A gallery of home built hoods and fume scrubbers _hood_

[geoffrod]

So long time reader new poster,
I am just starting to build a small fume hood and wet scrubber setup, something in the vein of the pictures provided by @4metals and others.
The cabinet im using a 410mm wide opening x 705mm high x 545mm depth, its a cabinet i am repurposing an will do what i need to start with, i am planning on having a hot plate with a 2000ml beaker for reactions and collection of fumes into the scrubber.
I might be a little tight but im not planning on running much to start. the idea is to setup a safe way of working.
I will be running a 6" inline fan thru a venturi (cut off funnel) drawing the air flow out of the box.
the main vacuum for the reaction beaker will be handled with a water eductor using a double diaphragm pump, 12L/min 130 psi. this will hopefully create enough vacuum to pull the fumes thru the wet scrubber canisters, well thats the plan, everything is in test mode atm.
attaching a few photos and a video of smoke getting drawn up the fume exit.
i look forward to adding more pics as the build goes along.
Edit - added pump pics

 

[Yggdrasil]

So long time reader new poster,
I am just starting to build a small fume hood and wet scrubber setup, something in the vein of the pictures provided by @4metals and others.
The cabinet im using a 410mm wide opening x 705mm high x 545mm depth, its a cabinet i am repurposing an will do what i need to start with, i am planning on having a hot plate with a 2000ml beaker for reactions and collection of fumes into the scrubber.
I might be a little tight but im not planning on running much to start. the idea is to setup a safe way of working.
I will be running a 6" inline fan thru a venturi (cut off funnel) drawing the air flow out of the box.
the main vacuum for the reaction beaker will be handled with a water eductor using a double diaphragm pump, 12L/min 130 psi. this will hopefully create enough vacuum to pull the fumes thru the wet scrubber canisters, well thats the plan, everything is in test mode atm.
attaching a few photos and a video of smoke getting drawn up the fume exit.
i look forward to adding more pics as the build goes along.

Two things strike me.
Since most of the reaction gases/fumes are heavier than air, the suction should be at the lower part of the hood.

Next I think that the funnel might need to be opened more.
I'm afraid it will create too much back pressure on the flow from the fan.
You are the one seeing this live and it is easy to adjust.

Besides that it seems good.

Edit to add:

It is wise to duct the intake air directly from outside, not the same room as the hood are placed in.

 

[geoffrod]

Two things strike me.
Since most of the reaction gases/fumes are heavier than air, the suction should be at the lower part of the hood.

Next I think that the funnel might need to be opened more.
I'm afraid it will create too much back pressure on the flow from the fan.
You are the one seeing this live and it is easy to adjust.

Besides that it seems good.

Edit to add:

It is wise to duct the intake air directly from outside, not the same room as the hood are placed in.

Thanks so much for your reply, greatly appreciated and taken on board. The fumes being sucked out are planned to be anything rogue that doesnt get taken to the scrubbers, which hopefully will not be much at all.
I take your comment about the funnel, i have increased it twice already, as the fan being used cant handle compressing so much, i was reluctant to cut too much more from it as i was thinking i needed the end of the funnel to be as far along the exit tube as it could be? but there is definitely backpressure already there as you rightly state. More modifications required i guess.
Regards
Geoff

 

[Shark]

Can't really tell how long your funnel is but something like this one on Amazon might work.

Long Funnel

 

[geoffrod]

Can't really tell how long your funnel is but something like this one on Amazon might work.

Long Funnel

Hi @Shark , thanks for the reply, i guess the question i need to answer is how far into the wye does the funnel need to go? i have at the moment got the end of the funnel at or near the end of the wye as in where the straight section begins again, hope that makes some sense.
the one you have shown looks longer for sure, but im not sure the fan will push the air thru without causing more back pressure.
What comes to mind with the picture from @4metals is a leaf blower nozzle picture attached.
Thanks again for the reply.
i will go do some research on venturi's
Regards
Geoff

 

[geoffrod]

Hi @Shark , thanks for the reply, i guess the question i need to answer is how far into the wye does the funnel need to go? i have at the moment got the end of the funnel at or near the end of the wye as in where the straight section begins again, hope that makes some sense.
the one you have shown looks longer for sure, but im not sure the fan will push the air thru without causing more back pressure.
What comes to mind with the picture from @4metals is a leaf blower nozzle picture attached.
Thanks again for the reply.
i will go do some research on venturi's
Regards
Geoff

i think i found a decent funnel to do the job.
a flo tool extra large funnel.
a little trimming and it should be a winner.
Edit, added trimmed and fitted new funnel/venturi

 

[geoffrod]

So with the above funnel as the venturi there was too much back pressure created, so i have revised my design to use a 460mm safety cone cut down to fit straight out of the fan
it has a lot more pull in the hood now.

