Deposit Formation in Industrial Delayed Coker/ Visbreaker Heaters

In order to investigate fouling parameters indicative of the propensity of a furnace charge to form deposits in commercial coker/ visbreaker heater, 30+ processed furnace charge streams from more than 20 plant deposits were studied In general, about 90% of the deposits formed appear to be due to coke formation, and approximately 5% is due to the deposition of iron-containing materials For the investigation of furnace charge coking four important components were identified for various residues: colloids, resins, asphaltenes, and scarcely soluble asphaltenes 13 C-NMR and fluorescence spectroscopy were employed to further characterize the charges. Results indicate that from the colloids over the asphaltenes to the scarcely soluble asphaltenes the amount and the “ average condensation degree” of the respective aromatics increases, while the respective amount of longer chain (C⩽ 4) paraffines decreases. The amount of scarcely soluble asphaltenes correlates with the readiness of the residue to phase separate. The results are discussed on the basis of the solubility parameter concept. A titration method is suggested as a tool to characterize the potential of a residue to form coke precursors. Deposited iron seems to derive from non-sulfidic iron containing debris, dispersed in the furnace charge. In contrast, sulfur and vanadium present in the heater deposits appear to originate from residue molecules.