Sciencemadness Discussion Board

how to pump nitric acid?

Ubya - 18-6-2020 at 17:52

i'm trying to build a new apparatus for the home production of nitric acid, and part of the process is absorbing the gas in water.
i could use the classic boubbler, but i would need multiple stages to reoxidize any NO formed, a youtuber did it, but i won't be able to generate much pressure to force the gas and an excess of air through multiple wash bottles.
my other option as an absorbtion column, and i want to try this.

i want to trickle the dilute acid from the top of the column while the feed NO2/Air is at the bottom, and pump back at the top the acid in the receiver at the bottom of the column.
what pump could survive this?
my first thought is a peristaltic pump with a flexible teflon tubing, the issue is i can't find someone that sells to privates, or that sells small quantities, i don't need $1000 worth of teflon tubing, i just need the 15cm or so for the pump, and use standard teflon tubing for the rest.

the other idea i had is an all aluminium piston pump. aluminium IIRC is not attacked by nitric acid thanks to its oxide layer, but this might be a hard thing to pull off for cheap.

any ideas/suggestions/tips?

ahill - 18-6-2020 at 19:28

Suck the NO/air thru the bubblers Instead of pushing it.

Sulaiman - 18-6-2020 at 20:00

I think that ptfe tubing may be too rigid for a peristaltic pump,
Viton tubing may suit your purposes,
e. g. cnviton.com

Eddie Current - 18-6-2020 at 21:28

Tygon tubing isn't cheap, but it will do the job.

https://www.welco.net/dcms_media/other/05.Chemical_Resistanc...

Refinery - 19-6-2020 at 01:07

I used simply manual charge and gravity feed for cryogenic coolant. The flowrate was so low that 10 liter reserve had to be recharged only every 3 hours.

mackolol - 19-6-2020 at 04:30

As for the aluminium, NO2 dissolved in water will corrode it quite significantly. Not all of the NO2 reacts with water, some of it just dissolves.
And for teflon tubing, I bought it in some brewing shop. It wasn't expensive and does perfect job through all of my chemistry years, but it isn't very flexible...

[Edited on 19-6-2020 by mackolol]

Ubya - 19-6-2020 at 05:00
Quote:

Suck the NO/air thru the bubblers Instead of pushing it.


my aspirator pump is really loud, and i care a bit too much about my rotary vane pump, then again, i'm trying to do something different from a multi stage absorbtion system
Quote:

I think that ptfe tubing may be too rigid for a peristaltic pump, Viton tubing may suit your purposes, e. g. cnviton.com

yeah teflon tubing is rigid, my pla was to use a flexible tubing for the pump, and then rigid teflon tubing to connect the pump to the glassware (this way i need only a few centimeters of flexible acid resistant tubing, instead of 1.5m)
Quote:

I used simply manual charge and gravity feed for cryogenic coolant. The flowrate was so low that 10 liter reserve had to be recharged only every 3 hours.


eh, i'm not aiming for a small scale nitric acid plant, more like 1L every now and then (NA is still hard to find and expensive here, i could make 1L for maybe 3 euros with this method though)
Quote:

As for the aluminium, NO2 dissolved in water will corrode it quite significantly. Not all of the NO2 reacts with water, some of it just dissolves. And for teflon tubing, I bought it in some brewing shop. It wasn't expensive and does perfect job through all of my chemistry years, but it isn't very flexible...

bye bye aluminium pump idea

ok so now i need to find someone that sells viton or tygon tubings to privates and not in bulk

monolithic - 19-6-2020 at 14:00

Venturi pump if you have access to compressed air but it's not going to be quiet or clean. Industrially this easily handled with PTFE double diaphragm pumps but that's supremely overkill for 1 liter of fluid.

RedDwarf - 19-6-2020 at 14:15

No idea if this is the flexibility or diameter that you need for your peristalic pump but might be worth pursuing further: https://www.ebay.co.uk/itm/VITON-RUBBER-TUBE-3-2MMID-X-6-2MM...

