Apparatus and method for treating ammonia-nitrogen wastewater with caprolactam sulfate

Abstract

The application discloses a device and a method for treating ammonia-nitrogen wastewater by using caprolactam sulfate, and the device comprises a filter, a pH value adjusting tank, a cross-flow membrane contactor assembly, a caprolactam sulfate hydrolysis tank and an absorption liquid circulating tank; the filter is connected with the pH value adjusting tank; the pH value adjusting tank is connected with a pipe passage water inlet of a first cross-flow membrane contactor; the caprolactam sulfate hydrolysis tank is connected with an absorption liquid shell passage liquid inlet of the first cross-flow membrane contactor; an absorption liquid shell passage liquid outlet of a last cross-flow membrane contactor is connected with the absorption liquid circulating tank; and the absorption liquid circulating tank is connected with an absorption liquid shell passage liquid inlet of the first cross-flow membrane contactor. The application further discloses a method for treating ammonia-nitrogen wastewater by using caprolactam sulfate. The device is simple, has a large treatment capacity, has a good ammonia removal effect, and is low in energy consumption and cost. The method has a good ammonia removal effect, is low in requirements for acid corrosion resistance of pipelines and equipment, has no extra by-products and three wastes, and realizes neutralization of caprolactam sulfate.

Description

TECHNICAL FIELD

[0001] The present application relates to a device and method for treating ammonia-nitrogen wastewater, in particular to a device and method for treating ammonia-nitrogen wastewater by using caprolactam sulfate. BACKGROUND

[0002] With the rapid development and expansion of the petrochemical industry, chemical fertilizer industry, energy regeneration industry and the like in China, the amount of high ammonia-nitrogen wastewater generated therefrom is gradually increasing. At present, the technology for treating ammonia-nitrogen wastewater in China is relatively backward, and the cost for treating ammonia-nitrogen wastewater is huge, which seriously restricts the development of the petrochemical industry and the like in China. Therefore, developing new technology for treating high ammonia-nitrogen wastewater by using an economic and effective method has become an important research topic for environmental protection workers at present, and has been highly valued by people in the industry.

[0003] Ammonia-nitrogen wastewater is generally formed due to the coexistence of ammonia water and inorganic ammonia, and mainly consists of two kinds, one is ammonia-nitrogen formed by ammonia water, and the other is ammonia-nitrogen formed by inorganic ammonia, mainly ammonium sulfate, ammonium chloride and the like. When ammonia-nitrogen in wastewater is mixed into water, it can consume a large amount of oxygen in water, easily cause damage to water, and cause harm to the ecological environment. The treatment method for high ammonia-nitrogen wastewater includes physical-chemical method and biological method. The physical-chemical method includes stripping method, zeolite ammonia removal method, reverse osmosis membrane separation technology, MAP precipitation method, ultrasonic stripping treatment of ammonia-nitrogen method and chemical oxidation method. The biological method includes A / O, two-stage activated sludge method, strong oxidation aerobic biological treatment, short-cut nitrification and denitrification method and the like. However, whether it is stripping, stripping+A / O or stripping+chemical precipitation, it cannot be separated from the pretreatment process with high investment and high operation cost.

[0004] Caprolactam is an important chemical monomer, mainly used for the production of nylon-6 fiber and nylon-6 engineering plastics, and also used for drug synthesis, which is a widely used and irreplaceable product with broad market demand. The mainstream process for the production of caprolactam is cyclohexanone liquid phase ammonioxydation method. First, cyclohexanone, ammonia and hydrogen peroxide are used to generate cyclohexanone oxime under the action of titanium-silicon molecular sieve. Then, cyclohexanone oxime undergoes Beckmann rearrangement under the action of oleum to generate caprolactam sulfate. Caprolactam sulfate is neutralized with ammonia water to obtain a crude caprolactam aqueous solution. Finally, the crude caprolactam aqueous solution is treated by extraction, back extraction, ion exchange, hydrogenation, evaporation and distillation to obtain refined caprolactam. There are two different solvent systems for the production of cyclohexanone oxime by ammonioxydation method: one is to use tert-butyl alcohol as the solvent for cyclohexanone ammonioxydation reaction, and the other is to use water as the solvent for cyclohexanone ammonioxydation reaction. In order to improve the yield of cyclohexanone oxime, the amount of ammonia in the two reaction systems is excessive. For the homogeneous ammonioxydation system, most of the excess ammonia is recovered by distillation of the reaction solvent tert-butyl alcohol, but the ammonia nitrogen concentration in the oximation wastewater still reaches several hundred to several thousand mg / L. For the heterogeneous ammonioxydation system, there is no tert-butyl alcohol distillation process, so the ammonia nitrogen content in the oximation wastewater is very high, which can be as high as 30,000-40,000 mg / L. In industry, ammonia can be recovered by stripping to reduce the ammonia nitrogen value in the oximation wastewater to about several hundred mg / L, but the stripping method consumes steam and is not the most economical treatment method. If the stripping method is further used to reduce the ammonia nitrogen value to 100 mg / L or even below 10 mg / L, it will consume a lot of energy. At this time, the stripping method has poor ammonia removal rate and high energy consumption, and is not economical.

