A Novel Approach to Mineral Carbonation: Enhancing Carbonation While Avoiding Mineral Pretreatment Process Cost

Abstract

Known fossil fuel reserves, especially coal, can support global energy demands for centuries to come, if the environmental problems associated with CO 2 emissions can be overcome. Unlike other CO 2 sequestration candidate technologies that propose long-term storage, mineral sequestration provides permanent disposal by forming geologically stable mineral carbonates. Carbonation of the widely occurring mineral olivine (e.g., forsterite, Mg 2 SiO 4 ) is a large-scale sequestration process candidate for regional implementation, which converts CO 2 into the environmentally benign mineral magnesite (MgCO 3 ). The primary goal is cost-competitive process development. As the process is exothermic, it inherently offers low-cost potential. Enhancing carbonation reactivity is key to economic viability. Recent studies at the U.S. DOE Albany Research Center have established that aqueous-solution carbonation using supercritical CO 2 is a promising process; even without olivine activation, 30-50% carbonation has been achieved in an hour. Mechanical activation (e.g., attrition) has accelerated the carbonation process to an industrial timescale (i.e., near completion in less than an hour), at reduced pressure and temperature. However, the activation cost is too high to be economical and lower cost pretreatment options are needed.We have discovered that robust silica-rich passivating layers form on the olivine surface during carbonation. As carbonation proceeds, these passivating layers thicken, fracture and eventually exfoliate, exposing fresh olivine surfaces during rapidly-stirred/circulating carbonation. We are exploring the mechanisms that govern carbonation reactivity and the impact that (i) modeling/controlling the slurry fluid-flow conditions, (ii) varying the aqueous ion species/size and concentration (e.g., Li , and (iii) incorporating select sonication offer to enhance exfoliation and carbonation. Thus far, we have succeeded in nearly doubling the extent of carbonation observed compared with the optimum procedure previously developed by the Albany Research Center. Aqueous carbonation reactivity was found to be a strong function of the ionic species present and their aqueous activities, as well as the slurry fluid flow conditions incorporated. High concentration sodium, potassium, and sodium/potassium bicarbonate aqueous solutions have been found to be the most effective solutions for enhancing aqueous olivine carbonation to date. Slurry-flow modeling using Fluent indicates that the slurryflow dynamics are a strong function of particle size and mass, suggesting that controlling these parameters may offer substantial potential to enhance carbonation.During the first project year we developed a new sonication exfoliation apparatus with a novel sealing system to carry out the sonication studies. We also initiated investigations to explore the potential that sonication may offer to enhance carbonation reactivity. During the second project year, we extended our investigations of the effects of sonication on the exten...

CO2 sequestration in ultramafic ores: impacts on the efficiency of nickel beneficiation

“…Once precipitated, MgCO 3 is a solid at room temperature (solubility in water, 0.0139 g per 100 ml at 25°C) and 0.64 M NaHCO 3 is soluble at room temperature (solubility in water, 10 g per 100 ml at 25 °C). 7,11 Drying the wet sample would add NaHCO 3 to the total inorganic carbon concentration, which could be misleading. Thus, to precisely quantify the MgCO 3 formed, the inorganic carbon for the dried liquid was subtracted from the inorganic carbon for the solid value.…”

“…4,5 Research efforts on mineral carbonation have focused on efficient mineral activation, determining the optimum conditions for mineral dissolution and precipitation, and enhancing reaction kinetics to maximize conversion. [6][7][8][9][10][11][12][13][14][15] Some of the most abundant minerals on Earth, serpentine (Mg 3 Si 2 O 5 (OH) 4 ) and olivine (MgSiO 4 ) require some form of activation or pretreatment to react. 8,[16][17][18] Pretreatment of serpentine to convert it to olivine involves heating to high temperatures (>610 °C), which is also energy intensive.…”

Mechanistic insights into the co-recovery of nickel and iron via integrated carbon mineralization of serpentinized peridotite by harnessing organic ligands

“…8(c)) from the surface of the olivine due to volumetric differences and resulting stresses between the olivine crystal and the layer depleted of Mg and O. 70,98,99 The exfoliation rate depends on the thickness of the passivation layer. The hydrothermal deposition of silica is known to contribute to the irregular surface morphology of the amorphous layer, leading to the formation of brittle silica.…”

“…The influence of chemical additives, including bicarbonate compounds like NaHCO 3 , and organic ligands such as Na 2 H 2 EDTAÁ2H 2 O, have been investigated for their individual effects on carbon mineralization efficiency in direct carbon mineralization studies. 2,8,22,28,30,31,48,[70][71][72][73][74] It has been reported that the addition of 2 M NaHCO 3 significantly enhances the carbon mineralization efficiency by approximately 50-60%. 8,28 Upon dissolution in the aqueous phase, NaHCO 3 dissociates to produce bicarbonate ions (R2).…”

Mineral Carbonation of CO2 in Mafic Plutonic Rocks, II—Laboratory Experiments on Early-Phase Supercritical CO2‒Brine‒Rock Interactions

“…Mg 2+ (aq)+ Ca 2+ (aq) + 2HCO 3 − (aq) = (Ca,Mg)CO 3 (s) + 2H + (aq) (6) Numerous laboratory experiments have been performed to study the reactivity of olivine, serpentine, pyroxene, amphibole and plagioclase mineral groups, and glass basalt lavas with CO 2 -enriched solutions [17][18][19][20]. Most of these experiments were conducted in batch conditions at controlled pressure, temperature and P CO 2 , using crushed rock.…”