# Semi closed vacuum scrubber design



## autumnwillow (Nov 12, 2015)

The planned scrubber setup will be processing inquarted gold using nitric acid and refining gold in aqua regia.

This is actually 4metals design but I don't plan to use a closed system but rather use a pvc funnel instead.
The first and second filtering flasks will contain H202/water and the last one will contain sodium hydroxide/water.

The filtering flasks will only be 2liters, how much can I process with it?
The vacuum pump will be a 10 cfm, will this be enough for the funnel to suck up the fumes?
Is the condenser necessary to help scrub the fumes?
Should I use an air stone instead of drilling holes in the pvc pipe? I'm worried that the air stone might get clogged.
I am also worried about the temperature, at how long can I use this setup?

I will build a fume hood after this one and an NaOH scrubber with an eductor (based on 4metals design) with a venturi inlet for the fumes but I would need time to do this so I will stick with this setup first.

Forgive my drawing =(


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## rickbb (Nov 12, 2015)

I don't think the condenser is necessary, that's what you are doing by bubbling the gas through the water especially if you put them in a tray of ice, but won't hurt one bit. If you do use the condenser, make sure it's angled down so any liquid it collects will run out.

As to whether the 10CFM vacuum is enough, depends on the beaker size, how much water you are pulling the gas through and volume of gas you will be generating. You can easily test this before you run a batch with just air. If it pulls the air through and bubbles well in all 3 water bottles, then I'd pronounce it good to go.

I'd skip the air stone, will make the vacuum work to hard to draw through it.


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## geedigity (Nov 13, 2015)

Is the pump a disposable one? The reason I ask is that, even after you scrub the fumes, there will be some acidic content to the air being pulled through the pump. 

The longer the fumes are in contact with the scrubbing solution the better, so in reality, an air stone may help somewhat. I use two, 1 meter long, 4" PVC tubes with air stones in each, setup in series to scrub. Even with that setup, the fumes are not 100% absorbed by the scrubbing solution.


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## autumnwillow (Nov 13, 2015)

geedigity said:


> Is the pump a disposable one? The reason I ask is that, even after you scrub the fumes, there will be some acidic content to the air being pulled through the pump.
> 
> The longer the fumes are in contact with the scrubbing solution the better, so in reality, an air stone may help somewhat. I use two, 1 meter long, 4" PVC tubes with air stones in each, setup in series to scrub. Even with that setup, the fumes are not 100% absorbed by the scrubbing solution.



No, the pump is a robinair 10 cfm 1/2hp pump. I think it is either made of steel or aluminum. See here: http://www.robinair.com/products/vacumaster-118-lpm-vacuum-pump-220v50hz

I do think that this pump won't probably last a year, but by that time I would already have a big scrubber system. Maybe when this vacuum pump starts to fail I can have the internal parts customized to use polypropylene materials.

I guess I have to go with a condenser and an air bubbler. Do you use any packing media?


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## kurtak (Nov 13, 2015)

Scrubber :arrow: http://goldrefiningforum.com/phpBB3/viewtopic.php?f=40&t=19965&p=205108&hilit=scrubber#p205136 --- read from this point down rest of thread

Mine is just a smaller version of Phil's - I have been running mine with a 2.5 CFM harbor freight vacuum pump for more then a couple years & it still works fine (has not been destroyed by acidic fumes)

10 CFM is a LOT of suction & is going to want to suck the fumes through the peroxide &/or sodium hydroxide faster thereby giving it less retention time to scrub the fumes so your scrub columns need to be larger to hold more peroxide &/or sodium hydroxide --- or you can put a bleeder valve in line to bleed off some of the vacuum there by adjusting the vacuum up or down depending on how much you open or close the bleeder valve 

This shows Phil using his with the funnel over the top of a beaker :arrow: http://goldrefiningforum.com/phpBB3/viewtopic.php?f=40&t=18481&hilit=scrubber&start=30#p189866

Marbles work good as a media to defuse the bubbles & give more retention time in the scrubber

Kurt


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## MarcoP (Nov 13, 2015)

Since I'll be processing relatively small lots, I think I will do great with 4 polypropylene gas washing bottles I've got off ebay at a very good price, try to look at those, eg.:







Acid peroxide I believe to be useful only when dealing with nitric acid as it will create back nitric, thus diluted. Otherwise sodium hydroxide will be the only one needed. I think I would go with two bottles with 35% acid peroxide and the remaining two with sodium hydroxide. Or use the last with plain water to monitor the PH.