[0005] With the progress of membrane technology, the application advantages of membrane treatment technology in the field of environment are increasingly apparent, and membrane ammonia removal technology for ammonia-nitrogen wastewater is also a research and application hotspot. The commonly used membrane ammonia removal technologies include vacuum membrane ammonia removal, membrane absorption ammonia removal, and membrane bioreactor ammonia removal. Membrane ammonia removal process has the advantages of no air and steam consumption, and greatly reduced energy consumption and wastewater treatment cost, and the selection of absorption liquid is very important. Some literatures report that dilute acid solution (such as dilute sulfuric acid, dilute hydrochloric acid, dilute phosphoric acid, etc.) can be used as absorption liquid, but the by-product ammonium salt solution with low concentration is produced after absorption and ammonia removal, which is difficult to further treat.

[0006] CN 112875938 A discloses a kind of ammonia-nitrogen wastewater membrane absorption treatment device and method, which is a kind of membrane contactor device for treating ammonia-nitrogen wastewater, and introduces a method for treating ammonia-nitrogen wastewater with acid as absorption liquid. However, the pH value of the absorption liquid is 0.5-1.5, so strong acid is needed to maintain the pH value of the absorption liquid, which requires high corrosion resistance of the absorption liquid pipeline and material, and produces low-value ammonium salt by-products. SUMMARY

[0007] The technical problem solved by the present application is to overcome the above-mentioned defects existing in the prior art, and to provide a device for treating ammonia-nitrogen wastewater with caprolactam sulfate, which has simple structure, large processing capacity, good deamination effect, green environmental protection, safety and reliability, low energy consumption and low cost.

[0008] The further technical problem solved by the present application is to overcome the above-mentioned defects existing in the prior art, and to provide a method for treating ammonia-nitrogen wastewater with caprolactam sulfate, which has large processing capacity, good deamination effect, low requirement for acid corrosion resistance of pipelines and equipment, no additional by-products and three wastes, realizes neutralization of caprolactam sulfate, short residence time, simple process, low cost and suitability for industrial production.

[0009] The technical solution adopted by the present application to solve the technical problem is as follows: a device for treating ammonia-nitrogen wastewater with caprolactam sulfate, comprising a filter, a pH value adjusting tank, a cross-flow membrane contactor assembly, a caprolactam sulfate hydrolysis tank and an absorption liquid circulating tank; the cross-flow membrane contactor assembly is formed by one or more cross-flow membrane contactors in parallel in the vertical direction connected in series; one end of the filter is provided with a filter water inlet, and the other end of the filter is provided with a filter water outlet connected with a water inlet of the pH value adjusting tank; the pH value adjusting tank is provided with a pH adjusting agent feeding port; a water outlet of the pH value adjusting tank is connected with a tube side water inlet of one end of a first cross-flow membrane contactor in the cross-flow membrane contactor assembly, and the other end of the cross-flow membrane contactor is provided with a tube side water outlet; the caprolactam sulfate hydrolysis tank is provided with a water inlet, a caprolactam sulfate feeding port and an absorption liquid outlet; the absorption liquid outlet of the caprolactam sulfate hydrolysis tank is connected with an absorption liquid shell side inlet of the first cross-flow membrane contactor in the cross-flow membrane contactor assembly near the tube side water outlet; an absorption liquid shell side outlet of the last cross-flow membrane contactor in the cross-flow membrane contactor assembly near the tube side water inlet is connected with an inlet of the absorption liquid circulating tank; a circulating outlet of the upper part of the absorption liquid circulating tank is connected with an absorption liquid shell side inlet of the first cross-flow membrane contactor in the cross-flow membrane contactor assembly; and the lower part of the absorption liquid circulating tank is provided with an absorption liquid discharge port.

[0010] The working process of the device is as follows: ammonia-nitrogen wastewater is sent into the filter through the filter inlet, filtered, and then sent into the pH adjusting tank to adjust the pH value by using a pH adjuster; at the same time, the absorption liquid after hydrolysis of caprolactam sulfate and water in the caprolactam sulfate hydrolysis tank is sent into the shell side of the first cross-flow membrane contactor in the cross-flow membrane contactor assembly through the liquid inlet on the side of the tube side outlet; the ammonia-nitrogen in the ammonia-nitrogen wastewater in the tube side of the cross-flow membrane contactor is separated in the form of NH3 and is absorbed by the caprolactam sulfate hydrolysis absorption liquid in the shell side of the cross-flow membrane contactor through the micropores on the membrane wall of the cross-flow membrane, so that the ammonia-nitrogen in the wastewater is efficiently removed; the treated ammonia-nitrogen wastewater is discharged from the tube side outlet of the last cross-flow membrane contactor; the caprolactam sulfate hydrolysis absorption liquid after absorbing the ammonia-nitrogen is discharged from the absorption liquid shell side outlet of the last cross-flow membrane contactor and is sent into the absorption liquid circulating tank; when the pH value of the absorption liquid reaches the standard, the caprolactam sulfate is discharged as neutralized; and when the pH value of the absorption liquid does not reach the standard, the absorption liquid is returned to the absorption liquid shell side inlet of the first cross-flow membrane contactor in the cross-flow membrane contactor assembly for recycling.

[0011] Preferably, the filter has a filtering precision of ≤5 μm. The filter can filter the suspended solids in the wastewater to prevent the membrane holes from being blocked.

[0012] Preferably, when the cross-flow membrane contactor assembly is two or more cross-flow membrane contactors connected in series, the connection mode is that the tube side outlet of a previous cross-flow membrane contactor is connected to the tube side inlet of a next cross-flow membrane contactor, the absorption liquid shell side outlet of the previous cross-flow membrane contactor is connected to the absorption liquid shell side inlet of the next cross-flow membrane contactor, and so on.

