Synergism of Ethers on the Kinetic Inhibition Performance of Poly(N-vinyl pyrrolidone) on Methane Hydrate in a Pilot-Scale Flow Loop

The kinetic inhibition of methane hydrate by polyvinylpyrrolidone (PVP) with two ether synergists was studied in a pilot-scale flow loop. An isothermal (273.15 K) and isobaric (6 MPa) experimental method was adopted, and the two ether synergists were 2-phenoxyethanol (EPH) and butyldiglycol (DGBE). We mainly focused on the growth kinetics of methane hydrate, and it was characterized from the consumption of methane gas with time. It was found that methane hydrate mainly formed in the bulk of the solutions when the inhibitors were present, and the appearance of the formed methane hydrate slurry was murky. In contrast, methane hydrate preferred to appear on the wet wall of the flow loop and on the liquid surface when the inhibitors were absent. These results reflect the fact that PVP, like most KHIs, is surface active. EPH was demonstrated to be a good synergist of PVP as it could significantly decrease the growth rate of methane hydrate whereas DGBE was found to be detrimental to the inhibition performance of PVP. Methane hydrate formed in the 1 wt % PVP + 1 wt % DGBE solution was prone to blockage of the flow loop. It was proposed that the adsorption and steric effects of EPH and PVP may play a role in the inhibition of methane hydrate in such a flow loop.