# New fume scrubber design



## 4metals

I have been following the thread on building a hood and a scrubber for a long time now and it has gotten pretty long. This scrubber works on a different principle than the one in that thread and was inspired by a client of mine who didn't want to spend the money on a good vacuum system and a good scrubber, but he needed both.

I had posted a thread on building a vacuum system How to build a vacuum filtration system some time ago and it is the type of system required for a strong, commercial operation. Usually refiners processing 100 oz plus lots will benefit from the system.

This scrubber uses a feed similar to the vacuum system and is based on the principle that the eductor pulls air through the venturi and in addition to creating a vacuum, it pumps the air it pulls. By pumping that air into an air tight scrubbing chamber the fume has no place to go but along the airpath and through the scrubber. Plus with a 10 CFM eductor, the time the fumes remains exposed to your scrubber chemistry is exceptionally long for an effective reaction. 

As a bonus to this design by using the exhaust over a sealed reactor, 100 ounce digestions are completely handled by the 10 cfm flow. A side bonus is that by shutting off the feed line that pulls air for scrubbing and opening up a line set up to vacuum filter, you can filter and scrub fumes with the same piece of equipment, just not at the same time.


This setup can be pH controlled automatically or for a small shop, daily opening the access port to adjust the pH should suffice. The principles of scrubbing are the same, as is the packing but for someone digesting 100 ounce lots, this system is effective. 

Now it's time to have our DIY crowd tear into this design to see what we end up with.


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## Barren Realms 007

A couple of quick question's. 

We use to use a corkscrew type spray nozzel are you useing something similar to produce your spray pattern? Or are you useing something home made?

Where your piping from the pump comes down the inside of the tower is it connected where you have it labeled as the inductor(where the piping color changes from red to blue) to force your fumes into the bottom tank and then thru the stack? That is kind of what I am gathering from the picture.

Do you seem to run into any kind of restriction in air flow with the pipeing (red) so far into your solution?

I'm guessing that you have a seperate support system holding up the stack and the tank is not what is supporting the stack but just sealed off where they connect. 

I'm guessing where the tank and stack come together is plastic welded or have you used some sort of sealent.

Nice desighn. 8)


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## 4metals

> We use to use a corkscrew type spray nozzel are you useing something similar to produce your spray pattern? Or are you useing something home made?



corkscrews are fine they provide a good distribution and do not clog easily.



> Where your piping from the pump comes down the inside of the tower is it connected where you have it labeled as the inductor(where the piping color changes from red to blue) to force your fumes into the bottom tank and then thru the stack? That is kind of what I am gathering from the picture.



The way an eductor works is it compresses the water running down along the column (blue) through a small orifice just before the red line comes in from outside the scrubber. When the water expands after the orifice it draws a vacuum, so the red line going into the liquid level is a mixture of water and air used to pull a vacuum. 



> Do you seem to run into any kind of restriction in air flow with the pipeing (red) so far into your solution?



The reason the pipe extends beneath the liquid level is so when you are using it in vacuum mode, you will hold a stronger vacuum. If it was not submerged, the vacuum that builds up in the vacuum jug would overpower the suction and the thing would burp. The weight of the water keeps that from happening. 



> I'm guessing that you have a seperate support system holding up the stack and the tank is not what is supporting the stack but just sealed off where they connect.



The stack is welded to the tank to be airtight, in this case the weight of the column was supported externally in a way not indicated on the drawing, otherwise it would need support by running to the bottom and drilling large holes to allow the airflow to ascend.


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## Barren Realms 007

That was what I figured you did where the stack connectd to the tank. If not I would have set it up like you said with the stack going to the bottom of the tank.

Ok I see what you are doing. I have used a similar system with water to remove sand from pool filters so I know what you are doing now. It's amazing the things you forget as time goes by. Thanks


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## qst42know

The blue horizontal line, the arrow isn't indicating the direction of flow is it?

Is this similar to what your drawing depicts?

http://www.nciweb.net/wet_scrubbers.htm


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## 4metals

No, in fact it is opposite of the flow, it points to the text box saying what is down the line. 

The eductors in your link are of the same type but bigger. They work the same.


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## golddie

I will be honest with you guys and say that I didnt read in detail what was written here but I will read it when I have the time and the need.
What I would like to ask those who know about my scrubber ,would it be possible to convert my scrubber to one of these
Thanks


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## shyknee

4metals
This one is just brilliant.
Great design. I thank you.
The other day I was contemplating using a compressed air venturi vacuum pump and never thought to use the scrub liquid straight from the pump (much quieter too). This is just great !
I think I have a plastic eductor some where I used to suck out the water from my aquarium.


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## 4metals

> I think I have a plastic eductor some where I used to suck out the water from my aquarium.



If you have an eductor that can suck 10 CFM out of an aquarium it must be one huge fish tank!


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## shyknee

I still think small scale 1oz or less it's still just a hobby for me. The aquarium was a 140gallon tank about 25feet away from the sink .I don't know about the CFM of air but it also emptied my old water bed (25years ago) in about an hour with two feet of head. Do you think this would work ? Thanks 4metals I value your opinion.


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## 4metals

Shynee,

You could make a trap in glass erlenmeyer flasks filled with glass marbles and caustic liquid. Pull the air through it with your eductor and make sure the bucket on the right side of drawing has a tight fitting lid. You will need to place a hole in the lid which you can plug to allow a slow flow of air in to make up for what you take out. Use a beaker in the pail and you should be fine for a few ounces.


I think you can get plastic erlenmeyer vacuum flasks pretty cheap. I'd still be doing this in an exhaust hood or outdoors.


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## Barren Realms 007

golddie said:


> I will be honest with you guys and say that I didnt read in detail what was written here but I will read it when I have the time and the need.
> What I would like to ask those who know about my scrubber ,would it be possible to convert my scrubber to one of these
> Thanks



Yours is a little different type of tank but it might be possible to get it to work.


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## shyknee

Nice thanks


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## HAuCl4

Nice design 4metals!. A variation of the big johnson?. This one does not remake the nitric acid, only vaccums and scrubs right?.

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=49&t=8619&p=80788&hilit=big+johnson#p80788


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## rbramsey

I like this design it seems KISS. 

I would like a few more details:
Can someone point me into the right direction for a 10 CFM eductor? Not to be picky, but a part # and website would be great.
What size pump? 
What pressure is needed at the eductor?
What size is the pipe from the fume hood and from the pump?

Thanks,
Richard


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## 4metals

The pipe sizes are dependent on the cfm of the eductor, as are the piping sizes and the pump. This one uses an eductor with a 1 1/2 inch inlet (the line coming down the scrubber into the eductor) and a 2 1/2 inch suction line. 

The eductors and the required pump flows can be found here http://www.mcmaster.com/#eductors/=az29d0 look at liquid operated pumps.


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## Barren Realms 007

4metals said:


> The pipe sizes are dependent on the cfm of the eductor, as are the piping sizes and the pump. This one uses an eductor with a 1 1/2 inch inlet (the line coming down the scrubber into the eductor) and a 2 1/2 inch suction line.
> 
> The eductors and the required pump flows can be found here http://www.mcmaster.com/#eductors/=az29d0 look at liquid operated pumps.



Are you sure about the size being 2-1/2" and not a 2". This is not a regular size pipe. Pipe sizes jump from 2" to 3" in PVC pipe?


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## 4metals

That particular eductor has a 2 1/2 inch suction port. You could immediately use a fitting to expand that to 3" which is a universally available size. The air will still move through the pipe at 10 cfm (actually 11 with the correct pump) but it's velocity will be a bit slower which is no problem.

