Product category:
Separation and Membrane Systems
News Release from: Labtex | Subject: Pope Wiped-Film Still
Edited by the Processingtalk Editorial
Team on 27 July 2007
Pope brand Wiped-Film Stills introduced
Wiped-Film Still technology takes advantage of the fact that each chemical substance has a characteristic vapour pressure, to enable separation or stripping of components from mixtures
Since the molecules of all matter are in constant motion in varying degrees, depending on the chemical composition of that matter and the temperature and pressure applied to it, molecules near the surface have a tendency to escape into the surrounding atmosphere As temperature increases and pressure decreases, this escaping tendency usually increases and the substance is said to vaporise
This article was originally published on Processingtalk on 31 Oct 2005 at 8.00am (UK)
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The force generated by these escaping molecules is referred to as the vapour pressure of that material at a particular temperature and pressure.
It is this relative difference in vapour pressure which dictates how easily a complex compound can be separated into its constituent components.
The Pope Wiped-Film Still consists of a heated body into which a fluid system requiring some degree of separation is continuously fed.
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The fluid is spread into a thin film by a rotating wiper blade assembly driven at a predetermined speed.
The film, while being forced into turbulent flow by the wiper blades, progresses down the inside body wall aided by gravity and the slots in the wiper blades.
During the course of flow through the heater system, some degree of evaporation takes place depending on the characteristics of the feed material and the inside wall temperature, in addition to the system pressure.
The non-evaporated fluid forming the bottom product flows out of the system continuously while the vapour is condensed either inside or outside the system depending on the design.
Why Thin Films? Thin films are created in Pope Wiped-Film Stills for a variety of reasons:.
1) Turbulence created by a rapidly moving wiper or controlled clearance blade greatly assists in heat transmission, thereby lowering the temperature required on the inside evaporator wall for a given system pressure.
2) A maximum surface area per unit volume of flow is generated facilitating rapid evaporation.
3) The liquid exposure time to the elevated wall temperature can be controlled within seconds or less.
This minimises product degradation of heat sensitive materials by controlling the wiper assembly speed.
4) High viscosity materials can be transported through the system for distillation or solvent stripping.
5) Pope slotted wiper blades promote plug flow with little back mixing.
This minimises dwell time distribution, ensuring that material flowing through the system has a uniform exposure to process conditions.
Pope adds design and construction excellence to the basic wiped film still process.
This has enabled Pope stills to sustain pressures down to one micron for either solvent stripping or molecular distillation.
Pope variable speed control of the wipers coupled with the ability to reverse rotation, allows an extremely wide variation of hold up time for the process fluids in the evaporator body.
Pope supplies either Teflon or carbon wiper blades with carbon preferred on applications over 200C.
Popes flexibility allows for parts to be manufacture in glass, stainless steel, Hastelloy, titanium, C-20 and other alloys.
To generate sound research and development data for molecular distillation and solvent stripping variables must be rigorously controlled - i.e feed rate, wiper revolution speed, still body temperature and pressure.
Pope provides the capability to control each of these variables to the degree required for efficient and repeatable processing.
Typical applications: the thin film evaporator/molecular still technique is a primary means of separation for many applications.
* Solvent stripping.
* Stripping monomer from polymer.
* Stripping free fatty acids from fats and oils.
* Concentrating or distilling heat sensitive pharmaceuticals, nutraceuticals and biomaterials.
* Distillation of polymers.
* Distillation of petroleum fractions.
* Reactives from solid catalysts.
* Concentration of fruit juices.
* Isolation of aromatic compounds.
* Deodorisation of oils.
* Removal of colours.
* Separations of waxes or silicones.
* Foods and flavours purifications. Request a free brochure from Labtex ...
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