Synergistic effects of nonylphenol ethoxylates and polyethylene glycols on performance of gas hydrate kinetic inhibitor

In this work, the kinetic inhibition effect of two non-ionic surfactants, nonylphenol ethoxylates (NPEs) and polyethylene glycols (PEGs) has been investigated on both nucleation and growth of ethane hydrate in the presence of a known kinetic inhibitor, polyvinylpyrrolidone (PVP). The results have been compared to experiments done without PVP at the same condition. Moreover, a kinetic model based on mass transfer has been applied to predict the kinetic coefficient. Experiments have been performed in an isochoric bath reactor under constant conditions with temperature of 275.15 K, initial pressure of 2.2 MPa and aqueous solutions of containing either 100 ppm NPE/PEG or 100 ppm NPE/PEG plus 1 wt.% PVP. The addition of NPEs and PEGs has extended the induction time remarkably and it has been prolonged about 2-6 times compared to pure water system. It has also been observed that inhibition efficiency is enhanced in the presence of PVP, so that it causes a more increase (about 4-20 times) in the induction time and decrease in the initial rate. With varying surfactant length included NPEs (NPE6, NPE10, NPE30 and NPE40) and PEGs (PEG200, PEG300, PEG400 and PEG600), NPE6 and PEG400 have shown the best inhibition performance. The results showed that NPE solutions was generally more effective than PEG on the induction time (increasing up to 16,000 s), while PEG solutions considerably reduce the rate of hydrate crystal growth and kinetic constant obtained by model.