This is where some of the machine shop guys should step up to the plate. There has to be a series of standard PVC fittings coupled with a little lathe turning that could turn out an eductor relatively easily. This size from McMaster costs just shy of $800. 

THe pump and eductor are the most costly components of the system.


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## Barren Realms 007

4metals said:


> That particular eductor has a 2 1/2 inch suction port. You could immediately use a fitting to expand that to 3" which is a universally available size. The air will still move through the pipe at 10 cfm (actually 11 with the correct pump) but it's velocity will be a bit slower which is no problem.
> 
> This is where some of the machine shop guys should step up to the plate. There has to be a series of standard PVC fittings coupled with a little lathe turning that could turn out an eductor relatively easily. This size from McMaster costs just shy of $800.
> 
> THe pump and eductor are the most costly components of the system.



Yea I agree. It would be better to make it out of SCH80 grey pipe because of the thicknes ofthe walls. Only trick is you have to put a bushing inside the pipe you keep it from deforming when you turn it. This is what has to be done when you thread it or the pipe will deflect inwards during the threading process and crack and break.


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## qst42know

Schedule 40 or 80 PVC in 2-1/2" is available through USPlastics.

http://www.usplastic.com/catalog/item.aspx?itemid=23979&clickid=redirect


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## Barren Realms 007

qst42know said:


> Schedule 40 or 80 PVC in 2-1/2" is available through USPlastics.
> 
> http://www.usplastic.com/catalog/item.aspx?itemid=23979&clickid=redirect



I know I have run 2-1/2" in copper but never 2-1/2" in PVC. Thanks


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## rbramsey

Ask an electrical supply house. I used 2-1/2" PVC before for data wires, and for making tator guns that shoot tennis balls.

Richard


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## Barren Realms 007

rbramsey said:


> Ask an electrical supply house. I used 2-1/2" PVC before for data wires, and for making tator guns that shoot tennis balls.
> 
> Richard



Yes but you are not supposed to use electrical conduit for applications like this.


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## rbramsey

Yes, but pressure wouldn't much of a consideration at that point. I know where I seen sch40 PVC also, is at chicken houses. They are used in the feed system. This is also 2-1/2". I can double-check in a little while. I have some at home.

Richard


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## 4metals

> A variation of the big johnson?. This one does not remake the nitric acid, only vaccums and scrubs right?.



This one would make nitric to a limited extent as the flow through the unit is quite high. To make nitric there is no draw on the scrubber either from a blower or an eductor. The flow comes from the oxygen flow which pressurizes the vessel the reaction is taking place in and forces it into the scrubbing chamber and out the top. The flow is slower but it is an enclosed system, sealed from the reactor to the outlet of the scrubber. So this is not in the Big Johnston class of scrubber.


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## Barren Realms 007

rbramsey said:


> Yes, but pressure wouldn't much of a consideration at that point. I know where I seen sch40 PVC also, is at chicken houses. They are used in the feed system. This is also 2-1/2". I can double-check in a little while. I have some at home.
> 
> Richard



Yea that is for the screw conveyor but if I remember right that is thinwall pipe specificly for that application. Use to have one in our finishing house on the hog farm.


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## rbramsey

Barren Realms 007 said:


> Yea that is for the screw conveyor but if I remember right that is thinwall pipe specificly for that application. Use to have one in our finishing house on the hog farm.



You are correct. I forgot about that.

Richard


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## rbramsey

$800.00 is too much for me to buy, but I think I can make one. It might not as efficient, but doable. I have built other venturi jets for our dredge with some good results in the past. I would make this out of PVC. I think by taking some off the shelf parts (sweep and bushings) and welding the plastic, I could pull this off.

I need some help. I am still trying to get my head wrapped around the eductor specs. Using the specs from McMasters 
http://www.mcmaster.com/#eductors/=azj1bb 
they list several types of eductors with ratings. They list liquid operated/liquid suction, steam operated/liquid suction, and steam operated/gas suction. How would I convert the parameters for a liquid operated/gas suction eductor to figure 10 cfm suction. From the charts, I see that I would assume atmospheric pressure in refining use, but I would need to know what the inlet pressure needs to be? Can someone help me with the formulas?

Richard


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## golddie

I am trying to understand this concept and this subject is completely knew to me.

First I would like to understand this tool and how it is used in this system
http://www.mcmaster.com/#eductors/=b05gh1
jet pumps
If I am correct the water that flows into this thing comes with a greater force.
I looked at the picture and I am not getting anywhere and reading the posts are not helping me.

I know about vacuum filtering (page 238 hoke)

If anyone can explain this system in the simplest way that would be nice.
Thanks


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## Barren Realms 007

golddie said:


> I am trying to understand this concept and this subject is completely knew to me.
> 
> First I would like to understand this tool and how it is used in this system
> http://www.mcmaster.com/#eductors/=b05gh1
> jet pumps
> If I am correct the water that flows into this thing comes with a greater force.
> I looked at the picture and I am not getting anywhere and reading the posts are not helping me.
> 
> I know about vacuum filtering (page 238 hoke)
> 
> If anyone can explain this system in the simplest way that would be nice.
> Thanks



To put it in very simple terms if you go back and look at 4metals picture. The green pipe that goes into the red pipe has a nozzel on it. The red pipe is bigger than the green pipe and when the fluid from the green pipe goes into the red pipe it pulls a vacume on the red pipe and pulls the fumes from the containers thru the red pipe and they go into the tank and then up thru the stack.


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## golddie

Hi Barren
That is exactly what I was looking for 
Thanks Buddy


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## Acid_Bath76

I in the process of building my own scrubber, and I want to make sure I pick up the right water pump. It needs to pull the NaOH/water out of the tank, up, and into the sprayer within the scrubber. I'm concerned that the caustic nature of the scrubbing solution is going to destroy my water pump pretty quickly. What type does everyone here use? Would something like this work? 

http://www.amazon.com/Flojet-Electric-Water-Chemical-Pump/dp/B004HL5V5M


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## 4metals

You need a pump to handle corrosives like this

http://www.usplastic.com/catalog/item.aspx?itemid=27449&catid=629 

You also need a flow of at least 250 gph at working pressure


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## NoIdea

Hello - the water pumps used in washing machines are design for mild caustic solution, those found is washing powder, and alot cheeper. The coil is sealed in plastic to prevent moisture damage.

Deano


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## overdriv

Granger Supply has quite a few different options on pumps that can handle both acids and/or bases. This is what my scrubber looks like.


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## NobleMetalWorks

Hello,

This is my first post, I have silently been reading this forums, and learning a lot. So before I go any further, yes I have read Hoke, and I think she was brilliant, and I honestly try to find answers before I post questions. I am really happy that this forum exists, it seems there is very little real information anywhere that is easily digestible and involves so many brilliant minds discussing how to refine PM. It's awesome. So I have read many many posts in the forums and have set up a fairy decent garage lab/gold recovery system. The only two parts that are missing is a fume hood/scrubber, and an XRF scanner. The scanner is a pipe dream, haha, so I am working on the fume hood/scrubber and came across this post. Awesome post by the way.

I had a few ideas, the type of filter this is, is almost the same type of venturi filter that I use for my salt water tanks. I have 5 huge tanks, these filters help keep the nitrates/nitrites out of my water. The idea is to pump the water into the venturi reaction chamber, and add air, via an air stone. The air entering the chamber has a positive charge, and lucky for my fish the nitrate/nitrite are negative. The air bubbles attach and carry the waste to the top where the bubble pops, and leave behind the negative nitrite/nitrate in a cup around the top. The air is allowed to escape.

