Method for treating coking wastewater hardness removal resin regeneration waste liquid by using old membrane

Abstract

The invention provides a method for treating coking wastewater hardness removal resin regeneration waste liquid by using an old membrane, and belongs to the technical field of coking wastewater zero discharge treatment, and the method comprises the following steps: step 1), carrying out high-flow washing on an old reverse osmosis membrane, and then introducing a test solution to test the salinity of the old reverse osmosis membrane, marking the old reverse osmosis membrane with low salinity as a low-salinity membrane according to the salinity, introducing a sodium hypochlorite solution into the old reverse osmosis membrane with high salinity to carry out circular oxidation until the desalination rate reaches a preset value, and marking the old reverse osmosis membrane after oxidation treatment as a high-salinity membrane for later use; (2) adding sodium hydroxide and sodium carbonate into the hardness-removed resin regeneration waste liquid, stirring, dehydrating chemical sludge generated by reaction, introducing supernate after reaction into the high-salt-permeability membrane obtained in the step (1), refluxing concentrated water of the high-salt-permeability membrane, and continuously adding sodium hydroxide and sodium carbonate; and (3) introducing the high-salt-permeability membrane produced water obtained in the step (2) into the low-salt-permeability membrane obtained in the step (1), conveying the low-salt-permeability concentrated water out of the system, carrying out ultrahigh-pressure concentration or extracting sodium chloride by an evaporative crystallization system, applying the low-salt-permeability membrane produced water to high-flow flushing and test liquid preparation in the step (1), and delivering redundant low-salt-permeability membrane produced water as product water. According to the invention, the impact problem after the hardness removal resin regeneration waste liquid flows back to the water treatment system can be eliminated, and meanwhile, a new resource utilization mode of the old reverse osmosis membrane is expanded.

Description

Technical Field

[0001] The invention relates to a method for treating hard resin regeneration waste liquid, in particular to a method for treating hard resin regeneration waste liquid from coking waste water by using old membranes, belonging to the technical field of zero-discharge treatment of coking waste water. Background Art

[0002] In the zero-discharge treatment system for coking wastewater, hardness removal resin plays a key role. Its core function is to use the ion exchange effect of the resin on the basis of front-end chemical hardness removal to fix the residual hardness in the wastewater on its own hardness removal group, thereby achieving near-zero control of the hardness and avoiding the scaling of calcium fluoride, calcium sulfate, calcium carbonate, etc. that occurs when the subsequent reverse osmosis membrane systems at all levels concentrate the wastewater. There is little in-depth research on the treatment of the regenerated waste liquid of coking wastewater hardness removal resin. The regenerated waste liquid contains a large amount of calcium and magnesium hardness, and its pH value varies between 1-12. After returning to the coking wastewater treatment system, it will have a greater impact on the original system in terms of hardness, pH value, and water volume.

[0003] In many water treatment industries, including coking wastewater treatment, reverse osmosis membranes are widely used. Their ability to remove salt allows the high-salt side of the reverse osmosis membrane to be continuously concentrated to meet the requirements of evaporation and crystallization water inlet, while the low-salt side water is reused as product water in production. As the reverse osmosis membrane is continuously used, it faces organic matter, colloid pollution, scaling and chemical cleaning. The desalination rate of the reverse osmosis membrane will continue to decrease and eventually reach the elimination standard. Compared with the old reverse osmosis membranes eliminated by the power and municipal industries, the old reverse osmosis membranes eliminated by coking wastewater are often considered to have lower utilization value due to their more complex and poor water quality. According to statistics, the annual elimination scale of waste reverse osmosis membranes in various industrial enterprises in my country, including the coking wastewater field, has exceeded 20,000t / year. A large number of old reverse osmosis membranes with reuse value are scrapped and disposed of in a rough manner due to the lack of corresponding reuse methods, resulting in a waste of resources. Summary of the invention

[0004] In response to the above problems, the present invention provides a method for treating coking wastewater to remove hard resin regeneration waste liquid using old reverse osmosis membranes, which not only eliminates the impact problem after the resin regeneration waste liquid returns to the water treatment system, but also develops a new way of resource utilization of old reverse osmosis membranes.

