Technology approaches to reduce the amount of carbon dioxide released into the atmosphere from industrial sources – principally hydrocarbon fuel-based power plants- has been evaluated in some of my earlier posts. It is now generally agreed that scrubbing flue gases with alkaline liquids, followed by stripping out the carbon dioxide, is uneconomical, except for the possible case of the Skyonics technology (see post dated June 26, 2014) which makes bicarbonate of soda and hydrochloric acid useful for fracking, but has limited broad-scale application (Small size of bicarbonate market, sale of HCL requires large local market, such as nearby large fracking installations.). I have also covered the approach where power plants do not burn the coal, but make synthesis gas from gasified coal as a technique to produce a concentrated carbon dioxide stream( Kemper lignite-based plant described in post dated January 2nd, 2016). This technology, which is also being applied in a grassroots Canadian plant( in both cases using large government grants), is now also deemed to be uneconomical due to very high capital investment as well as high operating costs.
But now we come to an entirely new approach to carbon dioxide capture, namely use of a special type of fuel cell, which has recently received a strong vote of confidence from ExxonMobil Research. The concept is very interesting and will be described below. What is not yet clear are the economics for this approach and whether it is truly scaleable.
This fuel cell, as built and commercially used by Fuel Cell Energy, uses a high-temperature molten carbonate salt mixture. Reformed natural gas (i.e. hydrogen) and oxygen are reacted to generate power, producing carbon dioxide and water. In a typical application, the produced carbon dioxide is recycled, but in the carbon capture and sequestration (ccs) mode, the carbon dioxide-steam mixture is chilled to about 40 degrees below zero where carbon dioxide becomes a liquid and is separated and stored underground. The fuel cell then needs to replace the removed carbon dioxide and captures it from the incoming flue gas from the power plant, which substitutes for normally used air pumped into the fuel cell. Importantly, the system can also strip out 70 percent of the smog-producing oxides of nitrogen present in the power plant flue gas(!).
The company has installed relatively conventional fuel cells in fifty or so locations around the world. Now, Fuel Cell Energy wants to hook its ccarbonate cells up to power plants.The concept ( fuel cells with ccs) has been proved out in relatively small scale cells, with part of the funding from a $ 2.5MM grant by DOE. Now, a very major scale-up is planned, with more meaningful funds becoming available from ExxonMobil. Vijay Swarup. vice president for research and development at ExxonMobil Research and Engineering says that while commercial application at power plants is years away, the ccs-oriented fuel cell application “could be a game changer.”
Fuel Cell Energy claims that current ccs technologies, such as used at the Kemper plant, nearly double the cost of power. Their approach uses considerably less so-called parasitic power( a term used to identify the percent of the power needed to run the complete system) and therefore provides a strong economic incentive.