The study of the Particle Size Distribution (PSD) during the processes of crystallization is a subsject of considerable interest, notably for the understanding of the inhibition mechanisms induced by some additives. Such an apportunity is well defined into the offshore exploitation of liquid fuels where the gas hydrate crystallization can plug production, treatment and transport facilities. The classical remedy to this problem is mainly thermodynamic additives such as alcohols or salts, but a new way of research is the use of dispersant additives which avoid crystals formation.

In this work, we show an original apparatus that is able to measure in situ the polychromatic UV-Visible turbidity spectrum in a pressurised reactor. We apply this technology to the calculation of the PSD during crystallization of methane hydrate particles in a stirred semi-batch tank reactor. We discuss the mathematics treatment of the turbidity spectrum in order to determine the PSD and especially the method of matrix inversion with constraint. Moreover, we give a method to calculate theoretically the refractive index of the hydrate particles and we validate it experimentally with the methane hydrate particles. We apply this technology to the study of the crystallization of methane hydrate from pure liquid water and methane gas into the range of temperature [0-2°C], range of pressure [30-100 bars] and range of stirring rate [0-600 rpm].

We produce a set of experiments concerning the influence of the stirring rate and of the pressure on the rate of absorption of the gas in the liquid, on the induction delay for the formation of the first particles, and on the size and the number of the particles during crystallization. Then we realize a model of the crystallization taking into account the processes of nucleation, of growth, of agglomeration and flotation. We compare this model with the experimental results concerning the complex influence of stirring rate at 1°C and pressure of 30 bars. Then we investigate the influence of additives such as Fontainebleau sand, Potassium Chloride and a surfactant such PolyVinylPyrrolydone.