Definition and Exploration of the Integrated CO2 Mineralization Technological cycle

This paper is part of a multi-disciplinary research program on development and application of an integrated CO2 mineralization (ICM) framework for development of carbon mineralization as a CO2 mitigation solution. ICM is viewed as a three concentric layer system: technological, industrial integration, and decision-making. The search for viable ICM solutions in a given societal and economic context, which could be posed as an inverse design problem, begins with the identification and characterization of every system component. As an early writing on the development and applicability of the proposed ICM framework, this contribution focuses on ICM's inner technological layer. Several technological pathways, each one defined as a set of processing and transformation steps that connect a feedstock to a specific marketable product, can coexist within this layer. The paper addresses the characterization of one such technological pathway, whose cycle is divided into three successive blocks: feedstock, carbonation and valorization. The proposed concepts are illustrated through the valorization of ferronickel slag from New Caledonia as supplementary cementitious material or cement constituent, a case study that targets the production of “greener” construction materials. The data presented in the paper confirm the feasibility of characterizing the chosen ICM technological pathway, giving credit to the proposition that ICM can be approached as an inverse design problem. While exemplifying the significance of the characterization work necessary for one particular ICM technological pathway, the paper argues that development of ICM requires working on a scale considerably larger than that of standard mineral carbonation process research. Indeed, where grams of carbonated products are sufficient to investigate mineral carbonation processes, kilograms are mandatory to test and validate the use performance of final marketable products. Without precluding the merits of seeking innovative solutions, the authors argue that unit operations and transformation processes whose validity is proven at an industrial scale should be favored for timely development of viable ICM solutions

Approche thermodynamique du procédé de lixiviation pour la récupération des métaux - Cas de la chalcopyrite

Dans le domaine de l’hydrométallurgie, le développement d’un procédé de lixiviation du minerai de chalcopyrite, CuFeS2, revêt une importance industrielle majeure. Comme pour d’autres minerais, son efficacité est limitée par la formation de couches de surface solides, qui ralentissent ou bloquent la dissolution. De multiples études ont été menées pour identifier la nature des couches passivantes et les conditions opératoires qui favorisent leur formation, mais de nombreuses inconnues et contradictions persistent. Dans le but de voir s’il existe une fenêtre opératoire industriellement exploitable pour traiter la chalcopyrite en voie aqueuse, une méthodologie sur la modélisation thermodynamique de la lixiviation est en cours de développement. Cet article en présente les articulations principales. Le travail réalisé a permis d’identifier quelques points clés, dont certains sont discutés dans le texte. En croisant deux outils de simulation d’équilibres thermodynamiques, PhreeqC et FactSage, qui utilisent des approches de calcul et des bases de données thermodynamiques différentes, l’analyse fait apparaître une divergence importante sur la prédiction d’une des frontières phase aqueuse/phase solide dans le système le plus complet : Cu-Fe-S-H2O, système critique pour modéliser la lixiviation de la chalcopyrite. Pour mieux comprendre cet écart, des simulations de complexité croissante ont été mises en oeuvre : les sous-systèmes constitutifs ont été examinés un par un par confrontation à des données de la littérature. L’étude du système Fe-S-H2O a notamment révélé des espèces prédominantes en solution propres à chaque base de données. En particulier, aucune des configurations de calcul n’a permis de reproduire un jeu de données expérimentales portant sur la solubilité de la goethite, FeOOH, dans un solvant eau-acide sulfurique. Afin de déterminer les modifications éventuelles à apporter aux modèles ou bases utilisés, des mesures expérimentales complémentaires s’avèrent indispensable

Carboscories : carbonatation minérale en Nouvelle-Calédonie : rapport bibliographique. Tome Nickel et technologie (rapport scientifique 2015)

