New Carbon Capture Method for Energy Industry

A new industrial CO2 scrubbing process could provide the energy industry with a cheaper method of carbon capture than is used at present.

Scrubbers are anti-air pollution devices that come in various forms. Wet scrubbers spray liquid such as water, while dry scrubbers inject slurry into an exhaust flow. Mechanically aided scrubbers, meanwhile, are similar to wet scrubbers, but with an added motor.

CO2 Scrubbing

Compared to current CO2 scrubbing processes, the new method guarantees a CO2 removal rate of as much as 90 per cent, while consuming much less in the way of energy, and trials of the procedure are set to take place in coming months.

Carbon capture is unavoidably energy-consuming. On this premise, the challenge, then, is to identify ways through which such energy consumption is minimised, rather than obliterated, and this is where the new technology comes in to play.

Present carbon-capture techniques result in about an eleven per cent efficiency drop for the power-plant concerned. The new, Siemens-developed method offers the possibility of cutting this figure down by 1.8 per cent. While this kind of differential might appear minimal, in industrial terms, it is significant and, according to Siemens’ Tobias Jockenhoevel, a “huge benefit”.

On paper, the new process could work on removing 99.9 per cent of power plant-generated CO2 but, according to Jockenhoevel, “the last 10 per cent costs too much”. In other words, the balance between cost and energy efficiency is at its best at 90 per cent, and no more.

Carbon Absorption

Siemens’ method will be put through its paces in August at a dedicated site in Germany. The plant at this site will be modified to enable a portion of its gases to be directed into a chimney containing a column extending to 25 metres in height. The column emits a solvent mist that, when pressurised, enters into a reaction with CO2. When the gases created by the flue move through the mist, the carbon is absorbed, meaning just the residual gases make it out of the chimney. Separation of the CO2 from the solvent then occurs.

The process, according to Jockenhoevel, is “...basically like washing the gases.” The method itself is comparable to that usually performed by a CO2 scrubber – the difference here lies in the type of solvent employed and the techniques involved in the recovery process.

The industry standard in terms of solvents is MEA (monoethnolamine), but, in the Siemens method, amino acid salts will be used instead.

Compared to MEA, the amino acid salts offer improved stability and reduced volatility, meaning the amount of solvent emitted into the atmosphere should be close to zero.

All fossil fuel-powered plants will be able to incorporate the technology, said Jockenhoevel, while modifications can be made to those that can't.

On the downside, the upcoming trials, even if successful, will be years ahead of these kinds of methods actuallly entering the mainstream – a situation caused by factors including the high price of carbon, as well as complications associated with CO2 storage.