Comprehensive treatment method and system for coal chemical wastewater

Abstract

The invention relates to the technical field of chemical wastewater treatment, and discloses a comprehensive treatment method and system for coal chemical wastewater, coking wastewater, methanol gasification wastewater and coal dressing wastewater are conveyed to the same water distributor through a wastewater conveying pipeline, a defoaming agent and polyacrylamide are added at a dosing port of the water distributor, and the water distributor is used for uniformly mixing to dilute the hardness of the gasification wastewater; mixed wastewater enters an inclined plate area of the horizontal-flow sedimentation tank, suspended solids are removed through the inclined plate area of the horizontal-flow sedimentation tank, then the mixed wastewater enters an air floatation device, and residual suspended solids in the wastewater are deeply removed by means of the air floatation principle; the wastewater flows into the anaerobic tank, the anoxic tank and the aerobic tank to gradually remove ammonia nitrogen and COD (Chemical Oxygen Demand), and then is purified through mud-water separation operation of the secondary sedimentation tank; the purified wastewater reaching the standard enters a reclaimed water recycling device and is treated to be recycled, so that water resources are recycled; the alkalinity is effectively utilized to remove hardness, the biodegradability and degradation efficiency are improved, and the investment of wastewater treatment facilities and equipment is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical industrial wastewater treatment, and particularly relates to a comprehensive treatment method and system for coal chemical industry wastewater. Background Art

[0002] In the coal chemical industry, coking wastewater, methanol gasification wastewater, and coal preparation wastewater are the main wastewater sources, and each has complex and intractable characteristics; coking wastewater features high COD (chemical oxygen demand), high ammonia nitrogen, high oil content, and low biodegradability. The oil in it includes emulsified oil, a small amount of light oil, and heavy oil. Traditional oil separation and removal tanks can only remove heavy oil, and air flotation can only remove light oil. Emulsified oil entering the biochemical system will greatly hinder the microbial degradation efficiency. Moreover, high COD and low biodegradability result in a large amount of macromolecular organic matter remaining undegradable after biochemical treatment. Even with ozone / Fenton oxidation treatment, the cost remains high. In addition, high ammonia nitrogen wastewater is likely to impact the nitrification system, making it difficult for the system to operate stably for a long time; methanol gasification wastewater has the characteristics of high hardness, high ammonia nitrogen, and high suspended solids. Currently, the technology of sedimentation tank + high-density tank for hardness removal + A2O is often used. However, although adding a dispersant can reduce the risk of pipeline and equipment scaling, it causes a large dosage of chemicals for double-alkali method hardness removal, poor effect, and high cost. At the same time, high suspended solids and large amounts of sludge result in a large consumption of coagulation and flocculation agents and a large amount of sludge production. High ammonia nitrogen also causes C / N imbalance in the biochemical system and low biochemical degradation efficiency; the prominent problems of coal preparation wastewater are high turbidity, poor sedimentation performance, and poor biodegradability. The coal slime particles in the water not only have small particle sizes and high concentrations but also form a stable colloidal system due to the strong negative charge on the particle surface, making sedimentation extremely difficult, with a huge consumption of coagulation agents. Moreover, the flotation agents, inhibitors, and foaming agents such as light diesel oil and kerosene added during the coal preparation process are all refractory organic substances. When using the coagulation sedimentation + secondary sedimentation tank technology for treatment, numerous sedimentation tanks and aeration tanks are required, occupying a large area. Summary of the Invention

[0003] The purpose of the present invention is to solve the above problems and design a comprehensive treatment method and system for coal chemical industry wastewater.

[0004] The first aspect of the present invention provides a comprehensive treatment method for coal chemical industry wastewater, and the comprehensive treatment method for coal chemical industry wastewater includes the following steps:

[0005] S1. Through a wastewater conveying pipeline, coking wastewater, methanol gasification wastewater, and coal preparation wastewater are conveyed to the same water distributor, and an antifoaming agent and polyacrylamide are added at the chemical dosing port of the water distributor and mixed evenly by the water distributor to dilute the hardness of the gasification wastewater.

[0006] S2. The mixed wastewater enters the inclined plate area of the horizontal flow sedimentation tank, and the suspended solids are removed through the inclined plate area of the horizontal flow sedimentation tank, and then enters the air flotation device. By means of the air flotation principle, the remaining suspended solids in the wastewater are deeply removed.

[0007] S3. The wastewater flows into the anaerobic tank, anoxic tank, and aerobic tank to gradually remove ammonia nitrogen and COD, and then undergoes solid-liquid separation operation in the secondary sedimentation tank for purification;

[0008] S4. The wastewater after reaching the purification standard enters the reclaimed water reuse device, and after treatment, it is reused to achieve the recycling of water resources.

[0009] Optionally, in the first implementation manner of the first aspect of the present invention, step S1 specifically includes the following process: The coking wastewater, methanol gasification wastewater, and coal preparation wastewater are transported to the same water distributor through the wastewater transport pipeline. The flow rate of the wastewater transport pipeline is 0.5 - 1.5 m / s. Defoamer is accurately added at the chemical addition port of the water distributor to eliminate foam, and polyacrylamide is added for coagulation and flocculation. The mixture is evenly mixed through the water distributor for 10 - 15 minutes by the way of combining mechanical stirring and hydraulic circulation, and the hardness of the gasification wastewater is diluted to 200 - 400 mg / L.

