It can be concluded from the figure

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.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.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.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.