CN113105025A - Combined treatment method for regenerating high-concentrated-salt wastewater by sodium ion exchanger - Google Patents
Combined treatment method for regenerating high-concentrated-salt wastewater by sodium ion exchanger Download PDFInfo
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Abstract
A joint treatment method for regenerating high-concentration salt wastewater by a sodium ion exchanger is characterized in that regenerated high-concentration salt wastewater generated in the regeneration process of the sodium ion exchanger is treated, and magnesium ions are separated by adopting a chemical precipitation method to form a magnesium hydroxide product; the nano-filtration method is adopted to separate calcium chloride and sodium chloride, the calcium chloride solution can be used for spraying sinter ore in the sintering section, and the calcium chloride solution does not need to be evaporated and dried to be prepared into solid in the process, so that the energy consumption is reduced. Calcium chloride is separated by adopting a sodium ion exchanger and a reverse osmosis method, and sodium chloride is purified and concentrated, so that the obtained sodium chloride solution reaches the regenerant standard of the sodium ion exchanger to recycle sodium chloride in wastewater, and reverse osmosis permeates water to generate reusable desalted water, so that regenerated high-concentration salt wastewater is reasonably and efficiently utilized, economic investment is reduced, and yield and efficiency are increased.
Description
Technical Field
The invention relates to the technical field of industrial wastewater treatment and resource recycling, in particular to a combined treatment method for regenerating high-concentrated-salt wastewater by a sodium ion exchanger in an iron and steel enterprise.
Background
Iron and steel enterprises need to use a large amount of softened water and demineralized water in production, the treatment of high-salinity wastewater generated in the water production process is always difficult, particularly, the high-salinity wastewater regenerated by a sodium ion exchanger is directly discharged after harmless treatment or discharged to a sewage treatment plant for recycling after being treated by the sewage treatment plant, and the high-salinity wastewater greatly increases the burden of subsequent sewage treatment.
In industrial enterprises, ion exchange resin regeneration wastewater treatment methods mainly comprise a neutralization method, a precipitation method, a Fenton method, a biological method, a nanofiltration method and the like, most of the methods are harmless treatment and then are discharged, and two byproducts of calcium salt and magnesium salt are recovered or sodium chloride is recovered for recycling during a small part of treatment. The existing treatment method for regenerating concentrated salt wastewater by using sodium ion exchanger resin comprises the following steps:
qianfeng, Zhangjing, Liwei and the like, in the article published in the journal of environmental science and technology in 2009 01 Yue, the research on the use of the regeneration wastewater of the boiler soft water station in flue gas desulfurization, the regeneration wastewater of the boiler soft water is used as a desulfurizing agent and an additive of the desulfurizing agent. In a simulation experiment of recycling and utilizing ion exchange resin regeneration wastewater published in a text of 'Hebei metallurgy' published in 12.2012 journal of the morning glory and the Liyuyin, respectively adding a magnesium precipitator and a calcium precipitator into ion exchange resin regeneration high-salt wastewater, removing calcium and magnesium ions in the wastewater after fractional precipitation treatment, and recycling filtered clear liquid as a regenerant to obtain two byproducts of calcium salt and magnesium salt. Wuchunmi and Chen is enriched in the article 'simulation test research on recycling treatment of ion exchange resin regeneration wastewater' published in 2008 < 01 > journal of environmental engineering journal, the high-concentration wastewater part with the most concentrated hardness ions and chloride ions in the regeneration wastewater is subjected to fractional precipitation treatment, the chloride ions in the high-concentration wastewater are recycled, the hardness ions are effectively removed, and 2 precipitation byproducts are obtained. In the research on the treatment of ion exchange resin regeneration wastewater by a precipitation method, which is published in a paper of 'the research on ion exchange resin regeneration wastewater by precipitation method' of the book of Harbin university of commerce, journal of 03 months in 2010, Rough waves, wastewater in a high salt-containing area is subjected to precipitation and desalination, and supernatant after precipitation is separated is mainly sodium chloride and is recycled as sodium ion exchange resin regeneration liquid.
The methods for regenerating high-concentration salt wastewater by using ion exchange resins proposed in the above documents mostly adopt a chemical method to precipitate calcium ions and magnesium ions, and chemical reagents adopted by the chemical method, such as a precipitator, have the advantages of large dosage, high price and high energy consumption, so that the cost of wastewater treatment is seriously influenced, and the large-area popularization and use are not facilitated.