[0013] Preferably, the pore size of the cross-flow membrane is ≤0.25 μm.

[0014] Preferably, the cross-flow membrane is one or a combination of hollow fiber membrane, flat sheet membrane, and spiral wound membrane.

[0015] Preferably, the cross-flow membrane is one or a combination of polypropylene membrane, polytetrafluoroethylene membrane, polyvinylidene fluoride membrane, polyethylene membrane, and polyvinyl chloride membrane. More preferably, the cross-flow membrane is polytetrafluoroethylene membrane or polypropylene membrane.

[0016] Preferably, the pH adjusting tank has a heating function.

[0017] Preferably, the caprolactam sulfate hydrolysis tank has a stirring function, a heating function, and a temperature control function.

[0018] Preferably, the filter, the pH adjusting tank, and the absorption liquid circulating tank are all sealed devices, which can prevent ammonia gas from volatilizing.

[0019] The technical scheme adopted by the present application to solve the technical problems is as follows: a method for treating ammonia-nitrogen wastewater by using caprolactam sulfate, comprising the following steps:

[0020] (1) filtering the ammonia-nitrogen wastewater, adding a pH regulator to adjust the pH value, and preheating to obtain ammonia-nitrogen adjusted wastewater;

[0021] (2) adding water to the caprolactam sulfate, stirring to hydrolyze, and preheating to obtain a caprolactam sulfate hydrolysis absorption solution;

[0022] (3) feeding the ammonia-nitrogen adjusted wastewater obtained in step (1) into the tube side of a first-stage cross-flow membrane contactor, and performing cross-flow diffusion absorption with the caprolactam sulfate hydrolysis absorption solution obtained in step (2) fed into the shell side of the cross-flow membrane contactor, after the wastewater flows out of the tube side and enters the tube side of the next-stage cross-flow membrane contactor, and after the absorption solution flows out of the shell side and enters the shell side of the next-stage cross-flow membrane contactor, the treated ammonia-nitrogen wastewater is discharged from the tube side of the last-stage cross-flow membrane contactor, and the absorption solution is discharged from the shell side of the last-stage cross-flow membrane contactor and recycled, and when the pH value of the absorption solution reaches the standard, the neutralized caprolactam sulfate is discharged.

[0023] Preferably, in step (1), the mass concentration of the ammonia-nitrogen wastewater is 200-40,000 mg / L, and the turbidity is 10-600 NTU. The ammonia-nitrogen wastewater used in the present application is wastewater generated in the process of producing cyclohexanone oxime by the ammoximation method.

[0024] Preferably, in step (1), the filtration is performed to a turbidity of ≤20 NTU. By filtering the suspended matter in the wastewater, the membrane holes are prevented from being blocked.

[0025] Preferably, in step (1), the pH value is adjusted to 7.5-13 (more preferably 10-12). At the pH value, the ammonia-nitrogen in the wastewater can be maintained in the form of free ammonia, so as to overflow in the form of gaseous ammonia.

[0026] Preferably, in step (1), the pH regulator is one or more of sodium hydroxide, calcium hydroxide, calcium oxide, and potassium hydroxide.

[0027] Preferably, in step (1), the preheating is performed to a temperature of 15-55°C (more preferably 40-50°C). By preheating, the ammonia can be quickly overflowed, and the ammonia removal efficiency is improved.

[0028] Preferably, in step (2), the mass ratio of caprolactam sulfate to water is 1:0.5-50 (more preferably 1:1-20, and further preferably 1:2-10) on a sulfuric acid basis. The caprolactam sulfate used in the present application is the Beckmann rearrangement product of cyclohexanone oxime in the caprolactam production process. The caprolactam sulfate reacts with water to hydrolyze to form caprolactam and sulfuric acid, and forms an acidic buffer solution with the caprolactam sulfate. By controlling the ratio of water addition, the degree of hydrolysis and the acidity of the buffer solution are controlled, and the surface tension of the absorption solution is regulated.

[0029] Preferably, in step (2), the temperature of the hydrolysis is 0-50°C (more preferably 10-30°C), and the time is 1-60 min (more preferably 10-30 min). If the hydrolysis temperature is too low, the hydrolysis reaction will not proceed well, and if the hydrolysis temperature is too high, poly-caprolactam and other byproducts will be produced. The hydrolysis time is affected by the hydrolysis temperature, the concentration of the reactants, and stirring, and the hydrolysis time needs to ensure that the hydrolysis reaction is completely carried out.

[0030] Preferably, in step (2), the preheating temperature is 15-55°C (more preferably 40-50°C). A higher temperature is conducive to the mass transfer efficiency of the absorption solution, and promotes the absorption of ammonia.

[0031] Preferably, in step (2), the pH value of the caprolactam sulfate hydrolysis absorption solution is 1.5-3.0, and the surface tension is ≥40 mN / m (more preferably 40-65 mN / m). A higher pH value of the caprolactam sulfate hydrolysis absorption solution makes the requirement for acid corrosion resistance of the pipelines and equipment lower, reducing equipment investment and maintenance costs. In the prior art, the pH value of the absorption solution is lower in the method of removing ammonia with an acid solution. Although a higher pH value is not conducive to improving the ammonia removal rate, the neutralization capacity of ammonia by the acid solution is greater because the caprolactam sulfate hydrolysis solution is an acidic buffer system. Limiting the surface tension of the caprolactam sulfate hydrolysis absorption solution is conducive to judging the leakage of the material. If the surface tension is too low, the caprolactam product will leak into the wastewater, causing losses. The tension in the present application is the tension at 25°C.

