Olefin production utilizing whole crude oil/condensate feedstock and selective hydrocracking

1 . In a method for operating an olefin production plant that employs a pyrolysis furnace to severely thermally crack hydrocarbon containing material for subsequent processing of the thus cracked product in said plant which method of plant operation includes 1) providing at least one of whole crude oil and natural gas condensate as said hydrocarbon containing material, 2) submitting said whole crude/condensate feed to a vaporization step wherein said feed is substantially vaporized, and 3) feeding said substantially vaporized feed to said pyrolysis furnace, said plant further employing an oil quench step on said cracked material product to form a pyrolysis gas oil stream, the improvement comprising passing at least part of said pyrolysis gas oil stream to a hydrocracking step, hydrocracking said pyrolysis gas oil to form a hydrocracked product, and returning at least part of said hydrocracked product as feed to said vaporization step.

2 . The method of claim 1 wherein a liquid stream is removed from said vaporization step and passed as feed to said hydrocracking step.

3 . The method of claim 1 wherein said pyrolysis gas oil stream boils in the range of from about 380 to about 700 F.

4 . The method of claim 1 wherein said hydrocracking step is carried out at a temperature of from about 640 to about 840 F, pressure of from about 1,200 to about 5,000 psig, weight hourly space velocity of from about 0.1 to about 5, and hydrogen flow of from about 100 to about 200 cubic meters per ton of hydrocarbon feed.