Innovative Solution for the Oily Wastewater Treatment Challenge of Heavy-Oil Power Plants

A power plant using heavy oil as its main fuel is a type of thermal power generation. Such plants burn heavy oil to generate heat, drive the turbine units, and then the generator converts mechanical energy into electricity.

A heavy-oil power station in Pakistan

During operation, in addition to combustion exhaust gas, such plants also produce oily wastewater with complex composition. Its sources include the cleaning operations of fuel storage tanks, leakage and washing wastewater during the maintenance of oil pumps and pipelines, and the accidental mixing of lubricating oil in the coal conveying system. In this wastewater, heavy oil and light oil coexist, and the limited treatment scale restricts the application of high-efficiency recovery technologies; the presence of emulsified oil makes it difficult to achieve separation by natural settling alone; and although coal washing wastewater has a low oil concentration, it contains a large amount of suspended solids and solid residue, making the treatment process rather complicated. Although the oil content in the wastewater appears low on the surface, if discharged directly without proper treatment, it will seriously impact the subsequent water treatment system and threaten its stable operation and compliance discharge.

At present, the mainstream treatment technologies for oily wastewater in power plants mainly include the following:

Composite sedimentation tank + high-definition filter method: this method relies on chemical agents to assist in settling oil and suspended solids, but it requires a large land area and high capital cost, has a low level of automation, requires regular manual cleaning, and carries safety hazards and environmental risks.

Oil separator + flotation tank + filtration system: traditional flotation tanks can hardly effectively remove emulsified and high-density oil droplets, the treatment effect is unstable, and they are prone to clogging the filter; they also face problems of large floor area and high cost.

Oil-water separator technology: since the specific gravities of oil and water are similar, simple gravity separation has limited effect, poor resistance to fluctuation, and unstable effluent quality; meanwhile, the equipment occupies a large area and the packing is easy to clog, so the overall performance needs to be improved.

Therefore, developing more efficient, environmentally friendly, and economical oily wastewater treatment technology for thermal power plants has become a key topic that the industry urgently needs to tackle.

To meet this challenge, SINOKLE Technology, relying on its core patented products such as the CDFU (Cyclonic Dissolved Air Flotation) unit, has developed an oily wastewater treatment process scheme dedicated to heavy-oil power plants according to the different characteristics of power plant wastewater. The brief process flow is shown in the figure below:

Oily Wastewater Treatment Process for Heavy-Oil Power Plants

This stable and reliable process was successfully applied in the newly built wastewater treatment project of a heavy-oil power station in Sierra Leone. The project is located in Tonkolili District, Northern Province, Sierra Leone, on the west coast of Africa, and is equipped with 5 heavy-oil generating units with a total installed capacity of 43.65 MW.

The oily wastewater generated by the station is characterized by high heavy-oil density, high viscosity, rich resin and asphaltene content, significant emulsification, and high treatment difficulty. To ensure that the effluent quality continuously and stably meets the standard, SINOKLE Technology adopted its core patented equipment—a two-stage CDFU cyclonic dissolved air flotation oil-water separation system—in this project. The system can efficiently remove oil and suspended solids, successfully treating the floor washing wastewater of the main power building and oil pump house as well as the oily wastewater from the oil storage tank area to the specified standard before discharge.

Oily Wastewater Treatment Equipment of a Fuel Power Station in Bangladesh, Commissioned in 2021

This solution has the following significant advantages:

• Mature and stable process, good oil and suspended solids removal, ensuring effluent quality;

• Strong shock resistance, high efficiency, stable effluent, thoroughly solving the problem of oily wastewater discharge from power plants;

• Short process flow, mainly based on the pure physical method, with stable effect, less oily sludge, and environmentally friendly technology;

• Skid-mounted design with compact equipment to reduce floor area and weight;

• Meeting the requirements of automatic control and convenient operation, with an automated design that minimizes manual operations and reduces the operating intensity as much as possible;

• Excellent economy, good stability, and strong operability.

The oily wastewater treatment process for heavy-oil power plants is technically mature and highly stable, has been verified by a number of engineering examples at home and abroad, can ensure long-term stable compliance of the effluent, and keeps the operating risk at the lowest level.