# Lab Hood, Ventilation & Scrubber System Design



## HigginsMechanical (Jan 11, 2012)

Hey All,

Getting very close to the assembly of my lab. I bought a fume hood, cabinets and acid resistant counter tops in an industrial auction in mid December and I am picking the equipment up after Jan. 23rd. Meanwhile, I've done a basic design for the ventilation and scrubber system. (attached as a .pdf file) Your input and thoughts are greatly appreciated.

The scrubber design is based off of an eductor powered NOx scrubber that someone posted a picture of here on the forum. I cannot remember who submitted the picture and design, nor can I readily find the post... but THANK YOU for the concept!

I decided to use a draft inducer from a condensing gas furnace with a speed controller in lieu of a eductor to draw a vacuum. I was getting pump prices from vendors of $1200- $1400 to allow for the necessary +/- 70' of head at the desired flow rate and pressure to produce the vacuum. I had a few pump professionals look at the design... Now, the pump price drops to around $300.00.

The draft inducer is made out of plastic and is rated for chemical resistance to moist acidic compounds that exist within a condensing furnace's flue gas byproducts. It will be interesting to see how long the draft inducer assembly lasts. The 2" CPVC inlet pipe from the AR hood mounts to the draft inducer assembly with a flange. The outlet of the draft inducer comes as a standard size of 2" PVC, so it fits right into a 2" CPVC male to slip fitting.

The in-line exhaust fan is Continental Fan's M# AXC300B. It is painted with epoxy so it should last. It is readily available on the internet for around $400 with tax and shipping. At a quarter of the price of a corrosion resistant fan, I can afford to go through a few of them if they only last a couple of years.

The container for the soda ash and water mixture is a white or "natural" colored 55 gallon plastic drum with graduations from Grainger. It has sealed heads and (2) 2" threaded ports. The 12" PVC duct mounting flange will have to be notched around the ports. The duct flange will be bolted with nylon fasteners and also sealed with glue.

I'm still working on a suitable tower packing material. Considering tower packing, wiffle balls, hair curlers, cut lengths of hose or tubing... we shall see.

Every motor will have a speed controller and I have several Dwyer magnehelic gauges that will be mounted to monitor pressures. I can't wait to get the system assembled and start smoke testing!

Fittings and pieces and parts have been pouring in; assembly should start shortly. I've been taking pictures to document everything an will share if anyone wants to see the progress.


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## Noxx (Jan 11, 2012)

Your setup is very similar to mine.

Thank you for planning incorporating a scrubber in your design.

You should reconsider using an eductor (water injector). LittleGiant pumps are cheap and many are corrosion resistant. I can't hardly see your draft inducer resisting to highly concentrated NOx for a while.

The design posted was by 4metals IIRC.

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=40&t=9115&p=87383&hilit=eductor#p87383

I don't like the fact that you're venting toward the ground. According to law, fume hood venting should be upwards, on the roof. No airflow restricting rain caps allowed.

At least do it upright but add some plastic mesh grille to prevent leaves/animals from entering.

Finally, I'm curious on how you're gonna seal the PVC couplings on the scrubber if you do not weld/glue them ?

Good design, congrats !


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## HigginsMechanical (Jan 11, 2012)

Noxx said:


> Your setup is very similar to mine.
> 
> You should reconsider using an eductor (water injector). LittleGiant pumps are cheap and many are corrosion resistant. I can't hardly see your draft inducer resisting to highly concentrated NOx for a while.



After some extensive inquiry with a few professional pump supply companies that we do business with, it was determined that to get the proper vacuum through an eductor, the pump would be designed for 70' of head which, makes for a very expensive pump.

Meanwhile, being a heating and air conditioning contractor, I can get those 90% efficient condensing furnace draft inducer assemblies very cheaply. 90% furnace draft inducers are all plastic, including the impeller and casing. There is no exposed metal, unlike the ones used for standard 80% efficient furnaces that vent with sheet metal stack pipe. 



Noxx said:


> The design posted was by 4metals IIRC.
> http://goldrefiningforum.com/phpBB3/viewtopic.php?f=40&t=9115&p=87383&hilit=eductor#p87383



THANK YOU!



Noxx said:


> I don't like the fact that you're venting toward the ground. According to law, fume hood venting should be upwards, on the roof. No airflow restricting rain caps allowed.



Can you quote a specific law? BOCA code (as well as Chicago Building Code) allows for j-duct venting on all types of exhaust systems. One note that I considered and you probably didn't realize- The bottom of my downturn elbow will be better than 15' above the ground. We're in a pretty tall warehouse.




