A method for treating wastewater containing phenolic compounds

Abstract

This invention discloses a method for treating wastewater containing phenolic compounds, comprising the following steps: subjecting the wastewater to multi-stage dissolved air treatment, wherein the multi-stage dissolved air treatment includes a pre-stage dissolved air treatment and a post-stage dissolved air treatment, wherein the pressure of the pre-stage dissolved air treatment is lower than the pressure of the post-stage dissolved air treatment; subjecting the effluent from the multi-stage dissolved air treatment to a phenol oxidation reaction; and subjecting the effluent after the phenol oxidation reaction to multi-stage aeration treatment, wherein the hydraulic retention time is 0.75-1 h.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, and more specifically, relates to a method for treating wastewater containing phenolic compounds. Background Technology

[0002] Wastewater with high oil content, high acidity, high ammonia content, high phenol content, and high biotoxicity is difficult to treat, especially the phenolic substances it contains. Semi-coke wastewater is a typical example of this type of wastewater.

[0003] Semi-coke, also known as semi-coke or coke powder, is produced by burning high-quality Jurassic coal blocks abundant in the Shenfu Coalfield. As a new type of carbon material, it is widely used in the production of calcium carbide, ferroalloys, ferrosilicon, and silicon carbide due to its characteristics of high fixed carbon content, high resistivity, high chemical activity, low ash content, low aluminum content, low sulfur content, and low phosphorus content. It has become an irreplaceable carbon material. The production process of semi-coke generates a large amount of phenolic and ammonia wastewater, with chemical oxygen demand and ammonia nitrogen concentrations exceeding 30,000 mg / L and 3,000 mg / L, respectively. The wastewater contains high levels of pollutants, especially phenols, which are highly toxic to organisms.

[0004] Semi-coke wastewater refers to the wastewater generated during the low-temperature dry distillation of coal (approximately 500℃-800℃, though temperatures vary depending on the process). It contains recalcitrant organic pollutants such as phenols, tar, and ammonia, and its composition is similar to coking wastewater. The treatment of phenols is a key and challenging aspect. In recent years, numerous studies have been conducted on the treatment of coking wastewater, including incineration, electrochemical oxidation, coagulation, adsorption, and the use of flue gas to treat phenol-containing wastewater. However, these methods have been deterred by high costs or poor operability. Currently, factories widely use conventional biological treatment processes, but the effluent standards do not meet requirements. Summary of the Invention

[0005] 1. The problem to be solved

[0006] To address the problem of poor treatment efficiency in existing methods for treating wastewater with high phenol content, the present invention aims to provide a method for treating wastewater containing phenolic compounds.

[0007] 2. Technical Solution

[0008] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0009] 1) The wastewater is subjected to multi-stage dissolved air treatment, which includes a previous stage of dissolved air treatment and a subsequent stage of dissolved air treatment, wherein the pressure of the previous stage of dissolved air treatment is lower than the pressure of the subsequent stage of dissolved air treatment.

[0010] 2) Perform phenol oxidation reaction on the effluent from multi-stage dissolved air treatment;

[0011] 3) The effluent after the oxidation reaction of phenol is subjected to multi-stage aeration treatment with a hydraulic retention time of 0.75-1h.

[0012] Furthermore, in step 1),

[0013] The preceding stage of dissolved gas treatment is carried out using a dissolved gas pump with a head range of 40-50m.

[0014] The final stage of dissolved gas treatment is carried out using a dissolved gas tank, with a dissolved gas working pressure of 0.45-0.55 MPa.

[0015] Furthermore, in step 2), an oxidation treatment is carried out in a quinone reaction reactor;

[0016] The pH of the influent for the oxidation treatment is 8-11, and the residence time is 0.75-1h.

[0017] Furthermore, a disperser is used to disperse the effluent from the multi-stage dissolved air treatment into the quinone reaction reactor;

[0018] The disperser distributes water from the bottom of the quinone reactor and through a funnel-shaped water outlet.

[0019] Furthermore, the disperser includes a central tube and a conduit;

[0020] The central pipe includes an inlet end and an outlet end. The inlet end is connected to a multi-stage dissolved air system, and the outlet end is connected to a conduit.

[0021] The conduit includes an inlet and a distribution port. The inlet is connected to the outlet, and the distribution port is a funnel-shaped distribution port.

[0022] Furthermore, the effluent after the oxidation reaction of phenol is first subjected to baffled aeration treatment, and then subjected to multi-stage aeration treatment.

[0023] in,

[0024] From the water inlet side to the water outlet side, the spacing between the baffles and aeration plates gradually increases;

[0025] and,

[0026] The minimum spacing between the baffles and gas-gathering plates is ≥25mm, and the maximum spacing between the baffles and gas-gathering plates is ≤50mm.

[0027] Furthermore, the baffle-type aeration treatment is carried out using a baffle-type aeration plate, which is a segmented baffle plate with the spacing gradually increasing from the inlet side to the outlet side.

[0028] Furthermore, the bubbles generated by the defoaming and gas-gathering process are defoamed.

[0029] Furthermore, a defoaming treatment is performed using a defoaming system, which includes a hydraulic defoamer and a spraying system;

[0030] The spraying system is located at the top of the quinone reaction reactor;

[0031] The defoaming machine is located between the spray system and the baffle plate.

