Pre-combustion Capture is applicable to gasification including integrated gasification combined cycle power plants (IGCC), where solid fuel (i.e., coal) is converted into gaseous fuel (hydrogen and carbon monoxide, or “syngas”) by applying heat under pressure in the presence of steam and oxygen. The syngas is used to fuel a gas turbine generator to produce electricity. The recovered heat is used to produce steam that also drives a turbine generator designed to generate electricity. The carbon is captured from the syngas before it is combusted in the gas turbine.
In order to facilitate carbon capture and increase the hydrogen production, the syngas is shifted in a water-gas-shift (WGS) reaction to produce additional hydrogen and convert the carbon monoxide into carbon dioxide (CO2). In this case, the carbon is captured from the shifted syngas and afterward, the remaining hydrogen (H2) is combusted in a gas turbine that generates power.
Pre-combustion R&D efforts are focused on advanced solvents, solid sorbents, and membrane systems for the separation of H2 and CO2, with specific emphasis on high-temperature/novel materials, process intensification, and nanomaterials. Additionally, novel concepts, such as hybrid technologies that combine attributes from multiple technologies (e.g., sorbents and membranes) are being investigated.
Solvent-based CO2 capture involves chemical or physical absorption of CO2 from syngas into a liquid carrier and regenerating the absorption liquid by increasing the temperature or reducing the pressure to break the absorbent-CO2 bond. R&D objectives include modifying regeneration conditions to recover the CO2 at a higher pressure, improving selectivity to reduce H2 losses, and developing a solvent that has a high CO2 loading at a higher temperature to improve IGCC efficiency.
Sorbent technologies under development are aimed at improving the cost and performance of IGCC CO2 separation. R&D objectives are for sorbents to maintain a high adsorption loading capacity, be resistant to attrition over multiple regeneration cycles, and exhibit good performance at the high temperatures encountered in IGCC systems to avoid the need for syngas cooling and reheating.
Membrane technology options are under development to separate CO2 and H2 in coal derived syngas. Membrane designs include metallic, polymeric, or ceramic materials operating at elevated temperatures and using a variety of chemical and/or physical mechanisms for separation. R&D objectives are membranes that have high permeability and selectivity with low pressure drop, tolerance to contaminants (e.g., sulfur), and are capable of operation at system temperatures up to 500 °F.
Novel Concepts are under investigation and include hybrid systems that combine attributes from multiple technologies, novel process conditions (e.g., systems that operate at subambient temperatures), and nanomaterials. Technologies being considered include combining temperature-swing and pressure-swing regeneration to lower cost and energy penalties and integrating capture directly with the water-gas shift reaction to help drive equilibrium toward CO2 and H2 production while eliminating the need for syngas cooling