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.

Accelerated Carbonation of Coal Combustion Fly Ash for Atmospheric Carbon dioxide Sequestration and Soil Amendment: An Overview

“…For example, CaO has been found to be carbonated on a time-scale of one minute at temperatures above 550°C [49]. However, if the temperature is raised too much, the solubility of CO 2 in water is lowered since the higher kinetic energy causes more motion in molecules which breaks the intermolecular bonds between CO 2 and water, and allows CO 2 to escape from the solution [50][51][52][53]. In this way, the chemical equilibrium is shifted such that free CO 2 is favoured over the bound form.…”

“…However, for materials of low solubility in which CaO is bound as silicates, the accelerated carbonation is best carried out in a slurry phase with a liquid-to-solid ratio of greater than one [38,51]. Reddy et al [53] examined the possibility of point-source capture of the flue gas CO 2 with coal FA generated in the same plant [37]. They found that the moisture content of the flue gas is the most important factor that governs the mineralization of the FA particles.…”

“…In addition, the low bulk density of FA makes it a suitable additive to improve the bulk density of soils in a mixture [19]. The Ca 2+ from FA promotes flocculation between soil particles and helps to maintain a desirable level of soil aggregation through cation bridging, particularly in clay soils [29,53]. The structural and textural changes in soil upon FA addition increase water retention capacity in sandy soils and hydraulic conductivity in clay soils [22,31,54].…”

Microbial Carbonic Anhydrases in Biomimetic Carbon Sequestration for Mitigating Global Warming: Prospects and Perspectives

“…Mineral carbonation is being studied at length for its utility in biomineralization of CO 2 from flue gas. Some pilot scale studies have already been undertaken to demonstrate the viability of the process (Reddy et al, 2010 ).…”

CO2 mineral sequestration: developments toward large‐scale application

“…Similar results were obtained using either seawater or dilute NaHCO 3 as the carrier solution. 94 • A recent patent and results presented by Reddy et al 95,96 involves a method of simultaneously sequestering and storing Hg, SO 2 , and CO 2 by reacting an alkaline material (e.g. fl y ash from a coal-fi red plant, steel slag, paper mill waste ash) with a fl ue gas containing these species.…”