A system for treating oil-containing wastewater in a thermal power plant

Abstract

The utility model belongs to the thermal power plant oily wastewater treatment technical field, concretely relates to a kind of thermal power plant oily wastewater treatment system.The processing system described in the utility model includes plant area collection pool, regulating pool device, cyclone dissolved air flotation device, modified active filter and external drainage pool connected in sequence;The utility model solves the problems of high processing cost, large occupation, many supporting equipment and long process flow in the existing traditional regulating pool, oil separation tank, air flotation tank and coagulation sedimentation tank system;The oil content of the water outlet of the processing system of the utility model is stably reduced to less than 10mg / L, meets the oily wastewater discharge index of thermal power plant in IFC thermal power plant occupational health and safety guideline standard, reduces the operation cost by two-thirds, reduces the occupation by one-half, does not need sludge disposal device, and recovers waste oil.

Description

Technical Field

[0001] This utility model belongs to the technical field of oily wastewater treatment in thermal power plants, and specifically relates to an oily wastewater treatment system for thermal power plants. Background Technology

[0002] During operation, thermal power plants generate oily wastewater. Direct discharge of this wastewater will pollute the surrounding environment. Therefore, it is necessary to treat the oily wastewater to meet the standards before discharge or use it for irrigation of greening in the park. The oily wastewater includes: (1) Machine room drainage: the main pollutants are lubricating oil and dust carried out by the equipment flushing water; (2) Engine area drainage: the main pollutants are lubricating oil and dust carried out by the turbine, pump and other flushing water; (3) Auxiliary system area drainage: the main pollutants are rust residue flushed out of the pipeline by the power plant circulating water and fuel oil leaked from the equipment; (4) Workshop and cleaning room drainage: the main pollutants are oil and suspended solids in the cleaning water; (5) Oil tank area drainage: the main pollutants are fuel oil and bottom slag carried out by the drainage at the bottom of the oil tank; (6) Fuel processing area drainage: the main pollutants are fuel oil and suspended solids leaked from the tank truck during transportation carried out by the surface water; (7) Transformer area drainage: the main pollutants are oil leaked into the underground pool during transformer maintenance. Rainfall washes pollutants onto the ground and into the equalization tank, resulting in significant differences in treatment volume between the dry and rainy seasons. During the rainy season, when rainfall is heavy, the oily wastewater is characterized by a large flow rate and relatively good water quality; conversely, during the dry season, when rainfall is low, the flow rate is small and the water quality is poor. The stream with the highest pollutant concentration originates from the bottom drainage of the oil tank area. Due to the unpredictable nature of the oil supply to the thermal power plant—which can range from crude oil to fuel oil to residual oil—the water content in the oil fluctuates. The tank area discharges water irregularly, resulting in large instantaneous volumes and high pollutant concentrations. Therefore, the oily wastewater from thermal power plants presents challenges due to significant fluctuations in both water quality and volume, making maintenance difficult.

[0003] Traditional oil removal systems face problems such as unstable dosing control, waste of chemicals, or substandard water quality when water quality fluctuates. Therefore, how to ensure the stability of the effluent quality of wastewater from thermal power plants under different influent water quality and quantity fluctuations is a technical problem that urgently needs to be solved. Utility Model Content

[0004] To overcome the shortcomings of the prior art, this utility model provides an oily wastewater treatment system for thermal power plants. This system effectively removes oil and suspended solids from oily wastewater discharged from different areas of the power plant, even when the incoming water fluctuates, reducing the oil content to below 10 mg / L, thus meeting the requirements for irrigation or discharge into the plant's green spaces.

[0005] To achieve the above objectives, the technical solution adopted by this utility model is as follows: The first aspect of this utility model provides a system for treating oily wastewater from a thermal power plant, the system flow diagram of which is shown below.Figure 1 As shown, the treatment system includes a plant collection tank, an equalization tank, a cyclone dissolved air flotation device, a modified activated filter media filter, and an external drainage tank connected in sequence.

[0006] Furthermore, the external drainage tank is equipped with a backwash pump, which is used to pump water from the external drainage tank to the modified activated filter for backwashing, and the backwashed water is sent to the equalization tank.

