how to build an acid resistant hood & scrubber

[Emil]

Thanks 4metals for your time and effort working this problem through for me. I think it will work and I will give it a try. The only question left is the ratio of Sodium Hydroxide to water to a pH above 10. I'll work that with trial and error.

You have been a great help to me and others on this forum solving our problems and I will add very patient.

Thanks,
Emil

 

[4metals]

The blowers are usually PVC or fiberglass, I do not know where to buy this equipment on your side of the pond but here in the US check out this link;
http://www.usplastic.com/catalog/ca...SPlastic&category_name=58&Page=1&clickid=land

Caustic can be pumped by a lot of different centrifugal pumps look for one rated for highly corrosive liquids. (also in us plastics catalog) as can nozzles. Personally I would steer clear of nozzles favoring small holes which are easy to maintain. (caustic tends to salt up and clog nozzles)

The only material which will be unaffected by the chemicals we are encountering is glass or glass lined steel, very pricey. Vinyl ester resin fiberglass holds up well and is affordable and doesn't break.

 

[goldsilverpro]

usplastic.com is an excellent company that carries about everything plastic you'll ever need, at good prices. They also used to have a Safety Equipment catalog that was excellent. I've bought many things from them in the past. The founder, Stanley Tam, was originally in the silver film scrap industry.

Lou, I'm glad you mentioned them. I just ordered their catalog.

 

[goldsilverpro]

Thinking back, I guess most of the stuff I bought from them in the past was for companies that I was working or consulting for, when I didn't care what I spent. When I had my last refinery, besides little things like drum pumps, I think the only thing I bought from them was an 18" dia. plastic vacuum filter funnel. I never cared much for it. The way it was designed, it was very tricky to get a good seal. However, it was a good brand (Bel-Art, I think) that was sold everywhere and U.S. Plastics had the best price. It was my fault for buying it.

I think a decent fume hood and scrubber can be easily homemade. There has already been more than adequate information on this forum to make both. My last refinery was located in a building in a scrap metal yard. Almost every major piece of equipment I used was made from stuff that came from that yard. I don't think that, compared with tailor-made high dollar equipment, anything was sacrificed. My 12' fume hood cost about $200 to make from lumber. It worked great. BTW, I never incinerated in that hood. The 2 standard steel squirrel cage blowers came from the scrap yard and were mounted in the top rear of the 7' high hood - it took 5 years for them to crap out.

I have had both high dollar and El Cheepo, and I really think I prefer the El Cheepo. I can design it to fit ME.

 

[4metals]

I was hired once by a guy who wanted to own a gold refinery and after I began working with his contractor I realized he never told me the whole story. Sure he wanted a refinery but he wasn't about to buy anything new, everything was bought at auction. In the end we had a high tech refinery with moderate capacity (3750 ounces of karat per week) for a lot less cash than I had imagined.

Shop the auctions, these days with companies closing and auctions gone internet there are great deals out there. Generally scrubbers and corrosion resistant blowers don't go for a lot of money, filter presses on the other hand always cost a bundle.

 

[LaurenceOs]

I wouldn't even know where to start... I think I may just have to do small bits outside with a fan going lol.

 

[4metals]

Actually it's pretty east to get into the auction bidding scene. Since you live close to a big city, Google commercial / industrial auctioneers in your area, check their websites for local auctions of industrial businesses. For refining stuff you should look for businesses that had electroplating shops and or labs. Within a week or 2 of the auction most sellers post pictures on line of everything they're auctioning off so you can browse to see if anything sparks your interest. They all have days when anyone interested can walk through and browse the equipment, so you can check it out in detail. Go, look you may see something you need. Auction prices are usually cheap, especially if nobody else is interested. You can usually pick up old computers and scrap at auction as well.
When you feel comfortable doing it you can begin to bid on equipment further from home, usually the photos are decent and you can get a good idea, after you have trained your eye on local stuff.

