Acceleration of Gas-Solid CO2 Mineralization with Low Energy Consumption

Abstract

Above ground conversion of CO2 into stable minerals (‘CO2 mineralization’) by reaction with certain naturally available rocks offers a strategically attractive alternative to conditioning, transport, underground storage, and monitoring of CO2. To make CO2 mineralization a viable technology for high concentration point sources such as industry and direct air capture, the mineralization rate needs to be accelerated to reduce reactor size. Grinding is well known to accelerate mineralization rates, but if overdone can lead to large CO2 emissions and/or high unit costs of CO2 removal due to excessive energy consumption. We examine the acceleration and energy burden of batch grinding followed by CO2 mineralization and continuously grinding rocks while CO2 mineralization occurs. We find that the net CO2 removal efficiency and cost of CO2 mineralization using continuous grinding is strongly dependent on the rock used and the CO2 intensity of energy. In general, more reactive minerals are better suited to continuous grinding than less reactive minerals as they spend less time in the grinder and thus use less energy. Batch grinding performance is much less sensitive to rock type and electricity source; typical energy costs are <$10/t-CO2 for batch grinding.

Keywords: CCS, CDR, negative emissions, energy efficiency, comminution