MVR Evaporator for Magnesium Chloride Recovery from Electrolysis Brine Wastewater

MVR Evaporator for Magnesium Chloride Recovery from Electrolysis Brine Wastewater

Metallic magnesium production relies on molten magnesium chloride electrolysis, and brine purification pretreatment before electrolysis continuously discharges massive volumes of Magnesium chloride brine purification wastewater rich in residual magnesium chloride, calcium sulfate, potassium salt and trace heavy metal impurities. Direct discharge of this wastewater not only contaminates surrounding water and soil but also causes massive loss of recyclable magnesium salt resources, raising raw material procurement costs and triggering strict environmental penalties. Today, professional Magnesium chloride evaporation and crystallization equipment built on MVR mechanical vapor recompression technology delivers mature Magnesium chloride extraction solutions, converting waste brine into high-purity magnesium chloride crystals and reusable industrial water through closed-loop physical separation, which has become the mainstream sustainable process for global magnesium smelting plants.

Against the backdrop of worldwide carbon neutrality and zero-liquid-discharge (ZLD) industrial standards, traditional wastewater neutralization and solar evaporation methods can no longer satisfy large-scale magnesium electrolysis production demands. Chemical neutralization consumes large quantities of lime and generates massive hazardous mixed salt sludge, while natural solar ponds occupy huge land areas and are severely affected by seasonal weather. The integrated Evaporation Crystallization System launched by CONQINPHI perfectly solves the corrosion, scaling and low recovery bottlenecks of Magnesium chloride brine purification wastewater. This article elaborates on wastewater composition characteristics, complete MVR extraction workflow, core equipment configuration, economic and environmental advantages, and industrial application cases, providing actionable technical references for magnesium smelting enterprises seeking reliable Magnesium chloride extraction technology.

1. Composition & Treatment Challenges of Magnesium Chloride Brine Purification Wastewater

1.1 Main Pollutant & Resource Composition

The Magnesium chloride brine purification wastewater comes from desulfurization, calcium-magnesium precipitation, filtration and impurity removal links before magnesium chloride electrolysis, with distinctive physicochemical properties:

1. High magnesium chloride concentration, with MgCl₂ mass fraction ranging from 12% to 30%, containing recoverable magnesium salt core resources;

2. Mixed impurity ions including Ca²⁺, K⁺, Na⁺, SO₄²⁻, which easily form insoluble precipitates and scale on heat exchange surfaces during heating;

3. Strong corrosivity under high temperature and high salt conditions, requiring special anti-corrosion structural materials for evaporation equipment;

4. Large continuous discharge volume, with medium-sized magnesium electrolysis workshops producing 200–1500 cubic meters of wastewater per day.

If discharged without treatment, chloride ions will salinize soil and water bodies, while unrecovered magnesium chloride leads to continuous raw material waste. For a magnesium smelter with annual output of 10,000 tons of metal magnesium, the magnesium salt loss from untreated wastewater can reach millions of US dollars in economic losses every year.

1.2 Defects of Conventional Treatment Technologies

Before the wide application of Magnesium chloride evaporation and crystallization equipment, magnesium manufacturers mainly adopted two treatment routes, both with obvious drawbacks:

• Lime Neutralization Process: Low initial investment, but generates large amounts of calcium-magnesium mixed salt hazardous waste, 100% loss of magnesium chloride resources, and long-term waste stacking and transportation costs;

• Multi-Effect Evaporation without MVR: Relatively stable recovery effect, yet relies on continuous supply of live steam, resulting in extremely high energy consumption and operation costs, and frequent scaling blockage due to impurity precipitation.

Only the MVR-based Evaporation Crystallization System can realize low-energy continuous Magnesium chloride extraction while eliminating secondary solid waste pollution, matching the long-term uninterrupted production rhythm of magnesium electrolysis lines.

2. Core Mechanism: How MVR Evaporator Realizes Magnesium Chloride Extraction

CONQINPHI customized MVR forced circulation evaporator serves as the core of Magnesium chloride evaporation and crystallization equipment. The whole extraction process follows thermodynamics latent heat recycling and solubility difference crystallization logic, divided into five automated closed-loop stages for Magnesium chloride brine purification wastewater.