 

[2002valkyrie]

Hi all, Just reading about homemade hoods and scrubbers and me being a Noob I need to go cheap (talking lost my job and need to start with minimal investment in supplies other than the product and production). A hood and scrubber is in my opinion a must for safety and environmental responsibility. I have an idea for a small set up I will be starting and welcome any advice.

The breakdown of the attached pic.
2 plastic 55 gal drums. 1 on my table with a 2' x 2' square cut out also has 2" lip on bottom for spill catch. 2.5 flexible plastic pipe sealed in the top, leading to the bottom of the second drum also sealed. (Filled with Water 8" from top) A shopvac attached to the second drum's top and sealed.
I know the scrubber (2nd drum) has to have a caustic. Will ash work? And sliced round plastic bottles.
I just really am wanting to know that I will be o.k. with this set up till I know I will succeed and not put my self in debt for a refinery set up that I am not skilled enough at.

 

[LeftyTheBandit]

This is my set up currently used to handle my fumes from AR. 1L Erlenmeyer flasks, three rubber stoppers with two holes drilled into them, one rubber stopper with one hole drilled, 7 glass tubes to enter flask through rubber stoppers and poly tubing to connect the glass tubes.

I also use an aspirator pump to empty the last remnants of the gas through the caustic solution. Aspirator pumps use running water to create a venturi effect that creates a suction at the exit port. Total cost $75. 8)

 

[4metals]

Valkyrie,

Your shop vac just won't give you enough CFM to do any good. I like the cut off plastic drum, maybe if you use the drum with rigid pvc drain pipe, 4" and just above the hood add a true wye, which is a tee that enters at a 45 degree angle, and use a leaf blower to blow up. This will induce a vacuum and you will get exhaust. Just run the pipe over any roof lines to get the fumes away. The setup you drew will pull the fumes through the workings of the shop vac, and it will not last too long. The leaf blower is out of the air flow and fumes do not pass through it.

This will not neutralize any fumes, just remove the stinkies which escape the scrubber setup below which scrubs just the beaker where the reaction is going on. Very much like Lefty's

 

[2002valkyrie]

What can I use in the water to neutralize the fumes? I have a fine Doberman and neighbors and we all have too many cars (I'm setting up in my carport now).

 

[Noxx]

Caustic (Sodium Hydroxide), lime, H₂O₂ or simply water can work if used correctly.

 

[2002valkyrie]

What is the cheapest product? Can I use stove ash?

 

[4metals]

Valkyrie

The object of the scrubber is to neutralize the fume. Cheapest for you may be Lye. You do realize that a well designed scrubber with pumps and pH controls is only 80% efficient. That means coat your shop vac innards or you will destroy them. You also should realize that you want to get your fumes up, even after they come out of your home made scrubber, if your shop vac is on the ground next to your hood you will smell them.

 

[4metals]

How is the suction at the hood? It should draw smoke generated at the opening up and out efficiently.

 

[dick b]

I think he is trying to suck against 24"s of water column. That's much different than drawing air and fumes thru moist media. He needs to go back into this thread and get a better understanding of what the spray nozzles are for.

dickb

 

[eeTHr]

Val;

It works, but the beginning of the holes in the 4" pipe can't be more than an inch under the water or it will make too much suction inside the garbage can, and pull the sides in. It was drawing the air out of the end of the pipe, with no holes in it, with water about one foot up the pipe, but it nearly collapsed the Rubbermaid can.

The air flow will put out a bic lighter at the pipe opening inside the hood. I think that's enough flow to get rid of fumes. It's a 5.5 HP shop vac.

I'm thinking about some kind of reinforcement inside the garbage can.

I'm also wondering if the motor will overheat, because it doesn't look big enough to be a continuous duty motor, as it's very small for a 5.5 HP. I've seen one horse continuous duty motors that are bigger than it is.

I'll have to monitor the heat coming out of the separate cooling fan vent. I hope it has a thermal overload switch inside.

