Process for separating ethylene polymers produced under high pressure and apparatus therefor

Claim 1

IN A PROCESS FOR THE CONTINUOUS GS-PHASE POLYMERIZATION OF ETHYLENE IN A OLYMERIZATION ZONE AT A TEMPERATURE BETWEEN 100* C. AND 400* C. AND A PRESSURE OF AT LEAST 500 ATMOSPHERES, THERBY PRODUCING A HOT REACTION MIXTURE COMPRISING MOLTEN POLYETHYLENE, UNREACTED ETHYLENE GAS AND LOW MOLECULAR WEIGHT BY-PRODUCTS PRODUCED IN SAID POLYMERIZATION, THE IMPROVEMENT WHICH COMPRISES DISCHARGING SAID HOT REACTION MIXTURE FROM SAID POLYMERIZATION ZONE, DECOMPRESSING SAID HOT REACTION MIXTURE TO A FIRST DECOMPRESSION PRESSURE BETWEEN THE PRESSURE IN SAID POLYMERIZATION ZONE AND 200 ATMOSPHERES, FEEDING SAID HOT REACTION MIXTURE AT SAID FIRST DECOMPRESSION PRESSURE INTO A FIRST SEAPRATOR MAINTAINED AT SAID FIRST DECOMPRESSION PRESSURE, SEPARATING THE MOLTEN POLYETHYLENE FROM THE BULK OF SAID UNREACTED ETHYLENE AND SAID BYPRODUCTS IN SAID FIRST SEPARATOR WHILE MAINTAINING IN THE BOTTOM PORTION OF SAID FIRS SEPARATOR A BODY OF MOLTEN POLYETHYLENE, REMOVING FROM THE UPPER PORTION OF SAID FIRST SEPARATOR THE SEPARATED, HOT COMPOSITE OF UNREACTED ETHYLENE GAS AND BY-PRODUCTS, SAID HOT REACTION MIXTURE BEING FED INTO THE UPPER PORTION OF SAID FIRST SEPARATOR AT VERY HIGH FLOW VELOCITY HORIZONTALLY AND TANGENTIALLY AGAINST THE INNER WALL OF THE UPPER PORTION OF SAID SEPARATOR, WHICH INNER WALL IS CYLINDRICAL, THEREBY FACILITATING THE MAINTENACNE OF A SUBSTANTIALLY CONSTANT LEVEL OF SAID BODY OF MOLTEN POLETHYLENE IN SAID FIRST SEPARATOR AND PREVENTING POLYETHYLENE FROM BEING CARRIED FROM SAID FIRST SEPARATOR WITH SAID HOT COMPOSITE, COOLING SAID REMOVED, HOT COMPOSITE IN A COOLING ZONE AT SAID FIRST DECOMPRESSION PRESSURE, DECOMPRESSING THE COOLED COMPOSITE OF ETHYLENE GAS AND BY-PRODUCTS TO A PRESSURE OF ABOUT ONE ATMOSPHERE, SAID COOLING IN SAID COOLING ZONE AND SAID DECOMPRESSION T ABOUT ONE ATMOSPHERE TOGETHER LOWERING THE TEMPERATURE OF SAID COMPOSITE AT ABOUT ONE ASTMOSPHERE TO A TEMPERATURE BELOW O* C. AND ABOVE THE VOLATILIZATION TEMPERATURE OF ETHYLENE AT ABOUT ONE ATMOSPHERE, SEPARATING AT SAID LAST-MENTIONED TEMPERATURE AND AT ABOUT ONE ATMOSPHERE THE ETHYLENE GAS FROM SAID BYPRODUCTS, THE LATTER BEING AT THIS STAGE OILY AND SEMI-SOLID, DISCHARGING SAID SEPARATED, COOLED, ETHYLENE GAS FROM SAID SECOND SEPARATOR, RECOMPRESSING SAID SEPARATED ETHYLENE GAS, WHICH IS ESSENTIALLY FREE FROM SAID BY-PRODUCTS, TO SAID POLYMERIZATION PRESSURE AND RETURNING THE RECOMPRESSED, PURIFIED ETHYLENE TO SAID POLYMERIZATION ZONE, REMOVING SAID MOLTEN POLYETHYLENE FROM THE BOTTOM PORTION OF SAID FIRST SEPARATOR WHILE MAINTAINING SAID BODY OF MOLTEN POLYETHYLENE IN SAID BOTTOM PROTION OF SAID FIRST SEPARATOR, DECOMPRESSING SAID REMOVED, MOLTEN POLYETHYLENE TO ABOUT ONE ATMOSPHERE, AND SEPARATING IN A THIRD SEPARATOR SAID MOLTEN POLYETHYLENE AND ETHYLENE GAS RELEASED THEREFROM BY SAID LAST-MENTIONED DECOMPRESSION.