A novel stirred microcalorimetric cell for DSC measurements applied to the study of ice slurries and clathrate hydrates

Abstract

A novel prototype of a microcalorimetric cell with in-situ stirring has been developed to perform DSC measurements under atmospheric or pressure conditions. After a brief technical description of the apparatus, preliminary tests are presented which analyzed the influence of the stirrer rotation on the heat-flow signal. Experiments were then performed with complex fluids such as ice slurries and clathrate hydrates formed with cyclopentane and with carbon dioxide. They took place in stirred and non-stirred conditions and the results obtained were then compared. It was proven that the rotation of the microstirrer in the measuring cell does not disrupt the heat-flow signal during the analysis. As regards the practical applications tested, the in-situ stirrer efficiently reduces crystallization metastability, increases the water-to-hydrate conversion, and reduces the amount of time needed for analysis. The dissociation enthalpy of cyclopentane (CP) hydrates was measured at atmospheric pressure; it is effectively very difficult to analyze this system with non-stirred calorimetry techniques because the two liquid phases are immiscible. The experimental results, in good agreement with other data found in the literature, showed complete water-to-CP hydrate conversion within a short period of time using a simple protocol. Experiments were also performed under pressure to demonstrate that CO2 hydrate phase equilibrium data could be obtained rapidly and easily. It is therefore our opinion that the potential of this novel technology has been thoroughly demonstrated.