[0010] Optionally, in the second implementation manner of the first aspect of the present invention, the defoamer is selected as an organosilicon defoamer, and the dosage is 10 - 50 ppm; the polyacrylamide is selected as an anionic type with a molecular weight of 8 million - 15 million, and the dosing concentration is 0.1% - 0.5%.

[0011] Optionally, in the third implementation manner of the first aspect of the present invention, step S2 specifically includes the following process: The mixed wastewater enters the inclined plate area of the horizontal flow sedimentation tank. The hydraulic retention time in the inclined plate area of the horizontal flow sedimentation tank is controlled at 1.5 - 2.5 hours. The included angle between the inclined plate and the horizontal direction is set at 45° - 60°, and the inclined plate spacing is 80 - 120 mm. Suspended solids are removed through sedimentation, and the content of suspended solids in the wastewater is reduced to less than 50 mg / L; then it enters the air flotation device. The air flotation device adopts the dissolved air flotation process, and the dissolved air pressure is controlled at 0.3 - 0.5 MPa, and the air flotation time is 20 - 30 minutes. During this period, the slag scraping system in the air flotation device operates continuously, and the slag scraping plate slowly moves at a speed of 1 - 2 meters per minute to scrape and collect the floating slag layer in time, deeply removing the residual suspended solids in the wastewater, and reducing the suspended solids in the effluent to less than 20 mg / L.

[0012] Optionally, in the fourth implementation manner of the first aspect of the present invention, after the wastewater enters the air flotation device, the air supply system is started, and the air is compressed to 0.3 - 0.5 MPa and then injected into the dissolved air tank, so that the air is fully dissolved in water under high pressure to form dissolved air water. The dissolved air water is quickly decompressed and released through the release device, generating a large number of bubbles with diameters of 20 - 50 μm, which are evenly dispersed in the wastewater. The residual suspended solids, colloidal particles, and some difficult-to-precipitate organic matters in the wastewater will adhere to the surface of the bubbles due to surface activity and float to the water surface to form a floating slag layer. The air flotation time is controlled at 20 - 30 minutes.

[0013] Optionally, in the fifth implementation manner of the first aspect of the present invention, step S3 specifically includes the following process: The wastewater flows into the anaerobic tank, anoxic tank, and aerobic tank. The temperature of the anaerobic tank is 30-35°C, the pH value is 6.8-7.2, and the hydraulic retention time is 8-12 hours. Anaerobic bacteria are used to decompose macromolecular organic matter into small-molecular organic matter; the temperature of the anoxic tank is 25-30°C, the pH value is 7.0-7.5, and the hydraulic retention time is 6-10 hours. Part of the ammonia nitrogen is removed through denitrification; the temperature of the aerobic tank is 20-25°C, the pH value is 7.2-7.8, the dissolved oxygen concentration is 2-4 mg / L, and the hydraulic retention time is 12-18 hours. Aerobic microorganisms are used to oxidize and decompose organic matter and remove ammonia nitrogen to gradually remove ammonia nitrogen and COD. Then, through the mud-water separation operation of the secondary sedimentation tank, the surface hydraulic load of the secondary sedimentation tank is 0.8-1.2 m 3 / (m 2 ·h), for purification, so that the effluent COD is less than 60 mg / L and the ammonia nitrogen is 0 mg / L.

[0014] Optionally, in the sixth implementation manner of the first aspect of the present invention, step S4 specifically includes the following process: The wastewater after reaching the purification standard enters the reclaimed water reuse device. The reclaimed water reuse device adopts the ultrafiltration-reverse osmosis dual-membrane filtration process. The pore size of the ultrafiltration membrane is 0.001-0.01 μm, the operating pressure is 0.1-0.3 MPa, the molecular weight cut-off of the reverse osmosis membrane is 100-200 Da, and the operating pressure is 0.8-1.2 MPa. After treatment, reuse is achieved to realize the recycling of water resources.

[0015] The second aspect of the present invention provides a coal chemical wastewater comprehensive treatment system. The coal chemical wastewater comprehensive treatment system includes a wastewater delivery pipeline, a water distributor, an inclined plate area of a horizontal flow sedimentation tank, a flotation device, a microbial ecological environment, a secondary sedimentation tank, and a reclaimed water reuse device. Among them,

[0016] The wastewater delivery pipeline is used to connect each wastewater generation source with the water distributor;

[0017] The water distributor is equipped with a chemical addition port for adding defoamer and polyacrylamide and has a mixing structure inside;

[0018] The inclined plate area of the horizontal flow sedimentation tank removes suspended solids by setting the inclined plate angle and spacing;

[0019] The flotation device has a gas supply and slag scraping system to remove suspended solids;

[0020] The microbial ecological environment includes an anaerobic tank, anoxic tank, and aerobic tank for removing ammonia nitrogen and COD;

[0021] The secondary sedimentation tank is used for mud-water separation;

[0022] The reclaimed water reuse device is used for wastewater reuse.

