Numerical Investigation of Deposition Characteristics of Solid CO₂ During Choked Flow for CO₂ Pipelines

Choke valves are applied to control the pressure in CO₂ pipeline. However, the temperature of fluid would drop rapidly because of Joule-Thomson cooling (JTC), which may cause solid CO₂ generate and block the pipe. In this work, a three-dimensional Computational Fluid Dynamic (CFD) model, using the Lagrangian method, Reynold’s Stress Transport model (RSM) for turbulence and stochastic tracking model (STM) for particle trajectory, was developed to predict the gas-solid CO₂ flow and deposition characteristics downstream pipeline. The model predictions were in good agreement with the experimental data published in the literature. The effects of particle size, flow velocity and pipeline diameter on the fluid-particle flow characteristics were examined. Results showed that the increase in the flow velocity would cause a decrease in particle deposition ratio and there existed the critical particle size that caused the deposition ratio maximum for each velocity. The paper also presents the effects of particle motion on different deposition regions. Moreover, the main deposition region (the sudden expansion region) is the easy to be blocked by the particles. With the increase in pipeline diameter, the particle deposition ratio was decreasing. In addition, it was recommended for Stokes number to avoid 3-8 St.