Method cuts costs at refineries

Refineries could trim millions of dollars in energy costs annually by using a new method developed by a team of Purdue researchers to rearrange the distillation sequence needed to separate crude petroleum into products.

The researchers, led by Rakesh Agrawal, the Winthrop E. Stone Distinguished Professor of Chemical Engineering, have demonstrated their method on petroleum plants that separate crude, showing that 70 of the new sequences they identified could enable oil refineries to improve the energy efficiency of this step anywhere from 6 percent to 48 percent.

“This is important because improving efficiency by 10 percent at a refinery processing 250,000 barrels per day would save in excess of $12 million a year if oil were priced at $70 a barrel,” says Agrawal, who is working with doctoral student Vishesh Shah. “And that’s just a single refinery. For the U.S. petroleum industry as a whole, this is a huge potential savings.”

Chemical plants spend from 50 percent to 70 percent of their energy in “separations,” which are usually distillation steps required to separate a raw material into various products. In the case of petroleum, four distillation columns are needed to separate raw crude into five separate components – naphtha, kerosene, diesel fuel, gas oil and heavy residue. Some of these components are later used to make gasoline. The distillation is more energy efficient depending on the order in which the columns are operated.

Shah created a computer algorithm that identifies all of the possible sequences and then determines which require the least heat and energy. The researchers used their new technique to determine there are nearly 6,000 possible sequences for the four columns used in petroleum distillation. Purdue has filed a patent application for the new crude distillation sequences.