The problem of designing crude fractionation units is not only a distillation design. It has the added complexity that these units should be able to process different types of crude, sometimes from heavy to light. Important heat exchange also takes place, and the energy efficiency is related to the column design parameters. Crude distillation is energy intensive. It consumes fuel in the equivalent of 2% of the crude processed. The conventional design, consisting of a column with side strippers and pump-around circuits, appeared 70 years ago (Miller, 1938), and is still the design used in the refining industry. Watkins (1979) proposed a design procedure for this system and discussed a few variants such as pump-back reflux and stripping using reboilers. A few alternative designs can be found in the literature. For example, the addition of pre-fractionation columns to this conventional design was proposed by Brugma (1941) and is being used in several industrial sites. Another old design, the carrier design, was proposed as early as the 1920s. This design makes use of light components to enhance the separation in the stripping section of the column. Nelson (1958) also mentioned some other alternative designs. All these old designs have been abandoned for reasons that are not completely known or understood. One important fact is that they were abandoned before the seventies, when energy consumption started to play an important role in process economics. Because energy efficiency is now desired, all these designs merit reevaluations. Nevertheless, the conventional design is widespread and popular. We developed and are developing:
A rigorous targeting methodology to design this multipurpose plant, which can be implemented using a commercial simulator.
A heat Exchanger network design procedure.
Several retrofit procedures.
We have also studied in detail the performance of alternative designs, like the pre-flash, pre-fractionation and stripping type designs. These are part of a string of several papers starting in 1998.
As part of our studies we have developed two new technologies, for which patent applications have been filed to increase the yield of distillates and reduce energy consumption in crude units.
In addition, we are currently investigating the energy savings of two new technologies.
Patents
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