[0032] Furthermore, the deflection and gas concentration process is accompanied by exhaust gas treatment.

[0033] Powered by an induced draft fan, the gas produced by the oxidation reaction of phenol is drawn out of the reactor and subjected to water washing and alkali washing treatment.

[0034] The air volume of the fan is 10-30m³. 3 / h.

[0035] Furthermore, the multi-stage aeration treatment includes an agitation deaeration treatment stage and an oxidation aeration treatment stage;

[0036] The agitation, deaeration, and aeration stage involves an aeration volume of 10-15 m³ / h. 3 Aeration is gradually reduced from the inlet to the outlet.

[0037] During the oxidation aeration treatment stage, the aeration volume is 5-10 m³ / h. 3 .

[0038] Furthermore, the effluent from the agitation, deaeration, and aeration treatment is passed through the oxidation aeration treatment stage, then sequentially through the permeable plate with inclined holes and the grid plate before being discharged.

[0039] More specifically, a multi-stage aeration treatment is performed using an aeration system, which includes an aeration tank two, which includes aeration pipes, a sedimentation zone, an aeration zone, and a permeable plate disposed between the sedimentation zone and the aeration zone; the aeration pipes are disposed in the aeration zone.

[0040] The second aeration tank also includes an inlet, a sedimentation zone outlet, and an aeration zone outlet;

[0041] The water inlet is located in the sedimentation zone.

[0042] The second aeration tank also includes a grating plate, which is disposed between the permeable plate and the aeration zone.

[0043] Furthermore, the aeration system also includes an aeration tank, which includes an inlet and an outlet.

[0044] The inlet of the aeration tank is connected to the quinone reaction reactor;

[0045] The outlet of aeration tank one is connected to aeration tank two.

[0046] The inlet end of aeration tank 1 is considered the front end, and the outlet end of aeration tank 1 is considered the rear end.

[0047] The aeration rate in the aeration tank decreases from the front end to the back end.

[0048] Furthermore, reflux is also involved, with the effluent from the oxidation reaction of the phenol being refluxed to a multi-stage dissolved air treatment stage at a reflux ratio of 0%-100%; and / or,

[0049] The effluent from the multi-stage aeration treatment is recycled to the multi-stage dissolved air treatment stage, with a recycling ratio of 0%-100%.

[0050] Furthermore, the reactor (200) has a cylindrical body (230), the height-to-diameter ratio of which is generally in the range of 1.5-2.5, and can be calculated using empirical formulas:

[0051]

[0052] In the formula:

[0053] H is the height of the cylinder (230);

[0054] D is the diameter of the cylinder (230);

[0055] C represents the average COD (mg / L) of the influent;

[0056] T is the average inlet water temperature (°C);

[0057] Q is the average influent flow rate (m³ / s). 3 / h);

[0058] k is an empirical constant;

[0059] ε is a correction parameter, with a value range of -0.5 to 0.5.

[0060] Furthermore, the height of the baffle-type gas-gathering plate (220) is 0.5-0.6 times the height of the cylinder (230) of the quinone reactor (200).

[0061] 3. Beneficial effects

[0062] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0063] (1) Based on the principle of phenol oxidation reaction to form quinone (hereinafter referred to as quinolation reaction), this invention proposes a process for treating wastewater containing phenolic compounds. Through multi-stage dissolved air treatment, quinolation reaction treatment, and graded aeration treatment, the coupling of each step effectively achieves the treatment of wastewater containing phenolic compounds.

[0064] (3) The wastewater treatment method containing phenolic compounds provided by the present invention has a multi-stage dissolved air treatment step that combines low-pressure dissolved air and high-pressure dissolved air, thereby maximizing the reduction of energy consumption while ensuring the dissolved air effect.

[0065] (4) The wastewater treatment method containing phenolic compounds provided by the present invention utilizes a disperser in the phenol oxidation reaction step, which can effectively prevent clogging and distribute water evenly.

[0066] Its baffle-type air-gathering plate can efficiently gather tiny bubbles.

[0067] (5) The wastewater treatment method for phenolic compounds provided by the present invention has a defoaming treatment step that can specifically solve the problem of a large amount of foam generated in wastewater containing phenolic compounds, such as semi-coke wastewater during the quinone reaction.

[0068] (6) The wastewater treatment method containing phenolic compounds provided by the present invention uses multi-stage aeration to further treat the effluent of the quinone reactor, which can degas and deeply oxidize it, thereby enhancing the phenol removal effect.

[0069] The aeration step is a staged aeration, including a stirring deaeration aeration treatment stage and an oxidation aeration treatment stage. The stirring deaeration aeration treatment stage reduces energy consumption while ensuring the deaeration effect; the oxidation aeration treatment stage has the effects of shallow aeration and sedimentation, which can separate water quality, reduce siltation, and facilitate subsequent treatment.

[0070] (7) The wastewater treatment method for phenolic compounds provided by this invention can achieve continuous flow operation rather than intermittent operation. For wastewater of this type, especially wastewater such as semi-coke wastewater, the flocs produced after quinone treatment have high density and are easy to accumulate and adhere. Maintaining continuous flow operation can effectively prevent sludge accumulation problems in a static state. Attached Figure Description

[0071] Figure 1 A process flow diagram for wastewater treatment provided by the present invention;

[0072] Figure 2 A process flow diagram for wastewater treatment provided by the present invention;

[0073] Figure 3 A schematic diagram of the phenol oxidation reaction in accordance with the wastewater treatment method for phenolic compounds provided by this invention.

