CO2 capture

CO2 capture is a technique that is already used at the industrial level. For example, at the moment natural gas is produced, it is processed to extract any naturally present CO2. Although CO2 capture technology already exists, its application to industrial sources is not yet widely developed.

At the present time, there are several ways to capture CO2. Each of the technologies presented below require compressors to compress the captured CO2 into a supercritical state before it enters the transportation network.

Where will CO2 be captured?

cheminees_industrielles_3_petit

According to the IPCC, more than half the CO2 emissions around the world are produced by concentrated and localized sources known as “major emitters” (IPCC, 2005). These include, for example, thermal power plants, cement plants, refineries, iron and steel factories, and aluminum factories. We generally consider an industrial facility to be a major emitter when its annual CO2 emissions equal or exceed 100,000 tonnes of CO2. The CCS process is particularly well suited to major emitters.

Capture technologies

(Source : Lecomte, F., Broutin, P., Lebas, E. (éd.) Le captage du CO2 – Des technologies pour réduire les émissions de gaz à effet de serre. IFP Publications, Paris, France, 204 pages)

Post-combustion capture

postcombustion_eng

Post-combustion CO2 capture technology is considered to be the most promising solution at the industrial level. It covers all the operations that extract diluted CO2 from smokestack emissions produced by combusting fossil fuels (coal, natural gas, oil) or biomass in the presence of air (Lecomte, 2010). There are several different processes for post-combustion capture, the most common right now being CO2 capture by amines acting as of chemical solvents.

The capture unit can be added to existing facilities, which makes for an interesting option because it can apply to different types of industries. It must be kept in mind, however, that the existing facility may need to be significantly modified and that implementing this option will increase the energy consumption of the facility as a whole. The process must be improved before this technology can be widely used at the industrial level.

Capture via oxycombustion

oxycombustion_eng

CO2 capture via oxycombustion is currently at the demonstration stage (for example, at the Total pilot project in France). This technique aims to increase the CO2 content in smokestack emissions by using oxygen instead of air during combustion (Lebas, 2010). It is then a relatively straightforward procedure to separate CO2 from other components in the emissions (mostly water vapour) This technique not only requires modifications to existing facilities but also a continuous supply of pure oxygen.

Pre-combustion capture

precombustion_eng

Pre-combustion CO2 capture consists of extracting CO2 “at the source” by transforming a fuel into a synthetic gas that is a mixture of carbon monoxide (CO) and hydrogen (H2). The synthetic gas is then processed to increase hydrogen production and in so doing, CO2 is formed. The CO2 is separated from the hydrogen and the latter is burned at a thermal plant adapted for zero-CO2 emissions. (Broutin, 2010)

Next step: CO2 transport.