(220a) Petroleum Fouling: Causes, Tools, and Mitigation Methods

With the high price of light crude oils most refineries are driven to purchase greater quantities of lower priced opportunity crudes that are heavier and contain higher concentrations of sulfur and of naphthenic acids. This has led to higher frequency of refinery fouling, just when incentives for refinery utilization and for energy conservation are at their peak. Fortunately, the understanding of the causes and mitigation methods of petroleum fouling has greatly improved recently through the development of tools for prediction and for identification.

Surprisingly, 90% of petroleum fouling in refining has only a few common causes. The analysis of the foulant will usually enable identifying the root cause that is confirmed by finding the precursor in the oil flowing through the fouled unit. By tracing the precursor to the source, one arrives at a number of potential mitigating methods from which a refinery can select the best to implement for the refinery. Case studies will be presented where this strategy was used to mitigate petroleum fouling for different causes. Since the most common cause of organic fouling is by insoluble asphaltenes, a tool, the Oil Compatibility Model, was developed to predict the insolubility of asphaltenes on blending of oils and from thermal conversion. The presence of the carbonaceous mesophase in a foulant shows that the asphaltenes became insoluble at thermal reaction temperatures to form coke. These and other tools now make asphaltene fouling the easiest form of fouling to predict, to detect, and to mitigate. As a result, fouling by inorganics, caused either by corrosion or by ineffective desalter operation, is often a greater challenge to mitigate.