# Gas Extraction System



## chrisv (Jan 24, 2011)

I'm looking at constructing this new extraction system(see attached) as I'm going to be taking on alot more scrap to process and feel the system I currently have is not going to be able to cope with the extra work loads.
So, starting from the main extraction hood, I'm going to get this made of Aliminuim sheet at 2/3ft long and about 1.5ft wide, I'll need to get this painted to prevent any corrosion from any gasses. I might also have to make three holes on the top of the hood to allow for three flexi pipes to connect into a cross tee fitting and then into the main 4" pipe that would then go through the whole system. The reason I was thinking of using flexi ducting to connect to the top of the hood is so that I could adjust the hight of the hood if required. I am going to use 8" pipe for the scrubber and near enough fill it with hair curlers and also, at the bottom of the scrupper, have a one way valve so that the solution sprayed at the top of the scrubber can drain out of the scrubber back into the main vessle from where the solution gets pumped out from, this vessle is going to be lower than the main system so gravity can do its thing when it comes to draining out the solution from the scrubber. Also, as per drawing, above the scrubber, I'm going to fit a 90degree bend in and then after about a foot of it running horizontal, I'm going to fit another 2ft of 8" pipe with a top and bottom access panel in, and in this section, I am going to fill in with charcoal brickets inside of plastic netting so that the partialy neutralised gasses can flow thourgh this final section to try and neutralise a bit more of the gasses but also, hopefully neutralise any strong smellies to keep the naighbours happy 

So, any thoughts would be grately welcome and any advice if you think I've missed anything crucial.
One thing I do need clarified, for the solution thats going to be sprayed in from the top of the scrubber, I'd prefer to use Sodium Carbonate mixed with water. I'd prefer to stay clear of Sodium Hydroxide as I have to kids that would be in the garden in the summer months and feel really concerned about spillage while they are near


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## goldenchild (Jan 24, 2011)

Aliminuim will easly be digested by HCL.

Try this thread. 

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=40&t=4776&hilit=fume+hood


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## 4metals (Jan 25, 2011)

I assume the first and second extractors are the exhaust blowers. The total flow you get of air from the hood may be a small part of the overall flow. You can increase the draw you get from this type of configuration by tapering the outlet from the blower so the air stream is compressed. When the compression ends the expanding air will draw more air than non compressed air and the flow will be greater. If it is forced to get that extra air from your hood area, the result is more draft. Sort of like making a venturi.

This may make it more understandable.


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## chrisv (Jan 25, 2011)

Thanks for the info and your opinions.
Regarding your suggestion with the hood made pf ply, my only concerns is the heat thats going to be generated from my cooking 10 cats in one go in a few porcelan pots. Im getting these cats from a engineering company, and he said he would build this extractor system out of what ever I like, so I thought Aliminuim and then give it a couple of licks of what ever paint so that the gasses and acids dont penitrate to the metal. Basicaly, the whole system is going to get a good couple of coats of paint, lol

Regarding the suggestion that Goldenchild made, makes alot of sence, think I'll get my engineer to put one in.

What do you guys think about using Sodium Carbonate in water to spray from the top of the scrubber??


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## rusty (Jan 25, 2011)

4metals said:


> I assume the first and second extractors are the exhaust blowers. The total flow you get of air from the hood may be a small part of the overall flow. You can increase the draw you get from this type of configuration by tapering the outlet from the blower so the air stream is compressed. When the compression ends the expanding air will draw more air than non compressed air and the flow will be greater. If it is forced to get that extra air from your hood area, the result is more draft. Sort of like making a venturi.
> 
> This may make it more understandable.



Thanks 4metals your sketch shows a very economical venturi and easy to make, I'll use this for my fume hood.

Best Regards
Gill


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## dsmith2828 (Mar 9, 2011)

chrisv said:


> What do you guys think about using Sodium Carbonate in water to spray from the top of the scrubber??


Did this questions get answered? I was wondering the same thing.


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## 61 silverman (Apr 2, 2011)

I don't have the diffinitive answer on using Sodium Carbonate. I do have an additional Question on the prefered scrubber solution.. How does household ammonia work, using a chemical pump, I don't think the ammonia would cause any pump damage.! Allmost possitive Sodium Carbonate , (as long as all disolved ) would cause no pump damage, How much water is necessary per 1lb.? cold !!!
Mark


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## 4metals (Apr 2, 2011)

Ammonium hydroxide in a hydrochloric fume will form ammonium chloride and an inescapable white plume of gas exiting your system.


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## Oz (Apr 2, 2011)

If you place the openings of 2 containers (one HCl and the other ammonium hydroxide) in close proximity you will see the haze 4metals is referring to. While it is not efficient, if you are in a pinch for some ammonium chloride crystals they will slowly start growing on the edge of your containers.


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## 61 silverman (Apr 6, 2011)

Thank You , Sodium bicarbonate is my choice.. Thanks again 
Mark


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