Flue gas CO₂ mineralization using thermally activated serpentine: from single- to double-step carbonation

Abstract

Carbon dioxide capture and utilization by mineralization seeks to combine greenhouse gas emission control with the production of value-added materials in the form of solid carbonates. This experimental work demonstrates that the world's most abundant mineralization precursor, the magnesium (Mg) silicate serpentine, in its thermally activated, partially dehydroxylated form can be carbonated without the use of chemical additives at process temperatures (T) below 90 °C and CO2 partial pressures (pCO2) below 1 bar. A first series of single-step batch experiments was performed varying the temperature and slurry density to systematically assess the precipitation regime of the relevant Mg-carbonates and the fate of silicon (Si) species in solution. The results suggested that the reaction progress was hindered by a passivating layer of re-precipitated silica or quartz, as well as by equilibrium limitations. Concurrent grinding proved effective in tackling the former problem. A double-step strategy proved successful in addressing the latter problem by controlling the pH of the solution. This is achieved by continuously removing the Mg from the dissolution reactor and letting it precipitate at a higher T and a lower pCO2 in a separate reactor, thus yielding a combined T-pCO2-swing-the working principle of a new flue gas mineralization route is presented herein. Simulations and experiments of the different individual steps of the process are reported, in order to make an assessment of its feasibility.

Effect of pCO 2 on direct flue gas mineral carbonation at pilot scale

“…This route has the advantage to avoid a capture step which clearly simplifies the process scheme. In this way, different studies focused on using a diluted CO 2 stream, similar at some industrial flue gas (Pasquier et al, 2014a;Werner et al, 2014). Results showed that reaction mechanism, kinetics where similar as observed for pure CO 2 treatments and led to promising results Pasquier et al, 2014b).…”

Serpentinites: Mineral Structure, Properties and Technological Applications

“…[53][54][55][56][57] Direct carbonation involving serpentinite and forsterite rocks has been proposed. [58][59][60][61] In this case, the CO 2 is dissolved in solution forming carbonic acid. This causes a pH reduction in the medium, allowing the dissolution of the magnesium silicate and the subsequent carbonation.…”

Factors Influencing CO2 and Energy Penalties of CO2 Mineralization Processes

“…For the purpose of this work, we have chosen the best possible conversion at 50 °C and 20 wt % slurry concentrations in the single‐step ball‐mill reactor as S1. The researchers have also reported that a higher conversion of up to 88.8 % is possible at 90 °C and 1 wt % slurry conversion and we perform the analysis of the same as S4. It must be mentioned here that single‐step reaction without ball milling was also presented at the same conditions as that of S1; however, it was observed that the conversion was lower, at only about 15 % compared with 30 % for S1.…”

“…In addition to these, there are several other publications in the area of CO 2 mineralization and these can be broadly grouped based on the respective research group. Briefly, these research groups are the National Energy Technology Laboratory (NETL), Comans et al., Zevenhoven et al., Jie Bu et al., Shell Global Solutions, The Netherlands & collaborators, Maroto‐Valer et al., and others . Although most of this research focussed on inorganic acids, there are others who used organic acids.…”

“…Hence, we seek to understand further the DAC processes that are described in literature by NETL . More recently, the T‐P swing double step carbonation process, which avoids high temperature and pressure and utilises pH swing is being developed to avoid the large CO 2 and energy penalties associated with high‐pressure carbonation. In view of this, we present an evaluation of the T‐P swing process in addition to the DAC process so that we can compare a pioneering CO 2 mineralization process with an upcoming process to better understand the variables that impact CO 2 and energy penalties of the CO 2 mineralization process.…”