Method and device for treating ammonia-nitrogen water generated in surfactant production

Abstract

The invention belongs to the field of chemical engineering, and particularly relates to a treatment method and device for ammonia-nitrogen water generated by surfactant production, and the treatment method comprises the following steps: step 1, performing coarse filtration on the ammonia-nitrogen water generated by a surfactant production system through a coarse filtration system to remove solid impurities; 2, the ammonia nitrogen water is filtered by a first-stage membrane system, and first-stage concentrated water and first-stage clear water are obtained after filtering; primary clear water enters an intermediate tank; 3, filtering the first-stage clear water by a second-stage membrane system to obtain second-stage concentrated water and second-stage clear water; the secondary concentrated water flows back to the intermediate tank, and part of liquid in the intermediate tank is recycled to a surfactant production system. According to the method, various nanofiltration membranes are selected, production requirements are combined, a sewage treatment method with concentrated liquid capable of being recycled to a production system and clear water emission reaching the standard is explored, and the basic purpose can be achieved only through a first-stage nanofiltration membrane.

Description

Technical Field

[0001] The invention belongs to the field of chemical industry, and particularly relates to a method and device for treating ammonia nitrogen water generated in the production of surfactants. Background Art

[0002] Bulk surfactants are important daily chemical raw materials. As key functional ingredients, they are widely used in products such as skincare and cosmetics, and possess high market value. However, their production and preparation generate a certain amount of wastewater containing ammonia nitrogen, high COD, and total nitrogen values. If this wastewater is not promptly and effectively addressed, it can lead to wastewater accumulation, stalling product production and causing significant economic losses.

[0003] At present, the methods for treating ammonia nitrogen in industrial water include distillation, air stripping, chemical precipitation, biochemical oxidation, ion exchange and other methods. Although the above methods can solve the problem of reducing the ammonia nitrogen value in wastewater in a short period of time to a certain extent, they have defects such as high energy consumption, low treatment efficiency, large equipment footprint, and environmental pollution (many by-products) in the long-term treatment cycle.

[0004] In the applicant's previous research, we experimented with various nanofiltration membranes to filter this type of wastewater. Since this type of wastewater contains a large amount of small molecular organic amines, the total nitrogen content in the clean water remains high. In order to control the total nitrogen content in the clean water, we have to use a multi-stage nanofiltration system for repeated filtration.

[0005] The technical problem to be solved in this case is: how to achieve the reuse of sewage raw materials using only one-stage nanofiltration membrane and control the discharge of clean water to approach or reach below 100ppm of total nitrogen. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a method for treating ammonia nitrogen water produced by surfactant production. This method selects the nanofiltration membrane in advance, combines the characteristics of organic matter in the ammonia nitrogen wastewater, and combines the production requirements of the surfactant production system. After repeated debugging, a wastewater treatment method has been developed that can produce a large amount of clean water, the concentrate can be reused in the production system, and the clean water discharge meets the standards. This method only requires a first-level nanofiltration membrane to achieve the basic purpose.

[0007] At the same time, the invention also provides a system suitable for the method.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions: A method for treating ammonia nitrogen water produced in surfactant production comprises the following steps: Step 1: The ammonia nitrogen water produced by the surfactant production system is coarsely filtered through a coarse filtration system to remove solid impurities in the ammonia nitrogen water; Step 2: Filter the ammonia nitrogen water through a primary membrane system to obtain primary concentrated water and primary clean water; the primary clean water enters the intermediate tank; the pH of the intermediate tank is adjusted to 10±0.5; Step 3: The primary clean water is filtered through a secondary membrane system to obtain secondary concentrated water and secondary clean water. The secondary concentrated water is returned to the intermediate tank, and part of the liquid in the intermediate tank is reused in the surfactant production system. The membrane used in the primary membrane system is a ceramic membrane or a silicon carbide membrane; the membrane used in the secondary membrane system is a polyamide (PA) nanofiltration membrane; In step 2, the membrane inlet pressure is controlled to 0.3-0.4 MPa, and the concentration ratio of the clear liquid to the concentrated liquid is 5-7:1; In step 3, the membrane inlet pressure is controlled to 2.9-3.1 MPa, and the concentration ratio of the clear liquid to the concentrated liquid is 6-9:1.