La carbonatation minérale ex-situ, accélérant un processus naturel thermodynamiquement favorable, est considérée comme une voie possible pour le piégeage du CO2 émis par les installations industrielles. La situation insulaire de la Nouvelle-Calédonie, avec une proximité des flux de CO2 émis et des ressources carbonatables, est favorable au développement d’une filière. La carbonatation des résidus de pyrométallurgie, largement étudiée dans le monde au stade du laboratoire (notamment par plusieurs équipes d’universités américaines prestigieuses), n’a pas encore pu être menée à un stade pilote/pré-industriel, du fait notamment de verrous liés au procédé (faibles rendements de carbonatation liés à la passivation des surfaces réactives ; conditions opératoires contraignantes). Le projet CARBOSCORIES s’inscrit dans la continuité du projet ANR/CARMEX (2009-2012) qui a permis des avancées significatives sur la carbonatation minérale ex-situ, avec notamment le développement, au Laboratoire de Génie Chimique de Toulouse (LGC), d’un procédé en mode « batch » couplant attrition et réaction de carbonatation (thèse B. Bonfils, 2012). L’objectif de CARBOSCORIES concerne le transfert des acquis du nouveau procédé CARMEX aux scories de la SLN déjà caractérisées chimiquement et minéralogiquement dans le projet CARMEX et l’évaluation des potentialités de carbonatation des scories de KNS, seconde source de résidus industriels potentiellement carbonatables. En effet, il existe une différence majeure entre les scories issues des deux procédés. Les scories SLN sont finement fractionnées (<5 mm) grâce à un passage de la scorie en fusion à la sortie du four devant un rideau d’eau de mer (trempe), alors que les scories KNS sont grossièrement concassées après refroidissement (plus lent) à la sortie du four. Les processus de cristallisation s’en trouvent modifiés, ce qui peut influer sur les potentialités de carbonatation. Il est donc proposé dans le cadre du projet CARBOSCORIES de : - de tester la démarche ‘CARMEX’ de carbonatation, valider la bonne réactivité des scories vis-à-vis du CO2 et d’étudier en détail les sousproduits de réaction, finement divisés ; - de réaliser des calculs bilanciels massiques et énergétiques de l’intégration du procédé aux installations industrielles à partir des paramètres opératoires principaux des sites, afin de quantifier l’efficacité de l’unité de carbonatation dans les deux environnements industriels ; - de proposer aux industriels des perspectives opérationnelles en fonction du comportement à la carbonatation des deux types de scories. Des recommandations de préparation industrielle seront proposées le cas échéan

Mécanismes et verrous de la carbonatation minérale du CO2 en voie aqueuse

La carbonatation minérale est une technique alternative de capture et stockage du CO2 anthropique. L'abondance des matériaux carbonatables sur terre en fait une solution à fort potentiel. En particulier, la carbonatation directe en voie aqueuse a été présentée dans la littérature comme la voie la plus intéressante d'un point de vue énergétique pour la carbonatation minérale ex-situ, à la condition que les cinétiques naturellement lentes de dissolution des silicates magnésiens en phase aqueuse puissent être accélérées de plusieurs ordres de grandeur. Cette thèse étudie en détail les verrous et mécanismes de cette réaction en présence d'additifs organiques tels que l'oxalate, connus pour leur capacité à accélérer la dissolution des silicates magnésiens. Dans un premier temps, la carbonatation en voie aqueuse sans additif d'une olivine modèle est étudiée de manière à mettre en évidence la nature des phénomènes limitants. Ensuite le travail se concentre sur l'étude du rôle de l'additif oxalate à travers des essais spécifiques et une analyse fine de la phase solide. Il est démontré que pour différentes concentrations de suspension et sous 20 bar de CO2, cet additif conduit à la formation de complexes aqueux stables du magnésium avec l'oxalate et à la précipitation de MgC2O4,2H2O (glushinskite), qui empêchent toute précipitation quantitative de magnésite. La simulation géochimique complète du système a été réalisée et a permis d'expliquer les résultats des essais par un mécanisme de dissolution à grain rétrécissant. L'extension de l'étude à un autre silicate (harzburgite) et à d'autres ligands organiques accélérateurs de la dissolution des silicates tels que le citrate et l'EDTA n'a pas non plus permis d'obtenir la formation quantitative de carbonate, à cause d'une forte complexation en phase aqueuse du Mg extrait du minerai. Ces travaux remettent en doute la perspective de développement d'un procédé industrialisable de minéralisation du CO2 en présence d'additifs organiques.Mineral carbonation is an interesting option for mitigation of anthropogenic CO2 emissions. Direct aqueous mineral carbonation has been presented by many as a promising strategy for ex-situ mineral carbonation, on the basis that organic additives such as oxalate increase the rate and extent of dissolution of magnesium silicates several folds. This thesis discusses and extends the current understanding of this process through geochemical modelling and detailed solid characterization. First, mineral carbonation is investigated in water alone, without additives, in order to understand and quantify the actual limitations of the process with specific magnesium silicate ores. Dissolution kinetics being critical with this process, the role of disodium oxalate as a dissolution accelerating agent is thoroughly examined with olivine, through dedicated experiments and comprehensive analysis of both solid and liquid phases. Under 20 bar of CO2, and irrespective of the conditions used, it is found that the formation of strong oxalate-magnesium complexes in solution and precipitation of MgC2O4,2H2O (glushinskite) impede any chance of precipitating significant amounts of magnesium carbonate. Geochemical modelling permits successful simulation of the dissolution kinetics of magnesium silicate using a shrinking particle model. Other promising ligands from a dissolution perspective, namely citrate and EDTA, were also investigated. Contrary to oxalate, these do not form any solid by-products with magnesium, and yet they do not produce better carbonation results. The results and findings from this work cast strong doubts about the possibility of developing a viable direct aqueous mineral carbonation process using organic salts.TOULOUSE-INP (315552154) / SudocSudocFranceF

