PROCESS FOR CRACKING ASPHALTENE-CONTAINING FEEDSTOCK EMPLOYING DILUTION STEAM AND WATER INJECTION

摘要

A process for reducing the rate of increase in pressure drop across a furnace convection section, the furnace convection section having a temperature profile. The process includes the steps of establishing a ratio of total dilution H<SUB>2</SUB>O to feedstock for the system, injecting a first portion of the total dilution H<SUB>2</SUB>O in the form of water into the convection section of the furnace, injecting a second portion of the dilution H<SUB>2</SUB>O in the form of steam into the convection section of the furnace, wherein a ratio of dilution H<SUB>2</SUB>O in the form of water to dilution H<SUB>2</SUB>O in the form of steam is established and varying the temperature profile across the convection section of the furnace by adjusting periodically the ratio of dilution H<SUB>2</SUB>O in the form of water to dilution H<SUB>2</SUB>O in the form of steam. A similar technique is conducted during decoking to remove asphaltene coke starting from the lower convection section upward. This upward decoking is accomplished by initially using more H<SUB>2</SUB>O in the form of water, then as the decoke proceeds reducing H<SUB>2</SUB>O in the form of water while increasing H<SUB>2</SUB>O in the form of steam.