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Accelerated carbonation of alkaline solid wastes is an attractive method for CO 2 capture and utilization. However, the evaluation criteria of CaCO 3 content in solid wastes and the way to interpret thermal analysis profiles were found to be quite different among the literature. In this investigation, an integrated thermal analyses for determining carbonation parameters in basic oxygen furnace slag (BOFS) were proposed based on thermogravimetric (TG), derivative thermogravimetric (DTG), and differential scanning calorimetry (DSC) analyses. A modified method of TG-DTG interpretation was proposed by considering the consecutive weight loss of sample with 200–900 °C because the decomposition of various hydrated compounds caused variances in estimates by using conventional methods of TG interpretation. Different quantities of reference CaCO 3 standards, carbonated BOFS samples and synthetic CaCO 3 /BOFS mixtures were prepared for evaluating the data quality of the modified TG-DTG interpretation, in terms of precision and accuracy. The quantitative results of the modified TG-DTG method were also validated by DSC analysis. In addition, to confirm the TG-DTG results, the evolved gas analysis was performed by mass spectrometer and Fourier transform infrared spectroscopy for detection of the gaseous compounds released during heating. Furthermore, the decomposition kinetics and thermodynamics of CaCO 3 in BOFS was evaluated using Arrhenius equation and Kissinger equation. The proposed integrated thermal analyses for determining CaCO 3 content in alkaline wastes was precise and accurate, thereby enabling to effectively assess the CO 2 capture capacity of alkaline wastes for mineral carbonation. [ABSTRACT FROM AUTHOR]

Highlights: [•] CO2 is captured effectively and efficiently by carbonation of BOFS with CRW in RPB. [•] Direct and indirect carbonation are performed with a capacity of 277g CO2/kg BOFS. [•] Material balance in the RPB was established with a recovery ratio from 90% to 110%. [•] The product of calcite formed and coated on BOFS was confirmed by SEM-EDX and XRD. [•] Kinetics model of carbonation of BOFS in CRW via RPB was developed by mass balance. [Copyright &y& Elsevier]

Abstract: CO2 capture by accelerated carbonation of basic oxygen furnace (BOF) slag in a slurry reactor containing metalworking wastewater was investigated in this study. Two types of metalworking wastewater provided by China Steel Corp. (Kaohsiung, Taiwan) were used: cold-rolling wastewater (CRW) and effluent from a metalworking wastewater treatment plant (EW). The effect of operational conditions including the type of metalworking wastewater, reaction time, liquid-to-solid (L/S) ratio, CO2 flow rate, and slurry volume on the CO2 fixation process was evaluated. The results indicated that BOF slag in CRW provided the highest degree of carbonation, 89.4%, with a reaction time of 120min, an L/S ratio of 20:1, and a CO2 flow rate of 1Lmin−1 at ambient temperature and pressure. In addition, the kinetics of the aqueous carbonation was evaluated using the surface coverage model. This study provided a promising alternative for CO2 capture from the flue gas in steelmaking process by reusing the metalworking wastewater and steelmaking slag as feedstock, which could reduce the use of water resources as well as the total cost. Compared with other studies in the literature, this study showed a higher carbonation conversion with less consumption of energy and resources. [Copyright &y& Elsevier]

Abstract: Carbon dioxide (CO2) sequestration using the accelerated carbonation of basic oxygen furnace (BOF) slag in a high-gravity rotating packed bed (RPB) under various operational conditions was investigated. The effects of reaction time, reaction temperature, rotation speed and slurry flow rate on the CO2 sequestration process were evaluated. The samples of reacted slurry were analyzed quantitatively using thermogravimetric analysis (TGA) and atomic absorption spectrometry (AAS) and qualitatively using X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX), and transmission electron microscopy (TEM). The sequestration experiments were performed at a liquid-to-solid ratio of 20:1 with a flow rate of 2.5Lmin−1 of a pure CO2 stream under atmospheric temperature and pressure. The results show that a maximum conversion of BOF slag was 93.5% at a reaction time of 30min and a rotation speed of 750rpm at 65°C. The experimental data were utilized to determine the rate-limiting mechanism based on the shrinking core model (SCM), which was validated by the observations of SEM and TEM. Accelerated carbonation in a RPB was confirmed to be a viable method due to its higher mass-transfer rate. [Copyright &y& Elsevier]

