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

[Yggdrasil]

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?

You do not use an eductor with a vacuum pump, the eductor is the vacuum pump.
Don't you have Google??
You can use a pump in a closed system to run the eductor, like a 200L barrel or similar and just pump the water through the eductor back into the reservoir.

 

[Yggdrasil]

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.

Here is an example:
https://www.amazon.com/Nalgene-6140-0010-Aspirator-Polypropylene-Threading/dp/B003OBYNBO

Hard to find non metal ones now.

 

[4metals]

is an eductor system one that requires a source of flowing water?

Yes, recirculated water is typically used although they make small lab eductors that connect to a water faucet.

 

[CrystAG]

I dont want to add to any confusion but you have me thinking whether i have my scrubber set up backwards.
Like the OP, I am comfortable with small scale digestions in the 1ozt range but opted for a system operating under slight positive pressure rather than vaccum.
As per the image, the reaction vessel has incoming airflow of a few cc's a second. This appears to help the Nox through the scrubbers at a slow controllable rate. The first dreschel bottle is sacrificial to prevent suck back. The subsequent 3 contain 20% KOH and ceramic bump chips to increase surface area and make the gas throughput as tortuous as possible.

Did i get this badly wrong?

Typically i add some universal indicator to the gas wash bottles to visually cue me when the scrubbing Ph is decreasing.

Is vacuum the way to go?

 

[Yggdrasil]

I dont want to add to any confusion but you have me thinking whether i have my scrubber set up backwards.
Like the OP, I am comfortable with small scale digestions in the 1ozt range but opted for a system operating under slight positive pressure rather than vaccum.
As per the image, the reaction vessel has incoming airflow of a few cc's a second. This appears to help the Nox through the scrubbers at a slow controllable rate. The first dreschel bottle is sacrificial to prevent suck back. The subsequent 3 contain 20% KOH and ceramic bump chips to increase surface area and make the gas throughput as tortuous as possible.

Did i get this badly wrong?

Typically i add some universal indicator to the gas wash bottles to visually cue me when the scrubbing Ph is decreasing.

Is vacuum the way to go?

Gases and liquid will always go the easiest way, so with pressure you have no control.
With vacuum it follows and things do not need to be air thightbat the reaction vessel.
This in turn allows you to open and add or subtract in the reaction vessel.

 

[CrystAG]

Gases and liquid will always go the easiest way, so with pressure you have no control.
With vacuum it follows and things do not need to be air thightbat the reaction vessel.
This in turn allows you to open and add or subtract in the reaction vessel.

Thanks for the wisdom once again. Gives me another avenue to consider. I agree that an air tight reaction vessel is limiting when it comes to additions etc on the fly.

I figured if i can get the gasses to quench for long enough this setup should do fine. I can slow the air flow to a degree that the bubbles keep the gases in contact with the KOH for approx 8 seconds spread over the 3 gas washing bottles.

Exploring a vacuum setup should be a fun project to get into.

Thanks again.

 

[Acidrain]

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.

What did you use for the reaction vessel?

 

[4metals]

What did you use for the reaction vessel?

When I used this setup a was using a 12 liter conical head reactor with a 4" neck. This allowed the mounting of a condenser and direct connection to the scrubber feed. If one had to go out and pay for that setup today the cost is prohibitive.

Best suggestion is a beaker with a pickup where the pouring lip allows an opening under the watch glass, with the tubing resting in that pour slot. Or a simpler option is an inverted funnel over the beaker.

simple is better.

 

[Acidrain]

When I used this setup a was using a 12 liter conical head reactor with a 4" neck. This allowed the mounting of a condenser and direct connection to the scrubber feed. If one had to go out and pay for that setup today the cost is prohibitive.

Best suggestion is a beaker with a pickup where the pouring lip allows an opening under the watch glass, with the tubing resting in that pour slot. Or a simpler option is an inverted funnel over the beaker.

simple is better.

Could a boiling flask or vacuum flask be used?

 

[4metals]

Could a boiling flask or vacuum flask be used?

Depends on what you are refining. I always ran karat or chemical stone removal lots so the ability to get your hand into the vessel to clean it out and recover diamonds which can stick to the glass and not come out easily. So a conical head sealed reactor was easy to remove the head and get into as was a beaker.

But if you are doing karat scrap or foils or something that can fit into the small neck and there is no fear it won't dissolve completely a boiling flask or erlenmeyer can work.

I never liked aqua regia reactions in an erlenmeyer flask because as a reaction rises, sometimes faster than expected or desired, the narrowing circumference of an erlenmeyer as the liquid moves up accelerates the rate. The vision of a volcano erupting is a good analogy. It happens, I've seen it, so I don't recommend erlenmeyers for aqua regia reactions.

 

[Acidrain]

Depends on what you are refining. I always ran karat or chemical stone removal lots so the ability to get your hand into the vessel to clean it out and recover diamonds which can stick to the glass and not come out easily. So a conical head sealed reactor was easy to remove the head and get into as was a beaker.

But if you are doing karat scrap or foils or something that can fit into the small neck and there is no fear it won't dissolve completely a boiling flask or erlenmeyer can work.

I never liked aqua regia reactions in an erlenmeyer flask because as a reaction rises, sometimes faster than expected or desired, the narrowing circumference of an erlenmeyer as the liquid moves up accelerates the rate. The vision of a volcano erupting is a good analogy. It happens, I've seen it, so I don't recommend erlenmeyers for aqua regia reactions.

Thank you very much for the advice! You just saved me from buying unnecessary glassware

So obviously, there is no need for a condenser then? Just capture the fumes and suck them through the scrubber?

 

[4metals]

So obviously, there is no need for a condenser then? Just capture the fumes and suck them through the scrubber?

A condensed reaction allows you to go from a 3:1 aqua regia ratio to a 4:1 ratio because it recycles enough nitric to increase the efficiency. They work best in vessels like this.

 

[Acidrain]

A condensed reaction allows you to go from a 3:1 aqua regia ratio to a 4:1 ratio because it recycles enough nitric to increase the efficiency. They work best in vessels like this.
View attachment 62711

That's a nice set-up! Way out of my league though.