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Technology Research Area:

TVA Cryogenic Acid Gas Removal Process

What is the cryogenic acid gas removal process, and what does it have to do with TVA's mission?

The cryogenic acid gas removal process, developed and patented by TVA, could potentially make coal gasification much less expensive, and therefore more feasible for producing cleaner energy.

Coal gasification has been proposed as a way to limit the emission of carbon dioxide (CO2), a greenhouse gas, by using the energy in coal to produce a gas fuel whose active component is hydrogen. Hydrogen emits only water vapor when it is burned.

During the production of this hydrogen-based fuel, the carbon in the coal is converted into CO2. The CO2 is then separated from the hydrogen and compressed to a high pressure for disposal. The high pressure is necessary for the most commonly proposed methods for disposal: pumping it into the ground for deep underground containment or using it to increase the recovery of oil underground.

The coal gasification process has the potential to make disposal of CO2 easier because the gasified coal can be produced at high pressures. However, the currently used processes for removing CO2 (called acid gas removal) are costly, and have failed to take full advantage of the high pressure of CO2 in the gas.

The TVA cryogenic acid gas removal process cools the gas to condense the acid gases, separating the condensed acid gases and then evaporating the acid gases to provide the cooling needed to condense more acid gases. The gas essentially cools itself to carry out the condensation and removal of the acid gases.

The cooling is carried out in stages, starting with the original high pressure gas and continuing through successively lower pressure levels. This takes advantage of the original high pressure to begin the sequence, and that saves power. Less money is needed to generate power, making the whole process easier and cheaper.

What is TVA doing about it?

TVA has patented the cryogenic acid gas removal process in the U.S. and Canada, and is now marketing the license for use of the patent to help make the process available for coal gasification.

What are the possibilities for the TVA cryogenic acid gas removal process?

The TVA cryogenic acid gas removal process has the potential to make removal of CO2 in coal gasification more energy efficient and cheaper for the utility industry. It also has the potential to generate revenue for TVA through licensing of the technology.


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