Cracking of hydrocarbons

Claim 1

IN A PROCESS FOR THE PRODUCTION OF GASEOUS OLEFINS BY THERMALLY CRACKING LIQUID HYDROCARBONS IN A FLUIDIZED LAYER OF GRANNULAR SOLIDS AT A TEMPERATURE OF FROM ABOUT 550*C. TO 850*C. WITH SEPARATION IN A CYCLONE OF THE BULK OF THE SOLIDS ENTRAINED IN THE EFFLUENT GASEOUS AND VAPOROUS REACTION PRODUCTS, SAID SEPARATED SOLIDS BEING RETURNED FROM SAID CYCLONE TO SAID FLUIUDIZED LAYER, THE IMPROVEMENT WHICH COMPRISES: COOLING AND WASHING SAID EFFLUENT REACTION PRODUCTS LEAVING SAID CYCLONE AND STILL CONTAINING RESIDUAL FINE-GRAINED SOLIDS IN A QUENCHING ZONE WITH A LIQUID HYDROCARBON FRACTION OF SAID EFFLUENT REACTION PRODUCTS WHICH BOIL ABOVE ABOUT 250*C. AND WHICH ACTS AS A WASH LIQUID FOR ABSORPTION OF SAID RESIDUAL SOLIDS FROM SAID EFFLUENT REACTION PRODUCTS; RECOVERING SAID EFFLUENT REACTION PRODUCTS FREED OF SAID RESIDUAL SOLIDS FROM SAID QUENCHING ZONE; SEPARATELY RECOVERING SAID HYDROCARBON WASH LIQUID CONTAINING SAID RESIDUAL SOLIDS FROM SAID QUENCHING ZONE; AND LEADING AT LEAST PART OF SAID WASH LIQUID FROM SAID QUENCHING ZONE INTO SAID FLUIDIZED LAYER AFTER FIRST DISCHARGING THEREFROM AT LEAST PART OF SAID RESIDUAL SOLIDS, THE QUANTITY OF RESIDUAL SOLIDS SEPARATED FROM SAID WASH LIQUID BEING SUFFICIENT TO MAINTAIN AT LEAST 50% BY WEIGHT OF THE GRANULAR SOLIDS IN SAID FLUIDIZED LAYER WITHIN GRAIN SIZE OF 100 TO 3000 MICRONS.