine form large floc particles;

[0097] (5) The concentrated brine containing large floc particles enters the solid-liquid separator to realize solid-liquid separation; after the solid-liquid separation, acid (such as dilute hydrochloric acid) is added to the obtained clear water to adjust the pH value (i.e. the pH value shown in the table of effluent water quality), and then the obtained clear water enters the subsequent re-concentration process to obtain effluent water after hardening removal; the obtained precipitate after the solid-liquid separation is disposed as a general solid waste.

[0098] The effluent water quality after the hardening removal of the concentrated brine is shown in Table 4:

[0099] Table 4 Effluent water quality after hardening removal

[0100] Indicator Unit Value Ca 2+ ]]> mg / L 3.1 Mg 2+ ]]> mg / L 2.7 Total Fe mg / L 0.3 Total P (phosphate groups) mg / L 0.4 K + ]]> mg / L 22.1 Na + ]] mg / L 4501.0 Si mg / L 2.42 F - ]]> mg / L 0.95 Cl - ]] mg / L 1121 SO4 2- ]]> mg / L 9275 pH 7.8 CO3 2- ]]> mmol / L 0.57 HCO3 - ]]> mmol / L 20.22 TOC mg / L 3.42 Carboxylic groups mmol / L Not detected

[0101] The water quality results show that the calcium content in the concentrated brine after hardness removal is... 2+ Mg 2+ The removal rates reached 96.89% and 92.04%, respectively, and the removal rates of TOC, total phosphorus, and silicon were 98.58%, 98.41%, and 79.14%, respectively.

[0102] Example 4:

[0103] An optimized method for hardening with concentrated brine based on the dual-alkali hardening process removes Ca from the original concentrated brine. 2+ Mg 2+ , refer to Figure 1 The process flow shown is as follows:

[0104] (1) The concentrated brine to be treated shown in Table 1 is calculated at a flow rate of 0.1 m³ / s. 3 / h enters the destabilization tank; then the destabilizing agent is added to the destabilization tank; wherein, the destabilization tank is equipped with a dosing system, including: agent storage tank, dosing pipe and matching instrument valves, and is equipped with 1 dosing port;

[0105] The destabilizer is the product (Fe-Zr bimetallic organic framework suspension) prepared in Example 4 above, which can complex and adsorb scale inhibitors containing phosphate groups and carboxylic acid groups in concentrated brine.

[0106] The molar ratio of the destabilizing agent to the total number of phosphate and carboxylic acid groups in the concentrated brine is 1.5:1; the reaction time after adding the destabilizing agent is 60 minutes (i.e., the residence time of the concentrated brine in the destabilizing tank);

[0107] (2) The effluent from the destabilizing tank enters the reaction tank 1, and sodium hydroxide aqueous solution is added to the concentrated brine in the reaction tank 1; wherein, the reaction tank 1 is equipped with a dosing system, including: a chemical storage tank, a dosing pipe and matching instrument valves, and a dosing port; the reaction tank 1 is also equipped with a stirring device to ensure that the chemical and the concentrated brine are fully mixed.

[0108] The pH of the system was adjusted to 10.5 by controlling the amount of sodium hydroxide aqueous solution added to the concentrated brine; the hydraulic retention time in reaction tank 1 was 20 minutes (i.e., the retention time of the effluent from the destabilized tank in reaction tank 1);

[0109] (3) The effluent from reaction tank 1 enters reaction tank 2; sodium carbonate is added to the concentrated brine in reaction tank 2; wherein, reaction tank 2 is equipped with a dosing system, including: a chemical storage tank, a dosing pipe and matching instrument valves, and a dosing port; reaction tank 2 is also equipped with a stirring device to ensure that the chemical and concentrated brine are thoroughly mixed.

