Investigation of regenerable sorbents for CO{sub 2} capture

Conference · Thu Jul 01 04:00:00 EDT 1999

OSTI ID:20082395

Hoffman, J S; Pennline, H W

An experimental investigation was undertaken in pursuit of identifying novel dry, regenerable scrubbing processes for the capture of CO{sub 2} from a gaseous stream. Recent investigations by Japanese researchers have identified supported alkali carbonate materials that can remove CO{sub 2} in the presence of water vapor to form an alkali bicarbonate. The sorbent is thermally regenerated by heating, yielding CO{sub 2} and H{sub 2}O as products. Conceptually, the water could be condensed and separated from the gaseous product stream of regeneration, yielding a concentrated stream of CO{sub 2} to be further processed into either a usable byproduct or disposed of as a waste. A bench-scale microbalance study of prepared sorbents was performed by exposing the sorbents initially to CO{sub 2}, followed by thermal regeneration. The experimental approach involved utilizing a thermogravimetric analyzer (TGA) to track sorbent weight change as the material was exposed to gases under conditions representative of absorption or regeneration. Change in sorbent weight was linked to the extent of chemical reaction, from which kinetic rate information was extracted. By conducting parametric evaluations of prepared sorbents, the impact of temperature and flue gas components on the absorption chemistry was studied. Temperature, and possible reducing agents, were investigated for the regeneration chemistry. Sorbents were prepared by impregnating various alkali- and alkaline-earth materials onto a substrate composed of high-surface area activated alumina. The first sorbent studied consisted of potassium carbonate deposited on alumina. Alkaline earth sorbents would likely include the investigation of magnesium and calcium materials. A preliminary thermodynamic analysis was conducted for some proposed sorbents of interest. Enthalpy and free energy changes were calculated for both absorption and regeneration reactions. Equilibrium constants were formulated over a temperature range of 77--212 F. Results for alkali-based sorbents are generally favorable in that the forward (CO{sub 2} absorption) reaction rate is typically much larger than the reverse reaction. Per the Japanese study using potassium, the absorption reaction of KOH with CO{sub 2} to form KHCO{sub 3} was calculated to be extremely favorable over the reverse reaction.

• Research Organization: US Dept. of Energy, Pittsburgh, PA (US)
• OSTI ID: 20082395
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
20 FOSSIL-FUELED POWER PLANTS
ADSORBENTS
ADSORPTION
ALKALI METALS
ALKALINE EARTH METALS
CARBON DIOXIDE
CHEMICAL REACTION KINETICS
FLUE GAS
PERFORMANCE TESTING
REGENERATION
SCRUBBING
THERMODYNAMICS