Fume Hood, Will it work?

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IntelGold

Well-known member
Joined
Sep 9, 2012
Messages
117
Location
UK
Hi All, Not been on the forum for a while. I've been thinking of building a fume hood which will also act as a fume extractor for several buckets which will be used for AP. I would first like to say that it will only be used for HCL and Clorox Reactions, NO Nitric. Hopefully you can get the idea of what im trying to achieve.
Here's a very rough sketch of the proposed setup.
Any help would be Good.
Thanks.
Pic01 (1).JPG
 
I think I can see what your aiming for but your scrubber looks just like a reservoir which if I'm reading your sketch right won't work as there won't be enough pressure to push the fumes through it, for the scrubber to work you need it spraying the fumes with a mix of caustic, hydrogen peroxide and water over a large surface area and with enough time in the actual unit to scrub the fumes.
If you did your hcl bleach reactions in sealed conical beakers and piped the fumes through several more conical beakers the first with water the second with the mixture above it should do the job quite well, it won't remove all the fumes but the majority will be caught, a fume hood over the reactions venting the final fumes and then also scrubbed would finish the rest, if you intend to scrub your leach buckets with the same scrubber a valve to increase or decrease the flows from either area would be handy.
 
Hi Nick, Thanks for the input. The scrubbing material was going to be marbles or activated carbon, maybe a mix of the two? This would allow air through unlike water. I only need to scrub it a little as I said only HCL is being used no Nitric. Cheers.
 
I might be wrong but I fear carbon won't last too long and will need regular changing, instead of marbles old plastic pipe cut into small rings might be cheaper and still give a large surface area but it will need to have the solution constantly running over it to scrub the fumes along with the fumes lingering in the scrubber so they can be scrubbed efficiently.
I still think that sealed reactions might well solve most of your problems with the chlorox reactions and easier to create, 4metals posted his system sometime back so do a search and see his drawings.
You might still need to vent the final fumes but a lot of the worse chemicals will be removed , for your AP reactions maybe some sort of condenser would help before venting off.
 
There are three drawbacks with placing the fan close to the hood and in front of the scrubber.
- If the filter gets too clogged the fan is going to create pressure in the hood and blow the gases out in the room instead of up the chimney.
- It will create a positive pressure in the scrubber with respect of the room, any leak will let out fumes in the room.
- The volume of air going through the scrubber is increased and the dwelling time is decreased, less scrubbing occur or you have to build a bigger scrubber.

If you place the eductor / fan in the end of the system you get a number of advantages.
- No matter how clogged the scrubber gets it will never blow fumes back
- You create lower pressure in the ducting and suction, any leak will just suck air from the room.
- Lower volume of air going through the scrubber means you can have a smaller scrubber or scrubbing is done better.
- Lower air volume through the ducting means less resistance and higher flow / better drag from your hood.

Göran
 
From the picture it appears you are trying to use the venturi effect. I have experimented with it before and come to the conclusion that it is somewhat but not sufficiently effective. I think you would need a very large blower if that is what you are going for. A bit confused about where the fumes are going once it has left the hood. Is it going to both the scrubber and sealed buckets at the same time? Attached is my venturi effect experiment. Also a drawing of a different approach. It would involve using some kind of sprayer/pump to keep your media wet by recycling the neutralizer within the buckets. You would of course need to monitor the PH. It would also probably be a good idea to keep this system very modular.


hood.jpg


[youtube]http://www.youtube.com/watch?v=-4oQU-SyYZY&feature=share&list=UUulJxV7L-c3hiBhghfk1MYA&index=5[/youtube]
 
just throwing a couple cents in here...

have you considered the volume of the fumes you need to scrub vs. the volume of air you would need to scrub to maintain safe fume hood operation? the latter could be rather large and require a large scrubber with a long residence time forcing the scrubber to be unessecarly large.

also, i have always thought of a fume hood as a "fail-safe" measure that should enclose the work you are doing. If something catastrophic goes wrong you should always be able to isolate your work and vent the air in the hood out of the building. With the scrubber in-line with the fume hood exaust, both systems have to work to maintain safe operation.

If you are doing a smaller volume of work, you could design a scaled down scrubbing system sufficent for your reaction and bring it inside your hood. For a larger indusrtial sized scrubber, you would have to design a separate closed system. Either way, the systems would operating independantly of each other and add an extra layer of saftey.
 
Thanks everyone for all your input. I was curious whether a Gas Blower would work? I have included some pics. Any advice would be welcome. Should I pull or push the fumes?
IMG_0373.JPG
IMG_0375.JPG
Thanks.
 
How would you make it run? Also, being that its all metal construction it would go to hell quickly. That is unless you protect it somehow. The one in my video is in fact all metal but it came painted and I used spray on truck bed liner. I think it lasted 2-3 years with regular use.
 
I have re-thought the idea of using this sort of blower. Its hard to find the fittings. I think I will go for this one -
http://www.ebay.co.uk/itm/Inline-Duct-STUBE150-6-100mm-Extractor-Hydroponics-Bathroom-Fan-700m3-h-/390686002408?pt=UK_Baby_Baby_Feeding_Bottle_Warmers_Coolers_LE&var=&hash=item5af6b34ce8
Probably the 6 inch model. Should hold up better if I give it a coat of Epoxy Spray. May need to get it re-balanced though. Any idea's welcome.
Cheers for all your help guys.
 
If your handy maybe you can try a home made fan, find a plastic fan blade about the size needed, take the plastic fan blade out of a the old household fan.

Mount it to a stainless steel shaft, this fan blade will mount in a pipe after the turn of an elbow in the plastic piping (duct work), a hole in the back of the elbow for the fans shaft, external bearings hold the fans shaft in alignment, a motor, coupling (or pulley) to a the motor turns the shaft, only the stainless steel rod and the plastic fan blade exposed to the acidic environment in the duct work, motor and bearings externally mounted on the back of the elbow.