[0110] Sodium carbonate dosage (Ca) 2+ The molar ratio is 1:1; the Ca in concentrated brine is...2+ , Mg 2+ , scale inhibitor and destabilizer form co-precipitate;

[0111] Without adding destabilizer in the concentrated brine, the dosing amount of hardening agent (sodium carbonate) is generally 0.2-0.5 excess (the molar ratio of sodium carbonate dosing amount to Ca 2+ ; compared with the dosing amount in the actual double alkali method, the dosing amount of sodium carbonate is reduced due to the addition of destabilizer in this embodiment;

[0112] (4) The effluent of reaction tank 2 enters reaction tank 3; wherein, reaction tank 3 is divided into coagulation zone and flocculation zone;

[0113] First, add polymeric ferric sulfate to the coagulation zone of reaction tank 3, the dosing amount concentration is 10 mg / L (based on the inflow amount of 1 L of concentrated brine to be treated as the benchmark), fast stirring, hydraulic retention time 5 minutes; then add polyacrylamide to the flocculation zone of reaction tank 3, the dosing amount concentration is 1.5 mg / L (based on the inflow amount of 1 L of concentrated brine to be treated as the benchmark), slow stirring, hydraulic retention time 20 minutes; the destabilizer and scale inhibitor complex in the concentrated brine, Ca 2+ , Mg 2+ form large floc particles;

[0114] (5) The concentrated brine containing large floc particles enters the solid-liquid separator to realize solid-liquid separation; the clear water obtained after solid-liquid separation is added with acid (such as dilute hydrochloric acid) to adjust the pH value (i.e. the pH value shown in the effluent water quality table) and then enters the subsequent re-concentration process to obtain the effluent water after hardening removal; the precipitate obtained after solid-liquid separation is disposed as general solid waste.

[0115] The effluent water quality of the concentrated brine after hardening removal is shown in Table 5:

[0116] Table 5 Effluent water quality after hardening removal

[0117] Indicator Unit Value Ca 2+ ]]> mg / L 5.4 Mg 2+ ]]> mg / L 6.3 Total Fe mg / L 0.5 Total P (phosphate groups) mg / L 0.7 K + ]]> mg / L 20.1 Na + ]]> mg / L 4401.0 Si mg / L 0.42 F - ]]> mg / L 3.55 Cl - ]]> mg / L 1211 SO4 2- ]]> mg / L 9575 pH 8.0 CO3 2- ]]> mmol / L 0.57 HCO3 - ]]> mmol / L 18.5 TOC mg / L 4.42 Carboxylic groups mmol / L Not detected

[0118] As can be seen from the effluent water quality, the removal rates of Ca 2+ , Mg 2+ in the concentrated brine after hardening removal are 94.59% and 81.42% respectively, and the removal rates of TOC, total phosphorus and silicon are 98.17%, 97.22% and 96.38% respectively.

[0119] Example 5:

[0120] Based on the optimization method of double alkali hardening removal of concentrated brine, Ca 2+ , Mg 2+ is removed, for referenceFigure 1 The process flow is shown in the following steps:

[0121] (1) The concentrated brine to be treated shown in Table 1 is fed into the destabilization tank at a flow rate of 0.1 m 3 / h, and then a destabilizing agent is added into the destabilization tank; the destabilization tank is provided with one set of dosing system, including: a reagent storage tank, a dosing pipe and matching instrument valves, and one dosing port;

[0122] The destabilizing agent is the product (nano FeOOH suspension) prepared in Preparation Example 1 above, which can complex and adsorb the phosphoric acid group and carboxylic acid group containing scale inhibitors in the concentrated brine;

[0123] The molar ratio of the destabilizing agent to the total of the phosphoric acid group and carboxylic acid group in the concentrated brine is 0.8:1; the reaction time for adding the destabilizing agent is 20 minutes (i.e. the residence time of the concentrated brine in the destabilization tank);

[0124] (2) The effluent of the destabilization tank is fed into the reaction tank 1, and an aqueous sodium hydroxide solution is added into the concentrated brine in the reaction tank 1; the reaction tank 1 is provided with a dosing system, including: a reagent storage tank, a dosing pipe and matching instrument valves, and one dosing port; the reaction tank 1 is also provided with a stirring device to fully mix the reagent and the concentrated brine;

[0125] The amount of the aqueous sodium hydroxide solution added into the concentrated brine is controlled to adjust the pH of the system to 11.2; the hydraulic residence time in the reaction tank 1 is 20 minutes (i.e. the residence time of the effluent of the destabilization tank in the reaction tank 1);

