The Hezhongsi® MVR evaporation crystallization system is one of the zero-discharge solutions for high-concentration brine.
Hezhong Gaoko Environmental Protection pays close attention to the needs of customers in wastewater treatment, basing its work on rich practical experience in the field of zero-discharge wastewater treatment across multiple industries. It has established a strategic partnership with Whiting/Swenson, a Canadian company specializing in the research of thermal evaporators, and collaborated with authoritative experts both domestically and internationally to develop the Hezhongsi® MVR evaporation crystallization system technology. It provides comprehensive services to customers, including system design, equipment selection, on-site installation, commissioning, operation, and after-sales follow-up, ensuring the safe and stable operation of the system.

 

 

 

 

1. MVR Principle
MVR is short for Mechanical Vapor Recompression. An MVR evaporator is an energy-saving technology that reuses the energy of its own secondary steam, thereby reducing the need for external energy.

 

The MVR process involves compressing low-temperature steam using a compressor to increase its temperature, pressure, and enthalpy. The compressed steam then enters a heat exchanger to condense, making full use of the latent heat of the steam. Except for the start-up, the entire evaporation process does not require fresh steam. The secondary steam from the evaporator is compressed by the compressor, increasing its pressure and temperature, and thus its enthalpy. This steam is then sent to the heating chamber of the evaporator as heating steam, maintaining the boiling state of the material liquid. The heating steam itself condenses into water. In this way, only a small amount of electrical energy is needed to fully utilize the steam that would otherwise be wasted, recovering latent heat and improving thermal efficiency. The economic efficiency of fresh steam is equivalent to that of a 30-effect multiple-effect evaporator.
2. MVR Technology Characteristics
1) High thermal efficiency, energy saving, and low operating cost: Due to the 100% recycling of the latent heat of secondary steam, the use of fresh steam is completely avoided, greatly reducing energy consumption; the energy consumption for evaporating one ton of water is only 20-25% of that of traditional evaporators. This reduces operating costs for enterprises and environmental pollution. There is no waste heat steam discharge, and the energy-saving effect is very significant.
2) Because a compressor is used to provide the heat source, the temperature difference is much smaller compared to traditional evaporators, allowing for gentle evaporation, improving product quality, and reducing scaling.
3) No condenser is needed; the structure and process are very simple, simpler and more reliable than traditional multiple-effect evaporation equipment.
4) High degree of automation: The MVR evaporator uses an industrial control computer and PLC control system, as well as variable frequency technology, achieving fully automatic unmanned operation; it can operate continuously and is safe and reliable.
5) Clean energy, no pollution. The MVR evaporator can operate using electricity.

 

 

 

 

 

 

1. Industrial wastewater: Power plant desulfurization wastewater treatment, coal chemical wastewater treatment, petrochemical wastewater treatment, hydrometallurgical wastewater, wastewater from electroplating and surface treatment industries, dyeing wastewater, papermaking wastewater, smelting wastewater, rubber wastewater.
2. Chemical Industry:
(1) Chemical product production
(2) Seawater desalination
(3) Concentration and crystallization of organic additives
(4) Purification of fragrances
3. Food Industry
4. Pharmaceutical Industry
5. Beverage Industry

 

 

 

 

 

The MVR evaporation crystallization system is suitable for efficient reuse of industrial wastewater with large discharge volumes, complex water quality, and high salt content. Hezhong Gaoko has made a unique design based on the characteristics of domestic customer usage.

1. Customized process design based on customer needs
We not only provide MVR system equipment but also aim to meet the actual needs of our customers. We tailor-make complete solutions based on customer needs, including: pre- and post-MVR process supporting schemes; cost-effective equipment selection; full consideration of maintenance costs; ensuring the efficient and reliable operation of the MVR.

