retention time calculation

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saadat68

Well-known member
Joined
Aug 7, 2016
Messages
482
Hi
I searched many in forum but couldn't understand how to calculate retention time ( Need formula ) :oops:

For example we have 3 columns for vacuum scrubber.
columns diameter: 3.5 inch
columns height: 40 inch
packed columns height: 35 inch
vacuum pump: 3 CFM

Need another parameter ?
 
saadat68 said:
Hi
I searched many in forum but couldn't understand how to calculate retention time ( Need formula ) :oops:

For example we have 3 columns for vacuum scrubber.
columns diameter: 0.35 inch
columns height: 40 inch
packed columns height: 35 inch
vacuum pump: 3 CFM

Need another parameter ?
Click to expand...
You sure the column diameter is only .35"? Not 3.5"?
 
Sorry. I work with metric system here
3.5 inch is correct

They are just example. I need to know how to calculate rention time. Couldn't find any reference in forum. Just an excel file from 4metal
 
Retention time of what ?
What solvent (if any) ?
What is the column packed with ?

Sounds like a chromatography column to me.

If it is, then it would be better to ask on a Chemistry forum.
 
aga said:
Retention time of what ?
What solvent (if any) ?
What is the column packed with ?

Sounds like a chromatography column to me.

If it is, then it would be better to ask on a Chemistry forum.
Click to expand...
Hi
A vacuum scrubber for NOx
packed with bioball for example
 
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=40&t=24788&p=262177&hilit=scrubber+seconds#p262177
 
saadat68 said:
Hi
I searched many in forum but couldn't understand how to calculate retention time ( Need formula ) :oops:

For example we have 3 columns for vacuum scrubber.
columns diameter: 3.5 inch
columns height: 40 inch
packed columns height: 35 inch
vacuum pump: 3 CFM

Need another parameter ?
Click to expand...
Disregarding the packing, the total volume of the columns is (3.5/2)2 X pi X 40 X 3 = 1155 in3
That is 1155/1728 = .67 ft3
The 3CFM would do 3/.67 = 4.48 turnovers per minute.
A turnover, the theoretical time it would take for a gaseous molecule to travel from one end to the other, entrance to exit, would be 60/4.48 = 13.4 sec. This, to me, is the retention time.

The packing will increase this somewhat and, at the same time, it will decrease the volume. There are lots of variables in the packing and I would shy away from putting a number on it.

Depending on who you talk to, the required retention time for an insoluble NO molecule to find an oxygen molecule, react with it, and produce the required soluble NO2 molecule is 8 or 9 sec. Therefore, 13.4 sec should be quite adequate.
 
Understood

Thank you

Can I add 4 or 5 columns instead of 3 columns ? :shock:
I like to design smaller columns. it is safer
 
Uuum. Sorry.

The use as an NOx scrubber was not immediately obvious (to me at least).

Bubbling NO/NO2/NO3 into an NaOH solution works, giving sodium nitrite/nitrate.
The NaNO2 oxidies in air so you end up with all NaNO3, given enough time.
Just evaporate off enough water, allow to cool and nice crystals form.

Personally i feel that if a process produces a lot of something Nasty, better to capture it and make into a safe and useful by-product rather than just throw it away.

Better to not produce the Nasty in the first place, but heigh-ho. Needs must !

Edit:

By capturing the NOx and making sodium nitrate, it can be dried (sun or oven) then distilled with concentrated sulphuric acid to get near 100% pure nitric acid, which could be put back into the gold process, free of almost all contaminants that come with shop-bought nitric acid.

Final waste product of doing that is sodium sulphate, aka Glaubers' Salt : a laxative, amongst other things.
Very safe environmentally and does not smell.
 
aga
Thanks for information

Palladium
Thanks but 4metal does not explain complete in his post and I couldn't understand last section. Now I can

First want to make a scrubber with 5 columns 8) each one 20 inch
 
Aga

Welcome to the world of refining where the world of theoretical chemistry takes a few serious knocks mate. We're lucky to have some extremely good chemists on the site who also have a deep practical knowledge of refining, and some very good refiners who understand the chemistry they need to refine.


Jon
 
If making nitric was the end goal with scrubbing your fumes, why even go with NaOH, when you could just bubble the NOx through H2O2?

If it was from an AR reaction, you may want an empty vessel first to catch metal slimes that make their way through, but after the empty, you could have h2o2
 
anachronism said:
Welcome to the world of refining where the world of theoretical chemistry takes a few serious knocks mate.
Click to expand...
Chemistry is Chemistry. No magic at all no matter where it is used.