[0126] (3) The effluent of the reaction tank 1 is fed into the reaction tank 2, and sodium carbonate is added into the concentrated brine in the reaction tank 2; the reaction tank 2 is provided with a dosing system, including: a reagent storage tank, a dosing pipe and matching instrument valves, and one dosing port; the reaction tank 2 is also provided with a stirring device to fully mix the reagent and the concentrated brine;

[0127] The molar ratio of the amount of sodium carbonate added to Ca 2+ is 1:1; Ca 2+ , Mg 2+ , scale inhibitors and the destabilizing agent in the concentrated brine form a co-precipitate;

[0128] Without adding the destabilizing agent in the concentrated brine, the dosage of the hardening agent (sodium carbonate) is generally 0.2-0.5 times the excess dosage (the molar ratio of the amount of sodium carbonate added to Ca 2+ is 1:1.2-1.5); compared with the dosage in the actual double-alkali method, the dosage of sodium carbonate is reduced in this embodiment due to the addition of the destabilizing agent;

[0129] (4) The effluent of the reaction tank 2 is fed into the reaction tank 3; the reaction tank 3 is divided into a coagulation zone and a flocculation zone;

[0130] Polyferric sulfate was first added to the coagulation zone of the reaction tank 3, the dosage concentration was 10 mg / L (based on the amount of 1 L of the concentrated brine to be treated), fast stirring, hydraulic retention time 5 minutes; then polyacrylamide was added to the flocculation zone of the reaction tank 3, the dosage concentration was 1.5 mg / L (based on the amount of 1 L of the concentrated brine to be treated), slow stirring, hydraulic retention time 20 minutes; the complex of the scale inhibitor and the scale inhibitor in the concentrated brine was adsorbed by the polyferric sulfate and the polyacrylamide, and the scale inhibitor was removed from the concentrated brine, and the scale inhibitor was removed from the concentrated brine. 2+ , Mg 2+ , and the scale inhibitor was removed from the concentrated brine.

[0131] (5) The concentrated brine containing large floc particles enters the solid-liquid separator to realize solid-liquid separation; the clear water obtained after solid-liquid separation enters the subsequent re-concentration process after adding acid (such as dilute hydrochloric acid) to adjust the pH value (i.e. the pH value of the effluent water quality shown in the table), to obtain effluent water after hardness removal; the precipitate obtained after solid-liquid separation is disposed as general solid waste.

[0132] The effluent water quality after hardness removal of the concentrated brine is shown in Table 6:

[0133] Table 6 Effluent water quality after hardness removal

[0134] Indicator Unit Value Ca 2+ ]]> mg / L 11.6 Mg 2+ ]]> mg / L 9.1 Total Fe mg / L 0.7 Total P (phosphate groups) mg / L 2.47 K + ]]> mg / L 23.5 Na + ]] mg / L 4473.8 Si mg / L 5.74 F - ]]> mg / L 3.22 Cl - ]]> mg / L 1485 SO4 2- ]]> mg / L 9731 pH 8.0 CO3 2- ]]> mmol / L 0.57 HCO3 - ]]> mmol / L 18.45 TOC mg / L 29.57 Carboxylic groups mmol / L Not detected

[0135] As can be seen from the effluent water quality, the removal rates of Ca 2+ , Mg 2+ in the concentrated brine after hardness removal are 88.39% and 73.16% respectively, and the removal rates of TOC, total phosphorus and silicon are 87.75%, 90.20% and 50.52% respectively.

[0136] Example 6:

[0137] The optimization method of the concentrated brine hardness removal based on the double-alkali hardness removal method, the Ca 2+ , Mg 2+ in the original concentrated brine is removed, and the process flow is shown in Table 6, and the steps are as follows: Figure 1

[0138] (1) The concentrated brine to be treated shown in Table 1 enters the destabilization tank at a flow rate of 0.1 m 3 / h, and a destabilizing agent is added to the destabilization tank; wherein the destabilization tank is provided with one set of dosing system, including: a reagent storage tank, a dosing pipe and a matching instrument valve, and one dosing port is provided;