I had mine made to my spec by Tap Plastics so that I could add some additional features, one that has really seemed to help a lot was installing a submersible water pump on the bottom of the reaction chamber, right above where the air enters the chamber via an air stone. In this way I can keep the bubbles in the water longer because they are spinning around instead of just going straight up to the top. Obviously you need to position the pump so that it pushes the water along the inside making it swirl. It seems to me that if you do this with this filter, you could actually cut the size of the reaction chamber down and even use less water in the process. Also smaller bubbles would react faster, if you put the submersible pump where the air actually enters, it seems that it would cavatate and cause the bubbles to break up into even smaller bubbles. I think you could even shorten the reaction chamber more, and use even less water.

Also, for my reef filters I use a plastic media that allows for bacteria to grow on it's surface so that it breaks the biological garbage in the water into nitrates, they have been created to maximize surface area so that the largest possible number of bacteria can grow on their surface, cutting down on the amount of space needed. If this media was used, it would cause the bubbles to take even more time to make it to the top of the chamber, and I think you know what I am going to say, next.

Also, if the air is positive charged going into the chamber, in the form of an air stone and I believe you would not have to purchase one of those expensive lab air stones because the pump would be pumping clean water directing on it, but I might be mistaken about that. Anyway, isn't the gas being drawn into the reaction chamber negative charged? If the air bubbles are being pushed by water into the air/gas coming into the chamber, you not only create a cavatating effect, but you are mixing the two types of air together which seems like it would help in the reaction.

I wonder if aquarium pumps might work, they are fully sealed in hard plastic except for the impeller, I am not sure what material the magnet is made of, nor the axel the impeller rides on. How much nitric has to be in the water before it starts reacting on metals? If you dissolved a small amount of Urea in the water, would this solve the problem, or just create another problem by creating Urea Nitrate?

Just my thoughts, and I may even be way off if I am please be kind because this is after all my very first post. =)


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## overdriv

SBrown said:


> Hello,
> The only two parts that are missing is a fume hood/scrubber, and an XRF scanner. The scanner is a pipe dream, haha, so I am working on the fume hood/scrubber and came across this post.




Sorry, I got lost in all the fish tank talk. If I missed a question please repost it or send a pm. 

The fume hood is made from polypropylene and is welded together, and since it is welded any spills will stay it the fume hood. If the price is right I could build one for you. The tubing from the lab hood is HDPE, but could be made from schedule 40. The scrubber is HDPE (I believe) and is way too big. There are lawn sprinklers at the top and crushed marble at the bottom. I would buy a acid proof pump that is rated for the height of the water to push and the amount of water you need to flow (Granger). The most important is the fan..... get a acid proof fan. If you work in an enclosed area in the winter like me...... your life is worth what you spend.


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## Acid_Bath76

overdriv said:


> Granger Supply has quite a few different options on pumps that can handle both acids and/or bases. This is what my scrubber looks like.



wow! looks great!!


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## NobleMetalWorks

I decided to attempt to build this. I am going to give Taps Plastic a call tomorrow and see if I can get some of the parts fabricated in the way I want, here are a few ideas I had. I think I might be able to improve upon the design using my knowledge of aquarium filters. I know hardly anything about these types of systems when it comes to scrubbing, so I am hoping that if I am in error, in my thinking, someone will please correct me.

Right above the drain valve I was thinking of putting another valve that would ensure water flow was cut going up the blue pipe so that the pump can be used to pump the waste water out of the reservoir. The valve already in that line should be kept, but I think making the T off the valve threaded, so a chemical resistant hose or spout can be screwed in, might come in handy.

Splitting the reservoir tank down the middle with a sheet of PVC or Polypropylene sheet to just below where the water line would be so that the water can still move back and forth through the reservoir, just not the air. The red air line coming into the tank from the hood would go through this separator to the opposite side of the chamber from the access port. The red water pipe coming down into the reservoir tank, that T's with the air coming in from the hood would also go under the water line just like in the diagram, but not as low as the sheet of plastic that splits the reservoir in half.

The reason for this design is to keep the plastic balls in the next modification from moving to the access port side.

In the side of the reservoir opposite the access port, fill that side with bio balls used in salt water reef tank filters. The idea behind that it breaks up the bubbles even smaller as they pass through them, and it slows the bubbles travel time to the surface down a considerable amount. Plus, some bubbles will collect on the plastic balls and stay for awhile. The plastic bio balls look like this.







This is the part I feel I may be wrong about, but I would like to know if it's totally off base or may work. I think the chamber that has the spray head requires some room to react with whatever gas is left over, but I would also like to fill this chamber about halfway with the same bio balls, my thinking is this. As the balls get wet, the droplets of water will capture some of the outgas from the reservoir, when the droplets collect and become heavy enough they will make their way back down into the reservoir.

I like the idea of the viewing port in the 12 ducting pipe, I am going to see if Taps plastic has any clear plastic tubing that is acid resistant (polypropylene?) that can either be inserted in the middle so that you have a clear view all the way through, or that the entire length of the pipe can be made from.

For the reservoir I am thinking of using a 55 gallon DI water barrel, I can purchase them used from the place I purchase my Nitric Acid for $10 a piece. They are made out of a super heavy duty plastic that is about 1/4 inch thick, much better than plastic garbage cans, I currently use them to throw the recycle scrap I don't process into, like aluminum, etc. I think this would work perfectly, the lid is plastic welded air tight. I think just simply cutting a hole in the top for the 12 inch Conduit would work.

At the bottom of the reservoir tank I am thinking about putting in air stones, with a small aquarium air pump and tubing outside the chamber pumping air into the air stone inside the chamber. My thinking is this. The outgas coming into the reservoir is negative charged, the air coming out of the air stone is positive charged. As the two react with each other the negative charged outgase ions will be attracted to the positive charge air bubbles and will jump from the outgas air bubbles, to the outside of the positive charged air bubbles so that when they pop on the surface of the water, they let the negative charged ions go to be absorbed into the water instead of rising to the top of the 12 inch pipe.

Putting a 500gph submersible aquarium pump at the bottom of the reservoir, pointing in such a way as to make the water, with air bubbles, move in a circular pattern, keeping the bubbles in the water even longer. And even better, more cost effective and energy efficient way of doing this would be to simply angle the red water line entering the reservoir so that it makes the water mixed with the outgas follow the inside wall of the reservoir thus creating a similar swirling effect and keeping the bubbles suspended in the water longer.

Okay, have at, critic the hell out of my ideas please, but be constructive so that I can learn from any mistakes I made in my thinking.

And thank you!


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## butcher

Something to consider is temperature, gases aborb into cold solution and stay longer than in hot solutions, also some chemical reactions tend to heat up a solution.


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## overdriv

The bio balls are a great idea. You could possibly have a smaller chamber if you use them. I decided to use the "KISS" system as my goal was to keep* ME* breathing and knowing that full well the fan was blowing the "bad air" outside. There is a reason I used crushed marble in the bottom of the reaction chambers of the scrubber. Most acids react with marble and the reaction should neutralize the acid and give off harmless gases. In my system there are only two reaction chambers, the 55 gallon drums. The thirty gallon drums on top are to be used in the future. If you want to improve on my design:

1. use bigger pipes from the lab hood to the scrubber. This will increase the air flow/suction. 

2. Make the lab hood bigger to handle more reactions.. I can do AR, silver cell, inquartation and cementing silver all at the same time. I can be working at less that an arms length while these are reacting and not smell a bad fume. Bigger windows and bigger lab hood would have been great.

