Device and process for treating acid-containing wastewater in coal-to-ethylene glycol production process

Abstract

The invention discloses an acid-containing wastewater treatment device and process in a coal-to-ethylene glycol production process, and relates to the technical field of wastewater treatment, the acid-containing wastewater treatment device comprises a water inlet unit, a pretreatment unit, a filtering unit and a deep treatment unit which are sequentially connected through pipelines; the pretreatment unit comprises a pH meter, a thermometer II, two groups of hydrolysis acidification pools and a submersible stirrer; the deep treatment unit comprises a clean water tank, an ozone oxidation tower, an IC reactor and a homogenizing tank; ozone is added into the ozone oxidation tower through an ozone generator. According to the method, micromolecular organic matters such as ethylene glycol and methanol contained in the wastewater are used as electron donors, and under the action of facultative microorganisms, the acidic wastewater is naturally neutralized through a hydrolysis fermentation reaction, so that the pH value is increased to 4.5-5.5, and the medicament cost is effectively reduced.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to an apparatus and process for treating acidic wastewater in the coal-to-ethylene glycol production process. Background Technology

[0002] Coal-to-ethylene glycol is an industrial wastewater generated during the production of ethylene glycol from coal through processes such as gasification, syngas purification, oxalate synthesis, and hydrogenation. This wastewater is complex in composition, has a high pollution load, and is characterized by significant acidity (pH≤3), high concentrations of organic matter (COD 5000-10000 mg / L), high nitrate nitrogen (500-1000 mg / L), and high salinity (Cl⁻>5000 mg / L). If this wastewater is discharged directly without effective treatment, it will cause serious harm to aquatic ecosystems, soil environments, and human health.

[0003] Traditional treatment processes employ a "chemical neutralization + physicochemical pretreatment + aerobic biological treatment" route, which has the following drawbacks: Each ton of wastewater requires the addition of 3-5 kg ​​of liquid alkali (NaOH) to adjust the pH from 3 to 7, accounting for more than 35% of the treatment cost; excessive alkali addition leads to the accumulation of salts in subsequent biochemical units (Na⁺ concentration > 5,000 mg / L), inhibiting microbial activity.

[0004] Nitrate nitrogen denitrification requires the addition of methanol (based on COD / N≥4), which competes with COD degradation for carbon sources; aerobic processes (such as AO) have a removal rate of less than 40% for recalcitrant COD, and the COD in the effluent often exceeds the standard. Summary of the Invention

[0005] The present invention aims to provide a conventional, stable, low-energy-consumption, high pollutant removal rate, and simultaneous removal of organic and inorganic substances from ethylene glycol wastewater treatment equipment and process.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A wastewater treatment device for acidic wastewater from coal-to-ethylene glycol production includes an inlet unit, a pretreatment unit, a filtration unit, and a deep treatment unit connected sequentially by pipelines; wherein: The water inlet unit includes a flow meter, a cooling tower, and a thermometer to monitor the water inlet flow and temperature. It is also equipped with two diversion valves to divert part of the wastewater to the cooling tower for cooling, while the other part goes directly into the pretreatment unit. The pretreatment unit includes a pH meter, a thermometer, two sets of hydrolysis acidification tanks, and a submersible agitator. The filtration unit includes a high-density tank, a dosing system, a V-type filter, and a backwashing system. The dosing system sequentially adds lime, PAC, cationic polyacrylamide, and liquid alkali to adjust the pH value of the wastewater and perform chemical treatment. The backwashing system includes a backwash wastewater tank and an inclined plate flushing loop to periodically backwash the V-type filter. The advanced treatment unit includes a clear water tank, an ozone oxidation tower, an IC reactor, and a homogenization tank; the ozone oxidation tower is supplied with ozone through an ozone generator.

[0007] Preferably, the diversion valve of the water inlet unit automatically adjusts the diversion ratio according to the water inlet temperature: When the water temperature is >35℃, 70% of the wastewater enters the cooling tower to be cooled to 30℃, and 30% of the wastewater directly enters the pretreatment unit. The water temperature after mixing is 30-35℃. When the water temperature is ≤35℃, all wastewater enters the pretreatment unit directly.

[0008] Preferably, in the preprocessing unit: The hydrolysis acidification tank adopts a two-stage series structure, with the pH of the first stage controlled at 4.5-5.0 and the pH of the second stage controlled at 5.0-5.5; The high-density pool has an inclined plate sedimentation zone at the bottom and a water collection tank at the top for separating the clear water after sedimentation.