[0074] Figure 4 A schematic diagram of the overall structure of the wastewater treatment method containing phenolic compounds provided by the present invention;

[0075] Figure 5 A schematic diagram (top view) of the overall structure of the wastewater treatment method containing phenolic compounds provided by the present invention;

[0076] Figure 6 A schematic diagram of the structure of the disperser in the wastewater treatment method for phenolic compounds provided by the present invention;

[0077] Figure 7 A partially enlarged view of the disperser in the wastewater treatment method for phenolic compounds provided by the present invention;

[0078] Figure 8 This is a schematic diagram of the structure of the aeration tank II in the wastewater treatment method for phenolic compounds provided by the present invention. Detailed Implementation

[0079] The present invention will be further described below with reference to specific embodiments.

[0080] (1) Basic Principles

[0081] like Figures 1-3 As shown, this process unit is an integrated design, mainly composed of multi-stage dissolved air treatment steps, quinone reaction treatment steps, defoaming treatment steps, gas treatment steps, aeration treatment steps, etc. It utilizes the principle of air quinone treatment to treat wastewater with high phenol content and high biotoxicity, such as semi-coke wastewater. The following explanation will use semi-coke wastewater as an example.

[0082] During treatment, the semi-coke wastewater is first pressurized and dissolved in a multi-stage dissolved air system 100, and then released in a quinone reaction reactor 200 via a disperser 210. At this point, the pressure decreases, and the dissolved gas in the water forms a large number of tiny bubbles. The phenolic substances in the semi-coke wastewater react fully with the oxygen in the tiny bubbles, are oxidized to form quinone substances, and loose flocculent matter is formed and precipitated.

[0083] The quinone reactor 200 operates in an upflow mode, where the liquid flow, microbubbles, and flocs are propelled and continuously rise, overflowing after reaching a certain height. During the upward flow, the liquid passes through multi-stage aeration plates, where bubbles collide and aggregate under the deflection effect of the aeration plates, forming large bubbles, effectively reducing the number of bubbles in the effluent and facilitating subsequent treatment.

[0084] During the quinone reaction, semi-coke wastewater is prone to generating a large amount of foam. The top of the quinone reactor 200 is equipped with a defoaming system 300. The defoaming system 300 effectively controls foam by working together with a layered hydraulic defoaming unit and a spray system.

[0085] The gas produced by the quinone reactor 200 is collected in the gas treatment system 500 and discharged after two stages of gas washing: water washing and alkali washing.

[0086] After undergoing the quinone reaction, the semi-coke wastewater enters the aeration system 400, which serves to deaerate and deeply oxidize the wastewater. Aeration removes residual gases from the semi-coke wastewater while simultaneously oxidizing it, further enhancing the quinone reaction efficiency.

[0087] The device incorporates a reflux system, where the effluent from the quinone reactor 200 and the aeration system 400 is refluxed back to the front end of the device to mix with the raw water. This process homogenizes the water quality, reduces foam generation, and improves the device's treatment efficiency.

[0088] (2) Detailed explanation of water treatment using integrated devices (see...) Figures 4-8 ):

[0089] Multi-stage dissolved gas treatment steps:

[0090] Multi-stage dissolved gas treatment is performed using a multi-stage dissolved gas system 100;

[0091] The multi-stage dissolved air system 100 is divided into two sections: a low-pressure dissolved air system 120 and a high-pressure dissolved air system 110. Low-pressure dissolved air can be achieved using a dissolved air pump, while high-pressure dissolved air can be achieved using a dissolved air tank. Low-pressure dissolved air dissolves air into the influent of the device with lower energy consumption and a larger flow rate, while high-pressure dissolved air utilizes higher pressure to improve the dissolved air effect. The coupling of these two systems to form a multi-stage dissolved air system results in lower energy consumption and better dissolved air performance. In detail:

[0092] 001. The multi-stage dissolved air system 100 includes a low-pressure dissolved air system 120 and a high-pressure dissolved air system 110. The low-pressure dissolved air system 120 uses a dissolved air pump to dissolve air in the raw water, and the high-pressure dissolved air system 110 uses a dissolved air tank to dissolve air in the raw water after low-pressure dissolved air. The two stages are connected by a pipeline.

[0093] 002. The dissolved air pump used in the low-pressure dissolved air system 120 has a head range of 40-50m.

[0094] 003. The material of the flow-through part of the dissolved air pump used in the low-pressure dissolved air system 120 is resistant to corrosion from semi-coke wastewater.

[0095] 004. The high-pressure dissolved gas system 110 uses two or more dissolved gas tanks connected in parallel.

[0096] 005. The high-pressure dissolved air system 110 uses several dissolved air tanks, each with its own automatic valve that independently controls the water inlet and outlet. When some dissolved air tanks are in the dissolved air or water outlet state, it does not affect the water inlet of other dissolved air tanks.

