# Finish my hood and scrubber design



## jeneje (Jan 17, 2013)

Hello all, I have researched the forum for a several days, and this is the design i have decided on for the hood and scrubber in my new workshop. I have incorporated the basics of 4metals design and others here, reviewing all the information I could find. I think I have covered most everything…but there are always room for improvement. I have attached a drawing I would like input on and suggestions please.

The hood size is 64” long 30” deep and 30” high made out of ¾” plywood coat with epoxy paint.

The bottom will have ¼” Plexiglas for the work area. 

One four foot light encased in glass to lite the hood. 

I have added a solid baffle at the back 6” from the back wall and 2” from each side and 3” up from the bottom.

In the center I am using a 4” inline exhaust fan with a blast gate connected to a 4”Y.

In front of the solid baffle, I am running a 1 ½” schedule 40 pvc pipe. Connecting 4 drops with y’s spaced ever 8” Connected to the Y’s at the bottom is a reducer - reducing the drops to ½” for connection of reaction hoses. 

The front will have two ¼” sliding Plexiglas doors.

To help push the air through the 1 ½” pipe to the scrubber I will us a squirrel fan drawing air from the room as the inline fan draws from the exhaust side. I think with the right regulation of air flow, by using ball valves, I should be able to control the flow rate and retention time for scrubbing before exhausting to the outside.

The scrubber is a 55 gallon open top plastic barrel 22” in diameter inside and 46” tall. 

Scrubbing solution is NaOH - this will be spayed through a 360% nozzle placed at top. The solution will be passed through a water filter hooked up to remove any settlement picked up off the packing.

The packing will be a mixture of ping pong balls, PVC pipes cut into shards, and wiffle balls.

Above the spray nozzle is the 4” PVC exhaust to the inline blower. 

At the bottom of the scrubber I am installing a 2” drain with a trap and cleanout.

Thanks
Ken


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## Jimmy (Jan 18, 2013)

Personally, I think yoou need much bigger fans.
I dont know anything abuut the process .
Generally a fume hood requires a minimum of 80 ft per minute of face velocity.
So you would need around 1000 CFM minum of exhaust air and slightly more fresh air.
A squirll cage fan wont provide enough pressure to push any air thru those small pipes. You need a radial blade fan.


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## jeneje (Jan 18, 2013)

Jimmy said:



> Personally, I think yoou need much bigger fans.
> I dont know anything abuut the process .
> Generally a fume hood requires a minimum of 80 ft per minute of face velocity.
> So you would need around 1000 CFM minum of exhaust air and slightly more fresh air.
> A squirll cage fan wont provide enough pressure to push any air thru those small pipes. You need a radial blade fan.



Thanks Jimmy, i will check into the radial fans.
Ken


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## jeneje (Jan 22, 2013)

Here are a few pics of the hood, it's coming along slowly, Next is to install the piping for the drops to the reaction vessels.
Ken


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## jeneje (Jan 29, 2013)

Update on hood, I got my blowers installed today, cut out and hung the doors on the bottom of the cabinet, got the pipeing installed inside the hood and run the pipeing to scrubber, I am hopeing to get the scrubbing solution barrel hooked up tommorow, still have to run the electrical conduit for the wires. I temped the wires today to check the lights and blowers. 

It coming along slowly but it will be worth it when finished.
I am still not sure on the size of holes to make in the grate that will hold the packing. I am using 1/4" plexiglas, i am thinking about using 3/16" but not sure yet. 

Comment welcome
Ken


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## butcher (Jan 29, 2013)

jeneje,

This is really looking nice.

The barrel scrubber may need a better shelf support.

The tool boxes in the lab, and your hat in the hood, :lol: beside that, I do not see anything wrong, nice job, vey well thought out, and good craftsmanship, in building it, thanks for sharing.

please do keep showing us pictures of this as it progresses.


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## jeneje (Jan 29, 2013)

butcher said:


> jeneje,
> 
> This is really looking nice.
> 
> ...



Thanks Butcher, I still have alot to do, and yeah i am going to put a piece of 3/4 plywood under the scrubber shelf and install some shelfs on the left side for storage as well as above the hood. I am also building a 12"x24" plexiglas hood that will set inside the main hood to use as a AR exhaust. Its going to connect to one of the drops.

