Coal-Washing Wastewater Purification in Coal-Fired Power Plants: Existing Challenges and Technological Innovation
In the continuous production process of coal-fired power plants, the purification of coal-washing wastewater is a key environmental protection task. When a power plant pre-treats, processes and burns coal, operations such as washing, screening and dewatering generate large amounts of coal-washing wastewater. This wastewater contains suspended particles (such as coal dust and silt), dissolved organic components (phenols, aromatic hydrocarbons, etc.), oil and grease, heavy metal ions (lead, cadmium, mercury, etc.) and other inorganic salts. It is characterized by a large discharge volume, complex water composition, high suspended solids concentration and oil content, making purification difficult.
The pollutants in the wastewater not only affect water quality, but may also pose a threat to the natural environment and ecosystems. For example, high concentrations of suspended solids easily cause pipeline blockage and equipment wear; oil and grease are difficult to remove completely and may cause secondary pollution if handled improperly; heavy metal ions are significantly toxic and endanger the health of living organisms; and sharp fluctuations in water quality also place stringent demands on the adaptability of treatment technologies.
The coal-washing wastewater treatment technologies previously used by coal-fired power plants mostly relied on conventional methods such as sedimentation, filtration, coagulation and air flotation. Although these methods can partially remove suspended solids and oil from the wastewater, they still have obvious shortcomings. First, treatment efficiency is limited and effluent quality fluctuates greatly, making it difficult to continuously meet discharge requirements. Second, the treatment process produces large amounts of oily sludge, which is not only expensive to dispose of but also occupies a large area and requires considerable manpower for operation and maintenance. Moreover, in the face of frequent changes in water quality, conventional processes have weak resistance to load fluctuations and lack effective countermeasures.
To overcome the limitations of existing technologies, SINOKLE has introduced an innovative coal-washing wastewater treatment process for coal-fired power plants, whose key equipment is a two-stage CDFU cyclonic dissolved-air flotation system. Based on purely physical methods and combined with a number of advanced patented technologies, it achieves efficient, stable and eco-friendly wastewater purification.
(Figure 1: Process flow diagram of coal-washing wastewater treatment in a thermal power plant)
The process steps are as follows: the wastewater first enters a collection tank for preliminary filtration to separate larger debris, and then enters a two-stage CDFU cyclonic dissolved-air flotation unit for deep treatment. Inside the CDFU system, high-pressure dissolved-air water is injected into the wastewater to form a large number of micro-bubbles. By virtue of the unit's special cyclonic structure, these bubbles fully contact and adhere to suspended particles, oil and other pollutants in the wastewater, lifting them to the liquid surface and thereby separating the pollutants. Finally, the treated wastewater enters the downstream purification unit, further ensuring that the water quality meets discharge or reuse standards.
(Figure 2: two-stage CDFU unit on site)
The process performs outstandingly in technical terms: with influent oil and suspended solids both ≤1000 mg/L, the effluent oil and suspended solids after treatment are both ≤20 mg/L, giving a remarkable pollutant removal effect.
Compared with the previous technology, SINOKLE's new process offers outstanding advantages in many respects: strong resistance to load fluctuations, adapting to variable water quality and ensuring stable effluent; high treatment efficiency, with the two-stage CDFU cyclonic dissolved-air flotation system efficiently separating pollutants; a simple, physics-dominated flow that simplifies the stages and lowers operating costs; less oily sludge, reducing the burden of downstream disposal; no chemical dosing throughout the process, making it a green process; and fully automatic closed operation with a small footprint, low manual operation and maintenance requirements and simple management, improving overall treatment efficiency and operational control.
With the above significant advantages, SINOKLE's new coal-washing wastewater treatment process has broad application potential, providing solid technical support for power plants' environmental protection practice and helping the industry move toward sustainable operation.
