Abstract: The present subject matter relates to a feed nozzle assembly 100 for atomizing a heavy hydrocarbon feed by mixing the hydrocarbon feed with a diluent and an atomizing media. The feed nozzle assembly 100 includes at least one primary mixing chambers 101 for receiving the liquid hydrocarbon feed and the diluent to create a primary mixture. The primary mixture is than forwarded to a secondary mixing chamber 102. The secondary mixing chamber extends to a tertiary mixing chamber 103. A steam inlet 110 is provided to inject streams of steam to the secondary mixing chamber 102 and to the tertiary mixing chamber 103 through a first opening and a second opening, respectively, located within the steam inlet 110.