Abstract
AbstractMultiple CO2 capture and storage (CCS) processes are required to address anthropogenic CO2 problems. However, a method which can directly capture and mineralize CO2 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 CO2 into stable minerals (mineralization), has been studied extensively to store CO2. 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 CO2 and SO2 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 (CaCO3), %sulfate (SO42-), and %mercury carbonate (HgCO3) were calculated, respectively. Results suggested significant mineralization of flue gas CO2, SO2, and Hg within 10-15 minutes of reaction. Among different moisture conditions, ~16% showed highest conversion of flue gas CO2 and SO2 to %CaCO3 and %SO42- in fly ash samples. For example, an increase of almost 4% in CaCO3 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 CO2, SO2, 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 CO2 separation/compression/transportation/pore space/brine water treatment. It could also help protect sensitive amines and carbon filters used in flue gas CO2 capture and separation process and extend their life.
Highlights
Coal reserves are crucial for providing global energy needs
The objectives of this research were to 1) develop a pilot scale study for further testing to determine the feasibility of proposed the accelerated mineral carbonation (AMC) process, 2) determine the effect of temperature and moisture content of flue gas on the AMC process, 3) evaluate cost-economics of the AMC process and its potential benefits to CO2 capture and storage (CCS) processes, and 4) determine the significance of coal combustion ash in mineralization of flue gas CO2
Since the AMC process captures and mineralizes SO2, it could help protect and extend life of sensitive amines and carbon filters used in flue gas CO2 capture and separation process
Summary
Flue gas emissions from coal-fired power plants are a major source for the release of anthropogenic CO2 into the atmosphere. Mineral carbonation (MC), a process of converting CO2 to stable minerals (mineralization), is studied extensively to store CO2 Among these CO2 storage processes, mineral carbonation is an ideal approach to store CO2 on a geological time scale (Lackner, 2003). These CO2 capture technologies and storage processes have limitations for widespread practical use due to the requirement of separation of CO2 from flue gas, compression of CO2, and transportation of CO2 to a site where it can be safely stored or used for mineral carbonation process (Reddy et al, 2010). We show evidence suggesting that significant quantities of flue gas CO2 as well as SO2 and Hg can be directly captured (without separation) and mineralized by the fly ash particles under actual field conditions
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