Benzene-containing wastewater treatment device

Abstract

The invention discloses a benzene-containing wastewater treatment device which comprises an adjusting tank, a stripping tower, a concentrator, a wet oxidation reactor, a heat exchanger, a decompression separation tank, a neutralization tank and a biological treatment system which are connected in sequence, compared with the prior art, the device is mainly composed of an adjusting tank, a stripping tower, a concentrator, a wet oxidation reactor, a heat exchanger, a decompression separation tank, a neutralization tank and a biological treatment system, and for high-concentration benzene-containing wastewater with the benzene content larger than 1000 mg / L, benzene is removed in a combined mode of gas stripping concentration, wet oxidation and biological treatment. The benzene content in the treated wastewater can be reduced to be less than 0.1 mg / L; and meanwhile, the heat exchanger also recovers waste heat in the benzene-containing wastewater treated by the wet oxidation reactor, so that the loss of heat is reduced.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and specifically to a benzene-containing wastewater treatment device. Background Technology

[0002] Benzene has a wide range of uses in industrial production as a chemical raw material and solvent, but it is also a toxic substance. Inhalation and ingestion of benzene, and long-term exposure, can cause bone marrow and genetic damage. Blood tests may reveal leukopenia, thrombocytopenia, pancytopenia, aplastic anemia, and even leukemia. Inhaling large amounts of benzene in a short period can cause acute benzene poisoning, resulting in symptoms such as excitement or intoxication, accompanied by mucosal irritation. Therefore, national regulations on benzene content in water bodies are becoming increasingly stringent.

[0003] There are various methods for treating industrial wastewater containing benzene. For example, CN 115340201A discloses a device for treating and recovering benzene-containing wastewater, which includes a raw water tank, a hydrocyclone oil separator, a self-cleaning filter, parallel A / B adsorption columns, a condenser, an oil-water separator, and a solvent recovery tank connected in sequence along the flow direction of the wastewater.

[0004] In practical applications, the above-mentioned device has shown that it has a better treatment effect on low-to-medium concentration benzene wastewater containing oil and suspended solids (benzene content ≤300mg / L), but when the benzene content in the wastewater reaches more than 1000mg / L, its treatment effect is very poor, with a benzene removal rate of only about 40%. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a benzene-containing wastewater treatment device to solve the problem that the removal rate of benzene is low when the benzene content in the benzene-containing wastewater reaches more than 1000 mg / L.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a benzene-containing wastewater treatment device, comprising an equalization tank, a stripping tower, a concentrator, a wet oxidation reactor, a heat exchanger, a vacuum separation tank, a neutralization tank, and a biological treatment system connected in sequence.

[0007] Compared with the prior art, the present invention has the following beneficial effects:

[0008] This benzene-containing wastewater treatment device mainly consists of an equalization tank, a stripping tower, a thickener, a wet oxidation reactor, a heat exchanger, a pressure reducing tank, a neutralization tank, and a biological treatment system. For high-concentration benzene-containing wastewater with a benzene content greater than 1000 mg / L, a combination of air stripping concentration, wet oxidation, and biological treatment is used to remove benzene, which can reduce the benzene content in the treated wastewater to less than 0.1 mg / L. At the same time, the heat exchanger also recovers the waste heat from the benzene-containing wastewater after treatment by the wet oxidation reactor, reducing heat loss.

[0009] Furthermore, it also includes an exhaust gas treatment system connected to the exhaust port at the top of the stripping tower, the exhaust gas treatment system including a first condenser connected to the exhaust port at the top of the stripping tower and an activated carbon adsorber connected to the first condenser.

[0010] The gas phase separated from the top of the stripping tower is condensed by the first condenser. The liquid phase separated by the first condenser is collected. The gas phase enters the activated carbon adsorber for adsorption treatment. After testing and meeting the atmospheric emission standards, it can be directly discharged into the atmosphere.

[0011] Furthermore, the biological treatment system includes an anaerobic tank connected to the neutralization tank and an aerobic tank connected to the anaerobic tank.

[0012] Furthermore, the catalyst used in the wet oxidation reactor is an eggshell-shaped CuO / SiO2 catalyst. The eggshell structure ensures that the active component CuO is mainly distributed on the outer surface of the SiO2 support, which improves the utilization rate of active sites and reduces the clogging of internal channels. At the same time, during continuous operation, the eggshell-shaped CuO / SiO2 catalyst exhibits good resistance to dissolution and sintering, ensuring long-term stable catalytic performance.

[0013] Furthermore, the preparation method of the CuO / SiO2 catalyst is as follows:

[0014] Step S1, carrier pretreatment: Mesoporous SiO2 is modified with APTES and ultrasonically dispersed in 0.1M EDTA solution;

[0015] Step S2, Precipitation reaction: In a microfluidic reactor, Cu(NO3)2, (NH4)2CO3 solution and SiO2 dispersion prepared in step S1 are mixed and reacted at a flow rate ratio of 1:1:1 at a temperature of 80-90℃.