[0009] After trial operation, this solution can treat 16 tons of ammonia nitrogen wastewater and produce 12 tons of clear liquid; After research, the output efficiency of clear liquid is related to the following factors: 1. pH control of the intermediate tank; 2. Secondary membrane filtration process control; 3. Selection of nanofiltration membrane; Specifically, the pH of the stock solution is highly alkaline, with a pH range of 11-12. The filtration efficiency of the nanofiltration membrane is highest under neutral or slightly acidic conditions. However, if the solution is neutralized to neutral or slightly acidic conditions, organic bases such as propylene diamine in the ammonia nitrogen water will be completely neutralized, making it impossible to reuse the raw materials in the production system. The present invention adjusts the pH to a moderate 10±0.5, which can optimize multiple performance factors such as filtration efficiency, membrane cleaning cycle, and raw material reusability. Taking the stock solution selected in the experiment as an example, its pH is 11.2~11.8, and the content of propylene diamine is 500~800mg.L -1 When the pH of the solution is adjusted to 10±0.5, propylenediamine is neutralized first, and part of it forms organic ammonium chloride. Other macromolecular organic amines in ammonia nitrogen water, such as cocamidopropyl dimethylamine, are basically not quaternized or are quaternized in small amounts under this pH condition.

[0010] Small molecule organic amines that are pre-neutralized have the following advantages: 1. Propylenediamine is a compound with amine groups at both ends. Although its molecular weight is small, when both amine groups are neutralized, the ammonium groups formed will significantly increase the molecular radius of propylenediamine, making it easier to be adsorbed and intercepted by nanofiltration membranes. Propylenediamine is the ammonia nitrogen that is most likely to appear in clean water in wastewater, and it can significantly reduce the total nitrogen content in clean water. However, if it is not neutralized to the above pH and exists at a higher pH (such as pH 11), the total nitrogen content in the wastewater will be difficult to control.

[0011] 2. Polyamide nanofiltration membranes are often negatively charged due to the ionization of carboxyl and amino groups (zeta potential is -10~-50 mV when pH>3). During filtration, they will bind to cationic substances. Therefore, this type of nanofiltration membrane has significant advantages in intercepting high-valent metal ions. In the present invention, the polyamide nanofiltration membrane preferentially combines with the neutralized propylenediamine to form a cationic propylenediamine layer on the surface of the membrane, and its filter pores are not easily clogged; it has a longer cleaning cycle. If the ammonia nitrogen water is neutralized to a lower pH value (such as pH 9±0.5), cocamidopropyl dimethylamine will be adsorbed by the nanofiltration membrane and accelerate the clogging of the filter pores.

[0012] 3. Appropriate pH neutralization allows the concentrate to be reused in the production system. Under stable operating conditions, the concentrate is returned to the intermediate tank, and the pH of the liquid in the intermediate tank is maintained at 10±0.5. When it is reused in the production system, the pH can be restored to 11~12 after raw material preparation, maintaining the liquid in the intermediate tank at an optimal concentration state that can be utilized by the production system.

[0013] In addition, the concentration ratio needs to be strictly controlled in the present invention. By controlling the concentration ratio of the nanofiltration membrane, the total nitrogen content in the clear liquid can be controlled to be lower than 110 mg / L; when the concentration ratio is less than 6, its efficiency is too low, and when the concentration ratio is greater than 9, the total nitrogen content in the product exceeds the standard.

[0014] In the above treatment method, the flow rate of the intermediate tank recycled to the surfactant production system is 0.32~0.75m³ / h.