[0005] To achieve the above object, the technical solution of the present invention is: a method for treating coking wastewater by using old membrane to remove hard resin regeneration waste liquid, comprising the following steps:

[0006] Step 1): flush the old reverse osmosis membrane with a high flow rate, then pass a test solution to test the salt permeability of the old reverse osmosis membrane, and record the old reverse osmosis membrane with low salt permeability as a low salt permeability membrane according to the level of the salt permeability, pass a sodium hypochlorite solution into the old reverse osmosis membrane with high salt permeability for cyclic oxidation until the desalination rate reaches a predetermined value, and record the old reverse osmosis membrane after oxidation treatment as a high salt permeability membrane for standby use;

[0007] Step 2): adding sodium hydroxide and sodium carbonate to the hard resin regeneration waste liquid, stirring, dehydrating the chemical sludge produced by the reaction, passing the supernatant after the reaction into the high-permeability salt membrane obtained in step 1), and refluxing the high-permeability salt membrane concentrated water to continue adding sodium hydroxide and sodium carbonate;

[0008] Step 3): The high-permeability salt membrane water of step 2) is passed into the low-permeability salt membrane obtained in step 1), and the low-permeability salt concentrated water is sent outside the system for ultra-high pressure concentration or evaporation crystallization system to extract sodium chloride. The low-permeability salt membrane water is used for high-flow flushing and test liquid preparation in step 1), and the excess low-permeability salt membrane water is sent out as product water.

[0009] Furthermore, the test solution in step 1) is prepared by dissolving 3000 g of analytically pure solid sodium chloride and 1500 g of analytically pure solid sodium sulfate in 1000 L of low permeability membrane produced water and stirring for 5 minutes.

[0010] Furthermore, after the test liquid is passed through in step 1), under the premise of controlling the inlet pressure and the concentrated water flow rate of the test, the membrane water is obtained and the total dissolved solids are detected to calculate the salinity. The old reverse osmosis membrane with a salinity of less than 15% is recorded as a low-salinity membrane; the old membrane with a salinity of ≥15% is passed through a sodium hypochlorite solution for cyclic oxidation, and finally the desalination rate is reduced to 45% to 50%. At this time, the membrane is recorded as a high-salinity membrane.

[0011] Furthermore, when the test liquid is introduced for testing, the water inlet pressure is controlled to be between 1.0-1.5 MPa, and the concentrated water flow rate accounts for 13-15% of the total water inlet flow rate.

[0012] Furthermore, in step 1), the concentration of the sodium hypochlorite solution is 1%-3%, and the cycle oxidation time is 1-3 hours.

[0013] Furthermore, in step 2), the concentration of sodium carbonate added is N, and the hardness concentration of the hardness removal resin regeneration waste liquid after mixing with the high permeability salt membrane concentrated water is N2, then the N addition concentration is 0.75×N2 to 1.05×N2.

[0014] Furthermore, the amount of sodium hydroxide added in step 2) is based on controlling the reaction pH to 11.3-11.7.

[0015] Furthermore, in step 2), the high salt permeability membrane system controls the membrane water flux to be 18-20 L / ㎡·h and the water recovery rate to be 65%-70%.

[0016] Furthermore, in step 2), the high salt permeability membrane is shut down and flushed every 6-10 hours to reduce the concentration of pollutants on the membrane surface.

[0017] Furthermore, in step 3), the low permeability membrane system controls the membrane water flux to be 20-22 L / ㎡·h and the water recovery rate to be 73%-76%.

[0018] The beneficial effects of the method for treating coking wastewater by removing hard resin and regenerating waste liquid by using old reverse osmosis membrane of the present invention are as follows:

[0019] The method of the present invention pre-treats the old reverse osmosis membrane, first performs high-flow flushing, then detects the salinity of the old reverse osmosis membrane after cleaning, and oxidizes the old reverse osmosis membrane according to the test results to convert it into a high-salt permeability membrane and a low-salt permeability membrane; first adds a chemical stabilizer to the hardness-removing resin regeneration waste liquid to stabilize the pH and hardness and convert the calcium and magnesium hardness in the resin regeneration waste liquid into sludge, and then sequentially performs high-salt permeability membrane filtration and low-salt permeability membrane filtration on the stabilized supernatant to desalinate the supernatant and convert it into product water for reuse. Through the implementation of the above method, the impact problem after the resin regeneration waste liquid returns to the water treatment system can be eliminated, and at the same time, a new way of resource utilization of old reverse osmosis membranes has been expanded.