[0009] Preferably, in the filtering unit: The V-type filter uses homogeneous quartz sand filter media with a filter layer thickness of 1.2–1.5 m; The backwashing system uses a backwashing pump to pump the separated wastewater from the high-density tank back to the V-type filter tank, and the backwash wastewater flows into the backwash wastewater tank.

[0010] Preferably, it also includes a sludge treatment unit, which includes a sludge thickening tank and a sludge dewatering machine; The sludge thickening tank is used to thicken the sludge produced by the filtration unit. The supernatant is incorporated into the backwash wastewater tank and then returned to the inlet water unit. The sludge dewatering machine is a plate and frame filter press.

[0011] Preferably, the cooling tower is equipped with a temperature sensor to monitor the temperature of the wastewater after cooling, ensuring that the temperature of the mixed wastewater meets the inlet water requirements of the hydrolysis acidification tank.

[0012] A process for treating acidic wastewater during coal-to-ethylene glycol production includes the following steps: Hydrolysis acidification: Low pH acidic wastewater enters the hydrolysis acidification tank, where the pH is controlled at 4.5-5.5, the temperature at 30-35℃, and the HRT at 4-6h. Facultative microorganisms decompose macromolecular organic matter into small molecule acidic substances, and simultaneously achieve natural pH neutralization. High-density sedimentation: The hydrolyzed and acidified wastewater enters the high-density tank, where lime, PAC, cationic polyacrylamide and liquid alkali are added sequentially through the dosing system to adjust the pH to 7-8. The high-density tank is then combined with inclined plate sedimentation to remove suspended solids, hardness and silica. Advanced oxidation: The effluent from the high-density sedimentation tank enters the ozone oxidation tower, and ozone is added at an O3 / COD ratio of 1.2-1.5. Under the conditions of pH 7-8 and reaction time of 30-45 min, the recalcitrant organic matter is oxidized into biodegradable small molecules. Deep denitrification: The effluent from ozone oxidation enters the IC reactor, where the temperature is controlled at 35-38℃ and the HRT is 8-10h. Anaerobic bacteria convert nitrate nitrogen into nitrogen gas to achieve deep denitrification.

[0013] Preferably, the ozone dosage in the advanced oxidation step is calculated based on a mass ratio of O3 to COD of 1.2-1.5, and the ozone concentration is controlled at 80-100 mg / L.

[0014] Compared with the prior art, the present invention has the following advantages: This invention integrates physical and chemical impurity removal methods to achieve precise and graded removal of COD and nitrate nitrogen, and strengthens the synergistic control of inorganic pollutants such as silicon and hardness, forming a highly efficient purification system encompassing all elements: organic matter, nitrogen, and inorganic matter.

[0015] This invention utilizes small-molecule organic compounds such as ethylene glycol and methanol contained in wastewater as electron donors. Under the action of facultative microorganisms, the pH of acidic wastewater is naturally raised to 4.5-5.5 through hydrolysis and fermentation, thereby effectively reducing the cost of reagents.

[0016] 3. The ozone oxidation unit of this invention converts recalcitrant organic matter (such as phenols and long-chain alkanes, accounting for 40% to 60% of COD) in wastewater into small-molecule carboxylic acids (acetic acid, propionic acid, etc., accounting for 70% to 85% of COD), which serve as a high-quality carbon source for denitrifying bacteria in the IC anaerobic reactor. Compared with the traditional process that requires the addition of methanol (dosage of 1.5 kg / t water, cost of 25 yuan / t), the cost of adding an external carbon source is eliminated. Attached Figure Description

[0017] Figure 1 This is a process flow diagram of an acidic wastewater treatment device for the coal-to-ethylene glycol production process proposed in this invention.