[0097] 006. The dissolved gas system 110 uses a hollow dissolved gas tank made of stainless steel, with an inner lining resistant to corrosion from coke wastewater. It is supplied with air by an air compressor, and the dissolved gas working pressure is 0.45-0.55MPa.

[0098] 007. The dissolved gas system 110 uses a horizontal dissolved gas tank with a residence time of 4-5 minutes.

[0099] The reaction steps for the oxidation of phenol to quinone:

[0100] use Quinonization reactor 2 00 proceed The reaction of phenol to quinone ;

[0101] The quinone reaction reactor 200 is the main part of the equipment. The quinone reaction reactor 200 operates in an upflow manner and mainly consists of a disperser 210, a baffled aeration plate 220, and a cylindrical shell 230, and is coupled to the defoaming system 300. After being dissolved in air by the multi-stage dissolved air system 100, the raw water is released into the cylindrical shell 230 via the disperser 210. Inside the cylindrical shell 230, the pressure of the raw water decreases, releasing a large number of microbubbles. These microbubbles oxidize phenolic substances while simultaneously providing buoyancy to the flocs, preventing them from settling at the bottom of the cylindrical shell 230. In detail:

[0102] 001. The quinone reaction reactor 200 is a one-piece structure, with all components installed inside the cylindrical body 230. The cylindrical body 230 is a one-piece manufactured sealed structure, internally housing the disperser 210 and the baffle-type gas-gathering plate 220. The cylindrical body 230 is equipped with several water inlet and outlet ports, vent ports, etc. The cylindrical body also has installation points for a segmented defoaming system 300, and provides a gas outlet.

[0103] 002. The 230 cylinder material has good strength, and the 230 cylinder lining has good corrosion resistance, capable of withstanding the corrosion of semi-coke wastewater. For example, carbon steel can be used, with fiberglass lining for corrosion protection.

[0104] 003. The cylinder 230 is cylindrical with a conical bottom. The wastewater retention time is approximately 1 hour.

[0105] 004. The height-to-diameter ratio of the 230mm cylinder is generally in the range of 1.5-2.5, and can be calculated using empirical formulas:

[0106]

[0107] In the formula,

[0108] H is the height of the cylinder, 230.

[0109] D is the diameter of the cylinder, which is 230 mm.

[0110] C represents the average COD (mg / L) of the influent;

[0111] T is the average inlet water temperature (°C);

[0112] Q is the average influent flow rate (m³ / s). 3 / h);

[0113] k is an empirical constant, typically taken as 0.2;

[0114] ε is a correction parameter, with a value range of -0.5 to 0.5;

[0115] The value was determined based on experience, taking into account factors such as the usage environment, test results, and water quality characteristics.

[0116] 005. The quinone reaction reactor 200 uses a disperser 210 evenly distributed at the bottom of the device for water distribution. For example... Figure 3 , 4 As shown, the water distributor 210 includes a central tube (211) and a conduit (212);

[0117] The central pipe 211 includes an inlet end 211a and an outlet end 211b. The inlet end 211a is connected to the multi-stage dissolved air system 100.

[0118] The water outlet 211b is connected to the conduit 212;

[0119] The conduit includes an inlet 212a and a distribution port 212b. The inlet 212a is connected to the outlet 211b.

[0120] Mouth 212b is a funnel-shaped water distribution nozzle;

[0121] 006. The disperser 210 is arranged along a circumference on a plane. The plane where the disperser 210 is located is 0.2-0.5m above the bottom of the tank, and the height of the water inlet reserved in the cylinder 230 is consistent with the installation height of the disperser 210.

[0122] 007. The quinone reactor 200 is equipped with a baffle plate 220 in the middle to gather microbubbles, so that they collide with each other to form large bubbles.

[0123] 008. The baffle plate 220 used in the quinone reactor 200 has denser baffles on one side near the bottom of the cylinder 230 and sparser baffles on the other side. The material is resistant to corrosion from semi-coke wastewater.

[0124] 009. The height of the baffle plate 220 is 0.5-0.6 times the height of the cylinder 230 of the quinone reactor 200, and the installation method inside the cylinder 230 is welding.

[0125] 010. The outlet height of the quinone reactor 200 is 0.1-0.2m above the gas-gathering plate.

[0126] 011. The installation point for the defoamer 320 is reserved inside the cylinder 230 of the quinone reactor 200, at a height of 0.1-0.2m above the baffle plate 220.

[0127] 012. The quinone reactor 200 has a tail gas outlet inside the cylinder 230, which is located at the top of the cylinder 230 and the cylinder 230 is sealed with a cover.

[0128] Defoaming treatment steps:

[0129] Using defoaming system 300 Defoaming treatment ;

[0130] The defoaming system 300 includes a hydraulic defoamer 320 and a spraying system 310;

[0131] 001. The number of hydraulic defoamers 320 is 4-8, arranged in a ring with equal spacing on the same plane.

[0132] 002. The motor used in the 320 hydraulic defoamer is waterproof.

[0133] 003. The water defoamer 320 is installed in the cylinder 230 of the quinone reactor 200 by welding.

[0134] 004. The spray system 310 uses the device to produce water and uses a booster pump to supply water. The spray pipes are laid on the top of the cylinder 230 of the quinone reactor 200.

[0135] 005. The number of sprinkler heads in the 310 sprinkler system is 8-16, arranged in a ring with equal spacing on the same plane.

