The Throttling Characteristics And Safety Control Of Piped Fluid With High CO₂ Content

Pipelines with high CO₂ content are widely used in Carbon Capture,Utilization and Storage technology.Throttling is the most common method for pipeline pressure regulating.CO₂ has a strong Joule-Thomson Effect,and the existence of gaseous impurities and water makes throttling process much more complicated.Currently,the throttling safety control technology of pipeline with high CO₂ content has gone unheeded,and the pertinent theories are inadequate.In order to ensure the safety of throttling process for pipelines with high CO₂content,it is of great significance to do research on the throttling characterisitics,flow characterisitics and deposition mechanism of particles downstream the throttling valve.Firstly,the CO₂-H₂O phase equilibrium process is described by?-?method,and two different methods for calculating the water content of piped CO₂ are put forward,including simplified thermodynamic model and empirical formulas.Based on the result of error analysis,the application of the two methods is proposed.Then based on BWRS EOS,phase equilibrium principle and thermal equilibrium equation,a throttling model of multiphase flow with high CO₂ content is put forward.In this model,the throttling process of multiphase flow is divided into 3 parts,gas throttling process,CO₂ solubility equilibrium process and gas-liquid thermal equilibrium process.The model has high accuracy under the conditions of pipeline transportation.The effect of impurities and gas-water ratio on throttling temperature drop is analyzed using the model,and several safety control measures for throttling temperature drop of pipeline with high CO₂ content are proposed accordingly.Thereafter on the basis of theoretical research,a set of experimental device is set up for steady and transient throttling experiment of piped fluid with high CO₂ content.Steady throttling temperature drop is measured and compared with that calculated by the theoretical model.Transient experimental phenomena including flow state and solid particle deposition have been observed.The relationship between experimental phenomena and pressure-temperature conditions is analyzed.In addition,the critical pressure drop is measured under experimental conditions.In order to make further study on the particle deposition phenomena,a CFD model based on gas-solid two-phase flow theories is developed on open sourse CFD software OpenFOAM to describe the transient multiphase flow and particle deposition downstream the throttling valve.The effect of different inlet parameters on deposition characteristics is analyzed using the CFD model.Based on the work described above,measures for preventing particle deposition during transient throttling process of pipelines with high CO₂ content are proposed.