CO2 pipeline

[PINUS]

Hallo,

I have some questions about CO2 pipeline issue
- What is the best way to transport CO2: as a supercritical or as a liquid?
- What is operating region (temperature and pressure range) for supercritical CO2? if the pressure is high enough, is it possible to lower the temperature under 31oC without phase change (is it still supercritical)?

I will be grateful for any answers

 

[zdas04]

"Best" is such a subjective modifier. "Most cost effective" is probably a better term.

Which phase to transport really depends on where you start and where you need to end up. I recently evaluated a project that was taking CO2 at atmospheric pressure to approx 1,000 psig (the dense phase line for pure CO2 is 1070 psia). I looked at going to dense phase, going to liquid, and transporting the gas at an intermediate pressure and using boosters close to the end-use. The economics were clearly in favor of transporting the intermediate gas. Liquefying the CO2 was amazingly expensive, but pumping was very inexpensive, the end result was pretty expensive (i.e., energy intensive). If your end point is 10,000 psia then the energy balance might be quite different.

On that project I started my analysis with pure CO2. About half way through I decided to make certain that the 9% CH4 in the gas stream would really be immaterial. As I generated my own Mollier Diagrams and Phase Diagrams for this mix I quickly found that it was very material and changed some of design parameters substantially. My recommendation to you would be to get a copy of NIST's REFPROP program and generate your own phase relationships for the gas you are actually working with rather than looking here for an average of averages.

David

 

[dcasto]

It depends, sorry, but your economics will be driven by your end needs and hopefully the purity issue zadas alludes to is not a factor.

Supercriticle CO2 transports wonderfully, high density, low viscosity.