[0020] The present invention develops a new utilization approach for old reverse osmosis membranes by simply treating old reverse osmosis membranes to remove hard resin from coking wastewater and regenerate waste liquid. In particular, when the old reverse osmosis membranes used come from one's own coking wastewater treatment membrane system, the membrane elements that are often considered to have lower utilization value are effectively reused for the second time. At the same time, since old membranes are used, the cost of membrane replacement is extremely low, which is beneficial to related industry enterprises, especially coking wastewater treatment enterprises, to actively promote, reduce costs and increase efficiency.

[0021] The present invention uses chemical dosing to preliminarily precipitate the hardness in the hardness removal resin of coking wastewater, uses pretreated old reverse osmosis membrane elements for high-salt permeability filtration, returns the generated high-hardness concentrated water to continue chemical dosing to precipitate the hardness, and then performs low-salt permeability filtration on the generated produced water with a high sodium chloride content, and feeds the generated concentrated water with an extremely high sodium chloride content into an evaporation crystallization system to prepare industrial sodium chloride. The generated produced water with a low salt content is used for system preparation and flushing, and the excess produced water is sent out for production. The present invention actively explores the resource utilization of the regeneration waste liquid of the hardness removal resin of coking wastewater, and solves the problem of a large impact caused by the resin regeneration waste liquid after it flows back to the water treatment system. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present invention are described clearly and completely below. In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention can also be implemented in other ways different from those described herein, and those skilled in the art can make similar generalizations without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0023] A method for treating coking wastewater by using old membrane to remove hard resin regeneration waste liquid comprises the following steps:

[0024] Step 1): The old reverse osmosis membrane is flushed with a high flow rate, and then the test liquid is passed through. Under the premise of controlling the inlet pressure and the concentrated water flow rate of the test, the membrane water is obtained and the total dissolved solids (TDS) thereof is detected, and then the salinity thereof is calculated. The old reverse osmosis membrane with a salinity of less than 15% is a low-salinity membrane. The old membrane with a salinity of ≥15% is passed through a sodium hypochlorite solution for cyclic oxidation, and finally its desalination rate is reduced to 45% to 50%. At this time, the membrane is a high-salinity membrane. The difference between the high-salinity membrane and the low-salinity membrane is that the retention rate of ions is different, that is, the retention rate of chloride ions and sodium ions of the high-salinity membrane is lower than that of the low-salinity membrane.

[0025] The test solution is prepared as follows: 3000g of analytically pure solid sodium chloride and 1500g of analytically pure solid sodium sulfate are dissolved in 1000L of low-permeability membrane water, and stirred for 5 minutes; after the test solution is introduced, the membrane water is obtained and its total dissolved solids (TDS) are detected under the premise that the inlet pressure of the test is controlled between 1.0-1.5Mpa and the concentrated water flow accounts for 13-15% of the total inlet flow, and then its salinity is calculated. The old reverse osmosis with a salinity of <15% is recorded as a low-permeability membrane; the old membrane with a salinity of ≥15% is passed through a sodium hypochlorite solution for cyclic oxidation, and finally its desalination rate is reduced to 45% to 50%, and the membrane at this time is recorded as a high-permeability membrane; the concentration of the sodium hypochlorite solution is 1%-3%, and the cyclic oxidation time is 1-3 hours.

[0026] Step 2): sodium hydroxide and sodium carbonate are added to the hardness removal resin regeneration waste liquid, stirred, and the chemical sludge produced by the reaction is dehydrated. The supernatant after the reaction is passed through the high-permeability salt membrane obtained in step 1), and the high-permeability salt membrane concentrated water is refluxed to continue to add sodium hydroxide and sodium carbonate; the concentration of added sodium carbonate is N, and the hardness concentration after the hardness removal resin regeneration waste liquid and the high-permeability salt membrane concentrated water are mixed is N2, then the N addition concentration is 0.75×N2 to 1.05×N2; the amount of sodium hydroxide added is based on controlling the reaction pH to 11.3-11.7, preferably 11.5; the high-permeability salt membrane system controls the membrane water flux to be 18-20L / ㎡·h and the water recovery rate to be 65%-70%; the high-permeability salt membrane is shut down and rinsed every 6-10 hours to reduce the concentration of pollutants on the membrane surface.

