Patent ID: 7578929
Filing Date: 2009-08-25
Classification: C10G

Abstract:
1. A process for cracking a heavy hydrocarbon feedstock using a furnace having at least a convection section and a radiant section, said process comprising: (a) prior to feeding said heavy hydrocarbon feedstock to said radiant section, heating said heavy hydrocarbon feedstock to form a heated feedstock; (b) introducing steam to said heated feedstock; (c) before or after step (b), introducing at least one of liquid hydrocarbon and water to said heated feedstock; (d) at least partially flashing the heated feedstock from steps (b) and (c) to form a vapor phase and a liquid phase; (e) feeding at least a portion of said vapor phase to said radiant section to crack at least a portion of hydrocarbons in said vapor phase; (f) varying the amount of said steam and the amount of said at least one of liquid hydrocarbon and water with a control responsive to at least one operating parameter of said process; (g) holding substantially constant the sum of the rate of introduction of steam and the rate of introduction at least one of said liquid hydrocarbon and water to maintain the ratio of said separated vapor phase to said separated liquid phase substantially constant; and (h) providing secondary dilution steam to a superheater section in said convection section and introducing said secondary dilution steam into said heated feedstock after step (c), and controlling the temperature of said secondary dilution steam by controlling the flow rate of water from a desuperheater into said secondary dilution steam.