[0016] Step S3, Washing and Purification: The product prepared in step S2 is first washed by electrodialysis, and then rinsed with 0.1 mM EDTA solution;

[0017] Step S4, calcination and shaping: The mesoporous SiO2 precursor loaded with Cu(OH)2 prepared in step S3 is calcined and shaped using microwave.

[0018] Specifically, the APTES-modified SiO2 support introduces amino-enhanced Cu. 2+ Anchoring points are used to preferentially deposit Cu(OH)2 on the SiO2 surface, forming a uniform eggshell layer and avoiding the waste of active sites caused by bulk loading; this can increase CuO utilization by more than 50%. Step S2 is microfluidic co-precipitation to achieve uniform loading of nanoscale Cu(OH)2, with a specific surface area >150 m⁻² / g, porosity retention >90%, and significantly improved mass transfer efficiency. Step S3 uses a combination of electrodialysis washing and EDTA rinsing to thoroughly remove free Cu. 2+ (Residual content <0.02wt%), to avoid CuO particle agglomeration during calcination; EDTA complexes trace metal impurities (such as Fe3+). + This reduces the risk of catalyst poisoning.

[0019] Furthermore, step S4 specifically includes:

[0020] Step S41, Precursor pretreatment: Place the mesoporous SiO2 precursor in the microwave reaction chamber, introduce inert gas N2 at a flow rate of 50–200 mL / min, and continue purging for 5–10 minutes to remove air.

[0021] Step S42, Microwave heating stage: Under N2 atmosphere, the mesoporous SiO2 precursor is heated to 400±5℃ at a heating rate of 50–100℃ / min, while maintaining a constant N2 flow rate during the heating process.

[0022] Step S43, Constant temperature calcination stage: Hold at 400±5℃ for 10±1 minutes;

[0023] Step S44, Atmosphere switching stage: After the heat preservation is completed, switch the reaction atmosphere to air, with an air flow rate of 100–300 mL / min, and maintain for 5–10 minutes;

[0024] Step S45, Cooling and Collection: Turn off the microwave power and allow it to cool naturally to room temperature in an air environment.

[0025] This microwave calcination process achieves synergistic optimization of catalyst activity, stability, and structure through precise control of "inert protection - rapid heating - atmosphere switching." Specifically, in step S41, N2 purging is used to remove air, preventing Cu(OH)2 from being oxidized to Cu2O impurities at low temperatures (<250℃). In step S42, microwave rapid heating is used, selectively heating polar molecules (Cu(OH)2 and H2O) to achieve uniform heating of the bulk phase, avoiding the "external scorching and internal growth" phenomenon of traditional heating; it also inhibits CuO particle migration and agglomeration, controlling particle size to achieve a specific surface area of ​​150–180 m– / g, which is beneficial for improving benzene adsorption capacity. In step S43, isothermal crystal stability ensures complete decomposition of Cu(OH)2 into CuO; it promotes the formation of Si–O–Cu bonds between CuO and the SiO2 support, enhancing anchoring strength; this improves the mechanical strength of the catalyst, preventing the shedding of active components under wet oxidation high-pressure environment. In step S44, the atmosphere is switched to air, and the surface Cu… 2+ Partial deoxygenation creates oxygen vacancies; these vacancies act as active sites, promoting O2 activation to generate ·OH radicals, thereby increasing the benzene degradation rate. In step S45, natural cooling and slow temperature reduction avoid thermal stress, prevent the eggshell structure from cracking, and preserve the high-temperature oxygen vacancy structure, which helps improve the activity retention rate of the catalyst after multiple uses.

[0026] Furthermore, a mixing tank is provided between the anaerobic and aerobic tanks. In the mixing tank, 190-210 mg of glycerol, 140-160 mg of sodium nitrate, and 12-18 mg of humic acid are added per liter of wastewater. The glycerol, as an easily degradable carbon source, is rapidly utilized by aerobic bacteria, stimulating them to secrete phenyl dioxygenase, accelerating the opening of the benzene ring; simultaneously, it compensates for the insufficient carbon source in the effluent from the anaerobic tank. The sodium nitrate contains NO3... - As an electron acceptor, it drives denitrification in aerobic environments, increasing nitrogen removal rates; NO3 - H is consumed during the reduction process + This buffers pH fluctuations and prevents the accumulation of acidic intermediates (such as phenol). The quinone group (-C=O) of the humic acid is reversibly redox-promoting, leading to the chain degradation of benzene → phenol → catechol; it also complexes toxic intermediates (such as quinones and aldehydes), reducing their inhibitory effect on microorganisms; and simultaneously binds Cu in the wastewater. 2+ Fe 3+ It contains metal ions to prevent them from harming microorganisms. Meanwhile, glycerol, sodium nitrate, and humic acid all have a synergistic effect on benzene removal rate, denitrification efficiency, and sludge settling properties.

