Fractionating column with removable trays

Claim 1

A FRACTIONATING COLUMN COMPRISING: A CLOSED VERTICAL SHELL HAVING A TOP OPENING WITH A REMOVABLE, FLUID-TIGHT CLOSURE AND BEING ADAPTED TO MAINTAIN A PRESSURE DIFFERENTIAL BETWEEN THE INTERIOR AND EXTERIOR THEREOF; A PLURALITY OF AT LEAST THREE TRAY SECTIONS WITHIN SAID SHELL FORMING A VERTICAL SERIES OF CONTACT STAGES, EACH SECTION HAVING A TRAY DECK WITH PASSAGEWAYS FOR THE UPWARD FLOW OF VAPOR AND THE DOWNWARD FLOW OF LIQUID THROUGH THE DECKS ARRANGED TO EFFECT INTIMATE CONTACT BETWEEN SAID LIQUID AND VAPOR WITH A PRESSURE DROP BETWEEN STAGES, SAID TRAY SECTIONS BEING SHAPED TO PERMIT UNIMPEDED VERTICAL MOVEMENT THEREOF AS SEPARATE UNITS THROUGH THE SHELL TO THE TOP THEREOF AND THROUGH SAID TOP OPENING UPON REMOVAL OF SAID CLOSURE; A CLOSED ANNULAR WALL ON EACH TRAY SECTION EXTENDING IN SEALED RELATION FROM THE DECK THEREOF VERTICALLY TO A CORRESPONDING ANNULAR PORTION ON AN ADJACENT SECTION, SAID WALLS ENCLOSING LIQUID AND VAPOR CONTACT SPACES WITHIN THEMSELVES, AND THE WALL AND DECKS OF AT LEAST A PLURALITY OF LOWER SECTIONS HAVING CLEARANCES WITH RESPECT TO THE SHELL TO DEFINE A COMMON OUTER SPACE BETWEEN THE SHELL AND SAID LOWER SECTIONS EXTENDING VERTICALLY THROUGH THE HEIGHT OF SEVERAL TRAY SECTIONS; AN ANNULAR SEAL BETWEEN EACH ANNULAR WALL AND ITS CORRESPONDING ANNULAR PART OF THE ADJACENT SECTION ARRANGED TO PREVENT THE OUTWARD FLOW OF VAPOR FROM SAID CONTACT SPACES INTO SAID OUTER SPACE, EACH SEAL COMPRISING A TROUGH ADAPTED TO RETAIN A POOL OF LIQUID THAT CONTACTS THE INNER AND OUTER SIDES OF THE ANNULAR WALL, WHEREBY SAID SEALS CAN BE ESTABLISHED BY SUCCESSIVELY LOWERING TRAY SECTIONS THROUGH THE SHELL AND SAID CONTACT SPACES CAN BE MAINTAINED AT PROGRESSIVELY DIFFERENT PRESSURES INDEPENDENT OF THE PRESSURE IN SAID OUTER SPACE; SEAL MEANS BETWEEN THE LOWERMOST TRAY SECTION AND THE SHELL CLOSING OFF THE BOTTOM OF SAID OUTER SPACE, WHEREBY THE PRESSURE IN SAID OUTER SPACE IS ISOLATED FROM THE PRESSURE IMMEDIATELY BENEATH THE TRAY DECK OF SAID LOWERMOST TRAY SECTION; AND A VAPOR PASSAGEWAY INTERCONNECTING SAID OUTER SPACE WITH ONE OF THE UPPER CONTACT SPACES, WHEREBY THE PRESSURE IN SAID OUTER SPACE WILL BE THAT OF SAID ONE UPPER CONTACT SPACE.