Method for reducing fouling of coker furnaces

A method for reducing furnace fouling in a delayed coking process wherein at least one coker feed is supplied to a delayed coking unit comprised of a coker furnace, at least two coke drums and a coker fractionator comprising

• (a) supplying the feed to the bottom of the fractionator to produce an overhead stream, a bottoms stream and at least one intermediate stream from the fractionator;
• (b) increasing the aromaticity of the bottoms stream to produce a modified stream by combining with the bottoms stream upstream of the coker furnace a hydrotreated aromatic gas oil wherein the hydrotreated aromatic gas oil is formed from an unhydrotreated aromatic gas oil in a hydrotreater wherein the hydrotreater has a hydrotreater product and a hydrotreater feed, and wherein the hydrotreated aromatic gas oil has an aromatic carbon content of at least about X % according to the formula
• X=(A%)−[(0.02)·(hydrogen uptake in a hydrotreater)]
• where X is as least about 20% as measured by 13C NMR based on the total carbon content of the hydrotreated aromatic gas oil and A is the aromaticity of a unhydrotreated aromatic gas oil as measured by 13C NMR and is at least about 40%, where hydrogen uptake is [ρ659.5·(Δ hydrogen content (wt %) of the hydrotreater product and the hydrotreater feed)] and where ρ is the density (grams/cc) of the hydrotreater feed;
• (c) introducing the modified stream into the coker furnace;
• (d) heating the modified stream to a coking temperature in the coker furnace to produce a heated modified stream;
• and
• (e) transferring the heated modified stream from the coker furnace to a coke drum.

A method for reducing furnace fouling in a delayed coking process for producing anode or fuel grade coke wherein at least one coker feed is supplied to a delayed coking unit comprised of a coker furnace, at least two coke drums and a coker fractionator comprising

• (a) supplying the feed to the coker furnace without first passing the feed through the fractionator,
• (b) increasing the aromaticity of the feed to produce a modified stream by combining with the feed upstream of the coker furnace a hydrotreated aromatic gas oil, wherein the hydrotreated aromatic gas oil is formed from an unhydrotreated aromatic gas oil in a hydrotreater wherein the hydrotreater has a hydrotreater product and a hydrotreater feed, and wherein the hydrotreated aromatic gas oil has an aromatic carbon content of at least about X % according to the formula
• X=(A%)−[(0.02)·(hydrogen uptake in a hydrotreater)]
• where X is as least about 20% as measured by 13C NMR based on the total carbon content of the hydrotreated aromatic gas oil and A is the aromaticity of a unhydrotreated aromatic gas oil as measured by 13C NMR and is at least about 40%, where hydrogen uptake is [ρ659.5·(Δ hydrogen content (wt %) of the hydrotreater product and the hydrotreater feed)] and where ρ is the density (grams/cc) of the hydrotreater feed;
• (c) introducing the modified stream into the coker furnace;
• (d) heating the modified stream to a coking temperature in the coker furnace to produce a heated modified stream;
• and
• (e) transferring the heated modified stream from the coker furnace to a coke drum.