Modeling mafic carbonation efficiency using mafic rock chemistries from Nevada, USA

摘要

Mineral carbonation is one of the many ways that are being actively investigated to sequester point-source carbon dioxide emissions. However, relations between reaction conditions, variations in reactant mineral composition, and carbon sequestration potential are poorly understood. In this study we used reaction path geochemical modeling to evaluate carbon sequestration potential during ex-situ mineral carbonation of ten mafic rock samples from Nevada, USA. Models were run using arbitrary dissolution kinetics at temperatures between 0 and 200 degrees C. A subset of models were run using true dissolution kinetics. In the models, carbon is sequestered in 5 mineral phases: magnesite, siderite, dolomite, calcite, and dawsonite, with magnesite and dolomite the most abundant. Dawsonite sequesters carbon at T 150 degrees C in most of the arbitrary kinetics models but is not a significant carbon sink in the models using true dissolution kinetics. The arbitrary kinetics models resulted in 4.5-13 mol of carbon sequestered per kg of reacted mafic rock. True kinetics models only resulted in 1-2 mol of carbon sequestered, but the models only reacted 12.5 to 15 wt percent of the mafic rock inputs. Product minerals using the arbitrary kinetics model have volumes 150%-470% larger than the reactant volumes, whereas using true kinetics the models have a modest increase. Modeling presented herein confirms several areas of Nevada as having potential for mafic rock carbonation, some of which are located near existing coal- and natural gas-fired power plants. As shown in this study, reaction path modeling is a vital and inexpensive tool to help optimize costs and reaction conditions for ex-situ mafic rock carbonation projects.