4 replies to this topic

[ziba]

how can i design safe blowdown of 300 psig liquid co2 to atmosphere without noise or damage of piping or solid co2 ice formation?

 

i know i can ask silencer(muffler) designers to size it accordingly but what about piping and configuration what should i consider to prevent ice blockage or noise reduction some vendors design mufflers with 3 components 1-diffuser 2-shell and 3-noise reducer but my boss wants a piping configuratin

 

like i have to look at total design from truck driver opening valve to  liquid line and to  atmosphere discharge vai silencer, he says that ice blockage should not happen and i have to engineer it all by myself??? .

 

if i want to blowdwon 20000 lb/hr from 300 psig down to atmosphere ,,,,,i would have a pipe and a valve and a muffler what about distances, should i be at triple point of co2 ? and why?

 

how do i attach my excel file

Edited by ziba, 16 February 2016 - 02:05 PM.

[Art Montemayor]

Ziba:

 

You can't.

 

It is thermodynamically impossible to expand liquid CO₂ from a pressure of 300 psig down to atmospheric pressure without generating dry ice snow.

 

Without even using the Mollier Diagram where you can clearly see that I am correct, you can appreciate this phenomena by using a common CO₂ fire extinguisher.  Although the liquid inside the extinguisher is at ambient temperature, it still produces dry ice snow when expanded.  The amount of dry ice produced is even greater when liquid CO₂ at 300 psig (& approximately -8 ^oF) is expanded.

 

More chemical engineers should use - or learn how to use - the Mollier Diagram or the equivalent Temperature-Entropy Diagram.

[breizh]

On top  of what Art explained , you may want to take a look at the document attached .

 

Good luck

 

Breizh

[ziba]

Thanks Art, I appreciate your feed back,

 

but we have mufflers that are designed to be used for liquid phase CO2 blowdown, the problem is that the mufflers are noisy still, some of the users face safety like the piping failure and also ice blockage,

 

How come muffler designers sell these mufflers,  with diffuser head inside the shell of mufflers design seems work I have seen from Fluid kinetics and IMI company and universal technology ,

 

They claim it can prevent the ice formation by diffuser part, basically a pipe closed on end and holes around pipe shell, i have mollier chart of co2, i have seen these mufflers work well when the size of muffler is large and as long as pressure remains above triple point,  tx

[Art Montemayor]

Ziba:

 

There is no such thing as a "muffler" that will allow you to purge the liquid CO₂ out of a 300 psig & -1 oF storage tank without creating dry ice snow (solid CO2) when the purge is done to atmospheric pressure.  If you have installed such a device with the sales claim that no solids will be produced, you have been sold a "bill of goods".  Nothing can change the thermodynamics of the adiabatic free expansion as clearly shown on the Mollier Diagram.  That is why Breizh was kind enough to supply you with the thermo data.

 

I have been associated with a lot of CO₂ projects - all involved in one way or another with all its physical phases, and no one would dream of attempting to "muffle" the expansion with an external device.  Unless you keep it constantly heated, you will eventually plug it with dry ice particles.  Muffler designers sell these devices simply because you are willing to buy them.

 

Your information is confusing.  What do you mean by "i have seen these mufflers work well when the size of muffler is large and as long as pressure remains above triple point"??  If you are expanding the liquid to a pressure ABOVE the triple point (approx. 75 psig) then, of course, you will not form a solid CO₂ particle.  But then that is NOT A BLOW DOWN.  A blow down is always understood to mean a purge to atmospheric pressure.  You should always be clear and specific in your engineering explanations and identify all pertinent data involved.

 

Who is "IMI company" and what is their expertise in liquid CO₂?  Since I often consult in CO₂ projects, I'd like to know that information.