[0018] In the diagram: 100, Inlet unit; 200, Pretreatment unit; 300, Filtration unit; 400, Advanced treatment unit; 1, Flow meter; 2, Thermometer 1; 3, Diverter valve; 4, pH meter; 5, Thermometer 2; 6, Submersible agitator; 7, Hydrolysis acidification tank; 8, Cooling tower; 9, Clear water tank; 10, Ozone oxidation tower; 11, High-density tank; 12, IC reactor; 13, Homogenization tank; 14, Sludge dewatering machine; 15, V-type filter; 16, Backwash wastewater tank; 17, Flushing loop; 18, Sludge thickening tank. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0020] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0021] In existing technologies, the acidic wastewater generated during coal-to-ethylene glycol production is characterized by strong acidity, high organic matter concentration, high nitrate nitrogen, and high salinity. Traditional treatment processes employ chemical neutralization combined with physicochemical pretreatment and aerobic biological treatment, which suffers from problems such as high treatment costs due to large consumption of liquid alkali, excessive sodium salt accumulation inhibiting microbial activity, the need for additional carbon sources for denitrification, and low removal efficiency of recalcitrant organic matter. For example, a large amount of liquid alkali needs to be added per ton of wastewater to adjust the pH value, causing the salinity concentration in subsequent biological treatment units to exceed the standard; the aerobic process has insufficient COD removal rate, making it difficult for the effluent to meet discharge standards.

[0022] Therefore, refer to Figure 1 This application proposes a wastewater treatment device for acidic wastewater from coal-to-ethylene glycol production, comprising an inlet unit 100, a pretreatment unit 200, a filtration unit 300, and a deep treatment unit 400 connected sequentially by pipelines. The inlet unit 100 is equipped with a flow monitoring and temperature control device, the pretreatment unit 200 is configured with a hydrolysis acidification tank 7, the filtration unit 300 integrates a multi-stage dosing and backwashing system, and the deep treatment unit 400 adopts a combination structure of ozone oxidation and anaerobic reactor.

[0023] Among them, the diversion valve 3 of the inlet unit 100 is a device that dynamically adjusts the ratio of wastewater entering the cooling tower 8 to wastewater directly entering the pretreatment unit 200 according to the wastewater temperature. By controlling the diversion, the water temperature after mixing meets the requirements of subsequent treatment. The hydrolysis acidification tank 7 of the pretreatment unit 200 is a reaction tank in which organic matter is decomposed by facultative microorganisms. Specifically, it can adopt a two-stage series tank structure. The mixing is promoted by the submersible agitator 6, and the acidic environment of the wastewater is used for natural neutralization. The high-density tank 11 of the filtration unit 300 is a sedimentation device with inclined plate settling function. The ozone oxidation tower 10 of the deep treatment unit 400 is a reactor in which ozone is added by an ozone generator. Specifically, it can adopt a gas-liquid mixing tower structure and use microporous aeration discs to improve ozone mass transfer efficiency.

[0024] Specifically, wastewater first enters the influent unit 100, where parameters are monitored by flow meter 1 and thermometer 2. The diversion valve 3 automatically adjusts the cooling ratio based on the water temperature. In the pretreatment unit 200, the wastewater stays in the hydrolysis acidification tank 7 for a certain period. The pH value and temperature in the hydrolysis acidification tank 7 are controlled by pH meter 4 and thermometer 5. Under acidic conditions, microorganisms decompose large organic molecules into small acidic substances. The wastewater then enters the filtration unit 300, where lime, PAC, polyacrylamide, and liquid alkali are added sequentially for chemical treatment. Suspended solids are settled in the high-density tank 11, and impurities are further trapped in the V-type filter 15. The backwashing system periodically cleans the filter media. The treated water from the V-type filter 15 is discharged to the clear water tank 9 for storage. In the advanced treatment stage, the ozone oxidation tower 10 converts recalcitrant organic matter into biodegradable substances. The IC reactor 12 removes nitrate nitrogen under anaerobic conditions. Finally, the water quality is homogenized in the homogenization tank 13 to ensure stable effluent.

[0025] Compared with existing technologies, traditional processes require a large amount of liquid alkali to neutralize acidic wastewater, while this solution utilizes the hydrolysis acidification process to naturally adjust the pH value, reducing the amount of reagents added; existing technologies use single physicochemical precipitation, while this solution improves the removal efficiency of suspended solids through multi-stage dosing and high-density tank 11 inclined plate sedimentation; traditional aerobic processes have limited capacity to treat recalcitrant COD, while this solution introduces ozone oxidation combined with IC reactor 12 to achieve deep degradation of organic matter and simultaneous denitrification.

