Interested in this Scrubber Design or a Simple Scrubber for Small Scale Refining

[AuggieDog]

I have been through the library and I guess I realize that my intelligence is highly over rated =) I am not "getting it" when it comes to scrubber design...AT ALL!
I do small scale refining of E-waste, of which I have a LOT to process (think years), but I like to keep things small when recovering. I process maybe an ounce or two, in a run. I am building a fume hood currently and that isn't too big a deal a for me as a former finish carpenter. My exhaust is 10in which will be scaled down to whatever I need. I do MOST of my refining directly in AR as I have learned that kovar capped transistors are just easiest to process this way (thanks Orvi!). They can however erupt in vigorous amounts of fumes which I really would like to at least make less toxic and harmful to the environment. But I also do nitric digestions, and am soon going to employ a sulfuric stripping cell (for a massive amount of RF connectors) as well.
I saw this idea on a thread in the library and I am interested in something like this. But the problem is I can't wrap my head around how do my fumes get through this system ??? and frankly, I am not comprehending the theories about scrubbing in general. But I need something simple, somewhat compact in size, and it just needs to be effective enough for someone like me that may be processing a small amount on the weekends.
Thanks in advance for all of your insights and wisdom and thanks for this great place to share it all!

 

[Yggdrasil]

I have been through the library and I guess I realize that my intelligence is highly over rated =) I am not "getting it" when it comes to scrubber design...AT ALL!
I do small scale refining of E-waste, of which I have a LOT to process (think years), but I like to keep things small when recovering. I process maybe an ounce or two, in a run. I am building a fume hood currently and that isn't too big a deal a for me as a former finish carpenter. My exhaust is 10in which will be scaled down to whatever I need. I do MOST of my refining directly in AR as I have learned that kovar capped transistors are just easiest to process this way (thanks Orvi!). They can however erupt in vigorous amounts of fumes which I really would like to at least make less toxic and harmful to the environment. But I also do nitric digestions, and am soon going to employ a sulfuric stripping cell (for a massive amount of RF connectors) as well.
I saw this idea on a thread in the library and I am interested in something like this. But the problem is I can't wrap my head around how do my fumes get through this system ??? and frankly, I am not comprehending the theories about scrubbing in general. But I need something simple, somewhat compact in size, and it just needs to be effective enough for someone like me that may be processing a small amount on the weekends.
Thanks in advance for all of your insights and wisdom and thanks for this great place to share it all!

This is just a part of isn't it?
The digestion reactor is not here?
Is this better understandable?

 

[Yggdrasil]

I have been through the library and I guess I realize that my intelligence is highly over rated =) I am not "getting it" when it comes to scrubber design...AT ALL!
I do small scale refining of E-waste, of which I have a LOT to process (think years), but I like to keep things small when recovering. I process maybe an ounce or two, in a run. I am building a fume hood currently and that isn't too big a deal a for me as a former finish carpenter. My exhaust is 10in which will be scaled down to whatever I need. I do MOST of my refining directly in AR as I have learned that kovar capped transistors are just easiest to process this way (thanks Orvi!). They can however erupt in vigorous amounts of fumes which I really would like to at least make less toxic and harmful to the environment. But I also do nitric digestions, and am soon going to employ a sulfuric stripping cell (for a massive amount of RF connectors) as well.
I saw this idea on a thread in the library and I am interested in something like this. But the problem is I can't wrap my head around how do my fumes get through this system ??? and frankly, I am not comprehending the theories about scrubbing in general. But I need something simple, somewhat compact in size, and it just needs to be effective enough for someone like me that may be processing a small amount on the weekends.
Thanks in advance for all of your insights and wisdom and thanks for this great place to share it all!

This one is slightly more evolved than my simple sketch, you can disconnect and reroute a flask at a time to either swap the liquid or do other jobs.
It sucks the gases through a train of flasks by vacuum.

 

[AuggieDog]

This is just a part of isn't it?
The digestion reactor is not here?
Is this better understandable?

View attachment 62510

OK, this is definitely easier to understand. In this design, is the NaOH dissolved in water? If so, at what concentration? Also, what would the "vacuum" look like? Would an inline blower work?

