从图中可以得出：当压力在大于7.39MPa的某一固定值、温度在30.9

从图中可以得出：当压力在大于7.39MPa的某一固定值、温度在30.95℃以下时， 二氧化碳的压缩因子逐渐变大，当温度超过临界温度30.95℃时，其压缩因子由于超临界性的影响突然变大；当压力小于临界压力7.39MPa、温度较低时，二氧化碳处于液体状态，压缩因子较小，但是随着温度的增大，相态逐渐由液态变为气态，相应的压缩因子也变大。 <br>由出二氧化碳在正常的管道输送条件下其压缩因子是非线性的，并且杂质对其影响 是十分敏感的，但是当系统压力超过8.5MPa左右时杂质对压缩系数的影响就会趋于平缓，因此在设计管道压力参数时，为了减小杂质对压缩性能的影响，一般设计管道压力大于8.6MPa，这样就可以避免由于温度变化引起管道中介质的压缩系数变化。 <br>二氧化碳输送管道上一般采用ASME-ANSI 900#法兰，由于许用应力原因，一般在 38℃时允许的最大操作压力为15.3MPa，而若想管道在更高的操作压力下允许，则需要强度更高的法兰与之相配套。 <br>综上可见，与气态和液态二氧化碳相比，由于超临界二氧化碳密度大、粘度小、摩擦阻力小、温度敏感度小等原因，更利于二氧化碳的管道输送。

It can be concluded from the figure that when the pressure is at a fixed value greater than 7.39MPa and the temperature is below 30.95 ℃, the compressibility factor of carbon dioxide gradually increases. When the temperature exceeds the critical temperature of 30.95 ℃, its compressibility factor suddenly increases due to the influence of supercritical; When the pressure is lower than the critical pressure of 7.39MPa and the temperature is low, carbon dioxide is in the liquid state and the compressibility factor is low. However, with the increase of temperature, the phase state gradually changes from liquid to gas, and the corresponding compressibility factor also increases.<br>Under normal pipeline transportation conditions, the compressibility factor of carbon dioxide is nonlinear, and the influence of impurities is very sensitive. However, when the system pressure exceeds about 8.5MPa, the influence of impurities on the compressibility will tend to be gentle. Therefore, when designing pipeline pressure parameters, in order to reduce the influence of impurities on the compressibility, the design pipeline pressure is generally greater than 8.6MPa, This can avoid changes in the compression coefficient of the medium in the pipeline caused by temperature changes.<br>ASME-ANSI 900 # flange is generally used on carbon dioxide transmission pipelines. Due to allowable stress, the maximum allowable operating pressure is generally 15.3MPa at 38 ℃. However, if the pipeline is to be allowed to operate at a higher pressure, a stronger flange is required to match it.<br>In summary, compared to gaseous and liquid carbon dioxide, supercritical carbon dioxide is more conducive to pipeline transportation of carbon dioxide due to its high density, low viscosity, low frictional resistance, and low temperature sensitivity.

It can be concluded from the figure that when the pressure is above a fixed value of 7.39MPa and the temperature is below 30.95℃, the compressibility factor of carbon dioxide gradually increases, and when the temperature exceeds the critical temperature of 30.95℃, its compressibility factor suddenly increases due to the influence of supercritical; When the pressure is less than the critical pressure of 7.39MPa and the temperature is low, carbon dioxide is in a liquid state with a small compressibility factor, but with the increase of temperature, the phase state gradually changes from liquid to gas, and the corresponding compressibility factor also increases.<br> Under normal pipeline transportation conditions, the compressibility factor of carbon dioxide is nonlinear, and the influence of impurities is very sensitive. However, when the system pressure exceeds about 8.5MPa, the influence of impurities on the compressibility factor tends to be gentle. Therefore, in order to reduce the influence of impurities on the compressibility, the pipeline pressure is generally designed to be greater than 8.6MPa, so as to avoid the change of the compressibility factor of the medium in the pipeline due to temperature changes.<br> ASME-ANSI 900# flange is generally used in carbon dioxide transmission pipeline. Due to allowable stress, the maximum allowable operating pressure is generally 15.3MPa at 38℃. If the pipeline is allowed under higher operating pressure, a flange with higher strength is needed to match it.<br> To sum up, compared with gaseous and liquid carbon dioxide, supercritical carbon dioxide is more conducive to the pipeline transportation of carbon dioxide because of its high density, low viscosity, low friction resistance and low temperature sensitivity.