Developments in the understanding and modeling of the agglomeration of suspended crystals in crystallization from solutions

International audienc

Étude expérimentale et modélisation d'une précipitation avec agglomération entre cristaux de morphologies différentes : application au molybdate de strontium

L'étude expérimentale effectuée sur la précipitation du SrMoO4 a montré qu'il présente plusieurs morphologies (bipyramide et fuseaux) possibles sous forme d'agglomérats multiéchelles. Les paramètres opératoires: concentration initiale en SrMoO4, température et vitesse d'agitation ont une influence sur la morphologie et la taille des cristaux et agglomérats. La précipitation du SrMoO4 a été suivie en phase liquide par conductimétrie dans un réacteur discontinu. En fin de précipitation, la forme des cristaux et des agglomérats a été observée au MEB/FEG et la distribution de taille de particules (DTP) mesurée.La poudre a été analysée par DRX, BET et porosimétrie Hg. L'objectif de ce travail est le développement d'un modèle d'agglomération couplé avec la nucléation et la croissance cristalline de façon à déterminer la morphologie des agglomérats obtenus. Le logiciel Parsival a été utilisé pour résoudre les bilans de population et ainsi obtenir les DTP et les profils de désursaturation

Thermodynamics of cyclopentane hydrates formation from brine: experimental and modelling study

International audienceCyclopentane hydrates-based salt-removal has been considered to be one promising technologies for desalination because it requires a low amount of operating compared to traditional methods such as thermal distillation, membrane separation, or freezing. In order to design a desalination, or water treatment, plant, it is necessary to understand both the thermodynamics of crystallization of hydrates (CPH) in presence of salt, and the kinetics. Therefore, this study aims to determine and model the equilibria of cyclopentane hydrates in the presence of electrolytes. Eight salt mixtures have been considered: NaCl, KCl, NaCl-KCl, CaCl2, Na2SO4, MgCl2, MgCl2-NaCl, MgCl2-NaCl-KCl, with a wide range of concentrations. Two successive experimental procedures, quick and slow, have been applied to determine equilibrium temperatures. The objective of the quick procedure is to provide an initial estimate of the equilibrium temperature. Then, the slow procedure is used to obtain more accurate data. Experimental results show that equilibrium temperatures dropped significantly with an increase in salt concentration, whatever the kinds of salt. In comparison with the literature, the final slow procedure in pure water provides, or with NaCl, provide results very close to studies of Kishimoto et al. [2] and Zylyftari et al. [3], obtained either by slow dissociation or micro Differential Scanning Calorimetry (&#0181-DSC). Moreover, salt co-precipitation can be achieved simultaneously with the cyclopentane hydrate formation. For instance, the eutectic point of four phase equilibrium of {liquid water + liquid CP + CPH + Na2SO4.10H2O} has been obtained in this study. This provides possibility for by-products, or value added products, recovery thanks to CPH. Afterward, four thermodynamic approaches have been considered for the results modelling. One is based on Standard Freezing Point Depression method. Another one considers the very new Hu-Lee-Sum (HLS) correlation, designed to predict the suppression temperature of clathrate hydrates when an additive is introduced into the system. The two last models are based on van der Waals and Platteeuw model, using either Kihara potential, or a correlation instead (ABOC).All models provide data with a difference lower than 0.7°C compared to experimental results. However, the best method is the ABOC method (activity based occupancy correlation). This approach uses a correlation between the clathrate occupancy, and the water activity. It furnishes equilibrium temperatures within 0.2°C uncertainty

Kinetic modelling of methane hydrate formation and agglomeration with and without anti-agglomerants from emulsion in pipelines

GasHyDyn : Logiciel de simulation de la composition et de la stabilité des hydrates de gazNational audienceOffshore systems mainly containing crude oil, natural gas and water operate at low temperature and high pressure which favour conditions for gas hydrate formation and agglomeration. Gas hydrate is a serious issue in flow assurance; it may cause many troubles, especially, plugging in oil and gas pipeline. This work is to intend to develop a kinetic model to predict gas hydrate formation, agglomeration and plugging in flowlines based on the experimental data obtained from Archimede Flowloop from the work of Mendes-Melchuna (2015). In this model, the mean droplet size of emulsion will be calculated from flow parameters to evaluate the surface area of droplets which are very critical parameters for kinetic model of gas hydrate formation in emulsion. It is important to note that anti-agglomerants (AAs) may modify the water-oil interfacial tension leading to smaller mean droplet size. A preliminary study of the emulsion formation and behaviour will contribute to a better understanding of the hydrates formation and agglomeration