Disclosure of Invention
The invention provides a combined treatment method for regenerating high-concentration salt wastewater by a sodium ion exchanger, which is configured with a whole set of treatment process and treatment process aiming at the characteristic of pollutant content of the high-concentration salt wastewater regenerated by the sodium ion exchanger in the steel industry. The sodium ion exchange resin is mainly used for regenerating the high-concentration salt wastewater, calcium ions, magnesium ions, chloride ions and sodium ions are contained in the high-concentration salt wastewater, and the calcium chloride solution and the sodium chloride solution which account for the main concentrations are separated and recycled, so that the high-concentration salt wastewater regenerated by the sodium ion exchanger is not wastewater any more, but a resource capable of obtaining chemicals and recycling the chemicals, and meanwhile, the adding amount of a chemical precipitation reagent can be reduced, the energy consumption of evaporative crystallization is reduced, and the yield and the efficiency are increased.
The technical scheme of the invention is as follows:
a combined treatment method for regenerating high concentrated salt wastewater by a sodium ion exchanger is characterized by comprising the following steps,
s1, introducing the high concentrated salt wastewater regenerated by the sodium ion exchanger to a regenerated high concentrated salt wastewater pool, adding alkali (such as one or more of sodium hydroxide, calcium hydroxide and calcium oxide) into the regenerated high concentrated salt wastewater pool to make the liquid in the waste pool alkaline and the pH value between 8 and 10, and introducing air into the regenerated high concentrated salt wastewater pool to perform aeration treatment to coagulate trace iron ions in the liquid in the waste pool to generate ferric hydroxide; filtering the filtrate by a filter to remove ferric hydroxide, broken resin and impurities, and then sending the filtered water into a clear liquid pool;
s2, detecting Ca of the filtered water in the clear liquid pool2+Concentration and Mg2+Concentration; if the calcium chloride solution required by the spraying of the sintering ore is not allowed to have magnesium chloride with a certain concentration, the filtered water in the clear liquid pool is transferred to a reaction pool, and according to Mg2+The content of sodium hydroxide, calcium hydroxide and calcium oxide added into the mixtureAdjusting the pH value to 10.5-12.0, sending the reacted solution into a sedimentation tank, filtering the supernatant in the sedimentation tank through a filter after the precipitation is finished, sending the filtered supernatant into a liquid storage tank, taking out the precipitate in the sedimentation tank, washing, dehydrating, drying and crushing to obtain high-purity magnesium hydroxide powder; if the calcium chloride solution required by the spraying of the sinter allows the existence of magnesium chloride with corresponding concentration, directly transferring the filtered water in the clear liquid pool into a liquid storage pool;
s3, adding hydrochloric acid to adjust the pH value of the solution in the liquid storage tank to be between 5 and 7, and adding a proper amount of demineralized water to enable the volume of the solution in the liquid storage tank to be 1 to 8 times of the volume of the regenerated high-concentration salt wastewater, so as to obtain diluted liquid;
s4, performing nanofiltration on the diluted liquid through a nanofiltration device, wherein the nanofiltration device selects a nanofiltration membrane with high calcium chloride rejection rate and low sodium chloride rejection rate; the main component of the nanofiltration concentrated water obtained after the nanofiltration device is calcium chloride solution, and the main component of the nanofiltration permeated water obtained is sodium chloride solution;
s5, detecting the concentrations of a calcium chloride solution and a sodium chloride solution in the nanofiltration concentrated water;
s6, if the concentration of the calcium chloride solution in the nanofiltration concentrated water is lower than the concentration requirement of the calcium chloride solution required by the sinter spraying, sending the nanofiltration concentrated water to the next liquid storage tank, and entering the step S7; if the calcium chloride solution in the nanofiltration concentrated water meets the concentration and purity requirements of the calcium chloride solution required by sinter spraying, the step S8 is executed;
s7, repeating the steps S3-S6 until the calcium chloride solution in the nanofiltration concentrated water meets the requirements of the concentration and the purity of the calcium chloride solution required by the sinter spraying;
s8, conveying nanofiltration concentrated water meeting the requirements of the concentration and the purity of the calcium chloride solution required by the sinter spraying to a sintering section, and adjusting indexes for spraying the sinter;
in the steps S4 and S7, nanofiltration permeated water obtained by each nanofiltration is sent to a sodium ion exchanger, and residual calcium ions in the nanofiltration permeated water are selectively removed through sodium ion exchange resin to form calcium-removed low-salt water mainly containing sodium chloride; performing reverse osmosis treatment on the calcium-removed low-salt water, wherein reverse osmosis concentrated water obtained by the reverse osmosis treatment is 5-10% of sodium chloride solution; if the concentration of the sodium chloride solution in the reverse osmosis concentrated water is lower than 5-10%, adding sodium chloride, adjusting the concentration to 5-10%, and directly using the 5-10% sodium chloride solution as a regenerant of the sodium ion exchanger; the permeate obtained by the reverse osmosis treatment is desalted water, and is fed back to the dilution liquid used in steps S3 and S7.