[0136] 006. The defoaming treatment is designed with a maximum spraying capacity of 30L / m³. 2 / min, the actual spray flow rate should be adjusted during use based on the foam generation.

[0137] 007. Set up a water tank or reservoir to store the spray water. The spray water source is the water produced by the device or water with better quality. The water tank or reservoir is equipped with a chemical dosing port, and defoamer can be added as needed.

[0138] Exhaust gas treatment steps:

[0139] Using gas processing system 500 Exhaust gas treatment ;

[0140] The gas treatment system 500 is mainly used to treat the exhaust gas from the quinone reactor 200. The gas treatment system of the quinone reactor 200 is a multi-stage gas scrubbing tower, which uses a water scrubbing + alkaline scrubbing two-stage gas scrubbing tower in series, and can specifically treat ammonia, hydrogen sulfide and other substances in the tail gas.

[0141] In detail:

[0142] 001. The exhaust gas mainly comes from the quinone reaction reactor 200, powered by an induced draft fan. It is first treated by a water scrubbing tower, and then by an alkaline scrubbing tower before being discharged.

[0143] 002. The air volume of the induced draft fan is 10-30m³. 3 Between / h.

[0144] 003. The washing water can be returned to the inlet of the device to homogenize the water quality.

[0145] Aeration treatment steps:

[0146] Using an aeration system 400 Aeration treatment ;

[0147] The aeration system 400 is a staged aeration system used to further treat the effluent from the quinone reactor 200. It consists of two connected aeration tanks with different aeration structures inside, and its function is degassing and deep oxidation. In detail:

[0148] 001. The aeration system 400 consists of two aeration tanks connected in series, namely aeration tank one and aeration tank two, with independent aeration pipes for each. The retention time of wastewater in the aeration system 400 is 1 hour.

[0149] 002. Both aeration tank one and aeration tank two use Roots blowers with aeration hoses for aeration. The hoses are treated to be hydrophobic and oleophobic to effectively prevent pollution and clogging.

[0150] 003. The aeration tank is rectangular, with one side receiving the effluent from the quinone reaction reactor 200. The aeration air volume is 2-3 m³ / h. 3 / m 2 The aeration rate is 1 / h, and a gradually decreasing aeration method is adopted, with the maximum aeration rate at the end not exceeding 50% of the aeration rate at the front end. The air volume at the front end of the tank is relatively large, which has a good stirring and degassing effect, and can further oxidize the wastewater; the air volume at the rear end is reduced, which reduces stirring, saves energy, facilitates bubble dissipation, and can control the amount of foam generated for subsequent treatment in the second aeration tank.

[0151] 004. Aeration tank two is rectangular and connected to aeration tank one. The partition or wall at the connection point only covers the upper half; the lower half is open. Aeration air volume: 1-1.5 m³ / h. 3 / m 2 / h, mainly for oxidation, with small aeration volume and little hydraulic agitation effect.

[0152] 005. For example Figure 5 As shown, aeration tank two serves both shallow aeration and sedimentation functions. A horizontally installed grid plate 422 divides aeration tank two into upper and lower sections. The lower section is the sedimentation zone 410, primarily for sedimentation, and a permeable plate 411 (or inclined plate, or inclined tube) is installed to enhance the sedimentation effect. The upper section is the aeration zone 420, primarily for aeration.

[0153] The semi-coke wastewater after quinone reaction contains a large amount of heavy flocs, which are prone to siltation and adhesion. Aeration disturbs the flocs to a certain extent, keeping the water flow in motion. This sacrifices some of the sedimentation effect, reduces floc accumulation, and enhances sludge removal.

[0154] 006. Aeration tank 2 is equipped with two outlets, located at the end of aeration zone 420 and sedimentation zone 410 respectively. The effluent from aeration zone 420 is the final effluent from the integrated semi-coke wastewater treatment device, while the effluent from sedimentation zone 410 contains a large amount of flocs and sludge, which is beneficial for resource recovery.

[0155] 007. The bottom of the second aeration tank has a slope of 2‰ to 3‰ along the direction of water flow.

[0156] Reflux:

[0157] The reflux ratio is adjustable from 0% to 100%. Water is refluxed from the effluent outlets of the quinone reactor 200 and the aeration system 400 back to the inlet of the integrated equipment, powered by a reflux pump, operating intermittently. The purpose of reflux is to homogenize the water quality and facilitate the continuous and stable operation of the quinone reactor 200.

[0158] Example 1

[0159] In this embodiment, the treated semi-coke wastewater has a COD content of approximately 35,000 mg / L and a phenolic content of approximately 4,000 mg / L; the treatment steps for the semi-coke wastewater are as follows:

[0160] 1) Multi-stage dissolved air treatment for wastewater

[0161] A multi-stage dissolved air treatment system 100 is used for multi-stage dissolved air treatment. The influent pH is 8, the temperature is 20℃, and the designed influent flow rate is 20m³ / h. 3 / h.

[0162] The multi-stage dissolved air system 100 is equipped with one low-pressure dissolved air pump with a flow rate of 30m³ / h. 3 / h, head 40m, equipped with two high-pressure dissolved air tanks, working pressure 0.45MPa, residence time 4min.

[0163] 2) Perform phenol oxidation reaction on the effluent from multi-stage dissolved air treatment.