[0015] In the above-mentioned treatment method, the liquid recycled from the intermediate tank to the surfactant production system first enters a concentrate tank, and after being mixed in the concentrate tank, it reaches the application standard required by the surfactant production system; The primary concentrated water flows back to the inlet of the coarse filtration system.

[0016] In the above treatment method, the specification of the ammonia nitrogen water is COD: 9000~10000mg·L -1 Total nitrogen: 7500~8500mg·L -1 .

[0017] In the above treatment method, the discharge standard of the secondary clean water is COD≤500mg / L, total nitrogen≤110mg / L.

[0018] At the same time, the present invention also discloses a device for implementing the above method, including a concentrate tank and a wastewater tank, a coarse filtration system, a primary membrane system, an intermediate tank, and a secondary membrane system connected in sequence; the inlet of the primary membrane system is connected to the outlet of the coarse filtration system; the clear liquid outlet of the primary membrane system is connected to the inlet of the intermediate tank; the concentrate outlet of the primary membrane system is connected to the wastewater tank through a first circulation pump; the inlet of the secondary membrane system is connected to the outlet of the intermediate tank; the concentrate outlet of the secondary membrane system is connected to the inlet of the intermediate tank through a second circulation pump; and a first pump is provided between the outlet of the intermediate tank and the concentrate tank.

[0019] In the above device, the inlet of the primary membrane system and the inlet of the secondary membrane system are respectively connected to a feed pump and a booster pump; A temperature sensor is provided in the intermediate tank; a liquid level sensor is provided in the waste water tank, and the liquid level sensor is linked to the first circulation pump.

[0020] The above device further comprises an acid liquid tank, wherein the intermediate tank is provided with a pH sensor; the clear liquid outlet of the secondary membrane system is connected to a clear water tank via a second pump.

[0021] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention only requires the use of a primary nanofiltration membrane to achieve the dual goals of clear liquid discharge and concentrated liquid recovery; achieving this goal requires pH control of the intermediate tank, nanofiltration membrane selection, and process control.

[0022] 2. The concentrated water of the present invention is fully reused without any discharge; the pH of the concentrated water returned to the production system is 10±0.5, and after mixing with raw materials such as propylene diamine, it is restored to the pH value required by the system, with little impact on the pH of the production system, fully meeting the raw material requirements of the production system. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a flow chart of the ammonia nitrogen water treatment device of the present invention. DETAILED DESCRIPTION

[0024] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0025] Before describing the method of the present invention, the ammonia nitrogen water treatment device of the present invention is described first. Specifically: Figure 1The ammonia nitrogen water treatment device of the present invention includes a concentrate tank 12 and a wastewater tank 1, a coarse filtration system 2, a primary membrane system 3, an intermediate tank 4, and a secondary membrane system 5 connected in sequence; the coarse filtration system 2 of this device is selected as a rod filter; the inlet of the primary membrane system 3 is connected to the outlet of the coarse filtration system 2; the clear liquid outlet of the primary membrane system 3 is connected to the inlet of the intermediate tank 4; the concentrate outlet of the primary membrane system 3 is connected to the wastewater tank 1 through a first circulation pump 6; the inlet of the secondary membrane system 5 is connected to the outlet of the intermediate tank 4; the concentrate outlet of the secondary membrane system 5 is connected to the inlet of the intermediate tank 4 through a second circulation pump 7; the clear liquid outlet of the secondary membrane system 5 is connected to the second pump 13 and the clean water tank 14; a first pump 8 is provided between the outlet of the intermediate tank 4 and the concentrate tank 12, and the inlet of the primary membrane system 3 and the inlet of the secondary membrane system 5 are respectively connected to a feed pump 9 and a booster pump 10; a temperature sensor is provided in the intermediate tank 4; a liquid level sensor is provided in the wastewater tank 1, and the liquid level sensor is linked to the first circulation pump 6. In addition, the device of the present invention also includes an acid liquid tank 11, and a pH sensor is provided in the intermediate tank 4; the outlet of the acid liquid tank 11 and the inlet of the intermediate tank 4 are connected by a pipeline, and the acid liquid tank 11 injects the acid liquid into the intermediate tank 4 by pressurizing; an electromagnetic valve is provided on the pipeline, and the electromagnetic valve and the pH sensor are linked.