[0023] In the technical solution provided by the present invention, coking wastewater, methanol gasification wastewater, and coal preparation wastewater are transported to the same water distributor through a wastewater transportation pipeline. Defoaming agent and polyacrylamide are added at the chemical dosing port of the water distributor, and after being mixed evenly by the water distributor, the hardness of the gasification wastewater is diluted. The mixed wastewater enters the inclined plate area of the horizontal flow sedimentation tank, and the suspended solids are removed through the inclined plate area of the horizontal flow sedimentation tank, and then enters the air flotation device. By means of the air flotation principle, the residual suspended solids in the wastewater are deeply removed. The wastewater flows into the anaerobic tank, anoxic tank, and aerobic tank to gradually remove ammonia nitrogen and COD, and then is purified through the sludge-water separation operation of the secondary sedimentation tank. The wastewater after reaching the standard enters the reclaimed water reuse device, and after treatment, it is reused to achieve the recycling of water resources. The present invention utilizes the characteristics of the wastewater quality, effectively uses alkalinity to remove hardness, reduces the cost of hardness removal agents, and the coal slime in the gasification fine slag and coal preparation wastewater adsorbs and removes emulsified oil and macromolecular refractory organic matter in the wastewater, improving the biodegradability. Through dilution, the COD and ammonia nitrogen indexes in the wastewater are reduced, the operation of the biochemical system is stabilized, the degradation efficiency is improved, and the investment in wastewater treatment facilities and equipment is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] By reading the following detailed description of the preferred embodiments, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present invention.

[0025] Figure 1 It is a schematic diagram of an embodiment of the integrated treatment method for coal chemical wastewater provided by an embodiment of the present invention;

[0026] Figure 2 It is a schematic diagram of the structure of the integrated treatment system for coal chemical wastewater provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] The terms "first", "second", "third", "fourth", etc. (if any) in the specification, claims and above-mentioned drawings of the present invention are used to distinguish similar objects and do not have to be used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments described here can be implemented in an order different from that shown or described here. In addition, the term "comprising" or "having" and any variation thereof are intended to cover non-exclusive inclusion. For example, a process, method, device, product or device that includes a series of steps or units does not have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0028] For ease of understanding, the specific process of the embodiment of the present invention will be described below. Please refer to Figure 1Schematic diagram of an embodiment of the comprehensive treatment method for coal chemical wastewater provided by an embodiment of the present invention. The method specifically includes the following steps:

[0029] S1. Transfer coking wastewater, methanol gasification wastewater, and coal preparation wastewater to the same water distributor through a wastewater transfer pipeline. Add an antifoaming agent and polyacrylamide at the chemical dosing port of the water distributor, and mix evenly through the water distributor to dilute the hardness of the gasification wastewater.

[0030] S2. The mixed wastewater enters the inclined plate area of the horizontal flow sedimentation tank. Remove suspended solids through the inclined plate area of the horizontal flow sedimentation tank, and then enter the air flotation device. With the aid of the air flotation principle, deeply remove the remaining suspended solids in the wastewater.

[0031] S3. The wastewater flows into the anaerobic tank, anoxic tank, and aerobic tank to gradually remove ammonia nitrogen and COD, and then undergoes the sludge-water separation operation in the secondary sedimentation tank for purification.

[0032] S4. The wastewater that meets the purification standard enters the reclaimed water reuse device and is treated for reuse to achieve the recycling of water resources.

[0033] In this embodiment, step S1 specifically includes the following process: Transfer coking wastewater, methanol gasification wastewater, and coal preparation wastewater to the same water distributor through a wastewater transfer pipeline. The flow rate of the wastewater transfer pipeline is 0.5 - 1.5 m / s. Precisely add an antifoaming agent at the chemical dosing port of the water distributor to eliminate foam, add polyacrylamide for coagulation and flocculation, and mix evenly through the water distributor for 10 - 15 minutes by means of the cooperation of mechanical stirring and hydraulic circulation to dilute the hardness of the gasification wastewater to 200 - 400 mg / L.

[0034] In this embodiment, the antifoaming agent is selected as an organosilicon antifoaming agent, and the dosage is 10 - 50 ppm; the polyacrylamide is selected as an anionic type with a molecular weight of 8 million - 15 million, and the dosing concentration is 0.1% - 0.5%.

[0035] In this embodiment, step S2 specifically includes the following process: The mixed wastewater enters the inclined plate area of the horizontal flow sedimentation tank. The hydraulic retention time in the inclined plate area of the horizontal flow sedimentation tank is controlled at 1.5 - 2.5 hours. The angle between the inclined plate and the horizontal direction is set at 45° - 60°, and the inclined plate spacing is 80 - 120 mm. Remove suspended solids through sedimentation to reduce the suspended solid content in the wastewater to less than 50 mg / L; then enter the air flotation device. The air flotation device adopts the dissolved air flotation process, the dissolved air pressure is controlled at 0.3 - 0.5 MPa, and the air flotation time is 20 - 30 minutes. During this period, the slag scraping system in the air flotation device operates continuously, and the slag scraping plate slowly moves at a speed of 1 - 2 meters per minute to scrape and collect the floating slag layer in a timely manner, deeply remove the remaining suspended solids in the wastewater, and reduce the suspended solids in the effluent to less than 20 mg / L.

[0036] In this embodiment, after the wastewater enters the air flotation device, the air supply system is started, and the air is compressed to 0.3 - 0.5 MPa and then injected into the dissolved air tank, so that the air is fully dissolved in the water under high pressure to form dissolved air water. The dissolved air water is quickly decompressed and released through the release device, generating a large number of bubbles with diameters ranging from 20 to 50 μm, which are evenly dispersed in the wastewater. Residual suspended solids, colloidal particles, and some organic substances that are difficult to precipitate in the wastewater will attach to the surface of the bubbles due to surface activity and float to the water surface with the bubbles to form a scum layer. The air flotation time is controlled within 20 - 30 minutes.