Preferably, the recovery rate of nanofiltration permeated water of the nanofiltration device is more than 85 percent, and the pressure is more than 0.70 MPa; a security filter is arranged in front of the nanofiltration device.
Preferably, the nanofiltration membrane of the nanofiltration device has a calcium chloride rejection rate of more than 90% and a sodium chloride rejection rate of less than 40%.
Preferably, the filter includes a multimedia filter and an ultrafilter.
Preferably, in S2, the PH is adjusted to 11.0 to 11.5.
Preferably, in S2, a flocculating agent is added to the sedimentation tank to accelerate the sedimentation velocity of the solution.
Preferably, the concentration of the calcium chloride solution required for spraying the sinter is required to be more than 3%.
Preferably, the combined treatment method for regenerating the high concentrated salt wastewater by the sodium ion exchanger further comprises the step S9 of repeating the steps S3-S6, concentrating the concentrated solution through multiple times of nanofiltration operation until the concentration of the calcium chloride solution is more than 12%, adding one or more of sodium hydroxide, calcium hydroxide and calcium oxide, and adjusting the pH value to 7.5-11 to obtain an industrial calcium chloride product specified in GB/T26520-2011, wherein the concentration difference between the calcium chloride and the sodium chloride in the nanofiltration concentrated water reaches more than 20 times, so that the calcium chloride solution with the purity level of the industrial calcium chloride standard product specified in GB/T26520-2011 is obtained.
Preferably, the combined treatment method for regenerating the high concentrated salt wastewater by the sodium ion exchanger further comprises a step S10 of evaporating, drying and pulverizing the calcium chloride solution obtained in the step S9 to obtain calcium chloride solid powder.
Preferably, in S1, before the filtered water is sent to the clear water tank, the filtered water is sent to a decarbonizer to remove carbon dioxide from the filtered water, so as to further improve the purity of the extracted magnesium hydroxide.
The invention has the following technical effects: the combined treatment method for the high-concentration brine waste water regenerated by the sodium ion exchanger treats the regenerated high-concentration brine waste water generated in the regeneration process of the sodium ion exchanger, the sodium ion exchanger is regenerated after resin adsorption saturation, and calcium chloride and sodium chloride are separated by adopting a nanofiltration method after the high-concentration brine waste water in the regeneration process of the sodium ion exchanger is separately collected through the control of a concentrated brine discharge valve and a discharge pipeline, the calcium chloride solution can be used for spraying sinter ore in a sintering section, the calcium chloride solution is not required to be evaporated and dried to prepare solid in the process, and the energy consumption is reduced. Calcium chloride is separated by adopting a sodium ion exchanger and a reverse osmosis method, and sodium chloride is purified and concentrated, so that the obtained sodium chloride solution reaches the standard of a sodium ion exchanger regenerant, the sodium chloride in the wastewater is recycled, and meanwhile, the economic investment is reduced. The reverse osmosis permeate water is desalted water which can be reused and is used as dilution water or reagent preparation water in the treatment process. If the calcium chloride solution used for spraying the sinter in the sintering section has higher requirement on the concentration of magnesium ions in the sinter, a chemical precipitation method can be adopted to separate the magnesium ions in advance, and a high-purity magnesium hydroxide product is produced in the process to serve as an industrial raw material. In the process of producing magnesium hydroxide, calcium hydroxide is used as a reaction reagent, and the concentration of calcium chloride solution is increased to improve the product value. Therefore, the regenerated high-concentration salt wastewater is not wastewater any more, but is regarded as a resource capable of obtaining chemicals; the combined treatment method for the high-concentration brine regenerated by the sodium ion exchanger gradually separates and purifies calcium salt, magnesium salt and sodium salt in the high-concentration brine regenerated wastewater, not only finishes wastewater treatment and resource recovery, but also reduces the dosage of chemical precipitation reagent, reduces the energy consumption of evaporation crystallization, increases the use value of the product, and further realizes yield and efficiency increase.