[0007] Furthermore, the equalization tank device includes an equalization tank, a submersible pump, a first sludge pump, a second sludge pump, a sludge tank, and an incinerator located in the equalization tank. The submersible pump is used to pump the effluent from the equalization tank to the cyclone dissolved air flotation device. The first sludge pump is used to pump the sludge floating in the equalization tank to the sludge tank. The second sludge pump is used to pump the sludge in the sludge tank to the incinerator for incineration.

[0008] Furthermore, the equalization tank consists of a first compartment, a second compartment, and a third compartment. The first compartment is an oil collection area, which receives oily wastewater and sludge discharged from the dissolved air flotation device. Most of the sludge in the wastewater floats to the oil collection compartment. The first sludge pump, controlled by an oil-water level gauge, periodically pumps the sludge to the sludge tank. The clear liquid flows from the bottom of the oil collection area to the second compartment, which is a buffer zone. Wastewater overflows from the top of the buffer zone to the third compartment, which is an effluent area. The wastewater from the effluent area is pumped to the vortex dissolved air flotation device by a submersible pump. After preliminary separation in the equalization tank, most of the floating oil is removed.

[0009] Furthermore, the cyclone dissolved air flotation device includes a cyclone dissolved air flotation unit, an air compressor, and an exhaust gas treatment device. The air compressor generates air that enters the cyclone dissolved air flotation unit to treat the wastewater using cyclone dissolved air flotation. The exhaust gas from the cyclone dissolved air flotation unit enters the exhaust gas treatment device. The sludge and oil generated by the cyclone dissolved air flotation unit are sent to an equalization tank. The effluent from the cyclone dissolved air flotation unit enters a modified activated filter.

[0010] Furthermore, the cyclone dissolved air flotation equipment includes a flotation tank, a dissolved air pump, and a dissolved air tank. The dissolved air pump pressurizes the return wastewater in the flotation tank to dissolve air, and then the water enters the dissolved air tank. Suspended solids and sludge in the wastewater are removed through cyclone and flotation. Sludge is periodically discharged from the upper part of the flotation tank and sent to the oil collection area of ​​the equalization tank. The effluent enters the modified activated filter media.

[0011] A second aspect of this utility model provides a process for treating oily wastewater from thermal power plants using the above-described treatment system, the process comprising the following steps: (1) Oily wastewater flows by gravity from the collection pool in the plant area to the equalization pool, and the floating oil in the upper part of the equalization pool is pumped away; (2) The clear liquid in the middle of the equalization tank is pumped to the vortex dissolved air flotation device to remove oil and suspended solids; (3) The effluent from the air flotation enters the modified activated filter to remove oil and suspended solids; (4) Emissions meet standards.

[0012] Further, the specific process of step (1) is as follows: oily wastewater from different sources is collected and mixed in the plant collection pool, and then flows together to the equalization pool. The equalization pool is divided into three compartments. The first compartment is the oil collection area, which receives oily wastewater and sludge discharged from the dissolved air flotation device. Sludge and some of the sludge in the oily wastewater float to the oil collection compartment. The oil pump is controlled by the oil-water level gauge to periodically pump the sludge to the sludge tank and then to the incinerator for treatment. The clear liquid flows from the bottom of the oil collection area to the second compartment, which is a buffer zone. Wastewater overflows from the top of the buffer zone to the third compartment, which is the effluent area. The wastewater in the effluent area is pumped to the vortex dissolved air flotation device by the pump.

[0013] Further, the specific process of step (2) is as follows: after the wastewater from the effluent area of ​​the equalization tank enters the vortex dissolved air flotation device, it enters the flotation tank. The effluent from the flotation tank is returned, and the returned wastewater is pressurized by the dissolved air pump to dissolve the gas. The dissolved air water enters the dissolved air tank, and the gas-water mixture in the dissolved air tank enters the flotation tank. The suspended solids and sludge in the wastewater are removed by the action of vortex and flotation. The sludge is periodically discharged from the upper part of the flotation tank and sent to the oil collection area of ​​the equalization tank. The effluent enters the modified activated filter media filter.

