Experimental and theoretical investigation of simple gas hydrate formation with or without presence of kinetic inhibitors in a flow mini-loop apparatus

Gas hydrates are ice-like crystalline compounds, which form through a combination of water and suitably sized guest molecules under low temperature and elevated pressure conditions. These solid compounds give rise to problems in the natural gas oil industry because they can plug pipelines and process equipment. Low dosage hydrate inhibitors are a recently developed hydrate control technology, which can be more cost-effective than traditional practices such as methanol and glycols. The kinetics of hydrate growth has been modeled by numerous authors who have measured the gas consumption rate during hydrate formation in batch agitator reactors.The main objective of the present work is to investigate experimentally of simple gas hydrate formation with or without the presence of kinetic inhibitors in a flow mini-loop apparatus. To predict the gas consumption rate during hydrate formation in this system, the rate equation based on the Kashchiev and Firoozabadi model for simple gas hydrate formation in a batch system was developed for this objective. To complete the theoretical evaluation of gas hydrate formation through the pipeline with or without the presence of kinetic hydrate inhibitors (KHIs), a laboratory flow mini-loop apparatus was set up to measure the induction time for hydrate formation and the uptake rate when a hydrate forming substance (such as C1, C3, CO2 and i-C4) is contacted with water in the absence or presence of dissolved inhibitor under suitable temperature and pressure conditions. In each experiment, a water 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 the required gas make-up. The effect of pressure on gas consumption during hydrate formation is investigated with or without the presence of polyvinylpyrrolidone (PVP) and l-tyrosine as kinetic inhibitors at various concentrations. A good agreement is found between the predicted and experimental data with or without the presence of KHIs. The total average absolute deviation percent between the experimental and predicted gas consumption is found to be 15.8% and 14.9% for simple gas hydrate formation with or without presence of kinetic inhibitors, respectively.