Drawings
FIG. 1 is a schematic view of the treatment process in the combined treatment method of the wastewater with high concentrated salt regenerated by the sodium ion exchanger of the invention.
Detailed Description
The invention will now be described in detail with reference to fig. 1 and a specific embodiment.
Example 1
A certain iron and steel enterprise adopts a sodium ion exchanger to prepare softened water, after the resin of the sodium ion exchanger is saturated, 6% sodium chloride solution is adopted to regenerate the resin, wastewater with low salt content is discharged to a factory sewage treatment plant by controlling a wastewater discharge valve and a discharge pipeline, the wastewater becomes qualified reclaimed water after being treated, and the reclaimed water is used for preparing softened water through the sodium ion exchanger; and (4) collecting regenerated high-concentration salt wastewater generated in the resin regeneration process under the control of a strong-salt wastewater discharge valve and a strong-salt wastewater discharge pipeline.
The combined treatment method for regenerating high concentrated salt wastewater by the sodium ion exchanger comprises the following treatment processes:
s1, introducing the high-concentration salt wastewater regenerated by the sodium ion exchanger to a regenerated high-concentration salt wastewater pool, adding one or more of sodium hydroxide, calcium hydroxide and calcium oxide into the regenerated high-concentration salt wastewater pool, adjusting the pH value to 9, and introducing air into the regenerated high-concentration salt wastewater pool for aeration treatment to coagulate trace iron ions in liquid in the regenerated high-concentration salt wastewater pool to generate iron hydroxide precipitate; filtering ferric hydroxide, broken resin and other impurities in the wastewater by using a multi-media filter, and then sending the filtered water into a clear liquid pool;
s2, detecting Ca of the filtered water in the clear liquid pool2+The concentration is 3356Mg/L, Mg2+The concentration is 636 mg/L; because the calcium chloride solution required by spraying the sintering ore is not allowed to have magnesium chloride with a certain concentration, the filtered water in the clear liquid pool is transferred to the reaction pool, and according to Mg2+Adding one or more of sodium hydroxide, calcium hydroxide and calcium oxide into the solution, adjusting the pH value to 11.2, sending the solution after reaction into a sedimentation tank, filtering the supernatant in the sedimentation tank through a multi-medium filter after the sedimentation is finished, sending the supernatant into a first liquid storage tank, taking out the precipitate in the sedimentation tank, washing, dehydrating, drying and crushing to obtain high-purity magnesium hydroxide powder;
s3, adding hydrochloric acid to adjust the pH value of the solution in the first liquid storage tank to be between 5 and 7, adding a proper amount of demineralized water, and adjusting the water amount to dilute the solution to 4 times of the volume of the high-concentration saline wastewater to obtain a first diluted liquid;
s4, performing primary nanofiltration on the first diluted liquid through a nanofiltration device, wherein the nanofiltration device selects a nanofiltration membrane with high calcium chloride rejection rate and low sodium chloride rejection rate, the recovery rate of nanofiltration permeated water is 90%, and the pressure is more than 0.70 MPa; the main component of the primary nanofiltration concentrated water obtained after the nanofiltration device is calcium chloride solution, and the main component of the obtained nanofiltration permeated water is sodium chloride solution;
s5, detecting that the concentration of calcium chloride reaches 2.7 percent after one-time nanofiltration;
s6, the concentration of calcium chloride solution needed by the sinter spraying is required to be about 3 percent, so the process goes to step S7;
s7, repeating the steps S3-S6, and carrying out secondary nanofiltration, wherein the specific operations are as follows: feeding the primary nanofiltration concentrated water into a second liquid storage tank, adding hydrochloric acid to adjust the pH of the solution in the second liquid storage tank to be between 5 and 7, adding a proper amount of desalted water, and adjusting the water amount to dilute the volume of the solution to be 4 times of that of the primary nanofiltration concentrated water to obtain a second diluted liquid; carrying out secondary nanofiltration on the second diluted liquid through a second nanofiltration device, wherein the second nanofiltration device selects a nanofiltration membrane with high calcium chloride rejection rate and low sodium chloride rejection rate, the recovery rate of nanofiltration permeating water is 90%, and the pressure is more than 0.70 MPa; the main component of the secondary nanofiltration concentrated water obtained after passing through the second nanofiltration device is a calcium chloride solution, and the main component of the obtained nanofiltration permeated water is a sodium chloride solution; detecting that the concentration of calcium chloride reaches 6.1 percent after the secondary nanofiltration;
and S8, conveying the secondary nanofiltration concentrated water to a sintering section, and directly spraying sintered ore after adjusting indexes (adding demineralized water to dilute to 3% of calcium chloride solution concentration and adjusting pH value).