[0026] In production, the system of the present invention can be implemented in either continuous or intermittent production. If operated intermittently, a single batch can process 16 tons of ammonia nitrogen-rich water. Subsequent cases will all utilize intermittent production. After each production run, the differential pressure across the secondary membrane system is measured to determine whether membrane cleaning is necessary.

[0027] Example 1 A method for treating ammonia nitrogen wastewater comprises the following steps: Step 1: coarse filtration; Use rod filter for coarse filtration, the water flow rate is 16m 3 / h; The COD of ammonia nitrogen water is 9726.25 mg·L -1 Total nitrogen: 8004.07 mg·L -1 , pH 11.4, propylene diamine content 687.34 mg·L -1 ; This water sample was used for experiments in all subsequent cases.

[0028] Step 2: Primary membrane filtration The membrane core assembly of the primary membrane system uses a 50nm silicon carbide membrane. Turn on the first circulation pump, open the manual valves before and after the membrane core assembly, the manual valve for the concentrate to wastewater tank, the manual valve for the concentrate reflux regulation, the manual valve for the clear liquid extraction, and the manual valve for the clear liquid to the intermediate tank; Wastewater is transported into the primary membrane system, and the regulating valve is interlocked with the clear liquid extraction flowmeter. During the filtration process, the membrane inlet pressure is controlled to 0.4MPa, and the concentration ratio (clear liquid: concentrated liquid) is 7:1. When the liquid level in the intermediate tank reaches 1.82m, the secondary membrane filtration begins.

[0029] Step 3: Secondary membrane filtration The pH of the intermediate tank is adjusted to 10±0.5 by using hydrochloric acid in the acid tank. A temperature control jacket is provided outside the intermediate tank, and the water temperature of the intermediate tank is controlled to 45±5℃ by a circulating water pump; Open the feed pump, the manual valves before and after the booster pump, the manual valves before and after the membrane core assembly, the manual valve for the concentrate to go to the intermediate tank, the manual valve for the concentrate reflux regulation, and the manual valve for the clear liquid production. Start the feed pump and the booster pump through the PLC control panel to transport the wastewater into the secondary membrane system; interlock the regulating valve with the clear liquid production flowmeter; during the filtration process, control the membrane inlet pressure to 3.0MPa, the concentration ratio (clear liquid: concentrate) to 7:1, and the water sample temperature in the intermediate tank to 45±5℃.

[0030] The membrane core component of the secondary membrane system uses polyamide nanofiltration membrane with a pore size of 1~2nm; After the production stabilizes, open the manual valve from the intermediate tank to the concentrate tank, and use the first pump to pump the liquid in the intermediate tank into the concentrate tank at a rate of 0.6m³ / h. After the liquid in the concentrate tank is prepared, it is used as the raw liquid of the surfactant production system; the clear liquid produced by the secondary membrane system can be directly discharged after passing the inspection in the clear water tank.

[0031] Example 2 A method for treating ammonia nitrogen wastewater comprises the following steps: Step 1: coarse filtration; Use rod filter for coarse filtration, the water flow rate is 16m 3 / h.

[0032] Step 2: Primary membrane filtration The membrane core assembly of the primary membrane system uses a 50nm silicon carbide membrane. Turn on the first circulation pump, open the manual valves before and after the membrane core assembly, the manual valve for the concentrate to wastewater tank, the manual valve for the concentrate reflux regulation, the manual valve for the clear liquid extraction, and the manual valve for the clear liquid to the intermediate tank; Wastewater is transported into the primary membrane system, and the regulating valve is interlocked with the clear liquid extraction flowmeter. During the filtration process, the membrane inlet pressure is controlled to 0.3MPa, and the concentration ratio (clear liquid: concentrated liquid) is 5:1. When the liquid level in the intermediate tank reaches 1.65m, the secondary membrane filtration begins.

