Hydrate Induction Time with Temperature Steps: A Novel Method for the Determination of Kinetic Parameters

Gas hydrate formation usually occurs with a certain delay after a system composed of water and a hydrate forming gas is put under suitable thermodynamic conditions of pressure and temperature. This delay period is called the "induction time", and because of its large variability within a single experimental setting, hydrate formation is often referred to as a stochastic process. The evaluation of induction times, together with other measurements, is taken as an indication for the efficiency of hydrate inhibitors, and they are usually carried out by simply putting the experimental system under chosen P/T conditions and then waiting for the hydrate to form and measuring the time elapsed. In this paper, we present an improved procedure by which the variability of hydrate induction times can be remarkably reduced, while keeping a good correlation of measured induction times with the respective temperatures as obtained by a constant cooling method. In this procedure, temperatures are lowered by 0.5 degrees C after each time span of 3 h with no hydrate formation. Induction times obtained in this way show a remarkably lower coefficient of variation as compared to a standard induction time measurement.