AD–OX: A sequential oxidative process for water treatment— Adsorption and batch CWAO regeneration of activated carbon

A sequential process for water treatment involving usual adsorption on activated carbon (AC) followed by wet air catalytic oxidation of the adsorbed pollutants has been carried out in a fixed bed reactor with a mixture of two model pollutants. The first step achieves water purification while the second one reduces the organic pollution but also, more importantly, performs some AC in situ regeneration. The experimental work has been done with AC yet extensively used and stabilized by long range continuous oxidation. The two steps have been analyzed successively showing very important drop of adsorption capacity with respect to fresh AC but efficient oxidative partial regeneration. As expected with used AC no more evolution occurs in between two consecutive runs. The first step of competitive adsorption has been simulated by a model leading to higher diffusivities than estimations based on correlations. The main features of the complex second step, involving simultaneous non-isothermal desorption and three phase catalytic reaction, are qualitatively explained

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

Towards a new oxidation process using ozone to regenerate coked catalysts

This work focuses on the regeneration of a zeolite catalyst from industry deactivated by fouling with coke. To replace high temperature combustion, a common and energy intensive process, an oxidation process under milder conditions (50°C-200°C) has been investigated using ozone. Coked zeolite has been oxidized by an ozone stream in a fixed bed reactor, and regeneration kinetics was followed by analyzing carbon content of the particles and ozone concentration at the outlet. The effects of temperature, time on stream and ozone inlet concentration on carbon removal efficiency were studied. Moreover, elemental analysis showed that a maximum of 74.3% of carbon could be removed from the coked catalyst after 6.5 h. Moreover, the total specific surface area, the pore size distribution and the total pore volume (mainly mesopores) have been evaluated on coked and regenerated samples

Ultrasonic sludge pretreatment under pressure

The objective of this work was to optimize the ultraso und (US) pretreatment of sludge. Three types of sew-age sludge were examined: mixed, secondary and secondary after partial methanisation ("digested" sludge). Thereby, several main process parameters were varied separately or simultaneously: stirrer speed, total solid content of sludge (TS), thermal operating conditions (adiabatic vs. isothermal), ultra-sonic power input (PUS), specific energy input (ES), and for the first time external pressure. This parametric study was mainly performed for the mixed sludge. Five different TS concentrations of sludge (12-36 g/L) were tested for different values of ES (7000-75,000kJ/kg TS) and 28 g/L was found as the optimum value according to the solubilized chemical oxygen demand in the liquid phase (SCOD). PUS of 75-150 W was investigated under controlled temperature and the "high power input - short duration" procedure was the most effective at agiven ES. The temperature increase in adiabatic US application significantly improved SCOD compared to isothermal conditions. With PUS of 150 W, the effect of external pressure was investigated in the range of 1-16 bar under isothermal and adiabatic conditions for two types of sludge: an optimum pressure of about 2 bar was found regardless of temperature conditions and ES values. Under isothermal conditions, the resulting improvement of sludge disintegration efficacy as compared to atmospheric pressure was by 22-67% and 26-37% for mixed and secondary sludge, respectively. Besides, mean particle diameter (D[4,3]) of the three sludge types decreased respectively from 408, 117, and 110 μm to about 94-97, 37-42, and 36-40 μm regardless of sonication conditions, and the size reduction process was much faster than COD extraction

Effect of partial wetting on liquid/solid mass transfer in trickle bed reactors

The wetting efficiency of liquid trickle flow over a fixed bed reactor has been measured for a wide range of parameters including operating conditions, bed structure and physico-chemistry of liquid/solid phases. This data bank has been used to develop a new correlation for averaged wetting efficiency based on five different non-dimensional numbers. Finally liquid/solid mass transfer has been determined in partial wetting conditions to analyse what are the respective effects of wetting and liquid/gas flow turbulence. These effects appear to be separated: wetting being acting on liquid/solid interfacial area while the liquid/solid mass transfer coefficient is mainly connected to flow turbulence through the interstitial liquid velocity. A correlation has been proposed for liquid/solid mass transfer coefficient at very low liquid flow rate

Etude du transfert gaz-liquide en présence d’une troisième phase finement divisée

Le transfert de masse entre l’air et l’eau peut être accéléré ou au contraire ralenti par l’ajout d’une troisième phase, minoritaire, finement divisée. Ces effets peuvent être dus soit à des effets sur le coefficient de transfert côté liquide kL, soit à des effets sur l’aire interfaciale, a. Le but de cette étude est d’identifier le lien entre le transfert gaz-liquide et l’hydrodynamique en système air-eau-troisième phase. Cette phase est, dans notre cas, constituée de particules solides (systèmes gaz-liquide-solide) ou de gouttelettes d’une phase organique non miscible dans la phase aqueuse (systèmes gaz-liquide-liquide). Les liquides organiques utilisés sont le décane, le 2-éthyl-1-hexanol, le toluène et le 1-octène (0,2 à 2% vol.). Pour les solides, deux silices du commerce ont été expérimentées (0,25 à 1 g/l) ; les particules solides ont un diamètre de 4µm ou 28µm. Chaque silice a subi un traitement la rendant partiellement hydrophobe, ceci afin de tester l’influence de l’hydrophobicité sur le transfert. Les résultats obtenus pour le transfert de masse montrent un faible effet positif pour la silice hydrophobe en particules de 4µm. En revanche, l’utilisation de liquides organiques a conduit à une réduction systématique de l’aire interfaciale et à un ralentissement consécutif d’environ 60% du transfert entre l’air et l’eau aux vitesses de gaz les plus élevées par référence au cas diphasique

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