scotthensler5810
poorman5810
I’m building a fume hood for gold/silver refining. I would like to know if I’m using Nitric concentrate 67% to 70% or Sulfuric Acids, what cfm air flow would be needed for this?
Yeah, I figured this out after the fact. Biggest reason I'm moving it is I need the space so I can set up an assay lab and jewelry studio. Assay hood will be tiny and blower will be set up with a VFD so I can seal it up tight and just keep a negative pressure on it.Make up air always helps but refineries are always hot in summer and cold in the winter. Making a hood like this helps.
making a hood with a plain steel blower
Air intake from outside the refining space exhausts less CFM from the workspace.
I once saw an axial flow fan intended for aggressive extraction use at a second hand goods store, almost brought it for later use. It had heavy epoxy coating on all the exposed metal and a plastic impeller. I expect such professional fans are available for a price.Just curious to see if an effective fume scrubber could be built using course Limestone contained within a plastic pipe. Putting the blower on the vent (out) side to induce suction through the Limestone column. This would leave the blower at a greatly reduced exposure to corrosive elements. Engineering would dictate size needed for volume desired obviously. Just thinking out loud.
While this is always true, the more remote your location is the necessity of fume scrubbing decreases. The US EPA will grant a “de minimus” status to a small generator using less than 10 pounds of Nitric Acid a day. For most here that is a lot of nitric. To be granted this status you have to be a commercial operation and apply for the exemption. There is a caveat in the rule. Even if you are under the 10 pounds per day limit, if a neighbor complains you will need to scrub the fume.You need scrubbing to remove toxic gases before venting outside.
What kind of sealant is use to seal the seams in a fume hoodHere in the US, hood exhaust is called fugitive emission because the only bad fumes the blower sees is what escapes the scrubber or is emitted when you pour acids or do general in hood tasks. Don't make the mistake of going too small, make a hood with an opening at least 4 feet wide and 3 feet tall. You will not regret the space that hood will afford you. For a hood with a 4 foot by 3 foot opening, you should exhaust 1200 CFM. A little trick which will allow a blower half this size is to make a "face shield" out of plexiglass that folds up and out of the way when you need full access. The face shield is the full width of the hood and when down it usually hangs about 18" down from the top. It allows plenty of room for tasks to be accomplished with your hands under the shield working in the hood with your face behind the plexiglass. In addition to protecting you from splash, it effectively halves the exhaust requirement because with the shield down, the opening is now 4 feet by 1.5 feet or only requiring 600 CFM.
There are 2 schools of thought about blowers. One is use a cheap plain steel blower that you spray a resistant spray paint through to crudely coat the inside and when it craps out you replace it. The other school says get a corrosion resistant blower, much more costly. A third option is a blower made for high humidity which is usually plastic. They are better than coated steel but not as good as a true corrosion resistant fan.
But keep in mind you will need to address the corrosive fumes because, unless you. have a corrosion resistant blower, they will eat the blower. That is where a scrubber comes into play.
That depends on what material the hood is made from.What kind of sealant is use to seal the seams in a fume hood
I’m using frp panels on luan so a chemical resistant silicone will workThat depends on what material the hood is made from.
PVC is welded
Fiberglass uses fiberglass resin
Plywood uses a good epoxy sealer and silicone. I wonder how flex seal would hold up to the acid fumes.
https://flexsealproducts.com
Any members have first hand experience with flex seal?
Enter your email address to join: