Patent ID: 7422663

Claim:
A multi-stage distillation apparatus includes a plurality of evaporators connected in series for staged operation in a rising film evaporation process wherein the evaporators are disposed in a compact concentric arrangement, the apparatus comprising: a first stage evaporator of ring shell and tube construction including a first annular vertical tube bundle, having tubes supported and sealed by a first upper tubesheet and a first bottom tubesheet, an external wall and an internal wall enclosing the first tube bundle, said internal wall having an upward extension over the upper tubesheet and the external wall having a downward extension adjacent the bottom tubesheet and fastened to a base, the base including a feed chamber communicating through the bottom tubesheet with the tubes of the first tube bundle for supplying the tubes with a flow of undistilled water for partial vaporization, means for conducting a heated liquid against the tubes of the first tube bundle and partially vaporizing the undistilled water therein, and the first stage evaporator having a first stage vapor chamber above the upper tubesheet and in open communication with the tubes of the first tube bundle for receiving therefrom heated water vapor and residual undistilled water, the upward extension of the internal wall directing the heated vapor to a subsequent stage evaporator tube bundle; and a final stage evaporator, being also a pre-final stage condenser, including a final cylindrical vertical tube bundle, having tubes supported and sealed by a final upper tubesheet and a final bottom tubesheet, the final bottom tubesheet carrying a final stage floating head connected to receive, by gravity feed means from a final stage vapor chamber, residual undistilled water vacuumed from a prior stage evaporator to the final stage vapor chamber, the final floating head communicating with the tubes of the final stage evaporator cylindrical tube bundle for delivering said residual undistilled water thereinto, the final upper tubesheet having a diameter at least 30% larger than the final bottom tubesheet, the final upper tubesheet defining a lower wall of the final stage vapor chamber, in open communication with the final tube bundle for receiving therefrom additional water vapor for condensation to condensate and residual undistilled water for discharge from the distillation apparatus, and a final external armor shell surrounding the final cylindrical tube bundle and engaging the internal wall of an adjacent evaporator to direct heated vapor from the adjacent evaporator to pass through the final cylindrical tube bundle for heating the tubes and causing partial condensation of the heated vapor on the tubes of the final stage evaporator with said partial vaporization of the residual undistilled water in the tubes of the final tube bundle, and further including means for drawing off condensate from the partially condensed vapor from the final stage evaporator.