[0014] Furthermore, the air source for the vortex dissolved air flotation device is compressed air, and the waste gas is discharged into a waste gas treatment device for unified treatment.

[0015] Further, the specific process of step (3) is as follows: the effluent from the air flotation enters the modified activated filter through the filter lift pump, and the sludge and suspended solids are reduced to meet the discharge indicators through the interception of the filter, and then discharged to the external drainage pool for reuse or external discharge.

[0016] Furthermore, the modified activated filter media is backwashed periodically with water from the external drainage tank once a day for 1 minute each time. The backwash water contains oil and suspended solids and is pumped back to the equalization tank via a backwash pump.

[0017] Furthermore, the modified activated filter material is a quartz sand filter material with a SiO2 content > 99.9%.

[0018] Compared with the prior art, the beneficial effects of this utility model are: This invention provides a technically feasible and economically reasonable oil removal system for oily wastewater from thermal power plants. It effectively removes sludge and suspended solids from the wastewater, maintaining the oil content in the effluent below 10 mg / L. This system requires no chemical additives, allows for the recycling of sludge, reduces oily sludge production, avoids secondary pollution, and eliminates the need for a separate sludge treatment device. The compressed air consumption of the cyclone dissolved air flotation device has a gas-liquid ratio of only 10%, reducing air compressor energy consumption and significantly lowering operating costs. Attached Figure Description

[0019] Figure 1 This is a flow chart of the oily wastewater treatment system for thermal power plants according to this utility model.

[0020] Figure 2 This is a flowchart of the oily wastewater treatment system of a thermal power plant in the embodiment.

[0021] Among them, 1 is the plant area collection pool, 21 is the equalization pool, 22 is the submersible pump, 23 is the first sludge pump, 24 is the second sludge pump, 25 is the sludge tank, 26 is the incinerator, 31 is the cyclone dissolved air flotation equipment, 311 is the flotation tank, 312 is the dissolved air pump, 313 is the dissolved air tank, 32 is the air compressor, 33 is the waste gas treatment device, 4 is the modified activated filter, 5 is the external drainage pool, and 6 is the backwash pump. Detailed Implementation

[0022] The specific embodiments of this utility model are further described below. It should be noted that these descriptions are for the purpose of aiding understanding of this utility model, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of this utility model described below can be combined with each other as long as they do not conflict with each other.

[0023] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the experimental materials used in the following embodiments are all available through conventional commercial channels.

[0024] Example: Oily wastewater treatment at a 120MW dual-fuel power plant abroad The oily wastewater treatment system for thermal power plants according to this utility model is used for treatment. The system flow diagram is as follows: Figure 2 As shown, the oily wastewater treatment system of the thermal power plant consists of the following components: It includes a plant area collection tank 1, an equalization tank device 2, a cyclone dissolved air flotation device 3, a modified activated filter media filter 4, and an external drainage tank 5, which are connected in sequence.

[0025] The equalization tank device 2 includes an equalization tank 21, a submersible pump 22, a first sludge pump 23, a second sludge pump 24, a sludge tank 25, and an incinerator 26 located in the equalization tank 21. The submersible pump 22 is used to pump the effluent from the equalization tank 21 to the cyclone dissolved air flotation device 3. The first sludge pump 23 is used to pump the sludge that floats in the equalization tank 21 to the sludge tank 25. The second sludge pump 24 is used to pump the sludge in the sludge tank 25 to the incinerator for incineration 26.

[0026] The external drainage tank 5 is equipped with a backwash pump 6, which is used to pump water from the external drainage tank 5 to the modified activated filter media 4 for backwashing. The backwashed water is then sent to the equalization tank 21.

[0027] The equalization tank 21 consists of a first compartment, a second compartment, and a third compartment. The first compartment is an oil collection area, which receives oily wastewater and sludge discharged from the dissolved air flotation device 3. Most of the sludge in the oily wastewater floats to the oil collection compartment. The first sludge pump 23, controlled by the oil-water level gauge, periodically pumps the sludge to the sludge tank 25. The clear liquid flows from the bottom of the oil collection area to the second compartment, which is a buffer zone. The wastewater overflows from the top of the buffer zone to the third compartment, which is the effluent area. The wastewater in the effluent area is pumped to the vortex dissolved air flotation device 3 by the submersible pump 22. After preliminary separation in the equalization tank 21, most of the floating oil is removed.