Preferably, the combined treatment method for regenerating the high concentrated salt wastewater by the sodium ion exchanger can also simultaneously enter the step S9 after the step S7 when the calcium chloride solution for spraying the sintering ore is sufficient, repeat the steps S3 to S6, and carry out multiple nanofiltration operations, namely:
s9.1, sending the secondary nanofiltration concentrated water into a third liquid storage tank, adding hydrochloric acid to adjust the pH of the solution in the third liquid storage tank to be between 5 and 7, adding a proper amount of desalted water, and adjusting the water amount to dilute the volume of the solution to be 4 times of that of the secondary nanofiltration concentrated water to obtain third diluted liquid;
s9.2, performing nanofiltration on the third diluted liquid for three times through a nanofiltration device;
s9.3, detecting that the concentration of calcium chloride reaches 13.2 percent after three times of nanofiltration; and meanwhile, the concentration of sodium chloride is detected to be less than 0.63%, one or more of sodium hydroxide, calcium hydroxide and calcium oxide are added, the pH is adjusted to 7.5-11, the product standard of industrial calcium chloride specified in GB/T26520-2011 is reached, and the purity of the solution reaches the purity level of industrial calcium chloride products specified in GB/T26520-2011.
Wherein, nanofiltration permeated water obtained by each nanofiltration is sent into a sodium ion exchanger, and the residual calcium ions in the nanofiltration permeated water are selectively removed through sodium ion exchange resin to form calcium-removed low-salt water mainly containing sodium chloride; and (3) performing reverse osmosis treatment on the calcium-removed low-salt water to obtain reverse osmosis concentrated water which is a sodium chloride solution, and separating and concentrating the sodium chloride solution until the concentration is 6% to be used as a sodium ion exchange resin regenerant. The reverse osmosis permeated water obtained by the reverse osmosis treatment is desalted water and can be directly used as dilution water or reagent preparation water of other steps.
Example 2
A certain iron and steel enterprise adopts a sodium ion exchanger to prepare softened water, after the resin of the sodium ion exchanger is saturated, 8% sodium chloride solution is adopted to regenerate the resin, wastewater with low salt content is discharged to a factory sewage treatment plant by controlling a wastewater discharge valve and a discharge pipeline, the wastewater becomes qualified reclaimed water after being treated, and the reclaimed water is used for preparing softened water through the sodium ion exchanger; and (4) collecting regenerated high-concentration salt wastewater generated in the resin regeneration process under the control of a strong-salt wastewater discharge valve and a strong-salt wastewater discharge pipeline.
