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Pre‐combustion systems can be applied to natural gas combined cycles (NGCC) or integrated gasification combined cycle (IGCC) (Figure 1.1), where a syngas, comprising mainly CO and H₂, feeds a gas turbine (GT) combined cycle system to produce electricity. The potential advantages are higher conversion efficiencies of coal to electricity and cheaper removal of pollutants [8]. The syngas, based on the water shift reaction, can be converted into CO₂ and H₂O. This mixture is typically separated with physical solvents (as described in Section 1.2.4), membranes, or sorbents. However, hybrid technologies can also be used. Depending on the technology, further post‐treatment would be needed to avoid degradation and loss of efficiency.

The main theoretical advantage of pre‐combustion is the production of hydrogen, which will add value to the business model, and a lower energy penalty compared to using the traditional chemical absorption within a post‐combustion configuration. However, large projects demonstrated that this difference is only 1–2%, as reported by National Energy Technology Laboratory (NETL) [9].

The most notable pre‐combustion project was the Kemper County IGCC plant in the United States, which stopped its operation in 2017.This demonstration facility would place this arrangement at high TRL, while other testing campaigns would reach up to a TRL of 6.

Figure 1.1 Diagram of pre‐combustion capture for power generation in IGCC.

Source: Adapted from Jansen et al. [72].