Sunday, March 29, 2009

There is Clean Coal!

This last semester a got a chance to work here on the UT campus as a lab technician for the Rochelle group, which is researching ways to sequester flue gas from coal fired power plants. The primary technology being studied uses organic amines in an absorber/stripper system to absorb the CO2 out of power plant flue gas. The separated CO2 can then be compressed with traditional compressor equipment and sequestered into the ground. The basic technology was developed in the late 1920’s to absorb CO2 out of natural gas and oil refinery streams. The technology has been significantly improved since its inception to allow for higher energy efficiency, decreased corrosion of plant materials, and decreased degradation of the amine solvent. Some major focus areas of Dr. Rochelle’s research included studying inhibitors that prevent the amines form degrading in the presence of oxygen and studying chemical kinetics for proper equipment sizing.

If this clean coal technology was implemented two major capital intensive projects would need to be implemented. First, coal power plants would need to install these systems on their flue gas process streams. Second, additional power plants would need to be constructed to account for energy used in the absorption/stripping process.

The rule of thumb used by the group calculated that an 800 MW coal fired power plant would lose about 1/3 of its power output using this technology due to energy consumption (The 800 MW plant is would now be a 533 MW plant). According to the EIA energy review the United States generates about 1.8 Trillion KW-hr of electricity from coal. If this technology was implemented today about 0.6 trillion KW-hr of new power would need to be produced to offset the loss. If we decided to replace this loss with 800 MW coal plants we would have to build 750,000 new power plants (0.6 x 10^12 KW-hr/800,000 KW-hr).

By these numbers I wish I was a power plant construction contractor right about now!

More information about the Rochelle group can be found at


Jeff Otto said...

In the debate about the nation’s energy future, there is no argument that at some cost carbon dioxide, sulfur dioxide, particulate matter, and mercury can be removed from flue gas produced at a coal-fired power plant. The real question is at what cost? Chemically separating, or sequestering the gaseous pollutants has a high economic cost. You mention in your post the parasitic load that a scrubber system has on the output of a coal-fired power plant. You cite that this reduces the top-line revenue of the power plant by 1/3, this is not considering the tens or hundreds of millions of dollars it takes to install the scrubber. It is when the negative externalities of air pollution are considered that coal starts to look less economic. What we as a society need to decide is how much we value the quality of our air, and the insurance price we are willing to pay for mitigating the unknown consequences of adding excessive greenhouse gases to our atmosphere.

Faiz said...

The Carbon Capture and Storage Technology, on the face of it seems a promising and easy technique to separate CO2 from flue gases and store it beneath the ground or down under the ocean floor but it is actually a much complicated technology to apply it in practice. Although there are lot of developments in this field, researchers are still trying to find a suitable way to apply it. It seems like a combination of multi faceted problems.
Cost is one of them. Capturing and compressing CO2 requires much energy and would increase the fuel needs of a coal-fired plant with CCS by 25%-40%. These and other system costs are estimated to increase the cost of energy from a new power plant with CCS by 21-91%[1].

As Jeff mentioned, it would cost billions of dollars just for those scrubbers to get installed to separate out CO2 from a mixture of other gases. Apart from the problems related to cost, there are hurdles related to the transport of CO2 to the geological site where it is stored. CO2 will be transported through pipelines. The existing pipelines which are being used for CO2 enhanced oil recovery can be used for this but the Federal classification of CO2 as both a commodity (by the Bureau of Land Management) and as a pollutant (by the Environmental Protection Agency) could potentially create an immediate conflict which may need to be addressed not only for the sake of future CCS implementation, but also to ensure consistency of future CCS with CO2 pipeline operations today.[2]

Geological storage location is also big barrier for the implication of CCS. CO2 captured will be stored in deep saline aquifers or other geological formations but less is known about the geology of such aquifers. To keep the cost of storage acceptable the geophysical exploration may be limited, resulting in larger uncertainty about the aquifer structure. Another idea of storage is to inject CO2 into oceans where it mixes with alkaline sea water and dissolves. There are complications in this type of storage too.

Even if we find out solutions for the above mentioned problems many researchers says that it will take at least 15- 20 years to completely implement this technology into practice. If the emission of CO2 is actually leading to Global Warming (God knows this is true, especially after reading articles which propound the idea that global warming is a myth or not well understood), we need to find some immediate solution along with research and development in CCS technology.