The combined treatment method for regenerating high concentrated salt wastewater by the sodium ion exchanger comprises the following treatment processes:
s1, introducing the high concentrated salt wastewater regenerated by the sodium ion exchanger to a regenerated high concentrated salt wastewater tank, adding one or more of sodium hydroxide, calcium hydroxide and calcium oxide into the regenerated high concentrated salt wastewater tank, adjusting the pH value to 9.5, and introducing air into the regenerated high concentrated salt wastewater tank for aeration treatment to coagulate trace iron ions in liquid in the regenerated high concentrated salt wastewater tank to generate ferric hydroxide precipitate; after the ferric hydroxide, the broken resin and other impurities in the water are filtered by a multi-medium filter, the filtered water is sent to a decarbonizer to remove carbon dioxide in the water, and then the filtered water from which the carbon dioxide is removed is sent to a clear liquid pool;
s2, detecting Ca of the filtered water in the clear liquid pool2+The concentration is 3923Mg/L, Mg2+The concentration is 871 mg/L; because the calcium chloride solution required by spraying the sintering ore is not allowed to have magnesium chloride with a certain concentration, the filtered water in the clear liquid pool is transferred to the reaction pool, and according to Mg2+Adding sodium hydroxide and calcium hydroxide solution into the solution, adjusting the pH value to 11.0, sending the solution after reaction into a sedimentation tank, filtering supernatant in the sedimentation tank through an ultrafilter after the sedimentation is finished, sending the supernatant into a first liquid storage tank, taking out precipitates in the sedimentation tank, washing, dehydrating, drying and crushing to obtain high-purity magnesium hydroxide powder;
s3, adding hydrochloric acid to adjust the pH value of the solution in the first liquid storage tank to be between 5 and 7, adding a proper amount of demineralized water, and adjusting the water amount to dilute the solution to 4 times of the volume of the high-concentration saline wastewater to obtain a first diluted liquid;
s4, performing primary nanofiltration on the first diluted liquid through a nanofiltration device, wherein the nanofiltration device selects a nanofiltration membrane with high calcium chloride rejection rate and low sodium chloride rejection rate, the recovery rate of nanofiltration permeated water is 90%, and the pressure is more than 0.70 MPa; the main component of the primary nanofiltration concentrated water obtained after the nanofiltration device is calcium chloride solution, and the main component of the obtained nanofiltration permeated water is sodium chloride solution;
s5, detecting that the concentration of calcium chloride reaches 3.4% after one-time nanofiltration;
s6, the concentration of the calcium chloride solution required by the sinter spraying is required to be about 3%, and the concentration of the calcium chloride after one-time nanofiltration reaches 3.4%, but the solution also contains sodium chloride with certain concentration, so the process goes to step S7;
step S7, repeating the steps S3-S6, and carrying out nanofiltration for multiple times; the specific operation is that secondary nanofiltration: feeding the primary nanofiltration concentrated water into a second liquid storage tank, adding hydrochloric acid to adjust the pH of the solution in the second liquid storage tank to be between 5 and 7, adding a proper amount of desalted water, and adjusting the water amount to dilute the volume of the solution to be 8 times of the volume of the primary nanofiltration concentrated water to obtain a second diluted liquid; nanofiltration is carried out on the second diluted liquid through a second nanofiltration device, wherein the second nanofiltration device selects a nanofiltration membrane with high calcium chloride rejection rate and low sodium chloride rejection rate, the recovery rate of nanofiltration permeating water is 90%, and the pressure is more than 0.70 MPa; the main component of the secondary nanofiltration concentrated water obtained after passing through the second nanofiltration device is a calcium chloride solution, and the main component of the obtained nanofiltration permeated water is a sodium chloride solution; detecting that the concentration of calcium chloride reaches 3.9 percent after the secondary nanofiltration; and (3) carrying out nanofiltration for three times: sending the secondary nanofiltration concentrated water into a third liquid storage tank, adding hydrochloric acid to adjust the pH of the solution in the third liquid storage tank to be between 5 and 7, adding a proper amount of desalted water, and adjusting the water quantity to dilute the volume of the solution to 8 times of the volume of the secondary nanofiltration concentrated water to obtain a third diluted liquid; nanofiltration is carried out on the third diluted liquid through a third nanofiltration device, wherein the third nanofiltration device selects a nanofiltration membrane with high calcium chloride rejection rate and low sodium chloride rejection rate, the recovery rate of nanofiltration permeating water is 90%, and the pressure is more than 0.70 MPa; detecting that the concentration of calcium chloride reaches 4.5% after three times of nanofiltration and the concentration of sodium chloride is less than 0.21%, and entering step S8;
and step S8, conveying the triple nanofiltration concentrated water to a sintering section, and spraying sintered ore after adjusting indexes (adding a proper amount of demineralized water to enable the concentration of the calcium chloride solution to be 3% and adjusting the pH value).