2. "Pretreatment + MVR" process approach, wider applicability
Appropriate pretreatment is selected for different water qualities. This includes membrane methods, double-alkali softening, ion exchange, etc., to ensure the long-term stable operation of the evaporation system. At the same time, considering the characteristics of the water quality, different processes are selected during the evaporator selection and design process, such as vertical tube falling film, horizontal tube falling film, plate falling film, and forced circulation, to improve evaporation efficiency, enhance resistance to impact loads, and improve the applicability of the system.

 

 

3. Combined process design to achieve zero discharge
The process design can achieve salt crystallization, and the concentrated water can be discharged to an evaporation pond, and then a forced atomization evaporator is used for evaporation. Zero discharge is achieved through a combination of processes.
4. Safe, reliable, and highly stable system
The system is fully automatically controlled, and key parameters are monitored using high-quality imported instruments to prevent interference from human factors. At the same time, the process design is optimized to ensure sufficient design margin, ensuring that the system can still operate smoothly even when the raw water quality fluctuates.

 

 

 

 

 

The investment and operating costs of evaporation crystallization equipment are relatively high. Therefore, before high-concentration brine evaporation crystallization is implemented, other technologies with lower investment and operating costs are usually used to reduce the amount of concentrated brine. These technologies used before entering the evaporation crystallizer are collectively referred to as the pre-concentration system.

 

The design of the pre-concentration process flow depends on the salt content of the incoming water. If the incoming water volume is large and the salt content is low, the concentration process will be longer; conversely, the process will be shorter. The specific pre-concentration process needs to be designed according to the specific water quality and quantity. The overall principle is to improve cost-effectiveness and achieve excellent treatment results with simple methods.

 

The technologies commonly used in pre-concentration processes include:

 

High-pressure reverse osmosis system:

The membrane form is similar to the spiral-wound membrane used in traditional desalination systems, but the membrane material and structure have been improved. The maximum operating pressure of the equipment can reach 120 bar, concentrating the TDS of the incoming water to 12-15%, greatly reducing the incoming water volume.

 

 

 

Tubular microfiltration membrane softening:

The treatment of high-concentration brine presents a significant challenge due to scaling. As the influent continuously concentrates, scaling substances accumulate. The high-concentration brine treatment process is often intense, involving high pressure and high temperature operations, making scaling highly likely and impacting normal system operation. Therefore, pretreatment, such as softening, is typically necessary to minimize the concentration of scaling-prone ions. Traditional softening methods, like the double-alkali method, use lime/sodium hydroxide and soda ash to precipitate calcium and magnesium ions. This process, combined with tubular microfiltration membranes, can replace subsequent coagulation, sedimentation, and filtration systems, significantly improving effluent quality and reducing system footprint. This is particularly suitable for sites with limited land.

 

 

 

Spray Crystallization Evaporation:

Wastewater crystallization is complex, and many substances cannot be crystallized using conventional thermal evaporation crystallization systems. For these substances, spray drying crystallization is an alternative. It can crystallize substances that cannot be crystallized by conventional crystallizers, such as those with high COD and high boiling points. It is usually not used alone due to its high energy consumption and is often used in conjunction with traditional evaporation crystallization systems to treat a small amount of residual liquid from the traditional evaporator.

 

 

 

Disc Tube Reverse Osmosis:

Its structure differs from traditional reverse osmosis membranes. The internal flow path design is more suitable for sites with poor water quality, offering better fouling resistance. It can operate at high pressure, up to 120 bar or more, concentrating the influent TDS to 12-15%.

 

 

 

Forward Osmosis Technology:

Also using a spiral-wound membrane, the principle is the opposite of reverse osmosis. Forward osmosis uses osmotic pressure, rather than overcoming it, to extract freshwater from the influent, concentrating the brine. The system does not require high external pressure for operation and can concentrate the influent TDS to approximately 18%.

After pre-concentration, the concentrated brine exceeds the operating conditions of membrane systems, and the concentrate volume is significantly reduced. For further volume reduction, or even salt crystallization, thermal evaporation crystallization is a mature technology.