[0164] The effluent from the multi-stage dissolved air treatment enters the quinolation reactor 200 via the disperser 210 at the bottom of the quinolation reactor 200, where the phenol oxidation reaction takes place inside the quinolation reactor 200.

[0165] As the oxidation reaction proceeds, the tiny bubbles and foams generated during the reaction are gathered by the baffle-type gas-gathering plate 220 and collide with each other to form large bubbles;

[0166] Furthermore, the foam formed by large air bubbles is removed by the defoaming system 300 located at the top of the cylinder 230 of the quinone reactor 200;

[0167] At the same time, the exhaust gas generated is sent by the induced draft fan to the multi-stage scrubbing tower of the gas treatment system 500 for treatment.

[0168] The detailed information on the equipment used in the process and its process parameters is as follows:

[0169] Based on empirical values, the inner diameter D of the cylindrical shell 230 of the quinone reactor 200 is taken as 2.5m, and the height-to-diameter ratio is calculated using an empirical formula.

[0170]

[0171] The height of the cylindrical body 230 of the quinone reaction reactor 200 is 6.06m, so we take the height H = 6m;

[0172] The water distributor 210 is 0.2m above the bottom of the cylinder 230. Six distributors 210 are arranged in a ring, 0.2m above the bottom of the cylinder 230. A baffle-type air-gathering plate 220 is installed at a height of 3m above the cylinder 230.

[0173] From the inlet side 220a to the outlet side 220b, the spacing of the baffle-type aeration plates 220 gradually increases; specifically, the spacing of the baffle-type aeration plates 220a on the inlet side 220a is 25mm, and the spacing of the baffle-type aeration plates 220b on the outlet side 220b is 50mm.

[0174] The residence time of the wastewater in the quinone reaction reactor 200 is approximately 0.75 hours.

[0175] The defoaming system 300 installed at the top of the cylindrical body 230 of the quinone reaction reactor 200 specifically consists of four hydraulic defoamers 320 and four spray nozzles forming a spray system 310 for foam removal. The top of the quinone reaction reactor 200 has an exhaust gas outlet, and an induced draft fan sends the exhaust gas from the quinone reaction reactor 200 to a multi-stage scrubbing tower in the gas treatment system 500 for treatment. The induced draft fan has an air volume of 10 m³ / s. 3 / h.

[0176] 3) The effluent from the oxidation reaction of phenol is subjected to multi-stage aeration treatment.

[0177] The overflow effluent from the quinone reactor 200 is sent to aeration tank 1, with an aeration rate of 3m³ / h. 3 / m 2 After aeration is gradually reduced to remove impurities, the final aeration rate is 1.5 m³ / h. 3 / m 2 / h. Gravity flow to aeration tank two, aeration rate 1.5m³ / h. 3 / m 2 The wastewater is treated in aeration tank 2 at a rate of / h and then discharged separately. The total retention time of the wastewater in aeration tanks 1 and 2 is 0.75h. The effluent is returned to the front end via a return pump, with the return ratio set to 0% to save on operating and maintenance costs.

[0178] Table 1. Water quality before and after treatment

[0179]

[0180]

[0181] Example 2

[0182] In this embodiment, the treated semi-coke wastewater has a COD content of approximately 35,000 mg / L and a phenolic content of approximately 15,000 mg / L; the treatment steps for the semi-coke wastewater are as follows:

[0183] 1) Multi-stage dissolved air treatment for wastewater

[0184] A multi-stage dissolved air treatment system 100 is used for multi-stage dissolved air treatment. The influent pH is 11, the temperature is 20℃, and the designed influent flow rate is 30m³ / h. 3 / h.

[0185] Its multi-stage dissolved air system 100 is equipped with a low-pressure dissolved air pump with a flow rate of 30m³ / h. 3 / h, head 50m; equipped with two high-pressure dissolved air tanks, working pressure 0.55MPa, residence time 5min.

[0186] 2) Perform phenol oxidation reaction on the effluent from multi-stage dissolved air treatment.

[0187] The effluent from the multi-stage dissolved air treatment enters the quinolation reactor 200 via the disperser 210 at the bottom of the quinolation reactor 200, where the phenol oxidation reaction takes place inside the quinolation reactor 200.

[0188] As the oxidation reaction proceeds, the tiny bubbles and foams generated during the reaction are gathered by the baffle-type gas-gathering plate 220 and collide with each other to form large bubbles;

[0189] Furthermore, the foam formed by large air bubbles is removed by the defoaming system 300 located at the top of the cylinder 230 of the quinone reactor 200;

[0190] At the same time, the exhaust gas generated is sent by the induced draft fan to the multi-stage scrubbing tower of the gas treatment system 500 for treatment.

[0191] The detailed information on the equipment used in the process and its process parameters is as follows:

[0192] Based on empirical values, the inner diameter D of the cylinder 230 of the quinone reactor 200 is taken as 3m, and the height-to-diameter ratio is calculated using an empirical formula.

[0193]

[0194] The height of the cylindrical body 230 of the quinone reaction reactor 200 is 7.48m, and the height H is taken as 7.5m. The water distribution disperser 230 is 0.5m above the bottom of the tank, and six dispersers are arranged in a ring. A baffle-type aeration plate 220 is installed at a height of 4.5m in the reactor.

