Plate Multi-Effect Evaporator

I. Core Structure and Working Principle

1. Basic Structure

The plate multi-effect evaporator uses a plate heat exchanger as its core heat transfer element, which is fundamentally different from the traditional tubular evaporator. Its core structure includes:

Heat transfer plates: Four plates with different structures form a group. The corrugated plates create a highly turbulent flow channel, achieving a heat transfer coefficient of 3500-5800 W/(m²·K).

Frame system: A modular structure composed of fixed clamping plates, movable clamping plates, front support columns, upper and lower guide rods, and clamping studs.

Flow channel design: 8-12mm wide flow channels are formed between the plates, allowing material and heating medium to flow counter-currently or concurrently within their respective channels.

2. Working process: Material forms a uniform liquid film on the plate surface through a distributor:

Falling film type: Material enters from the top of the plate and forms a descending liquid film under gravity, suitable for heat-sensitive materials.

Rising film type: Material enters from the bottom of the plate and rises upwards driven by steam, suitable for low-viscosity materials.

Rising and falling film type: Combining the characteristics of rising and falling film, it consists of four plates forming four flow channels, suitable for handling complex materials.

3. Multi-Effect Series Mechanism

Adopting a three- or four-effect series connection, the secondary steam from the previous effect serves as the heat source for the next effect:

First Effect: Heated using live steam (0.3-0.5MPa)

Second/Third Effect: Utilizing the secondary steam generated in the previous effect (temperature gradually decreases)

Final Effect: Secondary steam enters the condenser for condensation, maintaining a vacuum state in the system.

II. Technical Advantages and Performance Indicators

1. Excellent Energy Saving

2. Compact and Efficient Design

Heat Transfer Efficiency: 15-30% higher than traditional tubular evaporators; high turbulence; heat transfer coefficient 3-5 times that of tubular evaporators.

Space Saving: 30-50% smaller footprint than tubular evaporators.

Low Liquid Holdup: Short residence time of materials at high temperatures, particularly suitable for heat-sensitive products.

3. Convenient Operation and Maintenance

Removable Structure: Plates can be quickly disassembled and installed, extending the scaling cleaning cycle from 7 days for tubular systems to 60 days.

No Dead Angle Design: Corrugated surface prevents material accumulation; CIP automatic cleaning system reduces downtime.

Flexible Adjustment: Adaptable to different materials by increasing or decreasing the number of plates or adjusting the flow (co-current/counter-current/mixed flow).

III. Key Design Considerations

1. Anti-Scale Technology

Multiple measures are taken for materials prone to scaling, such as dairy products and juices:

Flow Channel Optimization: Wide flow channel design (8-12mm) + forced circulation flow rate of 2-3m/s reduces crystalline salt adhesion.

Coating Technology: Tungsten carbide-cobalt alloy or TiO₂ nano-coating is sprayed on the inner wall of the heat exchange tubes.

Process Control: Precise control of feed flow rate and steam pressure, enhanced concentration monitoring.

2. Material Selection

Plate material is selected based on the corrosiveness of the material:

316L Stainless Steel: Suitable for general food and chemical materials.

Titanium Alloy: Suitable for wastewater containing chloride ions.

Hastelloy Alloy: Suitable for strong acid and alkali environments, extending equipment life by 3 times.

3. Efficiency Configuration Principles

Triple-Effect Evaporator: Ideal for balancing energy saving and investment costs.

Quadruple-Effect Evaporator: Suitable for large-scale production such as sugar production.

Five-Effect and Above: The reduction in steam consumption decreases with each subsequent effect beyond three (five-effect evaporators only reduce steam consumption by 7% compared to three-effect evaporators), but equipment investment increases by 40%.

IV. Typical Application Areas

1. Food Industry

Dairy Products: Milk powder and condensed milk concentration, operating temperature 75-40°C, protecting protein activity.

Sugar Industry: Sugar juice concentration (increasing dry matter content from 15% to over 68%). One company used a multi-effect plate evaporator, reducing steam consumption by 12%.

Fruit Juice Beverages: Low-temperature concentration of high-viscosity fruit juice, preserving flavor and nutrition.

2. Environmental Protection and Wastewater Treatment

High-Salinity Wastewater: Daily treatment of 300 tons of lithium battery wastewater, with a nickel recovery rate of 98%.

Electroplating Wastewater: Three-effect systems achieve zero heavy metal emissions, saving over 5 million yuan annually.

Alkali Recovery: Plate falling film evaporator groups are used for papermaking black liquor evaporation, with a thermal efficiency 15-30% higher than tubular evaporators.

3. Pharmaceutical Industry

Low-temperature concentration of antibiotics and enzyme preparations (≤55℃), 98% retention rate of active ingredients. Compliant with GMP standards, fully enclosed production.

V. Kang Jinghui Technology Upgrade

1. MVR Coupling Technology

Plate multi-effect evaporator combined with mechanical vapor recompression (MVR): MVR compresses and heats secondary steam for recycling, with fresh steam consumption approaching zero. Power consumption for treating 1 ton of high-salt wastewater is 35-50 kWh, saving 50-60% energy compared to traditional multi-effect evaporators. A project using MVR + triple-effect process achieved sodium chloride and sodium sulfate separation purities >99%.

2. Intelligent Upgrade

PLC/DCS Integration: Real-time monitoring of over 20 parameters including temperature, pressure, and liquid level.

AI Predictive Maintenance: Predicts cleaning cycles based on scaling monitoring data, reducing unplanned downtime.

Modular Skid-Mounted: Flexible capacity adjustment from 1000-36000L/h, rapid disassembly and assembly within 72 hours.

VI. Selection Recommendations

Applicable Scenarios:

Large-scale continuous production (>5t/h evaporation capacity)

Heat-sensitive materials (food, pharmaceutical)

Materials prone to scaling but requiring frequent cleaning

Projects with limited space.

Unapplicable Scenarios:

Extreme high-temperature and high-pressure conditions (requiring special materials)

Strongly corrosive media without suitable materials

Small-scale production (low return on investment).

Plate multi-effect evaporators, with their high-efficiency heat transfer, compact structure, and ease of maintenance, have become the preferred alternative to traditional tubular evaporators in the food and environmental protection fields. With the maturity of MVR coupling and intelligent control technologies, their comprehensive energy efficiency advantages will be further highlighted.