[0033] Step 3: Secondary membrane filtration The pH of the intermediate tank is adjusted to 10±0.5 by using hydrochloric acid in the acid tank. A temperature control jacket is provided outside the intermediate tank, and the water temperature of the intermediate tank is controlled to 45±5℃ by a circulating water pump; Open the feed pump, the manual valves before and after the booster pump, the manual valves before and after the membrane core assembly, the manual valve for the concentrate to go to the intermediate tank, the manual valve for the concentrate reflux regulation, and the manual valve for the clear liquid production. Start the feed pump and the booster pump through the PLC control panel to transport the wastewater into the secondary membrane system; interlock the regulating valve with the clear liquid production flowmeter; during the filtration process, control the membrane inlet pressure to 2.9MPa, the concentration ratio (clear liquid: concentrate) to 6:1, and the water sample temperature in the intermediate tank to 45±5℃.

[0034] The membrane core assembly of the two-stage membrane system is the same as that of Example 1; After the production stabilizes, open the manual valve from the intermediate tank to the concentrate tank, and use the first pump to pump the liquid in the intermediate tank into the concentrate tank at a rate of 0.7m³ / h. After the liquid in the concentrate tank is adjusted, it is used as the raw liquid of the surfactant production system; the clear liquid produced by the secondary membrane system can be directly discharged after passing the inspection in the clear water tank.

[0035] Example 3 A method for treating ammonia nitrogen wastewater comprises the following steps: Step 1: coarse filtration; Use rod filter for coarse filtration, the water flow rate is 16m 3 / h.

[0036] Step 2: primary membrane filtration; The membrane core assembly of the primary membrane system uses a 50nm silicon carbide membrane. Turn on the first circulation pump, open the manual valves before and after the membrane core assembly, the manual valve for the concentrate to wastewater tank, the manual valve for the concentrate reflux regulation, the manual valve for the clear liquid extraction, and the manual valve for the clear liquid to the intermediate tank; Wastewater is transported into the primary membrane system, and the regulating valve is interlocked with the clear liquid extraction flowmeter. During the filtration process, the membrane inlet pressure is controlled to 0.3~0.4MPa, and the concentration ratio (clear liquid: concentrated liquid) is 6:1. When the liquid level in the intermediate tank reaches 1.65m, the secondary membrane filtration begins.

[0037] Step 3: Secondary membrane filtration; The pH of the intermediate tank is adjusted to 10±0.5 by using hydrochloric acid in the acid tank. A temperature control jacket is provided outside the intermediate tank, and the water temperature of the intermediate tank is controlled to 45±5℃ by a circulating water pump; Open the feed pump, the manual valves before and after the booster pump, the manual valves before and after the membrane core assembly, the manual valve for the concentrate to go to the intermediate tank, the manual valve for the concentrate reflux regulation, and the manual valve for the clear liquid production. Start the feed pump and the booster pump through the PLC control panel to transport the wastewater into the secondary membrane system; interlock the regulating valve with the clear liquid production flowmeter; during the filtration process, control the membrane inlet pressure to 3.1MPa, the concentration ratio (clear liquid: concentrate) to 9:1, and the water sample temperature in the intermediate tank to 45±5℃.

[0038] The membrane core assembly of the two-stage membrane system is the same as that of Example 1; After the production stabilizes, open the manual valve from the intermediate tank to the concentrate tank, and use the first pump to pump the liquid in the intermediate tank into the concentrate tank at a rate of 0.56m³ / h. After the liquid in the concentrate tank is adjusted, it is used as the raw liquid of the surfactant production system; the clear liquid produced by the secondary membrane system can be directly discharged after passing the inspection in the clear water tank.

[0039] Comparative Example 1 The method is basically the same as Example 1, except that during the filtration process, the membrane inlet pressure is controlled to 2.75 MPa, the concentration ratio (clear liquid: concentrated liquid) is 5:1, and the water sample temperature in the intermediate tank is 45±5°C.