My original idea was to "push" air into a closed reaction vessel and send the fumes into two washing bottles with H2O2, two with NaOH and a last common bottle with water to monitor the PH. Dave, FrugalRefiner, I remember advising me about possible leaks being "push out" the reaction vessel, but vacuuming air from the vessel would actually seal it better. Pushing air will make it possible to use a last bottle with water to monitor the PH while vacuuming will eliminate this possibility.

Marco


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## autumnwillow (Nov 14, 2015)

Hmm. I wanted to buy a 10cfm vacuum pump because it will not really be a closed system, but rather I'll be using an upside down funnel on top of the beaker. Will a 5cfm vacuum be enough to suck the fumes for this? Or am right with going for a 10cfm rated pump?

On second thought, I think I would go for a 4 litre suction bottles since they are cheaper than using a pyrex filtering flask.


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## autumnwillow (Nov 18, 2015)

Air Vacuum pump price: $400
Magnetic Liquid Chemical Pump: $750

I was thinking if I could just buy the Magnetic Liquid Chemical Pump and create a venturi instead, I won't be wasting a vacuum pump since its internals will most likely corrode in a year.

Is it hard to get a good suction out of DIY venturi using pipes?


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## rickbb (Nov 18, 2015)

autumnwillow said:


> Is it hard to get a good suction out of DIY venturi using pipes?



Venturi's are easy to get working on vacuuming air, pulling air though a series of liquids may be a bit harder but should be doable.


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## Barren Realms 007 (Nov 18, 2015)

autumnwillow said:


> Air Vacuum pump price: $400
> Magnetic Liquid Chemical Pump: $750
> 
> I was thinking if I could just buy the Magnetic Liquid Chemical Pump and create a venturi instead, I won't be wasting a vacuum pump since its internals will most likely corrode in a year.
> ...



You can find a vacum pump on ebay for a lot less and should last you a long time.

http://www.ebay.com/itm/3CFM-1-4HP-Rotary-Vane-Deep-Vacuum-Pump-HVAC-Tool-Air-AC-R410a-R134-Refrigerant-/190891880406?hash=item2c720aefd6:g:U4oAAMXQxKxSHdK2#ht_3180wt_1128


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## rickbb (Nov 18, 2015)

rickbb said:


> autumnwillow said:
> 
> 
> > Is it hard to get a good suction out of DIY venturi using pipes?
> ...



I just remembered that years ago, (decades actually), when I was in the printing business we used Venturi's to draw a vacuum on large format exposure systems. They used clean, dry air compressed at 100psi and they would pull a large film or plate frame, (60" x 80") down to 28 inches of Hg in just a couple of minutes. Mechanical pumps would take 10 or 15 to do the same job. Made lots of noise though, lots, everyone complained so we had to add a muffler system to it.


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## autumnwillow (Nov 19, 2015)

Barren Realms 007 said:


> You can find a vacum pump on ebay for a lot less and should last you a long time.
> 
> http://www.ebay.com/itm/3CFM-1-4HP-Rotary-Vane-Deep-Vacuum-Pump-HVAC-Tool-Air-AC-R410a-R134-Refrigerant-/190891880406?hash=item2c720aefd6:g:U4oAAMXQxKxSHdK2#ht_3180wt_1128



It would cost me three to four times the price of that vacuum pump to have it shipped here in my country.

I think I need to change my plan. I believe my previous plan is inefficient and will break a $400 equipment.

I'll be using pvc drums instead packed with bio balls and ceramics. 
A sprayer (drilled pvc tube end caps) and an eductor that would connect to one 3L suction bottle filled with H202/water which then connects to a manifold inside the fume hood.

My problem is with the magnetic pump. The chemical magnetic pump offered to me has only 12 meters of head which translates to only about 17 psi. Assuming other losses from height, fittings and pipe length that would only be around 10 psi of pressure. 
Am I correct that this pressure will not be sufficient for the spray nozzles (I plan to use three in a triangular shape) and for the eductor to work?

