The simplest method of concentrating a solution makes use of jacketed pans. Such a type of evaporator is particularly suitable when small quantities are to be handled. In an open/jacketed pan evaporator, condensing steam is fed to a jacket for evaporating a part of the solvent. Pan is made of a single sheet of metal (for small sizes) or several sheets joined by welding / brazing. A jacket is welded to the pan. The jacket is provided with a steam inlet at the top, while a condensate drain is provided at its bottom. The pan is provided with an outlet at the bottom for draining its contents. The jacket is usually constructed out of mild steel, while the pan is constructed out of mild steel, stainless steel, copper or aluminium as per process requirements.
The solution to be concentrated is taken into the pan and steam is admitted in the jacket.
Evaporation is carried out for a predetermined time to achieve a desired concentration level.
The thick liquor is then drained from the outlet.
Fig. Jacketed pan evaporator