Advanced Carbonate Fuel Cell Technology in Carbon Capture and Storage
ExxonMobil, with partner FuelCell Energy, Inc., is advancing a new technology to capture carbon dioxide from large emitters such as power plants. At the center of ExxonMobil’s technology is a carbonate fuel cell. Laboratory tests have demonstrated that the integration of carbonate fuel cells and natural gas power generation captures carbon dioxide (CO2) more efficiently than current, conventional capture technology. Using fuel cells to capture carbon dioxide from power plants results in a more efficient separation of carbon dioxide from power plant exhaust. The potential breakthrough comes from an increase in electrical output using the fuel cells, which generate power, compared to a nearly equivalent decrease in electricity using conventional technology.
Carbon capture and storage (CCS) is a process by which carbon dioxide that would otherwise be released into the atmosphere is captured, compressed and injected into underground geologic formations for permanent storage. During the conventional capture process, a chemical reacts with the carbon dioxide, extracting it from power plant exhaust. Steam is then used to release the carbon dioxide from the chemical – steam that would otherwise be used to move a turbine, thus decreasing the amount of power the turbine can generate.
With the new technology ExxonMobil is developing, power plant exhaust is directed to the fuel cell, replacing air that is normally used in combination with natural gas during the fuel cell power generation process. As the fuel cell generates power, the carbon dioxide becomes more concentrated, allowing it to be more easily and affordably captured from the cell’s exhaust and stored.
ExxonMobil’s laboratory tests indicates that by applying this technology, more than 90% of a natural gas power plant’s carbon dioxide emissions could be captured. The resulting net benefit has the potential to substantially reduce costs associated with carbon capture for natural gas-fired power generation, compared to the expected costs associated with conventional separation technology. ExxonMobil’s research indicates that a typical 500 megawatt (MW) power plant using a carbonate fuel cell may be able to generate up to an additional 120 MW of power while current CCS technology consumes about 50 MW of power.
In addition, carbonate fuel cell technology has the potential to generate significant volumes of hydrogen. Simulations suggest that the new technology can produce up to 150 million cubic feet per day of hydrogen while capturing carbon dioxide from a 500 MW power plant. To put that in perspective, a world-scale steam methane reforming hydrogen plant produces around 125 million cubic feet per day. In addition, synthesis gas, or syngas, composed of hydrogen and carbon monoxide, can be produced that can be upgraded to other useful products such as methanol, olefins, or higher molecular weight hydrocarbons for transportation fuels or lubricants