[0195] From the inlet side 220a to the outlet side 220b, the spacing of the baffle-type aeration plates 220 gradually increases; specifically, the spacing of the baffle-type aeration plates 220a on the inlet side 220a is 25mm, and the spacing of the baffle-type aeration plates 220b on the outlet side 220b is 50mm.

[0196] The wastewater stays in the quinone reactor 200 for about 1 hour.

[0197] Four defoamers and eight spray nozzles are installed at the top of the cylindrical body 230 of the quinone oxidizing reactor 200 to remove foam. An exhaust gas outlet is located at the top of the reactor, and an induced draft fan sends the exhaust gas from the quinone oxidizing reactor 200 to a multi-stage scrubbing tower in the gas treatment system 500 for treatment. The induced draft fan has an air volume of 30 m³ / h. 3 / h.

[0198] 3) The effluent from the oxidation reaction of phenol is subjected to multi-stage aeration treatment.

[0199] The overflow effluent from the quinone reactor 200 is sent to aeration tank 1, with the aeration rate increasing from 2m³ / h. 3 / m 2 After a gradual reduction of aeration, impurities are removed until the final aeration rate is 1 m³ / h. 3 / m 2 / h. Gravity flow to aeration tank two, aeration rate 1m³. 3 / m 2 / h, after treatment in aeration tank two, the wastewater is discharged separately. The total retention time of the wastewater in aeration tank one and aeration tank two is 1 hour. The effluent from the device is returned to the front end via a return pump. Because this wastewater is difficult to treat, the return flow needs to be increased, and the return flow ratio is set to 100%.

[0200] Table 2. Water quality before and after treatment

[0201] Water quality indicators (mg / L) COD (mg / L) Phenolic compounds (mg / L) Before processing 35000 15000 After processing 11000 3800 Removal rate 70％ 75％

[0202] Comparative Example 1

[0203] The treatment process for semi-coke wastewater in this comparative example is basically the same as that in Example 2. The semi-coke wastewater treated is the same as that in Example 2, with the only difference being step 1).

[0204] In step 1) of this comparative example, instead of performing multi-stage dissolved air treatment on the wastewater, only a dissolved air pump (head 30-50m) or a dissolved air tank (pressure 0.35-0.5Mpa) is selected for single dissolved air treatment.

[0205] Table 3. Water quality before and after treatment

[0206] COD removal rate Phenolic removal rate Continuous operation Energy consumption Dissolved gas pump 45-55％ 50-60％ yes middle Dissolved gas tank 50-60％ 55-65％ no high

[0207] Based on this comparative example, it can be seen that multi-stage dissolved air treatment can produce better water treatment results while having lower energy consumption.

[0208] In continuous water treatment operation, multi-stage dissolved air systems save 8-10% more energy than dissolved air pumps or dissolved air tanks, and produce stable effluent.

[0209] Compared to Example 2, the reason for the decrease in removal rate in this comparative example is that the gas dissolving capacity is insufficient, resulting in insufficient oxygen for the subsequent oxidation reaction.

[0210] Comparative Example 2

[0211] The treatment process for semi-coke wastewater in this comparative example is basically the same as that in Example 2. The semi-coke wastewater treated is the same as that in Example 2, with the only difference being step 2.

[0212] In step 2) of this comparative example, the way the effluent from the multi-stage dissolved air treatment enters the quinone reactor 200 is not suitable for a disperser 210 with a funnel-shaped water distribution port, but rather a common perforated pipe is used.

[0213] Table 4. Quality of treated effluent

[0214] COD Phenols Removal rate after treatment 20％ 30％

[0215] 1. Average cleaning cycle (characterizing the ease with which the disperser becomes clogged):

[0216] The disperser 210 used in Example 2 has an average cleaning cycle of more than 90 days;

[0217] The single perforated tube used in Comparative Example 2: average cleaning cycle within 7 days;

[0218] 2. The reason for the decrease in removal rate is that the liquid flow is not sufficiently dispersed, resulting in incomplete oxidation reaction.

[0219] Comparative Example 3

[0220] The treatment process for semi-coke wastewater in this comparative example is basically the same as that in Example 2. The semi-coke wastewater treated is the same as that in Example 2, with the only difference being step 2.

[0221] In step 2) of this comparative example, the baffle-type aeration plates 220 are different, from the water inlet side 220a to the water outlet side 220b, and the spacing of the baffle-type aeration plates 220 remains unchanged at 50mm.

[0222] Table 5. Quality of treated effluent

[0223] COD Phenols Removal rate after treatment 55％ 60％

[0224] The removal rates of COD and phenolic substances in this comparative example both decreased, which may be due to the low gas aggregation efficiency of the oxidation process and poor agglomeration of bubbles and flocs.

[0225] Comparative Example 4

[0226] The treatment process for semi-coke wastewater in this comparative example is basically the same as in Example 2. The semi-coke wastewater treated is the same as in Example 2. The only difference is that the aeration system 400 used is different. Aeration tank 2 does not have a perforated permeable plate (411), a grid plate (422), a sedimentation zone 410 and an aeration zone 420. Aeration tank 2 is replaced with an ordinary horizontal flow aeration tank.

