Enhancement of the performance of modified starch as a kinetic hydrate inhibitor in the presence of polyoxides for simple gas hydrate formation in a flow mini-loop apparatus

Abstract

The main objective of the present work is the enhancement of the performance of modified starch as a kinetic inhibitor in the presence of polyoxides such as ethylene oxide (PEO) and polypropylene oxide (PPO) for simple gas hydrate formation in a flow mini-loop apparatus. Polyoxides such as PEO and PPO are high molecular weight polymers that are not kinetic inhibitors by themselves. For this investigation, a laboratory flow mini-loop apparatus was set up to measure the induction time and rate of gas hydrate formation when a hydrate forming substance (such as C1, C3, CO2 and i-C4) is contacted with water containing dissolved inhibitor in the presence or absence of polyoxides under suitable temperature and pressure conditions. In each experiment, water containing inhibitor blend saturated with pure gas is circulated up to a required pressure. Pressure is maintained at a constant value during experimental runs by means of required gas make-up. The effect of PEO and PPO on induction time and gas consumption during hydrate formation is investigated in the presence or absence of modified starch as a kinetic inhibitor. The results showed that the induction time is prolonged in the presence of PPO compared to the inhibitor alone. The efficiency of PPO is higher than the PEO, because, the induction time for simple gas hydrate formation in presence of PPO is greater than by using the PEO in presence of kinetic hydrate inhibitors.Also, the results show, that the gas consumption in the presence of modified starch is lower that in the absence of this inhibitor for all experiments. Moreover, the inhibition effect is clearly seen as well as the synergism between the inhibitor and PEO or PPO and this effect is higher in the presence of PPO.