The evaporation treatment of common wastewater from coal-fired power plants is one of the key technologies to achieve zero wastewater discharge. The following are several common methods of wastewater evaporation treatment:

          1、 Flue evaporation method

          The flue evaporation method is to spray wastewater into the flue of a power plant, use the heat of the flue gas to evaporate the wastewater, and thus achieve zero discharge of wastewater. This method can be divided into evaporation inside the flue and evaporation outside the flue according to the different evaporation positions.

          1. Evaporation in the flue:

          Technical principle: The desulfurization wastewater is directly sprayed into the inlet flue of the dust collector through a dual fluid atomizing nozzle for evaporation treatment.

          Advantages: Simple process, low investment and operating costs.

          Disadvantages: There are risks of flue corrosion and pollutant deposition.

          2. Evaporation outside the flue:

          Technical principle: the desulfurization wastewater is atomized into droplets with a particle size of tens of microns through a rotary atomizer and sprayed into the spray drying device. Part of the hot flue gas in front of the air preheater is extracted as the heat source, and the wastewater is evaporated in the spray drying device.

          Advantages: Simple system, reliable operation, and low investment cost. The pollutants in the wastewater are converted into crystalline salts, some of which fall to the bottom of the drying device and are transported by pneumatic conveying to the existing ash treatment system of the coal-fired power plant; The other part is carried by the flue gas into the electrostatic precipitator and removed together with the fly ash.

          2. Evaporation Crystallization Method

          Evaporation crystallization method is another commonly used method for wastewater evaporation treatment. By heating the wastewater to boiling, the water in the wastewater gradually evaporates, while the soluble solids are trapped in the residual liquid and precipitate in the form of crystals as the concentration ratio increases.

          1. Multi effect evaporation crystallization process:

          Principle: Multiple evaporators are operated in series, with the secondary steam from the previous evaporator serving as the heating steam for the subsequent evaporator, thus achieving the recycling of thermal energy.

          Advantages: High energy efficiency.

          2. Steam recompression evaporation crystallization process (MVR/TVR):

          Principle: Use a compressor to compress the secondary steam generated by the evaporator, increase its temperature and pressure, and then send it back to the evaporator as heating steam.

          Advantages: It can achieve maximum utilization of thermal energy and reduce energy consumption.

          3. Horizontal film spray/MVC evaporation system+crystallization system:

          Advantages: Low energy consumption, no scaling inside the pipe, and the ability to install online cleaning facilities. Introducing high-purity crystal salt separation technology during the crystallization process can extract high-purity NaCl, which can be used as industrial salt to generate economic benefits.

          3、 Preprocessing and concentration reduction technology

          Before conducting evaporation treatment, it is usually necessary to pretreat and concentrate the wastewater to reduce the construction and operation costs of the evaporation section.

          1. Preprocessing techniques:

          Chemical softening: such as limestone sodium carbonate softening, lime flue gas softening, sodium hydroxide sodium carbonate softening, etc.

          Filtration: including tubular microfiltration, ultrafiltration, nanofiltration, etc.

          2. Concentration and reduction technology:

          Membrane concentration: such as nanofiltration membranes, forward osmosis membranes, reverse osmosis membranes, and electrodialysis membranes.

          Thermal concentration: such as multi effect evaporation, steam recompression evaporation, low-temperature flue gas waste heat evaporation, etc.

          4、 Other evaporation treatment technologies

          In addition to the above methods, there are also some other evaporation treatment technologies that are also used in the wastewater treatment of coal-fired power plants, such as spray drying, fluidized bed drying, etc. These methods each have their own characteristics and can be chosen according to the actual situation.

          There are multiple methods available for the evaporation treatment of wastewater in coal-fired power plants, and the specific choice of method needs to be comprehensively considered based on the nature of the wastewater, the treatment capacity, and the actual situation of the power plant. In practical applications, attention should also be paid to equipment selection, optimization of operating parameters, and maintenance management to ensure the stable operation and standard discharge of wastewater evaporation treatment systems.