[0040] Comparative Example 2 The method is basically the same as Example 1, except that during the filtration process, the membrane inlet pressure is controlled to 3.2 MPa, the concentration ratio (clear liquid: concentrated liquid) is 12:1, and the water sample temperature in the intermediate tank is 45±5°C.

[0041] Comparative Example 3 The process is substantially the same as in Example 1, except that in step 3, the pH of the intermediate tank is adjusted to 9±0.5 using hydrochloric acid.

[0042] Comparative Example 4 The process is substantially the same as Example 1, except that in step 3, the pH in the intermediate tank is not adjusted, and the tested pH is 11.4.

[0043] Performance testing The COD and ammonia nitrogen content of the clear liquid after filtration by the secondary membrane system were tested. The test results are shown in Table 1. Table 1 Test results <![CDATA[COD / mg·L -1 ]]> <![CDATA[Total nitrogen / mg·L -1 > Example 1 452 81.51 Example 2 382.6 59.3 Example 3 406.3 107.03 Comparative Example 1 397.9 68.52 Comparative Example 2 605.1 205.43 Comparative Example 3 362.7 43.08 Comparative Example 4 635.7 218.62

[0044] Result analysis: 1. As can be seen from Examples 1 to 3, the total nitrogen content of the clear solution of the present invention is less than 110 mg·L -1 , COD value is lower than 500, and the clear liquid is close to or reaches the discharge standard; at the same time, in this case, it is only necessary to adjust the pH of the intermediate tank to 10±0.5, which can be reused in the production system without raising the pH. In the production system, raw materials such as propylene diamine will also be added. The pH of the intermediate tank solution has almost no impact on the pH stability of the production system.

[0045] 2. Comparative Examples 1 and 2 show that although a concentration ratio that is too low (Comparative Example 2) can achieve the goal of meeting discharge standards, it reduces the output of the clear liquid and increases the processing load of the nanofiltration membrane system; a concentration ratio that is too high (Comparative Example 2) cannot achieve the goal of meeting discharge standards for the clear liquid.

[0046] 3. Comparative Examples 3 and 4 show that lower pH values are beneficial for controlling the total nitrogen and COD values of clean water. However, based on the system operation process, under the operating conditions of Examples 1 to 3, the nanofiltration membrane cleaning cycle was 64 tons of ammonia nitrogen water. Under the operating conditions of Comparative Example 3, the nanofiltration membrane cleaning cycle was shortened to 16 tons of ammonia nitrogen water (the cleaning cycle was determined by a pressure difference across the membrane exceeding 20%). This indicates that when the pH drops by about 1, the nanofiltration membrane is more susceptible to clogging. At the same time, a lower pH means that when the liquid in the intermediate tank is reused in the production system, more raw materials such as propylene diamine need to be added, making it impossible to achieve the production requirements of the appropriate pH and corresponding concentration matching. In Comparative Example 4, although the nanofiltration membrane can still work normally at this pH value without adjusting the pH, it cannot achieve the discharge of clear liquid that meets the standards. At least one additional nanofiltration membrane is required to achieve the purpose of clear liquid discharge that meets the standards.

[0047] After analysis, we speculate that the selection of the nanofiltration membrane, the pH value of the intermediate tank, and the setting of the concentration ratio are key factors determining the performance of the present invention. A certain degree of neutralization can ensure that the liquid in the intermediate tank can be reused in the production system, while ensuring that the clear liquid discharge meets the standard. By controlling the pre-neutralization pH of the ammonia nitrogen water, the propylene diamine is cationized. Based on the principle of charge adsorption, the cationized propylene diamine will accumulate on the surface of the nanofiltration membrane, forming an adsorption layer on the surface of the nanofiltration membrane, which can block the passage of large molecular organic matter and prevent the filter pores from being blocked too quickly. At the same time, after the amine groups at both ends of the propylene diamine are cationized, the molecular diameter can be increased, preventing excessive propylene diamine from being introduced into the clear liquid.

