Power Plant Oily Wastewater Purification: Source Analysis and Treatment Solutions
Main sources of oily wastewater in power plants
Fuel transportation:
In the fuel transportation links of a power plant, including the diesel engine room, oil unloading areas, and gasoline and engine oil handling areas, oily wastewater is often generated. These locations throughout the thermal power plant may involve the use of engine oil and diesel, leading to the formation of oily wastewater.
Boiler feedwater system:
The boiler feedwater system is responsible for delivering treated water through pipes to the boiler to generate steam. If the system uses mechanized treatment devices, oil pollutants may be generated during equipment operation. These pollutants may enter the boiler interior with the pipes, contaminating the boiler walls and pipe inner surfaces, eventually forming oily wastewater.
Power plant dust removers:
Power plant dust removal devices use dust removal technology to remove dust and pollutants from flue gas, reducing atmospheric pollutant emissions. However, during dust removal, if washing liquid is used to clean the equipment, oil pollutants in the washing liquid may mix into the oily wastewater.
Desulfurization and denitrification equipment:
Desulfurization and denitrification equipment removes sulfur dioxide and nitrogen oxides from flue gas through chemical reactions, reducing atmospheric pollutant emissions. But in this process, the absorbents used contact and dissolve the soot and pollutants in the flue gas, generating oily wastewater.
Equipment cleaning and maintenance:
During the regular cleaning and maintenance of power plant equipment, especially devices that directly contact oil, such as oil tanks and oil pumps, oily wastewater may be generated. This wastewater often contains high concentrations of grease and other harmful components.
Oil depot areas, step-up substations and turbine rooms:
The oil depot area, step-up substation and turbine room are the main locations for oil storage, transfer and use in the power plant, and are therefore important sources of oily wastewater. In these areas, equipment leakage or operational errors can lead to the generation of oily wastewater.
In summary, the causes of power plant oily wastewater are diverse, mainly involving fuel transportation, boiler feedwater systems, power plant dust removal devices, desulfurization and denitrification equipment, equipment cleaning and maintenance, and oil depot areas, step-up substations and turbine rooms. If this wastewater is discharged directly without proper treatment, it will cause great harm to the ecological environment. Therefore, power plants must take effective measures to purify and reuse this oily wastewater to reduce its environmental impact.
Difficulties in treating power plant oily wastewater
The purification challenges of power plant oily wastewater are mainly reflected in the following aspects:
Difficulty of oil-water separation: The oil in oily wastewater usually exists in an emulsified state, with small droplet size and high stability, making oil-water separation difficult by simple physical methods. The oil components in oily wastewater from different sources are complex and diverse - mineral oil, vegetable oil, animal oil, etc. - differing in chemical properties, density and viscosity, which brings challenges to treatment.
Large water quality fluctuations: The volume and quality of oily wastewater fluctuate considerably, affected by production processes and operating conditions, and the treatment process must adapt to these changes. Water quality instability may cause unstable operation of treatment equipment and reduce treatment efficiency.
High technical requirements: To achieve efficient and environmentally friendly oily wastewater treatment, advanced treatment technologies and equipment are required.
These technologies and equipment often place high demands on the skills and experience of operators, increasing treatment difficulty.
High treatment cost: The cost of treating oily wastewater is usually high, including equipment investment, operating expenses and energy consumption.
Efficient treatment technology often means higher investment and operating costs, putting pressure on the economic operation of the power plant.
Strict environmental requirements: With increasingly strict environmental regulations and rising public environmental awareness, higher requirements have been placed on the discharge standards for oily wastewater. Power plants need to adopt more advanced and efficient wastewater treatment processes and technologies to ensure wastewater discharge complies with national and local environmental standards.
Complex oil components and high concentration: The oil components in oily wastewater are complex, including many different types of grease and organics, making treatment difficult. Meanwhile, some oily wastewater has a high oil concentration, which increases treatment difficulty and cost.
To address the above difficulties, power plants need to take comprehensive treatment measures when treating oily wastewater, including pretreatment, oil-water separation, deep treatment and other stages. At the same time, source control must be strengthened to reduce wastewater generation and discharge, lowering treatment difficulty and cost. In addition, power plants need to pay attention to the development of new technologies and processes, continuously improving the treatment efficiency and environmental performance of oily wastewater treatment.
Conventional treatment technologies
Disadvantages of conventional technologies
Insufficient treatment efficiency:
Conventional oily wastewater treatment processes, such as gravity separation and coarse granulation, often perform poorly in treating high-concentration oily wastewater. For example, gravity separation requires a long time for oil-water separation, and the coarse granulation method performs poorly in treating emulsified oily wastewater containing surfactants, with effluent oil content possibly above 10 mg/L.
