Instantaneous Capture and Mineralization of Flue Gas Carbon Dioxide: Pilot Scale Study (original) (raw)

Multiple CO 2 capture and storage (CCS) processes are required to address anthropogenic CO 2 problems. However, a method which can directly capture and mineralize CO 2 at a point source, under actual field conditions, has advantages and could help offset the cost associated with the conventional CCS technologies. The mineral carbonation (MC), a process of converting CO 2 into stable minerals (mineralization), has been studied extensively to store CO 2 . However, most of the MC studies have been largely investigated at laboratory scale. Objectives of this research were to develop a pilot scale AMC (accelerated mineral carbonation) process and test the effects of flue gas moisture content on carbonation of fly ash particles. A pilot scale AMC process consisting of a moisture reducing drum (MRD), a heater/humidifier, and a fluidized-bed reactor (FBR) was developed and tested by reacting flue gas with fly ash particles at one of the largest coal-fired power plants (2120 MW) in the USA. The experiments were conducted over a period of 2 hr at ~ 300 SCFM flow-rates, at a controlled pressure (115.1 kPa), and under different flue gas moisture contents (2-16%). The flue gas CO 2 and SO 2 concentrations were monitored before and during the experiments by an industrial grade gas analyzer. Fly ash samples were collected from the reactor sample port from 0-120 minutes and analyzed for total inorganic carbon (C), sulfur (S), and mercury (Hg). From C, S, and Hg concentrations, %calcium carbonate (CaCO 3 ), %sulfate (SO 4 2-), and %mercury carbonate (HgCO 3 ) were calculated, respectively. Results suggested significant mineralization of flue gas CO 2 , SO 2 , and Hg within 10-15 minutes of reaction. Among different moisture conditions, ~16% showed highest conversion of flue gas CO 2 and SO 2 to %CaCO 3 and %SO 4 2in fly ash samples. For example, an increase of almost 4% in CaCO 3 content of fly ash was observed. Overall, the AMC process is cost-effective with minimum carbon footprint and can be retrofitted to coal fired power plants (existing and/or new) as a post-combustion unit to minimize flue gas CO 2 , SO 2 , and Hg emissions into the atmosphere. Used in conjunction with capture and geologic sequestration, the AMC process has the potential to reduce overall cost associated with CO 2 separation/compression/transportation/pore space/brine water treatment. It could also help protect sensitive amines and carbon filters used in flue gas CO 2 capture and separation process and extend their life.