Application of the hottest MVR evaporation technol

Application of MVR evaporation technology in zero discharge of metallurgical industrial wastewater

with the rapid economic development and people's increasing demand for environmental protection, non-ferrous metal processing enterprises have increased capital investment and technical exploration in industrial wastewater treatment, and strive to achieve zero discharge of industrial wastewater on the basis of ensuring that industrial wastewater meets the standard discharge

reverse osmosis (RO), as one of the typical technologies of wastewater resource utilization, is widely used in the advanced treatment of secondary effluent of enterprise wastewater. However, RO concentrated water has high salt content, and it is difficult for the effluent quality to meet the discharge standard when using ordinary methods. The development of new treatment technology for RO concentrated water is particularly important

mvr process can well solve the problem of difficult ro concentrated water treatment. Its huge technical advantages can be widely used in biochemical, petrochemical, pharmaceutical, I believe professionals know, food manufacturing, environmental protection, seawater desalination and many other fields. Shaoguan Smelter uses MVR evaporation technology to treat RO membrane concentrated water, which can re concentrate ro concentrated water and reuse the evaporated water at the same time, so as to achieve the combination of wastewater treatment and resource utilization, concentrate to the crystallization stage, and after subsequent crystallization treatment, inorganic salts dominated by sodium sulfate can be obtained, and finally zero discharge of metallurgical industrial wastewater can be achieved

1 MVR evaporation technology principle

mechanical vapor recompression (MVR) technology, the secondary steam produced by evaporator evaporation, which originally needs to be condensed by cooling water, is compressed by the compressor, its pressure and saturation temperature are increased, the enthalpy is increased, and then sent to the evaporator heater as a heat source to replace the steam for recycling, and the latent heat of the secondary steam is fully utilized, so as to achieve the purpose of energy saving. Compared with traditional multi effect evaporation, the total energy consumption of mechanical vapor recompression (MVR) technology is more than 70% less than that of multi effect evaporation

2 engineering application of MVR evaporation technology

2.1 MVR engineering application

mvr technology is gradually applied to the concentration and treatment of wastewater. Because of its remarkable energy-saving effect and mature and reliable technology, it can save a lot of investment and operating expenses for enterprises, greatly reduce production costs, and thus bring huge economic benefits

non ferrous metal smelting enterprises have tentatively introduced MVR evaporation technology to solve industrial wastewater. This paper takes Shaoguan Smelter's application of MVR technology to treat wastewater as an engineering example, and discusses the application of MVR evaporation technology in zero discharge of metallurgical industrial wastewater

Shaoguan Smelter is a large-scale lead-zinc smelting enterprise at the advanced level of the same industry in China in terms of process technology, equipment level and environmental protection after more than 40 years of exploration and innovation. The industrial wastewater of the factory adopts the chemical precipitation method of biological agents to treat heavy metals. For the equipment manufacturers of renewable plastic granulator, membrane separation technology and RO concentrated water MVR evaporation crystallization make the industrial wastewater achieve zero discharge

Shaoguan Smelter strictly regulates the water consumption in all links of smelting, strives to improve the recycling efficiency of industrial water, and strictly controls the total amount of sewage entering the terminal wastewater treatment system, so as to reduce the total amount of industrial wastewater in the plant, and at the same time, make the wastewater quality contain relatively high inorganic salts. After the heavy metal removal process and membrane system technology, RO concentrated water with relatively high inorganic salts is finally obtained

since there is no precedent for using MVR evaporation technology to treat non-ferrous smelting wastewater, the factory finally adopted the process technology of "pretreatment softening + falling film evaporator evaporation + forced circulation evaporation crystallization + centrifugal drying and packaging process" as the main body through several technical explorations, forming the softening, evaporation, crystallization, drying and packaging process for waste water. Ro concentrated water is finally presented in the form of inorganic salts mainly distilled water and sodium sulfate, Realize the goal of zero discharge of wastewater. The process flow chart is shown in Figure 1

2.2 ro concentrated water quality

Shaoye industrial wastewater is concentrated by nanofiltration membrane and reverse osmosis membrane. Ro concentrated water quality contains high concentration of inorganic salts. Through the test, the salt content of RO concentrated water is between 2% and 3%, mainly including sodium ions, calcium ions, sulfate ions, chloride ions and fluorine ions

since this water contains chloride ions and fluorine ions, the corrosion of the equipment is extremely serious. Therefore, it is necessary to choose titanium materials with strong corrosion resistance. In the process of evaporation, the corrosion rate of titanium materials is less than 0.013mm/a at various concentrations of 20 ℃ ~ 100 ℃, so the selection of titanium materials can solve the problem of equipment corrosion caused by chloride ions and fluorine ions

2.3 MVR distilled water quality and solid salt

through the engineering example of Shaoye, the high concentration ro concentrated water is evaporated, and the condensed water is close to the distilled water by testing, so it can be completely recycled

the evaporated solid salt is mainly sodium sulfate through the test, which can be used for the recovery of low-grade salt resources

2.4 MVR evaporation process characteristics

mvr evaporation process characteristics: (1) after startup, there is no need to consume raw steam, or add a small amount of raw steam to maintain steam temperature. The operation cost is mainly the power consumption of the compressor, and the operation cost is greatly reduced; (2) Small floor area; (3) There are few supporting utilities, -- secondary steam condenses into water in the evaporator, and there is no need to set another condenser and use circulating cooling water; (4) The startup and operation are simple and easy, with few operators, stable operation and high degree of automation

3 conclusion

the RO concentrated water treated by MVR technology in Shaoguan Smelter finally exists in the growth trend of distilled water and solid salt market, such as paper packaging, paperboard, aluminum foil, etc. distilled water can be directly reused for production, and the solid salt produced is an inorganic salt dominated by sodium sulfate, which can be treated with low-grade sodium sulfate as a resource

in the process of operation, the scaling of falling film evaporator can be slowed down by adjusting the process operation, and the scaling of forced circulation evaporator can be avoided at the same time. Therefore, MVR evaporation technology, with its unique technical advantages, can complete the recycling of Smelting Wastewater and finally realize zero discharge of Metallurgical Wastewater