 

[geoffrod]

more to update,
got the hood fugitive fume extraction working.
now onto the reaction fume extraction and scrubber setup
canisters have bio ball and Racher rings/Ceramic Rings.
I am assuming that i dont really need to fill these canisters to the brim with the media, please correct me if i am wrong. i do need to fill the canisters 90% with the scrubbing fluid.
Just on the scrubbing fluid, i am using sodium carbonate and i think i have read i need to get the PH to 10 please any correction/confirmation would be greatly appreciated.
Cheers
Geoff

Edit- added more photos of scrubber canisters, also added a picture of container of sodium hydroxide, would this be appropriate to use in the canisters?
the plan is to pull a vacuum with micro vacuum pump through the canisters, with the thru put of air from the pump to go back into the hood and be pulled thru a second scrubber bucket with the high pressure pump and venturi as pictured in previous replies. I thought i had read from @4metals that the scrubber will clean 80% of the fumes so a second go at it should reduce this and then if i run the vent from the bucket scrubber back into the fume hood i should be evacuating most if not all of the fumes?? This is very important to me an if i am flawed in my thinking please feel free to correct me.

 

[Yggdrasil]

more to update,
got the hood fugitive fume extraction working.
now onto the reaction fume extraction and scrubber setup
canisters have bio ball and Racher rings/Ceramic Rings.
I am assuming that i dont really need to fill these canisters to the brim with the media, please correct me if i am wrong. i do need to fill the canisters 90% with the scrubbing fluid.
Just on the scrubbing fluid, i am using sodium carbonate and i think i have read i need to get the PH to 10 please any correction/confirmation would be greatly appreciated.
Cheers
Geoff

Edit- added more photos of scrubber canisters, also added a picture of container of sodium hydroxide, would this be appropriate to use in the canisters?
the plan is to pull a vacuum with micro vacuum pump through the canisters, with the thru put of air from the pump to go back into the hood and be pulled thru a second scrubber bucket with the high pressure pump and venturi as pictured in previous replies. I thought i had read from @4metals that the scrubber will clean 80% of the fumes so a second go at it should reduce this and then if i run the vent from the bucket scrubber back into the fume hood i should be evacuating most if not all of the fumes?? This is very important to me an if i am flawed in my thinking please feel free to correct me.

Looks good.
What is needed is aretention time if about 9 seconds.
Are you using Carbonate or lye?
Caustic Soda is Lye, NaOH

 

[geoffrod]

Looks good.
What is needed is aretention time if about 9 seconds.
Are you using Carbonate or lye?
Caustic Soda is Lye, NaOH

Hi @Yggdrasil thanks for the reply, I am presuming you mean a retention time is required? i am not sure if the vacuum pump will create too much or not enough vacuum, so if its too much flow, could i bleed off the excess, if not enough i will need a bigger pump!
Im not sure how to accurately workout what the flow will be as i have the rings in the canisters, and will the flow rate of the pump stay true thru the liquid?
I can workout what the volume of the canisters and i could fill them with fluid with the rings and bio balls in situ, so that should give me the actual volume of the canister! am i correct?
Then working on the pump specs of 40L/Min that is 0.6667 litres per second, if we need contact for 9 seconds we need a volume of 6 litres, is this total of all 3 canisters?
thanks in advance.
Regards
Geoff
Edit,
sorry i missed the other question, i was thinking carbonate in the canisters and lye in the bucket, but either either

 

[Yggdrasil]

Hi @Yggdrasil thanks for the reply, I am presuming you mean a retention time is required? i am not sure if the vacuum pump will create too much or not enough vacuum, so if its too much flow, could i bleed off the excess, if not enough i will need a bigger pump!
Im not sure how to accurately workout what the flow will be as i have the rings in the canisters, and will the flow rate of the pump stay true thru the liquid?
I can workout what the volume of the canisters and i could fill them with fluid with the rings and bio balls in situ, so that should give me the actual volume of the canister! am i correct?
Then working on the pump specs of 40L/Min that is 0.6667 litres per second, if we need contact for 9 seconds we need a volume of 6 litres, is this total of all 3 canisters?
thanks in advance.
Regards
Geoff
Edit,
sorry i missed the other question, i was thinking carbonate in the canisters and lye in the bucket, but either either

The volume is less important than the height (the distance the bubbles has to travel)
Bioballs will give it more time so that is good if you find something suitable.
A tip.
If you use them for Nitric, water and Peroxide in the first will regenerate some of the NOx to Nitric.

 

[Yggdrasil]

Hi @Yggdrasil thanks for the reply, I am presuming you mean a retention time is required? i am not sure if the vacuum pump will create too much or not enough vacuum, so if its too much flow, could i bleed off the excess, if not enough i will need a bigger pump!
Im not sure how to accurately workout what the flow will be as i have the rings in the canisters, and will the flow rate of the pump stay true thru the liquid?
I can workout what the volume of the canisters and i could fill them with fluid with the rings and bio balls in situ, so that should give me the actual volume of the canister! am i correct?
Then working on the pump specs of 40L/Min that is 0.6667 litres per second, if we need contact for 9 seconds we need a volume of 6 litres, is this total of all 3 canisters?
thanks in advance.
Regards
Geoff
Edit,
sorry i missed the other question, i was thinking carbonate in the canisters and lye in the bucket, but either either

Hmm are you using an actual pump?
Not an eductor?
Or are you showing the pump for the eductor?

