(154d) Droplet Transport in near-Horizontal Low Liquid Loading Flows

Low liquid loading gas-oil-water flow is widely encountered in wet gas pipelines.  Even though the pipeline is fed with single-phase gas, the condensation of the heavier components of the gas along with traces of water results in three-phase flow. In such cases top of the line corrosion is widely encountered due to condensation of water droplets containing dissolved corrosive gases. Most of the corrosion inhibitors used are in the liquid phase and need to be transported to the top of the pipe to prevent corrosion. The dominant mechanism for transport of liquid to the top, for large diameter pipes is through droplets entrained from liquid film at bottom of the pipe. However, droplet transport studies in pipes are scarce and are mostly based on experiments for small diameter (0.0025 m to 0.0076 m) pipes.  Scaling up of these models leads to inconsistent results since flow distribution could be different for larger diameter pipes. Moreover there is no work on transport of droplets in three-phase flow which is encountered in wet gas pipelines.

In the current work, droplet transport in three-phase flow for horizontal and slightly inclined pipe has been studied. A new isokinetic sampling system is developed to study droplet flux for oil/gas and oil/water/gas flows in a 0.015 m (6 in.) diameter flow loop. Experiments were performed for inclination of +2° and -2° from the horizontal. The flow conditions for initiation of atomization and droplet transport to top of the pipe have also been studied.

The droplet flux was found to decrease due to presence of water in the liquid phase for the same total liquid flow rate. Water-cut in the entrained liquid was found to be lower than the input water cut. In addition, the total droplet flux and water-cut in the entrained liquid was found to be lower for downward inclined pipe as compared to upward inclined pipe.