Wiped Film Evaporators
Evaporation applications that involve high boiling points, high viscosity, heat sensitivity or fouling products can be troublesome. Pfaudler’s extensive experience and expertise in this area and the Pfaudler Wiped Film Evaporators (WFE) are the solution.
The Wiped Film Evaporators (WFE) are designed to continuously separate volatile compounds by introducing a mechanically agitated thin film of feed material to a heated surface for efficient and reliable processing of a wide variety of products. WFE’s operate under high vacuum in order to reduce operating temperatures for high boiling and heat sensitive products. The short residence time minimizes the heat history to prevent thermal degradation. Special WFE designs provide for efficient processing of viscous materials like polymers and resins. The wipers continually clean the heat transfer surface making the WFE ideal for fouling applications
WFE Design Features
The operating features of Pfaudler’s WFEs, such as high vacuum (short path) distillation, short residence time and a highly agitated thin film of feed product on a heated surface, makes WFEs ideally suited to handle a wide range of heat sensitive, high boiling, fouling, and viscous materials.
With WFE sizes ranging from 1.2 sq. ft. (0.1sqm) to 500 sq. ft. (46.5sqm), no application is too small or too big for Pfaudler. Every Pfaudler Wiped Film Evaporator is thoroughly tested and inspected prior to shipment via Factory Acceptance Testing including a vacuum rise test, internal and jacket hydrostatic pressure test, and a operational test with water to ensure the WFE is operating precisely to our standards prior to shipment.
Pressure Vessel Design
Wiped Film Evaporator Systems
Unique WFE Design Advantages
Slotted Wiper Blades
Unique wiper blade designs effectively spread the material in a thin film on the wall for better heat transfer. Blades move the product down the heated wall in matter of seconds to minimize residence time.
Low Rotor Speed
High rotor speeds are not necessary with Pfaudler WFEs. The high heat transfer coefficient, provided by the Pfaudler WFE design, requires lower rotor speeds, which greatly extends the service life of the wiper blades, mechanical seal and drive bearing.
No Bottom Steady Bearing
Unlike a typical fixed clearance evaporator design, the Pfaudler WFE rotor is supported entirely from the top drive and bearing assembly, all mounted to the WFE top cover and main shell flange. This is accomplished by means of Pfaudler’s robust overhung design. With no bottom steady bearing, no flux oil is required, which is critical when non-volatiles are the product.
Low Horsepower Requirements
The low rotor speed significantly reduces horsepower requirements. This provides a significant savings in use, especially when compared to the same size fixed clearance evaporator.
Expandable WFE Sizes
For some models, additional thermal sections can be installed above the original thermal section at your plant site to provide increased capacity for existing WFEs. Easy Rotor Removal Any size WFE rotor can be removed and reinstalled in 30 minutes or less. Simply disconnect the motor leads, feed line, and bolts, then lift the rotor out of the shell as one complete assembly. This allows for quick, easy, inspection, maintenance, and cleaning.
The Pfaudler design with no bottom steady bearing allows for the installation of an internal condenser. WFEs with internal condensers minimize pressure drop compared to external condensers, allowing for high-vacuum operation. The high vacuum, and the proximity of the condenser surface area to the heated wall, provides better separations and ensures complete condensation and sub-cooling.
Efficient Entrainment Separators
Specially designed, full-length entrainment separators for standard and high-vacuum operation effectively remove entrained droplets from the vapor stream and improve the purity of the distillate product.
Pfaudler’s high-vacuum design WFE can operate with vacuums as low as one micron (.001 torr). Operating at deep vacuum lowers operating temperatures and prevents thermal degradation.
For viscous materials with high melting points, the WFE bottom head can be heated, and extruder blades can be utilized to mechanically aid in discharging heavy material.
Depending on the application, Pfaudler typically recommends only one shutdown per year for 1-2 days for inspection and maintenance. Mechanical seals typically last for many years. There is no bottom bearing and thus no costly maintenance.
Our unique WFE drive assembly enables our customers to easily access the mechanical seal for replacement without having to remove the complete rotor assembly, minimizing down time and extra costs associated with overhead cranes.