Abstract: CO2 sequestration by the aqueous carbonation of steel-making slag under various operational conditions was investigated in this study. The effects of the operational conditions, including type of steel-making slag, reaction time, reaction temperature, and CO2 flow rate, on the performance of the carbonation process were evaluated. The results indicated that the BOF slag had the highest carbonation conversion, approximately 72%, at a reaction time of 1h, an operating pressure of 101kPa and a temperature of 60°C due to its higher BET surface area of BOF slag compared to UF, FA, and BHC slags. The major factors affecting the carbonation conversion are reaction time and temperature. The reaction kinetics of the carbonation conversion can be expressed by the shrinking-core model. The measurements of the carbonated material by the SEM and XRD instruments provide evidence indicating the suitability of using the shrinking-core model in this investigation. Comparison of the results with other studies suggests that aqueous carbonation by slurry reactor is viable due to its higher mass transfer rate. [Copyright &y& Elsevier]

Basic oxygen furnace slag (BOFS) exhibits highly alkaline properties due to its high calcium content, which is beneficial to carbonation reaction. In this study, accelerated carbonation of BOFS was evaluated under different reaction times, temperatures, and liquid-to-solid (L/S) ratios in a slurry reactor. CO 2 mass balance within the slurry reactor was carried out to validate the technical feasibility of fixing gaseous CO 2 into solid precipitates. After that, a multiple model approach, i.e., theoretical kinetics and empirical surface model, for carbonation reaction was presented to determine the maximal carbonation conversion of BOFS in a slurry reactor. On one hand, the reaction kinetics of BOFS carbonation was evaluated by the shrinking core model (SCM). Calcite (CaCO 3 ) was identified as a reaction product through the scanning electronic microscopy and X-ray diffraction analyses, which provided the rationale of applying the SCM in this study. The rate-limiting step of carbonation was found to be ash-diffusion controlled, and the effective diffusivity for carbonation of BOFS in a slurry reactor were determined accordingly. On the other hand, the carbonation conversion of BOFS was predicted by the response surface methodology (RSM) via a nonlinear mathematical programming. According to the experimental data, the highest carbonation conversion of BOFS achieved was 57% under an L/S ratio of 20 mL g −1 , a CO 2 flow rate of 0.1 L min −1 , and a pressure of 101.3 kPa at 50 °C for 120 min. Furthermore, the applications and limitations of SCM and RSM were examined and exemplified by the carbonation of steelmaking slags. [ABSTRACT FROM AUTHOR]

Highlights: [•] Kinetics of BOFS carbonation reaction was well expressed by surface coverage model. [•] The model was validated by SEM images which indicate the BOFS was covered by CaCO3. [•] Carbonation conversion of BOFS with CRW was higher than that in pure-water system. [•] Reaction rate in RPB was greater than that in both autoclave and slurry reactors. [•] The maximum conversion was determined by kinetic model and response surface method. [ABSTRACT FROM AUTHOR]

Both basic oxygen furnace (BOF) slag and cold-rolling wastewater (CRW) exhibiting highly alkaline characteristics require stabilization and neutralization prior to utilization and/or final disposal. Using CO2 from flue gases as the stabilizing and neutralizing agents could also diminish CO2 emissions. In this investigation, ex situ hot stove gas containing 30 vol% CO2 in the steelmaking process was captured by accelerated carbonation of BOF slag coupled with CRW in a rotating packed bed (RPB). The developed RPB process exhibits superior results, with significant CO2 removal efficiency (η) of 96-99% in flue gas achieved within a short reaction time of 1 min at 25 °C and 1 atm. Calcite (CaCO3) was identified as the main product according to XRD and SEM-XEDS observations. In addition, the elimination of lime and Ca(OH)2 in the BOF slag during carbonation is beneficial to its further use as construction material. Consequently, the developed RPB process could capture the CO2 from the flue gas, neutralize the CRW, and demonstrate the utilization potential for BOF slag. It was also concluded that carbonation of BOF slag coupled with CRW in an RPB is a viable method for CO2 capture due to its higher mass transfer rate and CO2 removal efficiency in a short reaction time. [ABSTRACT FROM AUTHOR]