[0139] The destabilizing agent is the product (nano FeOOH suspension) prepared in Preparation Example 1 above, which can complex and adsorb the scale inhibitor containing phosphonic acid group and carboxylic acid group in the concentrated brine;

[0140] ​The molar ratio of the breaker to the total of phosphoric acid groups and carboxylic acid groups in the concentrated brine is 2.0:1; the reaction time for adding the breaker is 20 minutes (i.e., the residence time of the concentrated brine in the breaker tank);

[0141] (2) The effluent of the breaker tank enters the reaction tank 1, and an aqueous sodium hydroxide solution is added to the concentrated brine in the reaction tank 1; wherein the reaction tank 1 is provided with a dosing system, including: a reagent storage tank, a dosing pipe and a matching instrument valve, and one dosing port is arranged; the reaction tank 1 is also provided with a stirring device to fully mix the reagent and the concentrated brine;

[0142] By controlling the amount of the aqueous sodium hydroxide solution added to the concentrated brine, the pH of the system is adjusted to 11.2; the hydraulic retention time in the reaction tank 1 is 20 minutes (i.e., the residence time of the effluent of the breaker tank in the reaction tank 1);

[0143] (3) The effluent of the reaction tank 1 enters the reaction tank 2, and sodium carbonate is added to the concentrated brine in the reaction tank 2; wherein the reaction tank 2 is provided with a dosing system, including: a reagent storage tank, a dosing pipe and a matching instrument valve, and one dosing port is arranged; the reaction tank 2 is also provided with a stirring device to fully mix the reagent and the concentrated brine;

[0144] The molar ratio of the amount of sodium carbonate to Ca 2+ is 1:1; Ca 2+ , Mg 2+ , the scale inhibitor and the breaker in the concentrated brine form a co-precipitate;

[0145] Without the breaker, the dosage of the hardening agent (sodium carbonate) in the concentrated brine is generally 0.2-0.5 times the excess dosage (the molar ratio of the dosage of sodium carbonate to Ca 2+ is 1:1.2-1.5); compared with the dosage in the actual double-alkali method, the dosage of sodium carbonate is reduced in this embodiment due to the addition of the breaker;

[0146] (4) The effluent of the reaction tank 2 enters the reaction tank 3; wherein the reaction tank 3 is divided into a coagulation zone and a flocculation zone;

[0147] First, polymeric ferric sulfate is added to the coagulation zone of the reaction tank 3, and the dosage concentration is 10 mg / L (based on the inflow of 1 L of the concentrated brine to be treated); fast stirring is performed, and the hydraulic retention time is 5 minutes; then, polyacrylamide is added to the flocculation zone of the reaction tank 3, and the dosage concentration is 1.5 mg / L (based on the inflow of 1 L of the concentrated brine to be treated); slow stirring is performed, and the hydraulic retention time is 20 minutes; the breaker and the scale inhibitor complex, Ca 2+ , Mg 2+ in the concentrated brine form large floc particles;

[0148] (5) The concentrated brine containing large flocculation particles is introduced into a solid-liquid separator to realize solid-liquid separation; the clear water obtained after the solid-liquid separation is introduced into a subsequent re-concentration process after being adjusted in pH (i.e. the pH shown in the table for the effluent water quality) by adding acid (e.g. dilute hydrochloric acid); the effluent water obtained after the hardening removal is obtained; the precipitate obtained after the solid-liquid separation is disposed as general solid waste.

[0149] The effluent water quality of the concentrated brine after the hardening removal is shown in Table 7:

[0150] Table 7 Effluent water quality after the hardening removal

[0151] Indicator Unit Value Ca 2+ ]]> mg / L 1.7 Mg 2+ ]]> mg / L 1.3 Total Fe mg / L 0.52 Total P (phosphate groups) mg / L 0.28 K + ]]> mg / L 22.1 Na + ]] mg / L 4863.0 Si mg / L 2.05 F - ]]> mg / L 1.03 Cl - ]]> mg / L 1580 SO4 2- ]]> mg / L 9956 pH 8.0 CO3 2- ]]> mmol / L 0.86 HCO3 - ]]> mmol / L 21.00 TOC mg / L 7.57 Carboxylic groups mmol / L Not detected Figure 1 Indicator Unit Value mg / L mg / L Total Fe mg / L Total P (phosphate groups) mg / L mg / L mg / L Si mg / L mg / L mg / L mg / L pH mmol / L mmol / L TOC mg / L Carboxylic groups mmol / L Not detected

[0152] As can be seen from the effluent water quality, the Ca 2+ and Mg 2+ removal rates in the concentrated brine after the hardening removal are 98.30% and 96.17% respectively, and the TOC, total phosphorus and silicon removal rates are 96.86%, 98.89% and 82.33% respectively.

