insulator to prevent or minimize coking inside the feed nozzle conduit 14 has a gas outlet nozzle 38 disposed in a diagonal direction set at an angle such that steam will emerge from nozzle 38 and be directed towards the inner wall of transfer line reactor 2 thereby forming a layer of steam that will cover at least a portion of the inner wall the steam cover will shield the inner wall of the transfer line reactor from carbonaceous deposits which result from cracking of the hydrocarbon feed concentric conduits 15 and 14 terminate in outlet nozzle 26 disposed vertically and upwardly so that the hydrocarbon liquid and the remaining portion of the steam emanate as an upwardly directed stream although no detail is shown on the nozzle tip there are various well known designs that permit the steam to provide good feed atomization the hydrocarbon liquid may mix with the steam at the exit of the nozzle or the tip of the nozzle or the inner conduits may be shorter than the outer conduit so that the liquid and steam may mix before exiting from nozzle 26 preferably the transfer line reactor comprises more than one pair of concentric inlet conduits disposed in spaced relation parallel to the longitudinal axis of transfer line reactor so as to stage the introduction of the hydrocarbonaceous feed into the transfer line reactor returning to fig1 conduits 16 18 20 22 and 24 are each comprised of a smaller inner concentric conduit and similar nozzle systems as the ones described for conduit 14 although six pairs of inlet conduits are shown in fig1 the number of pairs of inlet conduits is not critical and they may be more or less inlet conduits disposed around the circumference of the transfer line.