Transient analysis and calculation of supercritical CO2 long-distance pipeline in undulating terrain
Supercritical CO2 long-distance transportation pipelines are different from oil and gas pipelines but are similar to some liquefied hydrocarbon pipelines.Operation of these pipelines need to consider the phase change or even gasification caused by variations in critical temperature and pressure.It is also necessary to consider the impact of water hammer caused by the closure of the trunkline valve.A particular CO2 long-distance pipeline is taken as an example for simulation calculation,and a study was conducted on the water hammer and gasification after shutdown of supercritical CO2 pipeline.The study results indicate that the valve closure in the pipeline valve chamber will generate pressure waves,and the location of the closed valve will affect the water hammer pressure change,while the valve closure speed has a minor impact on the pressure.Both the location of the closed valve and ground temperature conditions will affect the gasification time after shutdown.Considering that in engineering practice,the medium for pipeline transportation is usually CO2 with some impurities,and simulation analysis of its physical characteristics reveals that impurities can alter the CO2 phase behaviour.This is reflected in changes to its critical temperature and pressure,and the generation of a two-phase gas-liquid envelope or region,thus affecting the supercritical region.The research results provide guidance for the long-distance pipeline transmission of supercritical CO2 and offer scientific basis and decision-making references for the engineering design and operation of long-distance CO2 pipelines.
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