[0153] Comparative Example 1:

[0154] Based on the optimization method of the hardening removal of the concentrated brine by the double-alkali hardening removal method, Ca 2+ and Mg 2+ in the original concentrated brine are removed, and the steps are as follows:

[0155] (1) The concentrated brine to be treated shown in Table 1 is directly introduced into the reaction tank 1 at a flow rate of 0.1 m 3 / h without the destabilization tank; the sodium hydroxide aqueous solution is added to the concentrated brine in the reaction tank 1; wherein, the reaction tank 1 is provided with a dosing system, including: a reagent storage tank, a dosing pipe and a matching instrument valve, and one dosing port is provided; the reaction tank 1 is also provided with a stirring device to make the reagent and the concentrated brine fully mixed;

[0156] The amount of the sodium hydroxide aqueous solution added to the concentrated brine is controlled to adjust the pH of the system to 11.2; the hydraulic retention time in the reaction tank 1 is 20 minutes (i.e. the residence time of the material in the reaction tank 1);

[0157] (2) The effluent of the reaction tank 1 is introduced into the reaction tank 2, and the sodium carbonate is added to the concentrated brine in the reaction tank 2; wherein, the reaction tank 2 is provided with a dosing system, including: a reagent storage tank, a dosing pipe and a matching instrument valve, and one dosing port is provided; the reaction tank 2 is also provided with a stirring device to make the reagent and the concentrated brine fully mixed;

[0158] The molar ratio of the addition amount of the sodium carbonate to Ca 2+ is 1:1; the Ca 2+ , Mg 2+ , scale inhibitor and destabilizing agent in the concentrated brine form a co-precipitate;

[0159] Because no destabilizing agent is added in the system, the dosage of the hardening agent-removing agent for the concentrated brine is generally set to be 0.2-0.5 times of the excess dosage (the molar ratio of the dosage of sodium carbonate to Ca 2+

[0160] (3) The effluent of the reaction tank 2 enters the reaction tank 3; wherein the reaction tank 3 is divided into a coagulation zone and a flocculation zone;

[0161] First, polymeric ferric sulfate is added to the coagulation zone of the reaction tank 3, with the dosage concentration being 10 mg / L (based on the inflow of the concentrated brine to be treated being 1 L as the benchmark), rapid stirring, and the hydraulic retention time being 5 minutes; then polyacrylamide is added to the flocculation zone of the reaction tank 3, with the dosage concentration being 1.5 mg / L (based on the inflow of the concentrated brine to be treated being 1 L as the benchmark), slow stirring, and the hydraulic retention time being 20 minutes; the scale inhibitor complex, Ca 2+ , Mg 2+ in the concentrated brine form large floc particles;

[0162] (4) The concentrated brine containing large floc particles enters the solid-liquid separator to realize solid-liquid separation; the clear water obtained after the solid-liquid separation is added with acid to adjust the pH value (i.e. the pH value shown in the effluent water quality table) and then enters the subsequent re-concentration process to obtain the effluent water after the hardness removal; the precipitate obtained after the solid-liquid separation is disposed as a general solid waste.

[0163] The effluent water quality of the concentrated brine after the hardness removal is shown in Table 8:

[0164] Table 8 Effluent water quality after the hardness removal

[0165]

[0166]

[0167] As can be seen from the effluent water quality, the removal rates of Ca 2+ , Mg 2+ in the concentrated brine after the hardness removal are 82.38% and 64.31% respectively, and the removal rates of TOC, total phosphorus and silicon are 49.58%, 19.76% and 10.43% respectively.