3. Put bigger inlet air vents on the lab hood.

Remember, to vacate the air in the room as well. Put suction vents at floor level and up high as well. If you are going to use a torch inside make sure you have a means to suck out those fumes as well. Silver, Cadmium, and many other metals that we melt can have toxic off gases as well. Consider propane (cheaper fuel) and hydrogen (for platinum) instead of acetylene because of the black carbon deposited on your lab work.

Your bubbles and whatever become secondary to staying alive.

Good luck.


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## NobleMetalWorks

I picked up my hood today, it's actually very nice. I got the hood and 6 cabinets, one fire, one acid, one shelves with glass sliding doors, and three that have 3 huge drawers. I picked up each for 100, spent a total of $600 dollars. The hood looks like it's never been used. It has an acid resistant coating, a glass sliding door in the front, a polypropylene black bottom. Any ideas on the best way of connecting the scrubber without cutting into the metal if I can help it? I was thinking about having taps plastic fabricate a bottom ring that the hood would set on, out of polypropylene and put the scrubber pipes through that into the inside of the hood and then just simply pipe them inside to wherever I needed suction.

Any ideas on that?

overdriv, I looked at the pictures you posted, I understand the hood, the pipes coming off the hood so that you get suction from different areas of the hood, I am assuming the pump is a submersible in the small blue container on the cement in front of the reservoir rack? Or is that wrong, I see the fan, and the large 12" conduit, I am assuming that the conduit is expelling offgas and the fan facilitates by pushing rather than pulling? That way it doesn't have to be acid resistant? It looks like a large squirrel fan, is that right? What is it's airflow? And does that exit out of the room behind the hood? I was planning on using one 55 gallon drum rated for chemicals that I picked up from a local Bio Tech Firm I used to work for, I have three of them. Do I need two? I was going to use one, and then make a 6-7 ft spray down tower with the spray nozzle at the top and make it out of 12" conduit. If I split the pump like you have, into two 6ft tall, 12" PVC conduit and had them come out of the top of the barrel would that be enough? Or do you think I should just use two 55 gallon barrels?

I am trying to make the system as compact, width wise as possible. But if I am wrong with the design I am talking about, please someone tell me.

The ground up marble was a stroke of brilliance, where did you find yours?

If the spray down stacks wouldn't work, couldn't I have Taps plastic weld two plastic 55 gallon barrels, one on top of the other and do it that way? Would that be a better design?

Here is a picture of the hood I picked up today for $100, I couldn't believe it! It's a 6 ft wide Canadian Cabinet acid resistant hood.


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## Lou

SBrown:
Beautiful hood and a great deal you got there! Wish you did my shopping!




As far as bed packing media...we just make Raschig rings out of PVC pipe sections. More surface area, better flow through, more turbulence, more scrubbing efficiency in a countercurrent column. Problem is you need a greater pressure drop on your blower.

I've seen one very industrious well-known refiner here on this forum build one out of two 55 gallon drums and make his own PVC manifold--as good as the Italians make and about 10^2 cheaper.


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## overdriv

SBrown said:


> Any ideas on the best way of connecting the scrubber without cutting into the metal if I can help it? I was thinking about having taps plastic fabricate a bottom ring that the hood would set on, out of polypropylene and put the scrubber pipes through that into the inside of the hood and then just simply pipe them inside to wherever I needed suction.
> 
> Any ideas on that?



1.How you get the suction into the fume hood is up to you. Try not to over think this thing. There are two things to remember. Your fumes when hot will rise easily and air flow/ suction is important at the top. Mine is not perfect and I would change some things. If you do have a pipe coming up from below inside the hood then you have less room for beakers with reactions. Also you have now a hole in the floor for PGM's to spill out if you have an accident. Try to find a spot on the side up high, on top or on the back up high. 
a. Also the acid fumes when you are not heating them will tend to drop down to the bottom of the lab hood.
b. Provide an air supply that is equal to the air you are drawing.. Notice the air intakes on the front of the lab hood. Mine should be bigger. Although, I can watch the reactions happen with the window open or with the window closed. 

2. The pipes that I used on top of my lab hood are really too small.... They work well and are acid proof. A 2", 3" or 4" pipe would suck more air. Schedule 40 or 80 would work well for this.

3. The air flow into the Scrubber is NOT bubbling. You have the Bio Balls and they will increase the area that the fumes will have to react with the wet spray. If you notice that the pipes going into the scrubber are not at the bottom and there for there is NO bubbling. The lawn sprayers that I used will spray a curtain of water and the spray created a mist as well. Using 55 gallon drums was overkill.... way overkill. With your Bio Balls you should be able to get away with 30 gallon drums. 

4. If you proceed to go down the path of bubbles floating up through the Bio Balls, you will run into two problems. 
a. You will have to either have to create a pump pushing the TOXIC FUMES into the scrubber or through the water. The first will probably force the toxic fumes to leak out and the second will cause your plastic drums to collapse (trying to suck the fumes through the drums collapsed mine).
b. You will make the thing not as simple to operate.




SBrown said:


> I am assuming the pump is a submersible in the small blue container on the cement in front of the reservoir rack?



There is a acid resistant pump in the bottom of the front reservoir. Make sure it is powerful enough to pump the water vertically up to the sprayers. This is only for spraying water and does not suck the air from the lab hood.




SBrown said:


> Or is that wrong, I see the fan, and the large 12" conduit, I am assuming that the conduit is expelling offgas and the fan facilitates by pushing rather than pulling? That way it doesn't have to be acid resistant?



Yes, it should be acid resistant or just be prepared to buy new ones later. The fan you can not see is pulling the air through lab hood and through the scrubber (the sprayer wash) and outside very clean. It is also pulling air out the the lab.... You will appreciate this when you start pouring acid outside of your lab hood. Also it is mainly aimed at the floor scooping up fumes at the floor level and at the torch/melting/table. The fumes from this area is equally toxic.





SBrown said:


> Do I need two? I was going to use one, and then make a 6-7 ft spray down tower with the spray nozzle at the top and make it out of 12" conduit. If I split the pump like you have, into two 6ft tall, 12" PVC conduit and had them come out of the top of the barrel would that be enough? Or do you think I should just use two 55 gallon barrels?




1.The first barrel with a sprayer on top and bioballs in the middle and crushed marble at the bottom of the barrel should (estimated) take out 90% of the toxic fumes. The second barrel configured the same will further reduce the toxic fumes. 
2. I am not a guru on this stuff so if someone else has more knowledge than me please chime in.
3. Remember the fan should not be dedicated solely to the lab hood and scrubber. By making it take air from the lab as well you will provide a safety valve for the fan in case of a blockage in the scrubber or lab hood. You actually increase the pulling power of the fan for the scrubber, (this is as long as you choose a fan that is oversized).

One tall chamber will have one inherent problem. The sprayer will spray out at an angle and probably hit the walls of the PVC. The water will then run down the walls and not react with the bioballs or the fumes. If you use two 55 gallon drums like I did then fill the drums with bioballs up to the point where the sprayed water will splash evenly over the balls and concentrate on the walls or the center/middle of the drum. This allows the fumes to react with the water soaked bioballs and become a weak acid. Dripping down to the crushed marble and becoming neutralized. 

http://www.usplastic.com/catalog/search.aspx?search=fans,%20acid%20resistant&page=1


Remember the lab hood, the scrubbers are the tools, the fan is the life saver.

Crushed marble can be found at building materials yard.