 

[Yggdrasil]

OK, this is definitely easier to understand. In this design, is the NaOH dissolved in water? If so, at what concentration? Also, what would the "vacuum" look like? Would an inline blower work?

You can use Peroxide in the first and regenerate some of the Nitric, and yes it has to be liquid. The empty bottle is to make sure nothing is sucked into the reaction bottle so if you run an "open" system (like the one showed) you can drop that.
Vacuum is best achieved with an e-ductor on a faucet or a water pump.
Or you can use any pump creating enough suction to move the gases through the system.
Preferably not a pump with metal in contact with the fumes.

Edit to add:
Concentration is not important , it just have to be sufficient to neutralize the acid fumes.

 

[4metals]

The way the fumes get into the flasks is by vacuum. There are a lot of valves on the system which may seem complicated but in reality it is quite simple. Let me explain what all of the valves do and then you will get it.

First off, the concept in the sketch posted by Ygg is exactly what is happening here with the added convenience of an ability to add fresh chemistry to each of the 3 flasks separately.

The valve on the upper left of the photo is where the fumes enter. This valve is normally open when operating the scrubber. In normal scrubbing mode, the top middle and top right valves are open too. Ignoring the other 3 lower valves (which are closed when scrubbing) and you have a simple straight flow through system as in Ygg's sketch.

In essence, if you want to do this simple, eliminate all of the valves, all 6 of them, and you will have the system Ygg posted. All of the valves are only necessary to easily add, by suction, chemicals to each individual flask.

For example to add chemicals to the first flask, shut off the top left valve so nothing is sucking in from the reaction. The other 2 top valves stay open so vacuum is in each flask. Next put the chemical you want to add to flask 1 in the beaker and put the tubing into that beaker and open the valve in the lower row in front of flask #1. This will suck liquid from the beaker and empty it into flask #1. When you have added the quantity you want added, remove the tubing from the chemical beaker and allow the air to suck in to clean out the tubing. You can replenish flask #2 or #3 the same way by opening only the valve in front of the flask you want to feed and closing the others in front of the flasks. The top middle and top right are always open and the top left is closed to maintain negative pressure when doing additions.

When back to operating the scrubber just open the top 3 valves, the middle and right are open already and, truth be told, I don't know why I added them to begin with as they always stay open. All 3 of the lower chemical feed valves are always closed when using the scrubber.

I had a 12 liter sealed reactor and this system handled the fumes coming off a 50 ounce karat dissolve easily. Since the glass flasks are clear it was easy to see the effectiveness of each flask by looking at the fume color.

 

[4metals]

When I used this system, the first erlenmeyer had water and peroxide, the second had caustic and water, and the third had caustic and water as well. THere was a 4th erlenmeyer flask which was a trap for liquids coming over and it was located very close to the venturi in the sink.

 

[andu]

Should I expect a solution saturated with caustic would work best long term and the stronger the peroxide more nitric will be recovered? Altho prices are similar here best i can get without concentrating it myself is 12% for peroxide and 10% for nitric (second site says 3%) but I can only find 60% nitric on this specific site. Nitrate is plentiful tho .

 

[goldshark]

The way the fumes get into the flasks is by vacuum. There are a lot of valves on the system which may seem complicated but in reality it is quite simple. Let me explain what all of the valves do and then you will get it.

First off, the concept in the sketch posted by Ygg is exactly what is happening here with the added convenience of an ability to add fresh chemistry to each of the 3 flasks separately.

The valve on the upper left of the photo is where the fumes enter. This valve is normally open when operating the scrubber. In normal scrubbing mode, the top middle and top right valves are open too. Ignoring the other 3 lower valves (which are closed when scrubbing) and you have a simple straight flow through system as in Ygg's sketch.

In essence, if you want to do this simple, eliminate all of the valves, all 6 of them, and you will have the system Ygg posted. All of the valves are only necessary to easily add, by suction, chemicals to each individual flask.