[0168] Comparative Example 2:

[0169] Based on the optimization method of the concentrated brine hardness removal by the double-alkali hardness removal method, Ca 2+ , Mg 2+ in the original concentrated brine are removed, and the steps are as follows:

[0170] (1) The concentrated brine to be treated shown in Table 1 is treated according to the flow rate being 0.1 m 3 ​ / h into the destabilization tank, and adding a destabilizing agent into the destabilization tank; wherein, the destabilization tank is provided with one set of dosing system, including: a reagent storage tank, a dosing pipe and matched instrument valves, and one dosing port is set;

[0171] The destabilizing agent is the product (nano FeOOH suspension) prepared in Preparation Example 1 above, which can complex and adsorb the phosphoric acid group and the carboxylic acid group of the scale inhibitor in the concentrated brine;

[0172] The molar ratio of the destabilizing agent to the total of the phosphoric acid group and the carboxylic acid group in the concentrated brine is 0.2:1; the reaction time for adding the destabilizing agent is 20 minutes (i.e. the residence time of the concentrated brine in the destabilization tank) ;

[0173] (2) The effluent of the destabilization tank enters reaction tank 1, and an aqueous sodium hydroxide solution is added to the concentrated brine in reaction tank 1; wherein, reaction tank 1 is provided with a dosing system, including: a reagent storage tank, a dosing pipe and matched instrument valves, and one dosing port is set; a stirring device is further provided in reaction tank 1 to make the reagent and the concentrated brine fully mixed;

[0174] The amount of the aqueous sodium hydroxide solution added to the concentrated brine is controlled to adjust the pH of the system to 11.2; the hydraulic residence time in reaction tank 1 is 20 minutes (i.e. the residence time of the effluent of the destabilization tank in reaction tank 1) ;

[0175] (3) The effluent of reaction tank 1 enters reaction tank 2, and sodium carbonate is added to the concentrated brine in reaction tank 2; wherein, reaction tank 2 is provided with a dosing system, including: a reagent storage tank, a dosing pipe and matched instrument valves, and one dosing port is set; a stirring device is further provided in reaction tank 2 to make the reagent and the concentrated brine fully mixed;

[0176] The molar ratio of the amount of sodium carbonate to Ca 2+ is 1:1; Ca 2+ , Mg 2+ , the scale inhibitor and the destabilizing agent in the concentrated brine form a co-precipitate;

[0177] When the amount of the destabilizing agent added in step (1) is insufficient, the dosing amount of the hardening agent in the concentrated brine is set to be 0.2-0.5 times of the excess amount (the molar ratio of the amount of sodium carbonate to Ca 2+ is 1:1.2-1.5) ;

[0178] (4) The effluent of reaction tank 2 enters reaction tank 3; wherein, reaction tank 3 is divided into a coagulation zone and a flocculation zone;

[0179] First, polymeric ferric sulfate is added to the coagulation zone of the reaction tank 3, the dosage concentration is 10 mg / L (based on the amount of 1 L of the concentrated brine to be treated), fast stirring, hydraulic retention time 5 minutes; then polyacrylamide is added to the flocculation zone of the reaction tank 3, the dosage concentration is 1.5 mg / L (based on the amount of 1 L of the concentrated brine to be treated), slow stirring, hydraulic retention time 20 minutes; the complex of the breaking agent and the scale inhibitor in the concentrated brine, Ca 2+ , Mg 2+ forms large floc particles;

[0180] (5) The concentrated brine containing large floc particles enters the solid-liquid separator to realize solid-liquid separation; the clear water obtained after the solid-liquid separation is added with acid (such as dilute hydrochloric acid) to adjust the pH value (i.e. the pH value of the effluent water quality shown in the table) and then enters the subsequent re-concentration process to obtain effluent water after hardness removal; the precipitate obtained after the solid-liquid separation is disposed as general solid waste.

[0181] The effluent water quality after the hardness removal of the concentrated brine is shown in Table 9:

[0182] Table 9 Effluent water quality after hardness removal

[0183]

[0184]

[0185] As can be seen from the effluent water quality, the removal rates of Ca 2+ , Mg 2+ in the concentrated brine after the hardness removal are 84.58% and 66.96% respectively, and the removal rates of TOC, total phosphorus and silicon are 62.38%, 40.87% and 29.66% respectively.

