Natural Gas Hydrate Formation and Decomposition in the Presence of Kinetic Inhibitors. 2. Stirred Reactor Experiments

A newly fabricated, stirred reactor was used to investigate hydrate inhibition and decomposition in the presence of two commercial, chemical kinetic inhibitors, polyvinylpyrrolidone (PVP) and H1W85281, as well as two antifreeze proteins (AFPs), type I and type III. The longest induction times and the slowest growth rates were observed with HIW8581, with the fastest growth recorded for PVP. Type I AFP (APP-I) was a more effective inhibitor, with respect to induction time and growth, than either PVP or type III APP (APP-III). Complete hydrate decomposition occurred earlier in the presence of any of the inhibitors compared to water controls. However, depending on the type of inhibitor present during crystallization, hydrate decomposition profiles were distinct, with a longer, two-stage decomposition profile in the presence of the chemical kinetic inhibitors (PVP and H1W85281). The fastest, single-stage decompositions were characteristic of hydrates in experiments with either of the AFPs. These results argue that thought must be given to inhibitor-mediated decomposition kinetics in screens and designs of potential kinetic inhibitors. This is a necessary, practical consideration for industry in cases when, because of long shut in periods, hydrate formation may be unavoidable, even when inhibitors are utilized.