Economic pressures on the refining industry are forcing many refiners to look at lower priced high acid crudes to improve margins. These crudes may be discounted because they are perceived to cause increased corrosion or fouling problems, or simply because they are new or unknown to the market. If these problems are not properly managed or understood, the benefits of lower price may be consumed by higher processing costs or by the deterioration of the assets caused by corrosion. To safely process these high acid crudes, a comprehensive multi-discipline service has been implemented to identify, assess and mitigate the corrosion, fouling and processing risks associated with these crudes. This service covers all the aspects that are necessary to optimize the economics of processing corrosive crudes, such as materials selection, corrosion inhibition, process control, corrosion monitoring, inspection, and scheduling. In addition to managing the potential corrosion problems, it also addresses key issues such as crude oil selection strategy, the true value and cost of processing the crudes, an evaluation of the refinery's blending capabilities, the compatibility of various crudes, the quality of products, etc. This paper provides an overview of the strategic issues associated with processing high acid crudes and several case histories describing the benefits gained from using this approach.
Refineries are increasingly faced with the often competing requirements of increasing their margins while maintaining high levels of reliability and on stream availability of their plants. With crude costs accounting for around 80 % of a refinery?s expenditures, processing cheaper crudes can have a very positive impact on refinery margins. Traditionally high sulfur, high TAN (Total Acid Number) and
? Accelerated corrosion in the atmospheric and vacuum distillation columns, associated side strippers, furnace and piping, and overhead system.
? Accelerated heat exchanger fouling in the crude pre-heat train resulting in a reduction of plant capacity
? Fouling of the atmospheric and vacuum units with corrosion products
? Problematic desalting, resulting in loss of throughput capacity, loss of thermal efficiency, and loss of crude to the water
? Accelerated coking of furnaces in distillation units, coker or conversion units.
If not properly solved, these problems can quickly erode any margin gains obtained from buying a cheaper feedstock. But for those refiners that know how to handle these problems, these crudes can represent a significant improvement to their bottom line. Figure 1 shows an example of the difference in gross refinery margin (GRM) that can be achieved by processing a lower priced high acid crude (HAC) feedstock for a medium size, 200 KBPD refinery. The annual improvement in GRM can be in the 10?s of millions of dollars, if the costs associated with processing HAC?s are low. Before embarking on a program to introduce cheaper or opportunity crudes, a refinery must evaluate and balance the cost of corrosion, fouling and processing risks with the savings of a cheaper crude.
FIGURE 1 - Example of the gross refining margin (GRM) differential when processing high acid and low acid crudes.
Recent trends in the crude oil supply market indicate that within the next few years processing HAC?s will be less a matter of choice than of necessity. The global conventional crude oil slate will become markedly different from that of today, as supplies of conventional light, sweet crude decrease, and they are replaced by crudes lower in gravity and higher in acidity, sulfur and other impurities. High TAN, heavy crude