Evaluate carbon dioxide versus nitrogen as a purge gas 2

[Idontknowit]

Hi folks

I need your advice in evaluating nitrogen against carbon dioxide as a purge gas.

It is small test rig with dimensions 2x6 meters.The purging method is based on drawing vacuum.

Also there is possibility of moisture in the system.Any tips how to eliminate this before or during the purging will be highli appreciated.I think the drawing vacuum will partly solve this problem but if there will be more water in the system...?

Thanks

Idontknowit

 

[Idontknowit]

It is very urgent!

All efforts are appreciated.

Do not hesistate to share knowledge

 

[Compositepro]

It would help to know what level of vacuum you are using and how dry you need to get. Baking the chamber is the best way to make sure it is dry. Otherwise very high vacuum for an extended time. If you have any crevices that may contain water those two methods are the only way to remove the water in a reasonable time.

 

[ash9144]

CO2 is not usually used anymore. At one time common to burn natural gas to make CO2 but that gets expensive so most discontinued that practice. Also CO2 is not inert when in the presence of water it will form carbonic acid which can lead to corrosion issues as well as interfere with your process.

 

[zdas04]

I don't think that anyone was "hesitating to share knowledge". When I first read your post I thought "man I wish this guy would state the reason for doing the purge and some piping/facility design details so that maybe someone can help him".

There are a lot of reasons for doing a purge; you may be trying to get rid of an explosive or hazardous envirionment; you my be trying to get rid of air for process start up; or you may be trying to keep the environment safe for welding. Each of these purges has different design contraints. Nitrogen, CO2, and vacuum can all have a role in any of these purges, but the end result determines the quantity and quality of each in the purge-design.

Finally, you are on a mostly free forum. The best way to get quality engineering for free is to ask your question in a way that the engineers with the knowledge that you really should be paying for find to be interesting enough to respond to--if you ask a lame or boring question many of us will just close it and forget about you.

David

 

[Idontknowit]

Many thanks to all of you for your comments.

Zdas04 I understand that it should be more information provided to get most of you,but some times I need a hint to give you more information.I will take your comments into account for my future postings and will give more details.

The reason for purging is :

*changing the gas compostion (from methane let say to ethane or butane.As i mentioned boefore it is test rig so different hydrocarnon gases are going to be used during the test.
* depressurusing and dismantling part of the equipment

The level of the vacuum is going to be down to 0,001 bar.

I attach the scheme of the rig to give more clear picture.

many thanks

Idontknowit

 

[Idontknowit]

Compositepro

The level of the vacuum is going to be down to 0,001 bar as I mentioned above the level of the dry is supposed to be quite high.

Idontknowit

 

[gr2vessels]

Idontkow..,
At your vacuum level you should know that you don't have liquid water in your chamber, only water vapour, which cannot react with CO2 to form the carbonic acid. I cannot see where the corrosion issues will become an issue, for as long as you keep the components in gas status. Obviously, things will turn quickly after you condense moisture and keep feeding the CO2. Other than that, I would say that you'll be fine for the operating conditions, purging the system with CO2. I just noticed that you didn't mention any temperature;- my comments do not apply for the low temperature applications...
cheers,
gr2vessels