[0037] In this embodiment, step S3 specifically includes the following processes: The wastewater flows into the anaerobic tank, anoxic tank, and aerobic tank. The temperature of the anaerobic tank is 30 - 35 °C, the pH value is 6.8 - 7.2, and the hydraulic retention time is 8 - 12 hours. Anaerobic bacteria are used to decompose macromolecular organic substances into small-molecular organic substances; the temperature of the anoxic tank is 25 - 30 °C, the pH value is 7.0 - 7.5, and the hydraulic retention time is 6 - 10 hours. Part of the ammonia nitrogen is removed through denitrification; the temperature of the aerobic tank is 20 - 25 °C, the pH value is 7.2 - 7.8, the dissolved oxygen concentration is 2 - 4 mg / L, and the hydraulic retention time is 12 - 18 hours. Aerobic microorganisms are used to oxidize and decompose organic substances and remove ammonia nitrogen to gradually remove ammonia nitrogen and COD. Then, through the sludge-water separation operation in the secondary sedimentation tank, the surface hydraulic load of the secondary sedimentation tank is 0.8 - 1.2 m 3 / (m 2 ·h), and purification is carried out to make the effluent COD less than 60 mg / L and the ammonia nitrogen 0 mg / L.

[0038] In this embodiment, step S4 specifically includes the following processes: The wastewater after reaching the purification standard enters the reclaimed water reuse device. The reclaimed water reuse device adopts the ultrafiltration - reverse osmosis double membrane filtration process. The pore size of the ultrafiltration membrane is 0.001 - 0.01 μm, and the operating pressure is 0.1 - 0.3 MPa. The molecular weight cut-off of the reverse osmosis membrane is 100 - 200 Da, and the operating pressure is 0.8 - 1.2 MPa. After treatment, reuse is achieved to realize the recycling of water resources.

[0039] Please refer to Figure 2 , the structural schematic diagram of the coal chemical wastewater comprehensive treatment system provided by the embodiment of the present invention. The system includes a wastewater conveying pipeline, a water distributor, an inclined plate area of a horizontal flow sedimentation tank, an air flotation device, a microbial ecological environment, a secondary sedimentation tank, and a reclaimed water reuse device. Among them,

[0040] The wastewater conveying pipeline is used to connect each wastewater generation source with the water distributor;

[0041] The water distributor is equipped with a chemical addition port for adding defoamer and polyacrylamide, and has a mixing structure inside;

[0042] The inclined plate area of the horizontal flow sedimentation tank removes suspended solids by setting the inclined plate angle and spacing;

[0043] Air flotation device, equipped with air supply and scraping system to remove suspended matter;

[0044] Microbial ecological environment, including anaerobic tanks, anoxic tanks, and aerobic tanks, used to remove ammonia nitrogen and COD;

[0045] Secondary sedimentation tank, used for mud and water separation;

[0046] Recycled water reuse device, used for wastewater reuse.

[0047] In this embodiment, the wastewater transport pipeline is made of high-strength and corrosion-resistant polyethylene material, which has excellent chemical stability and can withstand long-term erosion by a variety of complex chemical components in coal chemical wastewater, thereby ensuring the service life of the pipeline.

[0048] The water distributor is equipped with a dosing port, which is connected to a high-precision agent flow control system. The system has built-in advanced flow sensors that can monitor the dosing flow of defoamers and polyacrylamide in real time, and accurately control the dosage of agents based on preset parameters and real-time characteristics of wastewater, such as foam generation, wastewater turbidity, suspended matter content, etc. The mixing structure inside the water distributor adopts a coordinated approach of mechanical stirring and hydraulic circulation. Mechanical stirring is achieved through a stirring paddle installed inside the water distributor. The speed of the stirring paddle is controlled at 60-100r / min, which can effectively break the stratification of wastewater and fully mix different wastewaters and agents. The hydraulic circulation uses a specially designed water flow guide channel and the pressure difference between the inlet and outlet water to circulate the wastewater in the water distributor. The flow rate is 2-3 times the total volume of the wastewater / h, which further enhances the mixing effect and ensures the stability and efficiency of the subsequent treatment process.

[0049] The inclined plate area of ​​the horizontal flow sedimentation tank is made of engineering plastics with good anti-fouling properties, such as polyvinyl chloride (PVC) or high-density polyethylene (HDPE). This material has a smooth surface, is not easy to attach suspended matter, and has a certain mechanical strength to withstand the impact of water flow. The angle between the inclined plate and the horizontal direction is set to 45°-60°. This angle range can not only ensure that the suspended matter slides and settles smoothly on the inclined plate, but also make full use of the sedimentation tank space to improve the sedimentation efficiency; the spacing between the inclined plates is 80-120mm. The reasonable spacing design can avoid the blockage of suspended matter between the inclined plates, while ensuring the smooth passage of water, so that the suspended matter content in the wastewater is effectively reduced to below 50mg / L during the sedimentation process.

