3 replies to this topic

[alokjaiswal]

Dear forum members,

Please find attached herewith the datasheet of CO2 Compressor which is being used to compress CO2 coming from Ammonia Plant to High pressure section of Urea Plant. The details of each stage is given in datasheet. A small flow diagram is also attached for better understanding.

My query is:

1. Why the CO2 flow (wet) has increased in third stage?
2. Why the RH is being mentioned as 100% for 2nd, 3rd, and 4th stage?

The CO2 compressor has been installed in 1995.

Alok Jaiswal

Attached Files

•  datasheet.pdf   263.28KB   88 downloads
•  CO2 COMPRESSOR.pdf   63.44KB   65 downloads

[breizh]

Hi ,
Can you describe a little bit more the intercooler ( Shell & tubes ?) and separator ?

Breizh

[S.AHMAD]

1. 100% humidity means the partial pressure of water vapor is equal to the water vapor pressure at the condensing temperature. The gas stream is saturated with water vapor.
2. Most likely the requirement of minimum flow to avoid surge point. Surge point increases with speed. As you are aware that the speed of stage 3 & 4 is higher than speed of stage 1 & 2.
3. Check the compressor performance curve to confirm the above.

[Art Montemayor]

Alok Jaiswal:

Your data sheet is erroneous if we are to believe your schematic flow diagram. Your PFD shows that all the gas stream goes through each successive stage – and that is essentially the normal way that you would have the process work if you are trying to recover all the available CO2 to convert it into Urea.

Therefore, what is going into every stage after the 1 st is progressively less and less mass. This is due to the fact that every stage is compressing and cooling the gas mass handled by it. When this is done, the exit gas mass out of each stage is SATURATED WITH WATER VAPOR after it exits the related intercooler. That cooled, water-saturated stream then enters the next stage for more compression – after you have REMOVED THE CONDENSED WATER in the 2-phase separator located after the intercooler. That means that the total mass entering each stage is less than the mass entering the stage previous to it. Your data sheet indicates (in hand writing) that the mass flow rates through the stages is: 57,926 kg/hr, 57,187 kg/hr, 59,140 kg/hr, and 58,123 kg/hr – which is IMPOSSIBLE IF WE BELIEVE YOUR SCHEMATIC DIAGRAM.

I believe that answers both your questions.