Experimental study on crude oil fouling in preheat exchangers at different operating conditions

Abstract

Fouling is one of the leading causes of energy loss in oil industry, particularly in preheat exchangers of refineries and desalting units. For each day that an oil operation unit producing 80,000 BPD is shut down due to fouling, a significant economic loss of approximately 6,400,000 $ (assuming 80 $/bbl) will occur. Unfortunately, there is currently no global or specific solution for reducing crude oil fouling in these units. On the other hand, conventional fouling detection methods are beaded on an inaccurate pressure difference measurement. This study proposed an accurate and sensitive thermal method based on surface temperature variation for fouling detection in crude oil system which was rarely reported in the literature. Experiments were performed to investigate the impact of three key operating parameters including heat flux (51.3–72.7 kW/m2), bulk temperature (33–40 °C) and fluid velocity (0.09–0.14 m/s) on the fouling rate of crude oil. The results indicated that the applied heat flux primarily determines a direct or inverse relationship between fouling rate and fluid velocity. Increasing fluid velocity, at a lower heat flux, decreases the fouling rate up to 23 % due to particle removal by shear stress while at higher heat flux, the simultaneous positive effect of diffusion and adhesion forces increases the fouling rate up to 63 %. Increasing bulk temperature reduces the fouling tendency of crude oil but demonstrates different effects at the beginning and end of the experiments. As heat flux increases, fouling occurs more rapidly due to increas ed adhesion forces, thermal driving force, and particles diffusion.