Inhibition of natural gas hydrate in the system containing salts and crude oil

Antifreeze proteins are a kind of proteins which can protect organisms at subfreezing temperatures by inhibiting the growth of ice crystals, they are becoming increasingly attractive as a kind of biological kinetic hydrate inhibitors (KHIs). In this work, the inhibition effect of an antifreeze protein (mSA-RmAFP1) on synthetic natural gas (SNG) hydrate nucleation in the case of existing salts and crude oil was investigated using a rocking cell apparatus. In addition, three kinds of environment friendly KHIs (starch, chitosan and glycine) as well as a commercial inhibitor (PVP) were tested for comparison. The results showed that 2250 p.m. mSA-RmAFP1 can inhibit SNG hydrate nucleation more effectively than PVP in various systems (pure water, salt water, salt water + 15 vol% crude oil). Starch, chitosan and glycine present weak inhibition ability on SNG hydrate nucleation. The inhibition strength of various chemicals can be ranked as follows: starch < chitosan < glycine < PVP < mSA-RmAFP1. The SNG hydrate crystal growth and decomposition process were investigated, it was found that mSA-RmAFP1 can decrease the SNG hydrate growth rate and production as well as the onset decomposition temperature. However, PVP increased the SNG hydrate production and onset decomposition temperature. For investigating if the results have dependence on experimental apparatus, the performance of various inhibitors were tested using a micro differential scanning calorimeter (DSC). It was found that the results are consistent with those obtained from the rocking cell apparatus. This study can provide detailed research information on the application of AFPs and contribute to understand hydrate formation and decomposition behavior for the system containing KHIs in realistic conditions.