Liquid CO2
Liquid CO2
(OP)
I've installed a liquid CO2 system but keeping getting gas CO2 at the discharge rather than liquid. I've tried various things such as bringing the supply/return closer to the machine and increasing the line size but for some reason I can not get the system cold enough to get liquid. It's running at about 285 psi at 20 F. I have no experience with CO2. Is there a consultant or applications engineer who could help?
thanks
thanks
RE: Liquid CO2
What is the pressure at the discharge?
It looks to me like you are right on the liquid / gas phase line.
If you're taking as off and dropping pressure then it will gasify.
CO2 is interesting stuff, but I don't understand your system at present.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Liquid CO2
RE: Liquid CO2
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Liquid CO2
RE: Liquid CO2
Good Luck,
Latexman
RE: Liquid CO2
Is this a circulating loop for cooling or something?
what's the pressure and temp on the inlet of the pump?
At 20F (~-5C) you need to be at about 30 bar (450psi) or more to be in liquid CO2.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Liquid CO2
The saturation temperature at 285 psig is about -1F, so at 20F you definitely have gas. If you are using a blackner recirculation pump you will need an external refrigeration system to recondense gas being sent back to the tank. Most bulk liquid co2 tanks have ports which allow for refrigerant to flow through copper coils located in the headspace of the tank.
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Not making a decision is a decision in itself
RE: Liquid CO2
Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?
-Dik
RE: Liquid CO2
Yep.
Good Luck,
Latexman
RE: Liquid CO2
Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?
-Dik
RE: Liquid CO2
Consider this pamphlet about CO2 properties.
Good luck
Pierre
RE: Liquid CO2
RE: Liquid CO2
"but for some reason I can not get the system cold enough to get liquid." Well what are doing at the moment?
"closer to the machine " - what machine?
What are you trying to do? Get to liquid at a certain pressure?
Use the CO2 for cooling?
Or can you increase the pressure?
How is pressure being maintained in the loop?
what's the flowrate / velocity in your 1 1/2 " pipe?
Temperature at start and stop of your loop?
Pressure at start and stop
Pressure in the reservoir
285 psi you need to get to <0F.
And then a bit more to keep it liquid
Can you draw a diagram, post a drawing, give us the whole picture?
If you don't need it to keep this thread going then any consultant will just be asking you the same questions.
But who designed this? Can't you ask them?
Where in the world are you located?
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Liquid CO2
Get to liquid at a certain pressure? No set process pressure but need to be discharging liquid CO2 for the rubber
Use the CO2 for cooling? Yes
Or can you increase the pressure? No, it's a set pressure at the tank
How is pressure being maintained in the loop? Mainly with the tank pressure (285 psi)
what's the flowrate / velocity in your 1 1/2 " pipe? I don't know
Temperature at start and stop of your loop? 0 F and 20 F
Pressure at start and stop 285 F
Pressure in the reservoir 285 F
It's closed loop system but pull off liquid when we need to wrap rubber.
Here's what we found. We opened the supply valve at the bottom of the tank and by the pump and it had gaseous CO2. I'm thinking the return line is liquid CO2 judging by the frost and in similar processes the pump is frozen over. In this case there is no frost on the pump. I'm thinking the supply line is piped to gas side of the tank inside. Tried to get drawings from the manufacturer but the tank is too old. In the picture below the line on the right is the return and the line on the left is the supply. If I swap lines, is there a problem putting liquid CO2 on the gas side of the tanks.
Thanks
RE: Liquid CO2
I believe you have a two phase coolant system, but I don’t know what other components you have that I’ve seen mentioned. The only place you have near 100% liquid CO2 is the point it comes out of the tank. Immediately after that, due to frictional losses and heat gain, you have a two phase mixture. The further down the line it goes and the more heat it picks up, the greater the gas content in the two phase mixture.
Link to possible Consultant1 or Consultant2
Google something like using two phase carbon dioxide as coolant or two phase carbon dioxide coolant consultants
Good Luck,
Latexman
RE: Liquid CO2
Thanks for posting that co2 "pamphlet" - i have been looking for it since i "lost" it. UNION dont have it on the web pages these days (unfortunately). A star for you
Best regards, Morten
--- Best regards, Morten Andersen
RE: Liquid CO2
What I don't think any of us understand at the moment is how do you cool the returning gaseous CO2?
Somewhere if you want a substance to stay below a certain temperature then you need to have a cooling mechanism. This can be boiling off the liquid or some mechanical means such as a chiller loop.
Can you actually sketch out your complete loop system with pressures and temperatures where known. A consultant will ask for this in the first instance or charge you to create one.
Some confusing things - you say you tried to get drawings from a manufacturer but it was too old - but in the OP it said you had just installed it??
What is the pressure and temperature in the tank in the tank??
When you know that you can find out where on the phase diagram you are.
You state the pressure at the discharge of the pump as 285 but not it's inlet pressure ( though you state storage pressure is 285 so what is the pump doing??)
To understand CO2 you need to use the phase diagram I posted above and annotated below.
It sounds to me that in your storage tank (285 psi @ 0F) you may just be at point A where there is liquid CO2 in the tank. But it might be a tank of gas as this is right on the line. Even if it's a liquid if you maintain the same pressure ( how do you get it to flow?) and the temperature increases as you go along your line, then the liquid CO2 will boil as it moves right on the graph but at the same or similar pressure. Therefore you will get gas at your mould at point B.
Then somehow it returns to the tank as a gas. There needs then to be some mechanism to cool it back down to 0F to liquify it.
Long and short of it is that if you want to get liquid CO2 at 285 psi to the mould the temperature needs to be 0F or lower. Or if the temperature is 20F then you need to arrive at point C - about 400 psi.
Does this make sense?
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Liquid CO2
You may consult your supplier of Co2 to get support .
I've attached a document from Praxair using N2 to cool reactor ( Indirect cooling) .
What is not clear to me in your description is the recycling of CO2 gas to the storage tank , something is missing here .How do you intend to liquify this gas prior to return to Storage .
My 2 cents
Pierre
RE: Liquid CO2
Typically, a LCO2 tank would need to be > 9 barG at all times to avoid this.