- Pre-combustion carbon capture is a method of capturing carbon dioxide (CO₂) before a fuel is burned, typically used in integrated gasification combined cycle (IGCC) power plants and various industrial processes. This approach involves converting fossil fuels (such as coal, natural gas, or biomass) into a mixture of gases, known as syngas (synthesis gas), primarily composed of carbon monoxide (CO) and hydrogen (H₂). Through subsequent chemical reactions, the CO is converted into CO₂, which is then separated and captured, while the hydrogen is used as a clean-burning fuel.
- The pre-combustion process begins with gasification or reforming, depending on the fuel source. In gasification, solid fuels like coal or biomass react with a controlled amount of oxygen and steam at high temperatures to produce syngas. In reforming, typically used for natural gas, methane reacts with steam to form syngas. This syngas then undergoes a water-gas shift reaction, where carbon monoxide reacts with steam to produce additional hydrogen and CO₂:
- CO + H₂O → CO₂ + H₂.
- After this shift reaction, the gas mixture contains a high concentration of CO₂ and hydrogen. The CO₂ is separated using physical or chemical solvents—such as amine-based solutions, physical solvents like Selexol or Rectisol, or adsorption techniques—and is then either compressed and stored underground (geological sequestration) or utilized in industrial processes (e.g., for enhanced oil recovery). The remaining hydrogen-rich gas can be burned in a gas turbine to generate electricity or used as a clean fuel in other applications, emitting only water vapor when combusted.
- One of the main advantages of pre-combustion capture is that it deals with high-pressure gas mixtures, making CO₂ separation more energy-efficient than in post-combustion systems. Additionally, the concentrated CO₂ stream allows for easier capture and purification. The use of hydrogen as a fuel also supports the transition to a low-carbon or hydrogen-based economy, as it can be integrated into power generation, heating, transportation, and industrial sectors.
- However, pre-combustion carbon capture also presents several challenges. It is best suited to new, specially designed facilities, such as IGCC power plants, and is generally more complex and capital-intensive than post-combustion retrofits. Retrofitting existing power plants for pre-combustion capture is typically not economically viable. Furthermore, the technology requires extensive integration and coordination between gasification, CO₂ separation, hydrogen purification, and combustion systems.
- Despite these challenges, pre-combustion carbon capture remains an attractive option for large-scale, centralized facilities, especially those looking to produce both low-emission power and hydrogen fuel. It is also a foundational component of blue hydrogen production, where hydrogen is derived from fossil fuels with CO₂ emissions captured and stored.
