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What is a Double Effect Evaporator?
A double effect evaporator is a thermal separation system that uses two stages (effects) of evaporation to concentrate solutions. The vapor generated in the first effect is used as the heating medium for the second effect, significantly improving energy efficiency compared to single effect systems.
Memva double effect evaporators are engineered for applications requiring high evaporation capacity with optimal energy utilization. Our systems achieve steam economies of 1.5-1.8 kg evaporation per kg steam, representing 40-50% energy savings compared to single effect evaporators.
Key Feature: Memva double effect evaporators typically achieve 40-50% lower steam consumption than single effect systems while maintaining high evaporation rates and product quality.
Double Effect Evaporation Technology
①
Energy Efficiency
Utilizes vapor from the first effect as heating steam for the second effect, achieving steam economy of 1.5-1.8 kg evaporation per kg steam (40-50% savings vs single effect).
②
Forward Feed Configuration
Feed enters the first effect at highest temperature and pressure, then flows to second effect at lower temperature. Most common configuration for many applications.
③
Backward Feed Configuration
Feed enters the second effect first (lowest temperature), then pumped to first effect. Ideal for solutions with high boiling point elevation.
④
Parallel Feed Configuration
Fresh feed enters both effects simultaneously. Suitable for solutions with high solids content where concentration is similar in both effects.
⑤
Mixed Feed Configuration
Combination of forward and backward feed. Offers flexibility for specific processing requirements and temperature-sensitive products.
⑥
Thermal Vapor Recompression (TVR)
Optional TVR system can further improve efficiency by recompressing vapor from second effect using high-pressure steam ejectors.
Memva Design Features
Heat Exchanger Design
Optimized falling film, forced circulation, or plate heat exchangers for each effect based on application requirements. Designed for maximum heat transfer efficiency.
- High thermal efficiency (>90% in first effect)
- Corrosion-resistant materials (SS316L, titanium, nickel alloys)
- Easy cleaning access for both effects
Separation System
Advanced vapor-liquid separation with high-efficiency demisters in each effect to minimize product loss and ensure high purity condensate recovery.
- Dual-effect demister systems
- Centrifugal separators
- Entrainment reduction >99.5%
Control System
Advanced PLC-based automation with touchscreen HMI for precise control of both effects, steam distribution, and concentration parameters.
- Automated inter-effect pressure control
- Remote monitoring and data logging
- Energy optimization algorithms
Memva double effect evaporators are designed for capacities from 1,000 to 100,000 kg/h evaporation rate, with operating pressures typically ranging from 0.2 to 5 bar in the first effect and vacuum conditions in the second effect.
Double Effect Process Flow
1
Feed Inlet
Dilute solution enters the first effect through preheater
2
First Effect
Steam provides thermal energy to boil solution in first effect
3
Vapor Transfer
Vapor from first effect becomes heating steam for second effect
4
Second Effect
Solution from first effect undergoes further evaporation
5
Concentrate Outlet
Final concentrated product is discharged from second effect
6
Condensation
Vapor from second effect is condensed to recover distilled water
Memva double effect evaporators typically achieve concentration factors of 10-40x, depending on feed characteristics and product requirements. Steam consumption is approximately 0.55-0.65 kg steam per kg of water evaporated, representing 40-50% savings compared to single effect systems.
Double Effect Evaporator Applications
Pharmaceutical
Pulp & Paper
Textile Industry
Metal Processing
Desalination
Double Effect vs Single Effect Comparison
| Parameter | Single Effect Evaporator | Memva Double Effect | Energy Savings |
|---|---|---|---|
| Steam Consumption | 1.0-1.2 kg steam/kg evaporation | 0.55-0.65 kg steam/kg evaporation | 40-50% |
| Operating Cost | Higher (more steam required) | Lower (reduced steam usage) | 35-45% |
| Capital Cost | Lower initial investment | Higher (additional equipment) | - |
| Footprint | Compact | Larger (two effects) | - |
| Complexity | Simple operation | More complex control | - |
| ROI Period | - | 1.5-3 years (energy savings) | Fast payback |
| Best For | Low capacity, intermittent operation, low energy costs | High capacity, continuous operation, high energy costs | - |
When to Choose Double Effect: Double effect evaporators are economically justified when steam costs are high, evaporation capacity is large, and continuous operation is required. The additional capital cost is typically recovered through energy savings within 1.5-3 years.
How much energy savings can I expect with a double effect evaporator?
Memva double effect evaporators typically achieve 40-50% steam savings compared to single effect systems. Steam consumption is reduced from 1.0-1.2 kg steam/kg evaporation to 0.55-0.65 kg steam/kg evaporation. The exact savings depend on operating conditions and feed characteristics.
What are the main configurations for double effect evaporators?
The three main configurations are: 1) Forward feed (most common) - feed enters first effect then flows to second effect; 2) Backward feed - feed enters second effect then pumped to first effect; 3) Parallel feed - fresh feed enters both effects simultaneously. Memva engineers recommend the optimal configuration based on your specific application.
What temperature and pressure conditions are used in each effect?
Typically, the first effect operates at higher temperature and pressure (e.g., 100-120°C, 1-2 bar), while the second effect operates at lower temperature and often under vacuum (e.g., 60-80°C, 0.2-0.5 bar). The temperature difference between effects is usually 10-20°C to ensure adequate heat transfer.
Can a double effect evaporator be converted to single effect operation?
Yes, Memva double effect evaporators can be operated in single effect mode if needed for maintenance, low capacity requirements, or specific process conditions. However, operating in single effect mode will increase steam consumption to typical single effect levels.
How does scaling compare between single and double effect evaporators?
Scaling tendency depends more on solution characteristics than the number of effects. However, double effect systems operating at lower temperatures in the second effect may experience different scaling patterns. Memva designs incorporate appropriate scale control measures for each effect based on operating conditions.