Tomorrow I'll try it in use. :?:

Don

 

[eeTHr]

I added more holes in the 4" down-pipe, at the same level, to increase flow and reduce the vacuum in the garbage can. It worked to some extent. Now the garbage can pulses like a beating heart, about two pulses per second. But it has good air flow at the hood.

The shop vac can take two filters inside, one cylinder shaped going into the impeller opening, and one bag type which feeds directly from the hose inlet and wraps around the inside of the vac. I put them both in.

I already had some holes drilled in the hood door, but now the air flow is more than with the 5" computer fan I used before, so I had to drill some more holes.

I ran it for 15 minutes and the motor fan outlet temperature was steady at 115 degrees.

I also put the box it came in over it to decrease the noise. I cut holes for the vac hose and power cord on one side, a hole for the motor fan outlet on the top and an opening for its inlet on the bottom, plus a hole for the vac blow outlet.

I ran it for two hours. Within the first couple of minutes the motor fan outlet went up to 110 degrees, and it stayed there the whole two hours just fine. I guess the box lowered the temperature by not allowing sunlight directly on the vac. (Air temperature was 74 degrees.)

Soon after I started the two hour run, the garbage can caved-in a bit, but the lid stayed sealed, so it worked for the two hours.

I need to drill yet more holes in the hood door, because there is still too much vacuum inside the hood (I noticed that when I had the door ajar a little, it sucked the fumes better). This should also help the can vacuum situation a little bit.

Now I need to install a 2" pipe that will take it up above the roof line.

I cooked some A/R at 190 degrees in there, and could smell it a little coming out of the vac blow hole, but it's nothing like when I used to cook it out in the open. Once it gets piped up above, and has a chance to dissipate, I don't think it will be a problem at all.

 

[2002valkyrie]

I cooked some A/R at 190 degrees in there, and could smell it a little coming out of the vac blow hole, but it's nothing like when I used to cook it out in the open. Once it gets piped up above, and has a chance to dissipate, I don't think it will be a problem at all.

That's great news! What did you mix in your drum as a caustic? I have added a 2 1/4" plastic fle pipe on the inside of the inlet port of my shopvac. Then buried it under 10lbs. of charcoal and before the air can enter the foam filter, I put a plastic coffee can over it so that there is a 1" gap it the top. May not last long but it can't hurt. I just need to get started. I am working on getting my exhaust elevated tomorrow.

I am trying to get everything ready to run so I can get started as soon as my melting dishes come in. Then I will be asking more questions on this forum.

 

[4metals]

Something rubs me the wrong way with sucking fumes through a shop vacuum, even with a scrubbing device in the line. I just don't think it will last for long. But some of what I've read here is good. Making a hood from a drum as Valkyrie did is a good cheap start, making the bottom of the door off the bottom by an inch or two is great for spill containment. I would exhaust fumes from the hood with a leaf blower as in the attached sketch. That will give good exhaust but a door that closes over the opening would be a good thing. I would use a hole saw and drill 3 or 4 inch and a half holes along the bottom of the door so air can get in with the door closed. If you get good flow from your shop vacuum you can use the exhaust side to blow up the pipe instead of a leaf blower.

Now there is no treatment of the fumes with this rig. The worst fumes, the red NO_x fumes, are the ones we really have to do something about. The bisulfite fumes from dropping the gold can be controlled by adding slowly in an open container and exhausting into open air without scrubbing, the fumes dissipate readily.

To handle the NO_x fumes I would exhaust the fumes out of a bucket with a bulkhead fitting towards the top edge connected to 2 erlenmeyer flasks and a vacuum eductor as described earlier.

Only the bucket for the reaction has to be in the hood, the flasks can be mounted outside the hood connected by a hose through the wall so they don't take up valuable hood space. The fumes will be better scrubbed this way and any fumes that leak out if you open up the top to see what is going on will be caught in the hood and pumped up and away from your face. When you change out the caustic from the scrubber flasks you can use it to treat your waste.