[0027] Step 3): The high permeability salt membrane water of step 2) is passed into the low permeability salt membrane obtained in step 1), and the low permeability salt concentrated water is sent to the outside of the system for ultra-high pressure concentration or evaporation crystallization system to extract sodium chloride. The low permeability salt membrane water is used for high flow flushing and test liquid preparation in step 1, and the excess low permeability salt membrane water is sent out as product water. The low permeability salt membrane system controls the membrane water flux to be 20-22L / ㎡·h and the water recovery rate to be 73%-76%.

[0028] Example 1

[0029] A case in which a chemical production workshop of a coking plant used the old reverse osmosis membrane eliminated from its own system to treat its hardness removal resin regeneration waste liquid. The old reverse osmosis membrane model was BW30XFR-400 / 34, and the hardness removal resin model was D113. The average daily amount of hardness removal resin regeneration waste liquid produced was 270m3, and its total hardness content was 4500mg / L.

[0030] (1) The old membrane was flushed at a high flow rate. The flushing water was heated with steam and maintained at 38°C. The flushing flow rate was 6m3 / h. Due to the serious fouling of the membrane, the membrane was flushed in the reverse direction after the forward flushing.

[0031] (2) Take 3000g of analytically pure solid sodium chloride and 1500g of analytically pure solid sodium sulfate and dissolve them in 1000L of low-salinity membrane produced water, stir for 5 minutes to prepare the test solution, control the test water inlet pressure of the old reverse osmosis membrane to 1.05Mpa, and the recovery rate is 13%. After testing, the salt permeability of the old reverse osmosis membrane after flushing is within 15%, accounting for 30%, marked as low-salinity membrane, and numbered D1-D75, and the salt permeability of the remaining membranes is above 15%;

[0032] (3) Install the old reverse osmosis membrane with a salt permeability of more than 15% into the membrane shell, prepare 2% sodium hypochlorite solution, circulate for 1.2 hours, and detect that the proportion of those with a salt permeability of 45%-50% is 80%, and the proportion of those with a salt permeability of 50%-55% is 20%. The old reverse osmosis membrane with a salt permeability of 50%-55% continues to circulate and oxidize for 1.0 hour, and the salt permeability can reach the standard of 45%-50%. The old reverse osmosis membranes with a salt permeability of 45%-50% are marked as high salt permeability membranes and numbered G1-G175 for standby use;

[0033] (4) Add 3800 mg / L of sodium carbonate and 545 mg / L of liquid caustic soda to the hardness removal resin regeneration waste liquid, control the reaction pH to 11.55, stir for 10 minutes, and perform plate-frame dehydration on the chemical sludge produced by the reaction. The dehydrated filtrate is refluxed to the front end of the reaction. The dehydrated sludge has a moisture content of 65% and is used for coal blending in the coking plant. The supernatant after the reaction is tested to have a total hardness removal rate of 91%. The high-permeability salt membrane device introduced is divided into two sections after on-site reuse and transformation, with 18 membranes in the first section and 9 membranes in the second section. The recovery rate of the high-permeability salt membrane device is controlled to be 67% and the water flux is 18 L / ㎡·h. The high-permeability salt membrane device is shut down for flushing once every 6 hours, and the flushing water flow rate is 60 m3 / h. The flushing water and the high-permeability salt membrane concentrated water are refluxed to the front end to continue to add sodium hydroxide and sodium carbonate;

[0034] (5) The high-permeability salt membrane produced water is passed into the low-permeability salt membrane device. The low-permeability salt membrane device is newly built and is divided into two sections, with 4 branches in the first section and 2 branches in the second section. The recovery rate of the low-permeability salt membrane device is controlled to be 73% and the water flux is 20.5L / ㎡·h. The concentrated water of the low-permeability salt membrane device is sent to the ultra-high pressure reverse osmosis prepared by the workshop for further concentration. The produced water of the low-permeability salt membrane device is used for high-flow flushing of the old reverse osmosis membrane and preparation of test liquid. The excess low-permeability salt membrane produced water is used as preparation water for dissolving lime and PAC in the pretreatment section of the workshop.