[0186] As can be seen from the test records of the examples and the comparative examples, the removal rates of Ca 2+ , Mg 2+ , TOC, total phosphorus and silicon in the concentrated brine after the hardness removal by the method of the present application are all very high. Comparative Example 1 is not subjected to breaking treatment before contacting with the alkaline agent, and Comparative Example 2 does not control the dosage of the breaking agent within the appropriate range, so that the hardness removal effects of both are very poor, and the removal rates of Ca 2+ , Mg 2+ , TOC, total phosphorus and silicon are all not ideal.

[0187] The above has described the examples of the present application, the above description is exemplary, not exhaustive, and is not limited to the disclosed examples. Many modifications and changes are obvious to those skilled in the art without departing from the spirit of the present application.

Claims

1. An optimized method for brine hardness removal based on double alkali hardness removal method, characterized in that, The method comprises the following steps: (1) passing the concentrated brine containing scale inhibitor into a destabilization tank, and adding a destabilization agent in the tank for destabilization treatment; the destabilization agent is selected from one or more of nano zero-valent iron, metal oxyhydroxide, potassium permanganate, persulfate and hydrogen peroxide; (2) passing the effluent of the destabilization tank into a reaction tank 1 for treatment; an alkali agent is added in the reaction tank 1; (3) the effluent of the reaction tank 1 is introduced into the reaction tank 2 for treatment; sodium carbonate is added into the reaction tank 2, so that Ca 2+ , Mg 2+ , scale inhibitor and destabilizer form a coprecipitate; (4) passing the effluent of the reaction tank 2 into a reaction tank 3 for treatment; a coagulant and a flocculant are added in the reaction tank 3 to make the precipitates in the concentrated brine form large floc particles; the concentrated brine containing the large floc particles is subjected to solid-liquid separation and concentration to obtain the effluent after hardening removal of the concentrated brine.

2. The optimization method of claim 1, wherein, The metal oxyhydroxide is selected from one or more of FeOOH, AlOOH, LaOOH, Mg(OH)2 and metal organic framework.

3. The optimization method according to claim 1 or 2, characterized in that, In step (1), the residence time of the concentrated brine to be treated in the destabilization tank is 20-60 min; and / or In step (1), the amount of the destabilization agent is 0.8-2 molar ratio of the total amount of phosphoric acid groups and carboxylic acid groups in the concentrated brine to be treated.

4. The optimization method of any one of claims 1-3, wherein, In step (2), the alkali agent is an alkaline substance, preferably selected from calcium hydroxide and / or sodium hydroxide.

5. The optimization method of any one of claims 1-4, wherein, In step (2), the pH value of the system is controlled in the range of 10.5-11.7 by the amount of the alkali agent added.

6. The optimization method of any one of claims 1-5, wherein, In step (2), the residence time of the effluent of the destabilization tank in the reaction tank 1 is 15-40 min.

7. The optimization method of any one of claims 1-6, wherein, In step (3), the amount of sodium carbonate used is in a molar ratio of 1 to 1.5 relative to the amount of Ca 2+ contained in the system.

8. The optimization method of any one of claims 1-7, wherein, In step (4), the coagulant is selected from polymeric ferric sulfate; The amount of the coagulant is 10-200 mg / L based on 1 L of the concentrated brine to be treated; after the coagulant is added, the residence time of the material in the reaction tank 3 is 5-60 min.

9. The optimization method of any one of claims 1-8, wherein, In step (4), the flocculant is selected from polyacrylamide; The amount of the flocculant is 1-10 mg / L based on 1 L of the concentrated brine to be treated; after the flocculant is added, the residence time of the material in the reaction tank 3 is 10-180 min.

10. The optimization method of any one of claims 1-9, wherein, The concentrated brine containing the large floc particles is subjected to solid-liquid separation in a solid-liquid separator, and then the filtrate obtained by the solid-liquid separation is adjusted in pH by adding acid and then enters a subsequent concentration process to obtain the effluent after hardening removal of the concentrated brine; the precipitates obtained by the solid-liquid separation are disposed as general solid waste.

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