CFD modeling of asphaltene deposition rate from crude oil

• Effects of operating conditions on asphaltene deposition rate are studied numerically.
• Effect of wall roughness on fouling is analyzed.
• Increasing the wall roughness reduces the deposition.
• The deposition rate plateaus with further increase of the wall roughness beyond 0.01D.

In this work, rate of asphaltene deposition from crude oil flowing under forced convection through a vertical pipe have been investigated using computational fluid dynamics (CFD). Effects of operating conditions such as surface temperature, Reynolds number, asphaltene concentration and surface roughness on the heat transfer coefficient, thermal resistance, and asphaltene deposition rate are studied numerically. For smooth pipe, the results showed that deposition rate of asphaltene decreases as crude oil velocity increases while it increases with increasing the surface temparature and flocculated asphaltene concentration. According to the results, by increasing the crude oil velocity from 0.6 to 1.6 m/s, the thermal resistance reduced to 62%. Also by increasing the concentration of flocculated asphaltene from 3.5 to 5.5 kg/m3, reduction in the heat transfer coefficient ratio is 4.5%, while the rate of asphaltene deposition and thermal resistance increases to 18.3%, and 17%, respectively. These are in agreement with previously published experimental results and theoretical models. The simulation then was extended to consider the wall roughness effects on asphaltene deposition rate. It was observed that increasing the wall roughness reduces the deposition. However, the deposition rate plateaus with further increase of the wall roughness beyond 0.2 mm, which is just under 1% of the pipe diameter.