[0032] Preferably, in step (3), the volume ratio of the ammonia nitrogen adjusted wastewater to the caprolactam sulfate hydrolysis absorption solution is 1:0.01-10 (more preferably 1:0.05-5.00, and further preferably 1:0.1-2.0). Limiting the volume ratio can control the ammonia removal rate of the wastewater and the neutralization degree of the caprolactam sulfate.

[0033] Preferably, in step (3), the ratio of the flow rate of the ammonia nitrogen adjusted wastewater in the tube to the flow rate of the caprolactam sulfate hydrolysis absorption solution in the shell is 1:1-100 (more preferably 1:1-50, and further preferably 1:2-20).

[0034] Preferably, in step (3), the flow rate of the ammonia-nitrogen-adjusted wastewater in the pipe is related to the single-stage cross-flow membrane area, and the flow rate of the wastewater per unit membrane area is 2-20 L / (m 2 ·h) (more preferably 5-15 L / (m 2 ·h).

[0035] Preferably, in step (3), the residence time of the cross-flow diffusion of the single cross-flow membrane contactor is 1.0-2.6 min (more preferably 1.2-2.0 min).

[0036] Preferably, in step (3), the pH value of the absorbent solution meets the standard of 2.5-12.0 (more preferably 3-7). The selection of the pH value will affect the ammonia removal rate of the wastewater and the neutralization degree of the caprolactam sulfate, and the content of caprolactam will be different with different neutralization degrees.

[0037] The beneficial effects of the present application are as follows:

[0038] (1) The device for treating ammonia-nitrogen wastewater with caprolactam sulfate according to the present application has a simple structure, a large treatment capacity, a good ammonia removal effect, and is green, environmentally friendly, safe and reliable, low in energy consumption and cost;

[0039] (2) The method according to the present application has a large treatment capacity, and the ammonia-nitrogen content in the effluent after ammonia removal meets the ammonia-nitrogen concentration requirement of the subsequent biochemical treatment section, which can be as low as 100 mg / L or less, in line with the “Integrated Wastewater Discharge Standard” GB8978-1996, and the ammonia removal rate is as high as 99.58%;

[0040] (3) The method according to the present application uses the weakly acidic material prepared from the hydrolysate of caprolactam sulfate in caprolactam production enterprises as the absorbent solution, which has a weak acidity and low requirement for acid corrosion resistance of pipelines and equipment. Part of the sulfuric acid is neutralized with ammonia in the wastewater to generate ammonium sulfate, which can reduce the consumption of raw ammonia in the subsequent ammonia neutralization process. Compared with membrane ammonia removal using acid solution as the absorbent, no additional ammonium salt byproduct and three wastes are generated, and the neutralization of caprolactam sulfate is realized at a short residence time.

[0041] (4) Compared with the wastewater ammonia removal processes such as distillation or stripping, the membrane ammonia removal does not require steam consumption, and the process is simple and low in cost, which is suitable for industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 is a schematic diagram of the device for treating ammonia-nitrogen wastewater with caprolactam sulfate according to Example 1 of the present application;

[0043] Figure 2 is a schematic diagram of the longitudinal section of the cross-flow membrane contactor. Figure 1 DETAILED DESCRIPTION​

[0044] The application will be further described in connection with the examples and the accompanying drawings.

[0045] The ammonia-nitrogen wastewater used in the examples and the comparative examples is the wastewater generated in the oximation process for producing cyclohexanone oxime in a certain factory. The initial ammonia-nitrogen value of the ammonia-nitrogen wastewater 1 is 21865 mg / L, and the turbidity is 68 NTU. The initial ammonia-nitrogen value of the ammonia-nitrogen wastewater 2 is 16425 mg / L, and the turbidity is 42 NTU. The caprolactam sulfate used in the examples of the application is the Beckmann rearrangement product of cyclohexanone oxime in the caprolactam production process, and the mass content of sulfuric acid is 50%.

[0046] The raw materials or chemical reagents used in the examples of the application are obtained through conventional commercial channels unless otherwise specified.

[0047] The effluent ammonia-nitrogen value in the examples and the comparative examples is detected by the Nessler's reagent spectrophotometry.

[0048] A device for treating ammonia-nitrogen wastewater with caprolactam sulfate

[0049] As Figure 1 , 2The device for treating ammonia-nitrogen wastewater by caprolactam sulfate includes a filter 1, a pH value adjusting tank 2, a cross-flow membrane contactor assembly 3, a caprolactam sulfate hydrolysis tank 4 and an absorption liquid circulating tank 5. The cross-flow membrane contactor assembly 3 is formed by two cross-flow membrane contactors 3-1 in parallel in the vertical direction. One end of the filter 1 is provided with a filter water inlet 1-1, and the other end is provided with a filter water outlet 1-2 connected with a water inlet 2-1 of the pH value adjusting tank 2. The pH value adjusting tank 2 is provided with a pH regulator feeding port 2-2. A water outlet 2-3 of the pH value adjusting tank 2 is connected with a pipe passage 3-1-6 water inlet 3-1-1 of one end of a first cross-flow membrane contactor 3-1 in the cross-flow membrane contactor assembly 3. The other end of the cross-flow membrane contactor 3-1 is provided with a pipe passage 3-1-6 water outlet 3-1-2. The caprolactam sulfate hydrolysis tank 4 is provided with a water inlet 4-1, a caprolactam sulfate feeding port 4-2 and an absorption liquid outlet 4-3. The absorption liquid outlet 4-3 of the caprolactam sulfate hydrolysis tank 4 is connected with an absorption liquid shell passage 3-1-7 liquid inlet 3-1-3 of the first cross-flow membrane contactor 3-1 in the cross-flow membrane contactor assembly 3 near the pipe passage 3-1-6 water outlet 3-1-2 side. An absorption liquid shell passage 3-1-7 liquid outlet 3-1-4 of the second cross-flow membrane contactor 3-1 in the cross-flow membrane contactor assembly 3 near the pipe passage 3-1-6 water inlet 3-1-1 side is connected with a liquid inlet 5-1 of the absorption liquid circulating tank 5. A circulating liquid outlet 5-2 of the upper part of the absorption liquid circulating tank 5 is connected with the absorption liquid shell passage 3-1-7 liquid inlet 3-1-3 of the first cross-flow membrane contactor 3-1 in the cross-flow membrane contactor assembly 3. The lower part of the absorption liquid circulating tank 5 is provided with an absorption liquid discharge port 5-3.