[0026] Through the above technical solutions, this application effectively reduces the consumption of acid-base adjustment reagents, avoids the inhibitory effect of sodium salt accumulation on the biochemical unit, improves the organic matter removal efficiency through the synergistic effect of multi-stage physicochemical and biochemical treatment, and achieves efficient removal of nitrate nitrogen without the need for additional carbon source addition. The overall treatment cost is significantly reduced and the effluent quality is stable and meets the standards.

[0027] This application further proposes that the diversion valve 3 of the water inlet unit 100 automatically adjusts the diversion ratio according to the water inlet temperature: when the water temperature is >35℃, 70% of the wastewater enters the cooling tower 8 to be cooled to 30℃, and 30% of the wastewater directly enters the pretreatment unit 200, and the water temperature after mixing is 30-35℃; when the water temperature is ≤35℃, all the wastewater directly enters the pretreatment unit 200.

[0028] Among them, the diversion valve 3 refers to the regulating valve that controls the opening degree, and the change of its opening degree can change the wastewater diversion ratio. The automatic temperature regulation refers to the control system based on the feedback signal of the thermometer-2. Specifically, it can be realized by linking the PLC controller with the thermometer and adjusting the valve opening in real time through a preset program. The cooling tower 8 refers to the equipment that realizes heat exchange through water-air contact. The pretreatment unit 200 refers to the wastewater treatment module that includes the hydrolysis acidification tank 7. Specifically, it can be realized by connecting multiple biochemical reaction tanks in series. Its operating temperature needs to be controlled within the suitable range of microbial activity.

[0029] Specifically, when the inlet water temperature exceeds 35℃, the temperature sensor transmits a signal to the control system, driving the diversion valve 3 to direct 70% of the wastewater into the cooling tower 8 for cooling. The remaining 30% of uncooled wastewater directly enters the pretreatment unit 200. The cooling tower 8 uses a water distributor to evenly distribute the high-temperature wastewater across the packing layer, exchanging heat with counter-current air to stabilize the outlet water temperature at 30℃. The cooled wastewater mixes with the uncooled portion, and a thermometer monitors to ensure the mixed water temperature remains within the 30-35℃ range. When the inlet water temperature is below or equal to 35℃, the diversion valve 3 completely closes the cooling tower 8 channel, and all wastewater directly enters the pretreatment unit 200, avoiding unnecessary cooling energy consumption.

[0030] This application further proposes that in the pretreatment unit 200, the hydrolysis acidification tank 7 adopts a two-stage series structure, with the pH of the first stage controlled at 4.5-5.0 and the pH of the second stage controlled at 5.0-5.5; the high-density tank 11 is provided with an inclined plate sedimentation zone at the bottom and a water collection tank at the top for separating the clear water after sedimentation.

[0031] The two-stage series hydrolysis acidification tank 7 refers to connecting two acidification tanks sequentially. The pH range of the first stage can be 4.5-5.0, and the pH range of the second stage can be 5.0-5.5. This can be achieved through the linkage control of pH meter 4, thermometer 5, and dosing system. This structure adjusts the pH value in stages, allowing facultative microorganisms at different stages to decompose organic matter under suitable acidity and alkalinity. Specifically, when the wastewater enters the first-stage hydrolysis acidification tank 7, the pH value is controlled within the range of 4.5-5.0. Under this condition, acid-producing bacteria preferentially decompose large molecular organic matter into volatile fatty acids. Subsequently, the wastewater enters the second-stage hydrolysis acidification tank 7, where the pH value is raised to the range of 5.0-5.5, promoting the activity of hydrogen-producing and acetic acid-producing bacteria, further converting intermediate products into small molecular acid substances. After treatment, the wastewater enters the high-density tank 11, where suspended solids slide rapidly down the inclined surface to the bottom of the tank in the inclined plate settling zone. The separated clear water is discharged through the top collection tank, achieving efficient solid-liquid separation.

[0032] This application further proposes that the V-type filter 15 in the filtration unit 300 adopts homogeneous quartz sand filter media with a filter layer thickness of 1.2 to 1.5 meters; the backwashing system pumps the separated wastewater in the high-density tank 11 back to the V-type filter 15 through a backwashing pump, and the backwash wastewater flows into the backwash wastewater tank 16.

