在管道输送纯二氧化碳时，其所处的状态主要有气态、液态和超临界状态。由于

在管道输送纯二氧化碳时，其所处的状态主要有气态、液态和超临界状态。由于气 体本身的密度较小，因此输送相同质量的二氧化碳时，所占用的管道尺寸较大，且由于气体和管道的摩阻较大，因此管道的压降也较高，因此大规模、长距离输送时气态时不 利于输送的，而液态输送时管道中的温度需要保持较低，但是由于外部条件的变化，介质在输送过程中很容易发生相态变化，即液态变为气态，这样管道中就会有气液两相流 动，管道的性能也大幅降低，因此液态输送时对保温措施要求较高，通常情况，井口产出二氧化碳的状态为超临界状态，这里有大部分的压能可以被有效的利用，且二氧化碳 在超临界状态时又有很多有利于管道输送的特点，所以超临界输送成为了管道输送二氧 化碳的首选状态

When transporting pure carbon dioxide through pipelines, it mainly exists in gaseous, liquid, and supercritical states. Due to the small density of the gas itself, transporting the same mass of carbon dioxide requires a larger pipeline size, and due to the high friction between the gas and pipeline, the pressure drop of the pipeline is also high. Therefore, large-scale and long-distance transportation in the gaseous state is not conducive to transportation, while liquid transportation requires maintaining a lower temperature in the pipeline. However, due to changes in external conditions, During the transportation process, the medium is prone to phase changes, that is, the liquid state changes to a gas state, which leads to gas-liquid two-phase flow in the pipeline and greatly reduces the performance of the pipeline. Therefore, high insulation measures are required for liquid transportation. Usually, the state of carbon dioxide produced at the wellhead is in a supercritical state, where most of the pressure energy can be effectively utilized, Moreover, carbon dioxide in supercritical state has many characteristics that are beneficial for pipeline transportation, so supercritical transportation has become the preferred state for pipeline transportation of carbon dioxide

When transporting pure carbon dioxide by pipeline, its state mainly includes gaseous state, liquid state and supercritical state. Because the density of gas itself is small, when transporting carbon dioxide with the same mass, the occupied pipeline size is large, and because of the large friction between gas and pipeline, the pressure drop of the pipeline is also high, so it is not conducive to transportation when transporting gas on a large scale and in a long distance, while the temperature in the pipeline needs to be kept low when transporting liquid, but due to the change of external conditions, the phase state of the medium is easy to change during transportation, that is, the liquid becomes gas. In this way, there will be gas-liquid two-phase flow in the pipeline, and the performance of the pipeline will be greatly reduced. Therefore, thermal insulation measures are required for liquid transportation. Usually, the state of carbon dioxide produced by wellhead is supercritical, where most of the pressure energy can be effectively utilized, and carbon dioxide has many characteristics conducive to pipeline transportation in supercritical state, so supercritical transportation has become the first choice for pipeline transportation of carbon dioxide.