You may just find a plastic squirrel cage fan out of an old fan like a dryer, or one of these http://www.ebay.com/itm/like/120951100484?lpid=82
mount it to a stainless steel shaft and build the box for the fan, keeping the motor and bearings outside of the acid fumes(you may also find the plastic fan shroud out of an old dryer:
https://www.google.com/search?q=dryer+plastic+squirrel+cage+fan&noj=1&tbm=isch&source=lnms&sa=X&ei=US1YU6_6N-jcyQHgiYBA&ved=0CAgQ_AUoAQ&biw=1024&bih=618
http://www.partselect.com/PS418726-Frigidaire-131775600-Blower-Housing-with-Blower-Wheel.htm
 

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This is the exact blower I use (also in video).

http://greendoorhydro.com/active-air-465-cfm-active-air-blower-system.html

You would need an adapter for your pipe like here.

http://florahydroponics.com/index.p...nfo&cPath=10_13&products_id=1538#.U1hg5GbD8dU

florohydro use to sell on ebay but it looks like they have stopped. I would buy both items from florohydro but it seems they don't have the 465cm blower. I guess you would have to order from each site. Also, you only need to buy 1 adapter as it doesn't take much damage at all. I originally bought 2 but never used the second one. If you could replace the stock squirrel cage with a plastic one you would really be set as that is the part that goes. So for about $120 you are making a very good investment in my opinion. Just don't forget to use the bedliner!
 
Thanks for all the input guys. I have been drawing up more rough sketches, hoping one of them will work. I have drawn a system that will draw air from the fume hood and the reaction buckets at the same time. I have placed blastgates at certain points hoping that I can just use blast gate number 1 (the one inline with the main extractor)in a closed position to extract just the fumes from the buckets and not the hood. When the fume hood is not in use the fumes from the buckets still need to be extracted. This means I can use the inline motor to extract and the fumes don't touch the main motor. The fumes would go straight to the exhaust. Maybe the inline motor would not last long but at around £10 they can be easily replaced. Let me know what you think and if you can improve on the idea?
IMG_0383 large.jpg
Thanks. :)
 
Trying to scrub the exhaust from a fume hood you will need a very large scrubber, the fume hood moves large volumes of air through it, the fumes from your reactions mix with this large volume of air flowing through the fume hood, making a larger volume to scrub.

In my opinion it would be better to scrub only the fumes from the reaction vessels (not mixed with all of the air flowing through the fume hood), this way the scrubber needed can be a much smaller unit, and anything that escapes the scrubber system as gases can be vented via the fume hood.


This would make the whole setup more simple, and effective, in my opinion.
 
If you want to use a growers fan then look at this one, it's almost all plastic and they have a 6 and 8 inch in the S-line with good CFM, the 8" is rated at 728 CFM at zero atmosphere.

http://www.ebay.com/itm/New-Vortex-8-S-Line-Inline-Duct-Fan-Blower-Hydroponics-Exhaust-Atmosphere-S-800-/390825935753?pt=LH_DefaultDomain_0&hash=item5aff0a8389

Update: Thought I would include the Manufacturers website. http://www.atmosphere.com/
 
It looks like you would need a beast of a blower! Remember for every cubic foot of space, you need 100cfm. This is before we even start to consider all the media the fumes will be pulled through. Also, the "inline motor fans" look like they would be competing with the main fan. One may even cancel out the other. I also don't understand what the buckets are doing. Is the last bucket on the far right somehow connected to the fan? If not the buckets will simply be sitting there as the fumes get pulled through the limestone.

Why not push the fumes through everything instead of pull? If you made a simple inline design where the buckets and limestone are next to each other it would give the fumes enough contact time to be scrubbed.

Edit: I think I see what you are trying to achieve a little better at second glance. With the end cap and drilled holes I think you are trying to retard the amount of fumes that initially go into the limestone to then go into the buckets. The problem with this is that the fumes will not only go down into the buckets but they will also go right back up to the fume hood. It's essentially a bottleneck. The cap and the drilled holes are actually making the system even more ineffective. Until you explain your design this is all speculation and if I am wrong I apologize.
 
Hi Butcher, The main motor on the right hand side does all the pulling of air. I do not have any scrubbing system on the fume hood. My aim was to pull the air from both the fume hood and the reaction buckets in one go. Main fan would be on when I was using the hood, Inline fan on the rest of the time. So sometimes the inline fan would be on 24/7. This way scrubbing would be done before both motors. It would not be very powerful using the inline motor but as long as it kept the fumes from escaping into the fume hood and out. I may have over engineered things a bit but want a system like this so its all kept indoors.
Thanks.
 
When I use the hood the main fan is on. When im not using the hood I would use the inline motor. Not both at the same time. The blastgates are there to block either pipe depending on which motor you are using. The buckets are sealed with reactions in them. They are joined by a piping system which i have yet to figure out? Because they are sealed I have a blastgate to protect against backdrafts.
 
I found this thread by 4metals to be very useful indeed.

http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=40&t=19965&hilit=fume+hood
 
If I use a motor like this surely it would work its specs are - 1300m3/hr at max pressure of 800Pa.
http://www.ebay.co.uk/itm/301118285130?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649
I have read the link, thanks. I think I haven't explained very well in my drawing what I am trying to achieve.
I will try and do another drawing which better describes my intentions clearer. I want to scrub the reaction buckets and the hood at the same time.
The fan I have listed above is very powerfull and I believe would work. Only problem is the noise level, 60db permanently I think will drive any neighbours mad?
What does everyone think of the sound level being on all the time?
Thanks.
 

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