Abstract: A feed nozzle for introducing steam and a heavy petroleum hydrocarbon into a reactor, including a nozzle body having a cylindrical inner steam conduit; and having a annular outer heavy petroleum hydrocarbon conduit, a first nozzle tip fixedly attached to the outlet end of the inner steam conduit, for the passage of the steam out of the inner steam conduit and into the heavy petroleum hydrocarbon, resulting in a mixture of steam and heavy petroleum hydrocarbon; the hemi-spherical outlet end having a row comprising a plurality of holes therein for the passage of the steam out of the inner steam conduit and into the heavy petroleum hydrocarbon passing through the outer heavy petroleum hydrocarbon conduit, resulting in a mixture of steam and heavy petroleum hydrocarbon; a second nozzle tip fixedly attached to the outer heavy petroleum hydrocarbon conduit, for passage of the mixture of steam and heavy petroleum hydrocarbon out of the feed nozzle assembly; the second nozzle tip being adapted to atomize the mixture