Experiment on steady-state throttling process of piped CO₂ at different phase states

In the process of CO₂ pipeline transportation, throttling can lead to large CO₂ temperature drop, and consequently threatens the safe operation of the pipeline. In this paper, the steady-state throttling experiment was conducted on CO₂ of different phase states by using the independently designed CO₂ throttling experiment device to acquire internal parameters inside the pipeline. And the influences of pressure difference before and after the throttling, CO₂ phase state before the throttling and impurity N₂ content on the CO₂ temperature drop after steady-state throttling were investigated. It is indicated that CO₂ temperature drop after the throttling increases with the increase of pressure difference before and after the throttling and decreases with the increase of N₂ content. The throttling effect of CO₂ is the strongest at gas state, secondly at supercritical state and the weakest at liquid state. As for the same pressure difference, the higher the pressure before the throttling, the smaller the CO₂ temperature drop after the throttling. In addition, the CO₂ temperature drop after the throttling is less affected by the pressure before the throttling at gas state than at liquid states.