Decoking of pebbles in pebble heater cracking of hydrocarbons

Claim 1

IN A PROCESS FOR CONVERSION OF HYDROCARBONS IN A PEBBLE HEATER IN WHICH REFRACTORY HEAT CARRYING PEBBLES ARE SUCCESSIVLEY HEATED TO A TEMPERATURE ABOVE CONVERSION TEMPERATURE IN THE RANGE OF 1500 TO 2500* F. IN AN UPPER CHAMBER BY CONTACT WITH HOT COMBUSTION GAS, GRAVITATED TO A LOWER CHAMBER IN WHICH THEY ARE CONTACTED WITH A STREAM OF HYDROCARBON UNDER CRACKING CONDITIONS SO AS TO DEPOSIT COKE ON SAID PEBBLES AND GRADUALLY CAUSE PEBBLE AND COKE AGGLOMERATES TO FORM, AND THEN SAID PEBBLES ARE TRANSFERRED TO SAID UPPER CHAMBER FOR REHEATING; THE METHOD OF REMOVING SAID COKE FROM SAID PEBBLES WHICH COMPRISES DISCONTINUING THE FLOW OF HYDROCARBON THROUGH SAID LOWER CHAMBER; AND PASSING THERETHROUGH A STREAM OF NON-DELETERIOUS, NON-COKING GAS UNDER THE CONDITIONS IN THE REACTION ZONE WHILE SIMULTANEOUSLY CONTACTING THE PEBBLES IN SAID UPPER CHAMBER WITH AN OXYGEN-CONTAINING GAS IN EXCESS OF THAT PRESENT IN SAID UPPER CHAMBER PRIOR TO DISCONTINUING THE FLOW OF HYDROCARBON TO THE LOWER CHAMBER SO AS TO BURN COKE THEREFROM; CONTINUING THE FLOW OF SAID LAST-NAMED GAS AND SAID PEBBLES AT LEAST UNTIL THE MAJOR PORTION OF THE COKE ON SAID PEBBLES HAS BEEN REMOVED; AND THEREAFTER DISCONTINUING THE FLOW OF SAID GASES AND RESUMING SAID HYDROCARBON CONVERSION AND HEATING OF SAID PEBBLES.