stream a liquid product stream having a boiling point in the range of about 100 u00b0 f to about 900 u00b0 f the liquid product stream contains c 5 hydrocarbons up to hydrocarbons having boiling points of about 900 u00b0 f such aa naphtha stove oil gas oil and the like exiting from fractionator 70 via conduit 22 at a temperature in the range of about 200 u00b0 f to about 300 u00b0 f is a third stream a volatile components stream having a boiling point in the range of 240 u00b0 f boiling point of methane to about 390 u00b0 f the volatile components stream is cooled upon transfer through an over head condenser 74 to a temperature in the range of about 80 u00b0 f to about 150 u00b0 f the heated residuum stream is transferred via conduit 27 past valve 29 within conduit 27 to coker 76 coker 76 is maintained at a temperature at the outlet to conduit 32 in the range of about 750 u00b0 f to about 850 u00b0 f and preferably in the range of about 800 u00b0 f to about 820 u00b0 f the flow of the heated residuum stream in coker 76 is maintained at a rate to permit both coking and thermo cracking of the hydrocarbons in the residuum stream the hydrocarbons breakdown into volatile components having a boiling point in the range of methane to about.