The worldwide focus on clean power generation and carbon capture has increased the importance of the associated technologies, which involve two distinct approaches, namely pre-combustion and post-combustion carbon capture.
In pre-combustion CO2 capture, fuel is gasified by applying heat under pressure in the presence of steam and air and/or oxygen to form synthetic gas (Syngas). CO2 is then captured from the Syngas, before being mixed with air in a combustion turbine, resulting in the CO2 being relatively concentrated and at a high pressure.
In post-combustion CO2 capture, mainly, pulverized coal is burnt in air to raise steam. CO2 is exhausted in the flue gas at atmospheric pressure and concentrations of 10-15% v/v. This process is more challenging due to the low pressure and dilute CO2 concentration resulting in a high volume of gas having to be treated. Also trace impurities in the flue gas tend to reduce the effectiveness of the CO2 absorbing processes and compressing the captured CO2 from atmospheric pressure to pipeline pressure represents a large parasitic load.
Another post-combustion capture technology, oxy-combustion, involves combustion of the fuel with near pure oxygen resulting in a flue gas stream of higher CO2 concentration. This technology relates more to combustion, and is not discussed further in this paper.