In the article, they highlight the challenge many refiners face who process “opportunity crudes” from shale oil and other non-conventional sources. The feedstock varies much more in terms of density, sulfur content, salt content and volumetric yield than traditional sources of crude oil have varied. They noted for traditional sources, the:
…crude assay would usually change little over time, often measured in years and only happening slowly as the well moved toward the end of its productive life. What is more, one well’s crude assay could frequently serve as a proxy for all other wells within the field.
Stable feedstocks are not the case for shale oil:
So, the type of crude assay that has been valuable in the past is no longer as useful because assays that were once good for many years, if not decades, may no longer hold from one well to another, or from one well to itself a few months hence.
Addressing the challenge of feedstocks with widely variable properties, involves three steps:
…developing the right analysis capabilities and then using the data thus generated to adjust the blend and the process to create the optimum solution.
Near infrared (near-IR) technology helps identify the composition of the feedstock through its spectral signature. This spectral signature helps determines the characteristics of the crude oil, which in turn, should be used to adjust the blending process:
…to create an input stream to the refinery that is a better match than any crude source may be on its own.
Using an analyzer-driven blending system:
…it is possible to determine such important properties of crude as its true boiling point (TBP) in less than a minute. In turn, this enables blending adjustments that result in benefits running into millions of dollars.
Feedstocks are not the only thing that varies. Changes in the weather:
…can also push distillation column operation out of optimum.
Traditionally, the solution was to over-purify the components to avoid being out of specification, which leads to:
…wasted energy and lower product yield.
Advanced process control strategies can address these variations:
…to automatically adjust distillation column parameters to optimal targets without violating constraints. Doing so will reduce product quality variation and off-spec production while minimising energy consumption per unit of feed. It will also increase recovery of more valuable products and column throughput. In the context of a world where feedstocks are more variable, this will mean that blending operations will have more leeway.
Patrick and Didier sum up their thoughts:
Because their properties are so variable, an old-style crude assay does not make sense. Hence, the need is for real-time analysis to provide the data for ad-hoc blending of crude supplies and intelligent process control. Together these can make a solution.
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