Issue with scrubber

[Alentia]

We have partially build and tested first system. But there is minor issue I am trying to understand and resolve and hope for some help.

When we build the scrubber and tested it, when water was flowing in "circle" the "NOx" input was sucking air and we could feel it. However when we connected vacuum sealed reaction vessel, the water for whatever reason is rising to the gas output tubing by about 4". If we open one of the valves in the vessel water going down to scrubber container again.

When we vacuum seal the vessel again (closing valve to any of the top tubing) NOx pressure generated inside the vessel starts pushing water down and opens the drain. We have huge industrial fan and PVC piping system built, this is where the pipe is connected to.
How to resolve the issue or does it work as intended?

Should we reduce diameter of tubing #1 from 3/8 to 1/4?
Should we increase diameter of tubing #2 from 1/2 to 5/8?

 

[Alentia]

While waiting for help, I was thinking for the last 20 hours, why I have this issue. It seem like the issue is due to pressure difference, even 3 feet makes the difference.

I am thinking the solution would be to raise NOx input just above or on the same level of vessel. The pressure will equalize and there will be no water coming up the tubing. I have attached the picture of what I am thinking to change.

I hope someone can confirm or deny my theory, as I did not have time today to make such modifications. I am hoping to do it tomorrow and let you guys know.

This is the first time I am working with completely sealed reaction vessels. Very interesting observation I have made. When vessel is completely sealed (beside the NOx output to scrubber), in late stage of reaction you can not see brown fumes, everything is perfectly clear. But as soon as you give little bit of air (oxygen) go inside the container, the NOx reaction starts happening right away. I lock it again and brown fumes are gone within 10-20 seconds.

 

[qst42know]

What purpose does #1 serve? Why tie the fumes hose into the pump line at all. The fumes should feed into the bucket above the water level.

I am thinking all of the pump output should spray on the scrubber packing only, you did say you have a blower in this system.

 

[Geo]

yea, i was thinking the same. the hose from your reaction vessel should enter just below the scrubber packing and be pulled up the column or else your wasting the most effective part of the scrubber. the way you have it set up the large pipe with the spray nozzle isnt even part the system so to speak. the reason for having the wiffle balls is the fumes enter the bottom of the column and have to pass by all the area covered by your lye solution and thus neutralizing it. if the fumes never enter the column then its not being effective.

 

[butcher]

I like it,
What about an inline check valve (anti backflow valve) in the reaction vessel line, something easy for the pressure of the NOx from the reaction to overcome, a tee after this check valve could also introduce a small portion of the scrubbing fluid and introduce pumped air before it enters the scrubber.

 

[Barren Realms 007]

He has actually done kind of what 4metals has posted on. He is pulling his fumes into his scrubber by a venturi effect and then the fumes run thru the stack. About the only difference in the setup is that the pipe pulling the fumes in does not go down into scrubber solution.

 

[butcher]

That makes more sense, then should not the jet venturi aspirator educator be on top before where the water pump discharge flows into the sprayer for the scrubber?

I think I would still use two check valve's on the reaction boiling vessel, one (check valve arrow) pointing towards, or directing fumes to scrubber, and one (check valve arrow pointing towards, or directing air into vessel, when lowering the heat allowing air to enter vessel when it cools and it try's to pull into a vacuum.

Edited to add:
That PVC Tee aspirator looks home made (I am not sure of the design but from the looks in the picture, I cannot see it working that well) , I think I would spend a couple of dollars on a factory made vacuum aspirator.

 

[qst42know]

I'm with butcher. The aspirator design may be the problem.


P.S. I don't like the idea of storing 5 gallon buckets of solution on the top shelf. That seems to be an accident waiting to happen.

 

[qst42know]

I still wonder if an aspirator discharging over the packing wouldn't simplify things?

 

[Barren Realms 007]

I still wonder if an aspirator discharging over the packing wouldn't simplify things?

4metals showed his design with the pipe discarging into the solution and then going up thru the stack with the packing and sprayer.

 

[Geo]

I still wonder if an aspirator discharging over the packing wouldn't simplify things?

4metals showed his design with the pipe discarging into the solution and then going up thru the stack with the packing and sprayer.

exactly, just saying.