[0033] Among them, homogeneous quartz sand filter media refers to quartz sand filter media with uniform particle size distribution. Specifically, it can be achieved by filling with quartz sand with a particle size range of 0.8 to 1.2 mm. The uniform pore distribution improves filtration efficiency and reduces filter media caking. The backwashing system pumps the wastewater separated in the high-density tank 11 back to the V-type filter tank 15 through the backwashing pump. The wastewater separated in the high-density tank 11 is used as the backwash water source. Specifically, the wastewater can be pressurized by a centrifugal pump and injected into the bottom of the filter tank through the flushing loop 17. The hydraulic flushing removes the blockages on the surface of the filter media. The wastewater containing impurities after flushing is collected in the backwash wastewater tank 16 for subsequent return treatment.

[0034] Through the above technical solution, this application can effectively reduce the clogging frequency of the V-type filter 15, extend the filtration cycle, and realize the internal recycling of backwash wastewater, reduce the amount of chemical agents added and the amount of sludge generated, thereby reducing the overall operating cost.

[0035] This application further proposes an acidic wastewater treatment device for the coal-to-ethylene glycol production process, including a sludge treatment unit. The sludge treatment unit includes a sludge thickening tank 18 and a sludge dewatering machine 14. The sludge thickening tank 18 is used to thicken the sludge generated by the filtration unit 300, and the supernatant is incorporated into the backwash wastewater tank 16 and then returned to the inlet water unit 100. The sludge dewatering machine 14 is a plate and frame filter press.

[0036] Among them, the sludge thickening tank 18 refers to a structure that reduces the volume of sludge through gravity settling. Specifically, it can be achieved by using a radial flow sedimentation tank with a sludge scraper. Its function is to thicken sludge with a water content of 99% to 95% to 97%.

[0037] Among them, the sludge dewatering machine 14 refers to the equipment that achieves solid-liquid separation of sludge through mechanical pressure. Specifically, it can be achieved by using a plate and frame filter press. Its function is to further reduce the moisture content of concentrated sludge to 75% to 80%.

[0038] Among them, supernatant return refers to the reintroduction of the liquid separated during the sludge thickening process into the treatment system. Specifically, this can be achieved by connecting the backwash wastewater tank 16 and the inlet unit 100 through a pipeline. Its function is to avoid secondary pollution caused by the discharge of high-salt wastewater.

[0039] Specifically, the suspended solids carried by the backwash wastewater from filter unit 300 enter sludge thickening tank 18, where solid-liquid separation is achieved during settling. The thickened sludge is pumped to a plate and frame filter press, where it is dewatered and forms a sludge cake under a pressure of 0.6-0.8 MPa. The separated supernatant, containing unreacted reagents and dissolved salts, is introduced into backwash wastewater tank 16 and mixed with the influent before re-entering the treatment system.

[0040] This application further proposes that the cooling tower 8 is equipped with a temperature sensor to monitor the temperature of the wastewater after cooling, so as to ensure that the temperature of the mixed wastewater meets the inlet water requirements of the hydrolysis acidification tank 7.

[0041] Among them, the temperature sensor refers to the detection device installed on the outlet pipe of the cooling tower 8. Specifically, it can be implemented by a contact temperature probe or an infrared thermometer. It is used to obtain the temperature data of the cooled wastewater in real time and dynamically adjust the operating parameters of the cooling tower 8 according to the feedback data of the temperature sensor to ensure that the temperature of the mixed wastewater is within the preset range.

[0042] This application further proposes a process for treating acidic wastewater during coal-to-ethylene glycol production, including the following steps: Hydrolysis acidification: Low pH acidic wastewater enters the hydrolysis acidification tank 7, where the pH is controlled at 4.5-5.5, the temperature at 30-35℃, and the HRT at 4-6h. Facultative microorganisms decompose macromolecular organic matter into small molecule acidic substances, and simultaneously achieve natural pH neutralization. High-density sedimentation: The hydrolyzed and acidified wastewater enters the high-density tank 11, where lime, PAC, cationic polyacrylamide and liquid alkali are added sequentially through the dosing system to adjust the pH to 7-8. The high-density tank 11 is then combined with inclined plate sedimentation to remove suspended solids, hardness and silica. Advanced oxidation: The effluent from the high-density sedimentation tank enters the ozone oxidation tower 10, and ozone is added at an O3 / COD ratio of 1.2-1.5. Under the conditions of pH 7-8 and reaction time of 30-45 min, the recalcitrant organic matter is oxidized into biodegradable small molecules. Deep denitrification: The effluent from ozone oxidation enters IC reactor 12, where the temperature is controlled at 35-38℃ and the HRT is 8-10h. Anaerobic bacteria convert nitrate nitrogen into nitrogen gas to achieve deep denitrification.