Edit to correct spelling error

 

[geoffrod]

The volume is less important than the height (the distance the bubbles has to travel)
Bioballs will give it more time so that is good if you find something suitable.
A tip.
If you use them for Nitric, water and Peroxide in the first will regenerate some of the NOx to Nitric.

Definitely will be used with Nitric, so happy to use water and peroxide, but what volume of peroxide to water and what concentration of peroxide?
I have Bioballs and Ceramic rings as well
So i am still perplexed as to how i workout to get the right retention time in the fluid?
BTW i really appreciate the reply's, I have held off for quite some time asking questions in fear of feeling silly asking stupid questions.
Thanks
Geoff

 

[Yggdrasil]

Definitely will be used with Nitric, so happy to use water and peroxide, but what volume of peroxide to water and what concentration of peroxide?
I have Bioballs and Ceramic rings as well
So i am still perplexed as to how i workout to get the right retention time in the fluid?
BTW i really appreciate the reply's, I have held off for quite some time asking questions in fear of feeling silly asking stupid questions.
Thanks
Geoff

I have not heard about what concentration is recommended.
But use some 3% and see how it goes.
The retention time should be fine but to check test the pH in the last cylinder from time to time.
If it goes down there is some acidic fumes reaching it.

 

[geoffrod]

Hmm ate you using an actual pump?
Not an eductor?
Or are you showing the pump for the educto

Hmm ate you using an actual pump?
Not an eductor?
Or are you showing the pump for the eductor?

yes i will be using a vacuum pump as shown, that will pull the fumes through the canisters, the air exiting the vacuum pump is planned on going back into the fume hood and out to some canisters via an eductor connected to the high pressure water pump into the bucket scrubber which will vent to the fume hood again and exit to atmosphere.
sounds complicated and maybe overkill but just want to be sure i am capturing as much as possible.

 

[geoffrod]

I have not heard about what concentration is recommended.
But use some 3% and see how it goes.
The retention time should be fine but to check test the pH in the last cylinder from time to time.
If it goes down there is some acidic fumes reaching it.

So 3% in the whole canister?

 

[Yggdrasil]

yes i will be using a vacuum pump as shown, that will pull the fumes through the canisters, the air exiting the vacuum pump is planned on going back into the fume hood and out to some canisters via an eductor connected to the high pressure water pump into the bucket scrubber which will vent to the fume hood again and exit to atmosphere.
sounds complicated and maybe overkill but just want to be sure i am capturing as much as possible.

You will be much better off using an e-ductor driven by water.
If gases comes through they will be dragged in with the water.
Use a tank and an electric water pump to pump the water through the e-ductor.

 

[Yggdrasil]

So 3% in the whole canister?

I have never seen a number for it, so I suggest starting with 3%.
You actually do not need the peroxide but it improves the process over using water alone.

 

[geoffrod]

You will be much better off using an e-ductor driven by water.
If gases comes through they will be dragged in with the water.
Use a tank and an electric water pump to pump the water through the e-ductor.

point taken

 

[AustAuScrap]

When I was involved with gas washing- which is the second part of what the process that is being discussed here - for it to happen well it has to be in positive pressure, -even if only a few cm water guage-
On the fume extraction side though it occurs best, and is safest if it is negative pressure .- induced draft
In practice when I gas wash I use the suction side of a acid resistant centrifugal fan to pull the fumes from the cabinet and somewhere over the functioning of the fan it transitions to positive pressure to push the fumes thru the chosen washing mediums.
The reality of the whole process is firstly a safety thing- to get people killing fumes away from people, Also from a safety point of view the extraction method should have no easy way to ignite any volatiles that might also get extracted - so spark proof motors should be the motive force.
Acid resistant fans of the correct volume flow etc are on the expensive side.
One interesting set up I saw had a whole sealed cubicle where the fume hood was mounted and the person did his chem processing. Fans forced positive pressure into the cubicle so forcing air flow out the extraction duct continually. At a point further along the duct it swung downward with multiple misting type sprayers set up to spray wash the passing Air/fumes, The spray mix supposedly both chemically neutralized and or diluted any nasty mists. As to how well this functioned chemically I don't know but with the aid of a bee keepers smoker we were able to prove all smoke we made in the fume hood did indeed flow out the extraction duct and not come back to where the person was. - even with only one of the 2 fans working and the misting sprayers working,
The fans used were recycled "swamp cooler" types from a junk yard,
One rework I know that had to be done on this build was that some of the ducting was not resistant to acid fumes- and had to be changed to polypropylene