Preferably, the combined treatment method for regenerating the high concentrated salt wastewater by the sodium ion exchanger can also enter step S9 after step S6 or step S7, step S3-S6 are repeated, one or more of sodium hydroxide, calcium hydroxide and calcium oxide are added into nanofiltration concentrated water after multiple nanofiltration operations, the pH is adjusted to 7.5-11 to obtain an industrial product, and the concentration difference between the calcium chloride and the sodium chloride reaches more than 20 times, so that the calcium chloride solution with the purity level of industrial calcium chloride standard products specified in GB/T26520-2011 is obtained.
Wherein, nanofiltration permeated water obtained by each nanofiltration is sent into a sodium ion exchanger, and the residual calcium ions in the nanofiltration permeated water are selectively removed through sodium ion exchange resin to form calcium-removed low-salt water mainly containing sodium chloride; and (3) performing reverse osmosis treatment on the calcium-removed low-salt water to obtain reverse osmosis concentrated water which is a sodium chloride solution, and separating and concentrating the sodium chloride solution until the concentration is 8% to be used as a sodium ion exchange resin regenerant. The reverse osmosis permeated water obtained by the reverse osmosis treatment is desalted water and can be directly used as dilution water or reagent preparation water of other steps.
It is pointed out here that the above description is helpful for the person skilled in the art to understand the invention, but does not limit the scope of protection of the invention. Any such equivalents, modifications and/or omissions as may be made without departing from the spirit and scope of the invention may be resorted to.
Claims (10)
1. A combined treatment method for regenerating high concentrated salt wastewater by a sodium ion exchanger is characterized by comprising the following steps,
s1, introducing the high concentrated salt wastewater regenerated by the sodium ion exchanger to a regenerated high concentrated salt wastewater pool, adding one or more of sodium hydroxide, calcium hydroxide and calcium oxide into the regenerated high concentrated salt wastewater pool to make the liquid in the waste pool alkaline and the pH value between 8 and 10, and introducing air into the regenerated high concentrated salt wastewater pool to perform aeration treatment to coagulate trace iron ions in the liquid in the waste pool to generate ferric hydroxide; filtering the filtrate by a filter to remove ferric hydroxide, broken resin and impurities, and then sending the filtered water into a clear liquid pool;
s2, detecting Ca of the filtered water in the clear liquid pool2+Concentration and Mg2+Concentration; if the calcium chloride solution required by the spraying of the sintering ore is not allowed to have magnesium chloride with a certain concentration, the filtered water in the clear liquid pool is transferred to a reaction pool, and according to Mg2+Adding one or more of sodium hydroxide, calcium hydroxide and calcium oxide to adjust pH to 10.5-12.0, feeding the solution into a precipitation tank, filtering the supernatant in the precipitation tank with a filter, feeding into a liquid storage tank, precipitatingTaking out the precipitate in the pool, washing, dehydrating, drying and crushing to obtain high-purity magnesium hydroxide powder; if the calcium chloride solution required by the spraying of the sinter allows the existence of magnesium chloride with corresponding concentration, directly transferring the filtered water in the clear liquid pool into a liquid storage pool;
s3, adding hydrochloric acid to adjust the pH value of the solution in the liquid storage tank to be between 5 and 7, and adding a proper amount of demineralized water to enable the volume of the solution in the liquid storage tank to be 1 to 8 times of the volume of the regenerated high-concentration salt wastewater, so as to obtain diluted liquid;
s4, performing nanofiltration on the diluted liquid through a nanofiltration device, wherein the nanofiltration device selects a nanofiltration membrane with high calcium chloride rejection rate and low sodium chloride rejection rate; the main component of the nanofiltration concentrated water obtained after the nanofiltration device is calcium chloride solution, and the main component of the nanofiltration permeated water obtained is sodium chloride solution;
s5, detecting the concentrations of a calcium chloride solution and a sodium chloride solution in the nanofiltration concentrated water;
s6, if the concentration and purity of the calcium chloride solution in the nanofiltration concentrated water are lower than the concentration and purity requirements of the calcium chloride solution required by sinter spraying, sending the nanofiltration concentrated water to a next liquid storage tank, and entering the step S7; if the calcium chloride solution in the nanofiltration concentrated water meets or is more than the concentration and purity requirements of the calcium chloride solution required by the sinter spraying, the step S8 is carried out;
