Process would make coal burn cleaner

Ongoing projects are funded with about $15 million in federal money and $5 million in private funds. A new project involving large-scale sequestration, to be based near Price, has $67 million in federal funds and $21 million from private partners like ConocoPhillips and Resolute Natural Resources (based in Denver), he said.

Extracting the carbon dioxide from the plant's exhaust stream is the expensive part, according to McPherson.

In a commercial setting, carbon dioxide would be removed from power plant emissions. The experimental sequestration takes gas from underground sites and pumps it into other below-surface formations.

To capture carbon dioxide:

• The emission stream is forced into a vat of chemicals, and the vat's conditions are changed so that the chemicals absorb carbon dioxide. Different combinations of pressure and temperature are used, depending on the chemical makeup in the vat.

• When CO2 is absorbed by the chemicals, the mixture is moved to another vat, where the conditions are changed again so that the CO2 bubbles out of the liquid. This is pure carbon dioxide, taken out of the plant's emissions.

• Two or more of these systems will operate simultaneously. While one is removing CO2 from the emissions, the other(s) will be separating the gas.

To sequester it:

• Captured CO2 is piped to a compressor, where it is pressurized to 2,000 pounds or 2,500 pounds per square inch. The pressure depends on "whatever the subsurface pressure is" at the target depth, McPherson said. With that sort of pressure, the gas "becomes essentially liquefied."

• "A pump is used to inject it down to depth." Pumping it down requires forcing it into a reservoir where pressures are "very high; again, 2,000 to 3,000 psi," he said.

The researchers have built a laboratory producing high pressure and high temperatures that can test the system, according to the university. Also, they are carrying out experiments in the field.

"We're right now in the midst of testing and research and development," McPherson said.

Smaller-scale CO2 injections are taking place near Bluff, San Juan County, and near Midland, Texas. Starting this month or next, he added, "we'll start injection in northern New Mexico in a coal field."

These experiments are to inject about 100 tons per year.

The group also is engineering a large-scale sequestration project scheduled to take place this year near Price. Pressurized gas would be injected into underground brines about 5,000 feet below the surface.

"The Price tests will be about a million tons a year," he said.