My hat was tied - needed to take a break :lol: I will post more pics as the project comes along. 

Thanks again
Ken


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## Noxx (Feb 2, 2013)

The thing is, squirrel fans are unable to generate appreciable amounts of air pressure. They have a lot of CFM but at only a few in. H2O.

Also, by ball valve, do you mean a check valve ?


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## FrugalRefiner (Feb 2, 2013)

Noxx,

A ball valve, aka a quarter turn valve.

Dave


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## jeneje (Feb 2, 2013)

Noxx, you are correct about the squirrel fan, inside the hood i ran 1 1/2" pipe for my drops. What i found doing this is plenty of air with no suction through the Y,s. After thinking about this and researching on vacuum, I done some tests using another piece of smaller pipe - placing it inside the 1 1/2" Y from the bottom creating a baffle effect. By doing this it creates a vacuum around the inside tube.

The prolbem with this is you can only use one drop at a time which sucks if you need to do more then one reaction at a time. The main exhaust is a 4" high pressure vacuum inline blower which works great and can remove any fumes inside the hood, but i would prefer to use drops.

I am now looking at getting a high pressure blower for the 1 1/2" later on - but to get started with some material i have I may have to use the main exhaust.

The ball valves I decided to not use because i was using unions, i also installed a water filtering system for the scrubbing solution to remove any fine particles that may be pulled through.

I have my system all together and tested it last night. Had a few leaks in my plumbing :lol: got them fixed,forget to put on the tefkon tape :roll: :lol: .

I done a air test by burning paper and watching the smoke and it cleared out great with the main blower, seem like i have plenty of negtive pressure inside the hood.

The real test will be with a process and i hope - weather premitting next week. I still have some finial things to do as far as painting, finishing the cabniets and a few odds and ins.

I will post more pics as it gets closer to being completed

Thanks
Ken


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## jeneje (Feb 11, 2013)

Hey guys, almost there, I built my mini hood today and finished the painting. I uploaded a few more pics, i also added a new work station on the left side of room for my filtering and testing.

Just a few more days and it will be complete and ready for processing my goodies. :mrgreen: 
Ken


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## etack (Feb 12, 2013)

jeneje said:


> I done a air test by burning paper and watching the smoke and it cleared out great with the main blower, seem like i have plenty of negtive pressure inside the hood.
> 
> The real test will be with a process and i hope - weather premitting next week. I still have some finial things to do as far as painting, finishing the cabniets and a few odds and ins.



You could make some smoke bombs and try it out. sodium/potassium nitrate and sugar. Just heat it together till the sugar caramelizes and let it cool. then light it up. careful it will catch fire quick with a flame.

This is the video that I used. if your system can take care of the smoke you're all good.

http://video.about.com/chemistry/How-to-Make-a-Smoke-Bomb.htm


Eric


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## etack (Feb 12, 2013)

You do great work. I will have to hire someone to make me one like that. 

I use an old wash sink turned on its side and some plexiglass glued to the front. It works just really small. 

Eric


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## jeneje (Feb 13, 2013)

etack said:


> You do great work. I will have to hire someone to make me one like that.
> 
> I use an old wash sink turned on its side and some plexiglass glued to the front. It works just really small.
> 
> Eric


Thanks Eric, it has been a long project but i am looking forward to trying it on gold. I put everything back in it yesterday and its starting to look like a lab somewhat now.

I don't think i will use the smoke bomb :lol: for testig but will play with making them for fun :lol: though.

Thanks
Ken


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## jeneje (Feb 14, 2013)

Well, i guess i done now for awhile. I run my tests and everything seems to work good. I started 47 grams of gold last night in HNO3 to remove base metals and the hood and scrubber done its job. When it warms up i going to paint the walls,celing and hang my door to hide the scrubber, but i'm in know hurry.

Here is a few more pics and i got to try out my vacuum setup and i like it. It seems to work well for my needs.

I want thank everybody that has posted things on how to build a hood and scrubber system i took alot of there ideals and added a few of mine and it all came out good.

Ken


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## Palladium (Feb 14, 2013)

Looks good! Only thing i would question is where is the exhaust from your vacuum pump exhausting to?


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## jeneje (Feb 14, 2013)

Palladium said:


> Looks good! Only thing i would question is where is the exhaust from your vacuum pump exhausting to?



