Effect of SDBS surfactant on gas-liquid flow pattern and pressure drop in upward-inclined pipelines

Liquid loading is a common phenomenon for natural gas gathering and transportation in hilly terrain pipelines, and traditional mechanical pigging technology is usually employed to remove the liquid loading in these pipelines. However, this technology has some obvious limitations and risks in complex pipeline operation conditions. Surfactant injection was presented as an alternative to promote liquid drainage in this study. To further understand the effect of surfactant on the flow characteristics of a gas-liquid flow, an experimental investigation of the flow pattern and pressure drop with and without surfactant was conducted using visual observation and pressure drop measurement methods in the upward-inclined section of a hilly terrain pipeline. The experimental pipeline was made of acrylic glass with an inner diameter of 50 mm and an inclination angle of 10 degrees. Air and deionized water were used as working fluids, and sodium dodecyl benzene sulfonate (SDBS) with concentrations of 100, 400 and 800 parts per million (ppm) was used as surfactant additive in the experiment. The superficial liquid and gas velocities ranged from 0.005 to 0.100 m/s and from 2.0 to 30.0 m/s, respectively. The intermittent flow and segregated flow with and without foam formation were classified into various sub-flow patterns based on the gas-liquid distribution and pressure drop fluctuation characteristics. The distribution of the flow patterns was summarized under different working conditions. The experimental results enhance the understanding of the morphology and evolution process of gas-liquid flow with a surfactant.