[0035] Through the implementation of the above plan, an average of 190m3 of product water is generated every day for reagent preparation, 72m3 of concentrated water is used for ultra-high pressure concentration, and 2.07t of chemical sludge is used for coal preparation, which solves the impact of hard resin wastewater removal and saves water for workshop preparation.

[0036] The relevant treated water quality is shown in Table 1:

[0037] Table 1 (To facilitate the observation of trends, the following data are the average values ​​of 10 rounds of processing)

[0038]

[0039] Example 2

[0040] The wastewater treatment workshop of a steel plant used the old reverse osmosis membrane eliminated from the desalting water workshop to treat its hardness removal resin regeneration waste liquid. The old reverse osmosis membrane model was CR100, and the hardness removal resin model was D113. The average daily hardness removal resin regeneration waste liquid production was 120m3, and its total hardness content was 1890mg / L.

[0041] (1) Flush the old membrane at a high flow rate, use electric heating to heat the flushing water and maintain it at 39°C, with a flushing flow rate of 7m3 / h;

[0042] (2) Take 3000g of analytically pure solid sodium chloride and 1500g of analytically pure solid sodium sulfate and dissolve them in 1000L of low-salinity membrane produced water, stir for 5 minutes to prepare the test solution, control the test water inlet pressure of the old reverse osmosis membrane to 1.00Mpa, and the recovery rate is 14%. After testing, the salt permeability of the old reverse osmosis membrane after flushing is within 15%, accounting for 90%, marked as low-salinity membrane, and numbered D1-D108. The salt permeability of the remaining membranes is above 15%;

[0043] (3) Install the old reverse osmosis membrane with a salt permeability of more than 15% into the membrane shell, prepare 2.5% sodium hypochlorite solution, circulate for 1 hour, and test the salt permeability of the membrane to be 45%-50%. Mark it as a high salt permeability membrane and number it G1-G12 for standby use;

[0044] (4) 1990 mg / L of sodium carbonate and 330 mg / L of liquid caustic soda were added to the hardness removal resin regeneration waste liquid, the reaction pH was controlled to 11.6, and the mixture was stirred for 10 minutes. The chemical sludge produced by the reaction was subjected to plate-and-frame dehydration, and the dehydrated filtrate was refluxed to the front end of the reaction. The moisture content of the dehydrated sludge was tested to be 70% and used for coal blending in the coking plant. The total hardness removal rate of the supernatant after the reaction was tested to be 93%. The high permeability salt membrane device into which the liquid was passed was divided into two sections after on-site reuse and transformation, with 8 membranes in the first section and 4 membranes in the second section. The recovery rate of the high permeability salt membrane device was controlled to be 65% and the water flux was controlled to be 19 L / ㎡·h. The high permeability salt membrane device was shut down for flushing once every 4 hours, and the flushing water flow rate was 45 m3 / h. The flushing water and the high permeability salt membrane concentrated water were refluxed to the front end to continue to add sodium hydroxide and sodium carbonate;

[0045] (5) The water produced by the high-permeability salt membrane is passed into the low-permeability salt membrane device. The low-permeability salt membrane device is newly built and divided into two sections, with 12 branches in the first section and 6 branches in the second section. The recovery rate of the low-permeability salt membrane device is controlled to be 75% and the water flux is 21.5L / ㎡·h. The concentrated water of the low-permeability salt membrane device is sent to the ultra-high pressure reverse osmosis system of the workshop water treatment system for further concentration treatment. The water produced by the low-permeability salt membrane device is flushed with the old reverse osmosis membrane at a high flow rate and prepared with test fluid. The excess water produced by the low-permeability salt membrane is used as a preparation water for dissolving lime and sodium carbonate in the high-density pool of the water treatment system.

[0046] Through the implementation of the above plan, an average of 86m3 of product water is generated every day for reagent preparation, 32m3 of concentrated water is used for ultra-high pressure concentration, and 1.35t of chemical sludge is used for coal preparation, which solves the impact of hard resin wastewater removal and saves water for workshop preparation.