s7, repeating the steps S3-S6, and performing nanofiltration operation on the nanofiltration concentrated water for a plurality of times until the calcium chloride solution in the nanofiltration concentrated water finally obtained meets the requirements of the concentration and the purity of the calcium chloride solution required by sinter spraying;
s8, conveying nanofiltration concentrated water meeting the requirements of the concentration and the purity of the calcium chloride solution required by the sinter spraying to a sintering section, and adjusting indexes for spraying the sinter;
in the steps S4 and S7, nanofiltration permeated water obtained by each nanofiltration is sent to a sodium ion exchanger, and residual calcium ions in the nanofiltration permeated water are selectively removed through sodium ion exchange resin to form calcium-removed low-salt water mainly containing sodium chloride; performing reverse osmosis treatment on the calcium-removed low-salt water, wherein reverse osmosis concentrated water obtained by the reverse osmosis treatment is 5-10% of sodium chloride solution; if the concentration of the sodium chloride solution in the reverse osmosis concentrated water is lower than 5-10%, adding sodium chloride, adjusting the concentration to 5-10%, and directly using the 5-10% sodium chloride solution as a regenerant of the sodium ion exchanger; the permeate obtained by the reverse osmosis treatment is desalted water, and is fed back to the dilution liquid used in steps S3 and S7.
2. The combined treatment method for regenerating high concentrated salt wastewater by the sodium ion exchanger as claimed in claim 1, wherein the nanofiltration permeated water recovery rate of the nanofiltration device is more than 85%, and the pressure is more than 0.70 MPa; a security filter is arranged in front of the nanofiltration device.
3. The combined treatment method for regenerating high concentrated salt wastewater by the sodium ion exchanger as claimed in claim 1 or 2, wherein the nanofiltration membrane of the nanofiltration device has a calcium chloride rejection rate of more than 90% and a sodium chloride rejection rate of less than 40%.
4. The integrated treatment method for regenerating high concentrated salt wastewater by a sodium ion exchanger as claimed in claim 1 or 2, wherein the filter comprises a multi-media filter and an ultrafilter.
5. The integrated treatment method for regenerating concentrated salt wastewater by sodium ion exchanger as claimed in claim 1 or 2, wherein in S2, the pH value is adjusted to 11.0-11.5.
6. The integrated treatment method for regenerating concentrated salt wastewater by using sodium ion exchanger as claimed in claim 1 or 2, characterized in that in S2, a flocculating agent is added into the precipitation tank to accelerate the precipitation speed of the solution.
7. The combined treatment method for regenerating the high concentrated salt wastewater by the sodium ion exchanger as claimed in claim 1 or 2, wherein the concentration of the calcium chloride solution required by the sinter ore spraying is required to be more than 3%.
8. The combined treatment method for the high concentrated salt wastewater regenerated by the sodium ion exchanger according to claim 1 or 2, characterized by further comprising the step of S9, repeating the steps S3-S6, carrying out nanofiltration operation on the nanofiltration concentrated water for a plurality of times, concentrating the nanofiltration concentrated water until the concentration of the calcium chloride solution is more than 12%, adding one or more of sodium hydroxide, calcium hydroxide and calcium oxide, adjusting the pH value to 7.5-11 to obtain an industrial calcium chloride product specified in GB/T26520-2011, wherein the concentration difference between the calcium chloride and the sodium chloride in the nanofiltration concentrated water reaches more than 20 times, and the obtained calcium chloride solution is the calcium chloride solution with the product purity level in the industrial calcium chloride standard.
9. The combined treatment method for regenerating concentrated salt wastewater by the Na ion exchanger as claimed in claim 1 or 2, further comprising step S10, wherein the calcium chloride solution obtained in step S9 is evaporated, dried and powdered to obtain calcium chloride solid powder.
10. The integrated process of claim 1, wherein in step S1, before the filtered water is sent to the clear water tank, the filtered water is sent to a decarbonizer to remove carbon dioxide from the filtered water, so as to further increase the purity of the extracted magnesium hydroxide.
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