What works works.

All depends on what the word 'works' means.
(please see below)

Topher_osAUrus said:
you could just bubble the NOx through H2O2?
Click to expand...
Maybe you could, i could not.

30% H2O2 is prohibited here, so it'd end up cheaper to go the NaOH to sodium nitrate & sulphuric acid route to recover nearly pure nitric acid than to use H2O2 in a scrubber.

With even 30% H2O2 and perfect scrubbing efficiency, there's still that 70% water in there, making very dilute nitric acid. Useless (for gold dissolution).

I appreciate that i know absolutely jack shit about the actual ins and outs of metal refinery, also that i will screw it up a Lot due to lack of experience in this Art, and will appreciate any help.

The Art is in Knowing what to do and when, which i certainly do not know, having no experience at actually Doing it.

Sadly, for me, i was not born knowing everything, so have to learn it all, usually the hard way.

All Great fun though !
 
aga said:
anachronism said:
Welcome to the world of refining where the world of theoretical chemistry takes a few serious knocks mate.
Click to expand...
Chemistry is Chemistry. No magic at all no matter where it is used.

What works works.

Yep the difference being the practical chemistry of refining vs the theoretical chemistry of the text book.


I appreciate that i know absolutely jack crap about the actual ins and outs of metal refinery, also that i will screw it up a Lot due to lack of experience in this Art, and will appreciate any help.

Oh we've all done that, and still do.

The Art is in Knowing what to do and when, which i certainly do not know, having no experience at actually Doing it.

Sadly, for me, i was not born knowing everything, so have to learn it all, usually the hard way.

Oh you're going to have such an interesting ride on this train then mate.

All Great fun though !
Click to expand...
 
anachronism said:
Oh you're going to have such an interesting ride on this train then mate.
Click to expand...
Probably so.Looking forward to finding out !

Platdigger said:
Well, 30 percent nitric is very useful. Both for silver and gold, and or base metals dissolution.
Of course by adding hcl for gold.
Click to expand...
Please expain that nonsense.

Topher_osAUrus said:
Well, the 3% h2o2 will create stronger than 30% nitric, as evening bubbling no2 through water will create some nitric acid.
Click to expand...
Please explain How 3% of one magically makes 30% of the other.

Are you a Banker ?

This is all starting to feel very very familar.

I just want to have some fun with trying to refine Gold, screw it up (inevitebly), then ask questions, try again and then maybe get better results next time.

As for Chemistry, i got sober for a couple of weeks 3 years ago, got interested and done/learnt a lot since then.
No PhD here, just an Amateur Chemist amongst many other interests, including precious metals, like Gold.

You know it ? The kinda yellow and Shiny one. The Nice one that shines. That one. Gold.
 
I simply meant that 3% you can get at the pharmacy is perfectly fine, as the water itself gets partially converted to hno3 by the no2 gas. The h2o2 just aides the conversion some. But, i believe retention time of the gas plays a large factor for conversion too.

There are many threads here where people, including myself, have made nitric at home with this methodology.
Butcher has some of the bests posts on it.

And 30% is fine, because silver itself won't readily dissolve in azeotrope nitric, and it needs the h2o to help it kick off the dissolution. Something about the magical H+ ion...
When we dissolve sterling, we mix 50/50 nitric with distilled h2o. And when making ar, some choose to add water so silver chloride doesnt easily stay in solution and have to be diluted out later.. Or if we are separating gold from platinum, we can use cold dilute ar to only dissolve the gold.
And other reasons

Edit to finish
 
Thank you for a clear reply Topher_osAUrus.

Yes, how it all Actually works is still not perfectly understood by anybody.

Water does indeed have a mysterious role in many reactions.

The current thinking is that it's not lone protons (H+) but H3O+ thingies.
What difference that makes is also not really understood.

People Experienced with specific materials, such as yourself, have a very large advantage over those (like me) who think they Know something, never having had that specific experience.

I stand corrected and grateful.

Oh ! Happy New Year !
 
Dont mention it.

I learned from the great people at this forum, and without this site. I would know next to nothing.

Be sure to check out the library here, as it holds the best of the best threads. And download Miss Hoke's book, as it is the bible of refining. It was written for everybody, so someone with a chemistry background such as yourself will pick up on its information quite quickly.

Happy newyear to you as well!
Cant wait to see your first :G
 

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