6 replies to this topic

[saiedeh]

Dear Friends,

I need to decide about the best cooling method for cooling liquid CO2 with 3 Million tons per year from 50 to 20C. Plant location is around 1 kilometer away from the sea. Seawater temperature is between 4C(winter) to 13C (Summer).
I can consider cooling with seawater, but I'd like to know which other alternatives I have.

Thanks

[Art Montemayor]

Saiedeh:

Please be specific and accurate in your description of what you propose.

If you know a little about the properties of CO₂, you know that the liquid phase can only exist below the critical temperature of 30.9782 ^oC. If you claim to have LIQUID CO₂ at 50 ^oC, it must be a very special form of CO₂. Perhaps you made a mental mistake in not stating that the CO₂ initially is at 50 ^oC (superheated) and a pressure greater than its critical pressure (73.773 bara) and you want to cool this to 20 ^oC (which would result in liquid CO₂. Am I correct?

You can certainly cool and condense the high pressure CO₂ with seawater. You can also use a refrigerant – such as ammoia or the Freons. You could also resort to using an engineered, CO₂ refrigerating cycle whereby you employ the same CO₂ compressors you use to reach the critical pressure. This is a very old and efficient cooling system that I used many years (50) ago.

[saiedeh]

Art,

You are right. The CO2 mixture (It's not pure CO2, its critical pressure and temperature are 81 bara and 29C) is supercritical fluid initially, at 50C and 100barg.It's going to be cooled down to 20C to make sure it's liquid and can be pumped.
I'd like to choose the best cooling media. Seawater have corrosion problems. Cooler has to be made of Titanium. As you said I can use refrigeration. But usually refrigeration been used for lower temperatures. I don't whether it's practical to use it for reaching 20C.

Thanks
Saiedeh

Edited by saiedeh, 22 February 2011 - 03:39 AM.

[Art Montemayor]

Saiedeh:

We don't know where you are located and what other options you have available for cooling. You are the only one who knows that. Therefore, all we can identify as your options are:

• Seawater;
• Cooling water tower system (you need makeup water);
• mechanical refrigeration system;
• atmospheric air.

Of the above heat sinks, the only ones I personally know as reliable are:

• Cooling Water System;
• mechanical refrigeration system;
• Seawater.

No knowing anything else, I would make my selection in that order.

[saiedeh]

Art,
This site is 1 km away from the North sea. Seawater temperature is 4C(winter) to 13C (summer). Air temperature is between 0C(winter) to 20C(summer).
I don't think cooling water which is produced in a cooling tower can give us enough cooling to reach 20C.
Whst about Mechanical refrigeration? What medium do you suggest? Is mechanical refrigeration cheaper or more reliable than seawater?

Thanks
Saiedeh

[Art Montemayor]

Saiedeh:

Thank you for the additional information and data. However, we need more specific basic data in order to furnish specific suggestions.

I have condensed CO₂ in various countries, situations, and projects. I have resorted to using cooling mediums such as cooling water towers, seawater, ammonia, Freons, and even CO₂ itself.

The mechanical refrigeration I have employed was done in different manners – all depending on the situation, the type of liquid CO₂ required, and the economics involved. At this point, without a full description of all the basic data, the scope of work, and not even a simple PFD, all I can offer is a general description of a chiller system in a workbook that I started for this thread. I can elaborate – to the degree that you desire. You have my interest, but I have to have the above information in order to be specific.

I hope this helps you out.

Attached Files

•  Cooling & Condensing CO2.xlsx   86.73KB   40 downloads

[saiedeh]

Thank you very much.