Olefin production utilizing whole crude oil

In a method for operating an olefin production plant that employs a pyrolysis furnace to severely thermally crack hydrocarbon molecules for the subsequent processing of said cracked molecules in said plant, said furnace having in its interior a convection heating section and a separate radiant heating section, said radiant heating section being employed for said severe cracking, the improvement comprising providing whole crude oil as the primary feedstock to said furnace, preheating said feedstock to a temperature of from about 500° F. to about 750° F. to form a mixture of vaporous and liquid hydrocarbons, collecting said mixture in a vaporization/mild cracking unit, in said unit separating said vaporous hydrocarbons from said liquid hydrocarbons, passing said vaporous hydrocarbons to said radiant heating section, retaining said liquid hydrocarbons in said unit, introducing steam into said unit to mix with said liquid hydrocarbons in said unit to dilute said liquid hydrocarbons and heat same to a temperature of from about 800° F. to about 1,300° F. thereby forming additional vaporous hydrocarbons, continuing the retention of liquid hydrocarbons in said vaporization/mild cracking unit until said liquid hydrocarbons are converted to vaporous hydrocarbons by at least one of vaporization and mild cracking, and removing said additional vaporous hydrocarbons to said radiant heating section.