For example to add chemicals to the first flask, shut off the top left valve so nothing is sucking in from the reaction. The other 2 top valves stay open so vacuum is in each flask. Next put the chemical you want to add to flask 1 in the beaker and put the tubing into that beaker and open the valve in the lower row in front of flask #1. This will suck liquid from the beaker and empty it into flask #1. When you have added the quantity you want added, remove the tubing from the chemical beaker and allow the air to suck in to clean out the tubing. You can replenish flask #2 or #3 the same way by opening only the valve in front of the flask you want to feed and closing the others in front of the flasks. The top middle and top right are always open and the top left is closed to maintain negative pressure when doing additions.

When back to operating the scrubber just open the top 3 valves, the middle and right are open already and, truth be told, I don't know why I added them to begin with as they always stay open. All 3 of the lower chemical feed valves are always closed when using the scrubber.

I had a 12 liter sealed reactor and this system handled the fumes coming off a 50 ounce karat dissolve easily. Since the glass flasks are clear it was easy to see the effectiveness of each flask by looking at the fume color.

I am assuming you are drawing fumes directly from the beaker, and not scrubbing the fume hood air/gas mixture, with the above described setup. It would be reasonable to assume a fume hood would require a considerably larger system, then if one were to say use an Erlenmeyer style with a vacuum port, to be sucked through the various scrubbing chambers.

 

[goldshark]

You can use Peroxide in the first and regenerate some of the Nitric, and yes it has to be liquid. The empty bottle is to make sure nothing is sucked into the reaction bottle so if you run an "open" system (like the one showed) you can drop that.
Vacuum is best achieved with an e-ductor on a faucet or a water pump.
Or you can use any pump creating enough suction to move the gases through the system.
Preferably not a pump with metal in contact with the fumes.

Edit to add:
Concentration is not important , it just have to be sufficient to neutralize the acid fumes.

Sreetips uses a Harbor Freight vacuum pump for his filtrations. I think he neutralizes his solutions before filtering, so don't think he is sucking high concentration fumes directly through his pump. But his pump has lasted, I think 12-15 years of sucking on a flask. I'm sure some corrosion has occurred over this amount of time. The point being, a HF vacuum pump, through the properly sized, maintained, and chemically balanced scrubber flasks, should last for a while, on a small home lab scale. This would be much less polluting, then installing a fume hood to the environment only.

 

[4metals]

All modern fume scrubbers for refiners scrub the concentrated fumes coming off the reaction and not the entire exhaust of a refining hood. The cfm of a modest 48”
Wide hood with an 18” operating opening will require scrubbing 600 cfm. To maintain that airflow the packed section of the scrubber needs to be huge. Too big to be practical. A small 48” hood would need a 75 cubic foot packed section to maintain the 8 second retention time that renders the most efficient scrubbing.

By using drops and selectively scrubbing the concentrated NOx, a much more reasonably sized and less costly scrubber can be effective.

But do not overlook the general hood exhaust which protects the operator from fugitive emissions. You cannot have a scrubber and forego the hood. All of the seemingly tiny emissions from performing pouring operations, transfers, filtration, cementation, and many other things we do while refining need to be exhausted. Even waste solutions sitting in open pails emit fumes, albeit a small quantity. They add up and a workshop with just scrubber pickups and no general exhaust would quickly become a contender for the rustiest shop of the year.

 

[goldshark]

All modern fume scrubbers for refiners scrub the concentrated fumes coming off the reaction and not the entire exhaust of a refining hood. The cfm of a modest 48”
Wide hood with an 18” operating opening will require scrubbing 600 cfm. To maintain that airflow the packed section of the scrubber needs to be huge. Too big to be practical. A small 48” hood would need a 75 cubic foot packed section to maintain the 8 second retention time that renders the most efficient scrubbing.

By using drops and selectively scrubbing the concentrated NOx, a much more reasonably sized and less costly scrubber can be effective.

But do not overlook the general hood exhaust which protects the operator from fugitive emissions. You cannot have a scrubber and forego the hood. All of the seemingly tiny emissions from performing pouring operations, transfers, filtration, cementation, and many other things we do while refining need to be exhausted. Even waste solutions sitting in open pails emit fumes, albeit a small quantity. They add up and a workshop with just scrubber pickups and no general exhaust would quickly become a contender for the rustiest shop of the year.