[0050] Air Flotation Device: It adopts the dissolved air flotation process and has a perfect air supply system. The air supply system consists of an air compressor, a gas storage tank, a dissolved air tank, and supporting pressure regulating valves, safety valves, etc. The air compressor compresses air to 0.3 - 0.5 MPa and then injects it into the dissolved air tank, enabling the air to be fully dissolved in water under high pressure to form dissolved air water. The dissolved air water is rapidly decompressed and released through a release device, generating a large number of tiny bubbles with a diameter usually between 20 - 50 μm, which are evenly dispersed in the wastewater. Residual suspended solids, colloidal particles, and some organic substances that are difficult to precipitate in the wastewater will attach to the surface of the bubbles due to surface activity and float to the water surface with the bubbles to form a scum layer. The air flotation device is also equipped with an efficient scum scraping system. The scum scraping plate moves slowly at a speed of 1 - 2 meters per minute to scrape and collect the scum layer in a timely manner. The air flotation time is controlled within 20 - 30 minutes, reducing the suspended solids in the effluent further to below 20 mg / L to ensure that the suspended solids are removed as much as possible before the wastewater enters the subsequent treatment unit.

[0051] Microbial Ecological Environment (Anaerobic Tank, Anoxic Tank, Aerobic Tank): The temperature of the anaerobic tank is controlled at 30 - 35 °C. This temperature range is suitable for the growth, reproduction, and metabolic activities of anaerobic bacteria. To maintain temperature stability, heat insulation materials can be wrapped around the outside of the tank body, and a temperature sensor and temperature control system can be installed to monitor and regulate the temperature in real time. The pH value is maintained at 6.8 - 7.2. Through an on-line pH monitor and an automatic acid-base dosing device, the acid-base environment in the tank is ensured to be stable, which is beneficial for anaerobic bacteria to decompose macromolecular organic substances into small-molecular organic substances and provide more easily degradable substrates for subsequent treatment. The hydraulic retention time is 8 - 12 hours to ensure that anaerobic bacteria have enough time to complete the metabolic process; the temperature of the anoxic tank is controlled at 25 - 30 °C. This temperature range conforms to the growth characteristics of denitrifying bacteria and helps them play the denitrification role efficiently to remove part of the ammonia nitrogen. The pH value is maintained at 7.0 - 7.5, and the accurate pH regulation system is also relied on to ensure a suitable environment. The hydraulic retention time is 6 - 10 hours to enable the denitrification process to proceed fully; the temperature of the aerobic tank is controlled at 20 - 25 °C, which is suitable for the growth of aerobic microorganisms. The installed aeration system and cooling device (if necessary) are used to jointly regulate the temperature. The pH value is maintained at 7.2 - 7.8, and the dissolved oxygen concentration is controlled at 2 - 4 mg / L. The aeration volume is accurately controlled through equipment such as a variable-frequency blower and a gas flowmeter of the aeration system to ensure that aerobic microorganisms further oxidize and decompose organic substances and remove ammonia nitrogen in a suitable dissolved oxygen environment. The hydraulic retention time is 12 - 18 hours to provide sufficient reaction time for aerobic treatment. At the same time, to maintain the activity of microorganisms, highly efficient microbial strains need to be inoculated regularly. According to the microbial growth cycle and the wastewater treatment load, nutrients such as nitrogen, phosphorus, and other trace elements are supplemented every 3 - 6 months to ensure the stable and efficient operation of the microbial ecosystem.

[0052] Secondary Sedimentation Tank The surface hydraulic load of the secondary sedimentation tank is controlled at 0.8 - 1.2 m 3 / (m2 ·h), through reasonable design of the tank structure, such as optimizing the inlet and outlet water methods, setting up flow guiding plates, etc., to achieve efficient separation of mud and water in the tank. A sludge scraping device is equipped at the bottom of the tank to regularly discharge the precipitated sludge to prevent sludge accumulation from affecting the separation effect. The sludge discharge frequency is determined according to the sludge generation amount, generally 1-2 times a day. To ensure the long-term stable operation of the mud-water separation equipment, regular maintenance is required, including checking the wear condition of the scraping plate, cleaning the blockages in the inlet and outlet pipes, etc. A comprehensive maintenance should be carried out at least once a month to ensure that the effluent quality meets the standards.

[0053] The reclaimed water reuse device adopts the ultrafiltration-reverse osmosis double-membrane filtration process. The ultrafiltration membrane is used as the pretreatment link, with a pore size of 0.001-0.01μm, which can effectively intercept tiny particles such as colloids, macromolecular organic matters, bacteria, and some viruses in the wastewater. The operating pressure is controlled at 0.1-0.3MPa. This pressure range can not only ensure the filtration efficiency of the ultrafiltration membrane but also avoid damage to the membrane caused by excessive pressure. The wastewater after ultrafiltration treatment enters the reverse osmosis unit. The reverse osmosis membrane has a rejection molecular weight of 100-200Da, which can further remove almost all remaining impurities such as dissolved salts, heavy metal ions, and small molecular organic matters in the water. The operating pressure is 0.8-1.2MPa to achieve deep purification of the wastewater. Pressure sensors are equipped before and after the ultrafiltration membrane and the reverse osmosis membrane to monitor the pressure difference on both sides of the membrane in real time, so as to promptly detect the blockage or damage of the membrane. Once the pressure difference exceeds the normal range, the automatic backwashing program can be started or an alarm can be given to prompt the operation and maintenance personnel to handle it; the reclaimed water after double-membrane filtration needs to be subjected to water quality testing. The testing indicators cover chemical oxygen demand (COD), ammonia nitrogen, total hardness, heavy metal content, total number of bacteria, turbidity, etc. All indicators need to meet the corresponding reclaimed water reuse standards. For example, the industrial water standard requires that COD is lower than 60mg / L, ammonia nitrogen is lower than 5mg / L, total hardness is lower than 450mg / L, heavy metal content meets the industry specifications, total number of bacteria is lower than 100CFU / mL, and turbidity is lower than 5NTU, etc. Only the water that meets the standards can be safely reused for cooling water, flushing water, etc. in the coal chemical production process, realizing the recycling of water resources, reducing the enterprise's water consumption cost, and improving the water resource utilization rate.