Ex-situ mineral carbonation: resources, process and environmental assessment (Carmex project)

This article presents the main results of the Carmex project (2009-2012), whose purpose was to review the feasibility of ex-situ mineral carbonation in terms of resource availability, performance of the aqueous mineral carbonation process and life cycle analysis criteria. This collaborative project looked at a wide range of generic issues about this CO2 mitigation option, with particular views on assessing its potential in the context of New-Caledonia. Indeed, insularity and local abundance of 'carbonatable' rocks and industrial wastes (i.e. rich in MgO, CaO, if not Fe(II)O), coupled with significant GHG emissions from first-class nickel pyrometallurgical industries, make it a potential candidate for application of ex-situ mineral carbonation. The project conducted a worldwide analysis of the potential of ex-situ mineral carbonation using a dedicated SIG-based tool. Using a variety of materials the project also reviewed a number of critical issues associated with the aqueous mineral carbonatation process itself, with promising perspectives. Finally, through life cycle analysis of the system as a whole, ex-situ mineral carbonation was compared to mainstream CSC solutions. It was concluded that the viability of this CO2 storage option is located at the level of the process itself and lies with the optimisation of its operating conditions

Defining the operating conditions of the attrition-leaching process using thermodynamic process modelling

The attrition-leaching process aims at improving leaching performance when formation of passivation layers at the surface of leached particles is a severe limiting factor, as discussed recently by Julcour and coworkers (Julcour et al., 2015). This paper proposes a geochemistry-based modelling scheme for deriving the window of possible operating conditions for the attrition-leaching process to match the properties of the processed ore. The rationale is that the attrition-leaching process maintains the surface of reacting particles in an unpassivated state by continuous mechanical removal of surface leach layers, so that the process reactions can be modelled from thermodynamic equilibria throughout the duration of the process. The strength of the proposed modelling approach is that it bridges the gap between the properties of the ore and the process operating conditions. The present paper exemplifies the proposed process modelling route for derivation of the attrition-leaching process operating conditions in the context of the leaching of silicate ores, matching model predictions against controlled laboratory experiments. It is shown how thermodynamic modelling, when used in conjunction with a solid knowledge of the phases present in the system, can assist with deciding upon suitable process operating conditions. As an example, this firstprinciple modelling approach predicted that steel grinding medium would be converted into siderite (FeCO3) under a wide range of operating conditions, which led to questioning this initial choice of grinding medium for the attrition-leaching process under mineral carbonation conditions. It is emphasised that the same approach could be applied to ores of greater economic significance

About the foundations of direct aqueous carbonation with dissolution enhancing organic salts

Direct aqueous carbonation is a promising mineral carbonation route. Under mildly acidic conditions, this single-step carbonation process aims to simultaneously dissolve Ca/Mg-bearing silicates or wastes and precipitate Ca/Mg carbonates. By and large, since mineral dissolution is rate limiting due to the lack of protons at near-neutral pH, research has mainly been concerned with the issue of enhancing dissolution. By analysing the liquid phase, it has been established that polyacid organic salts can significantly enhance silicate dissolution under such unfavourable conditions. Comparatively little attention has been paid to the investigation of the very basis of the whole process, i.e. the concomitance of silicate dissolution and carbonate precipitation. By taking a close look at the solid phases in lizardite and olivine slurries, this work confirms the co-occurrence of magnesium silicate dissolution and magnesite precipitation inside a stirred reactor operating at 120°C, 20 bar of CO2 and 0.1M disodium oxalate, thereby bringing indisputable evidence that supports the foundation of direct aqueous carbonation with organic salts

