Accelerated Carbonation of Steel Slags Using CO2 Diluted Sources: CO2 Uptakes and Energy Requirements

Renato Baciocchi,Daniela Zingaretti,Raffaella Pomi,Alessio Stramazzo,Giulia Costa,Alessandra Polettini

doi:10.3389/fenrg.2015.00056

Renato Baciocchi, Daniela Zingaretti + Show 4 more

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https://doi.org/10.3389/fenrg.2015.00056

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Abstract

This work presents the results of carbonation experiments performed on Basic Oxygen Furnace (BOF) steel slag samples employing gas mixtures containing 40 and 10% CO2 vol. simulating the gaseous effluents of gasification and combustion processes respectively, as well as 100% CO2 for comparison purposes. Two routes were tested, the slurry phase (L/S=5 l/kg, T=100 °C and Ptot=10 bar) and the thin film (L/S =0.3-0.4 l/kg, T=50 °C and Ptot=7-10 bar) routes. For each one, the CO2 uptake achieved as a function of the reaction time was analyzed and on this basis the energy requirements associated to each carbonation route and gas mixture composition were estimated considering to store the CO2 emissions of a medium size natural gas fired power plant (20 MW). For the slurry phase route, maximum CO2 uptakes ranged from around 8% at 10% CO2, to 21.1% (BOF-a) and 29.2% (BOF-b) at 40% CO2 and 32.5% (BOF-a) and 40.3% (BOF-b) at 100% CO2. For the thin film route, maximum uptakes of 13% (BOF-c) and 19.5% (BOF-d) at 40% CO2, and 17.8% (BOF-c) and 20.2% (BOF-d) at 100% were attained. The energy requirements of the two analyzed process routes appeared to depend chiefly on the CO2 uptake of the slag. For both process route, the minimum overall energy requirements were found for the tests with 40% CO2 flows (i.e. 1400-1600 MJ/t CO2 for the slurry phase and 2220-2550 MJ/t CO2 for the thin film route).

Highlights

Accelerated carbonation of alkaline earth metal silicate ores has been proposed as a method for ex situ carbon dioxide storage in the early 90s (Seifritz, 1990; Lackner et al, 1995)
Since the aim of the present paper is to provide an assessment of the energetic profile of CO2 sequestration through mineral carbonation of steel manufacturing residues applying both the slurry-phase and the thin-film route, the energy demand of the various process units as affected by the operating conditions and the intrinsic reactivity of the material toward CO2 was estimated
The CO2 uptakes measured after 24 h carbonation applying the slurry-phase route were: ≈8% at 10% CO2 for both types of slag, 21.1% (BOF-a) and 29.2% (BOF-b) at 40% CO2, and 32.5% (BOF-a) and 40.3% (BOF-b) at 100% CO2; the corresponding values resulting for the thin-film route were: 12.9% (BOF-c) and 19.5% (BOF-d) at 40% CO2, and 17.8% (BOF-c)

Summary

Introduction

Accelerated carbonation of alkaline earth metal silicate ores has been proposed as a method for ex situ carbon dioxide storage in the early 90s (Seifritz, 1990; Lackner et al, 1995). Different types of process routes, i.e., gas-solid or aqueous, each performed in direct or indirect mode, have been tested (see e.g., Sipilä et al, 2008; Baciocchi et al, 2014). It should be noted that the operating conditions that have proven effective to promote the carbonation kinetics of the tested minerals, and obtain high reaction yields in technically feasible operating times (

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