# Will this Hood and Bucket Scrubber work?



## Alentia (Nov 5, 2011)

After reading vast posts on this forum I have drawn a schematic for small hood (4L 10-15 oz per load) and poor's man scrubber. What do you guys think? Will it work? Will I have enough CFM to create optimal vacuum to clean NOx? Rather then using spray tower in enclosed tube, I can change NaOH solution after each load. Should I possibly reduce vacuum PVC pipe with outflow to 2"?


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## 4metals (Nov 5, 2011)

I don't think 300 cfm into the "venturi" will give you either the required 100 cfm for the 3 sq ft opening, or the power to suck the fume through the water in the scrubbing section.


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## goldsilverpro (Nov 5, 2011)

Also, from the figures I've always worked with, the nitric fumes must spend at least 9 sec in the caustic scrubber to get scrubbed - that's considering a packed column with a spray system at the top. Therefore, at an exhaust rate of 300 cfm, the scrubber volume would have to be at least 300 x 9/60 = 45 cu.ft (340 gallons). This scrubber, therefore, would be at least 3' in dia X 6.4 feet tall. In practice, I would, at least, double this volume.


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## Alentia (Nov 6, 2011)

Thank you, 4metals and GSP!

What if I change position of the fan. Fan body is made of Polypropylene. Fan made of ABS, I will have to epoxy coat it if that can work. Will it give enough suction through the water? Area of opening with 4" PVC pipe is only 1/12 sqft and hood opening 1 sft. Placing cone shaped packing into the vertical pipe should create natural shower, when fan suction will pick up bits of water from bucket, condensed water will drip down itself.
I assume exhaust rate through the water should be reduced significantly, should it?
Is there a formula to calculate how much water by how much reduces the force of the fan suction of gas/air?


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## Alentia (Nov 6, 2011)

At 15.0 °C, the viscosity of air is 1.78×10−5 kg/(m·s), 17.8 μPa.s or 1.78×10−5 Pa.s
The dynamic viscosity of water is 8.90 × 10−4 Pa·s or 8.90 × 10−3 dyn·s/cm2 or 0.890 cP at about 25 °C.
Water has a viscosity of 0.0091 poise at 25 °C, or 1 centipoise at 20 °C.

Based on the above in approximation:

Water = 0.01 Air = 0.0002

100/2 = 50 times
300cfm/50 = 6cfm of pushing water through if submerged into it. However, Fan is creating vacuum at the top of bucket and sucking NOx through the water. It will not be 6cfm obviously as gases have different properties passing though water.


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## butcher (Nov 6, 2011)

just some of my rambling on,

what if you used the exhaust air from the scrubber as inlet air after the hood as an aspirator feeding the gases that made it through the first run back into the scrubber a second run, and also helping to pull a vacuum in your fume hood to add new fume with the mix. Or just make the major portion of the gas just keep recycling back through your solution.

also maybe a small water pump to lift water caustic solution wetting a filter bead bed material the gases have to pass through.


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## samuel-a (Nov 7, 2011)




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## eeTHr (Nov 7, 2011)

Alentia---

I did try an experiment with the hood air going down into water, and bubbler holes in the end of the submerged pipe. The problem is that before starting the air flow, the water level inside the hood outlet pipe is the same as the water level in the bucket, and enough vacuum must be created to pull the water level inside the pipe down to where the bubble holes are. This creates a heavy load on the blower, and drags down the overall air flow considerably. This load is less, if the bubble holes are at a shallower level in the water.

Another experiment I tried was to merely point the hood outlet pipe directly at the water, but a half inch or so above it, eliminating the need for bubbler holes. The force of the air flow appeared to blow all the air against the surface of the water, thus forcing all the fumes into the water. A pH test after running a couple of AR evaporations indicated that most of the acid fumes were trapped in the water. I also had NaOH in the water.

