'Scrubbing' gases of power stations
Australia currently generates 85 per cent of its electricity by burning coal, resulting in 170 million tonnes of CO2 entering the atmosphere each year. Although alternative energy is slowly coming on line, coal is likely to provide some of our power for the foreseeable future, but that’s not to say that coal can’t clean up its act.
Dr Rowena Ball is an applied mathematician and physical chemist, currently working on the mathematics of the complex thermo chemistry and kinetics involved in flue gas CO2 capture.
Carbon capture involves two main processes. The first is the 'scrubbing', or selective removal of carbon dioxide from the mixture of flue gases in the emissions stream. The second is 'sequestration' – the stable, longterm geologic storage of the compressed pure carbon dioxide.
In collaboration with an Australian company, Calix Ltd, Ball is developing a novel looping technique to scrub the flue gases of power stations. The team is refining what’s known as an Endex reactor, based on some initial work Rowena did back in the 1990s. In the Endex reactor, CO2 is adsorbed by calcium oxide to form synthetic limestone, a reaction that is exothermic, so generates large amounts of heat. The second stage is desorption of pure carbon dioxide from this limestone, a reaction which is endothermic so requires a lot of heat energy to drive it.
The clever part about the Endex reactor is that the adsorption and desorption reactions are coupled thermally and matched kinetically, meaning that the energy generated by the exothermic first stage is harnessed directly to drive the endothermic second stage making the process highly energy efficient and therefore cheap. The system can be retrofitted to existing power plants.
“Endex carbon capture is an interesting example of how high quality fundamental mathematics research can turn out to have important applications to new problems,” Ball says.