precombustion

Precombustion refers to a set of processes applied to a fuel before combustion with the goal of reducing emissions, enabling carbon dioxide capture, or producing separate fuel streams such as hydrogen. In energy and industry, precombustion capture is a CCS approach in which fuel is converted into a synthesis gas (syngas) consisting mainly of hydrogen and carbon monoxide, through gasification or steam reforming. The syngas undergoes a water-gas shift reaction to convert CO to CO2 and produce additional H2. Carbon dioxide is then removed from the gas stream, typically by chemical absorption, pressure swing adsorption, or membranes. The resulting hydrogen-rich gas is then combusted or used as an industrial feedstock, while the separated CO2 is captured for storage or utilization.

Primary applications are new-build cycles such as integrated gasification combined cycle (IGCC) power plants that burn a clean, CO2-lean fuel after capture, and hydrogen production facilities where CO2 is captured from the reforming stream. BECCS (bioenergy with CCS) uses precombustion capture with biomass to achieve negative emissions.

Compared with post-combustion capture, precombustion capture generally allows CO2 to be captured at higher pressure and purity, potentially enabling lower energy penalties in new plants, but requires gasification or reforming equipment and substantial capital investment. It is less readily retrofitted to existing conventional steam turbines than post-combustion methods.

Limitations include higher complexity, cost, and feedstock dependence, as well as the need for robust gas cleanup to prevent turbine fouling. Ongoing research focuses on improving efficiency, lowering the cost of capture, and expanding applications beyond coal to natural gas and biomass.