I haven't had time to set up my next version, which will be directly through a shop vac, with a teflon painted impeller. This one has two filters, a typical cylindrical one, plus an optional "dust bag" insert. I will probably put a furnace filter in the fume hood, too. I'm looking for the optimum performance, at a beginner home refiners' budget. I'm finishing up some other projects, and will be able to do this one next, and will post some results and pictures when I do.

Samual's drawing looks like the basic standard configuration for anything larger.

There are a few other fume hood threads on here too, if you use the Search feature.


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## dvdczar (Nov 10, 2011)

Hello all , 
I've been reading this thread because I have intentions of building my own scrubber system , this was a previous occupation of mine. I only fabricated from the blueprint the molds for the bodies and the parts themselves then I also did the assembly of said parts, I however did not have any understanding of what exactly the scrubber did, of the gases each scrubber handled, so many different ones! Now it has been a few years since the job but I have a excellent memory of some of the components of different scrubbers from discriptions on the prints. So heres where ill raise some questions for those that know, for I do not! 

1. Would the addition of refridgeration in the media chamber be benifical to helping the oxides of nitrates condense?
2. Would the addition of Ozone in the media chamber be benifical to the scrubbing process?
3. Plumbing the scrubber to a catch basin in the hood so that the scrubber resivour can double as a liquid waste neutralizing plant with a handy elevated draining valve.

And Ive failed so see any mention of a demister which seemed common place in all the scrubbers that I built . As for media to fill the chamber go to a saltwater fish store and they sell cage media balls of polypropelene for the filter that usually is hidden under the tank, its the same media the big company we did the work for used. Some of the scrubbers were first made of polypropelene then we overlay them with fiberglass . Some of the scrubbers were, when assembled 28 feet tall and 14 foot in diameter, the smallest however was about 3ft. diameter and 6 ft. tall without legs, what I believe will be most useful to the vast majority of forum members. 

Im working on drawing up prints that I'll be glad to post with the proper resins and veil to be used, when some of those questions above are answered so that I might clairify the design before I let you guys poke holes in it....lol


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## Ardibash (Nov 15, 2011)

Here is a drawing of a scrubber I'm building pretty much same as sams design, I will also post pictures of actual scrubber.


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## Ardibash (Nov 15, 2011)

Work in progress ...


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## goldsilverpro (Nov 15, 2011)

It looks like you have a plastic welder. That looks like welding rod sticking out at the bottom right of the last photo. At one place I worked, we fabricated all of our plastic tanks, etc. We also had a long electrically heated sheet bender. Sure a lot cheaper to make your own tanks, etc. Pretty simple, too.


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## Ardibash (Nov 15, 2011)

goldsilverpro said:


> It looks like you have a plastic welder. That looks like welding rod sticking out at the bottom right of the last photo. At one place I worked, we fabricated all of our plastic tanks, etc. We also had a long electrically heated sheet bender. Sure a lot cheaper to make your own tanks, etc. Pretty simple, too.



Yeap! pretty simple, only I was having troubles locating finding the mist eliminator found it right next door to my lab, also plastic misting nozzle with high flow is really hard to get. 

.......... Long electrically heated sheet bender ........... I would kill for one right now


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## Ardibash (Nov 15, 2011)

How much do you think it's worth? (when finished)


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## samuel-a (Nov 15, 2011)

Great drawing Ardibash.

Keep us posted.


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## saadat68 (Nov 4, 2016)

Hi
Will this scrubber work ? I want to add blower and injector over the hood. I think it is better :shock:


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## UncleBenBen (Nov 4, 2016)

I dont think so. For the venturi effect to work you need a relatively unobstructed air flow across the pipe you are trying to create suction in. The scrubber tank would stop air flow and you would end up blowing the air and fumes backwards out the opening of your fume hood.


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## 4metals (Nov 4, 2016)

Saadat,

Please don't double post, you asked the same question on two threads. We prefer not to clutter up the forum with multiple posts.


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