 

[qst42know]

I get it now.

 

[butcher]

NO nitrous oxides needs oxygen to convert to NO2 nitrous dioxide, and nitrous dioxide will dissolve into water forming nitric acid,(nitrous oxide will not normally), the caustic solution in the scrubber can convert the HNO3 to nitrate salts,

By introducing the fumes into the top of the scrubber (with a water assisted vacuum aspirator the NO2 gases would mix with water, the nitrogen gases would come into contact easy with air converting to NO2 and be absorbed by water and solution)

By introducing these fume into water bucket below the NO2 would also be absorbed the NO fumes would travel back up the scrubber into air and water stream and also be absorbed.

HCl fumes would dissolve easily into water and form chloride salts in caustic solution.

I do not see where these fume entered into the fume scrubber system would make much difference, as long as they did not leave this system as gases.
But also the lower you could have your hose from the reaction vessel the better as it can condense liquids in this hose, if you want liquids condensing to go back into solution Have hose higher allowing condensed nitric to go back into solution to do more work, if you do not want the condensed liquids to go back into reaction vessel then tube should be lower than heated reaction vessel.

 

[Alentia]

I have raised the aspirator above the vessel level and changed aspirator assembly.

Neither fixed the issue. Driving home and thinking about it finally clicked in my head. It works as indented.

Before I jump to theoretical conclusion, I would like to address concern about 5 gallon bucket with 2 aspirators on top of the shelf. The bucked is filled with very dangerous chemical, but sitting very tight up there. The chemical is known to cause death to some species in our universe. The substance is a liquid consisting of two molecules of Hydrogen and one Oxygen. :mrgreen:

Basically what is happening with the pipes:

1. Water (Lye solution) is flowing down the pipe
2. With horizontal opening it creates low pressure within such opening
3. Opening (aspirator) is connect to reaction vessel, which is vacuum sealed
4. The pressure in vessel becomes negative after less than a seconds
5. Negative pressure draws liquid back into the tubing connected to the vessel to equalize the pressure
6. Pressure in the vessel needed to rise before it can equalize with pressure in the aspirator
7. When pressure in the vessel is high enough venturi effect will work

 

[butcher]

Where is scrubber vented?
If you do not vent it pressure may build in the system and this may also slow fumes from the reaction heated vessel, the acids and bases would also create gases that can add to the pressure build up if not vented.

Edit to add after thought: if the scrubber had unreacted NO nitrous oxide gas this gasfrom the scrubber could be bubbled into a solution of water and Hydrogen peroxide to form dilute nitric in this bucket , before the fumes are being sent outside.

 

[qst42know]

Are one of the valves on the reactor head open to allow flow?

 

[Alentia]

The 4" pipe goes to the main system we have built and which ends with roof top industrial fan.

There are no vents in the vessel. They are connected to Nitric and HCl reservoirs. Opening up anything in reaction vessel instantly creates NO2 and it starts to escape at the point of lowest resistance.

 

[qst42know]

Is there a chance the shower head over the packing is robbing to much flow from the aspirator?

NOX shouldn't be able to escape if you are creating a decent vacuum.

You may still have aspirator design trouble.

 

[Alentia]

System is working great now. Moving aspirator head up made some improvements and today scrubber went to second stage (AR) of refining purging all of NO2 from vessel to vent system without any issues. I think we may say the issue is closed. When you build a scrubber and that see water is being pulled into NO2 outflow tubing, raise the tubing and create some pressure in the vessel by increasing heat and stirring. We hope to have first production of AuCl tomorrow after night run.

Next step will be to move to bigger scrubber reservoir from "test bucket".

 

[Alentia]

Finally, we had completed the build of first scrubbing system, based on mistakes and failures or previous one. The system looks cool. System accounts for water pressure and vacuum suction at different degree of pressure from the vessel.

Scrubber includes replaceable activated carbon filter above the shower head. Most of the connections are not glued, but connected using "white plumbing" teflon grease. Teflon grease allows for easy disassembly and minor tweaks when needed. Vacuum is automatically regulated by pressure in the vessel. More pressure of NOx increases water flow through venturi nozzle.


Pictures below:

1. Custom build venturi vacuum nozzle
2. Vent system
3. Complete scrubber