[0054] In order to enable those skilled in the art to better understand the present invention, the present invention will be further elaborated below in combination with specific embodiments.

[0055] Example 1

[0056] Take 100 L of coking wastewater, methanol gasification wastewater, and coal preparation wastewater respectively. Among them, the COD of coking wastewater is 4500 mg / L and the ammonia nitrogen is 60 mg / L; the hardness of methanol gasification wastewater is 1000 mg / L and the suspended solids are 500 mg / L; the turbidity of coal preparation wastewater is 800 NTU and the suspended solids are 400 mg / L. Through a high-strength corrosion-resistant polyethylene pipeline, it is transported to the water distributor at a flow rate of 1 m / s. Add 30 ppm of silicone defoamer and 0.3% anionic polyacrylamide (molecular weight 12 million) at the chemical addition port of the water distributor. After 15 minutes of mechanical stirring (rotation speed 80 r / min) and hydraulic circulation (flow rate 2.5 times the total volume of wastewater per hour), the hardness of methanol gasification wastewater is diluted to 300 mg / L. The mixed wastewater enters the inclined plate area of the horizontal flow sedimentation tank, with a hydraulic retention time of 2 hours, the included angle between the inclined plate and the horizontal direction is 50°, and the inclined plate spacing is 100 mm. The suspended solids in the effluent are reduced to 40 mg / L. Then it enters the air flotation device, with a dissolved air pressure of 0.4 MPa and an air flotation time of 25 minutes. The slag scraping plate cleans the floating slag at a speed of 1.5 meters per minute, and the suspended solids in the effluent are further reduced to 15 mg / L. The wastewater flows into the anaerobic tank, anoxic tank, and aerobic tank. Each tank strictly controls the temperature, pH value, and hydraulic retention time. The dissolved oxygen concentration in the aerobic tank is maintained at 3 mg / L. After sedimentation and separation in the secondary sedimentation tank (surface hydraulic load 1 m 3 / (m 2 ·h)), the COD of the effluent is 50 mg / L and the ammonia nitrogen is 0 mg / L. Finally, it enters the reclaimed water reuse device for ultrafiltration-reverse osmosis dual membrane filtration. The pore size of the ultrafiltration membrane is 0.005 μm, the operating pressure is 0.2 MPa, the rejection molecular weight of the reverse osmosis membrane is 150 Da, and the operating pressure is 1 MPa. All indicators of the treated reclaimed water meet the industrial water standard, the conductivity is lower than 50 μS / cm, and there are no visible impurities.

[0057] Example 2

[0058] Collect 120 L of each of the three kinds of wastewater from different sources. The COD of coking wastewater is 5000 mg / L, and the ammonia nitrogen is 70 mg / L; the hardness of methanol gasification wastewater is 1100 mg / L, and the suspended solids are 600 mg / L; the turbidity of coal preparation wastewater is 900 NTU, and the suspended solids are 500 mg / L. The wastewater is transported to the water distributor through pipelines at a pipeline flow rate of 0.8 m / s. Add 40 ppm of organosilicon defoamer and 0.4% anionic polyacrylamide (molecular weight 10 million) at the chemical dosing port of the water distributor, and mix for 20 minutes (mechanical stirring speed 70 r / min, hydraulic circulation flow rate 2 times the total volume of wastewater per hour). The hardness of the gasification wastewater is reduced to 250 mg / L. The hydraulic retention time in the inclined plate area of the horizontal flow sedimentation tank is 1.8 hours, the inclined plate angle is 55°, the spacing is 90 mm, and the suspended solids in the effluent are 35 mg / L. The dissolved air pressure of the air flotation device is 0.35 MPa, the air flotation time is 28 minutes, and the suspended solids in the effluent after scraping the slag are 12 mg / L. The subsequent anaerobic tank, anoxic tank, aerobic tank and secondary sedimentation tank are operated according to the standard process, and the effluent COD is 45 mg / L and the ammonia nitrogen is 0 mg / L. The ultrafiltration membrane pore size of the reclaimed water reuse device is 0.008 μm, the operating pressure is 0.15 MPa, the reverse osmosis membrane retention molecular weight is 180 Da, the operating pressure is 0.9 MPa, the reclaimed water quality is clear, and the chemical oxygen demand is lower than 30 mg / L, meeting the reuse requirements.

