Carbon Sequestration
Pre-Combustion Capture Focus Area
Carbon dioxide (CO2) capture is defined as the separation of CO2 from emissions sources or from within the CO2 emission process. When CO2 is recovered from emissions sources, such as power plant flue gases, it is in a concentrated stream that is amenable to storage or conversion. Currently this process is costly and energy intensive, accounting for the majority of the cost of storage.
The Carbon Sequestration Program is focusing on developing technologies used to reduce the cost of capture and separation of CO2 in pre-combustion systems. Pre-combustion capture is mainly applicable to Integrated Gasification Combined Cycle (IGCC) power plants and refers to removal of the CO2 from the synthesis gas (syngas) prior to its combustion for power production. CO2 is concentrated and at a high pressure as a result. A simplified process schematic for pre-combustion CO2 capture is shown below. Near-term applications of CO2 capture from pre-combustion systems will likely involve improvements to the existing state-of-the-art physical or chemical absorption processes being used by the power generation industry.
|
| Schematic for Pre-Combustion CO2 Capture (click to enlarge) |
Pre-Combustion Capture Research Goals
Current state-of-the-art pre-combustion technologies would raise the cost of electricity by approximately 30 percent. The Carbon Sequestration Program goal is to identify technologies that would capture 90% of the CO2 generated and increase the cost of pre-combustion capture by no more than 10 percent. The program would then support projects to test the most promising technologies at a pilot scale level. DOE's system analyses have shown that the current portfolio of technologies have demonstrated progress toward meeting the cost targets at bench scale.
Integrating NETL's existing portfolio of technologies with other advanced IGCC system improvements has reduced the added cost of pre-combustion capture from 30 percent to 16 percent. Continued support of these and other technology efforts will keep DOE on track to have appropriate technologies for small-scale pilot testing to begin addressing scale-up and integration issues.
Pre-Combustion CO2 Capture Technologies
The Carbon Sequestration Program is focusing on mid- and long-term technology solutions that offer opportunities to dramatically reduce the costs associated with pre-combustion capture. The program is currently funding the development of several advanced pre-combustion CO2 capture technologies that have the potential to provide improvements in both cost and performance over current state-of-the-art technologies. Three technology areas show significant promise and could be integrated into IGCC systems, including:
| |
Application |
| |
- Solvents are sought that readily dissolve CO2, have a high CO2 adsorption capacity and are regenerated at higher pressure. Solubility is directly proportional to CO2 partial pressure and inversely proportional to temperature, making physical solvents more applicable to low temperature, high-pressure applications (cooled syngas). Solvent regeneration normally occurs by pressure swing.
Existing solvents are operational at scale, but are not cost effective.
|
| |
Research Focus |
| |
- Increase solvent loading capacity to reduce energy demand and capital costs.
- Increase temperature and pressure operating window for solvent to reduce energy demand and compression requirements.
- Reduce impacts of co-contaminants and temperature on solvent degradation.
- Increase CO2 selectivity.
|
| |
Collapse Text |
| |
Application |
| |
- Sorbents that have a higher CO2 adsorption capacity and regenerate at higher pressure are sought. When sorbent pellets are contacted with syngas, CO2 is physically adsorbed onto sites and/or dissolved into the pore structure of the solid sorbent. Rate and capacity are directly proportional to CO2 partial pressure, making these sorbents more applicable to high pressure applications. Regeneration normally occurs by pressure swing.
|
| |
Research Focus |
| |
- Address pressure drop of CO2 during flash recovery.
- Reduce energy requirements needed to cool syngas for CO2 capture and heating and re-humidify for firing to turbine.
- Increase recovery of hydrogen (H2) during CO2 capture.
|
| |
Collapse Text |
| |
Application |
| |
- A membrane material which selectively allows H2 or CO2 to permeate is used in gasification operations with concentrated streams of H2 and CO2. Membranes are sought that are capable of operating at higher temperatures and pressures and do not require cooling and reheating of gas streams. They also would produce CO2 at higher pressure than conventional technology.
In a solvent hybrid system, the syngas is contacted with a membrane, and a solvent on the permeate side absorbs CO2 and creates a partial pressure differential to draw CO2 across the membrane.
|
| |
Research Focus |
| |
- Develop novel materials that would reduce material and manufacturing costs.
- Examine impacts of co-contaminants, temperature, and pressure on membranes and solvents.
- Improve selectivity to increase purity of CO2.
- Improve permeability to decrease pressure drop.
|
| |
Collapse Text |
Information on the active pre-combustion capture projects receiving DOE funds that aim to obtain these goals for the Carbon Sequestration Program is provided in the following table.
|
ABOUT NETL
Deepwater Technology