----------



## NobleMetalWorks

Thank you for correcting and clarifying, I really appreciate it.

if you look at the hood, the two sides have open holes, I have pieces of polypropylene plastic it came with that fit, with acid resistant seals, in the holes. I am planning on having holes cut large enough and attaching two - four pvc suction pipes, the top has a hole where the vent used to attach, it covers about 3/4 of the distance across the top of the hood. I am planning on fitting a piece of polypropylene in the vent hole, and dropping a PVC pipe into the top part of the inside of the hood to suck gas that reaches the top (heated NOx, etc). On the back, I am planning on setting the hood on a polypropylene collar that will allow PVC pipe to suck from the back, and nothing in the bottom of the hood, you are right I didn't think about any spilled aqua regia wasting down an outgas vent.

I might decide to use sheets of 1/2 polypropylene cut to spec by taps, and fabricate the scrubber myself. If I can use some type of clear plastic, so I can see everything going on in the scrubber, I may go that route unless there is something I am missing or should know? Taps sells a bonding liquid that fuse the parts together using a regular propane torch, no plastic welding.

I will have another hood that is 6ft across, similar to the hood I just purchased. I bought it from a different person, paid to have it shipped to me but I no longer need it. It arrives tomorrow, if anyone is interested let me know and I will snap pictures and post all the information, manufacturer, model number, etc tomorrow. I am only going to ask what I actually paid for the hood, plus what it cost to ship it to me. Also, I am having Taps Plastic fabricate some of the pieces I am going to use, if anyone is interested in the hood I could have parts fabricated at the same time, and just charge you for the cost. I live in the San Francisco Bay Area, so if there is someone in the area that is interested you can pick it up in person. If not, I would be willing to drop it off at a freight company within a reasonable distance from me, that will band it to a pallet and ship it to you. I would just ask, since I am going to sell it for what I paid and shipped it for, to pay for any gas past 30 miles so that I am not loosing money. I don't mind selling it for what I paid on this forum, but after a week I will put it on eBay for double the price, and still be way under what you can but the hood for, from anyone else, used.


----------



## overdriv

SBrown said:


> Thank you for correcting and clarifying, I really appreciate it.
> 
> I might decide to use sheets of 1/2 polypropylene cut to spec by taps, and fabricate the scrubber myself. If I can use some type of clear plastic, so I can see everything going on in the scrubber, I may go that route unless there is something I am missing or should know? Taps sells a bonding liquid that fuse the parts together using a regular propane torch, no plastic welding.
> 
> [\quote]
> 
> On your scrubber think KISS. The more you make it complicated the more that can go wrong with it. Like leaks....... water and gases. Think of it as exhaling all the bad fumes you do not want to breathe... outside. Yes, processed to do your part environmentally. That is why I used two 55 gallon barrels. However two 30gallon barrels the way you are doing it would be way overkill. What really is there to see inside the scrubber? Water splashing around. Pretty dark in there unless you are going to put in a light. The fumes would become very transparent in that environment.
> 
> Good luck.
> 
> Nick


----------



## overdriv

overdriv said:


> SBrown said:
> 
> 
> 
> Thank you for correcting and clarifying, I really appreciate it.
> 
> I might decide to use sheets of 1/2 polypropylene cut to spec by taps, and fabricate the scrubber myself. If I can use some type of clear plastic, so I can see everything going on in the scrubber, I may go that route unless there is something I am missing or should know? Taps sells a bonding liquid that fuse the parts together using a regular propane torch, no plastic welding.
> 
> [\quote]
> 
> On your scrubber think KISS. The more you make it complicated the more that can go wrong with it. Like leaks....... water and gases. Think of it as exhaling all the bad fumes you do not want to breathe... outside. Yes, processed "bad fumes" to do your part environmentally, "Thou shall not kill thy neighbor". That is why I used two 55 gallon barrels. However two 30gallon barrels the way you are doing it with bio balls would be way overkill. What really is there to see inside the scrubber? Water splashing around. Pretty dark in there unless you are going to put in a light. The fumes would become very transparent in that environment.
> 
> 
> 
> Umm, did you mean the fume hood or the scrubber? I would use a 1/4 inch glass on the fume hood to look in. That makes it very nice to see what reactions are happening in the fume hood. Make such window at the least 2ft wide.
> Good luck.
> 
> Nick
Click to expand...


----------



## NobleMetalWorks

overdriv said:


> overdriv said:
> 
> 
> 
> 
> 
> SBrown said:
> 
> 
> 
> Thank you for correcting and clarifying, I really appreciate it.
> 
> I might decide to use sheets of 1/2 polypropylene cut to spec by taps, and fabricate the scrubber myself. If I can use some type of clear plastic, so I can see everything going on in the scrubber, I may go that route unless there is something I am missing or should know? Taps sells a bonding liquid that fuse the parts together using a regular propane torch, no plastic welding.
> 
> [\quote]
> 
> On your scrubber think KISS. The more you make it complicated the more that can go wrong with it. Like leaks....... water and gases. Think of it as exhaling all the bad fumes you do not want to breathe... outside. Yes, processed "bad fumes" to do your part environmentally, "Thou shall not kill thy neighbor". That is why I used two 55 gallon barrels. However two 30gallon barrels the way you are doing it with bio balls would be way overkill. What really is there to see inside the scrubber? Water splashing around. Pretty dark in there unless you are going to put in a light. The fumes would become very transparent in that environment.
> 
> 
> 
> Umm, did you mean the fume hood or the scrubber? I would use a 1/4 inch glass on the fume hood to look in. That makes it very nice to see what reactions are happening in the fume hood. Make such window at the least 2ft wide.
> Good luck.
> 
> Nick
> 
> 
> 
> 
> 
> Click to expand...
Click to expand...


The fume hood has a counterbalanced glass door, here is a picture.






And if you notice on the left hand side it also has an airflow meter, and on the right, on the glass and the supporting frame there are arrows that when matched up, are suppose to be the operational level the glass door should be drawn down to.

The reason I thought clear poly is because in the plan it asks for windows in the spray down tower, so you can see what is going on. I thought instead of adding a view port, and making the fabrication more expensive, I could make the entire scrubber out of clear poly so that I can see everything working properly and would not have to use any view ports anywhere on the scrubber. All I would have to do is use a band like you have, or clamps, or some other way to fix the spray down tower to the reservoir. In that way I can get rid of the access port, and the view port and save on fabrication costs, and have the added extra benefit of being able to make sure the spray down tower sprayer, and all the other components, as well as the reservoir, substrate, etc were all working properly. The filters on my salt water reef tanks are all clear, here is what one looks like.






That is a reef filter that I just use for my sharks, the reef filters that I use for my reef tanks are a little more complex, but you can see what I am talking about. Here are some pictures of my old venturi protein skimmer and a new one I am replacing it with I just had modified by Taps. I figured since I was switching them out I would post some pictures so everyone understood what I have been blabbing about. 






This is what I was trying to explain, about the bubbles, but I am not going to attempt anything like this anytime soon. I need to do a lot more reading before I can figure out if this would actually work, or be beneficial at all. It kind of works on a similar principle as the venturi scrubber, except the scrubber exhausts air, where the protein skimmer captures nitrates/nitrites in the catch.











You can see all the sludge, the negative charged nitrates and nitrites that float to the top, then when the bubble pops it's cause in the catch. I had thought, if a ventruli filter could be made to do the same with the Nitric or other acid values in the water of the scrubber, it would be easy to balance the PH, because you would actually be removing them from the water. I just don't know enough to know if this can actually be done or not, and you are right it would make the scrubber that much more complex. But running the reef filter, and the ventruli protein skimmer, makes the water so pristine that my tanks shimmer.






I am just going to adapt the bio balls for now, and try other things out after I have a good solid working system.