[0059] Example 3

[0060] Take a total of 150 L of equal amounts of the three kinds of wastewater. The COD of coking wastewater is 4200 mg / L, and the ammonia nitrogen is 55 mg / L; the hardness of methanol gasification wastewater is 900 mg / L, and the suspended solids are 450 mg / L; the turbidity of coal preparation wastewater is 750 NTU, and the suspended solids are 350 mg / L. Treat with the system of the present invention: Send water to the water distributor at a pipeline flow rate of 1.2 m / s, add 25 ppm of organosilicon defoamer and 0.2% anionic polyacrylamide (molecular weight 13 million), and mix for 12 minutes (mechanical stirring 90 r / min, hydraulic circulation 3 times per hour). The hardness of the gasification wastewater is diluted to 350 mg / L. The residence time in the inclined plate area of the horizontal flow sedimentation is 2.2 hours, the inclined plate angle is 48°, the spacing is 110 mm, and the suspended solids in the effluent are 45 mg / L. The dissolved air of the air flotation device is 0.45 MPa, the air flotation is 22 minutes, and the suspended solids after scraping the slag are 18 mg / L. The wastewater is treated by anaerobic, anoxic, aerobic tanks and secondary sedimentation tank, and the effluent COD is 55 mg / L and the ammonia nitrogen is 0 mg / L. In the reclaimed water reuse link, the ultrafiltration membrane is 0.003 μm, the pressure is 0.25 MPa, the reverse osmosis membrane retention molecular weight is 120 Da, the pressure is 1.1 MPa, and the heavy metal content in the treated water is lower than 0.1 mg / L, and it can be safely reused.

[0061] Example 4

[0062] Mix 200 L of three kinds of wastewater in proportion. Among them, the COD of coking wastewater is 4,800 mg / L and the ammonia nitrogen is 65 mg / L; the hardness of methanol gasification wastewater is 1,050 mg / L and the suspended solids are 550 mg / L; the turbidity of coal preparation wastewater is 850 NTU and the suspended solids are 480 mg / L. The wastewater is sent to the water distributor through a specific pipeline at a flow rate of 0.9 m / s. Add 35 ppm defoamer and 0.35% anionic polyacrylamide (molecular weight 11 million) at the dosing port, and mix evenly in 18 minutes (mechanical stirring at 85 r / min and hydraulic circulation at 2.8 times / h). The hardness of the gasification wastewater is reduced to 280 mg / L. The horizontal flow sedimentation inclined plate area has a residence time of 2 hours, an inclined plate angle of 52° and a spacing of 105 mm, and the suspended solids in the effluent are 42 mg / L. The air flotation dissolved air is 0.38 MPa, and the air flotation takes 26 minutes. After scraping the slag, it is 16 mg / L. For subsequent biological treatment and sludge-water separation, the COD of the effluent is 48 mg / L and the ammonia nitrogen is 0 mg / L. The reclaimed water reuse ultrafiltration has a pore size of 0.006 μm and an operating pressure of 0.18 MPa, and the reverse osmosis has a retention of 160 Da and an operating pressure of 0.85 MPa. The bacterial content of the reclaimed water is less than 100 CFU / mL, and the reuse is safe and reliable.

[0063] Through the implementation of the above solution, after mixing the coking wastewater, gasification wastewater, and coal preparation wastewater, the gasification fine slag in the gasification wastewater and the coal slime in the coal preparation wastewater are used to adsorb and remove the emulsified oil and macromolecular refractory organic matter in the comprehensive wastewater, improving the biodegradability and reducing the cost of advanced treatment of coking wastewater; using the high alkalinity of coking wastewater and the high hardness of gasification wastewater, partial precipitation is generated and then removed by coagulation and flocculation in the secondary sedimentation tank, reducing the cost of dispersant and hardening removal agents and the risk of subsequent equipment structure; through dilution, the COD and ammonia nitrogen indexes in the wastewater are reduced, the operation of the biochemical system is stabilized, and the degradation efficiency is improved; using the wastewater quality characteristics, the alkalinity is effectively used to remove the hardness, reducing the cost of hardening removal agents; the gasification fine slag and the coal slime in the coal preparation wastewater adsorb and remove the emulsified oil and macromolecular refractory organic matter in the wastewater, improving the biodegradability; reducing the investment in wastewater treatment facilities and equipment.

[0064] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art of this industry should understand that the present invention is not limited by the above embodiments. The above embodiments and the descriptions in the specification are only preferred examples of the present invention and are not used to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A comprehensive treatment method for coal chemical wastewater, characterized in that: The comprehensive treatment method for coal chemical wastewater comprises the following steps: S1. Coking wastewater, methanol gasification wastewater and coal preparation wastewater are transported to the same water distributor through the wastewater transport pipeline, defoaming agent and polyacrylamide are added to the water distributor dosing port, and mixed through the water distributor to dilute the hardness of the gasification wastewater; S2. The mixed wastewater enters the inclined plate area of ​​the horizontal flow sedimentation tank, where the suspended solids are removed, and then enters the flotation device, where the suspended solids remaining in the wastewater are deeply removed by the flotation principle; S3, wastewater flows into anaerobic tank, anoxic tank and aerobic tank to gradually remove ammonia nitrogen and COD, and then is purified by mud-water separation operation in the secondary sedimentation tank; S4. The wastewater that has been purified and meets the standards enters the reclaimed water reuse device and is reused after being treated to achieve the recycling of water resources.

