Method for reducing coke and oligomer formation in a furnace

Abstract

A method for reducing the formation of coke and oligomers in the convection section of a hydrocarbon pyrolysis furnace, the method comprising reducing the partial pressure of the hydrocarbon feed to the furnace before that feed is mixed with dilution steam.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]This invention relates to the reduction of the formation of coke and oligomers in a pyrolysis furnace. More particularly, this invention relates to the reduction of coke and oligomer formation in the convection section of a pyrolysis furnace.[0003]2. Description of the Prior Art[0004]Thermal cracking of hydrocarbons is a petrochemical process that is widely used to produce olefins such as ethylene, propylene, butenes, butadiene, and aromatics such as benzene, toluene, and xylenes. In an olefin production plant, a hydrocarbonaceous feedstock such as ethane, naphtha, gas oil, condensate, residuum (resid) and other fractions of whole crude oil, or even whole crude oil itself is mixed with what is termed “dilution steam” which serves as a diluent to keep the hydrocarbon molecules separated to facilitate the cracking function.[0005]This mixture of hydrocarbons and dilution steam, after preheating of same, is subjected to hyd...

AI Technical Summary

Benefits of technology

[0015]Pursuant to this invention, coke and oligomer formation in the convection section coils of a pyrolysis furnace can be reduced, if not eliminated, by reducing the partial pressure of the feed to the pyrolysis furnace before and / or while it is preheated, and before it is mixed with the total operating amount of dilution steam.

Problems solved by technology

This is most undesirable because coke can plug a furnace coil thus hindering the operation of the furnace even to the extent of shutting the furnace down altogether.

Coke cannot readily be burned out of convection tubes.

Further, coke can cause premature failure of furnace tubes, tube bends, down stream piping bends.

Although the radiant section coils of current furnaces are built to resist coke deposition and to have coke deposits physically removed from the interior thereof, the convection section coils of many current furnaces were not designed either to resist coke deposition or to have coke readily cleaned there from once it has deposited therein.

It would be prohibitively expensive to physically retro fit many current furnaces so that their convection section coils can more readily resist the formation of coke deposits therein, and can have coke cleaned therefrom in the manner of their radiant section coils.

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