Process for cracking a heavy hydrocarbon feedstream

Abstract

A process for cracking a hydrocarbon feedstream containing non-volatile components in a hydrocarbon cracking furnace having upper and lower convection heating sections within a flue of the furnace, a radiant heating section downstream of and connected to said lower convection heating section, a transfer line exchanger downstream of and connected to said radiant heating section, a furnace box containing furnace burners and said radiant heating section, and a vapor/liquid separator vessel connected between the upper and lower convection heating sections, the process comprising (a) passing said hydrocarbon feedstream into said upper convection section to heat said hydrocarbon feedstream to a first temperature sufficient to flash at least a portion of the hydrocarbons within said hydrocarbon feedstream into a vapor phase to form a vapor/liquid stream; (b) passing said vapor/liquid stream out of said upper convection section and into said vapor/liquid separator to separate said vapor/liquid stream into a hydrocarbon-containing vapor phase and a hydrocarbon-containing liquid phase within said vapor/liquid separator; (c) collecting said liquid phase into a bottoms liquid within said vapor/liquid separator; (d) passing said vapor phase into said radiant heating section and cracking hydrocarbons in said vapor phase to form an olefins-containing effluent stream; and (e) periodically injecting an air-steam mixture into said convection heating section, then through said vapor/liquid separator to incinerate coke formed and passing an incinerated coke residue/air-steam mixture so-formed between the furnace burners within the furnace box.