Wiped Film Still Components – Part II – Feed System

Feed systems can be complex or simple.  The object of a feed system is to meter material into the wiped film still at a controlled rate.  Feed rate is one of the big three levers the wiped film distiller has to control the results of a distillation.  So, feed systems and feed rate control are critical to reproducible distillations.

On small wiped film stills, a glass addition funnel is often used to slowly feed material into the still body.  These are generally driven by gravity, and the feed rate is set using a needle valve.  This type of control works well for lab trials and feasibility studies.  It is not a sufficient method for truly consistent work.

For this reason, on larger and more sophisticated systems a feed pump is used with a check valve.  The check valve allows the still system to be under vacuum while the feed container is at atmospheric pressure.

Pumping systems can consist of just a simple gear pump or diaphragm pump (or other appropriate style pump), or they can be paired with a Coriolis to meter the feed rate.  A Coriolis measures the feed rate and communicates back to a controller.  The controller speeds up or slows down the pump as needed to hold the set feed rate.  Having a consistent feed rate is critical to having consistent results on a pass through the still.

Picture 1 shows a system with a feed flask mounted on a gear pump.  Picture 2 shows a system with a diaphragm pump.

Pictures are courtesy of Pope Scientific, Inc.