Control process and apparatus for continuously operating superatmospheric distillation

Claim 1

IN A PROCESS FOR THE CONTINUOUS DISTILLATION OF A STREAM OF INTAKE MIXTURE WHICH IS CARRIED OUT AT SUPERATMOSPHERIC PRESSURE IN A MULTITRAY DISTILLATION COLUMN HAVING BOTH RECTIFYING AND STRIPPING SECTIONS, WHEREIN THE OVERHEAD VAPORS ARE CONDENSED IN A CONDENSER AND COLLECTED IN AN ACCUMULATOR; WHEREIN BOTH REFLUX IN THE UPPER PORTION AND RE-EVAPORATION IN THE BOTTOM PORTION OF THE COLUMN ARE USED; AND WHEREIN THE AMOUNT OF REFLUX, THE DEGREE OF RE-EVAPORATION, THE TOP PRODUCT FLOW AND THE BOTTOM PRODUCT FLOW ARE CONTROLLED SUCH THAT THE TOP PRODUCT ACCUMULATOR LEVEL AND THE BOTTOM PRODUCT LEVEL IN THE COLUMN ARE ADJUSTED TO PREDETERMINED RESPECTIVE LEVELS AND THE DESIRED QUALITY OF THE SEPARATION IS ATTAINED, THE IMPROVEMENT COMPRISING: ALLOWING THE PRESSURE IN THE COLUMN TO FREELY ADJUST ITSELF BETWEEN THE MAXIMUM AND MINIMUM PERMISIBLE OPERATING PRESSURES FOR THE COLUMN; CIRCULATING THE MAXIMUM POSSIBLE QUANTITY OF COOLING MEDIUM THROUGH THE CONDESNER, REDUCING THE AMOUNT OF THE COOLING MEDIUM CIRCULATED ONLY WHEN THE COLUMN PRESSURE EQUALS THE LIMITS OF THE PERMISSABLE OPERATING RANGE; PREHEATING THE INTAKE MIXTURE TO THE DISTILLATION COLUMN WITH THE MAXIMUM POSSIBLE QUANTITY OF HEAT, REDUCING SAID PREHEATING ONLY WHEN THE TRAYS OF THE RECTIFYING SECTION OF THE COLUMN OVERLOAD; AND, DECREASING THE CIRCULATION OF CONDENSER COOLING MEDIUM WHENEVER THE MAXIMUM PERMISSIBLE LOAD ON THE TRAYS OF THE STRIPPING SECTION OF THE DISTILLATION COLUMN IS EXCEEDED.