Carbonation of high-calcium fly ashes and its potential for carbon dioxide removal in coal fired power plants

Abstract

Carbonation of industrial wastes rich in earth-alkali oxides is found to have a significant potential for CO2 sequestration. This process opens new perspectives not only for carbon dioxide mitigation, but also for the valorization and new applications of industrial waste materials from coal-burning power 2 plants. In this study, mineral carbonation of high-calcium fly ash is investigated under dry and moist conditions in a continuous flow reactor during up to 2 hours, at temperatures ranging from 160 to 290 ºC and CO2 pressures between 1 and 6 bar. A comprehensive charaterization of treated and untreated samples was carried out before and after carbonation using X-ray diffraction, X-ray fluorescence spectroscopy, thermogravimetric analysis, infrared spectroscopy and scanning electron microscopy. The maximum sequestration capacity achieved was 117.7 g CO2/kg fly ash (48.14 % carbonation efficiency) under dry conditions. Results showed that increasing the pressure and temperature enhances the process of carbonation, as well as the presence of moderate amounts of water vapor in the CO2 gas flow. Newly formed carbonates were always present in the treated samples. This study shows that about 21% of all CO2 emissions of a coal-burning power plant could potentially be sequestered as carbonates.

The Mineral Carbonation Process of High Calcium Fly Ash under Elevated Carbon Dioxide Pressure and Temperature

“…Therefore, in laboratory conditions, the mineral carbonation process is carried out under increased pressure and also at a higher temperature. It is the reaction between calcium oxide and carbon dioxide which results in carbonates, which are raw material for use in industry, as well as for further physical and chemical treatment [12]. There are two types of mineral carbonation: There is a possibility of previous treatment of the examined fly ash (grinding, cleaning) before the mineral carbonation process, as well as the use of catalysts changing e.g.…”

Carbonatación mineral natural y acelerada mediante cenizas volantes de coque de petróleo: Evaluación potencial de su pre-tratamiento físico

“…La literatura plantea que a medida que se aumenta la relación S/L, el porcentaje de captura de CO 2 debe ir aumentando [5,[10][11][12]. Este planteamiento se corrobora en los resultados, lo cual indica que la variable S/L no puede analizarse separadamente de la temperatura.…”

“…La carbonatación depende de características físicas del material como la distribución del tamaño de partícula, área superficial específica y porosidad. Además depende de variables de operación como la temperatura, presión, relación sólido-líquido, concentración de CO 2 y agitación del medio [4][5][6][7][8][9][10][11][12]. Varios investigadores reportan que la reacción de carbonatación sigue un modelo cinético de primer orden [7,[10][11][12].…”

Calcination-free production of calcium hydroxide at sub-boiling temperatures

“…Of the latter, only 58% are benecially utilized. 21 And, global waste reservoirs host well over a billion tons of slag, 16 and tens of billions of tons of y ash, [22][23][24] based on broad estimates. Underutilized quantities of alkaline wastes, i.e., y ashes and slags, are routinely disposed in landlls, which not only implies a waste disposal cost ("tipping fees", NB: the average tipping fee in the U.S. is on the order of $50 per t), 25 but can also result in environmental damage.…”