to a desired capacity with coke deposits 79 the time required to fill coker 76 is in the range of about 18 hours to about 30 hours and varies depending upon both the capacity of coker 76 composition of the residuum stream and process conditions under which coker 76 is run when a desired amount of coke 79 has been formed in coker 76 valve 29 is closed the heated residuum stream can be diverted to a second coker via conduit 25 while coker 76 is being cleaned as hereinafter described shortly after conduit 27 to coker 76 is closed e g within above five minutes a process involving introducing a stripping steam e g steam at a temperature that gives rise to a pressure thereof of about 140 psig and at a rate in the range of about 5 to 15 000 pounds per hour via conduit 30 into coker 76 is initiated this process of introducing a stripping stream with valve 78 open to conduit 24 and fractionator 70 is continued depending upon the amount of coke present for about 10 to about 30 minutes then with the process continuing valve 78 is turned closing 24 to fractionator 70 but opening conduit 34 to a coker blow down system 80 the material which passes from coker 76 through valve 78 into conduit 34 comprises hydrogen gas hydrogen sulfide water c 1 c 5 hydrocarbons and occasionally though undesirably c 7 hydrocarbons this material initially at a temperature in the range of about 600 u00b0 f to about 800 u00b0 f and at a pressure in the range of about 30 psig to about 80 psig is cooled to a temperature in the range of about.