With concern about global warming prompting 177 countries to sign the December 2015 Paris Agreement to reduce greenhouse-gas emissions, the removal of carbon dioxide from power-plant flue gas is becoming an urgent priority. On May 5, a fuel-cell manufacturer and an international oil-and-gas player unveiled their plan to meet that need.
For the past two years, FuelCell Energy Inc. and Exxon Mobil Corp. have jointly performed comprehensive laboratory tests on the carbon-capture technology of FuelCell Energy’s molten carbonate fuel cell. Now, the companies will work together to integrate it into a larger-scale pilot plant within four years.
Using conventional amine scrubbers to capture power-plant carbon-dioxide emissions can cost 30% of the plant’s net output. By contrast, integrating carbonate fuel cells and natural-gas-fired power generation captures CO2 more efficiently than conventional scrubber technology while actually increasing the plant’s power output, say officials of both companies.
Of the various fuel-cell technologies, “carbonate is the only one that uses, consumes or wants some CO2 intake,” says Kurt Goddard, FCE’s vice president of investor relations.
That appetite for carbon makes carbonate fuel cells an object of intense interest today, and pairing Exxon Mobil’s deep pockets, natural-gas production and infrastructure with FCE’s technology may be a timely combination—if it lives up to billing and scales successfully.
Breaking Into the Mainstream
Fuel cells have been a niche player in power for decades. While they have been used to generate electricity on a relatively small scale for primary and backup power, they have not yet broken into the mainstream (ENR 7/8/13 p. 36).
The FuelCell Energy-Exxon project may be one of the first applications of fuel-cell technology to add carbon capture to the fuel cell’s capabilities. “The idea has been around for a while—that the fuel cells can do it. The problem has been the maturity of fuel cells and the difficulty of scaling the fuel cells up to a utility scale,” says Howard J. Herzog, project director of carbon-capture and sequestration technologies at MIT.
A lot of the energy penalty in conventional carbon capture results from separating the CO2 from the nitrogen in the flue gas, notes Herzog, who says he does not know of any major project using fuel cells for carbon capture.
In the carbonate fuel cell, natural gas (CH4) reacts with coal- or gas-fired power-plant flue gas after the sulfur oxides have been removed. The reaction concentrates CO2 in the anode exhaust, which is chilled, compressed and condensed. Then, it can be piped, trucked or sequestered, Goddard says.