Formation d’hydrates sans et avec additif antiagglomérant en variant le débit et la fraction d’eau

National audienceLa cristallisation des hydrates de méthane pendant l’extraction de pétrole est une source majeure de risques, notamment concernant le bouchage des pipelines. La circulation d’huile et d’eau dans une pipe induit la formation d’une émulsion. A haute pression et basse température, l'eau peut être combinée avec des composants gazeux légers, résultant dans la formation d’hydrates, qui sont des structures solides dont l’agglomération est capable de boucher le pipeline.La cristallisation des hydrates de méthane a été étudiée de manière intensive au cours des 30 dernières années, surtout à basse teneur en eau. Cependant, les puits en fin de vie de production ont un pourcentage d’eau plus important que parfois l’eau devient la phase dominante, l’huile devenant la phase dispersée. Dans ce cas de figure le processus de cristallisation des hydrates de gaz doit être étudié et comparé aux systèmes où l'eau est la phase dispersée.Ce travail est une étude paramétrique réalisé dans une boucle de circulation capable de reproduire les conditions de la formation d’hydrate dans les pipelines sous marins, en faisant varier la teneur en eau (30% jusqu’à 100%) et le débit (200 L.h-1) et 400L.h-1), afin d'observer et comprendre la cristallisation d’hydrate à partir d’un mélange de Kerdane® (C11-C14) et d'eau, en présence de méthane. Ensuite, la même étude paramétrique a été réalisée en présence d'un additif dispersant, afin de comprendre le comportement de l’additif. Les expériences sont suivies par mesures de perte de charge, masse volumique, taille et forme des gouttelettes et hydrates. A partir de l’étude réalisée, le mécanisme de formation de l’émulsion et des hydrates sans et avec additif dispersant a été développé

Monitoring industrial crystallization using Acoustic emission

International audienceAcoustic emission (AE), which has been successfully applied for monitoring a rather wide variety of solids elaboration processes, was almost never evaluated in the field of industrial crystallization for pharmaceutical or chemical products. Few papers reported that crystallization processes give rise to acoustic emission signals that could be related to the development of the basic crystallization phenomena. This study is intended to demonstrate new perspectives opened up by the possible use of acoustic emission (AE) as a non-intrusive and non destructive sensor for monitoring crystallization with a particular focus being put on real industrial processes. The preliminary results of the study will be reported in this work namely concerning the ability of the EA to follow the crystallization processes under different operating conditions and different types of crystallisation, and the obtained crystals in terms of particle size distribution and agglomeration degree

Validation of an agglomeration model for multiple agglomeration

International audienc

Multiple agglomeration in strontium molybdate precipitation

International audienc

Modélisation de la précipitation du molybdate de strontium : effet de la vitesse d'agitation

National audienc

Experimental flowloop study on methane hydrate formation and agglomeration in high water cut emulsion systems

Thème de cette communication: International Conference on Integrated Petroleum Engineering (IPE)International audiencehydrate risk also increases. Especially in the offshore systems, operating at low temperature and high pressure, conditions are favourable to the formation of gas hydrate, from the combination of liquid water and gas molecules, under the form of a solid phase. It is a serious issue in the flow assurance; it may cause many troubles, up to plugging.This work brings new understanding on hydrate kinetics of crystallization, nucleation and growth, agglomeration, breakage and deposition under flowing. We focused on high water cut emulsion systems under flowing and we studied the role of commercial anti-agglomerants or low dosage hydrate inhibitors (AA-LDHIs). These additives can disperse hydrate particles to prevent plugging. More specifically, the topic of this study concerns methane hydrate crystallization, agglomeration and hydrate slurry transportation in a flowloop at high water cut systems, with and without AA-LDHI. We have been used up-to-date measurements and calculations among FBRM (Focused Beam Reflectance Measurement), PVM (Particle Video Microscope), pressure, pressure drop, flowrate/density, hydrate conversion and hydrate volume fraction. In this study, we performed the experiments at very high water volume fractions (80-90-100%) in laminar regime (150L/h) with and without anti-agglomerants. The results showed that using gas-lift system (riser), dramatic events were witnessed with a high rate of methane hydrate formation, followed with a quick agglomeration and leading to plugs, even with additive. But we also observed a dramatic foaming event, even at low AA-LDHI concentration of 0.01%.We concluded our work with a discussion of the agglomeration mechanisms, based on a quick hydrate formation and agglomeration rates