[0028] The cyclone dissolved air flotation device 3 includes a cyclone dissolved air flotation unit 31, an air compressor 32, and a waste gas treatment device 33. The air compressor 32 generates air that enters the cyclone dissolved air flotation unit 31, and the waste gas in the cyclone dissolved air flotation unit 31 enters the waste gas treatment device 33. The cyclone dissolved air flotation unit 31 includes a flotation tank 311, a dissolved air pump 312, and a dissolved air tank 313. The dissolved air pump 312 pressurizes the return wastewater in the flotation tank 311 to dissolve air, and then the water enters the dissolved air tank 313. The suspended solids and sludge in the wastewater are removed through the cyclone and flotation action. The sludge in the upper part of the flotation tank 311 is periodically discharged to the oil collection area of ​​the equalization tank 21, and the effluent enters the modified activated filter 4.

[0029] The steps of the oily wastewater treatment process from the thermal power plant are as follows: Section 1: Oily wastewater from various areas within the plant is collected and mixed in the plant collection pool 1 before being discharged into the equalization pool 21. The equalization pool 21 is designed to have a retention time of 8 hours. In the equalization pool 21, the floating oil in the wastewater and the sludge discharged from the flotation tank are pumped to the sludge tank 25 by the first sludge pump 23. The sludge in the sludge tank 25 is then pumped to the incinerator 26 for incineration by the second sludge pump 24. The suspended solids in the water settle to the bottom of the equalization pool 21. During the dry season when there is no rainfall, the bottom of the pool is cleaned during maintenance. The effluent from the equalization pool 21 is pumped to the flotation tank 311 by the submersible pump 22 in the effluent area. The oily wastewater undergoes preliminary removal of floating oil and large suspended solids with fast settling speed in the equalization pool 21.

[0030] Section Two: The effluent from the equalization tank 21 is pumped into the dissolved air flotation tank 311 via submersible pump 22. The dissolved air flotation process uses swirling dissolved air flotation. The incoming water enters the flotation tank 311 tangentially, creating a swirling effect that accelerates the collision, aggregation, and floating of air bubbles and pollutants. The residence time is 5 minutes. The flotation tank 311 uses an external air supply. A portion of the effluent from the flotation tank 311 is mixed with compressed air via dissolved air pump 312 and then enters the dissolved air tank 313. The compressed air is generated by air compressor 32, and the gas-liquid mixture enters the dissolved air tank. After 313, the dissolved air water mixes with the influent of the flotation tank and enters the flotation tank 311. At this time, the dissolved air bubbles in the water are released through decompression, forming dense bubbles in the water. These bubbles are accelerated by swirling flow, collide with pollutants, aggregate, and float to the surface, carrying away oil and suspended solids in the wastewater. The sludge and oil in the flotation tank 311 are discharged from the top and returned to the equalization tank 21. The waste gas in the flotation tank 311 is drawn to the waste gas treatment device 33. The oil content of the effluent from the flotation tank is less than 50 mg / L, and the suspended solids are less than 30 mg / L, which meets the water quality requirements for entering the filter.

[0031] Section 3: The effluent from the air flotation enters the modified activated filter 4, with a residence time of 20 minutes. Through the interception of the modified activated filter media, the oil content in the water is reduced to below 10 mg / L, and the suspended solids are reduced to below 10 mg / L. The filter effluent is discharged into the external drainage tank 5. After passing the online analysis, it is either discharged or reused. The water in the external drainage tank 5 can be backwashed by the backwash pump 6 to the modified activated filter 4. The filter media is high-purity quartz sand with a SiO2 content > 99.9%. The filter media is modified with superhydrophilic oil-repellent properties, making it less prone to clogging. Backwashing does not require chemical agents. Backwashing is performed once a day for 1 minute. The backwash effluent containing sludge and suspended solids is returned to the equalization tank 21.