[0227] Table 6. Water quality before and after treatment

[0228] COD Phenols Removal rate after treatment 60％ 65％

[0229] 1. Compared to the aeration system 400 in Example 1, the water treatment effect of a conventional horizontal flow aeration tank is worse.

[0230] 2. Semi-coke wastewater is prone to producing sludge. Therefore, the equipment in this comparative example is prone to sludge accumulation and adhesion at the bottom of the pool during the treatment of semi-coke wastewater, which can cause blockage of the aeration pipe.

[0231] 3. Compared with Example 1, the semi-coke wastewater treated by the equipment in this comparative example has significantly more suspended matter in its effluent.

[0232] Comparative Example 5

[0233] This comparative example is basically the same as Example 1, except that: the overflow water from the quinone reactor 200 is sent to aeration tank 1, and aeration tank 1 does not use a gradual aeration treatment; its aeration rate is always maintained at 3m³. 3 / m 2 / h, flowing by gravity to aeration tank two, the aeration rate remains no less than 3m³ of the aeration rate in aeration tank one. 3 / m 2 / h.

[0234] Compared with the control group, the energy consumption of the aeration system increases by 12-15% due to the increase in aeration volume.

[0235] Table 7. Quality of treated effluent

[0236] COD Phenols Removal rate 60％ 64％

[0237] The quality of the effluent has declined, and the reasons for this decline are:

[0238] (1) In the gradually decreasing aeration mode, aeration tank one is conducive to the aggregation of flocs at the end and a smooth transition to aeration tank two. In this comparative example, aeration tank one always maintains a high aeration rate, which hinders the stability of flocs, is not conducive to the cooperation with aeration tank two, and weakens the treatment effect.

[0239] (2) In this comparative example, the aeration tank 2 maintains a large aeration volume, which causes violent agitation of the water body, destroys the design of stratified and graded water discharge, and makes the water quality of the effluent worse.

Claims

1. A method for treating wastewater containing phenolic compounds, said wastewater being generated during the production of semi-coke and comprising phenolic substances, the treatment method comprising: 1) The wastewater is subjected to multi-stage dissolved air treatment, which includes a previous stage of dissolved air treatment and a subsequent stage of dissolved air treatment, wherein the pressure of the previous stage of dissolved air treatment is lower than the pressure of the subsequent stage of dissolved air treatment. 2) Phenol oxidation reaction is carried out on the effluent from the multi-stage dissolved air treatment; the oxidation treatment is carried out in a quinone reactor (200), the pH of the influent for the oxidation treatment is 8-11, and the residence time is 0.75-1h; The effluent from the multi-stage dissolved air treatment is dispersed into the quinone reactor (200) using a disperser (210); the disperser (210) distributes water from the bottom of the quinone reactor (200) and through a funnel-shaped water outlet. 3) The effluent from the oxidation reaction of phenol is first subjected to deflection and gas-gathering treatment; Then, multi-stage aeration is performed, with a hydraulic retention time of 0.75-1 hour; Among them, from the water inlet side (220a) to the water outlet side (220b), the spacing of the baffle and aeration treatment plates gradually increases; and the minimum spacing of the baffle and aeration treatment plates is ≥25mm, and the maximum spacing of the baffle and aeration treatment plates is ≤50mm.

2. The method for treating wastewater containing phenolic compounds according to claim 1, characterized in that, In step 1), The preceding stage of dissolved gas treatment is carried out using a dissolved gas pump with a head range of 40-50m. The final stage of dissolved gas treatment is carried out using a dissolved gas tank, with a dissolved gas working pressure of 0.45-0.55 MPa.

3. The method for treating wastewater containing phenolic compounds according to claim 1 or 2, characterized in that, Defoaming treatment is performed on the bubbles generated by the baffled gas concentration process.

4. The method for treating wastewater containing phenolic compounds according to claim 3, characterized in that, The deflection and gas concentration process is accompanied by an exhaust gas treatment step. The exhaust gas treatment includes: using a blower to draw the gas generated by the oxidation reaction of phenol out of the quinone reactor (200), and then washing the gas with water and alkali. The air volume of the fan is 10-30m³. 3 / h.

5. The method for treating wastewater containing phenolic compounds according to claim 1 or 2, characterized in that, The multi-stage aeration treatment includes an agitation deaeration treatment stage and an oxidation aeration treatment stage. The agitation, deaeration, and aeration stage involves an aeration volume of 10-15 m³ / h. 3 Aeration is gradually reduced from the inlet to the outlet. During the oxidation aeration treatment stage, the aeration volume is 5-10 m³ / h. 3 .

6. The method for treating wastewater containing phenolic compounds according to claim 5, characterized in that, The effluent from the agitation, deaeration, and aeration treatment is then passed into the oxidation aeration treatment stage. After passing through the permeable plate (411) and the grating plate (422) in sequence, the water exits.

7. The method for treating wastewater containing phenolic compounds according to any one of claims 1 to 2, 4, and 6, characterized in that, It also involves reflux, with the effluent from the oxidation reaction of the phenol being refluxed to a multi-stage dissolved air treatment stage at a reflux ratio of 0%-100%; and / or, The effluent from the multi-stage aeration treatment is recycled to the multi-stage dissolved air treatment stage, with a recycling ratio of 0%-100%.

Images