At the back end of pollutant treatment for power plants, the desulfurization process produces desulfurization wastewater whose quality and volume vary widely with the type of coal used for power generation, process water quality and limestone quality. Desulfurization wastewater from most power plants is faintly acid with pH of 4-6. Suspended solids in the wastewater are largely fine particles made of dust from flue gas and desulfurization products (CaSO4 and CaSO3). Cl- concentration is up to 20000mg/L; Ca2+, Mg2+ and SO42- concentrations are also very high; heavy metals released from most power plants are outside the specified limit. Our zero wastewater discharge technology offers two solutions: flue evaporation and crystallization.
Technical principle: Desulfurization wastewater goes through a series of pretreatment processes including three treatment tanks, softening (optional) and concentrating (optional) before being sprayed by double stream spray gun into flue. Under the effect of hot flue gas, moisture in the wastewater evaporates into flue gas while salt crystalizes as particles falling into ash bucket or collected by dust precipitator. For 600MW units, vapor in flue gas after spraying water makes up 7.3% by volume and would not lead to major changes in flue gas parameters. The temperature drop of 4.67℃ is safe to dust precipitator and flue. The acid dew point of the flue increases by 0.946℃ and would not erode downstream flue.
Advantages: low investment and operation costs; high cost-effectiveness; release pollutants in wastewater in the form of dry ash; adjust flue gas property; increase dedusting efficiency; little impact on fly ash composition and trait; cause no heat loss to the generator.
Because of physical characteristics of pollutants in wastewater, salt crystals precipitate from the super-saturated solution in a specially-made crystallizer. Crystallization can be divided by crystallization technique into concentrating crystallization, cooling crystallization and vacuum crystallization. MVR + forced cycle crystallization is adopted, with reliable technology, high automation, high efficiency of heat utilization, high concentration, little scaling and low steam consumption.
Advantages: small impact from water quality; good quality of effluent water; generated salt crystals can be used for industrial purposes; short dwell time of product; low-temperature evaporation; little impact on product quality.
MVR is the process by which secondary steam is compressed in a compressor to increase its temperature for reuse. It saves energy by reducing energy consumption.