Analysis of syngas cooler fouling from asphaltene gasification

• Syngas fouling deposits from asphaltene gasification are analyzed.
• First fouling layer formed as a result of impact of pure Ni3S2 on the tube surface.
• V2O3 particles surrounded by condensed Ni3S2 get deposited due to high viscosity.
• The condensation of sodium sulfite at T < 800 °C adds to the fouling formation.

Vanadium (V) and nickel (Ni) are the most abundant and troublesome metals present in Athabasca oil sands asphaltenes which are formed during the primary upgrading of bitumen. Asphaltenes consist of iron, phosphorus, calcium, sodium, and aluminum in noticeable amounts in addition to poly aromatic hydrocarbons, sulfur, nitrogen and oxygen. During gasification of asphaltene, a small amount of carbon in the form of soot, along with some of the inorganic components in the feed, exits the gasifier as particulates with the syngas. If these V, Ni or any other metal species do not get encapsulated by soot, these would create fouling/erosion issues at the downstream of the gasifier as the syngas is cooled down in the syngas cooler tubes. The present study focuses on the analysis of the ash deposits collected from an industrial syngas cooler attached to an asphaltene gasifier. First half of the tube length was affected by high temperature corrosion, whereas the second half was covered with fouling deposits of different layers. Fouling deposits from three different locations along the second half of the syngas cooler were collected as samples for the purpose of examination. At first the morphological and composition analysis of the deposits were done for the as received tube sections after stabilizing the deposit with epoxy with SEM-EDX to identify the different layers. TG/DSC analyses were carried out to investigate the thermal behavior of the scratched samples from three locations. The heated samples after TG/DSC were examined again for the crystal structure change and morphology change. Finally evolved gas analyses of the deposits were done to identify which species act as the binding agent to cause the fouling deposit.