2.1 Pretreatment & Impurity Removal Stage

Raw brine wastewater first enters the regulating tank for homogenization of concentration and temperature, then flows into multi-stage precision filters and sedimentation tanks to remove suspended calcium sulfate, barium sulfate and colloidal impurities. This pretreatment step greatly reduces scaling frequency inside the MVR evaporator heat exchange tubes and improves the purity of final magnesium chloride crystals, laying a foundation for efficient Magnesium chloride extraction.

2.2 Low-Temperature Vacuum Evaporation Concentration Stage

Purified wastewater is pumped into the heating chamber of the MVR forced circulation evaporator. Under negative pressure vacuum environment, the feed liquid boils and evaporates at 50–70°C low temperature, effectively avoiding magnesium chloride hydrolysis and thermal decomposition under high temperature. The system continuously evaporates water to raise magnesium chloride concentration to supersaturated state, reducing wastewater volume by over 85%. The low-pressure secondary steam generated during evaporation is captured and delivered to the steam compressor, realizing internal heat recycling.

2.3 Secondary Steam Compression & Heat Circulation Stage

This is the core link that distinguishes MVR equipment from traditional evaporators. The low-temperature low-pressure secondary steam is sucked into centrifugal or Roots compressor, where mechanical work raises steam temperature and pressure, converting low-grade waste heat into high-temperature available heat source. The compressed high-temperature steam flows back to the heating chamber outer wall to continuously heat the brine feed liquid, forming an independent closed heat cycle. The whole system basically eliminates dependence on external live steam, cutting overall energy consumption by more than 55%.

2.4 Gradient Crystallization & Solid-Liquid Separation Stage

Supersaturated magnesium chloride concentrated liquid enters matched DTB crystallizer for staged crystallization. By precisely controlling system temperature, pressure and circulation flow rate, magnesium chloride hexahydrate (bischofite) crystals are selectively precipitated, while impurity salts remain in the mother liquor. The crystal slurry is sent to centrifugal separator for thorough solid-liquid separation: high-purity magnesium chloride crystals are discharged as finished products, and residual mother liquor flows back to the evaporator for secondary circulation concentration to maximize Magnesium chloride extraction rate.

2.5 Recycled Water Reuse & Zero Discharge Stage

Water vapor condensed after heat exchange forms clean desalinated fresh water, free of chloride and metal ions. The condensed water can be reused for brine purification washing, electrolysis workshop cooling and equipment flushing, completely cutting the factory’s freshwater intake demand. The entire processing flow outputs no external wastewater, fully meeting global ZLD environmental supervision standards for non-ferrous metal smelting industries.

3. Core Configuration of CONQINPHI MVR Evaporation Crystallization System for Magnesium Salt Recovery

To adapt to the high-corrosion, high-scaling characteristics of Magnesium chloride brine purification wastewater, CONQINPHI optimizes all core components of Magnesium chloride evaporation and crystallization equipment, forming a complete set of professional Evaporation Crystallization System for magnesium electrolysis supporting projects.

3.1 Forced Circulation MVR Evaporator Main Unit

Forced circulation structure is selected instead of falling film evaporator, as high-flow circulation prevents magnesium salt crystal adhesion and tube blockage. All liquid-contact parts adopt titanium alloy, Hastelloy or rubber-lined anti-corrosion materials to resist long-term chloride erosion, extending equipment service life to over 10 years. The heat recovery rate of the whole unit reaches above 92%, supporting 24-hour unattended continuous operation.

3.2 Customized Crystallizer & Solid-Liquid Separation Equipment

DTB crystallizer is standardly equipped for magnesium chloride fractional crystallization, with built-in fine crystal elimination device to stabilize crystal particle size and improve finished product purity. Matched horizontal centrifugal separators realize automatic continuous separation of crystal slurry, reducing manual operation intensity and avoiding magnesium crystal loss during separation.

