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US Iceman
12-05-2006, 06:49 PM
Here is a link from Danfoss that shows the phase changes in CO2 as the pressure or temperature is changed.

This is a very good demonstration of the refrigerant properties for solid, liquid, and vapor.

The video is about 8 minutes long but worth the waiting period to see this.

http://www.danfoss.com/businessareas/refrigerationandairconditioning/training+and+education+material/co2+phase+changes.htm

(8.5 MB)

chemi-cool
12-05-2006, 07:19 PM
Very interesting video.

Thanks for bringing the link

Chemi:)

Alan B
13-05-2006, 05:47 AM
Excellent video. Thanks for posting it.
Alan B

fuzzy logic
13-05-2006, 06:15 PM
Wow. Thanks for the link. I saw this Vid 2 weeks ago but didn't know where to find it. Thanks mate

Tycho
13-05-2006, 08:00 PM
great video, we had some Danfoss representatives visit our office to tell us about their new products a few years ago, and they showed us this video, pretty good :)

sagittarius
17-05-2006, 10:56 AM
Thank you anymore US Iceman.Whatever about Co2 refrigeration I am glad to study!

Buddha
20-12-2007, 06:12 PM
Link seems to have been removed, anyone save a copy of this movie? Sounds like it would be a nice teaching tool.

Samarjit Sen
20-12-2007, 06:31 PM
The link is

http://www.danfoss.com/BusinessAreas/RefrigerationAndAirConditioning/EducationAndTraining/CO2+Phase+Changes.htm

US Iceman
20-12-2007, 10:55 PM
Thank you Samarjit for re-posting the valid link.;)

Grizzly
20-12-2007, 11:55 PM
Thanks.
Samarjit for reintroducing the link and Iceman,
thanks for a very interesting link. My exposure to Co2 has been very limited and this is a good start.
It appears to be gaining popularity within the U.K.
and with the supermarkets driving it forward. I asume it will become more common?
Grizzly

Plank!
24-12-2007, 04:15 PM
Thanks.
Samarjit for reintroducing the link and Iceman,
thanks for a very interesting link. My exposure to Co2 has been very limited and this is a good start.
It appears to be gaining popularity within the U.K.
and with the supermarkets driving it forward. I asume it will become more common?
Grizzly

CO2 will gain ground in the UK and i guess the rest of the world too.
Tax incentives will push it further into all sectors.
One area we are seeing huge growth is the IT market. Under-desk and server rack mounted CO2 pumped evaporators provide a huge cooling potential in a small crowded work space.
TBH its nice kit to work with, our CO2 systems are mostly oil free, so very little maintenance - except for valve reliability issues, but thats been dealt with and soon things will be easier than ever ;)

Giannis
25-12-2007, 12:47 AM
Very Good video about CO2

Thank you

Alex_DK
23-01-2008, 06:49 PM
What valves have you had problems with Plank? Many valves need a bit of oil to stay tight but your boss knows that already, I think.

Alex_DK
23-01-2008, 09:34 PM
Regarding the Danfoss video, it shows the phase change happens more or less instantly. In fact if the valve had not been so open the you can make a ice-slurry. A patent running the system just under and over tells about such a way to use CO2. CO2 is a very nice refrigerant to work with once you have tried it.

mr saw
11-02-2008, 11:01 PM
hello plank, was wondering about job opportunities with c02. like potential earnings, ease of employment, that kind of thing. main exp commercial fridge and ac including chillers.thanks.

cmorris69
04-04-2008, 11:35 PM
Facinating video, and thanks for posting it.

We've just commissioned a CO2 Recovery system at our brewery which actually recovers more CO2 from fermentation than we need for the beer packaging process. Without a doubt a facinating system.

Josip
06-04-2008, 11:47 AM
Hi, cmorris69 :)

welcome to RE forums....



...........

We've just commissioned a CO2 Recovery system at our brewery which actually recovers more CO2 from fermentation than we need for the beer packaging process. Without a doubt a facinating system.

.... can you explain a little more your recovery system.....

.....cooling and liquefaction of CO2 with ammonia or *****, piston or screw compressor/s.... manufacturer and type of CO2 compressor/s

... do you keep your liquid CO2 in big thermos tanks ...

Best regards, Josip :)

cmorris69
06-04-2008, 03:09 PM
Certainly. At full design production for this facility, more CO2 is generated by the fermentation process than is required for use in blending and packaging the beer. Since production demands are cyclical, there are times when we are over-producing or under-producing CO2. Between the CO2 "generation" side and the "usage" side are five, 100,000 pound-liquid storage tanks which provide a flywheel effect. Sounds like alot but production typically requires 120,000 pounds per day OR MORE...

