MVR technology applied in highly concentrated salt-containing dyestuff wastewater

Dyestuff industry is the critical one in the national economy, China's dyestuff production has reached 900 thousand tons, accounting for about 60% of the world's dyestuff production, and it’s mainly used in the textile, leather, food, paint, ink, rubber and so on. China is giant dye-producer and can produce It can produce dyes of eleven kinds, more than 550 varieties. The production and trade volume of dyes are the highest in the world.Dye wastewater refers to the wastewater discharged in the producing process of dyes and pigments, the statics shows that there are 12% discharged in forms of wastewater.Our country discharges about 160 million cubic meters of dye wastewater into various types of water environment, and the rate of wastewater treatment is only 25%, the majority of wastewater without proper treatment directly discharges into rivers and lakes, causing serious water pollution. With increasing environmental concerns in recent years, the policy also has more stringent requirements for wastewater discharge, including dye wastewater, the latest policy stipulates that dye wastewater should achieve the goal of zero emissions. Currently, there are no barriers in the treatment of dye wastewater at the technical level to achieve the goal of zero emissions except for cost, which is priority to solve out by enterprises for the sake of the sustainable development. 

Fig 1 Dye wastewater

A large number of low-pressure steam can be reused by using very little energy with MVR technology, especially is suitable for dealing with high salinity wastewater in dyestuff industry. The characteristics of wastewater from dye industry is with large quantity, high chromaticity, high poisonous and detrimental substances, and difficulty in handling etc., which is suitable for forced circulation evaporator. We take Yabang dye as an example to understand the process about forced circulation. The flow chart of the forced circulation evaporator as below:

Fig 2 Flow chart of forced-circulation evaporation

Based on characteristics of high-salinity wastewater, the wastewater will be concentrated to  supersaturation condition, then the wastewater in supersaturated state is into the slurry pipe for further thickening, and then enters into the centrifuge for solid-liquid separation and the mother liquor is returned to the evaporation system for further evaporating. In this process, the evaporator in the form of externally heated forced circulation evaporation crystallizer can make the crystal with a growing process, the larger crystal particles, which can be separated more easily after entering into the centrifuge. When forced circulation evaporation occurs, circulation of the solution in the equipment mainly depends on the forced flow generated by the external movement. The speed can reach 1.5-3.5 meters per second, and the heat transfer efficiency and production capability are relatively large.

Fig 3 MVR system applied in the concentration of dye wastewater with high salinity

The application of MVR technology in industrial wastewater treatment has the advantages of reasonable cost and good applicability. It is an ideal process of wastewater and waste residue treatment from industrial wastewater at present stage and they are thoroughly treated and recycled. Characteristics of excellent research and development team, outstanding technology in design, exquisite processing technology and high reliability, strict quality management is the high-quality assurance of "MVR system" produced by Turbovap, and the technology applied will plays an important role in dealing with dye wastewater even the industrial wastewater.

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