Arrangement for multistage vacuum molecular distilling

Claim 1

In an arrangement for establishing a multi-stage vacuum and molecular distillation process using a wiped-off film, an elongated, vertically disposed evaporator vessel supported for rotation about a first longitudinal axis thereof and having a convex outer surface; means including condenser means surrounding first, second and third successively lower regions of the convex outer surface of the evaporator vessel to define therebetween first, second and third vacuum distillation stages; first and second annular elements individually affixed to the outer surface of the evaporator element to define interfaces between the first and second vacuum stages and the second and third vacuum stages, respectively; first, second and third elongated wiping means extending longitudinally along the outer surface of the evaporator means in the respective first, second and third vacuum stages, the first, second and third wiping means respectively including first, second and third entraining rods, the first and second rods having respective lower and upper ends secured to the first annular element, the second and third rods having respective lower and upper ends secured to the second annular element, whereby the evaporator vessel, the annular elements and the entraining means form a unitary first assembly rotatable about the first axis; means disposed in each of the first and second annular elements for effecting a controlled flow of a fluid therethrough from the lower end of the next-higher vacuum stage to the upper end of the next-lower vacuum stage so that the controlled flow of such fluid during a rotation of the first assembly about the first axis provides a rotary vacuum seal between the associated vacuum stages; means for introducing a first liquid to be distilled to the upper end of the first wiping means to be entrained thereby, whereby portions of the first liquid flow downwardly and alternately through the entraining rods and the effecting means of the annular elements; means for rotating the first assembly about the first axis so that the controlled movement of the first liquid through the effecting means of the annular elements provides liquid rotary vacuum seals among the first, second and third vacuum stages; and means coupled to the condensing means for individually evacuating the first, second and third vacuum stages to successively higher degrees.