Ubya - 19-6-2020 at 14:43
Quote:

Venturi pump if you have access to compressed air but it's not going to be quiet or clean. Industrially this easily handled with PTFE double diaphragm pumps but that's supremely overkill for 1 liter of fluid.


sadly no compressed air, but even if i did have it i think this kind of pump would mess up with the flow as it would push more air from the top, while i want the gas to raise from the bottom of the column.
Quote:

No idea if this is the flexibility or diameter that you need for your peristalic pump but might be worth pursuing further: https://www.ebay.co.uk/itm/VITON-RUBBER-TUBE-3-2MMID-X-6-2MM...


thanks a lot! i'm looking on ebay many listings, just tryiing to find the best deal.
i also tried searching for tygon, but apparently there are many grades, and some resist acids better than others, i can only find generic tygon for fuel lines or the specific acid resistant one, but in bulk sizes

SWIM - 20-6-2020 at 11:06

If your apparatus can hold a bit of positive pressure it might be possible to circulate the liquid without a pump.

Okay, I know this will sound a bit goofy, and probably isn't the smart solution, but picture that the liquid and gas from the absorption tower are both led into an Erlenmeyer flask through 2 holes in the stopper, and the third hole in the stopper has a vertical glass tube that dips to nearly the bottom of the flask.

Both the liquid, and the larger volume of gas, will be forced up the tube.
This will probably happen in a slurping, bubbling way that results in drops of liquid being forced up the tube by the gas pressure with considerable gas between them.

At the top, this tube is bent over so it empties into an addition funnel.
The addition funnel has a vent tube out the top to let the gas out, and the drip tip at the bottom runs the liquid back into the top of the tower.

Yes, the tower is under slightly increased pressure, but this is produced by a column consisting of mostly gas with drops of liquid spaced out in the rising tube, and it has less weight per unit of height than the solid but shorter column of liquid in the addition funnel forcing its way into the top of the gas tower.

So this idea is certainly a long-shot and probably not worth the effort when there are acid proof pumps out there, but it would be an interesting apparatus if it worked.

The liquid bubbling and rising, the gas absorbing, If you ran it out on the porch you'd probably have stoned people showing up to stare at it like an unusually toxic and corrosive lava lamp.




Ubya - 20-6-2020 at 16:34

Quote: Originally posted by SWIM  
If your apparatus can hold a bit of positive pressure it might be possible to circulate the liquid without a pump.

Okay, I know this will sound a bit goofy, and probably isn't the smart solution, but picture that the liquid and gas from the absorption tower are both led into an Erlenmeyer flask through 2 holes in the stopper, and the third hole in the stopper has a vertical glass tube that dips to nearly the bottom of the flask.

Both the liquid, and the larger volume of gas, will be forced up the tube.
This will probably happen in a slurping, bubbling way that results in drops of liquid being forced up the tube by the gas pressure with considerable gas between them.

At the top, this tube is bent over so it empties into an addition funnel.
The addition funnel has a vent tube out the top to let the gas out, and the drip tip at the bottom runs the liquid back into the top of the tower.

Yes, the tower is under slightly increased pressure, but this is produced by a column consisting of mostly gas with drops of liquid spaced out in the rising tube, and it has less weight per unit of height than the solid but shorter column of liquid in the addition funnel forcing its way into the top of the gas tower.

So this idea is certainly a long-shot and probably not worth the effort when there are acid proof pumps out there, but it would be an interesting apparatus if it worked.

The liquid bubbling and rising, the gas absorbing, If you ran it out on the porch you'd probably have stoned people showing up to stare at it like an unusually toxic and corrosive lava lamp.







eh as you described it, it wouldn't work, no liquid is going to flow from the funnel as the pressure of the system is higher and the funnel is open to the air (same thing as when you open the stopcock on an addition funnel and forget to remove the cap, liquid won't flow).
maybe an airlift pump but the head is too high for a small flow of air

flaminglasrswrd - 21-6-2020 at 12:56

Viton comes in a soft variety that is suitable for peristaltic pumps. But there are cheaper Tygon varieties based on PVC that will work for nitric acid.

In either case, you should consider the peristaltic pump tubing as a consumable.

