Factors Influencing CO2 and Energy Penalties of CO2 Mineralization Processes

Chemical Batteries with CO2

Efforts to obtain raw materials from CO2 by catalytic reduction as a means of combating greenhouse gas emissions are pushing the boundaries of the chemical industry. The dimensions of modern energy regimes, on the one hand, and the necessary transport and trade of globally produced renewable energy, on the other, will require the use of chemical batteries in conjunction with the local production of renewable electricity. The synthesis of methanol is an important option for chemical batteries and will, for that reason, be described here in detail. It is also shown that the necessary, robust, and fundamental understanding of processes and the material science of catalysts for the hydrogenation of CO2 does not yet exist.

Utilization of low-calcium fly ash via direct aqueous carbonation with a low-energy input: Determination of carbonation reaction and evaluation of the potential for CO2 sequestration and utilization

Environmental impacts from coal-fired power generation that produces large amounts of CO₂ and fly ash are of great interest. To reduce negative environmental impacts, fly ash utilization was investigated via a direct aqueous carbonation with a low-energy input in which the alkali calcium content in the fly ash reacted with CO₂ to form carbonate. Raw fly ash was characterized to understand the potential for direct aqueous carbonation of fly ash. The performance of the fly ash as a calcium source for direct aqueous carbonation at atmospheric pressure was investigated for different solid-liquid ratios and introduced CO₂ concentrations. Variations in fly ash elemental composition, reaction solution pH, CO₂ concentration in the reactor outlet, CO₂ uptake efficiency, CaCO₃ content and degree of carbonation were used to illustrate this process reaction. The maximum CO₂ uptake efficiency was ~0.016 g-CO₂/g-fly ash. This value was compared with previous studies, and the CO₂ uptake efficiency was comparable despite the use of a low-energy input method, i.e., direct aqueous carbonation with atmospheric pressure and unconcentrated CO₂. The calculated maximum degree of carbonation was 31.0%, which corresponds to 0.0063 g-CO₂/g-fly ash. Carbonated product characterization confirmed the carbonation reaction mechanism and safety for further utilization. A comparison of CO₂ uptake efficiency in this work with previous work, and considering the energy input and reactive species content, is provided. An assessment of the CO₂ reduction potential is provided.

CO2 Utilization via Direct Aqueous Carbonation of Synthesized Concrete Fines under Atmospheric Pressure

Mineral carbonation using alkaline wastes is an attractive approach to CO₂ utilization. Owing to the difference between waste CO₂ and feedstock CO₂, developing CO₂ utilization technologies without CO₂ purification and pressurization is a promising concept. This study investigated a potential method for CO₂ utilization via direct aqueous carbonation of synthesized concrete fines under atmospheric pressure and low CO₂ concentration. The carbonation reaction with different solid-liquid ratios and different concentrations of introduced CO₂ was examined in detail. Under basic conditions, a CO₂ uptake of 0.19 g-CO₂/g-concrete fines demonstrated that direct aqueous carbonation of concrete fines under atmospheric pressure and low CO₂ concentration is effective. The CaCO₃ concentration, degree of carbonation, and reaction mechanism were clarified. Furthermore, characterization of the carbonated products was used to evaluate ways of utilizing the carbonated products.