Pre-combustion capture refers to removing CO2 from fossil fuels before they are burned (or combusted) in a power plant. For example, in gasification processes a feedstock (such as coal) is partially oxidized in steam and oxygen/air under high temperature and pressure to form synthesis gas, a mixture of hydrogen, carbon monoxide, CO2, and smaller amounts of other gaseous components such as methane. This synthesis gas can then undergo the water-gas shift reaction to convert CO and water (H2O) to H2 and CO2, producing a H2 and CO2-rich gas mixture. The concentration of CO2 in this mixture can range 15-50%. The CO2 can then be captured and separated, transported, and ultimately sequestered, and the H2-rich fuel combusted.

Compared to post-combustion technology, which removes dilute CO2 (~5-15% CO2 concentration) from flue gas streams and is at low pressure, the shifted synthesis gas stream is rich in CO2 and at higher pressure, which allows for easier removal before the hydrogen is combusted. Due to the more concentrated CO2, pre-combustion capture typically is less expensive but the capital costs of the base gasification process are often more expensive than traditional pulverized coal power plants.

Today’s commercially available pre-combustion CCS technologies generally use physical or chemical adsorption processes, and will add around 35 percent to the cost of electricity for an integrated gasification combined cycle (IGCC) power plant. The goal of our research efforts is to reduce the increase in cost of electricity to 10 percent. Our research focuses on three key separation technologies – advanced solvents, sorbents, and membranes – in order to meet this goal.

The pre-combustion capture research activities will coordinate closely with the gasification and hydrogen turbine programs to ensure that pre-combustion capture technologies can be successfully integrated into an IGCC facility. Advances in those programs will also help meet the goal of limiting the cost of pre-combustion capture to a 10 percent increase in cost of electricity.