Project Background

A certain recycling company in Zhejiang Province has generated a large amount of wastewater containing zinc sulfate heptahydrate during its production process. This type of wastewater is characterized by high salinity, high corrosiveness, and contains a small amount of organic impurities. Traditional treatment methods are energy-intensive and inefficient, making it difficult to meet modern environmental protection requirements. To achieve efficient wastewater treatment and resource recovery, while reducing operating costs, the company has introduced the MVR tubular evaporation system and selected 2507 super duplex stainless steel as the main material to ensure the corrosion resistance and operational stability of the equipment.

 

 

Process flow

• Pretreatment: The heptahydrate zinc sulfate wastewater first undergoes pretreatment to remove suspended solids, large particle impurities and some organic matter, and adjust the pH value to ensure the stability of the subsequent evaporation process.

 

 

• MVR tubular evaporation: The pre-treated wastewater enters the MVR tubular evaporation system.

 

 

• Heating evaporation: Through mechanical steam recompression technology, the secondary steam is compressed and heated, and then recycled as a heat source. The wastewater is heated and evaporated in the evaporator, and the heptahydrate zinc sulfate gradually concentrates to a saturated state.

 

 

• Utilization of secondary steam: The secondary steam generated during the evaporation process is compressed by a compressor, its temperature and pressure are increased, and then it is reused as a heat source, achieving high efficiency and energy conservation.

 

 

• Freezing crystallization: The concentrated solution enters the freezing crystallization system, where zinc sulfate heptahydrate crystals are separated through low-temperature freezing crystallization (50℃). The frozen mother liquor is returned to the MVR system to achieve "zero discharge" of salt.

 

 

• Condensation and recovery: The condensate water generated during the evaporation process is treated and reused in production, achieving the recycling of water resources and reducing wastewater discharge.

 

 

• Finished product output: The crystallized zinc sulfate heptahydrate is separated by centrifugation to obtain high-purity crystals, which can be recycled as industrial raw materials.

 

 

Technical advantage

• High efficiency and energy conservation: MVR technology significantly reduces energy consumption through the recompression and recycling of secondary steam. Compared with traditional single-effect evaporation processes, its energy-saving effect can reach 60% to 80%.

 

 

• Strong corrosion resistance: The main body is made of 2507 super duplex stainless steel, which has excellent corrosion resistance and can effectively resist the corrosion of zinc sulfate wastewater, thus extending the service life of the equipment.

 

 

• High strength and toughness: The high strength and toughness of 2507 material enable it to perform exceptionally well in high-salinity and highly corrosive environments, ensuring the long-term stable operation of equipment.

 

 

• High degree of automation: Equipped with an advanced automatic control system, it realizes full-process automatic monitoring and operation, ensuring the stability of the production process and the consistency of product quality.

 

 

• Significant environmental benefits: By condensing and recovering secondary steam, wastewater discharge is reduced, meeting environmental protection requirements.

 

 

Application field

The MVR tubular evaporation system is widely used in fields such as chemical engineering, renewable resources, and environmental protection, and is particularly suitable for the treatment of high-salt wastewater and resource recovery.