Gasi-fuel cell combo doubles coal efficiency

ENGINEERS at MIT have proposed a system to drastically boost the efficiency of producing power from coal – by combining gasification with fuel cell technology.

Simulations carried out by doctoral student Katherine Ong and professor Ahmed Ghoniem, director of MIT’s Centre for 21st Century Energy, suggest combining the technology could double to 60% the fuel-to-electricity efficiency compared with conventional coal-fired power.

The team proposes a system where the syngas produced by gasifying pulverised coal is fed to a solid oxide fuel cell to produce electricity. Ideally, the fuel cell system would be installed in the same chamber as the gasifier so that the gas flows straight to the fuel cell. Here a membrane separates carbon monoxide and hydrogen in the syngas from oxygen, causing an electrochemical reaction that generates electricity without burning the fuel.

Ong says that combining the two systems would be beneficial, as both processes operate at a similar temperature – around 800?C. This would allow both to exchange heat with reduced losses and eliminate the need for a separate heating system to sustain the gasification process.

The team says the research progresses previous efforts to simulate the combination of the technologies and shows that using steam to react with coal – rather than CO₂ used in other studies – could triple power output.

Furthermore, the system doesn’t truly burn the coal so reduces the production of ash and other air pollutants, and it produces a pure stream of CO₂ eliminating the need to strip out nitrogen as with capture from conventional coal-fired plants.

Ong says the next step is to build a pilot plant. A full-scale operational plant is feasible within two years, she says, because the component technologies are fully developed.

“It’s just a matter of coupling these existing technologies together well.”

Ong concedes the system would be more expensive than conventional coal-fired power but reasons the added efficiency would offset the capital investment within several years.

“If we’re going to cut down on CO₂ emissions in the near term, the only way to realistically do that is to increase the efficiency of our fossil fuel plants,” she says.

Journal of Power Sources doi.org/bd25