[0050] The filter 1 has a filtering precision of 5 μm. When the cross-flow membrane contactor assembly 3 is formed by two cross-flow membrane contactors 3-1 connected in series, the first cross-flow membrane contactor 3-1 is connected with the second cross-flow membrane contactor 3-1 through the pipe passage 3-1-6 water outlet 3-1-2 and the pipe passage 3-1-6 water inlet 3-1-1, and the absorption liquid shell passage 3-1-7 liquid outlet 3-1-4 and the absorption liquid shell passage 3-1-7 liquid inlet 3-1-3. The cross-flow membrane 3-1-5 is a polytetrafluoroethylene membrane with a pore size of 0.05 μm and a hollow fiber membrane combination mode. The pH value adjusting tank 2 has a heating function. The caprolactam sulfate hydrolysis tank 4 has a stirring function, a heating function and a temperature control function. The filter 1, the pH value adjusting tank 2 and the absorption liquid circulating tank 5 are all sealed devices.

[0051] The working process of the device is as follows: the ammonia-nitrogen wastewater is sent into the filter 1 through the filter inlet 1-1, filtered, and then sent into the pH value adjusting tank 2 to adjust the pH value by using a pH adjusting agent; at the same time, the absorption liquid after the hydrolysis of caprolactam sulfate and water in the caprolactam sulfate hydrolysis tank 4 is sent into the shell side 3-1-7 of the first cross-flow membrane contactor 3-1 in the cross-flow membrane contactor assembly 3 through the liquid inlet 3-1-3 of the absorption liquid shell side 3-1-7 close to the tube side 3-1-6; the ammonia-nitrogen in the ammonia-nitrogen wastewater in the tube side 3-1-6 of the cross-flow membrane contactor 3-1 is separated in the form of NH3 and is absorbed by the caprolactam sulfate hydrolysis absorption liquid in the shell side 3-1-7 of the cross-flow membrane contactor 3-1 through the micropores on the membrane wall of the cross-flow membrane 3-1-5, so that the ammonia-nitrogen in the wastewater is efficiently removed; the treated ammonia-nitrogen wastewater is discharged from the tube side 3-1-6 outlet 3-1-2 of the second cross-flow membrane contactor 3-1; the caprolactam sulfate hydrolysis absorption liquid after absorbing the ammonia-nitrogen is discharged from the absorption liquid shell side 3-1-7 outlet 3-1-4 of the second cross-flow membrane contactor 3-1 and is sent into the absorption liquid circulating tank 5; when the pH value of the absorption liquid reaches the standard, the caprolactam sulfate is discharged as neutralized; when the pH value of the absorption liquid does not reach the standard, the absorption liquid is returned to the liquid inlet 3-1-3 of the absorption liquid shell side 3-1-7 of the first cross-flow membrane contactor 3-1 in the cross-flow membrane contactor assembly 3 for recycling.

[0052] A device for treating ammonia-nitrogen wastewater by using caprolactam sulfate

[0053] The difference between the embodiment and the embodiment 1 is that the cross-flow membrane contactor assembly 3 is composed of one cross-flow membrane contactor 3-1.

[0054] A device for treating ammonia-nitrogen wastewater by using caprolactam sulfate

[0055] The difference between the embodiment and the embodiment 1 is that the cross-flow membrane contactor assembly 3 is composed of three cross-flow membrane contactors 3-1 in parallel in the vertical direction; when the cross-flow membrane contactor assembly 3 is composed of three cross-flow membrane contactors 3-1 in series, the connection mode is that the tube side 3-1-6 outlet 3-1-2 of the first cross-flow membrane contactor 3-1 is connected with the tube side 3-1-6 inlet 3-1-1 of the second cross-flow membrane contactor 3-1, the absorption liquid shell side 3-1-7 outlet 3-1-4 of the first cross-flow membrane contactor 3-1 is connected with the absorption liquid shell side 3-1-7 inlet 3-1-3 of the second cross-flow membrane contactor 3-1, and so on.

[0056] A device for treating ammonia-nitrogen wastewater by using caprolactam sulfate

[0057] The same as Example 2.