The CO2 gas collects at the top of the fermentation vessels and is piped into a header which delivers it to the recovery system, which consists of a number of components.

First is a vessel called a Foam Trap which uses an intermittant water spray to knock down foam carried over from the fermenters. Can't let foam proceed beyond this point, so safety logic here CAN shut the whole recovery system down if necessary.

Next is a centrifugal booster which maintains the proper pressure within the Foam Trap and back up the header into the fermenters. Low pressure here (around 4 to 6 inches of water) is good as it enhances the fermentation process. The Booster discharges at a pressure of between 3 and 7 psig. Manufactured by Gardner-Denver (Hoffman Blower), 200hp.

Next in line is a vertical tower called the Scrubber, which uses a continuous water spray to wash un-desirable components from the CO2 gas.

Now come the high pressure compressors. CO2 gas from the Scrubber at 3 to 7 psig gets compressed up to 250 - 275 psig, and around 230 deg. F. Compressors are belt drive, 200hp at around 700 rpm, two-stage, double acting reciprocating, manufactured by Gardner-Denver. One piston for low stage, one for high stage, compression in both directions. Two steps of capacity control. Each compressor is rated at just over 4,500 lb/hr pumping rate at full design conditions.

After the compressors, a pair of heat exchangers in series reduce the gas temperature to around 40 deg. F. before it enters a a Deodorizer / Drier unit. In here, the the gas is exposed to media which dries it to a very low dew point (LESS than -100 deg. F.) and removes undesirable odors.

From here it's on to the CO2 Condenser where the gas is liquified by an ammonia cascade system operating at around -25 deg. F. The Cascade system rejects heat gained from the CO2 Recovery system into the low side of the Brewery ammonia refrigeration system, which is operating at around +20 deg. F. This is accomplished through the Cascade system condenser. The Cascade system ammonia compressor is a 200hp FES/GEA screw which is designed to operate at -28 deg. F. suction and +35 deg. F. condensing temperatures. Not quite a booster, not quite a high stage; the FES start-up guy called it a "hooster"...

Liquid from the CO2 Condenser drains into another vessel called the Stripping Tower. In the Stripper, the liquid CO2 is purified to a state classified as "beaverage grade". From here it is pumped to the storage tanks. From the storage tanks, the liquid is vaporized on demand in heat exchangers and piped to the Blending and Packaging facilities.

That's a thumbnail sketch of the process. However, as they say, the devil is in the details.

Fire away!

chillin out
07-04-2008, 12:39 AM
Nice explanation mate.
Thanks for sharing.

Chillin:):)

cmorris69
10-04-2008, 01:17 AM
I have a question which I hope has a simple answer but doesn't make me look too stupid:

When CO2 converts from a solid into a liquid within a sealed enclosure as the pressure gets high enough, does that state-change require significant latent heat input? Or is the fact that pressure has increased to the required point enough within itself to cause the reaction?

cm

Josip
10-04-2008, 10:02 PM
Hi, cmorris :)


I have a question which I hope has a simple answer but doesn't make me look too stupid:

When CO2 converts from a solid into a liquid within a sealed enclosure as the pressure gets high enough, does that state-change require significant latent heat input? Or is the fact that pressure has increased to the required point enough within itself to cause the reaction?

cm

all depend on pressure and temperature, at tripple point everything is very simple, pressure about 5 bar and temperature about -56*C and we have all three phases ... but you can see that much better here...

http://www.science.uwaterloo.ca/~cchieh/cact/c123/phasesdgm.html (http://www.science.uwaterloo.ca/%7Ecchieh/cact/c123/phasesdgm.html)
http://www.standnes.no/chemix/english/phase-diagram-co2.htm

Best regards, Josip :)

cmorris69
10-04-2008, 11:24 PM
Thanks for your reply, Josip!

So, a there is dry ice inside a sealed container at the triple point pressure and temperature, and that container is extremely well insulated so as to allow VERY LITTLE heat infiltration. Sublimation is occurring which is causing a gradual increase in pressure within the container. There is plenty of dry ice, so not all of it will "sublime" before state change occurs.

At some point, will the remaining dry ice undergo a transformation to the liquid state strictly as a result of increasing pressure, or is there a requirement that additional heat be added to the dry ice as well?

If heat WERE added in the case above, would that speed up the state-change?

Would raising the pressure by admitting CO2 gas from a high pressure source speed the state change by itself without the addition of heat?

I've must be missing something somewheres along the line!

