Cheap home made scrubbing unit (theoretical design)

[eeTHr]

Johnny---

If you calculate the speed of the air through the pipe in the water, to give you the recommended 100 CFM per square foot of front opening in your fume hood, you will see that the air (and resulting water splash from the bubbles) will be like a hurricane in there. It's quite possible that even a steel drum would collapse under such a vaccum, and your blower will likely suck lots of the lye water.

I would suggest that you test it on a small scale, and find out for yourself.

 

[Johnnycat535]

I actually already have with the steam cleaner blower (around 93CFM), a vacuum hose, and Rubbermaid container. It does cave in some what but it still keeps a good enough seal to hold up. I used it with water and some baking soda when dissolving my BM's in HCL & H2O2. It's got at least 24 hours of use on it so far. For something I threw together in about 3 hours with stuff I had around the house it works perfectly and with simple PVC framing it can hold up with out much of any caving. I'll post some pictures when I get back from dinner. I also have found that a 5hp shop vac rates in at around 175CFM, give or take. I'll also do my best to draw up a design to hopefully be able to obtain some numbers before the final build. Thanks everyone!!!

 

[Johnnycat535]

OK so here's my first prototype. Please don't comment negatively about the fume hood. It was thrown together for testing purposes.

 

[butcher]

sometimes we can learn from the negative as well as the positive, well I guess it is because I am an electrician I think this way.

 

[Johnnycat535]

It's not that I don't want to learn it's that the fume hood you see won't be involved in my next prototype. I'm going to build the one I listed earlier in this thread. Believe me I know the importance of negative advice. In my opinion its the best kind of advise.

 

[butcher]

maybe if you give a description of how it works, I see what looks to be a vacuum cleaner motor, a hose from the bottom of the seal-able tub going to a plastic jug.

if the blue tub is the scrubber what are you going to use to keep the gases in solution long enough to react and neutralize, the large hose and high velocity of the vacuum motor would suck those fumes in and out of solution so fast they would be out in the air before they even thought about getting neutralized, where are you exhausting the fumes to away from where you are working

I do not know how long the motor would last in these conditions, and mounting it to the plastic, I would be concerned of fire danger.

just thought I would add some negatives.

now for a little positive,

Good job working on this, with work you will work out the bugs and get a working fume scrubber, I like how you are working to remedy the problem with fumes keep up the good work.

 

[Johnnycat535]

The heat from the motor was my biggest concern at first so I used high temp gasket sealer. The motor is from a steam cleaner, and doesn't seem to get that hot. The hose's are from a vacuum and the steam cleaner. I'll do my best to draw something up. A lot of your questioned can be answered in my earlier post. I'll be using a 55 gallon plastic drum, and have been made fully aware that the blower will need to be quite powerful. I'm hoping 4metals will have a way for me to calculate what will be needed. I'm hoping using a diffuser to produce multiple small bubbles will help a lot with any lost time in the solution. I have a couple more idea's for that as well. Also in the works is to add a stack for the exhaust to be dispersed about 6' high. I still have a few things I need to figure out, but with everyone's help here I've made a lot of ground in a short period of time. Thanks for the positive as well. I wanna make sure to do it the right way, and come up with a way that is cost effective at the same time. Once I draw it up it'll be easier to understand what I'm going for.

 

[Johnnycat535]

So here's what I came up with. Let me know if you have any questions or concerns. I included as much detail as I could think to.

 

[butcher]

John I like the bubblier in that design, it will give more surface are to the bubbles of gases to be scrubbed, that and something inside the column for the bubbles to hang onto for a while would help, one member posted some blue balls (bio balls?) that looked like they would work good (maybe S. Brown).

The taller the coulomb, and the smaller, and harder for the bubbles to escape gives more time for the reactions to work.

Move the fan further from the liquid solution up on top of the exhaust stack, also this means water or condensed fumes can fall back into solution instead going into the fan, do not put motor in path of the fumes.

Possibly add a small chemical pump to pull caustic solution from bottom of the barrel and spray it down from the top this can also help with escaping fumes and mixing as well as keeping fresh caustic solution on rising acid fume bubbles caught in the media.

