Impact of Centrifuge-Separated Fractions from Light Tight Oils on the Propensity and Mechanisms of Fouling,and Improved Crude Oil Fouling Potential Prediction Model

摘要

Processing of light tight oils (LTOs) and their blends is challenged with their high fouling propensity. In this study, their fouling potential was attributed to fractions from centrifuge-accelerated settling. A small solid fraction comprising lower than 0.5% of the volume was found to bear a majority of the fouling potential of a set of LTOs. The chemical analysis of these centrifuge-separated solids from an LTO blend resembled that of the field deposits from the crude unit furnace tubes processing the same blend, further validating their impact in crude unit fouling. The liquid fraction of the LTOs affected the fouling potential in two aspects. First, the same solid fraction separated form an LTO presented varying fouling potency when mixed with different liquid fractions from different crude oils. Second, paraffin crystals led to a flocculated structure and impaired solid settling. Time-of-Flight Secondary Ion Mass Spectrometry analysis of lab-generated thin fouling films unmasked the complex and intertwined fouling mechanisms of different LTO blends, which explained the unsatisfactory prediction quality of crude oil fouling potential based on solid volume fraction alone and emphasized the importance to evolve from the conventional fouling management approach focusing solely or heavily on asphaltene stability. Finally, a nonlinear model considering the two-class solids loading input and the Fourier transform infrared fingerprint of the crude oil was developed to predict the fouling potential of crude oils. The predictive power of the model was corroborated in the field at various refinery sites processing crudes with fouling potentials ranging from low to severe. As an integral component of our field-deployable predictive modeling platform, the fouling potential model helped refineries quickly and reliably predict crude oil instability and fouling severity, the associated processing issues, the likely locations where they may be manifested, and the recommended actions for mitigation. Hence, feed-forward optimization and reliability improvement of the crude fractionation unit process were made possible.