GB695560A - Improvements relating to the degassing and devolatilising of low vapour pressure liquids - Google Patents

Abstract

Liquids of low vapour pressure are degassed prior to high-vacuum distillation by heating the liquid in a container having a <PICT:0695560/III/1> vapour-exit attached to the lower end of a vertical tube which is open at the upper end, both the container and the vertical tube being wholly disposed inside an evacuated vessel; the tube is cooled over at least a part of its length, thus acting as a reflux condenser, and the gases escape from the upper end of the tube into the enclosing vessel from which they are continuously withdrawn by the evacuating means. The necessity for apparatus with hot vacuum seals is thereby obviated. In the Figure, the liquid to be degassed is charged into container C; and the vertical tube D is then attached to it by means of joint C1. The upper end of tube D is cooled by means of a cooling liquid flowing through pipe E. The container C and tube D are suspended inside cylindrical vessel A by passing the ends of pipe E through ring E1, which is then supported on a flange at the top of vessel A. The lower part of vessel A contains a grease A1 of very low vapour pressure, which is heated and maintained in the liquid condition by electric heater B, the temperature being measured by thermo-couple T. The container C is almost wholly immersed in the heating medium A1. Vessel A is evacuated by diffusion pump G and by a backing pump (not shown); a cold trap F being provided between the diffusion pump and the vessel A. The occluded gas and the lightest volatile components of the liquid are driven out of the liquid, and find their way into vessel A through the upper end of tube D. These lightest volatile components are condensed in trap F; while the gas is sucked away by the pumps. The less volatile components of the liquid, which it is desired to separate by subsequent high-vacuum distillation, condense on the cooler portions of tube D, and flow back to the container C. The precise degree of separation of the volatile components is determined both by the temperature to which the liquid is heated and the extent to which the tube D is cooled.