[0032] The processing effects of each processing unit in the above process are shown in Table 1 below.

[0033] Table 1 Collection pool 2000mg / L 500mg / L 6~9 equalization tank 1000mg / L 300mg / L 6~9 Swirl dissolved air flotation 50mg / L 30mg / L 6~9 Modified activated filter media 10mg / L 10mg / L 6~9 Drainage index 10mg / L 10mg / L 6~9 As can be seen, the oil content in the effluent from the above system is reduced to below 10 mg / L, the suspended solids are reduced to below 10 mg / L, and it is a purely physical treatment system. Therefore, the pH of the water quality remains unchanged, meeting the discharge requirements.

[0034] The above system is fully automated through DCS and connected to the plant's control room, requiring only two personnel for regular inspections.

[0035] The overall operating cost of the above system is two-thirds less than that of traditional chemical flotation, equipment investment is reduced by one-third, and equipment footprint is reduced by half.

[0036] The embodiments of this utility model have been described in detail above, but this utility model is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of this utility model, and these variations still fall within the protection scope of this utility model.

Claims

1. A system for treating oil-containing wastewater from a thermal power plant, characterized in that The treatment system includes a plant collection tank (1), an equalization tank (2), a vortex dissolved air flotation device (3), a modified activated filter (4), and an external drainage tank (5) connected in sequence. The regulating tank device (2) includes a regulating tank (21), a submersible pump (22), a first sludge pump (23), a second sludge pump (24), a sludge tank (25), and an incinerator (26) located in the regulating tank. The submersible pump (22) is used to pump the effluent from the regulating tank (21) to the vortex dissolved air flotation device (3). The first sludge pump (23) is used to pump the sludge floating in the regulating tank (21) to the sludge tank (25). The second sludge pump (24) is used to pump the sludge in the sludge tank (25) to the incinerator (26) for incineration.

2. A system for treating oily wastewater from a thermal power plant according to claim 1, characterized in that, The external drainage tank (5) is equipped with a backwash pump (6), which is used to pump the water in the external drainage tank (5) to the modified activated filter (4) for backwashing, and the backwashed water is sent to the regulating tank (21).

3. A system for treating oily wastewater from a thermal power plant according to claim 1, characterized in that, The regulating tank (21) consists of a first compartment, a second compartment, and a third compartment. The first compartment is an oil collection area, which receives oily wastewater and sludge discharged from the dissolved air flotation device (3). Most of the sludge in the oily wastewater floats to the oil collection compartment. The first sludge pump (23) is controlled by the oil-water level gauge to periodically pump the sludge to the sludge tank (25). The clear liquid flows from the bottom of the oil collection area to the second compartment, which is a buffer zone. The wastewater overflows from the top of the buffer zone to the third compartment, which is the effluent area. The wastewater in the effluent area is pumped to the vortex dissolved air flotation device (3) by the submersible pump (22).

4. The system for treating oily wastewater of a thermal power plant according to claim 1, characterized in that, The cyclone dissolved air flotation device (3) includes a cyclone dissolved air flotation equipment (31), an air compressor (32), and a waste gas treatment device (33). The air compressor (32) generates air that enters the cyclone dissolved air flotation equipment (31) to treat the wastewater by cyclone dissolved air flotation. The waste gas in the cyclone dissolved air flotation equipment (31) enters the waste gas treatment device (33). The sludge and oil generated by the cyclone dissolved air flotation equipment (31) are sent to the equalization tank (21). The effluent from the cyclone dissolved air flotation equipment (31) enters the modified activated filter (4).

5. The oily wastewater treatment system for thermal power plants according to claim 4, characterized in that, The vortex dissolved air flotation device (31) includes a flotation tank (311), a dissolved air pump (312), and a dissolved air tank (313). The dissolved air pump (312) pressurizes the return wastewater in the flotation tank (311) to dissolve air, and then enters the dissolved air tank (313). The suspended solids and sludge in the wastewater are removed by the vortex and flotation action.

6. The system for treating oily wastewater of a thermal power plant according to claim 1, characterized in that, The modified active filter media in the modified active filter (4) is quartz sand filter media with SiO2 content > 99.9%.

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