Two new patented sorbents used for carbon dioxide (CO2) capture
from coal-based power plants have moved closer to commercialization as a result
of a licensing agreement between the Office of Fossil Energy’s (FE) National
Energy Technology Laboratory (NETL) and ADA Environmental Solutions (ADA-ES).
The nonexclusive agreement facilitates negotiations on intellectual property
rights, protects proprietary information, and grants non-exclusive licensing of
the new technology. Under federal regulations, NETL is authorized to obtain,
maintain, and own patent protection for its inventions, including those funded
through collaborative agreements. By granting a commercial license for these
sorbents, NETL can now convey and control the right to make, use, and sell the
products and services claimed in the patent, thereby assuring strategic
commercialization throughout the coal-fired power plant industry.
CO2 capture is an important component of carbon capture and
storage (CCS) technology, viewed by many experts as an integral part of a
portfolio strategy (including increased use of renewable and nuclear energy,
and greater efficiencies) for confronting increasing atmospheric carbon dioxide
emissions and potential climate change. Coal-based power and industrial plants
are essential to U.S.
energy production and are projected in many forecasts to remain so for the
foreseeable future. But they are also among the most carbon-intensive energy
FE’s comprehensive CCS research includes developing new materials that can
capture and release CO2 at reasonable energy and operating costs.
Traditional solvent-based systems consume too much energy, either in operation
or during regeneration of the solvents. So FE is developing and testing a wide
range of approaches.
A promising solution for affordable CO2 capture is “dry
scrubbing” or chemical absorption of CO2 using a solid
regenerable sorbent. The most important advantage of solid sorbents is the
potential to significantly reduce the amount of energy required to capture and
release CO2. These range from alkaline earth metal oxides or
hydroxides that can absorb CO2 at temperatures that typically range
from about 100 to 300 °C to impregnating a porous substrate with one of the
liquid solvents. In all of these, the sorbent can be regenerated in a
subsequent step, after the CO2 is removed. The efficiencies of these
processes are highly dependent on the optimum temperature and pressure
conditions at which absorption and regeneration are performed. In the case of
high-performance sorbents, both of these mechanistic steps occur with the
lowest possible energetic and operational costs.
In collaboration with ADA-ES and the Electric Power Research Institute
(EPRI), NETL in 2008 began testing candidates for solid-sorbent CO2
capture in coal-fired power plants. The initial research included a cost
analysis and sorbent screenings at both laboratory and pilot scales. Based on
the success of the initial phase, the research project moved to the technology
development and pilot-scale demonstration in 2010. The goals of this phase were
to demonstrate a ninety percent CO2 capture rate at a projected
long-term cost that would add less than a 35% increase to the cost of producing
The research resulted in two patents issued to NETL; specifically, U.S.
Patent No. 6,547,854, titled Amine Enriched Sorbents for Carbon Dioxide
Capture, and U.S. Patent No. 7,288,136, titled High Capacity Immobilized Amine
Sorbents. Both patents represent new methods for making low-cost CO2
sorbents that can be used in large-scale gas-solid processes. The first entails
treating a solid substrate with acid or base and a substituted amine salt,
eliminating the need for organic solvents and polymeric materials for the
preparation of CO2 capture systems. The second patent entails
treating an amine to increase the number of secondary amine groups and
impregnating the amine in a porous solid support. The method increases the CO2
capture capacity and decreases the cost of utilizing an amine-enriched solid
sorbent in CO2 capture systems.
Under a multi-year study examining ways to retrofit existing coal fired
power plants with carbon capture technology, NETL and its partners (ADA-ES, the
Electric Power Research Institute, and Southern Company) will continue to
demonstrate the sorbents in a 1 megawatt (about 24 tons CO2/day)
pilot-scale plant and conduct detailed engineering analysis to provide
technology cost estimates for post-combustion capture. In the demonstration,
solid sorbents are used to separate CO2 from flue gas. Once the
sorbents are saturated, they are processed to isolate purified CO2
for reuse or sequestration. The same process also regenerates the sorbents.
With initial reports showing a greater than ninety percent capture rate for the
patented solid sorbents, further refinements to the technologies and processes
surrounding this research offer great promise.