[0058] A method for treating ammonia-nitrogen wastewater with caprolactam sulfate

[0059] (1) 5 L of ammonia-nitrogen wastewater 1 was filtered to a turbidity of 5 NTU, sodium hydroxide was added to adjust the pH value to 11.5, and then preheated to 40°C to obtain 5 L of ammonia-nitrogen adjusted wastewater;

[0060] (2) 2400 g of water was added to 1200 g of caprolactam sulfate, and after stirring for hydrolysis at 25°C for 20 min, it was preheated to 40°C to obtain 3 L of caprolactam sulfate hydrolysis absorption liquid (pH value 1.9, surface tension 52 mN / m);

[0061] (3) 5 L of ammonia-nitrogen adjusted wastewater obtained in step (1) was sent into the tube side of the first-stage cross-flow membrane contactor at a flow rate of 10 L / h, and the flow rate of wastewater per unit membrane area was 10 L / (m 2 h), and was subjected to cross-flow diffusion absorption with 3 L of caprolactam sulfate hydrolysis absorption liquid obtained in step (2) sent into the shell side of the cross-flow membrane contactor at a flow rate of 100 L / h, after the wastewater flowed out from the tube side into the tube side of the second-stage cross-flow membrane contactor, and the absorption liquid flowed out from the shell side into the shell side of the second-stage cross-flow membrane contactor, the ammonia-nitrogen wastewater was discharged from the tube side of the second stage, the residence time of cross-flow diffusion of a single cross-flow membrane contactor was 1.5 min, and the absorption liquid was discharged from the shell side of the second stage and returned for recycling, and when the pH value of the absorption liquid reached 3.5, the neutralized caprolactam sulfate was discharged.

[0062] After detection, the ammonia-nitrogen value of the effluent of each stage was: the ammonia-nitrogen value of the first stage was 1756 mg / L, and the ammonia-nitrogen removal rate was 91.97%; the ammonia-nitrogen value of the second stage was 98 mg / L, and the ammonia-nitrogen removal rate was 99.55%.

[0063] Comparative Example 1

[0064] The difference between this comparative example and Example 1 is only that in step (3), the caprolactam sulfate hydrolysis absorption liquid obtained in step (2) was sent into the shell side of the cross-flow membrane contactor at a flow rate of 8 L / h.

[0065] After detection, the ammonia-nitrogen value of the effluent of each stage was: the ammonia-nitrogen value of the first stage was 6784 mg / L, and the ammonia-nitrogen removal rate was 68.97%; the ammonia-nitrogen value of the second stage was 2118 mg / L, and the ammonia-nitrogen removal rate was 90.31%.

[0066] Comparing Example 1 with Comparative Example 1 shows that as the flow rate of the caprolactam sulfate hydrolysis absorption liquid decreases, the mass transfer effect of the absorption liquid is weakened, and the ammonia-nitrogen removal rate decreases accordingly.

[0067] A method for treating ammonia-nitrogen wastewater with caprolactam sulfate

[0068] (1) 50 L of ammonia-nitrogen wastewater 1 was filtered to a turbidity of 5 NTU, sodium hydroxide was added to adjust the pH value to 12, and then preheated to 50°C to obtain 50 L of ammonia-nitrogen adjusted wastewater;

[0069] (2) 24000 g of water was added to 12000 g of caprolactam sulfate, and hydrolysis was carried out at 20°C for 25 min under stirring, and then preheated to 50°C to obtain 30 L of caprolactam sulfate hydrolysis absorption liquid (pH value 1.9, surface tension 52 mN / m);

[0070] (3) 50 L of ammonia-nitrogen adjusted wastewater obtained in step (1) was sent into the tube side of the cross-flow membrane contactor at a flow rate of 100 L / h, and the flow rate of wastewater per unit membrane area was 13 L / (m 2 ·h), and was subjected to cross-flow diffusion absorption with 30 L of caprolactam sulfate hydrolysis absorption liquid obtained in step (2) sent into the shell side of the cross-flow membrane contactor at a flow rate of 1000 L / h, the ammonia-nitrogen wastewater was discharged from the tube side, the residence time was 1.2 min, the absorption liquid was discharged from the shell side and returned for recycling, and when the pH value of the absorption liquid reached 3.1, the neutralized caprolactam sulfate was discharged.

[0071] It was detected that the ammonia-nitrogen value of the effluent from the tube side was 1248 mg / L, and the ammonia-nitrogen removal rate was 94.29%.

[0072] Comparative Example 2

[0073] The difference between this comparative example and Example 2 is that step (2) is replaced by: 34800 g of water was added to 1200 g of caprolactam sulfate, and hydrolysis was carried out at 20°C for 20 min under stirring, and then preheated to 50°C to obtain 35.4 L of caprolactam sulfate hydrolysis absorption liquid (pH value 3.9, surface tension 67 mN / m); in step (3), when the pH value of the absorption liquid reached 7.5, the neutralized caprolactam sulfate was discharged.

[0074] It was detected that the ammonia-nitrogen value of the effluent from the tube side was 11730 mg / L, and the ammonia-nitrogen removal rate was 46.35%.

[0075] Comparing Example 2 with Comparative Example 2 shows that the ammonia removal effect is greatly reduced after reducing the ratio of caprolactam sulfate to water.

[0076] Comparing Example 2 with Example 1 shows that even if the residence time is shortened, the ammonia removal effect is better when the pH value of the wastewater is increased and the preheating temperature of the absorption liquid and the wastewater is increased.

