USA: Refrigeration is often blamed for its contributions to global warming, but in the future it could be used to significantly reduce CO2 levels from coal-fired power stations and reduce levels of other dangerous chemical emissions.
Physicists at the University of Oregon have predicted that refrigerating coal-plant emissions could reduce CO2 emissions by 90%, and reduce levels of other dangerous chemicals that pour into the air, at a cost of 25% efficiency.
The computations for such a system, prepared on an electronic spreadsheet, appeared in
Physical Review E, a journal of the American Physical Society.
In a separate, unpublished and preliminary economic analysis, the scientists argue that the 'energy penalty' would raise electricity costs by about a quarter but also reap huge societal benefits through subsequent reductions of health-care and climate-change costs associated with burning coal.
'The cryogenic treatment of flue gasses from pulverized coal plant is possible, and I think affordable, especially with respect to the total societal costs of burning coal,' said UO physicist Russell J. Donnelly, on the University of Oregon website.
'In the U.S., we have about 1,400 electric-generating unit powered by coal, operated at about 600 power plants,' Russell Donnelly said. That energy, he added, is sold at about 5.6 cents/kWh, according to a 2006 Congressional Budget Office estimate. 'The estimated health costs of burning coal in the U.S. are in the range of $150bn to $380bn, 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.'
Russell Donnelly and UO research assistant Robert E. Hershberger, a co-author on the journal paper, estimate that implementing large-scale cryogenic systems into coal-fired plants would reduce overall costs to society by 38% through the sharp reduction of associated health-care and climate-change costs.
The cryogenic concept is not new. Donnelly experimented briefly in the 1960s with a paper mill in Springfield, Ore., to successfully remove odour-causing gasses filling the area around the plant using cryogenics. Subsequently the National Science Foundation funded a major study to capture sulfur dioxide emissions -- a contributor to acid rain -- from coal burning plants. The grant included a detailed engineering study by the Bechtel Corp. of San Francisco.
The Bechtel study showed that the cryogenic process would work very well, but noted that large quantities of carbon dioxide also would be condensed, a consequence that raised no concerns in 1978. 'Today we recognize that carbon dioxide emissions are a leading contributor to climate-warming factors attributed to humans,' Donnelly said.
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, Donnelly said.
According to the
Physical Review E paper, carbon dioxide would be captured in its solid phase, then warmed and compressed into a gas that could be moved by pipeline at near ambient temperatures to dedicated storage facilities that could be hundreds of miles away. Other chemicals such as sulfur dioxide, some nitrogen oxides and mercury also would be condensed and safely removed from the exhaust stream of the plants.
http://uonews.uoregon.edu/archive/news-release/2012/8/cooled-coal-emissions-would-clean-air-and-lower-health-and-climate-chang