On Day 1 of Gulf Energy Information’s Carbon+Intel Forum in Houston, Texas (U.S.), Anthony Leo, Executive Vice President, Chief Technology Officer for Fuel Cell Energy, delivered a presentation titled, “Advanced fuel cell-based carbon capture solutions.”

Leo began his presentation with a brief overview of Fuel Cell Energy, focusing on its power generation solutions based on carbonate fuel cells, the development of its solid oxide fuel cells and H₂ production applications for high-temperature fuel cell platforms.

Fuel cell technology. Fuel cells convert energy in H₂-rich fuels into electricity and high-quality heat. A fuel stack is comprised of many cells grouped together, which convert fuels to H₂ by reforming water and heat produced by the fuel cell. Conversely, fuel cell stacks can produce H₂ from steam and power. Solid oxide fuel cells can operate with natural gas, biogas or liquid H₂ and can produce H₂ through internal reforming or electrolysis.

For the presentation, Leo focused on carbonate fuel cells. According to Leo, carbonate fuel cells can be deployed as carbon capture devices. “All fuel cells that run on hydrocarbon fuels can capture their own carbon, but carbonate fuel cells are unique because they can capture CO₂ from an external source,” Leo said.

He explained that a fuel cell is like a battery but reacts with fuel and air, and it has a fuel and air electrode with a thin material in between that contains an electrolyte. Fuel Cell Energy stacks 400 single fuel cells in its standard stack; four of these stacks go into its 1.4-MW stack module.

“In a carbonate fuel cell, we typically send a hydrocarbon and steam mixture into our fuel electrodes, and steam methane reforming happens driven by waste-to-heat from the fuel cell,” Leo said. “That methane is converted to H₂. The carbon associated with that methane is going to be exhausted in the form of CO₂, but the fuel electrode chemical reaction consumes H₂ while producing extra CO₂.”

For every one CO₂ that’s associated with the methane, we are going to create four additional CO₂’s, he said. We need to get the four extra CO₂s to our air electrode because the air electrode reaction reacts with oxygen and CO₂. “We realized this could be exploited for carbon capture because in that stream is a lot of extra CO₂ that is relatively easy to grab,” Leo said.

Carbon capture. Leo went on to describe the carbon capture process. In this process, carbon is captured from its platform, taking a system that’s making combined heat and power, and instead of emitting CO₂, most can be captured and used in other industries (e.g., food and beverage).

“Another thing that is very unique to carbonate is deploying carbonate to capture CO₂ from an external source,” he said. “We send a hot fuel steam mixture (two parts water and one part methane) into our fuel electrodes, and we form a reaction that turns methane into H₂. We use about 70% of that H₂ to make power and leave 30% unused to be used in a catalytic reactor. CO₂ and leftover H₂ then comes out of the fuel electrodes.”

In the carbon capture process, the front-end is the same, but all the exhausts from the fuel electrodes are taken, cooled down to remove the water and then compressed/chilled to remove the CO₂, according to Leo. It is then sent it back to the cathodes. The problem becomes that all the CO₂ has been removed from cathodes, which require CO₂, so the external source of CO₂ from the flue gas replaces the CO₂ that was removed. The leftover H₂ that was in that stream can be exported.

Story by Tyler Campbell, Managing Editor H₂Tech