Frédéric Gruy

Interest of in situ turbidimetry for the characterization of methane hydrate crystallization: Application to the study of kinetic inhibitors

In this paper we describe a new experimental set-up which makes possible the in situ determination of the particle size distribution of methane hydrate during its formation in a pressurized reactor. It has been installed on two research sites: one at the Institut Francais du Petrole (IFP) and the other at the Ecole des Mines de Saint-Etienne (EMSE). Thanks to this apparatus, new data can be obtained, in particular concerning the granular aspects of the crystallization processes and the reproducibility of the results. Particularly, we propose a new experimental procedure which allows us two important improvements: • a better reproducibility of the induction time, • the possibility of doing a large number of experiments in a day (around fifteen). Using this protocol, the effect of some kinetic inhibitors of the crystallization processes are shown: increase of the induction time and/or decrease of the quantity of hydrate formed.

In-line study of crystal fragmentation in a stirred reactor

This paper presents an example of the use of a turbidity multi-wavelength sensor for an in-line study of fragmentation of crystals in an agitated vessel. Thanks to this in situ sensor, it is possible to continuously record the turbidity spectrum of a suspension. Particle size distributions can be calculated for grain diameters between 0.2 and 10 μm. This sizing technique is applied here to the fragmentation of potassium sulphate in ethanol and in its aqueous solution. A qualitative and quantitative study of the phenomenon of fragmentation can be thus performed. Determination of the influence of mass and stirring rate gives an indication of the prevailing fragmentation mechanisms. The large discrepancies observed between the behaviors in ethanol and in water are due to agglomeration.

Experimental Study and Modeling of Inclusion Aggregation in Turbulent Flows to Improve Steel Cleanliness

Getting clean steel is becoming a major challenge nowadays, both for the production of competitive steel and for making easier the process exploitation. As a consequence, there is a need to study the behavior of solid particles (called inclusions) in liquid steel, responsible for the cleanliness defects observed in steel products. The addition to steel of a deoxidizing element such as aluminum provokes the formation of solid particles (Al 2 O 3 ). These inclusions have a density smaller than steel so they can be eliminated by flotation and captured by the liquid slag layer on the steel surface. The paper proposes some mechanisms for the formation of inclusion cluster in liquid steel and examines the influence of the wetting condition on inclusion growth, using a cold experiment.

Calculation of the refractive index of pure gas hydrates using a modified Lorenz-Lorentz model. Application to methane hydrate

Abstract The calculation of the refractive index of methane hydrate is carried out using a modified Lorenz-Lorentz model. The occupancy of methane into the structure of the hydrate is taken into account. It is calculated from van der Waals and Platteuuw theory and shows small changes when the experimental pressure varies from 30 to 110 bars and when the experimental temperature varies from − 3 to + 12 °C. We have observed great changes of the relative index of refraction with the methane occupancy (the relative index of refraction is the ratio between the refractive index of the methane hydrate and of liquid water). The relative index of refraction characterizes the ability of the methane hydrate particles to scatter the light. Thus, the occupancy factor of methane must be taken into account when the calculation of size distribution uses the optical properties of particles.

Theoretical aspects of Ostwald ripening in systems with high solubility and high solid volume fraction

Many models have been developed to describe Ostwald ripening. The most recent of them have dealt with systems of high solid volume fraction (φ > 0.01). To obtain an exploitable solution, all these models require several simplifications: assumption of low solubility, assumption of motionless fluid phase, no consideration of the spatial arrangement of the grains, analytical or numerical approximation methods. In this paper an unidimensional linear model (row of grains) of Ostwald ripening is proposed which can be applied to the most general and difficult situation, i.e. systems with high volume fraction in highly soluble grains. This model does not require any simplifying assumption. Its validity can be proved from already published theoretical results. Within this model, the spatial arrangement of the grains and the associated connectivity effects which have not been studied so far, can be taken into account. These effects become particularly important at high volume fraction.