The US Department of Energy (DOE) announced of late that it is to provide $36m for 15 projects aimed at furthering the development of new cost-effective technologies for the capture of carbon dioxide (CO2) from the existing fleet of coal-fired power plants.

The announcement is part of the DOE’s Office of Fossil Energy’s Innovations for Existing Plants (IEP) programme, which is managed by the National Energy Technology Laboratory (NETL) – according to a report by NewsBlaze.com.

The 15 projects will focus on five areas of interest for CO2 capture, including membranes, solvents, sorbents, oxycombustion (flue gas purification and boiler development), and chemical looping.

US Secretary of Energy Samuel W. Bodman commented, “Currently, the existing US coal fleet accounts for over half of all electricity generated in this country. The projects announced today will combat climate change and help meet current and future energy needs by curbing CO2 emissions from existing coal-fired plants.”

Focus five
Of the five focus areas for CO2 capture, membrane-based capture uses permeable or semi-permeable materials that allow for the selective transport and separation of CO2 from flue gas. Research projects in this area will address key technical challenges to the use of membrane-based systems such as large flue gas volume, relatively low CO2 concentration, low flue gas pressure, flue gas contaminants, and the need for high membrane surface area.

Solvent-based CO2 capture involves chemical or physical sorption of CO2 from flue gas into a liquid carrier, with solvent-based systems in commercial use today as they scrub CO2 from industrial flue gases and process gases.

Solid particles can be used to capture CO2 from flue gas through chemical absorption, physical adsorption, or a combination of the two. Possible configurations for contacting the flue gas with the solid particles include fixed, moving, and fluidized beds. The projects selected in this area of interest will address key technical challenges to sorbent-based systems.

In terms of oxycombustion and flue gas purification, such systems combust a fuel in pure or almost pure oxygen, producing a flue gas that has high CO2 concentration but may also include water, excess oxygen, nitrogen, sulphur oxides, nitrogen oxides, mercury, and other contaminants.

Among the gas majors involved, Air Products and Chemicals Inc. will demonstrate the feasibility of purifying the CO2 derived from an actual oxycombustion flue gas - with special attention paid to acidic impurities within the captured CO2 product.

Praxair will also develop a near-zero emissions flue gas purification technology for existing pulverized-coal power plants, retrofitted with oxycombustion technology. The targets of this project are cited as cost-effectively capturing more than 95% of CO2 emissions from a boiler with high air ingress.

Atmospheric emissions of sulphur oxides and mercury will be reduced by at least 99%, and emissions of nitrogen oxides will be reduced by greater than 90% without the need for wet flue gas desulphurisation and selective catalytic reduction.

The characteristics of oxycombustion have not yet been fully developed and it is in boiler development that interaction of oxycombustion products with boiler materials will be analysed.

Chemical looping combustion involves the use of a solid oxygen carrier particle in the combustion of fuels and is also to form part of the development project initiative.