Insights Into Nickel Slag Carbonation in a Stirred Bead Mill

This work is part of the ongoing development of the attrition-leaching carbonation process, a single-step aqueous carbonation technology that integrates a stirred bead mill. The principle of the attrition-leaching carbonation process is to continuously refresh the surfaces of reactive particles so that leaching can proceed unimpeded, yielding enhanced carbonation kinetics and yield. Invariably, attrition-leaching carbonation experiments carried out under controlled temperature and CO2 partial pressure conditions with different silicate-rich carbonation feedstocks - natural ores and nickel slags - show a carbonation yield that tends towards a plateau 20–50% below the stoichiometric yield. This repeatable behaviour raises the question as to whether the carbonation limitation is due to specific equilibrium side reactions of the carbonation feedstock or to a kinetic limitation of the attrition-leaching carbonation process. To try to provide some answers to this puzzling question, this reflexive paper implements a “thermo-kinetic” modelling methodology based upon geochemical equilibrium simulations and particle reaction models. The results obtained indicate that the observed slowing down of the carbonation process can be explained either by the formation of Mg- and/or Fe-rich silicates that precipitate at the expense of carbonates, or by a decrease in the efficiency of the attrition process over time. Indeed, either one of these mechanisms could explain the observed behaviour of the attrition-leaching carbonation process. However, the cross comparison of different data sources pleads in favour of the attrition-leaching carbonation performance being limited by the attrition process. Pending further confirmation, this tentative conclusion suggests that further development of the attrition-leaching carbonation process requires new knowledge about its inner workings, and that there may be ways to optimize the performance of this process beyond that based on standard stirred bead mill operating rules

Guiding mineralization process development with geochemical modelling

Mineralization is a CO2 utilization solution that can possibly meet all the CO2 mitigation criteria stated by the International Energy Agency, namely CO2 emissions reduction, economic self-sufficiency and scalability. Considered as a global niche markets solution, mineralization process development is particularly challenging, as its scope is territory dependent and combines feedstock selection, mineralization technology and undisruptive product valorization through local materials supply chains. Identification of potential mineralization pathways is a definite challenge. This paper argues that geochemical modelling is an indispensable guiding tool for mineralization process development. Owing to its capacity to predict product speciation for complex mineralization systems, the paper discusses a number of issues that illustrate and confirm the value of geochemical modelling for feedstock selection, product valorization and process engineering. Supporting arguments are provided in the context of the valorization of Ni-slags from the New Caledonian metallurgical industry. It is concluded that geochemical modelling is an undisputed building block for developing and modelling any mineralization process. Moreover, the paper argues that the full potential of geochemical modelling for mineralization process design requires its merging with high-level decision-making frameworks, such as regionalized life cycle assessment

Comprehensive analysis of direct aqueous mineral carbonation using dissolution enhancing organic additives.

Direct aqueous mineral carbonation using organic anions has been presented by many as a promising strategy for mineral carbonation, on the basis that additives such as oxalate increase the rate and extent of dissolution of magnesium silicates several folds. Through geochemical modelling and detailed solid characterization, this paper discusses and extends our current understanding of this process. The role of disodium oxalate as a dissolution enhancing agent for olivine is thoroughly examined through experiments in which all phases are carefully analysed. We show that under 20 bar of CO2 pressure formation of strong oxalate-magnesium complexes in solution and precipitation of MgC2O4,2H2O (glushinskite) impede any chance of obtaining significant amounts of magnesium carbonate. Other promising ligands from a dissolution perspective, namely citrate and EDTA salts, are also investigated. Contrary to oxalate, these ligands do not form any solid by-products with magnesium, and yet they do not produce better carbonation results, thereby casting strong doubts on the possibility of developing a direct aqueous mineral carbonation process using organic salts. Geochemical modelling permits successful simulation of the dissolution kinetics of magnesium silicate using a shrinking particle model that accounts for the precipitation of glushinskite, amorphous silica and a magnesium phyllosilicate at advanced stages of the dissolution process