Carbon Capture Technologies
Post combustion: Separation of CO2 from flue gases after combustion of fossil fuels
As flue gases mainly consist of carbon dioxide, Sulphur oxides, Nitrous oxides and water , post combustion process includes separation of CO2 from these exhaust gases. The most commonly used procedure is passing CO2 rich gas stream through amine based solvents. Before this gas stream is bubbled through amine solution, the gas is cooled and cleaned to remove other impurities. As shown in figure below there are two types of solvents :
Solvent scrubbing, e.g. MEA, KS-1, MDEA, chilled ammonia (TRL = 6) :High energy requirements, high degradation rates, environmentally hazardous solvent degradation products, potential problems due to equipment corrosion, requires very large equipment.
Low-temperature solid sorbents, e.g. supported amines (TRL = 2–3): Relatively low capture capacity, no experience under realistic conditions.
As flue gases mainly consist of carbon dioxide, Sulphur oxides, Nitrous oxides and water , post combustion process includes separation of CO2 from these exhaust gases. The most commonly used procedure is passing CO2 rich gas stream through amine based solvents. Before this gas stream is bubbled through amine solution, the gas is cooled and cleaned to remove other impurities. As shown in figure below there are two types of solvents :
- CO2 scrubbing column – This column kept at about 80˚C .The solvent in this column absorbs 90% of CO2 as amine based solvent gets bonded with CO2 and it passes other gases further.
- Solvent regeneration column – This column kept at about 120 ˚C. Co2(99%pure CO2) will be absorbed from the saturated amine solution and compressed for storage purpose. The amine solvents can be recycled and reused.
Solvent scrubbing, e.g. MEA, KS-1, MDEA, chilled ammonia (TRL = 6) :High energy requirements, high degradation rates, environmentally hazardous solvent degradation products, potential problems due to equipment corrosion, requires very large equipment.
Low-temperature solid sorbents, e.g. supported amines (TRL = 2–3): Relatively low capture capacity, no experience under realistic conditions.
Pre combustion: This process includes separation of CO2 before solid / liquid combustion such as coal , biomass or petrochemicals. These fuel products undergoes gasification in a chemical reaction at high temperature with controlled amount of oxygen (O2). After complete combustion a gas also known as syngas which primarily comprises carbon monoxide(CO),hydrogen (H2),methane (CH4) and carbon dioxide(CO2) is produced. By heating the mixture of gases in reforming reactors , output gases will be mixture of H2 and CO2. Afterwards CO2 is compressed for storage purposes and pure H2 can be used to generate electricity.
Oxyfuel Combustion: Oxyfuel burning includes burning of a fossil fuel in the presence of pure oxygen .Burning fuel in the presence of oxygen removes contaminants, including nitrogen, from those exhaust gas stream. This constant removal of contaminants will make capturing of CO2 easier. Air will be purified in Air separation unit where oxygen (O2) gets separated. The pure oxygen (O2) will be after that combusted with the fuel . The burning will result in flue gas comprising steam and CO2. Steam will be used to run a turbine to generate electricity or in other industrial applications. The CO2 can be captured and compressed for storage.