[0048] In summary, the selection of the nanofiltration membrane, the concentration ratio, and the pH of the intermediate tank are the core factors that affect the realization of the purpose of the present invention.

[0049] The applicant declares that while the above-described embodiments illustrate the process of the present invention, the present invention is not limited to the above-described process steps, nor does it imply that the present invention must rely on the above-described process steps for implementation. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the raw materials used, additions of auxiliary ingredients, and selection of specific methods, etc., fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for treating ammonia nitrogen water produced by surfactant production, characterized in that: The steps include: Step 1: The ammonia nitrogen water produced by the surfactant production system is coarsely filtered through a coarse filtration system to remove solid impurities in the ammonia nitrogen water; Step 2: Filter the ammonia nitrogen water through a primary membrane system to obtain primary concentrated water and primary clean water; the primary clean water enters the intermediate tank, and the pH of the intermediate tank is adjusted to 10±0.5; Step 3: The primary clean water is filtered through a secondary membrane system to obtain secondary concentrated water and secondary clean water. The secondary concentrated water is returned to the intermediate tank, and part of the liquid in the intermediate tank is reused in the surfactant production system. The membrane used in the primary membrane system is a ceramic membrane or a silicon carbide membrane; the membrane used in the secondary membrane system is a polyamide nanofiltration membrane; In step 2, the membrane inlet pressure is controlled to 0.3-0.4 MPa, and the concentration ratio of the clear liquid to the concentrated liquid is 5-7:1; In step 3, the membrane inlet pressure is controlled to 2.9-3.1 MPa, and the concentration ratio of the clear liquid to the concentrated liquid is 6-9:

1.

2. The processing method according to claim 1, characterized in that The flow rate of the intermediate tank recycled to the surfactant production system is 0.32~0.75m³ / h.

3. The processing method according to claim 1, characterized in that The liquid recycled from the intermediate tank to the surfactant production system first enters a concentrate tank and is mixed in the concentrate tank to meet the application standards required by the surfactant production system.

4. The processing method according to claim 1, characterized in that The inlet flow rate of the ammonia nitrogen water is 15~17m 3 / h; the specification of the ammonia nitrogen water is COD: 9000~10000mg·L -1 ; Total nitrogen: 7500~8500mg·L -1 .

5. The processing method according to claim 1, characterized in that The ammonia nitrogen in the water contains no less than 500 mg·L -1 of propylenediamine.

6. The processing method according to claim 1, characterized in that The discharge standard of the secondary clean water is COD≤500mg / L and total nitrogen≤110mg / L.

7. A device for implementing the method according to any one of claims 1 to 6, characterized in that: It includes a concentrate tank and a wastewater tank, a coarse filtration system, a primary membrane system, an intermediate tank, and a secondary membrane system connected in sequence; the inlet of the primary membrane system is connected to the outlet of the coarse filtration system; the clear liquid outlet of the primary membrane system is connected to the inlet of the intermediate tank; the concentrate outlet of the primary membrane system is connected to the wastewater tank through a first circulation pump; the inlet of the secondary membrane system is connected to the outlet of the intermediate tank; the concentrate outlet of the secondary membrane system is connected to the inlet of the intermediate tank through a second circulation pump; and a first pump is provided between the outlet of the intermediate tank and the concentrate tank.

8. The device according to claim 7, characterized in that The inlet of the primary membrane system and the inlet of the secondary membrane system are respectively connected to a feed pump and a booster pump; A temperature sensor is provided in the intermediate tank; a liquid level sensor is provided in the waste water tank, and the liquid level sensor is linked to the first circulation pump.

9. The device according to claim 7, characterized in that It also includes an acid tank, and a pH sensor is provided in the intermediate tank; the clear liquid outlet of the secondary membrane system is connected to a clear water tank through a second pump.

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