Washington, Dec 23 Oil refineries worldwide could save billions of dollars in energy costs yearly, by using a novel method developed by an Indian-Amercian chemical engineer.

Researchers led by Rakesh Agarwal, Purdue University professor of chemical engineering, have shown how their method could help refineries improve the energy efficiency by six to 48 percent.

Chemical plants of refineries expend from 50 percent to 70 percent of their energy in 'separations', usually distillation steps that separate a raw material into various products.

In 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 process gasoline.

"Separations are a huge part of what chemical plants do," said Agrawal, who did his B.Tech from the Indian Institute of Technology, Kanpur, India, in 1975.

"Improving efficiency by only a few percentage points translates into major savings. For every 100 barrels of oil distilled, nearly two barrels go into supplying energy for distillation. That's a lot of oil."

"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," said Agrawal, who is working with doctoral student Vishesh Shah, according to a Purdue release.

"And that's just a single refinery. For the US petroleum industry (alone), this is a huge potential savings," said Shah. Purdue has filed a patent application for the new crude distillation sequences.

These findings appeared online in AIChE Journal, the official publication of the American Institute of Chemical Engineers.