Multistage Compressor Mcompr In Aspen Plus V10

Hello everyone,

I intend to compress a vapor stream from 5.06 bar to 28 bar using a multistage compressor MCOMPR. I input 2 stages and a discharge pressure of 28 bar. I get the following warning. Please help me understand why is the warning appearing and how to resolve it?

Add a separator after the cooler.

Bobby

Hi Bobby,

Thanks for your response. Indeed having a separator would help as when I see the stream components, it is 0.21 liquid fraction and rest is vapor which is what causing the two phase entering issue. However, I do not know how to add a separator within the intercoolers of multi-stage compressors. should I do it separately - meaning, having a normal compressor - cooler - separator, another compressor, cooler - separator and so on, until I get the final discharge pressure of 28 bar and T of 2 deg C? 

Thanks

Geetanjali

Edited by Geetanjali, 17 June 2021 - 04:46 PM.

Try connecting a stream from the 'liquid knockout' port on the Mcompr unit.

Yes, it worked with a "liquid knockout" port. No more warnings anymore. Thank you ! 

Thanks Pilesar and Bobby for your time and assistance.

Best regards,

Geetanjali

So, did you get the right interstage pressure? And would you recognize it as such?

Bobby.

Yes Bobby, I got good interstage pressure. First it goes from 5.26 to 12.14 bar in the first stage (Pressure ratio = 2.3), and then from 12.14 to 28 bar in the second stage (Pressure ratio = 2.3). But one thing, the power requirement is more now (1655 kW than previously i.e. 179 kW when I did not use a liquid separator).

I combine the liquid outlet from knock out port with the outlet from MCOMPR in order to feed in to a distillation column.

Edited by Geetanjali, 18 June 2021 - 02:58 PM.

Equal compression ratios is not necessarily consistent with best manufacturer offerings. But this is likely only an academic exercise? And, it may be more effective to feed the vapor and liquid to different trays in the column. Something a designer would explore.

Bobby

Thank you Bobby. Yes, it is an academic exercise. and I am feeding the vapor and liquid feeds to different trays in the column.

Thank you for your valuable suggestion. 

Geetanjali