[0043] Hydrolysis acidification refers to the process of decomposing organic matter by microorganisms under anaerobic conditions. It is achieved by using two-stage series hydrolysis acidification tanks 7. By controlling the pH gradient, facultative microorganisms gradually decompose large molecular organic matter, while the acidity and alkalinity of the wastewater itself are used to achieve neutralization.

[0044] High-density sedimentation refers to the process of enhancing the settling of suspended solids through chemical agents. It is achieved by using inclined plate settling zones and water collection tanks in synergy. The process involves adding lime, PAC, and cationic polyacrylamide in stages to form flocs and accelerate the settling process.

[0045] Advanced oxidation refers to the process of using ozone oxidation to degrade recalcitrant organic matter. It is achieved by controlling the O3 / COD mass ratio through an ozone generator, and under alkaline conditions, it promotes the breaking of organic matter chains to generate biodegradable substances.

[0046] Deep denitrification refers to the process of removing nitrate nitrogen in an anaerobic environment. An IC reactor 12 is used to maintain the activity of anaerobic bacteria through temperature control in order to complete the denitrification reaction.

[0047] Specifically, the wastewater treatment process first involves microbial decomposition in a low-pH environment using a hydrolysis acidification tank 7. For example, the pH of the first-stage tank is controlled at 4.5-5.0, and the pH of the second-stage tank at 5.0-5.5, utilizing the acidic characteristics of the wastewater to reduce the amount of neutralizing agents needed. Subsequently, lime, PAC, and cationic polyacrylamide are added in stages in a high-density tank 11. For example, lime is added first to adjust the pH to 6.5-7.0, then PAC is added to form flocculants, and finally, cationic polyacrylamide is used to accelerate floc settling. In the ozone oxidation stage, the ozone dosage is precisely controlled, for example, by dynamically adjusting the output power of the ozone generator based on the influent COD value, causing recalcitrant organic matter to be oxidized and decomposed into smaller molecules such as acetic acid and formic acid. Finally, in the IC reactor 12, a constant temperature environment of 35-38℃ is maintained, for example, using a circulating hot water jacket for insulation, prompting anaerobic bacteria to convert nitrate nitrogen into nitrogen gas, which is then discharged from the system.

[0048] Compared to existing technologies, which require large amounts of liquid alkali for chemical neutralization, this process utilizes hydrolysis and acidification to simultaneously achieve natural pH neutralization. For example, when the influent pH is 3, after two stages of hydrolysis and acidification, the pH can be raised to 5.5, reducing the amount of liquid alkali used by approximately 60%. Existing technologies require the additional addition of methanol as a carbon source for denitrification, while this process uses ozone oxidation to generate biodegradable small-molecule organic compounds, such as oxidizing benzene ring compounds into fatty acids, providing an endogenous carbon source for subsequent nitrogen removal. Existing aerobic processes have insufficient COD removal rates, while this process, through the synergistic effect of advanced ozone oxidation and IC reactor 12, converts recalcitrant COD into biodegradable substances before anaerobic degradation, increasing the overall removal rate to over 85%.

[0049] This application further proposes that the ozone dosage in the advanced oxidation step be calculated based on a mass ratio of O3 to COD of 1.2-1.5, and the ozone concentration be controlled at 80-100 mg / L.

[0050] The ozone dosage is calculated based on an O3 to COD mass ratio of 1.2-1.5, which means dynamically adjusting the ozone dosage ratio according to the chemical oxygen demand content in the wastewater. This ratio can ensure that recalcitrant organic matter is fully oxidized and avoid increased operating costs caused by excessive dosage.

[0051] Among them, controlling the ozone concentration at 80-100 mg / L means maintaining the effective oxidation concentration in the reaction system by adjusting the power of the ozone generator and the gas flow rate. This concentration range can ensure the oxidation reaction rate and prevent ozone escape from causing secondary pollution.