----------



## overdriv

Well my friend you are truly amazing and my hat is off to you on the aquarium thing. The aquarium tank with the bioballs in it would probably work fine. (I AM OUT OF MY LEAGUE HERE, so please others that know better chime in.) The acid fume will be strongest in the pipe going to the scrubber and of course in the lab hood. Once it hits the water it will become a very weak acid. Once it hits the base elements it will start to neutralize. 

I can not wait to see your good results. If I do not understand what you did I will ask about it and maybe I can learn from you. Good luck.

Nick


----------



## NobleMetalWorks

overdriv said:


> Well my friend you are truly amazing and my hat is off to you on the aquarium thing. The aquarium tank with the bioballs in it would probably work fine. (I AM OUT OF MY LEAGUE HERE, so please others that know better chime in.) The acid fume will be strongest in the pipe going to the scrubber and of course in the lab hood. Once it hits the water it will become a very weak acid. Once it hits the base elements it will start to neutralize.
> 
> I can not wait to see your good results. If I do not understand what you did I will ask about it and maybe I can learn from you. Good luck.
> 
> Nick



Well, if I was going to use the tank, I would have to do something with the fish, lol, but thank you for the kind words.

I think I am going to take your advice and start off simple, I was only using the pictures to illustrate what I was talking about a little better. I read through what I posted, and I couldn't even understand it, ha. No, I knew what I was trying to say, but I just wasn't able to make it clear enough. Maybe if I had a stick and bare earth to scratch it out on, but pictures are the next best thing!

I know I'm going to have a lot of questions still, but I don't think I'll have too much of a problem putting a scrubber together. And thanks for the support!


----------



## butcher

Beautiful saltwater reef tank, I know you have had to learn a lot, to be able to have that nice of tanks, and to keep them critters alive, my daughter just started learning salt water tanks, and said she is learning the chemistry to take care of them, she said it was like listening to me talk about gold refining chemistry.

I believe from what you know of the salt water chemistry it will not be hard to use that knowledge in the gold refining, although we do not work with the organic bacteria changing ammonia to nitrate, there are similarity's in the chemistry, I can see your already using the knowledge in this field to build your scrubber.

The little nitrate factory you have there, it is beautiful and impressive.


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## NobleMetalWorks

butcher said:


> Beautiful saltwater reef tank, I know you have had to learn a lot, to be able to have that nice of tanks, and to keep them critters alive, my daughter just started learning salt water tanks, and said she is learning the chemistry to take care of them, she said it was like listening to me talk about gold refining chemistry.
> 
> I believe from what you know of the salt water chemistry it will not be hard to use that knowledge in the gold refining, although we do not work with the organic bacteria changing ammonia to nitrate, there are similarity's in the chemistry, I can see your already using the knowledge in this field to build your scrubber.
> 
> The little nitrate factory you have there, it is beautiful and impressive.



Hey, thanks a lot, I love it when people enjoy my tanks. I have had some of them since 1991. And you're right, salt water tanks have all kinds of chemistry going on, biological in nature for the most part but also inorganic as well, like charcoal, it's used to absorb ammonia as water passes through it. If you ever need help with anything to do with salt water aquariums I would be more than happy to try and help.


----------



## butcher

Thanks, I will let my daughter know.
Now we just need to learn to make nitric acid from that tank skimmer sludge.


----------



## Lou

SBrown, do you know Bill Wann?

He makes a mean scrubber and is an excellent source for reasonably priced big glassware.


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## 4metals

SBrown,

Very nice reef tank. From what I gather from quickly reading your posts is you are thinking that a protein skimmer type device will scrub your nitric fumes and enable you to somehow reconstitute your nitric. 

Nitric is removed from the air column in a scrubber by oxidation in the air on the surface of the tower packing (bio balls) The alkaline pH of the solution which has wet the fume on the packing neutralizes the fume. In reality a caustic only scrubber is at best 50% efficient at neutralizing NOx. adding peroxide either to the scrubber or the reaction can increase the efficiency. The big key is retention time in the scrubber. 8 seconds is good. If you think about it passing all of the air moving through the hood you will need to scrub a lot of air. I recommend a general exhaust for the hood and a manifold from closed reaction vessels directed to a smaller scrubber with the proper retention time. 

I have seen devices similar to your protein skimmers used in refining of electronic scrap. Parts with exposed gold plating were granulated and etched in a solution containing 50% nitric acid to release the foils of gold. The solution also contained potassium phosphate and citric acid to act as a frothing agent. The froth acted like scrubbing bubbles to release and float the gold particles in the froth where they were collected. The system is more efficient at removing the gold foils and the separation is effective. The protein skimmer on fish waste is an example of foam fractionation working on a hydrophilic compounds in the aquarium water. The foam fractionation to collect the gold flakes is an example of stripping non surface active particles from the waste stream. The reason I say this is not an effective method of scrubbing NOx is while watching the process, visible red fume passes right through the foam layer and is pulled into a classic fume scrubber. 

One question, how high do you maintain calcium hardness to stimulate coralline algae?


----------



## NobleMetalWorks

4metals said:


> SBrown,
> 
> Very nice reef tank. From what I gather from quickly reading your posts is you are thinking that a protein skimmer type device will scrub your nitric fumes and enable you to somehow reconstitute your nitric.
> 
> Nitric is removed from the air column in a scrubber by oxidation in the air on the surface of the tower packing (bio balls) The alkaline pH of the solution which has wet the fume on the packing neutralizes the fume. In reality a caustic only scrubber is at best 50% efficient at neutralizing NOx. adding peroxide either to the scrubber or the reaction can increase the efficiency. The big key is retention time in the scrubber. 8 seconds is good. If you think about it passing all of the air moving through the hood you will need to scrub a lot of air. I recommend a general exhaust for the hood and a manifold from closed reaction vessels directed to a smaller scrubber with the proper retention time.
> 
> I have seen devices similar to your protein skimmers used in refining of electronic scrap. Parts with exposed gold plating were granulated and etched in a solution containing 50% nitric acid to release the foils of gold. The solution also contained potassium phosphate and citric acid to act as a frothing agent. The froth acted like scrubbing bubbles to release and float the gold particles in the froth where they were collected. The system is more efficient at removing the gold foils and the separation is effective. The protein skimmer on fish waste is an example of foam fractionation working on a hydrophilic compounds in the aquarium water. The foam fractionation to collect the gold flakes is an example of stripping non surface active particles from the waste stream. The reason I say this is not an effective method of scrubbing NOx is while watching the process, visible red fume passes right through the foam layer and is pulled into a classic fume scrubber.
> 
> One question, how high do you maintain calcium hardness to stimulate coralline algae?



On the tank, if you notice the rock it's calcium rich basalt. You will also notice the giant clam if you can see it, right against the glass in front. I have had that clam since 1991, he has enough calcium to grow, but not too fast, he started out about and inch and a half wide, now he's about 11-12 inches. I don't need to add any calcium to any of my tanks, I honestly try to keep the coralline algae down to a minimum because it has a way of encrusting and fusing things together that I might have to replace. When I get a chance I'll show you a tank of mine I have had going since 1991 that has coralline algae so thick, I have a pump meant to circulate water that has long since died, fused to the corner of the tank in a huge mass of coralline algae. I have 3 tanks in series that each feed into, and out of the same reef filter/protein skimmer, etc. One of the three tanks I put new basalt rock into about once every year, in that same tank I have trigger fish, wrasses and parrot fish, it's a pretty tank all on it's own but the cool thing is that they chew up the basalt rock and spit it out of their gills to clean them, when they do that they release calcium into the water that makes it's way into my filter system, and then distributed into my reef tanks. In this way I can have more large fish in a tank than normally I could not, and they create the nutrients my corals need by chewing up basalt rock. In the reef tanks I can keep smaller, reef fish that otherwise would be eaten by the trigger fish. I don't like adding additives if I can help it, I am more about creating a sustainable eco system that I don't have to play with very much. I might put in about 6-8 total hours a month actually taking care of them, I only feed my small fish once every thee weeks, and even at that it's just a supplement food, I like to think I am giving them a treat. I have little tiny crustaceans, a little bigger than brian shrimp. They breed and live in my filters, eating the detritus that get caught in the mechanical filters (sponges) so I never clean them anymore, in turn, when they breed too heavy, the extras end up spilling into the tank where they are eaten by fish. The only fish I have to hand feed are my sharks, and my trigger fish. Other than that, most everything else takes care of itself and I only feed the smaller fish supplements to their food once every 3 weeks.