[0027] Furthermore, the gas-liquid volume ratio in the stripping tower is 290-300:1.

[0028] Furthermore, the flash vapor phase of the vacuum separator is condensed by the second condenser and then returned to the stripping tower.

[0029] Furthermore, 40-50 mg of glycerol is added per liter of wastewater to the equalization tank. Adding glycerol to the equalization tank homogenizes the water quality and initiates the benzene-degrading bacteria in advance. Attached Figure Description

[0030] Figure 1 This is a process flow diagram of a benzene-containing wastewater treatment device according to the present invention. Detailed Implementation

[0031] The present invention will be further described in detail below through specific embodiments:

[0032] Example 1

[0033] like Figure 1 As shown, a benzene-containing wastewater treatment device includes an equalization tank, a stripping tower, a concentrator, a wet oxidation reactor, a heat exchanger, a vacuum separation tank, a neutralization tank, an anaerobic tank, a mixing tank, and an aerobic tank connected in sequence. The top of the stripping tower is connected to a first condenser and an activated carbon adsorber in sequence. The flash vapor phase of the vacuum separation tank is condensed by a second condenser and then returned to the stripping tower.

[0034] Benzene-containing wastewater (benzene concentration 1200 mg / L) sequentially passes through an equalization tank, stripping tower, concentrator, wet oxidation reactor, heat exchanger, vacuum separation tank, neutralization tank, anaerobic tank, mixing tank, and aerobic tank. In the equalization tank, 40 mg of glycerol is added per liter of benzene-containing wastewater, and the pH is adjusted to 7.5. In the stripping tower, the temperature is controlled at 80-100℃, the pressure at -0.05 to -0.02 MPa, and the gas-liquid ratio is 290:1 (volume ratio). The wet oxidation reactor incorporates an eggshell-type CuO / SiO2 catalyst, and the reaction conditions are a temperature of 250℃ and a pressure of 12 MPa. The anaerobic tank has a heat transfer time (HRT) of 24 h. In the mixing tank, 200 mg of glycerol, 150 mg of NaNO3, and 15 mg of humic acid are added per liter of benzene-containing wastewater. The aerobic tank uses MBR membrane filtration with a flux of 20 L / m³. 2 •h, the sludge age of the activated sludge in the aerobic tank is >15 days.

[0035] The specific preparation process of the CuO / SiO2 catalyst described above is as follows:

[0036] Step S1: Vector pretreatment

[0037] Mesoporous SiO2 (pore size 10 nm) was modified with APTES and ultrasonically dispersed in 0.1 M EDTA solution to form a SiO2 dispersion (to remove metal impurities).

[0038] Step S2: Precipitation reaction

[0039] In a microfluidic reactor, a dispersion of Cu(NO3)2, (NH4)2CO3 and SiO2 is mixed (flow rate ratio 1:1:1, temperature 80-90℃).

[0040] Step S3: Washing and Purification

[0041] Electrodialysis washing (operating conditions: 1.5V / cm, 30min), followed by rinsing with 0.1mM EDTA.

[0042] Step S4: Microwave calcination

[0043] Step S41, Precursor pretreatment: Place the mesoporous SiO2 precursor in the microwave reaction chamber, introduce inert gas N2 at a flow rate of 50–200 mL / min, and continue purging for 5–10 minutes to remove air.

[0044] Step S42, Microwave heating stage: Under N2 atmosphere, the mesoporous SiO2 precursor is heated to 400±5℃ at a heating rate of 50–100℃ / min, while maintaining a constant N2 flow rate during the heating process.

[0045] Step S43, Constant temperature calcination stage: Hold at 400±5℃ for 10±1 minutes;

[0046] Step S44, Atmosphere switching stage: After the heat preservation is completed, switch the reaction atmosphere to air, with an air flow rate of 100–300 mL / min, and maintain for 5–10 minutes;

[0047] Step S45, Cooling and Collection: Turn off the microwave power and allow it to cool naturally to room temperature in an air environment.

[0048] Example 2

[0049] The only difference from Example 1 is:

[0050] The benzene concentration in the benzene-containing wastewater is 1100 mg / L. 50 mg of glycerol is added per liter of benzene-containing wastewater in the equalization tank. The gas-liquid ratio in the stripping tower is 300:1 (volume ratio). 190 mg of glycerol, 140 mg of NaNO3, and 12 mg of humic acid are added per liter of benzene-containing wastewater in the mixing tank.

