Pictured here is a borosilicate evaporator. This complex unit is the heart of a wiped film evaporator and enables the distillation of heat sensitive materials to proceed under low pressure with a short residence time. It is also referred to as a thin film evaporator or short path evaporator; the internal coil condenser's close relation to the heated outer oil jacket is the "short" in "short path". A wiper blade assembly will be mounted above this unit, with wiper blades extending into and around the annular space between the inner condenser and the heated jacket.
The concentrate is taken off at the side arms, which are jacketed for heat control to accommodate the often viscous product. The process can be run continuously.
There is a good general description of the process in a reprint from the February 1997 edition of Chemical Processing, along with a description of the kinds of typical applications.
Below we thought we'd illustrate the separate jackets surrounding the main chamber by filling them with colored water:
Shows the heated oil jacket. This inner wall provides the heated surface against which the inserted wiper blades will interact.
This jacket helps control the often viscous heavier residues.
Shows the secondary heating path, which extends up into the coiled condenser. It is the distance between the coil and the oil jacket that is the "short path". At the bottom, the viscous take-off is expedited by this heated jacketed circuit. This is typically the target product.
The main chamber is often evacuated to reduce the vapor pressure / boiling point.
This is a definitive old school glassblowing challenge, work we continue to pursue. Will it ever be possible to 3D print glass like this? We'd like to think that improbable....