Claims

1. A device for treating acidic wastewater during coal-to-ethylene glycol production, characterized in that, It includes an inlet unit (100), a pretreatment unit (200), a filtration unit (300), and a deep treatment unit (400) connected in sequence by pipes; wherein: The water inlet unit (100) includes a flow meter (1), a cooling tower (8) and a thermometer (2) for monitoring the water inlet flow and water temperature. It is equipped with two diversion valves (3) to divert part of the wastewater to the cooling tower (3) for cooling, and the other part directly enters the pretreatment unit (200). The pretreatment unit (200) includes a pH meter (4), a thermometer (5), two sets of hydrolysis acidification tanks (7) and a submersible agitator (6). The filtration unit (300) includes a high-density tank (11), a dosing system, a V-type filter (15), and a backwashing system. The dosing system sequentially adds lime, PAC, cationic polyacrylamide, and liquid alkali to adjust the pH value of the wastewater and perform chemical treatment. The backwashing system includes a backwash wastewater tank (16) and an inclined plate flushing loop (17) to periodically backwash the V-type filter (15). The deep treatment unit (400) includes a clear water tank (9), an ozone oxidation tower (10), an IC reactor (12), and a homogenization tank (13); the ozone oxidation tower (10) adds ozone through an ozone generator.

2. The apparatus according to claim 1, characterized in that, The diversion valve (3) of the water inlet unit automatically adjusts the diversion ratio according to the water inlet temperature: When the water temperature is >35℃, 70% of the wastewater enters the cooling tower (8) to be cooled to 30℃, and 30% of the wastewater directly enters the pretreatment unit (200). The water temperature after mixing is 30-35℃. When the water temperature is ≤35℃, all wastewater directly enters the pretreatment unit (200).

3. The apparatus according to claim 1, characterized in that, In the preprocessing unit (200): The hydrolysis acidification tank (7) adopts a two-stage series structure, with the pH of the first stage controlled at 4.5-5.0 and the pH of the second stage controlled at 5.0-5.5; The high-density pool (11) has an inclined plate settling zone at the bottom and a water collection tank at the top for separating the clear water after sedimentation.

4. The apparatus according to claim 1, characterized in that, In the filter unit (300): The V-type filter (15) uses homogeneous quartz sand filter media with a filter layer thickness of 1.2 to 1.5 m; The backwashing system pumps the separated wastewater in the high-density tank (11) back to the V-type filter tank (15) via a backwashing pump, and the backwash wastewater flows into the backwash wastewater tank (16).

5. The apparatus according to claim 1, characterized in that, It also includes a sludge treatment unit, which includes a sludge thickening tank (18) and a sludge dewatering machine (14). The sludge thickening tank (18) is used to thicken the sludge produced by the filtration unit (300). The supernatant is incorporated into the backwash wastewater tank (16) and then returned to the inlet water unit (100). The sludge dewatering machine (14) is a plate and frame filter press.

6. The apparatus according to claim 1, characterized in that, The cooling tower (8) is equipped with a temperature sensor to monitor the temperature of the wastewater after cooling, ensuring that the temperature of the mixed wastewater meets the inlet water requirements of the hydrolysis acidification tank (7).

7. A process for treating acidic wastewater during coal-to-ethylene glycol production, employing the apparatus described in claim 1, and comprising the following steps in sequence: Hydrolysis acidification: Low pH acidic wastewater enters the hydrolysis acidification tank (7), and the pH is controlled at 4.5-5.5, the temperature at 30-35℃, and the HRT at 4-6h. Facultative microorganisms decompose macromolecular organic matter into small molecule acid substances and simultaneously achieve natural pH neutralization. High-density sedimentation: The hydrolyzed and acidified wastewater enters the high-density tank (11), and lime, PAC, cationic polyacrylamide and liquid alkali are added in sequence through the dosing system to adjust the pH to 7-8. The suspended solids, hardness and silica are removed by inclined plate sedimentation in the high-density tank (11). Advanced oxidation: The effluent from the high-density sedimentation tank enters the ozone oxidation tower (10), and ozone is added according to O3 / COD=1.2-1.

5. Under the conditions of pH 7-8 and reaction time of 30-45min, the recalcitrant organic matter is oxidized into biodegradable small molecules. Deep denitrification: The effluent from ozone oxidation enters the IC reactor (12), where the temperature is controlled at 35-38℃ and the HRT is 8-10h. The anaerobic bacteria convert nitrate nitrogen into nitrogen gas to achieve deep denitrification.

8. The process according to claim 7, characterized in that, In the advanced oxidation step, the ozone dosage is calculated based on a mass ratio of O3 to COD of 1.2-1.5, and the ozone concentration is controlled at 80-100 mg / L.

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