 

[Johnnycat535]

Yea I got the idea after Sam's comments. I'm going to mount the blower to the top of the exhaust stack then attach a fan for cooling, and a vent cover to keep it dry. Once I have everything setup then I'll incorporate using some kind of additional filtration in the stack. I think I'll use a 2" pipe for the inlet and a 4" for the stack to better mount the blower. Also I believe that should mean less water in the pipes for when the blower is turned on, and better CFM at the fume hood. I may use instead of a T fitting a X fitting for even better surface area. That way I can drill much smaller holes, and much more of them. Being optimistic I feel this next prototype should be fully functional with only few modifications after testing. I'm excited to begin collecting everything tomorrow to begin assembling. I'll be sure to include pictures as it progresses.

 

[Johnnycat535]

Step one: I installed the fittings that connects the down pipe and fume hood inlet to the drum. I used a piece of rubber to make a gasket on both sides. The gaskets are sealed with PVC cement. The two fittings screw together as well so it should be enough to create an air tight seal that will hold up to the pressure. Let me know what you think and if you have any questions. Thanks everyone.

 

[butcher]

Looks like it will work fine, next time see if they have bulkhead fittings.

http://www.google.com/search?hl=en&q=bung+fittings&rlz=1R2RNQN_enUS457&bav=on.2,or.r_gc.r_pw.&biw=1024&bih=539&wrapid=tlif134855575904610&um=1&ie=UTF-8&tbm=isch&source=og&sa=N&tab=wi&ei=2lNhUMvtLMqeiALN0oHwAg#um=1&hl=en&rlz=1R2RNQN_enUS457&tbm=isch&sa=1&q=bulkhead+fitting&oq=bulkhead+fitting&gs_l=img.12...0.0.7.359.0.0.0.0.0.0.0.0..0.0...0.0...1c.ATxx_Bi8DWM&bav=on.2,or.r_gc.r_pw.&fp=4dda7dcaf871ccf&biw=1024&bih=539

 

[Johnnycat535]

I knew I should of asked about that before I went out buying parts. Live and learn though. I'll be sure to upload more photo's tonight as I progress. I hope to get the connection for the stack on today, but I don't believe they have any 4 inch PVC bulkhead fittings. Or at least I couldn't find them online from Lowe's or Home Depot.

 

[goldenchild]

That drum makes me think of what I'm going to do for my scrubber. I will be using 7 gallon buckets. Possibly a relay of them that look like this.

 

[Johnnycat535]

Two questions: First I'd like to reinforce the drum with a couple 2x4's placed inside. I wasn't sure it that would be a problem. Second I'm considering using a rheostat for my motor to better control the system. Would this work? http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=380075545605 The blower I'm using is 120v 60hz and 12amps.Thank you all for your help. And I'll more pictures tonight on my progress.

 

[Johnnycat535]

Latest pictures. My drill died on me so I couldn't finish the holes in the diffuser. I'm also going to use pieces of rubber to put on the ends of the 2x4's with PVC cement to be sure I don't have any unexpected leaks. I'll have it fully assembled tomorrow given no problems occur. Wish me luck!!!

 

[butcher]

Looking good,

I do not know if will help but Harbor freight sells a cheap plastic welder, they also sell the plastic welding rods, or you can trim some of the same type of plastic from the article your welding to use as rods.

 

[Johnnycat535]

I thought of doing that to seal my pipes, but then I remembered I'd never welded anything and though it best to stick to what I know LOL. Do you have any knowledge on if that rheostat will work for my blower? And just wait till you see what I rig up to handle it getting over heated. Hopefully I'll be able to start that tomorrow.

 

[butcher]

The motor speed controller in the link above says:

Will work with any universal AC motor.
Will not work on induction, shaded pole, soft/slow start, or brushless type motors.

So it depends on what type of motor you are using.

 

[Johnnycat535]

http://www.totalvac.com/B-010-5970ES.html?zmam=6843742&zmas=1&zmac=57&zmap=B-010-5970ES&gclid=CNLd2KCO07ICFQKCnQod_WAAWQ
That's the motor I have so It'll work. I just wasn't sure if these would damage the motor or not.