Early Implementation of Large Scale Carbon Dioxide Removal Projects through the Cement Industry

Abstract:

The development of large-scale carbon dioxide reduction projects requires high purity CO₂and a reactive cation source. A project seeking to provide both of these requirements will likely face cost barriers with current carbon prices. The cement industry is a suitable early implementation site for such projects by virtue of the properties of its exhaust gases and those of waste concrete.

Cement plants are the second largest source of industrial CO₂ emissions, globally. It is also the second largest commodity after water, has no ready substitute and is literally the foundation of society. Finally, half of the CO₂ emissions originate from process reactions rather than fossil fuel combustion resulting in higher flue gas CO₂concentrations. These properties, with the co-benefits of oxygen combustion, create a favorable environment for spatially suitable projects.

Oxygen combustion involves substituting produced oxygen for air in a combustion reaction. The absence of gaseous N₂ necessitates the recirculation of exhaust gases to maintain kiln temperatures, which increase the CO₂ concentrations from 28% to 80% or more. Gas exit temperatures are also elevated (>300^oC) and can reach higher temperatures if the multi stage pre-heater towers, that recover heat, are re-designed in light of FGR.

A ready source of cations can be found in waste concrete, a by-product of construction and demolition activities. These wastes can be processed to remove cations and then reacted with atmospheric CO₂ to produce carbonate minerals. While not carbon negative, they represent a demonstration opportunity for binding atmospheric CO₂while producing a saleable product (precipitated calcium carbonate).

This paper will present experimental results on PCC production from waste concrete along with modeling results for oxygen combustion at cement facilities. The results will be presented with a view to mineral sequestration process design and implementation.