A gallery of home built hoods and fume scrubbers _hood_

[skinny]

View attachment 63445
Here's the inside of my hood with the scrubber I am using. Hood is 48in x 30x32. The tray in the bottom is disposable and replaceable. The hood is made from Melamine and I built it myself.

does the scrubber vacuum off the fumes directly from the beaker? sorry novice question been spending all night trying to figure them out

 

[Yggdrasil]

For small volumes that is often used.

 

[4metals]

This is a larger hood in a commercial refinery but it still demonstrates one basic method to allow the NOx to be collected and sent through the scrubber. These beakers have had the watch glasses removed because they were ready for the next step. The watch glass directs the fume from the pour spout into the pickup tube.

 

[AuggieDog]

does the scrubber vacuum off the fumes directly from the beaker? sorry novice question been spending all night trying to figure them out

Yes. If you look at that last bit of white tubing dangling free; that piece goes through a watch glass with a hole in the center that fits neatly over a 5L beaker.
The "watch glass" is a glass pot lid from the thrift store with its handle removed (like the photo), these have holes pre-drilled (find one without a vent hole like in the attachment). .

 

[4metals]

The "watch glass" is a glass pot lid from the thrift store with its handle removed (like the photo), these have holes pre-drilled (find one without a vent hole like in the attachment). .

Not exactly, a watch glass is a piece of glass that looks like a mammoth contact lens, no hole in the center. It sits atop the beaker and the pour spout on the beaker creates an opening where the fume can pass between the rim of the beaker and the watch glass. The glass encloses the rim most of the way around except for where the pour spout is. The pot lid pictured above can work if the hole allows the pick-up pipe to draw enough air. And it is placed on the beaker "upside down" from how it goes on to a pot. That allows the condensed fume to drip into the beaker.
This is a catalog cut from a glassware supplier showing a watch glass.
This is a shot of a watch glass on a beaker with an ongoing reaction.
No need to over think this concept, the watch glass sits on the beaker but it is not "sealed". I have also had PVC lids with a hose pickup made but it was overkill and you needed one for every size beaker.
simple is better in this instance.

 

[BGDOCK]

I like the flexible hoses ( looks like my CPAP hoses )do you more details on the plumbing / exhaust duct , that’s a really good idea

 

[BGDOCK]

My first hood
32” high 32” deep 48” wide
Melonite ( 43$ a sheet , two sheets)
Corian counter top (free)
Light LED ( free)
Still working on the exhaust could use some suggestions I have room on the right side
I’m running it 15’ to a 8” round roof penetration

 

[Yggdrasil]

I think I have seen similar but with upside down funnels.

 

[AuggieDog]

Actually, I was trying to say that my watch glass is a pot lid. I use the hole to feed the hose through that draws up the fumes to the scrubber.

 

[4metals]

I like the flexible hoses ( looks like my CPAP hoses )do you more details on the plumbing / exhaust duct , that’s a really good idea

available from McMaster Carr, I have been using this 1 1/4" hose on setups for years and it holds up exceptionally well. HERE

 

[BGDOCK]

Thanks m familiar w/ that big catalog , I love looking through it
Do you run a scrubber system and a seperate exhaust

CFM requirements for hood

Face dimension x 100 \ 144 = CFM requirements
33x48x100/144=1066 CFM required
Edited for clarity

 

[BGDOCK]

So I have a couple of questions about this scrubber set up .
1.) Can I start off with just two 5L flasks ( one w/ peroxide and an empty one ) to start off , four 5L flask are 200 $ plus
2.) using an Eductor System McMaster Carr valve 600$ plus ( wife would shoot me) it uses a 8g/min valve . I was thinking of using a submersible pump for the water side possibly little giant pump in a 10-15 gallon container.
Any suggestions or ideas on an affordable educator valve ?

 

[4metals]

Any suggestions or ideas on an affordable educator valve ?

https://flexpvc.com/cart/agora.cgi?p=PVC-Venturi-Tees&p_id=473-825&xm=on&ppinc=detail

flexpvc's venturi's are inexpensive. Put your money into a good corrosion resistant pump

I used the 4 liter vac flasks because I got them for nothing. One of the benefits of being in the refining consulting business. If I were doing it like so many other members I would use 6" PVC rigid pipe with appropriate caps and piping.

 

[Shark]

I have bought a fair bit of glassware from here Tennessee Labware

They keep limited supplies on hand at times so ask when they may have what you may need. I haven’t ordered online but have been in their shop a few times. Seems like decent people to work with.

They don’t have the educator but you might ask to make sure.

 

[4metals]

I drew this up for making the scrubber out of PVC.


If you want I can make up a similar drawing for the vacuum by venturi setup

 

[Shark]

I like the way the ports are on the side, it keeps the cap from dripping when servicing them. Very nice touch.

 

[4metals]

This is the configuration for the venturi powered off a reservoir and pump. Since this is drawing water through your scrubbers it is always possible you will overpower the chemistry in the tubes (by not checking it daily and making additions) and some NOx will enter the reservoir. Emptying a bag of marble chips into the reservoir base is not a bad idea. The vent for the vacuum ties into your fugitive exhaust and any odors will be drawn away. For a small setup the vacuum can be dual purpose as it will also provide suction for vacuum filtration, just not when you are using it to scrub NOx fumes.
The venturi's from flexpvc.com are inexpensive and they have a detailed tutorial to determine sizing. For a scrubber this size (3 tubes) a 10 CFM flow will work fine.

 

[4metals]

And all together it would look like this.


I would connect the piping between the tubes with clear heavy vinyl tubing so you can see if red NOx passes over. (telling you to check your scrubber chemistry)

The tubes are filled 90% of their volume with tower packing like bio balls or something similar.

 

[skinny]

i found a few things i wanted to run by you after studying your drawing for a minute i found a circulating vacuum pump that basically does what you have illustrated but what i didnt see on the machine or in any reference was how to apply something to take care of the fugitive fumes the scrubbers miss im guessing thats the blue vent in your diagram? i also found these gas scrubber glass pieces and some medium i was hoping you could evaluate the setup and let me know how to construct it and what else i might need ill use caustic lie and water in one scrubber and hydrogen peroxide and water in the second with the third being empty

 

[4metals]

The machine you showed is basically the same venturi setup but I notice it has brass fittings. Sooner or later your chemistry will run down and corrosive fumes will get to your vacuum generator. The one you show is not vented because it is meant to pull vacuum for laboratory experiments and apparently they don't worry about corrosion. It may last for many years but as far as corrosion goes, refiners see a lot of it. But the reason I vent the one I showed is in the event that your chemistry is consumed you are covered. I said as much in the text box. But the emissions that pass thru the scrubber are considered scrubbed emissions as the flow rate and chemistry in the scrub tubes takes care of the NOx.

Fugitive emissions are fumes that never make it to the scrubber, it's the whisp of fume when you open a bottle of acid or when you remove a watch glass. They are removed with your general exhaust blower. Once a reaction is running and the exhaust pickup is set the worst of the fumes go through the scrubber.

You can do your reactions in a sealed reactor and connect the vessel directly to the scrubber if you use something like this. These sealed reactors like this 2 liter reactor will handle a dissolve of about 9 1/2 ounces while maintaining a safe reaction chemical rise. But when you fill the vessel, or empty it to filter it or transfer solutions you will still have fugitive emissions.