Palladium, i am now lost, please explain, are you talking about the air that comes from the other side of the pump or the solution i am filtering?

Thanks
Ken


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## butcher (Feb 14, 2013)

Very nice lab, I really like it, you have done a great job. 
Thank you for showing us the pictures and progress of your work on this project.

I would look at having a small sink or eye wash station, at least a water hose with a valve just outside the door easy to get to.


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## philddreamer (Feb 14, 2013)

Very nice, Ken! 8) 

Do a "check" on safety; and spill control... A bucket of fresh water, like Butcher suggested in case of a splash... 
On my tables, a I have a dam to keep any spills from finding their way to the floor. 
Your respirator, when not been used, should be in a container, so to keep it from been exposed to the ambient, thus the cartridges lasting longer.
Just little things that can save you "headaches" later on.
I'm remodeling mine, and I picked a few good tips from your project.
Just my 2 centavos. 
Thanks!
Phil


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## Palladium (Feb 14, 2013)

What ever air the pump pulls from the flask it will exhaust from the pump back into the room. This includes So2 gas, nitric fumes, and hcl fumes. This also will include oil mist which will coat everything around your shop in a thin film of oil. You also need a back flow preventer ( check valve ) to stop oil being sucked from the pump back up through the hose when the pump is off and the flask is under vacuum. I use a check valve from walmart made for fish aquariums. It lasts about 6-8 months and needs replacing. http://www.walmart.com/ip/Aqua-Culture-Check-Aquarium-Valve-1-ct/10536141 Also if your using coffee filters under vacuum your are going to have a lot of fine particulate make it's way through. I mounted my pump outside my room and run the hose to my flask. Hose is cheap. Run you a wire and install a light switch to turn it off and on with. Cost about $2.00 at Lowes for the plastic work box and a light switch with cover plate.


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## Palladium (Feb 14, 2013)

Also, Cardboard is you friend around the filter area. You will have spits and spats that jump everywhere no matter how careful you are. Let's not even mention a spill. These are not as easily wiped up as they are caught and trapped on cardboard for later recovery.


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## jeneje (Feb 14, 2013)

Thanks guys for the support.

*Butcher wrote:
I would look at having a small sink or eye wash station, at least a water hose with a valve just outside the door easy to get to. *
I am thinking about running a water line to the building this spring for an outside water faucet.
Thanks Butcher,

*Philddreamer wrote
I have a dam to keep any spills from finding their way to the floor. 
Your respirator, when not been used, should be in a container, so to keep it from been exposed to the ambient, thus the cartridges lasting longer.*
That is a good ideal about the dam, thank you for your advice on the respirator and cartridges, they are not cheap to replace so any help to prolong their life is appreciated. 
Thanks philddreamer,

Palladium, thank you for explaining, there is an exhaust on the side of the pump. I will make the corrections in the morning and using cardboard under the pump is a good idea -one that is needed. I like the ideal about placing it outside running the hose to the inside, when running the check valve - this should go between the flask and the exhaust or on the exhaust side. Thanks for all the help.

Ken


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## Palladium (Feb 14, 2013)

In line between the flask and the condensation trap you have will be fine. I found that out the hard way when i cut my pump off and the flask was still under vacuum. I had gold chlorides in the flask and walked away to come back and find the oil had risen back up my hose and into my filter flask creating one hell of a mess. Yep!!!! Only took me once to learn that lesson. :mrgreen:


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## adoreman (Mar 13, 2013)

hi jenje, 
i made a scrubber and a very effective water spray you can use is the spinning sprinklers used in gardening. put like 3-4 of them and it sprays well. also those synthetic grass mats can be used as filters.


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## solar_plasma (Mar 13, 2013)

I love it! Geat work.

The fireman in me would suggest a refractory lining on the inside, maybe eternitplades, as fx. conc. HNO3 is principedly capable of inflaming wood. If it is not ex-protected in some way, there shouldnt be emitted great amounts of inflammable gas as H2 or H2S. Both of them have a lower explosion limit of about only 4 vol.% (http://en.wikipedia.org/wiki/Flammability_limit). Since that would be 8 litres per 200l of air, it had to be quite great amounts, but I would keep this in mind.

Would be a nice terrarium tank too


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