[0077] A method for treating ammonia-nitrogen wastewater with caprolactam sulfate

[0078] (1) 50 L of ammonia-nitrogen wastewater 1 was filtered to a turbidity of 5 NTU, sodium hydroxide was added to adjust the pH value to 11.5, and then preheated to 45°C to obtain 50 L of ammonia-nitrogen adjusted wastewater;

[0079] (2) 12000 g of water was added to 6000 g of caprolactam sulfate, and after stirring for hydrolysis at 25°C for 20 min, it was preheated to 45°C to obtain 15 L of caprolactam sulfate hydrolysis absorption liquid (pH value 1.9, surface tension 52 mN / m);

[0080] (3) 50 L of ammonia-nitrogen adjusted wastewater obtained in step (1) was sent into the tube side of the first stage cross-flow membrane contactor at a flow rate of 100 L / h, and the flow rate of wastewater per unit membrane area was 10 L / (m 2 ·h), and was subjected to cross-flow diffusion absorption with 15 L of caprolactam sulfate hydrolysis absorption liquid obtained in step (2) sent into the shell side of the first stage cross-flow membrane contactor at a flow rate of 800 L / h, after the wastewater flowed out from the tube side, it entered the tube side of the second stage cross-flow membrane contactor, and after the absorption liquid flowed out from the shell side, it entered the shell side of the second stage cross-flow membrane contactor, and so on, the ammonia-nitrogen wastewater treated was discharged from the tube side of the third stage, the residence time of cross-flow diffusion of a single cross-flow membrane contactor was 1.5 min, and the absorption liquid was discharged from the shell side of the third stage and returned for recycling, and when the pH value of the absorption liquid reached 5.8, the neutralized caprolactam sulfate was discharged.

[0081] It was detected that the ammonia-nitrogen value of the effluent of each stage was: the ammonia-nitrogen value of the first stage was 3511 mg / L, and the ammonia-nitrogen removal rate was 83.94%; the ammonia-nitrogen value of the second stage was 564 mg / L, and the ammonia-nitrogen removal rate was 97.42%; and the ammonia-nitrogen value of the third stage was 92 mg / L, and the ammonia-nitrogen removal rate was 99.58%.

[0082] Comparative Example 3

[0083] The difference between this comparative example and Example 3 was only that in step (3), the flow rate of wastewater per unit membrane area was 21 L / (m 2 ·h), and the residence time of cross-flow diffusion of a single cross-flow membrane contactor was 0.71 min.

[0084] It was detected that the ammonia-nitrogen value of the effluent of each stage was: the ammonia-nitrogen value of the first stage was 9384 mg / L, and the ammonia-nitrogen removal rate was 57.08%; the ammonia-nitrogen value of the second stage was 4100 mg / L, and the ammonia-nitrogen removal rate was 81.25%; and the ammonia-nitrogen value of the third stage was 1828 mg / L, and the ammonia-nitrogen removal rate was 91.64%.

[0085] Comparing Example 3 with Comparative Example 3, it can be seen that when the flow rate of wastewater per unit membrane area is increased, the residence time of wastewater in the cross-flow diffusion of the single cross-flow membrane contactor is correspondingly shortened, and the ammonia nitrogen removal rate is significantly reduced.

[0086] A method for treating ammonia nitrogen wastewater with caprolactam sulfate

[0087] (1) 50 L of ammonia nitrogen wastewater 2 was filtered to a turbidity of 5 NTU, sodium hydroxide was added to adjust the pH value to 11.8, and then preheated to 43°C to obtain 50 L of ammonia nitrogen adjusted wastewater;

[0088] (2) 30,000 g of water was added to 10,000 g of caprolactam sulfate, and hydrolysis was carried out at 15°C for 15 min under stirring, and then preheated to 43°C to obtain 35 L of caprolactam sulfate hydrolysis absorption liquid (pH value 2.6, surface tension 64 mN / m);

[0089] (3) 50 L of ammonia nitrogen adjusted wastewater obtained in step (1) was sent into the tube side of the cross-flow membrane contactor at a flow rate of 100 L / h, and the flow rate of wastewater per unit membrane area was 10 L / (m 2 ·h), and was subjected to cross-flow diffusion absorption with 35 L of caprolactam sulfate hydrolysis absorption liquid obtained in step (2) sent into the shell side of the cross-flow membrane contactor at a flow rate of 1000 L / h, the treated ammonia nitrogen wastewater was discharged from the tube side, the residence time was 1.5 min, the absorption liquid was discharged from the shell side and returned for recycling, and when the pH value of the absorption liquid reached 3.6, the neutralized caprolactam sulfate was discharged.

[0090] After detection, the ammonia nitrogen value of the effluent in the tube side was 1698 mg / L, and the ammonia nitrogen removal rate was 89.66%.

[0091] Comparative Example 4

[0092] The difference between this comparative example and Example 4 is only that step (2) is deleted, and the absorption liquid used in step (3) is replaced with a sulfuric acid solution, and the pH value of the sulfuric acid solution is 2.6 and the surface tension is 72 mN / m. After the operation is completed, the final pH value of the absorption liquid is 11.1.

[0093] After detection, the ammonia nitrogen value of the effluent in the tube side was 11307 mg / L, and the ammonia nitrogen removal rate was 31.16%.

[0094] Comparing Example 4 with Comparative Example 4, it can be seen that under the same pH value of the absorption liquid, compared with the conventional sulfuric acid solution, the caprolactam sulfate hydrolysis liquid used in the method has stronger pH value buffering capacity and higher ammonia removal rate.

