4 replies to this topic

[HKk]

Dear Friends

Till now our suction to CO2 compressor is Bone dry CO2. However after some change in plant operating condtions we are anticipating 1.9% of moisture in the CO2. Presently CO2 compressor is not designed to handle wet CO2 . Is it possible to dry out CO2 using adsorbtion process. The co2 is available at 0.26kg/cm2_g pressure . temperature 15 C & Flow is around 25000NM3/Hr.

Regards

[Art Montemayor]

HKK:

First of all, you have to give us basic data that is important, basic, and specific to the application. You don’t tell us WHAT KIND OF COMPRESSOR. Is it:

• Reciprocating piston compressor?
• Screw compressor?
• Centrifugal compressor?

You also don’t tell us the number of compression stages and the final discharge pressure.

I suspect you have a centrifugal compressor but I don’t know the discharge pressure. I also suspect you won’t have any problems handling wet CO₂, but you don’t tell us the details of the materials of construction. So all I can do is suspect and guess.

You also don’t tell us if you need “Bone dry CO₂” as the compressor’s discharge. If so, there should be no problem installing an adsorbent dryer (preferably Activated Alumina adsorbent) on the discharge and producing CO₂ with approximately -100 ^oF atmospheric dew point.

[HKk]

Dear Sir

Thanks a Lot for your response.

The compressor is 2 barrel 3 stage centrifugal compressor , with 2 intercooler s & 1 aftercooler. Final Discharge Pressure is 34 Kg/cm2_abs
At the discharge side we have a wash tower to wash the CO2 with water . So the dryer at the discharge side is not required. The compressor impeller is of SS but the piping is of CS & no knockout drums are at discharge side of intercoolers.

However at the suction side I want to dry out the gas so that condition at the inlet does not change otherwise we may have to go for many changes in the compressor side like piping changes to SS & installation of KOD's etc. Since the pressure of Suct CO2 is low, is it possible to use alumina/ mol. sieve dryer ?

[Art Montemayor]

HKK:

Thank you for furnishing the additional basic data.

I see no problem in your compressor setup as it is, assuming that the added molecular weight will not be a problem at the suction when the CO₂ is wet. You should check this out with your compressor manufacturer.

For over 100 years, CO₂ has been produced, compressed, and dried using compressors and piping made up of 100% carbon steel. I don’t see any problem using your compressor for wet gas – as long as the manufacturer approves. To prove my point, look at the compressor “barrels” and main material of construction: the impellers may be SS, but I’ll bet the rest of the components are carbon steel. Your wash tower is – I guess - Carbon steel together with all the associated piping and instruments.

Yes, there may be some corrosion with wet CO₂, but the rate is usually tolerable. Wet CO₂ is presently compressed to much higher pressures and the materials of construction for the compressors is usually carbon steel. I have never seen a Stainless Steel compressor body or cylinder.

I don’t believe you can economically justify installing an adsorbent dryer at the suction side. The vessels would be HUGE. And besides that, you have to saturate the gas after compression! And to make things worse, if we are to be alarmed by potential wet CO₂ corrosion, than the adsorbent towers should also be fabricated of stainless steel! That is not the answer.

[HKk]

Dear Sir ,

Thanks for the informative mail to enlighten me with some very good & basic knowledge.

Regards