Abstract: Delayed coking is an important technology of heavy oil processing. The furnace is the core device of delayed coking units. Taking the delayed coking furnace of a domestic petrochemical enterprise as an example, the influence of working condition changes on the operation of the radiation section of the furnace was studied by simulation. The rule about the variation law of key operating parameters along the axial direction of the furnace tubes was obtained. On this basis, the coking law of furnace tubes was also studied. The results showed that the parameters including velocity of flow, vaporization rate, temperature, conversion rate of fluid and thickness of coking layer in furnace tube gradually increased along the length of the furnace tube increased before the third steam injection point. The velocity of fluid and vaporization rate of fluid rapidly increased, temperature and conversion growth rate of fluid decreased, especially the thickness of coking layer first decreased and then increased along the length of the furnace tube increased after the third steam injection point. The reason lied in the fact that the intensifying effect of temperature rise on coking gradually offset the mitigating effect of speed reduction on coking. When the fluid temperature was similar, a high recycle ratio was more effective than a low recycle ratio in slowing down coke formation in furnace tubes.

Key words: delayed coking, furnace, coking, simulation, recycle ratio