Josip
11-04-2008, 04:35 PM
Hi, cmorris69 :)


......So, a there is dry ice inside a sealed container at the triple point pressure and temperature, and that container is extremely well insulated so as to allow VERY LITTLE heat infiltration.


.... according to theory at triple point we have all three states, the same as with water;) at 273,15K or 273,16K


Sublimation is occurring which is causing a gradual increase in pressure within the container. There is plenty of dry ice, so not all of it will "sublime" before state change occurs.

.... sublimation itself is phase change, from dry ice to gas, no liquid phase, but for sure not in one second because by sublimation we remove some heat and cool again the rest of dry ice ....


At some point, will the remaining dry ice undergo a transformation to the liquid state strictly as a result of increasing pressure, or is there a requirement that additional heat be added to the dry ice as well?
If heat WERE added in the case above, would that speed up the state-change?

take a look at diagram again....
http://www.standnes.no/chemix/images/scrshpic/phase-diagram-co2.gif

http://www.standnes.no/chemix/english/phase-diagram-co2.htm

going straight up (increasing the pressure only) there is no change of state... we must increase temperature..... about speed..... I believe it will be faster because molecules are moving faster at higher temperature;)


Would raising the pressure by admitting CO2 gas from a high pressure source speed the state change by itself without the addition of heat?

I'm afraid not ... we are keeping liquid CO2 at -34*C and 16 bar (in brewery tanks) for evaporating and reuse of gaseous CO2 you need HE usually steam type with pressure regulator ..... maybe to take that in this way ... as much energy we used to liquefy that gas that much we need to transform it to back to gas .... but maybe I am not right;)


I've must be missing something somewheres along the line!

... probably me, too;)

Using CO2 for refrigeration purposes we are trying to work with acceptable pressures and temperatures needed for low temperature use, (below 233K, above 233K ammonia is much better)... having all the time liquid or gas.... because dry ice cannot travel through the pipes;)

.....sorry about my English... I'm trying to explain that in plain language..

Best regards, Josip :)

US Iceman
11-04-2008, 04:38 PM
I'm trying to explain that in plain language..


And doing a very nice job of it.;)

cmorris69
11-04-2008, 06:14 PM
Josip:

Thank you! I finally see the error of my ways. I was looking at the chart with my eyes, but not "seeing" what would be happening to the dry ice in my example. I was missing the vertical line completely.

My concern over this matter is that during routine maintenance and repair we will have to access parts of our recovery system which contain liquid CO2. Along with personnel safety, we have to protect the equipment as well and I wanted to fully understand how the CO2 would behave when accessing the system components. Our policy is to remove liquid CO2 from the component being accessed as a liquid, then de-pressurize after the liquid is gone. Your explanation will help me to more accurately explain our proceedures to the boss.

Thank you again, sir. Extremely well said.

CM

US Iceman
11-04-2008, 07:53 PM
Eliminating the liquid is the important part. If you try to de-pressurize the system with liquid remaining the dry ice can cause the valve open to atmopshere to be blocked with solid CO2.

cmorris69
12-04-2008, 03:21 AM
US Iceman:

Exactly the point of the original question. Personnel and equipment safety, as well as down-time are primary considerations which we must take into account whenever performing service or repair on our systems. Although we have always had large quantities of liquid CO2 on-site, we've just not had that much reason to open to atmosphere parts containing the liquid. The recovery system is a different animal though, and we need to fortify our knowledge of CO2 and how it behaves.

Thanks to you and Josip for your help.

CM

US Iceman
12-04-2008, 04:43 AM
cmorris69,

I think you are wise to raise these questions. Although CO2 is an old refrigerant, it is new enough to the people who are now expected to work on it.

Add in the fact CO2 has high pressures and can turn into snow or complete solid also increases the complexity of understanding this old "new" refrigerant.

tjk2007
12-04-2008, 10:59 AM
Dear US,

The Page cannot been displayed.Can you pls help me to see the vedio.

Rgds,

TJK


Here is a link from Danfoss that shows the phase changes in CO2 as the pressure or temperature is changed.

This is a very good demonstration of the refrigerant properties for solid, liquid, and vapor.

The video is about 8 minutes long but worth the waiting period to see this.

http://www.danfoss.com/businessareas/refrigerationandairconditioning/training+and+education+material/co2+phase+changes.htm

(8.5 MB)

Samarjit Sen
12-04-2008, 12:52 PM
The valid link has been mentioned earlier in this thread. It is

http://www.danfoss.com/BusinessAreas...se+Changes.htm (http://www.danfoss.com/BusinessAreas/RefrigerationAndAirConditioning/EducationAndTraining/CO2+Phase+Changes.htm)