Influence of process parameters on carbonation rate and conversion of steelmaking slags – Introduction of the ‘carbonation weathering rate’

Abstract

Alkaline industrial wastes are considered potential resources for the mitigation of CO2 emissions by simultaneously capturing and sequestering CO2 through mineralization. Mineralization safely and permanently stores CO2 through its reaction with alkaline earth metals. These elements are found in a variety of abundantly available industrial wastes that have high reactivity with CO2, and that are generated close to the emission point‐sources. Among all suitable industrial wastes, steelmaking slag has been deemed the most promising given its high CO2 uptake potential. In this paper, we review recent publications related to the influence of process parameters on the carbonation rate and conversion extent of steelmaking slags, comparing and analyzing them in order to define the present state of the art. Furthermore, the maximum conversions resulting from different studies are directly compared using a new index, the Carbonation Weathering Rate (CWR), which normalizes the results based on particle size and reaction duration. To date, the carbonation of Basic Oxygen Furnace steelmaking slag, under mild conditions, presents both the highest carbonation conversion and CWR, with values equal to 93.5% and 0.62 μm/min, respectively. © 2016 Society of Chemical Industry and John Wiley & Sons, Ltd

How Characterization of Particle Size Distribution Pre- and Post-Reaction Provides Mechanistic Insights into Mineral Carbonation

“…Table 3 summarizes the methods used by these researchers to determine particle size and/or PSD, and how these data were used in the cited work, especially if significant mechanistic insight was obtained. The works reviewed in Table 3 are the same as the works that were reviewed by Georgakopoulos et al [10] in a study that introduced and applied the carbonation weathering rate; for more on this topic, see Section 4.1. It is important to note that, to calculate the CWR, at least the volume-based average particle size must be known.…”

“…Table 3. Summary of particle size determination methods and utilization from different carbonation studies reviewed by Georgakopoulos et al [10].…”

“…As discussed by Georgakopolus et al [10] the absence of precise particle size data makes the calculation of the CWR less accurate. It is also important to note that it is not possible to know with certainty if a slag sample classified as <44 µm is actually finer than one classified as <88 µm.…”

“…Mineral carbonation is a solid-state-diffusion-limited process under most conditions, so the different particle sizes affect the carbonation rate and maximal achievable conversion. In order to make direct comparisons among the results obtained from different studies, the carbonation weathering rate (CWR) was conceptualized [10]. The rate is expressed in units of µm·min -1 , and represents the weathering rate of the particle radius, from the original outer radius of the slag particle to the final radius of the unreacted core of the carbonated slag particle.…”

Effect of Solidification and Cooling Methods on the Efficacy of Slag as a Feedstock for CO₂ Mineralization

“…The large variability in these characteristics introduces significant noise into experimental data; consequently, logically consistent trends about the effectiveness of operating parameters such as liquid-to-solid ratio, temperature, CO 2 partial pressure, and reaction time remain elusive. 13) Further, there is a failure to recognize that these traits are in large part controlled by the slag solidification and cooling processes employed at ISM facilities. This paper posits that slag-based CO 2 mineralization efficacy can be improved by control of the solidification-and coolingdependent mineralogy, structure, and micromorphology of slags.…”