Asphalt’s assistance
Team says method strips carbon dioxide from natural gas at wellhead
A material used for roads can help limit carbon dioxide releases, Rice chemists say.
Rice University chemists say they have discovered how to quickly and cheap ly strip carbon dioxide from natural gas at the wellhead, an advance that might someday save gas drillers millions of dollars in potential carbon taxes and, to somedegree, help curtail climate change. Thesecret: asphalt. Rice chemistry professor James Tour and his lab workedfor six years before coming up with a method using a type of asphalt known as Gil son it et or educe the carbon dioxide released in natural gas processing, whichstrips impurities from the gas before it is sold commercially.
Carbondioxideis so-called greenhouse gas that contributes to global warming, and many energy companies expect the U.S. government to impose taxes based on the carbon dioxide released byfossil fuels as part of a worldwide effort to slow climate change.
“They are going to have to stop blowing this stuff into the air,” Toursaid. “It hasn’t hit yet, but they see it coming.”
Carbondioxide is released into the atmosphere when fossilfuelsare pumpedfrom the ground and later burned, and carbon capture has become one of the great technological challenges for the energy industry. Companies andresearchers are seeking waysto collect carbon dioxide before it is released into the atmosphere.
Before natural gas can be burnedat powerplants, it must be stripped of impurities, including carbon dioxide, which makes up anywhere from 2 to 10 percent of the gas pulled from the ground. Buttheprocess is energy-intensive and expensive. Companies transport the newly mined gas via pipeline to plants, wherethe gas is passed through fluids called amines, whichfilter out impurities, andthen
“If you can do this at the wellhead, then you can just pump it right back down ...” James Tour, Rice chemistry professor
are heated to temperatures above 250 degrees to release the natural gas.
A mines, however, can only soak up about 15 percent of their weight in carbon dioxide, whichrequires large amounts of the fluid sand higher costs, Toursaid. The process vents the carbon dioxide into the atmosphere.
If natural gas producers could find an economical method to separate and capture the carbon dioxide, they would not only reduce their exposure to carbon taxes, but also have a product to sell. Carbondioxide has industrial uses, including stimulating oil and gas recovery in existing wells.
So Tour and his team at Rice began investigating alternatives.
Two years ago, they published research on a porous carbon powder that trapped 82 percent of its weight in carbon dioxide. Last year, they found anasphaltthat absorbed 114 percent of its weight in the greenhouse gas, and then improved its performance. In research published this month in the journal Advanced Energy Materials, Tour showed that the asphalt, Gilsonite, can trap 154 percent of its weight in carbon dioxide.
Better yet, the new material works at room temperature, and at pressures common inside gas wellheads. It releases gaswhenpressure dips.
Tour said companies could add a pipe and some valves at the endof a well, easily clean the natural gas, and capture the carbon dioxide at the same time.
“If youcandothis at the wellhead,” Toursaid, “then you can just pump it right back down underground, whereit’s been for millions of years.”
The Houston oil and gas exploration company Apache funded there search andhaslicense to the intellectual property, Toursaid. AlmazJalilov, a postdoctoral researcher waslead author of the study.