[0047] The relevant treated water quality is shown in Table 2:

[0048] Table 2 (In order to facilitate the observation of trends, the following data are taken as the average of 5 rounds of processing)

[0049]

[0050] Example 3

[0051] The difference between the treatment schemes of Example 3 and Example 2 is that, in addition to treating the de-hardening resin regeneration wastewater, this embodiment also treats 5m3 / h of immersion ultrafiltration cleaning emptying water (due to the high conductivity of the water in the immersion ultrafiltration membrane pool, direct emptying and refluxing the front end will cause a conductivity shock to the system). This embodiment uses the method provided by the present invention to treat its resin regeneration waste liquid and immersion ultrafiltration emptying water. The used reverse osmosis membrane model used is CR100, and the de-hardening resin model is D113. The average daily production of de-hardening resin regeneration waste liquid and immersion ultrafiltration emptying water is 90m3, and its total hardness content is 2250mg / L.

[0052] (1) Flush the old membrane at a high flow rate, use electric heating to heat the flushing water and maintain it at 39°C, with a flushing flow rate of 7m3 / h;

[0053] (2) Take 3000g of analytically pure solid sodium chloride and 1500g of analytically pure solid sodium sulfate and dissolve them in 1000L of low-salinity membrane produced water, stir for 5 minutes to prepare the test solution, control the test water inlet pressure of the old reverse osmosis membrane to 1.00Mpa, and the recovery rate is 14%. After testing, the salt permeability of the old reverse osmosis membrane after flushing is within 15%, accounting for 50%, marked as low-salinity membrane, and numbered D1-D90. The salt permeability of the remaining membranes is above 15%;

[0054] (3) Install the old reverse osmosis membrane with a salt permeability of more than 15% into the membrane shell, prepare 2.5% sodium hypochlorite solution, circulate for 1 hour, and test the salt permeability of the membrane to be 45%-50%. Mark it as a high salt permeability membrane and number it G1-G90 for standby use;

[0055] (4) 1730 mg / L of sodium carbonate and 280 mg / L of liquid caustic soda were added to the hardness removal resin regeneration wastewater and the immersion ultrafiltration evacuation water, and the reaction pH was controlled to 11.6. The mixture was stirred for 10 minutes, and the chemical sludge produced by the reaction was subjected to plate-and-frame dehydration. The dehydrated filtrate was refluxed to the front end of the reaction. The moisture content of the dehydrated sludge was tested to be 70% for coal blending treatment. The total hardness removal rate of the supernatant after the reaction was tested to be 92%. The high permeability salt membrane device into which the liquid was passed was divided into two sections after on-site reuse and transformation, with 8 membranes in the first section and 4 membranes in the second section. The recovery rate of the high permeability salt membrane device was controlled to be 65% and the water production flux was 19 L / ㎡·h. The high permeability salt membrane device was shut down for flushing once every 4 hours, and the flushing water flow rate was 45 m3 / h. The flushing water and the high permeability salt membrane concentrated water were refluxed to the front end to continue to add sodium hydroxide and sodium carbonate;

[0056] (5) The water produced by the high-permeability salt membrane is passed into the low-permeability salt membrane device. The low-permeability salt membrane device is newly built and is divided into two sections, with 12 branches in the first section and 6 branches in the second section. The recovery rate of the low-permeability salt membrane device is controlled to be 75% and the water flux is 21.5L / ㎡·h. The concentrated water of the low-permeability salt membrane device is sent to the evaporation and crystallization workshop to prepare mixed salt. The water produced by the low-permeability salt membrane device is flushed with high-flow reverse osmosis old membrane and prepared with test fluid. The excess water produced by the low-permeability salt membrane is used as a preparation water for dissolving lime and sodium carbonate in the high-density pool of the reclaimed water treatment system.

[0057] Through the implementation of the above plan, an average of 65m3 of product water is generated every day for reagent preparation, 24m3 of concentrated water is used for ultra-high pressure concentration, and 0.86t of chemical sludge is used for coal preparation, which solves the impact of hard resin wastewater removal and saves water for workshop preparation.

