Carbon Capture and Storage
The Absorber in the Smokestack: Can Chemistry Stop Climate Change?
A Reactor in the Pipe
CO2 separation can, of course, also take place downstream with an integrated gas-scrubbing in the exhaust pipe. For this purpose, one idea is to transfer amine scrubbing from natural gas treatment to power-station exhaust flues. In this process, CO2 accumulates on fine amine droplets which are separated and regenerated. Due to the necessary regeneration and "dragging along" of atmospheric nitrogen, energy requirements are high: the energy consumption of a coal fired power station rises by 30 %–40 % due to post-combustion technology, experts say.
Now chemical absorption processes shall push CO2 separation to the next level: At the "International Conference on Distillation and Absorption" in Friedrichshafen the topic occupied a top place. A research group of Eon presented experiences in dealing with flue gas contaminations. In particular, hydrogen sulphide (H2S), nitrogen oxide and sulphur dioxide (SO2) react irreversibly with the scrubbing agent and must therefore be removed beforehand. Yet, a steady loss of solvents, termed "slippage", is inevitable. As a result, a certain quantity of fresh scrubbing agent (6 kg to 0.35 kg amine per tonne CO2) must be added constantly. And not only the solvents age: Remains of oxygen in flue gas can lead to oxidation of the amines and thus limit solvent activity.
Can CCS stop climate change? The technology is by no means a cure-all, but could make an important contribution. Thus not only constructors and electrical engineers, but also process technology could hold the key to the power station of the future – thanks to the absorber in the smokestack.