Instantaneous Capture and Mineralization of Flue Gas Carbon Dioxide: Pilot Scale Study

Abstract

-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 2-in 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.

Field Application of Accelerated Mineral Carbonation

“…Additionally, increasing the AMC reaction to industrial scale would be needed to determine if it is cost effective and efficient [42]. Fly ash and flue gas conditions vary between different power plants and studies with differing conditions would elucidate if the AMC process works elsewhere.…”

“…For these reasons, the removal of CO 2 and SO 2 from the flue gas was calculated based on C and S contents of control and treated fly ash samples. A detailed description of the demonstration scale AMC process is available in Reddy et al [42,43]. Fly ash solubility and fractionation data from a pilot scale AMC process at JBPP, smaller than the current demonstration scale conducted at JBPP, is detailed in Bhattacharya et al [44].…”

“…The flue gas is relatively low in SO 2 (20-25 ppm) and NO x (100-120 ppm) concentrations, contains 11-13.5 mol % CO 2 , 66-70 mol % N 2 , 10-20 mol % moisture and trace amounts of Hg, As, and various other trace elements. The pH of the flue gas is 3.3 [41,42].…”

“…A small pilot scale AMC process was successfully tested at a large coal power plant prior to the current demonstration scale AMC process [41]. The AMC process has shown promise not only in removing flue gas CO 2 , but also SO 2 and Hg, as well as minimizing the mobility and leaching of trace elements in the fly ash [42][43][44]. However, for this current study, we made several modifications to the demonstration apparatus ( Figure 1).…”

Commentary: Ex Situ Aqueous Mineral Carbonation

“…These studies have formed the basis for understanding CO2 interactions with calcium and magnesium silicates that extend beyond the laboratory to the demonstration scale (Reddy et al, 2010;Kelly et al, 2011;Zevenhoven et al, 2011;Hitch and Dipple, 2012;Brent, 2015) and toward geological carbon storage (Kelemen and Matter, 2008;Matter and Kelemen, 2009;Schaef and McGrail, 2009;Gislason et al, 2010;Rosenbauer et al, 2012). The studies performed at NETL-Albany have also been extensively cited in studies for the accelerated carbonation of industrial alkaline wastes [Pan et al (2012), Gadikota and Park (2014), Sanna et al (2012), and references contained therein].…”