[0058] The relevant treated water quality is shown in Table 3:

[0059] Table 3 (To facilitate the observation of trends, the following data are taken as the average of 5 rounds of processing)

[0060]

[0061]

[0062] Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Claims

1. A method for treating coking wastewater by using old membrane to remove hard resin regeneration waste liquid, characterized in that: The steps include: Step 1): flush the old reverse osmosis membrane with a high flow rate, then pass a test solution to test the salt permeability of the old reverse osmosis membrane, and record the old reverse osmosis membrane with low salt permeability as a low salt permeability membrane according to the level of the salt permeability, pass a sodium hypochlorite solution into the old reverse osmosis membrane with high salt permeability for cyclic oxidation until the desalination rate reaches a predetermined value, and record the old reverse osmosis membrane after oxidation treatment as a high salt permeability membrane for standby use; Step 2): adding sodium hydroxide and sodium carbonate to the hard resin regeneration waste liquid, stirring, dehydrating the chemical sludge produced by the reaction, passing the supernatant after the reaction into the high-permeability salt membrane obtained in step 1), and refluxing the high-permeability salt membrane concentrated water to continue adding sodium hydroxide and sodium carbonate; Step 3): The high-permeability salt membrane water of step 2) is passed into the low-permeability salt membrane obtained in step 1), and the low-permeability salt concentrated water is sent outside the system for ultra-high pressure concentration or evaporation crystallization system to extract sodium chloride. The low-permeability salt membrane water is used for high-flow flushing and test liquid preparation in step 1), and the excess low-permeability salt membrane water is sent out as product water.

2. A method for treating coking wastewater by using old membrane to remove hard resin regeneration waste liquid according to claim 1, characterized in that: The test solution in step 1) is prepared by dissolving 3000 g of analytically pure solid sodium chloride and 1500 g of analytically pure solid sodium sulfate in 1000 L of low permeability membrane produced water and stirring for 5 minutes.

3. The method for treating coking wastewater and removing hard resin regeneration waste liquid by using old membrane according to claim 1, characterized in that: After the test liquid is passed through step 1), under the premise of controlling the inlet pressure and concentrate flow rate of the test, the membrane water is obtained and the total dissolved solids are detected to calculate the salinity. The old reverse osmosis membrane with a salinity of less than 15% is recorded as a low-salinity membrane; the old membrane with a salinity of ≥15% is passed through a sodium hypochlorite solution for cyclic oxidation, and finally the desalination rate is reduced to 45% to 50%. The membrane at this time is recorded as a high-salinity membrane.

4. A method for treating coking wastewater by using old membrane to remove hard resin regeneration waste liquid according to claim 3, characterized in that: When the test liquid is passed into the test, the water inlet pressure is controlled between 1.0-1.5Mpa, and the concentrated water flow accounts for 13-15% of the total water inlet flow.

5. The method for treating coking wastewater and removing hard resin regeneration waste liquid by using old membrane according to claim 1, characterized in that: In step 1), the concentration of the sodium hypochlorite solution is 1%-3%, and the cycle oxidation time is 1-3 hours.

6. The method of treating coking wastewater and removing hard resin regeneration waste liquid by using old membrane according to claim 1, characterized in that: The concentration of sodium carbonate added in step 2) is N, and the hardness concentration of the hardness removal resin regeneration waste liquid mixed with the high permeability salt membrane concentrated water is N2, so the N addition concentration is 0.75×N2 to 1.05×N2.

7. The method for treating coking wastewater and removing hard resin regeneration waste liquid by using old membrane according to claim 1, characterized in that: The amount of sodium hydroxide added in step 2) is based on controlling the reaction pH to 11.3-11.

7.

8. The method for treating coking wastewater and removing hard resin regeneration waste liquid by using old membrane according to claim 1, characterized in that: Step 2) The medium and high permeability salt membrane system controls the membrane water flux to be 18-20 L / ㎡·h and the water recovery rate to be 65%-70%.

9. The method for treating coking wastewater and removing hard resin regeneration waste liquid by using old membrane according to claim 1, characterized in that: Step 2) The medium and high permeability salt membrane is shut down and flushed every 6-10 hours to reduce the concentration of pollutants on the membrane surface.

10. The method for treating coking wastewater and removing hard resin regeneration waste liquid by using old membrane according to claim 1, characterized in that: Step 3) The low-salt permeability membrane system controls the membrane water flux to be 20-22 L / ㎡·h and the water recovery rate to be 73%-76%.

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