Investigation On The Long Distance Pipeline Transportation Technology Of Supercritical CO₂

Long distance pipeline transportation is one of the important links in CO₂ capture and storage technology.Compared to the others,the supercritical state of pipeline has the characteristics of high transportation efficiency.Therefore,in this paper,the long distance pipeline transportation technology of supercritical CO₂ was studied based on the flue gases captured from Shengli Power Plant.In this paper,the PR equation was used to compare the change rules with pressure and temperature of density,viscosity,thermal conductivity,specific heat of constant pressure and compression coefficient of three components pure CO₂,CO₂-N₂,CO₂-SO₂ by Matlab programming.In the supercritical region,the density,viscosity and thermal conductivity increase with the increase of pressure,and the increase rate decreases gradually;decrease with the increase of temperature,the change curve tends to be gentle.Near the critical point,the specific heat of constant pressure increases suddenly and reaches the maximum value.When it is far from the critical point,the specific heat value decreases.Under certain temperature,the compression coefficient reaches the minimum value around 10 MPa,and then increases with the increase of pressure.Under certain pressure,the compression coefficient increases with the increase of temperature.With the increase of N₂ content,the density decreases,the viscosity decreases,the conduction system decreases,the specific heat of constant pressure increases,and the compression coefficient increases.With the increase of SO₂ content,the density increases,the viscosity increases,the thermal conductivity increases,the specific pressure decreases and the compression coefficient decreases.The minimum operation pressure and temperature of the calculation object are 8.17 MPa,33.46℃ when the supercritical state is maintained in the process of pipeline transportation.Pipe diameter calculation using the McCollum model,according to the "oil & gas gathering design manual on" standard to determine the wall thickness,combined with supercritical CO₂ heat transfer correlation and pressure drop correlation calculation to establish the model of hydraulic calculation and thermodynamic calculation.In the inlet parameters for 10²0MPa,35⁵0℃,obtained the pipeline size of different inlet parameters,and according to the "GB/T 9711-2011 Specification for steel industry of oil natural gas pipeline system",to determine the minimum standard pipe size.Finally,the influence of inlet parameters,elevation difference and ambient temperature on maximum safe conveying distance of CO₂ in supercritical state is analyzed.Under the premise of setting the first and last station,the maximum safeconveying distance is 106 km when the inlet pressure is 10 MPa and inlet temperature is40℃.10 MPa inlet pressure and 50℃ inlet temperature,the maximum safe conveying distance is 234 km.The minimum inlet pressure and temperature for conveying 100 km distance are 9.68 MPa and 39.82℃.At 10 MPa and 40℃,when the pipe length is 100 km and the elevation difference is greater than 40 m,the outlet temperature is lower than33.46℃,the outlet pressure meets the requirements.Increase the pipe length to 200 km,when the elevation difference is greater than 120 m,the outlet pressure is lower than the minimum operating pressure of 8.17 MPa.With the increase of ambient temperature,the outlet pressure decreases slightly and the outlet temperature increases obviously.