4 replies to this topic

[P Thakur]

Dear All,

 

I need to transport CO2 (99.9% dry basis) over a distance of 50 km via pipeline. Ambient temperature (not soil temperature) varies from 5 C to 50 C. CO2 critical condition is 73.9 bar & 31.1 C. I need to decide the operating condition of pipeline.

 

Option 1: Transport CO2 in liquid phase. Lets say at 20 C at 60 bar

Option 2: Transport CO2 in supercritical phase. Lets say at 35 C and 100 bar.

 

Which of the above option would be better considering wide variation in temperature range?

Whether pipeline should be aboveground or underground?

 

Thanks

[Art Montemayor]

Your data is insufficient and not clear.  Are your pressure units absolute or gauge?

 

More importantly, what do you mean by 20 ^oC and 60 bar?   Do you think that you will not have a pressure drop?  In other words, is your data for the entrance to the pipeline, or is it for the terminus of the pipeline?  It makes a BIG difference since CO₂ at 20 ^oC and 57.2 barA is a VAPOR.  That means you only have 2.79 bars available for pressure drop before your liquid turns to gas.

 

That is why CO₂ is transported by pipeline as a supercritical fluid with substantial pressure for the drop.

[P Thakur]

Dear Art,

 

The units are in bar absolute

 

After posting, I read some details about another pipeline for hydrocarbon.

 

Based on that I infer that my inlet Pressure & Temp should be in liquid state and size of pipeline should be such that after pressure drop and heat input /loss from soil, CO2 exist in liquid state only at outlet of pipeline.

 

Is that a correct way to proceed?

[Technical Bard]

Commercial CO2 pipelines are generally designed at conditions such that they are supercritical along the whole length, or if cooling cannot be avoided, liquid at the outlet.  It is necessary however to check the phase behaviour at all points along the pipeline, taking consideration of pressure drop and static head.  If the pipeline rises over a hill, you must stay above the critical pressure at the top of the hill.

[P Thakur]

Thanks Bard for your response.

 

I have seen reference of CO2 pipelines in US wherein super-critical conditions are maintained throughout the length. In India, the ambient temperature varies from 7 deg Celsius to 48 deg Celsius, so in your view/experience would it be better to keep supercritical conditions throughout the length or would it be better to keep it in liquid conditions?

 

Or do you think it is okay to keep supercritical conditions at inlet to pipeline and let it change to liquid phase at outlet of pipeline?

 

I agree that while performing simulation, I need to check properties throughout the length and ensure the impact of elevation change and heat transfer from soil to buried pipeline are taken into account.