There is a 1.7kw chemical pump, but the power supply is in 3 phase and its very expensive. 
Should I just buy a normal centrifugal pump? 
A 1-2hp will just cost me around $300 but how long will this machine last?

I'll try to draw a sketch of my design and post it here.


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## MarcoP (Nov 19, 2015)

autumnwillow said:


> Air Vacuum pump price: $400
> Magnetic Liquid Chemical Pump: $750
> 
> I was thinking if I could just buy the Magnetic Liquid Chemical Pump and create a venturi instead, I won't be wasting a vacuum pump since its internals will most likely corrode in a year.
> ...


With the same budget I would definitively buy a second hand chemical resistant Laboport pump.

Marco


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## Smack (Nov 19, 2015)

Get a micro vacuum pump, way cheaper and plenty of vacuum power for lab work. Buy 2 so you have a backup pump.


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## autumnwillow (Nov 20, 2015)

DC micro vacuum pumps made of polypropylene are only $20. I am not sure that is up to the job of getting around 10cfm suction to a 3L suction cup with h202/water then to the NaOH scrubber drum.

I have found an eductor. Seems up to the job. Now my only problem is the pump.
In 4metals thread he recommended a 1/32hp chemical pump. With that power, can it create a suction out of this venturi?

My supplier is offering me a 1/4hp polypropylene magnetic pump. I'm worried about the pressure that it can give. Its expensive so I don't want to put it to waste.

Actual pump specs. I believe I need at least 40psi to get a good suction out of the eductor. I am having trouble understanding/converting the specs given to psi rating, maximum height of my scrubber system will only be about 2-3 meters. 



> Max. Capacity :	135 l/min
> Max. Head :	12 m
> Standard Liquid Capacity	:	70-9 l/min-m
> Connection Type :	Hose 25mm
> ...


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## kurtak (Nov 20, 2015)

autumnwillow said:


> I'll be using pvc drums instead packed with bio balls and ceramics.
> A sprayer (drilled pvc tube end caps) and an eductor that would connect to one 3L suction bottle filled with H202/water which then connects to a manifold inside the fume hood.
> 
> My problem is with the magnetic pump. The chemical magnetic pump offered to me has only 12 meters of head which translates to only about 17 psi. Assuming other losses from height, fittings and pipe length that would only be around 10 psi of pressure.
> ...



This sounds more like the type of scrubber you would build (bio balls & spray bar) to deal with the fumes drawn through a fume hood vented with a hood blower rather then a scrubber designed to deal with fumes drawn directly off a reaction vessel needing to be scrubbed

So I have to ask - what are you trying to do - scrub fumes directly off a reaction vessel - or fumes from a fume hood 

Your OP sounds like you want to scrub fumes directly off a reaction vessel - if so ------

then follow the instructions for making a scrubber as described by 4metals, Phil & my self in the link I already posted (which I see 4metals has now added to the library)

NOTE; - all 3 of us are using a vacuum pump that operates at "ONLY" 2.5 - 3 CFM --- running a vacuum pump that operates at high CFM will mean you need "MUCH" larger scrubber columns filled with "MUCH" more H2O2 &/or NaOH in order to get the needed retention time for the H2O2 &/or NaOH to scrub

In other words - the more CFM you are pulling (vacuum) the larger the volume size your scrub columns need to be in order to allow retention time to effect proper scrubbing (you keep talking 10 CFM)

NOTE; - 4metals little scrubber made with vacuum flasks with a 3 CFM vacuum pump is being used to scrub fumes from a 12 liter reaction vessel 

NOTE: - Phil is using his with a funnel over the top of a beaker (as you asked about in your OP) & he is running a 2.5 CFM vacuum pump

I use mine on 5 gallon buckets (with a "small" vent hole drilled in the lid to keep the bucket from collapsing) my vacuum pump is only 2.5 CFM (though I also have a 3 CFM pump as back up - just have never needed to use it as the 2.5 pump is still working after 2 years of scrubbing with it) 

Stop trying to reinvent the wheel - go with what is proven to work - READ the thread I provided a link to --- The whole tread :!: 

here it is again :arrow: http://goldrefiningforum.com/phpBB3/viewtopic.php?f=40&t=19965&hilit=scrubber

Kurt


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## autumnwillow (Nov 20, 2015)

Kurt,

I am still thinking whether I should go for the full scrubber system or the vacuum type that was originally designed by 4metals.
I am just comparing the cost effectiveness of setting up a vacuum type between a full scrubber system. I actually have a notebook full of drawings, indicating costs, setup time and its purposes. 