2. A method for comprehensive treatment of coal chemical wastewater according to claim 1, characterized in that: Step S1 specifically includes the following process: coking wastewater, methanol gasification wastewater and coal preparation wastewater are transported to the same water distributor through a wastewater transport pipeline, the flow rate of the wastewater transport pipeline is 0.5-1.5m / s, a defoaming agent is accurately added to the dosing port of the water distributor to eliminate foam, polyacrylamide is added for coagulation and flocculation, and mechanical stirring and hydraulic circulation are used to coordinate the mixing through the water distributor for 10-15 minutes to dilute the hardness of the gasification wastewater to 200-400mg / L.

3. A method for comprehensive treatment of coal chemical wastewater according to claim 2, characterized in that: The defoamer is an organic silicon defoamer with a dosage of 10-50ppm; the polyacrylamide is an anionic type with a molecular weight of 8-15 million and a dosage concentration of 0.1%-0.5%.

4. A method for comprehensive treatment of coal chemical wastewater according to claim 1, characterized in that: Step S2 specifically includes the following processes: the mixed wastewater enters the inclined plate area of ​​the horizontal flow sedimentation tank, the hydraulic retention time of the inclined plate area of ​​the horizontal flow sedimentation tank is controlled at 1.5-2.5 hours, the angle between the inclined plate and the horizontal direction is set to 45°-60°, the inclined plate spacing is 80-120mm, and the suspended matter is removed by sedimentation, so that the suspended matter content in the wastewater is reduced to below 50mg / L; then enters the flotation device, the flotation device adopts a dissolved air flotation process, the dissolved air pressure is controlled at 0.3-0.5MPa, and the flotation time is 20-30 minutes. During this period, the scraping system in the flotation device continues to operate, and the scraping plate moves slowly at a speed of 1-2 meters per minute to scrape and collect the scum layer in time, deeply remove the suspended matter remaining in the wastewater, and reduce the suspended matter in the effluent to below 20mg / L.

5. A method for comprehensive treatment of coal chemical wastewater according to claim 4, characterized in that: When the wastewater enters the flotation device, the air supply system is started, and the air is compressed to 0.3-0.5MPa and then injected into the dissolved air tank, so that the air is fully dissolved in the water under high pressure to form dissolved air water. The dissolved air water is quickly released by the releaser under reduced pressure, generating a large number of bubbles with a diameter of 20-50μm, which are evenly dispersed in the wastewater. The residual suspended matter, colloidal particles and some organic matter that is difficult to precipitate in the wastewater will adhere to the surface of the bubbles due to surface activity, and form a scum layer as the bubbles float to the water surface. The flotation time is controlled at 20-30 minutes.

6. A method for comprehensive treatment of coal chemical wastewater according to claim 1, characterized in that: Step S3 specifically includes the following processes: wastewater flows into an anaerobic tank, an anoxic tank, and an aerobic tank. The temperature of the anaerobic tank is 30-35°C, the pH value is 6.8-7.2, and the hydraulic retention time is 8-12 hours. Anaerobic bacteria are used to decompose large molecular organic matter into small molecular organic matter; the temperature of the anoxic tank is 25-30°C, the pH value is 7.0-7.5, and the hydraulic retention time is 6-10 hours. Part of the ammonia nitrogen is removed by denitrification; the temperature of the aerobic tank is 20-25°C, the pH value is 7.2-7.8, the dissolved oxygen concentration is 2-4 mg / L, and the hydraulic retention time is 12-18 hours. Aerobic microorganisms are used to oxidize and decompose organic matter and remove ammonia nitrogen, so as to gradually remove ammonia nitrogen and COD, and then the wastewater is separated in the secondary sedimentation tank. The hydraulic load on the surface of the secondary sedimentation tank is 0.8-1.2m 3 / (m 2 h), and purify the effluent to make the COD less than 60mg / L and the ammonia nitrogen to 0mg / L.

7. A method for comprehensive treatment of coal chemical wastewater according to claim 1, characterized in that: Step S4 specifically includes the following process: The purified wastewater that meets the standards enters the reclaimed water reuse device, which adopts the ultrafiltration-reverse osmosis double membrane filtration process. The pore size of the ultrafiltration membrane is 0.001-0.01μm, the operating pressure is 0.1-0.3MPa, the reverse osmosis membrane has a molecular weight cutoff of 100-200Da, and the operating pressure is 0.8-1.2MPa. After treatment, it can be reused to achieve the recycling of water resources.

8. A comprehensive treatment system for coal chemical wastewater, characterized in that: The coal chemical wastewater comprehensive treatment system includes a wastewater delivery pipeline, a water distributor, a horizontal flow sedimentation tank inclined plate area, an air flotation device, a microbial ecological environment, a secondary sedimentation tank and a reclaimed water reuse device, wherein: Wastewater delivery pipeline, used to connect various wastewater generation sources with water distributors; The water distributor is equipped with a dosing port for adding defoamer and polyacrylamide, and has a mixing structure inside; The inclined plate area of ​​the horizontal flow sedimentation tank removes suspended matter by setting the angle and spacing of the inclined plates; Air flotation device, equipped with air supply and scraping system to remove suspended matter; Microbial ecological environment, including anaerobic tanks, anoxic tanks, and aerobic tanks, used to remove ammonia nitrogen and COD; Secondary sedimentation tank, used for mud and water separation; Recycled water reuse device, used for wastewater reuse.

Images