Cooled coal emissions can clean air: university study

RESEARCHERS from the University of Oregon have revealed that refrigerating emissions from coal-fired plants can reduce chemical emissions, including carbon dioxide by more than 90%.
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Donna Schmidt

The results, prepared by a research group on an electronic spreadsheet and presented in American Physical Society journal Physical Review E,would equate to a cost of 25% efficiency.

The University of Oregon said a separate, unpublished and preliminary economic analysis of the technology shows that the “energy penalty” would increase electricity costs by about 25% but conversely would also reap significant societal benefits via subsequent reductions of healthcare and climate-change costs.

“The cryogenic treatment of flue gases from pulverized coal plant is possible, and I think affordable, especially with respect to the total societal costs of burning coal," physicist Russell Donnelly said.

Donnelly’s research team and its work thus far was funded by the US Department of Energy.

"In the US, we have about 1,400 electric-generating unit powered by coal, operated at about 600 power plants," Donnelly said.

A Congressional Budget Office estimate from 2006 was about 5.6 cents per kilowatt hour for sold energy, he said.

“The estimated health costs of burning coal in the US are in the range of $US150 billion to $380 billion, including 18,000-46,000 premature deaths, 540,000 asthma attacks, 13,000 emergency room visits and two million missed work or school days each year."

Donnelly and research assistant Robert Hershberger, also of the University of Oregon and a co-author on the journal paper, estimated implementation of large-scale cryogenic systems into coal-fired plants would result in a 38% overall cost reduction to society because it would leave the nation with a sharp reduction of associated healthcare and climate-change costs.

Not included in that equation, he noted, are the front-end healthcare costs involved in coal extraction through mining.

What is especially notable about the cryogenic research is that that it is not new.

In fact, Donnelly, said, he first experimented with it in the 1960s using an Oregon paper mill seeking to remove odor-causing gases. That work was successful.

The National Science Foundation later funded a major study to capture sulfur dioxide emissions from coal burning plants. Grant money from that effort included a detailed engineering study by Bechtel.

That study, the university said, showed the cryogenic process would work very well.

However, large quantities of carbon dioxide also would be condensed. In 1978, that consequence did not raise concerns.

“Today we recognize that carbon dioxide emissions are a leading contributor to climate-warming factors attributed to humans," Donnelly said.

His previous work was unshelved once more and a two-year project followed to recheck and update his thermodynamic calculations and compose a spreadsheet-accessible formula that industry could potentially make use of.

“While the required cooling machinery would be large ¬– potentially the size of a football stadium ¬– the cost for construction or retrofitting likely would not be dramatically larger than present systems that include scrubbers, which would no longer be necessary,” the university said of Donnelly’s work.

Additionally, the journal work does not address construction costs or captured pollutants disposal, the latter of which would hinge on engineering and geological considerations.

The researchers say in the Physical Review E paper that carbon dioxide would be captured in its solid phase, warmed and compressed into a gas, then moved by pipeline at near ambient temperatures to a dedicated storage facility.

Other chemicals, including sulfur dioxide, some nitrogen oxides and mercury, could also be condensed and safely removed from the plants’ exhaust stream.

Donnelly said the group’s “conservatively produced” calculations would do better than the US Environmental Protection Agency’s newly issued Mercury and Air Toxics Standards regulations that call for the trapping of 41% of sulfur dioxide and 90% mercury.

A cryogenic system, he said, would capture at least 98% of sulfur dioxide, virtually 100% of mercury and 90% of carbon dioxide.

"This forward-thinking formula and the preliminary analysis by these researchers offer some exciting possibilities for the electric power industry that could ultimately benefit human health and the environment," UO vice president for research and innovation Kimberly Andrews Espy said.

"Scientists at the University of Oregon are continuing to develop new ideas and advanced materials to foster a sustainable future for our planet and its people."

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