Synergic CO2 mineralization of coal fly ash and carbide slag and potential utilization
To confirm the technical feasibility of CO2 mineralization for multi-source solid waste treatment,the typical industrial solid waste,coal fly ash and calcium carbide slag in northern Shaanxi were selected to explore their CO2 mineralization performance and physicochemical properties before and after reaction,as well as their interaction during CO2 mineralization.The results show that the CO2 removal efficiency(50%)and CO2 sequestration capacity 5.0 g/kg)of coal fly ash were very limited.Compared with coal fly ash,calcium carbide slag showed a higher CO2 removal efficiency(90%)and CO2 sequestration capacity(340 g/kg).However,in the process of CO2 mineralization,the CO2 mineralization reaction on the surface of calcium carbide slag particles was very intense,resulting in the rapidly generated CaCO3 coating the unreacted calcium carbide slag particles,thus reducing the amount of CO2 sequestration capacity.When coal fly ash and calcium carbide slag was mixed for the synergic CO2 mineralization,coal fly ash particles not only provided the precipitation crystallization site for calcite,but also dispersed the calcium carbide slag particles,preventing the newly formed calcite from covering the unreacted calcium carbide slag particles,which promoted the reaction of calcium carbide slag,and increased the CO2 sequestration capacity of coal fly ash and calcium carbide slag mixture.The fly ash produced by coal mining is prepared into slurry with calcium carbide slag and mine water to mineralize and seal CO2 in the flue gas.After mineralization,the slurry is backfilled into the mine through pipes,which not only helps to reduce CO2 emission,but also reduces the agglomeration of particles in the slurry.It is of great significance to the utilization of fly ash resources,the utilization of coal goaf space,the utilization of mine water and the reduction of carbon emission of power plants under the coal-power joint operation mode.
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