Noxx said:


> Finally, I'm curious on how you're gonna seal the PVC couplings on the scrubber if you do not weld/glue them ?



Slip fittings on 12" couplings and pipe are pretty tight. If you'll notice, I am only leaving (2) joints unglued, opposite the direction of the water shower. There shouldn't be any leakage, if there is, I can seal the outer lip where the pipe meets the fitting.



Noxx said:


> Good design, congrats !



THANKS!


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## HigginsMechanical (Feb 1, 2012)

My refining lab is starting to come together. I had to wait a month before the auctioneer would be ready for us to pick up the cabinets, acid resistant counter tops and chemical fume hood. Meanwhile, all materials for the ducting and scrubber system, associated piping and equipment have been gathered... Keep in mind, I've yet to inquart and pour corn flakes for my first batch! Hopefully, everything will be ready by mid-February... Very excited!


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## Noxx (Feb 1, 2012)

Looks nice ! 8)


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## cnbarr (Feb 1, 2012)

Very nice, I'm extremely jealous of your new lab.

Nice and spacious, Congrats on the nice.


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## Smack (Feb 2, 2012)

Did you have any cabinets and counter top left or did you use it all?


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## HigginsMechanical (Feb 2, 2012)

Smack said:


> Did you have any cabinets and counter top left or did you use it all?



There are three sections left:

(1) base corner unit with top
(1) 4' sink base with double bowl sink and top and fixtures
(1) 4' base cabinet with partial top (about 16") 

You are welcome to them.... (Otherwise, they'll just sit around the warehouse forever.)


Noxx & cnbarr- Thank you for the nice comments!


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## glondor (Feb 2, 2012)

Hey Mechanical, I have said it before and will say it again, a roll of plastic snow/construction fence has got to make great packing material for a scrubber. Either rolled up tight or cut it provides a massive surface area with very little air flow restriction and it is dirt cheap. I would use the round profile type rather than the lighter flat profile type.

This type>>>> http://www.google.ca/imgres?q=construction+safety+fence&hl=en&sa=X&biw=1024&bih=677&tbm=isch&prmd=imvns&tbnid=D6bGrWr_C8KpNM:&imgrefurl=http://www.alibaba.com/product-gs/430366458/Security_Fencing.html&docid=NHPh6ZyxfV41dM&imgurl=http://i00.i.aliimg.com/img/pb/574/234/231/1259983600991_hz_myalibaba_web12_7548.jpg&w=800&h=533&ei=EQUrT7efOcSusQLP78i-Dg&zoom=1


NOT this type>>>>> http://www.google.ca/imgres?q=construction+safety+fence&hl=en&sa=X&biw=1024&bih=677&tbm=isch&prmd=imvns&tbnid=wMO_Jj8WPy5-3M:&imgrefurl=http://www.merchantcircle.com/business/Boxes.and.Bags.-.GBE.Packaging.Supplies.414-545-6636/picture/gallery%3Fstart%3D40&docid=nAYIWiqbPJ6DWM&imgurl=http://media.merchantcircle.com/29481826/safety_fence_557_medium.jpeg&w=296&h=240&ei=EQUrT7efOcSusQLP78i-Dg&zoom=1


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## HigginsMechanical (Feb 2, 2012)

glondor said:


> Hey Mechanical, I have said it before and will say it again, a roll of plastic snow/construction fence has got to make great packing material for a scrubber. Either rolled up tight or cut it provides a massive surface area with very little air flow restriction and it is dirt cheap. I would use the round profile type rather than the lighter flat profile type.
> 
> This type>>>> http://www.google.ca/imgres?q=construction+safety+fence&hl=en&sa=X&biw=1024&bih=677&tbm=isch&prmd=imvns&tbnid=D6bGrWr_C8KpNM:&imgrefurl=http://www.alibaba.com/product-gs/430366458/Security_Fencing.html&docid=NHPh6ZyxfV41dM&imgurl=http://i00.i.aliimg.com/img/pb/574/234/231/1259983600991_hz_myalibaba_web12_7548.jpg&w=800&h=533&ei=EQUrT7efOcSusQLP78i-Dg&zoom=1




Excellent idea and something to try... Thank you very much!


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## Bizness4you (Feb 3, 2012)

Is the hood ductless? looks great!!


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## Smack (Feb 3, 2012)

No it's not ductless. He still has to set that part up.


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