If my hood is fairly air tight, couldn't I lower the shroud enough to only allow as much air flow as the scrubber can handle going in? So long as the shroud face has positive air flow into the hood? I have 2 air flow meters, I was thinking I could use one on the outgas exhaust conduit, and one on the hood for air intake, balance them so that the two match and the hood is only bringing in as much air as the scrubber can handle? The only problem I see with that is the air flow meter being damaged by NOx. In your opinion should I scrap that idea (no pun intended "scrap") and just make a reaction vessel out of poly?

On the protein skimmer, the way you describe it, I can make that work. I have been designing and building protein skimmers for my own personal use and a few close friends for about 20 years, it's only been recently that I have purchased them. I probably have enough old protein skimmers to test several different designs. I might play around with that after I have a working system put together. Thank you so much for all the information! It's a very interesting concept at the very least.


----------



## 4metals

Don't get your hopes up for the hood being tight, those laboratory hoods have an airflow pattern that remains constant. If the door is down the full CFM flows over the top vents into the hood and vened through the blower. If the door is open, the top vents are blocked and the air influx is through the door. My guess that's a 6 foot hood so the full opening is likely at least 6 feet by 2 feet. 

Conventional exhaust protocol will require a 1200 CFM blower for that hood. An efficient scrubber for that hood will be huge if you want to scrub all of the air. To give you an idea of size, if you had 2 full 55 gallon drums, one atop the other and filled to the gills with bioballs, your CFM capacity to hold the fume in the scrubber for 8 seconds will be 110 CFM. 

I would opt for 1, 55 gallon drum of balls and a 50 cfm blower running through a manifold in the back of the hood. A sealed "reactor" can be as simple as a 5 gallon Spackle bucket with a bulkhead fitting close to the top on the side where a hose hooks up to carry the fume to the manifold. you can easily remove the lid and add chemicals or scrap to the bucket and replace it to regain suction. All the while the main exhaust will remove any fugitive fume. Plastic band heaters will warm the acid in a plastic pail nicely if necessary.


----------



## NobleMetalWorks

4metals said:


> Don't get your hopes up for the hood being tight, those laboratory hoods have an airflow pattern that remains constant. If the door is down the full CFM flows over the top vents into the hood and vened through the blower. If the door is open, the top vents are blocked and the air influx is through the door. My guess that's a 6 foot hood so the full opening is likely at least 6 feet by 2 feet.
> 
> Conventional exhaust protocol will require a 1200 CFM blower for that hood. An efficient scrubber for that hood will be huge if you want to scrub all of the air. To give you an idea of size, if you had 2 full 55 gallon drums, one atop the other and filled to the gills with bioballs, your CFM capacity to hold the fume in the scrubber for 8 seconds will be 110 CFM.
> 
> I would opt for 1, 55 gallon drum of balls and a 50 cfm blower running through a manifold in the back of the hood. A sealed "reactor" can be as simple as a 5 gallon Spackle bucket with a bulkhead fitting close to the top on the side where a hose hooks up to carry the fume to the manifold. you can easily remove the lid and add chemicals or scrap to the bucket and replace it to regain suction. All the while the main exhaust will remove any fugitive fume. Plastic band heaters will warm the acid in a plastic pail nicely if necessary.




Thank you, makes perfect sense. I was thinking of a reactor that I could remove or insert as needed. I have a poly base I milled a round slot that fits the lip of a 5 gallon plastic bucket. If I used that with PVP pipe from the bucket to the scrubber I would have a cheep and easy, and most important safe reaction chamber I think.

I was also thinking about something like this http://www.ebay.com/itm/Nederman-Fu...029?pt=LH_DefaultDomain_0&hash=item1c1875b315 to connect the scrubber to so that I can easily move it around in the hood but it would be out of the way when I didn't need it. Any thoughts of this?

And thank you again for the help!


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## 4metals

The arm can only exhaust one reaction at a time, I would run a 4" manifold across the back of the hood with 6 inch and a half drops, each with their own shut off valve all leading into the scrubber inlet. This way you can have some digestions cooking on one or two drops while precipitating gold on another drop. 

You could also build a foam fractionator to collect your foils and scrub the fume coming off. 

You never mentioned what type of refining you're doing or the size of your process lots so it could very well be you only need one collection point.


----------



## NobleMetalWorks

4metals said:


> The arm can only exhaust one reaction at a time, I would run a 4" manifold across the back of the hood with 6 inch and a half drops, each with their own shut off valve all leading into the scrubber inlet. This way you can have some digestions cooking on one or two drops while precipitating gold on another drop.
> 
> You could also build a foam fractionator to collect your foils and scrub the fume coming off.
> 
> You never mentioned what type of refining you're doing or the size of your process lots so it could very well be you only need one collection point.



I am very new to this if you couldn't already tell. I paid off my initial investment so I have stopped processing for the time being, and am concentrating on getting my work area the way I want it, hood, scrubber, lighting, ventilation, etc. I am primarily recovering gold from e-scrap, however I have run some plated jewelry through an HHO cell with awesome results. I am not planning on growing big enough that I have to hire employees, been there, done that, bought the t-shirt and it's just not for me. I only want to do this to supplement and perhaps eventually make a living this way, or maybe a little more. But I am not expecting, nor am I intending to make millions doing this, anytime in the near future.

However, I am set up, or will be, to be able to deal with large quantities of scrap. I have beakers up to 4000 ml, so whatever I do has to be able to encompass beakers that size, I am using two heat pad/stirrers and I have to tell you, I love the stirrers, makes a huge world of difference. When I am running I usually have 6-8 large 2000 - 4000 ml beakers at different stages of processing. I was doing anything that was reacting, giving off gas, outside. But I was starting to process so much that I was afraid if the wind blew the wrong way, I would be polluting my neighbors air, not to mention the fact that when you do large amounts, you create huge amounts of NOx. I was reacting 10lbs of pins/finger boards at a time.

I think your suggestion is probably better than my fancy costly solution, it makes a lot more sense, I could also use the same lines for suction, for Buchner filters, so long as I attach a fitting for the rubber hose.

So, I am recovering and refining, reacting large amounts in large beakers, and I have several going all at the same time, at different points in the recovery or refining process.

Did I answer everything?


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## 4metals

Then you definitely need to be doing more than 1 thing at a time (someday) . This is an example of the manifold, a change, made since this was made, is to have the tee's extend to the back of the hood horizontally into a shut off valve and then a 90 degree elbow and the hose. This does 2 things, one it allows lines to be shut off increasing suction to others and two it prevents condensate from running down the next inlet down the line. 


A tee replaced the manifold elbow that goes up with a reducer and a 1/2" valve to drain the "scrubber juice." There is definitely value in scrubber juice, so always check it with stannous.


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## NobleMetalWorks

That makes sense!