To say that I am re-inventing the wheel. I think that may be true.

What I'm trying to do is a full scrubber system that can do the following:
1) Scrub incineration fumes, cupellation fumes, anything that has to do with fire will be in a stainless steel box along with a cyclone dust seperator on top plus a seperate blower that takes air from the atmosphere to lower the temperature of the fumes.
2) Using an eductor, I will be able to generate a vacuum. My problem was the available chemical pumps have low head (low pressure). I just solved this today by using multiple external pond water pumps connected in series would add up their head capacity, thus increasing the pressure.
3) Recover nitric acid, destroy cyanide solutions and help with the scrubbing of aqua regia fumes. All of which will have a seperate reaction vessel for each along with a pvc valve that I could close/open. So if I were using nitric acid on inquarted gold, I would just open the valve for the nitric recovery reaction vessel. This is where the vacuum of the eductor would take part.
4) The scrubber system will be both connected to the fume hood and incinerator, a 6" pvc ball valve that I could close/open if I don't use the incinerator or fume hood. This design will allow any fumes escaping from the closed reaction vacuum setup design to simply go thru the scrubber.

It may be hard to understand without the drawing but when I finish it I'll post it here on a separate thread, its either I go with the closed system vacuum setup or my re-invented scrubber setup.

Thank you for your time, I really appreciate it.
And I am sorry for the confusing posts. It is true that some my posts are no longer related to the topic of the thread.


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## rickbb (Nov 20, 2015)

If you want to use a venturi setup then you need a blower or air compressor, not a vacuum pump. That puts the air source in front of any fumes so it does not need to be non-corrosive.

Venturi's create vacuum by decompressing air, (or a liquid), in front of a smaller opening drawing air from the smaller opening into the larger chamber where the air is rapidly decompressed. 

So you need compressed air to begin with. Either an air compressor or a pre-chamber in the venturi that compresses the air just before it enters a larger chamber to be decompressed.

I'm confused by your use of a chemical/pond pump. Why are you wanting to create a vacuum in a liquid to scrub gases, (air)?


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## autumnwillow (Nov 20, 2015)

rickbb said:


> If you want to use a venturi setup then you need a blower or air compressor, not a vacuum pump. That puts the air source in front of any fumes so it does not need to be non-corrosive.
> 
> Venturi's create vacuum by decompressing air, (or a liquid), in front of a smaller opening drawing air from the smaller opening into the larger chamber where the air is rapidly decompressed.
> 
> ...



Because you told me that it was noisy. I do not want a noisy lab but I might consider it to save on costs, a silent compressor is definitely cheaper than buying 3 pumps.


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## Smack (Nov 21, 2015)

Smack said:


> Get a micro vacuum pump, way cheaper and plenty of vacuum power for lab work. Buy 2 so you have a backup pump.



I thought you were talking about a vacuum pump for filtering like through a Buchner into a vacuum flask.


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## kurtak (Nov 21, 2015)

autumnwillow said:


> It may be hard to understand without the drawing but when I finish it I'll post it here on a separate thread, its either I go with the closed system vacuum setup or my re-invented scrubber setup.
> 
> Thank you for your time, I really appreciate it.
> And I am sorry for the confusing posts. It is true that some my posts are no longer related to the topic of the thread.



though I "think" I understand your idea as you explained it in righting I can't quite visualize it so yes a drawing would be really nice before I comment further

Pease keep it "all" posted here in this thread because it is "all" related to the topic of this thread

You started out asking about scrubber design & we are still talking about scrubber design - we are just talking about different variations/options in design to figure out what will fit your needs & work for you - so its better to keep it all in the same thread thereby keeping the thought process of working the design out consolidated in one place for future information & referencing to other members

will wait to see your drawing

Kurt


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## autumnwillow (Nov 23, 2015)

Here are the drawings.