Along these lines, but not relative to refining, was the discussion on another forum about what causes automotive battery corrosion; dissimilar metals, or a small amount of Sulphuric acid vapor leaking out of the breathers. Apparently the vapors corroded more then the metals reactivity series. I would like to see what GRF's opinion is.

 

[Yggdrasil]

Along these lines, but not relative to refining, was the discussion on another forum about what causes automotive battery corrosion; dissimilar metals, or a small amount of Sulphuric acid vapor leaking out of the breathers. Apparently the vapors corroded more then the metals reactivity series. I would like to see what GRF's opinion is.

As long as the poles are dry I have not seen any corrosion.
Sulfuric acid are probably one of the acids that has the least evaporation.
But batteries that has moisture on them will have corroding poles.

 

[AuggieDog]

TO EVERYONE

When I used this system, the first erlenmeyer had water and peroxide, the second had caustic and water, and the third had caustic and water as well. THere was a 4th erlenmeyer flask which was a trap for liquids coming over and it was located very close to the venturi in the sink.

How large do these flasks need to be?
Thank you for all your explanations, it is MUCH clearer to me now and I'm going to gather what I need to test my first system.

 

[4metals]

How large do these flasks need to be?

The flasks I used were 4 liters each. Today you can get Chinese made vacuum flasks in 5 liter size much cheaper than American made 4 liter flasks.

 

[anachronism]

Sreetips uses a Harbor Freight vacuum pump for his filtrations. I think he neutralizes his solutions before filtering, so don't think he is sucking high concentration fumes directly through his pump. But his pump has lasted, I think 12-15 years of sucking on a flask. I'm sure some corrosion has occurred over this amount of time. The point being, a HF vacuum pump, through the properly sized, maintained, and chemically balanced scrubber flasks, should last for a while, on a small home lab scale. This would be much less polluting, then installing a fume hood to the environment only.

One thing to note Goldshark if I may. I've been using a $200 HVAC pump for 6 years for my vacuums. I change the oil regularly and it hasn't missed a beat.

Edit for name.

 

[goldshark]

One thing to note Goldshark if I may. I've been using a $200 HVAC pump for 6 years for my vacuums. I change the oil regularly and it hasn't missed a beat.

Edit for name.

Thanks. I also, have heard changing the oil regularly, can add longevity to the unit, some people's opinion bases it on time spent under vacuum, others by the anum time scale. Been trying to find a spec on the correct oil. HF says to buy theirs, but am not near one, and just for posterity, want to know the spec, in case I already have some sitting around.

 

[Shark]

I have been using a Harbor Freight pump for around 5 years now. From what I found several years ago their oil is a low grade of glycerin, if I recall correctly. I have been using 5-20 motor oil for most of the years I have had mine.

 

[4metals]

I guess we should be more specific about the actual use for the vacuum pump. When driving a scrubber with vacuum, especially where you do not control the pH automatically with a pH controller and dosing pump, your vacuum pump will see some NOx. How much depends on you. For my money, and knowing how real life refiners center around "Damn, my vacuum pump burned out" vs. "The quarter is over time to do preventative maintenance!" I always preferred an eductor system. Powered by the right corrosion resistant pump they last for years.

When I lay out a refining room, I count a lot on vacuum, from powering a scrubber intake to filtration and acid dispersing. I like to know when you flip the switch, it sucks......literally!

 

[AuggieDog]

I guess we should be more specific about the actual use for the vacuum pump. When driving a scrubber with vacuum, especially where you do not control the pH automatically with a pH controller and dosing pump, your vacuum pump will see some NOx. How much depends on you. For my money, and knowing how real life refiners center around "Damn, my vacuum pump burned out" vs. "The quarter is over time to do preventative maintenance!" I always preferred an eductor system. Powered by the right corrosion resistant pump they last for years.

When I lay out a refining room, I count a lot on vacuum, from powering a scrubber intake to filtration and acid dispersing. I like to know when you flip the switch, it sucks......literally!

So 4metals, is an eductor system one that requires a source of flowing water? I am a little confused still about this. I just purchased an oil less vacuum and I am wondering if an eductor can be used with it?
Edit: Ok I think I see how these systems would work with a water pump. I don't think I have the means to set up a system like this.