Georgia Tech researchers have demonstrated a CHAMP reactor, which uses the four-stroke engine cycle to create hydrogen while simultaneously capturing carbon dioxide emissions. Photo by Candler Hobbs.
By John Toon
By inserting a catalyst, hydrogen separating membrane, and carbon dioxide sorbent into the conventional four-stroke engine cycle, researchers have created a modular, hydrogen-reforming system that produces the green fuel from natural gas at relatively low temperature in a process that can be scaled up to meet specific needs.
The process could provide hydrogen at the point of use for residential fuel cells or neighborhood power plants; electricity and power production in natural gas-powered vehicles; or fueling of hydrogen-based vehicles. It could also supplement intermittent renewable energy sources.
Known as the CO2/H2 Active Membrane Piston (CHAMP) reactor, the device operates at temperatures much lower than conventional steam reforming processes, consumes substantially less water, and could also work with fuels such as methanol or bio-derived feedstocks.
“We already have a nationwide natural gas distribution infrastructure, so it’s much better to produce hydrogen at the point of use rather than trying to distribute it,” said Andrei Fedorov, a professor in Georgia Tech’s Woodruff School of Mechanical Engineering. “Our technology could produce this fuel of choice wherever natural gas is available, which could resolve one of the major challenges with the hydrogen economy.”
Key to the reaction process is the variable volume provided by a piston rising and falling in a cylinder. As with a conventional engine, a valve controls the flow of gases into and out of the reactor as the piston moves up and down. The system works like this:
• Natural gas (methane) and steam are drawn into the reaction cylinder through a valve as the piston is lowered. The valve closes once the piston reaches the bottom of the cylinder.
• The piston rises into the cylinder, compressing the steam and methane as the reactor is heated. Once the temperature reaches approximately 400 degrees Celsius, catalytic reactions take place inside the reactor, forming hydrogen and carbon dioxide. The hydrogen exits through a selective membrane, and the pressurized carbon dioxide is adsorbed by the sorbent material.
• Once the hydrogen has exited the reactor and carbon dioxide is tied up in the sorbent, the piston is lowered, reducing the volume and pressure in the cylinder. The carbon dioxide is released from the sorbent into the cylinder.
• The piston is again moved up into the chamber and the valve opens, expelling the concentrated carbon dioxide and clearing the reactor for the start of a new cycle.
A paper published in the journal Industrial & Engineering Chemistry Research describes the process. The research was supported by the National Science Foundation, the Department of Defense through NDSEG fellowships, and the U.S. Civilian Research & Development Foundation (CRDF Global).