(118c) Prediction of Propensity to Fouling in Fluid Cokers

Fluid cokers are used to upgrade heavy oils to lighter oils through thermally cracking. Heavy oil is sprayed into a fluidized bed of hot coke particles that are moving downward to a stripper and then to a burner were the particles are reheated. Fouling of the stripper internals by coke deposits is a serious problem that limits the operability of the coker. It is surmised that fouling is caused when wet agglomerates, which are formed with imperfect spray nozzles, break up on the stripper internals, smearing them with their liquid. If an agglomerate formed at the spray level is wet enough and large enough, it can survive all the way to the stripper. It is believed that the propensity to fouling is directly related to the flowrate of liquid reaching the stripper level within agglomerates. The flowrate of liquid reaching the stripper level was predicted through the combination of an experimental study of agglomerate formation at the spray level, a model of the heat transfer, mass transfer and reaction processes occurring within a reacting agglomerate, and a model of the solids residence time distribution between spray and stripper levels.