3.3 Intelligent PLC Automatic Control System

The independent PLC control module monitors real-time wastewater concentration, evaporation temperature, compressor pressure and crystal slurry density. It automatically adjusts feed volume, circulation pump speed and compressor operating power according to fluctuations of incoming Magnesium chloride brine purification wastewater, stabilizing the Magnesium chloride extraction rate above 96% and ensuring consistent crystal quality. Remote online monitoring function supports overseas client after-sales diagnosis and parameter adjustment.

3.4 Auxiliary Heat Exchanger & Preprocessing Unit

All-welded tubular heat exchangers are configured for wastewater preheating, recovering residual heat from condensed fresh water to further reduce system power consumption. The integrated pretreatment skid realizes automatic slag discharge and online cleaning, greatly lowering daily equipment maintenance frequency.

4. Outstanding Economic & Environmental Benefits of MVR Magnesium Chloride Extraction Technology

4.1 High Resource Recovery & Sharp Raw Material Cost Reduction

The mature Evaporation Crystallization System achieves over 96% recovery rate of magnesium chloride from brine purification wastewater. Recovered high-purity magnesium chloride hexahydrate can be directly sent to dehydration workshop for electrolysis raw material preparation, or sold as commercial bischofite products to construction, road deicing and chemical industries. For magnesium smelters, the recovered magnesium salt resources can offset most equipment operation power costs, with full investment recovery cycle within 2–3 years for large-scale projects.

4.2 Zero Hazardous Waste & Compliance with Global Environmental Policies

Different from lime neutralization that produces tons of mixed salt sludge every day, the whole MVR physical extraction process only outputs recyclable magnesium chloride crystals, without any hazardous waste residue. Factories eliminate waste landfill construction fees, transportation expenses and environmental fines caused by chloride wastewater discharge, smoothly passing EU, Southeast Asia and North America industrial environmental audits and green factory certifications.

4.3 Ultra-Low Energy Consumption & Carbon Emission Reduction

Relying on MVR steam recycling technology, the system requires almost no live steam supply, only consuming electric energy to drive compressors and circulating pumps. Compared with traditional triple-effect evaporators, comprehensive operation energy consumption is reduced by over 50%, significantly cutting fossil fuel combustion and factory carbon emissions, helping magnesium enterprises fulfill carbon neutrality transformation targets.

4.4 Compact Modular Layout & Flexible Capacity Expansion

The integrated modular design of Magnesium chloride evaporation and crystallization equipment occupies small workshop space, shortens on-site installation and commissioning cycles. Reserved expansion interfaces allow clients to upgrade evaporation capacity without full equipment replacement as magnesium electrolysis production lines expand, bringing long-term flexible production advantages.

5. CONQINPHI Brand Introduction & Custom Solution CTA

As a global professional manufacturer of industrial evaporation and crystallization equipment, CONQINPHI has accumulated dozens of engineering projects serving magnesium smelting, salt lake brine processing, non-ferrous metal electrolysis and chemical industries. We independently develop targeted Evaporation Crystallization System for high-chloride, high-salt wastewater including Magnesium chloride brine purification wastewater, mastering mature Magnesium chloride extraction technology with verified stable operation effects across global client sites.

Our factory owns a 90,000 square meters modern production base, professional corrosion-resistant material testing laboratory and full-process engineering team covering free water quality analysis, process simulation drawing, equipment customized manufacturing, global on-site installation, commissioning and 24/7 multilingual after-sales support. All equipment passes CE and ISO industrial quality certifications, with local overseas service teams in Southeast Asia, Middle East, Africa and Europe to respond to client technical demands rapidly.

If your magnesium electrolysis plant faces troubles such as high wastewater treatment costs, severe magnesium resource loss, excessive solid waste stacking or unstable magnesium chloride recovery purity, please contact CONQINPHI immediately. Our professional chemical and evaporation engineers will provide free water quality testing reports, personalized Magnesium chloride evaporation and crystallization equipment process design and detailed equipment quotation, delivering a one-stop ZLD magnesium salt recovery solution tailored to your actual wastewater volume and brine composition.