Investigation of the potential of coal combustion fly ash for mineral sequestration of CO2 by accelerated carbonation

Mineral carbonation of alkaline waste materials is being studied extensively for its potential as a way of reducing the increased level of CO2 in the atmosphere. Carbonation converts CO2 into minerals which are stable over geological time scales. This process occurs naturally but slowly, and needs to be accelerated to offset the present rate of emissions from power plants and other emission sources. The present study attempts to identify the potential of coal fly ash as a source for carbon storage (sequestration) through ex-situ accelerated mineral carbonation. In the study, two operational parameters that could affect the reaction process were tested to investigate their effect on mineralization. Coal fly ash was mixed with water to different water-to-solid ratios and samples were carbonated in a pressure vessel at different initial CO2 pressures. Temperature was kept constant at 40 °C. According to the results, one ton of Hazelwood fly ash could sequester 7.66 kg of CO2. The pressure of CO2 inside the vessel has an effect on the rate of CO2 uptake and the water-to-solid ratio affects the weight gain after the carbonation of fly ash. The results confirm the possibility of the manipulation of process parameters in enhancing the carbonation reaction.

► Mineral sequestration CO2 by of coal fly ash is a slow process under ambient conditions.
► It can be accelerated by manipulating the process parameters inside a reactor.
► Initial CO2 pressure and water to solid mixing ratio inside the reactor are two of those operational parameters.
►  According to the test results higher CO2 initial pressure gives higher on rates of CO2 sequestration.
► Water to fly ash mixing ratio effect on amount of CO2 sequestered into fly ash.