CO2 capture in power plants
Pre combustion: CO2 is captured before the combustion of the fuel.
Post combustion: CO2 is captured after the combustion of the fuel.
Both of these processes primarily use solvents or membranes to separate the CO2 from the flue gases.
Oxy combustion: CO2 is captured after combustion but the fuel is burnt with nearly pure oxygen (up to 97%) instead of air as in post combustion.
CO2 capture in industry
22% of the CO2 emissions in Europe (EU Energy in Figures 2010, European Union) come from the industry sector such as gas processing, steel and cement works and glass making. CO2 can be removed from the emissions gases produced by industry using solvents and membranes in similar processes to power plants.
The main technologies for removing CO2 from a process stream are:
- CO2 stripping, or scrubbing, usually using absorbent solvents, adsorbents or membranes.
- Cryogenic separation, where the gas stream is transformed into liquid after a series of compression and expansion, and the components of interest are separated with distillation.
- Clean hydrogen production, where using a water-gas shift reaction process on a syngas process stream. CO2 rich stream is produced which can then be separated using solvents, adsorbents or membranes.
Within each of these basic capture technologies there are multiple design choices, all impacted by the type of fuel being used, the environmental conditions, the availability of resources (such as water) at the chosen locations, and the operational requirements of the plant.
Compostilla project would use Flexi-Burn (a flexible air/oxygen) circulating fluidised bed (CFB) technology. The academic partner in the project (Ciuden) successfully commissioned a 30MWth boiler and testing so far has yielded promising results.
Don Valley project has contracted the company BOC and its parent company Linde to supply the carbon capture technology and air separation units (ASUs) for the CCS plant. The FEED study for the plant is on-going.
ROAD project has completed the design of the capture unit and will be using primary amines in post-combustion.
Sleipner makes use of an advanced amine high-pressure absorption/desorption technique without fuel conversion (i.e. no combustion).