Claims

1. A method for treating ammonia nitrogen wastewater with caprolactam sulfate, characterized in that: The steps include: (1) Filtering the ammonia nitrogen wastewater, adding a pH regulator to adjust the pH value, and preheating to obtain ammonia nitrogen adjusted wastewater; (2) adding water to caprolactam sulfate, stirring for hydrolysis, and preheating to obtain a caprolactam sulfate hydrolysis absorption liquid; the mass ratio of the caprolactam sulfate to water is 1:0.5-50, calculated as sulfuric acid; the preheating is performed to 15-55° C.; the pH value of the caprolactam sulfate hydrolysis absorption liquid is 1.5-3.0, and the surface tension is ≥40 mN / m; (3) The ammonia nitrogen regulated wastewater obtained in step (1) is fed into the tube side of the first-stage cross-flow membrane contactor and is subjected to cross-flow diffusion absorption together with the caprolactam sulfate hydrolysis absorption liquid obtained in step (2) fed into the shell side of the cross-flow membrane contactor. The wastewater flows out of the tube side and enters the tube side of the next-stage cross-flow membrane contactor. The absorption liquid flows out of the shell side and enters the shell side of the next-stage cross-flow membrane contactor. The treated ammonia nitrogen wastewater is discharged from the tube side of the last stage, and the absorption liquid is discharged from the shell side of the last stage and The wastewater is returned for recycling and discharged as neutralized caprolactam sulfate when the pH value of the absorption liquid reaches the standard; the volume ratio of the ammonia nitrogen adjustment wastewater to the caprolactam sulfate hydrolysis absorption liquid is 1:0.01-10; the flow rate ratio of the ammonia nitrogen adjustment wastewater in the tube side to the caprolactam sulfate hydrolysis absorption liquid in the shell side is 1:1-100; the flow rate of the ammonia nitrogen adjustment wastewater in the tube side is related to the area of ​​the single-stage cross-flow membrane, and the flow rate of the wastewater per unit membrane area is 2-20L / (m 2 ·h); the residence time of cross-flow diffusion in a single cross-flow membrane contactor is 1.0 to 2.6 min; the pH value of the absorption liquid that meets the standard is 2.5 to 12.

0.

2. The method for treating ammonia nitrogen wastewater with caprolactam sulfate according to claim 1, wherein: In step (1), the mass concentration of the ammonia nitrogen wastewater is 200-40000 mg / L, and the turbidity is 10-600 NTU; the filtration is performed to a turbidity of ≤20 NTU; the pH value is adjusted to 7.5-13; the pH regulator is one or more of sodium hydroxide, calcium hydroxide, calcium oxide or potassium hydroxide; and the preheating is performed to 15-55°C.

3. The method for treating ammonia nitrogen wastewater with caprolactam sulfate according to claim 1 or 2, characterized in that: In step (2), the hydrolysis temperature is 0 to 50° C., and the time is 1 to 60 minutes.

4. A device for treating ammonia nitrogen wastewater with caprolactam sulfate using the method according to any one of claims 1 to 3, characterized in that: The invention comprises a filter, a pH regulating tank, a cross-flow membrane contactor assembly, a caprolactam sulfate hydrolysis tank and an absorption liquid circulation tank; the cross-flow membrane contactor assembly is composed of a plurality of cross-flow membrane contactors connected in series in parallel in the vertical direction; one end of the filter is provided with a filter water inlet, and the filter water outlet at the other end is connected to the water inlet of the pH regulating tank; the pH regulating tank is provided with a pH regulator feed port; the water outlet of the pH regulating tank is connected to the tube side water inlet at one end of the first cross-flow membrane contactor in the cross-flow membrane contactor assembly, and the other end of the cross-flow membrane contactor is provided with a tube side water outlet; the caprolactam sulfate hydrolysis tank A water inlet, a caprolactam sulfate feed inlet and an absorption liquid outlet are provided on it; the absorption liquid outlet of the caprolactam sulfate hydrolysis tank is connected to the absorption liquid shell-side inlet on the near-tube-side water outlet side of the first cross-flow membrane contactor in the cross-flow membrane contactor assembly; the absorption liquid shell-side outlet on the near-tube-side water inlet side of the last cross-flow membrane contactor in the cross-flow membrane contactor assembly is connected to the inlet on the absorption liquid circulation tank; the circulation outlet on the upper part of the absorption liquid circulation tank is connected to the absorption liquid shell-side inlet of the first cross-flow membrane contactor in the cross-flow membrane contactor assembly; and an absorption liquid discharge port is provided at the lower part of the absorption liquid circulation tank.

5. The device for treating ammonia nitrogen wastewater with caprolactam sulfate according to claim 4, characterized in that: The filtration accuracy of the filter is ≤5μm; the connection method of the cross-flow membrane contactor assembly is: the tube-side water outlet of the previous cross-flow membrane contactor is connected to the tube-side water inlet of the next cross-flow membrane contactor, the absorption liquid shell-side liquid outlet of the previous cross-flow membrane contactor is connected to the absorption liquid shell-side liquid inlet of the next cross-flow membrane contactor, and so on; the pore size of the cross-flow membrane is ≤0.25μm; the cross-flow membrane is a combination of one or more of a hollow fiber membrane, a flat membrane or a roll membrane; the cross-flow membrane is a combination of one or more of a polypropylene membrane, a polytetrafluoroethylene membrane, a polyvinylidene fluoride membrane, a polyethylene membrane and a polyvinyl chloride membrane; the pH value adjusting tank has a heating function; the caprolactam sulfate hydrolysis tank has stirring function, heating function and temperature control function; the filter, pH value adjusting tank and absorption liquid circulation tank are all sealed.

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