1. Equipment Overview
This system is a Mechanical Vapor Recompression (MVR) evaporator combining tube falling film evaporation and forced circulation crystallization, designed for the efficient concentration and crystallization of potassium chloride (KCl) solutions. The system is constructed primarily from titanium (TA1/TA2) to ensure corrosion resistance, given the aggressive nature of chloride-containing solutions.
2. Key Features
Evaporation Capacity: 4.5 tons/hour
Process Type: Continuous evaporation & crystallization
Location: Hunan, China (high humidity & potential scaling challenges)
Material of Construction (MOC):
Heat exchanger tubes & vessel: Titanium (TA1/TA2) for superior chloride resistance
Piping & pumps: Titanium or high-grade stainless steel (if applicable)
Crystallizer: Titanium-lined or solid titanium for abrasion resistance
3. Working Principle
(1) Tube Falling Film Evaporation (Primary Stage)
Feed Distribution: The KCl solution is evenly distributed over the vertical titanium tubes as a thin falling film.
Heat Transfer: The film flows downward while waste steam (compressed by MVR) heats the tubes externally, evaporating water efficiently.
Advantages:
High heat transfer efficiency (low ΔT)
Low energy consumption (MVR recovers latent heat)
Reduced scaling risk due to short residence time
(2) Forced Circulation Crystallization (Secondary Stage)
Circulation Pump: A titanium centrifugal pump drives the concentrated KCl solution into the crystallizer.
Supersaturation & Crystal Growth: Controlled evaporation under forced circulation promotes uniform KCl crystal formation.
Separation: The slurry is sent to a centrifuge or filter for solid-liquid separation.
4. System Components
Component Function Material
Preheater Heats feed solution using condensate heat recovery Titanium (TA2)
Falling Film Evaporator Primary evaporation stage Titanium tubes (TA1/TA2)
MVR Compressor Recompresses vapor for reuse Stainless steel (impeller may be titanium-coated)
Forced Circulation Pump Ensures high flow rate to prevent scaling Titanium (TA2)
Crystallizer Promotes KCl crystal growth Titanium (TA2) with anti-scaling design
Cyclone Separator Removes entrained droplets from vapor Titanium (TA1)
Condensate System Recovers heat from condensed water Titanium/SS316L
5. Advantages of MVR + Forced Circulation for KCl
✔ Energy Efficiency: MVR reduces steam consumption by 70-80% compared to traditional evaporators.
✔ High Purity Crystals: Controlled supersaturation in forced circulation ensures uniform crystal size.
✔ Corrosion Resistance: Titanium construction extends equipment lifespan in chloride environments.
✔ Compact Design: Suitable for 4.5T/h capacity with a small footprint.
