Molecular Dynamics Method To Simulate The Process Of Hydrate Growth In The Presence/Absence Of Kinetic Hydrate Inhibitors

The plugging phenomenon of clathrate hydrates often occurs in natural gas transportation pipelines,which is very likely to cause serious industrial problems.Therefore,it is great significant to develop efficient gas hydrate risk prevention and control technology.Kinetic hydrate inhibitors(KHIs)are widely used as low dosage hydrate inhibitors,but their inhibition mechanism is still unclear.Therefore,in this thesis,the molecular dynamics simulation method was employed to study the inhibition process of hydrate growth.The inhibition mechanisms of the selected KHIs are clarified at the molecular level.The main contents are summarized as below:(1)The growth processes of hydrates were simulated with the inhibitor PVP located at different positions in the solution.By comparing the potential energy changes of the system,the amount of methane,and the number of hydrate cages,it is found that the closer the inhibitor is to the surface of the hydrate nucleus,the better the inhibition effect is.(2)The inhibition effects of PVP,PVP-A,and PVP-E at the gas-liquid interface were compared.By analyzing the potential energy changes of the system,the dissolution rate of methane,and the number of hydrate cages,it is found that PVP-A shows the best inhibition performance.Moreover,the configurations of the inhibitors at the gas-liquid interface were analyzed,and the inhibition mechanisms of the kinetic inhibitors were further studied.(3)The inhibition effects of PVP,PVP-A,and PVP-E on the surface of hydrate nucleus were compared.The results show that PVP has the best inhibition effect.In addition,it is found that the growth of methane hydrate can be effectively inhibited when the inhibitor is stably adsorbed on the surface of methane hydrate nucleus.By comparing the growth of the hydrate and observing the configuration when the inhibitor binded to the surface of the hydrate,the relationship between the inhibitor structure and its inhibition effect was further clarified.(4)Finally,the advantageous locations of the three inhibitors were investigated.By analyzing the dissolution rate of methane,the growth of hydrate cages,and the snapshots at different times during the growth of hydrate when the same inhibitor was located at the gas-liquid interface and one side of the hydrate nucleus surface,it is found that three inhibitors have different advantageous locations for better inhibition.