Construction of decompression model and analysis of leakage flow rate of supercritical carbon dioxide in pipelines
By using an industrial scale pipeline of DN250 in nominal diameter and 260 m in length,the supercritical carbon dioxide leakage tests in small holes were performed.The phase change process in the pipeline during supercritical carbon dioxide leakage was discovered,including supercritical phase carbon dioxide release,gas-liquid two-phase carbon dioxide release,and gas phase carbon dioxide release successively.Based on the results,a method for establishing carbon dioxide leakage theoretical models was raised by setting up the supercritical phase leakage model,the gas-liquid phases leakage model,and the gas phase leakage model respectively.The transferring parameters of different carbon dioxide phase leakage models were determined.The theoretical model of the carbon dioxide decompression process was realized.The calculation flow chart of every leakage phase model was set up.A calculation program was compiled by using MATLAB software to solve the theoretical model.The reliability of the model is verified by comparing the calculated pressure drop curve with the experimental data obtained in industrial-scale pipelines.Based on the theoretical calculation results,the influences of the initial pressure,initial temperature,and leakage diameter on the leakage mass flow rate were discussed.Results show that the biggest deviation between the pressure curves of theoretical calculation and the experimental test is about 22.8％.When the initial pressure varies from 8 MPa to 9.5 MPa,the influences of initial pressure on pressure drop and mass flow rate are small.When the initial temperature varies from 33 ℃ to 39 ℃,the time of pressure decreasing down to the critical value gradually increases.The pressure decreasing time obviously larges with the decrease of leakage diameter.The leakage mass flow rate fluctuates at the initial decompression stage,then decreases with the pressure decreasing.Results can provide a reference for understanding the decompression mechanism of supercritical carbon dioxide and pipeline leakage risk.
NETL
NSTL
万方数据
维普