A glass syringe pump would work as well. It would last forever, but be more expensive upfront. There are some DIY versions out there that are fairly cheap.

May I ask how you are producing your NO? Plasma?

Ubya - 21-6-2020 at 15:42

Quote: Originally posted by flaminglasrswrd  
Viton comes in a soft variety that is suitable for peristaltic pumps. But there are cheaper Tygon varieties based on PVC that will work for nitric acid.

In either case, you should consider the peristaltic pump tubing as a consumable.

A glass syringe pump would work as well. It would last forever, but be more expensive upfront. There are some DIY versions out there that are fairly cheap.


i thought about a glass syringe, but it also need check valves, and those also must survive the acid.
Quote:

May I ask how you are producing your NO? Plasma?

Nope, thermal decomposition of calcium nitrate fertilizer, it is cheap when bought in bulk, and you don't even need sulphuric acid

Heptylene - 21-6-2020 at 23:22

Shameless plug of my own abosrption column.
I used an "IWAKI" type pump. Actually a chinese copycat, model number is MP-6RZ bought on aliexpress.

The pump head is polypropylene, so chemically resistant. It is not self-priming! It must be full of liquid to start, it doesn't suck air and draw liquid through the inlet.

[Edited on 22-6-2020 by Heptylene]

flaminglasrswrd - 22-6-2020 at 10:30

Quote: Originally posted by Ubya  
thermal decomposition of calcium nitrate fertilizer


Ahhh. Nice. I might have to look into that.

I bought 5lbs of "calcium nitrate" for hydroponic use a while ago. I didn't realize that it was actually calcium ammonium nitrate. It should still work, albeit at lower conversion.
Quote: Originally posted by Ubya  
but it also need check valves


Maybe a tesla valve would work well here. The pumping cost is negligible so a little inefficiency might be worth the long life?

You could also just try some cheap aquarium check valves. They might be constructed with nitric resistant plastic, a lot of plastics are. Who knows?
Quote: Originally posted by Heptylene  

Shameless plug of my own abosrption column.


Nicely done! Have you looked at ozone injection?

[Edited on 22-6-2020 by flaminglasrswrd]

densest - 22-6-2020 at 10:52

One way valves made with thin Teflon flaps are feasible. It's flexible enough for that.
I have a diaphragm pump made entirely of Teflon & other fluoroplastics.

In your case the devil is in the details. How concentrated will the acid be and how much dissolved NO2?
Polypropylene will work for a while but degrades.
Other than fluoroplastics you should consider anything organic as a consumable.

For concentrated or hot acid I don't know oof any tubing which would work in a peristaltic pump. THe compression and stretching would force the acid into any crack rapidly eating through.

Viton, EDPM, and Kalrez are possible. Under 3M and under 70C you have a lot of choices for tubing.
Butyl rubber is mentioned on some charts.

Heptylene - 22-6-2020 at 11:24

Quote: Originally posted by flaminglasrswrd  


Nicely done! Have you looked at ozone injection?

[Edited on 22-6-2020 by flaminglasrswrd]


Thank you!

No I never thought about that, but it sounds interesting! I'll try when whenever I've repaired my tube furnace. I had considered running the absorption tower on dilute hydrogen peroxide though, considering it is much more available than nitric acid. Anyways, I don't want to hijack this thread...

Ubya - 22-6-2020 at 15:29

Quote:
I bought 5lbs of "calcium nitrate" for hydroponic use a while ago. I didn't realize that it was actually calcium ammonium nitrate. It should still work, albeit at lower conversion.

i have the same mixed salt, it works, but ammonium nitrate also decomposes to N2O, and in small quantities into ammonia and nitric acid that combine again in cooler parts forming a white smoke (i have already done a few small scale experiments). My plan is to add some lime (super cheap) and convert all the ammonium nitrate to calcium nitrate and ammonia, it is another step that is going to take some days (filtering, evaporating the water and then drying the salt)
Quote:

Maybe a tesla valve would work well here. The pumping cost is negligible so a little inefficiency might be worth the long life?


mh tesla valves don't work that well with low speed fluids

[Edited on 22-6-2020 by Ubya]