CO2 Capture Project Descriptions Thermally Optimized Membranes for Separation and Capture of CO2 Carbon Dioxide Capture from Flue Gas Using Dry Regenerable Sorbents CO2 Capture for PC-Boiler Using Flue-Gas Recirculation: Evaluation of CO2 Capture/Utilization/Disposal Options Greenhouse Gas Emissions Control by Oxygen Firing in Circulating Fluidized-Bed Boilers Oxygen-Fired CO2 Recycle for Application to Direct CO2 Capture from Coal-Fired Power Plants Carbon Dioxide Capture by Absorption with Potassium Carbonate Advanced Oxyfuel Boilers and Process Heaters for Cost Effective CO2 Capture and Sequestration Conceptual Design of Oxygen-Based PC Boiler Conceptual Design of Optimized Fossil Energy Systems with Capture and Sequestration of CO2 Combined Power Generation and Carbon Sequestration Using a Direct FuelCell® Reference Shelf

CO₂ capture is the separation of CO₂ from emissions sources or the atmosphere and the recovery of a concentrated stream of CO₂ that is amenable to sequestration or conversion. The program currently funds a relatively large number of laboratory-to-pilot-scale research projects involving chemical sorbents, physical sorbents, membranes, hydrates, and other approaches.  Efforts are focused on systems for capturing CO₂ from coal-fired power plants, although the technologies developed will be applicable to natural-gas -fired power plants, industrial CO₂ sources, and other applications. 

Pulverized coal (PC) plants, which are 99 percent of all coal-fired power plants in the United States, burn coal in air to raise steam. 
CO₂ is exhausted in the flue gas at atmospheric pressure and a concentration of 10-15 volume percent.  This post-combustion
capture of CO₂ is a challenging application because:

• The low pressure and dilute concentration dictate a high actual volume of gas to be treated
• Trace impurities in the flue gas tend to reduce the effectiveness of the CO₂ adsorbing processes
• Compressing captured CO₂ from atmospheric pressure to pipeline pressure (1,200–2,000 pounds per square inch (psi)) represents a large parasitic load.

Aqueous amines are the state-of-the-art technology for CO₂ capture for PC power plants.  Analysis conducted at NETL shows that CO₂ capture and compression using amines raises the cost of electricity from a newly-built supercritical PC power plant by 84 percent, from 4.9 cents/kWh to 9.0 cents/kWh.  The goal for advanced CO₂ capture systems is that CO₂ capture and compression added to a newly constructed power plant increases the cost of electricity by no more than 20 percent compared to a no-capture case. 

Integrated gasification combined cycle (IGCC) is an exciting and emerging technology for coal power, offering the potential for higher efficiency and reduced cost of pollutant emissions control.  From the perspective of carbon sequestration, CO₂ can be captured from a synthesis gas (coming out of the coal gasification reactor) before it is mixed with air in a combustion turbine. This is referred to as pre-combustion CO₂ capture. The CO₂ is relatively concentrated (50 volume %) and at high pressure.  These conditions offer the opportunity for lower cost CO₂ capture. 

The state-of-the-art for CO₂ capture from an IGCC power plant is glycol-based Selexol sorbent.  Analysis conducted at NETL shows that CO₂ capture and compression using Selexol raises the cost of electricity from a newly built IGCC power plant by 25 percent, from 5.5 cents/kWh to 6.5 cents/kWh.  The goal for advanced CO₂ capture and sequestration systems applied to an IGCC is no more than a 10 percent increase in the cost of electricity.  It is a more stringent goal given that the conditions for CO₂ capture are more favorable in an IGCC plant.

Oxygen Combustion (oxy-combustion) combusts coal in an enriched oxygen environment using pure oxygen diluted with recycled CO₂ or H₂ O. The CO₂ is then captured by condensing the water in the exhaust stream. Oxy-combustion offers several benefits as determined through large-scale laboratory testing and systems analysis. Oxy-combustion results in a 60-70 percent reduction in NOx emissions and increased mercury removal. Also, oxy-combustion’s key process principles have been demonstrated commercially, including air separation and flue gas recycle. The oxygen required for oxy-combustion increases costs, but novel oxygen separation techniques such as ion transport membranes and chemical looping systems are being developed to reduce costs.