[0051] Example 3

[0052] The difference from Example 1 is as follows:

[0053] The benzene concentration in the benzene-containing wastewater is 1050 mg / L. 45 mg of glycerol is added per liter of benzene-containing wastewater in the equalization tank. The gas-liquid ratio in the stripping tower is 295:1 (volume ratio). 210 mg of glycerol, 160 mg of NaNO3, and 18 mg of humic acid are added per liter of benzene-containing wastewater in the mixing tank.

[0054] Comparative Example 1

[0055] The only difference from Example 1 is:

[0056] No glycerol is added to the conditioning tank.

[0057] Comparative Example 2

[0058] The only difference from Example 1 is:

[0059] No humic acid is added to the mixing tank.

[0060] The parameters of Examples 1-3 and Comparative Examples 1-2 were detected and calculated using ultraviolet spectrophotometry and other detection methods during the operation process, and the results are shown in the table below.

[0061] Table 1. Detection data from Example 1

[0062]

[0063]

[0064] The total nitrogen removal rate in the table above is calculated from the total nitrogen content of the effluent from the aerobic tank and the total nitrogen content of the effluent from the anaerobic tank (the same applies below); the detection point for the sludge volume index is located at the end of the mixed liquor in the aerobic tank.

[0065] Table 2 Detection data from Example 2

[0066]

[0067] Table 3 Detection data from Example 3

[0068]

[0069]

[0070] Table 4 shows the detection data for Comparative Example 1.

[0071]

[0072] Table 5 shows the detection data for Comparative Example 2.

[0073]

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A benzene-containing wastewater treatment device, characterized in that, It includes a regulating tank, a stripping tower, a concentrator, a wet oxidation reactor, a heat exchanger, a vacuum separation tank, a neutralization tank, and a biological treatment system, all connected in sequence.

2. The benzene-containing wastewater treatment device according to claim 1, characterized in that, It also includes an exhaust gas treatment system connected to the exhaust port at the top of the stripping tower, the exhaust gas treatment system comprising a first condenser connected to the exhaust port at the top of the stripping tower and an activated carbon adsorber connected to the first condenser.

3. The benzene-containing wastewater treatment device according to claim 1, characterized in that, The biological treatment system includes an anaerobic tank connected to a neutralization tank and an aerobic tank connected to the anaerobic tank.

4. The benzene-containing wastewater treatment device according to claim 1, characterized in that, The catalyst used in the wet oxidation reactor is an eggshell-type CuO / SiO2 catalyst.

5. The benzene-containing wastewater treatment device according to claim 4, characterized in that, The preparation method of the CuO / SiO2 catalyst is as follows: Step S1, carrier pretreatment: Mesoporous SiO2 is modified with APTES and ultrasonically dispersed in 0.1M EDTA solution; Step S2, Precipitation reaction: In a microfluidic reactor, Cu(NO3)2, (NH4)2CO3 solution and SiO2 dispersion prepared in step S1 are mixed and reacted at a flow rate ratio of 1:1:1 at a temperature of 80-90℃. Step S3, Washing and Purification: The product prepared in step S2 is first washed by electrodialysis, and then rinsed with 0.1 mM EDTA solution; Step S4, calcination and shaping: The mesoporous SiO2 precursor loaded with Cu(OH)2 prepared in step S3 is calcined and shaped using microwave.

6. The benzene-containing wastewater treatment device according to claim 5, characterized in that, Step S4 specifically involves: Step S41, Precursor pretreatment: Place the mesoporous SiO2 precursor in the microwave reaction chamber, introduce inert gas N2 at a flow rate of 50–200 mL / min, and continue purging for 5–10 minutes to remove air. Step S42, Microwave heating stage: Under N2 atmosphere, the mesoporous SiO2 precursor is heated to 400±5℃ at a heating rate of 50–100℃ / min, while maintaining a constant N2 flow rate during the heating process. Step S43, Constant temperature calcination stage: Hold at 400±5℃ for 10±1 minutes; Step S44, Atmosphere switching stage: After the heat preservation is completed, switch the reaction atmosphere to air, with an air flow rate of 100–300 mL / min, and maintain for 5–10 minutes; Step S45, Cooling and Collection: Turn off the microwave power and allow it to cool naturally to room temperature in an air environment.

7. The benzene-containing wastewater treatment device according to claim 3, characterized in that, A mixing tank is set up between the anaerobic tank and the aerobic tank. In the mixing tank, 190-210 mg of glycerol, 140-160 mg of sodium nitrate and 12-18 mg of humic acid are added per liter of wastewater.

8. The benzene-containing wastewater treatment device according to claim 1, characterized in that, The gas-liquid volume ratio in the stripping tower is 290-300:

1.

9. The benzene-containing wastewater treatment device according to claim 1, characterized in that, The flash vapor phase from the pressure-reducing separator is condensed by the second condenser and then returned to the stripping tower.

10. The benzene-containing wastewater treatment device according to claim 1, characterized in that, 40-50 mg of glycerol is added to each liter of wastewater in the equalization tank.

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