The drums are pvc blue drums they are resealable for ease of cleaning and dosing.
They are slightly tilted on purpose so as to make the water flow easier to drain.

All large pipes will either be 6" or 4" diameter. All small pipes are 1" in diameter.

I think that the 1st eductor(top left part) should not be connected to the water, I just think that the sprayers wont work because of the pressure. Any thoughts?

The base to support the structure will either be pvc pipes or marine plywood.


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## kurtak (Nov 23, 2015)

no, No, NO

And that is what I thought - you are trying to incorporate 3 systems - each of which is "supposed" to preform a specific task - into a single system to preform all of the tasks

In other words you are trying to incorporate a vacuum system --- with an air "pushing" blower system --- with an air "drawing" blower system --- & expecting that you can control which function you want the system to preform simply by opening &/or closing certain ball valves --- it NOT going to work --- you NEED to have a system - each its own - designed to preform its task - based on system working requirements --- meaning ----------

A vacuum system NEEDs to be a vacuum system "working on its own"

An air pushing system NEEDs to "working on its own" at pushing air

An air drawing system NEEDs to "working on its own" at drawing air

You are WAY over complicating things here AND there are many things that can & WILL go wrong with the system you have drawn out & there is no way I am going to try to explain it all

You want a system to scrub "heavy fuming" that occurs during full blown reactions - follow the instructions provided for building a "vacuum" scrubber to be used for this task - this can be done cheap & simple

Then - make a scrubber for your fume hood - this can also be done cheap & simple - if you need help with it ask & I &/or others will help with it

Then - build a "bag house" system for your incinerator (&/or melting/smelting set up) this can also be done cheap & simple - if you need help with it ask & I &/or others will help with it 

This will make your systems (each there own) fail safe --- the system (all in one) you have drawn out - is not fail safe

Also --- I see you have included cyanide treatment into the same system that is treating acids - that is a very, VERY bad idea - cyanide & acid should NEVER be worked with in the same system --- keep them COMPLETELY separate - or you may not live to tell us about it

Kurt


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## autumnwillow (Nov 23, 2015)

Oh well, back to the vacuum setup then. Thanks for the advice. I knew there could be something wrong with this setup. Especially now that I am pumping compressed air in the setup.

Can I at least use the wet scrubber for both my incinerator and fume hood (without any eductors)? The baghouse concept I think is covered by the cyclone separator.
My incinerator will also be the place to melt gold, cemented silver, etc. I believe some of the chemicals like nitrates can have a small ppm in it or lets say a small amount of silver chloride, so exposing it to just a baghouse will not completely treat it.


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## MarcoP (Nov 24, 2015)

Kurt said:


> Then - build a "bag house" system for your incinerator (&/or melting/smelting set up) this can also be done cheap & simple - if you need help with it ask & I &/or others will help with it


If it won't go off thread I would like to know more, please. My gas-fired pyrolysis reactor is ready but never fired up, excluding small tests, it includes a coke-fired after burner too.

Marco


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## kurtak (Nov 24, 2015)

autumnwillow said:


> Can I at least use the wet scrubber for both my incinerator and fume hood (without any eductors)? The baghouse concept I think is covered by the cyclone separator.
> 
> 
> > The short answer is yes - The question is whether or not doing so is your best option
> ...



No it wont go off thread to discuss it here - the thread may have started asking about "vacuum scrubber design" but it has evolved into discussion of fume control in general so I think we can continue the course it is taking --- if the mod's then decide to split (as it evolves) it they can certainly do so

For the next couple (few) days I am going to be busy so it may be a few days before I get back to posting more info

Kurt


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## autumnwillow (Nov 26, 2015)

kurtak said:


> You are WAY over complicating things here AND there are many things that can & WILL go wrong with the system you have drawn out & there is no way I am going to try to explain it all



I did my research and I won't use the vacuum scrubber vessels for cyanide destruction, I would use caustic and bleach instead.

Assuming that I will get a higher head pump that can draw an air vacuum on the eductor.
Would you kindly enumerate some of the things that could go wrong?


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