High resource consumption:
Some conventional processes, such as electrocoagulation, although small in footprint and simple to operate, have problems such as large anode metal consumption, the need for large amounts of salts as auxiliary chemicals, and high power consumption, resulting in relatively high treatment costs.
Chemical treatment methods can quickly change the properties of substances in oily sludge and achieve rapid separation, but the use and disposal of chemical reagents may involve special safety and environmental issues, and also increase treatment costs.
Environmental impact:
Conventional processes may produce secondary pollution during treatment. For example, if coagulants are added in mechanical separation methods, oily sludge will be produced; if this sludge is not properly handled, it may pollute the environment.
Some processes, such as pyrolysis, require high energy consumption and may produce gas emissions and residues, posing potential environmental risks.
Operational complexity:
Some conventional processes, such as electrochemical separation technology, have high requirements for electrode materials and voltage selection, requiring precise operation and maintenance, which increases operational difficulty and cost.
Limited scope of application:
Some conventional processes may only be suitable for specific types of oily wastewater; for example, electrocoagulation is mainly suitable for secondary treatment after chemical flocculation of cooling lubricants in the machining industry, and may not work well for other types of oily wastewater.
Long treatment cycle:
Some conventional processes, such as salting-out, have slow coagulation and sedimentation separation generally requiring more than 24 hours, resulting in long treatment cycles that are unfavorable for rapidly responding to water quality changes.
Large footprint:
When treating large-scale oily wastewater, conventional processes often require a large footprint for treatment equipment, increasing land resource consumption.
New process
The cyclonic dissolved air flotation developed by Shenzhen SINOKLE Company is a new generation of green, highly efficient vertical-tank flotation equipment. The equipment integrates cyclonic centrifugal separation, ultra-fine bubble generation and dissolved air flotation technologies, and through the synergy of multiple technologies achieves rapid and efficient separation of dirty oil, emulsified oil and suspended solids from wastewater.
Pretreatment process scheme for oil tank area water draw-off in refineries
Technical features:
Purely physical separation technology, stable and reliable, with high oil removal efficiency (over 95%)
Chemical-free, purely physical demulsification and oil removal; recovered oil goes directly back to the crude oil tank for reuse, with no secondary
pollution, no oily sludge (hazardous waste) generated, solving environmental problems while creating economic
benefits
Short process flow, compact equipment structure, small footprint,
skid-mounted, automated, easy operation and maintenance, short construction period, can be implemented online
Strong shock resistance, stable operation, can withstand large water quality fluctuations
Oily wastewater treatment process scheme for light oil depot water draw-off, washing water, pipeline leakage, etc.
Technical features:
Strong shock resistance, high efficiency, stable effluent, completely solving oil depot waste
water discharge problems
Short process flow, mainly physical methods, stable performance, low oily sludge
output, environmentally friendly technology
Fully automated enclosed operation, small footprint, less labor and maintenance,
easy operation
Multiple domestically leading patented technologies, technically advanced
Heavy oil depot oily wastewater treatment process scheme
Technical features:
Purely physical separation technology, stable and reliable, with high oil removal efficiency;
Reliable and stable process, compact equipment structure, small footprint;
Equipment operates fully enclosed, with no exhaust gas leakage;
Skid-mounted, automated, easy operation and maintenance, short construction period, can be implemented online;
Strong shock resistance, stable operation, can withstand large water quality fluctuations.
Light oil depot oily wastewater treatment and discharge process
Technical features:
Strong shock resistance, high efficiency, stable effluent, completely solving oil depot wastewater discharge problems
Short process flow, mainly physical methods, stable performance, low oily sludge, environmentally
friendly technology
CDOF Multi-catalytic oxidation, fast reaction rate, short residence time (<15 min),
skid-mounted, small footprint (1/5 of conventional)
Fully automated enclosed operation, small footprint, less labor and maintenance, easy operation
Multiple domestically leading patented technologies, technically advanced
Heavy oil depot oily wastewater treatment and discharge process
Technical features:
Strong shock resistance, high efficiency, stable effluent, completely solving oil depot wastewater discharge problems
Short process flow, mainly physical methods, stable performance, low oily sludge, environmentally
friendly technology
CDOF Multi-catalytic oxidation, fast reaction rate, short residence time (<15 min),
skid-mounted, small footprint (1/5 of conventional)
Fully automated enclosed operation, small footprint, less labor and maintenance, easy operation
Multiple domestically leading patented technologies, technically advanced
Application achievements
