A gallery of home built hoods and fume scrubbers _hood_

[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

 

[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.

Hi,
so the double diaphragm water pump i bought doesnt seem to be producing enough flow to make the eductor work very well.
I attached the eductor to the mains water and got a nice suction thru the eductor, so back to the drawing board. need to find a better pump.
Edit - i have bit the bullet and purchased this pump.
after testing with the hose i asked Copilot and they did some calculations for me - i think this pump should provide similar specs on delivery.

1. Calculate the flow rate per second:

Flow rate per second=20 liters50 seconds=0.4 liters per second\text{Flow rate per second} = \frac{20 \text{ liters}}{50 \text{ seconds}} = 0.4 \text{ liters per second}

1. Convert the flow rate to liters per minute:

Flow rate per minute=0.4 liters per second×60 seconds per minute=24 liters per minute\text{Flow rate per minute} = 0.4 \text{ liters per second} \times 60 \text{ seconds per minute} = 24 \text{ liters per minute}
So, your water supply delivers 24 liters per minute.
In New South Wales, the standard mains water pressure for residential homes typically ranges between 300 and 500 kilopascals (kPa), which is approximately 43 to 72 pounds per square inch (psi)

 

[4metals]

Seeing as you will be using an eductor to draw fumes through a scrubber and transfer liquids that tend to fume, selecting a pump that has corrosion resistance will extend it's life. The liquid you will recirculate tends to become corrosive and takes its toll on the pump.

 

[geoffrod]

Seeing as you will be using an eductor to draw fumes through a scrubber and transfer liquids that tend to fume, selecting a pump that has corrosion resistance will extend it's life. The liquid you will recirculate tends to become corrosive and takes its toll on the pump.

Thanks for the reply @4metals greatly appreciated. will careful monitoring of the fluid running thru the pump help improve the pumps longevity?
btw, thanks for all the great information on this subject that you have provided.
Regards
Geoff

 

[4metals]

will careful monitoring of the fluid running thru the pump help improve the pumps longevity?

Yes, if you monitor the pH and keep it neutral [ish], using caustic you can extend the life for sure. I live in the real world of refiners who only maintain stuff when it breaks. For them I recommend using the March series of highly corrosive magnetic drive pumps HERE. I always visit refineries, or I did before I retired, with 2 things, pH papers and a dropper bottle of stannous chloride. The pH papers to check the pH of their vacuum reservoir to judge just how often they do not do maintenance, and the stannous to drip on the floor and trash can contents to see just how sloppy their workers are. I don't hide what I'm doing because hopefully they will learn to do it themselves to see how their staff is actually performing. (one can hope right?)

 

[4metals]

I always visit refineries, or I did before I retired, with 2 things,

Actually with 3 things. I have a very accurate pocket velometer to roughly gauge the air velocity through the hoods, another thing to keep tabs on.

 

[geoffrod]

Yes, if you monitor the pH and keep it neutral [ish], using caustic you can extend the life for sure. I live in the real world of refiners who only maintain stuff when it breaks. For them I recommend using the March series of highly corrosive magnetic drive pumps HERE. I always visit refineries, or I did before I retired, with 2 things, pH papers and a dropper bottle of stannous chloride. The pH papers to check the pH of their vacuum reservoir to judge just how often they do not do maintenance, and the stannous to drip on the floor and trash can contents to see just how sloppy their workers are. I don't hide what I'm doing because hopefully they will learn to do it themselves to see how their staff is actually performing. (one can hope right?)

So am i too assume that the starting pH is neutral water? i was thinking i would use sodium carbonate mixture keeping it high? in the canisters i was going to use sodium hydroxide in the last 2 and water and peroxide mix in the first?

I thought i had read that you mentioned that this type of scrubber will only scrub 80% of the fumes? would it then be a benefit to recirculate the fumes back thru a second scrubber and therefore scrub 80% of the residual 20% from the first scrub? which should leave about 4% un-scrubbed?

 

[4metals]

I thought i had read that you mentioned that this type of scrubber will only scrub 80% of the fumes?

Lots of scrubber designs have been discussed here, which are you planning on building?

 

[geoffrod]

Lots of scrubber designs have been discussed here, which are you planning on building?

the one that you have presented here.
i have the fan and venturi working for the hood extraction, i have 3 canisters completed, i am now working on the water aspirator vacuum system.
I have another question in regards to the return water thru the Eductor/Aspirator, you have indicated that it should go into a return tune in the reservoir, but how does this work, does the tube have holes in the base or all over it, is it blanked off so as to send the return water out of it and over the top?
Thanks in advance

 

[Yggdrasil]

the one that you have presented here.
i have the fan and venturi working for the hood extraction, i have 3 canisters completed, i am now working on the water aspirator vacuum system.
I have another question in regards to the return water thru the Eductor/Aspirator, you have indicated that it should go into a return tune in the reservoir, but how does this work, does the tube have holes in the base or all over it, is it blanked off so as to send the return water out of it and over the top?
Thanks in advance
View attachment 67113

The water goes through the e-ductor and directly into the tank as a reservoir.
The pump then pumps from the same reservoir.
Over time the water in the tank may go acidic so a mild caustic solution is good to have.
Test it from time to time and if it creeps towards 7 add some more carbonate.