What type of material is the flexi hose made of? Is that PCV or is it Poly or some other material?

I was wondering who made the hood, I see in the upper right hand corner the tag of whoever made it. Did they also design it, or is the design your own? It looks very well built, best custom hood I have seen, and lately I have seen a lot of hokey systems for sale.

I am going to end up trading in the three 6ft hoods I have, for one 4ft poly hood, and a few other items/money. Not positive but I speak with the guy again tomorrow. Anything other than being made out of Poly with the glass sash I should be aware of? I am going to make sure I get an air flow meter/alarm. Is there anything else besides the scrubber that I should think about and maybe ask him to throw in on the trade?


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## 4metals

The flex hose is polyethylene off the shelf item from US Plastics.

http://www.usplastic.com/catalog/item.aspx?itemid=23022&catid=567


The hood shown has a plexiglass eye shield which folds up. generally it is down and the main exhaust is sized for the opening with the shield down. 

This hood is made by Chem Tec form Long Island NY http://www.chemteksys.com/Fume-Hoods.html


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## NobleMetalWorks

4metals said:


> The flex hose is polyethylene off the shelf item from US Plastics.
> 
> http://www.usplastic.com/catalog/item.aspx?itemid=23022&catid=567
> 
> 
> The hood shown has a plexiglass eye shield which folds up. generally it is down and the main exhaust is sized for the opening with the shield down.
> 
> This hood is made by Chem Tec form Long Island NY http://www.chemteksys.com/Fume-Hoods.html



Thank you for all the information, it's really appreciated. When I get rolling I'll post my progress.


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## NobleMetalWorks

I wanted to post this video on how to make a home made eductor venturi. I have done this for my fish tanks, and included one similar to the one made in this video, in my fume scrubber.

[youtube]http://www.youtube.com/watch?v=j47XbRzCcNo&feature=related[/youtube]

Also, I found these a long time ago, and just found the link again. I have not purchased anything from these people, but I was thinking about it at one time, for a fish tank. Fairly inexpensive.

http://www.millerplastics.com/eductors.html

EDITED: I am building another fume scrubber, I want a more efficient eductor, so I called, and spoke with an engineer at millerplastics about their eductors. With the correct pump, their 2 inch eductor will pull 10 cfm. Its actually a 1.25'' inlet and a 2'' outlet. If anyone would like more information you may message me.

Any comments or corrections, please feel free to post and quote.


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## saadat68

Hi
Opening of my *venturi *hood is 1 square foot. Is 100 CFM blower enough?


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## 4metals

You seem to be confusing a venturi for powering a scrubber with a venturi style exhaust blower. A venturi as in the video is for powering a scrubber and it requires a strong water circulating pump. A scrubber to power a hood is powered with an airflow from an air blower and it causes a venturi effect sucking the air out of the hood to follow the blowers flow. It is used when you have a blower that is not corrosion resistant and you blow clean air up a pipe causing the air in the hood to follow it. 

The reason you use a venturi powered scrubber is to scrub a small quantity of fume being sucked from an enclosed reaction. A flow of 10 CFM is good for that type application. 

A flow of 100 CFM would require a huge venturi and a very very large pump.


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## saadat68

4metals said:


> You seem to be confusing a venturi for powering a scrubber with a venturi style exhaust blower. A venturi as in the video is for powering a scrubber and it requires a strong water circulating pump. A scrubber to power a hood is powered with an airflow from an air blower and it causes a venturi effect sucking the air out of the hood to follow the blowers flow. It is used when you have a blower that is not corrosion resistant and you blow clean air up a pipe causing the air in the hood to follow it.
> 
> The reason you use a venturi powered scrubber is to scrub a small quantity of fume being sucked from an enclosed reaction. A flow of 10 CFM is good for that type application.
> 
> A flow of 100 CFM would require a huge venturi and a very very large pump.


Thanks for your response.
But I don't want make venturi scrubber. ( want to use vacuum and I bought a 3 CFM pump for it )

In other topic you say we need 100 CFM for every 1 square foot of opening in your hood
I have a hood with 1 square foot of opening and want to use venturi effect with plain steel blower. So do I must buy 100 CFM blower ? Or must produce 100 CFM from venturi pipe ? ( Sorry for bad English )


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## 4metals

The reason I started the thread about the venturi type fume hood was because a corrosion resistant blower is costly and a lot of members here were not about to go spend about $1000 on a blower. The venturi option is much less expensive. But there are trade-off's. First the efficiency depends on a few things, the number of elbows and the length of the discharge pipe, the diameter of the discharge pipe, and the CFM of the blower. So it is impossible to say how many CFM of actual exhaust you will have from any given size blower. The bigger the blower, the more air you will exhaust from your hood because there is more air dragging hood exhaust up the stack along with the air from the blower. 

Probably some math or physics wiz could figure out actual numbers but I just use a velometer to make sure the air is sucking out of the hood. Don't have a velometer? Find someone who smokes and have them stand right at the face of the hood and blow smoke into the hood. If it all goes into the hood you're good.


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## g_axelsson

The most obvious thing is the placement of the venturi. If it is placed close to the exit with a long suction pipe down to the hood there is less restrictions for the larger air flow after the venturi.
Putting the venturi close to the hood could add too much restrictions so in the worst case it would blow air backwards through the hood. It also requires a thicker ducting to achieve the same air flow from the hood.
Another advantage with placing the venturi close to the exit is that most of the ducting will have under pressure so any leaks will draw air into the ducting instead of pushing fumes back into the work space.

There is a whole science in calculating air speed in ducting, but here are a few links I found.
https://www.cdicurbs.com/ductcal
http://www.engineeringtoolbox.com/ductwork-equations-d_883.html
http://www.engineering.com/calculators/airflow.htm
https://www.thermexcel.com/english/program/duct.htm
Here is a nice equation for calculating the flow through an orifice.  
http://www.tlv.com/global/TI/calculator/air-flow-rate-through-orifice.html
... just saying, imperial units makes my head ache... :twisted: 

Göran


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## saadat68

Thank you understood

Göran
Do you use venturi hood ? 
Can you say what is your blower CFM and your hood size ?


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## g_axelsson

Haven't built my fume hood yet, I'm doing my refining outside.
Working on my plans for the refining lab at the moment though, I finally have a room that I can build it in.

Göran


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## saadat68

Thanks
I make a venturi pipe with my small blower for testing 
suction is really weak. I think need a very big blower for small hood :shock:


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## g_axelsson

Look at this post, the ejector type of venturi would probably work the best. And as I said before, place it close to the exhaust and add pipes down to the fume hood.
http://goldrefiningforum.com/~goldrefi/phpBB3/viewtopic.php?t=10979#p106810

Göran


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## 4metals

I am getting to the point of giving up trying to be helpful here. You posted on this thread, which is about a scrubber design. But you are asking about a hood exhaust design. Please re read the threads you have already read and understand what you are asking and ask in the proper place.

As far as a hood goes, I posted this design a while back on this thread. http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=40&t=19965&hilit=venturi+hood

This design works and I know it does as I used it for years. It's pretty simple, stop trying to re-invent the wheel and just make what is in the picture, I don't know what else to say.


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## saadat68

OK
Thanks
I had read those topics but need to read again


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## ashir

4metals said:


> I am getting to the point of giving up trying to be helpful here. You posted on this thread, which is about a scrubber design. But you are asking about a hood exhaust design. Please re read the threads you have already read and understand what you are asking and ask in the proper place.
> 
> As far as a hood goes, I posted this design a while back on this thread. http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=40&t=19965&hilit=venturi+hood
> 
> This design works and I know it does as I used it for years. It's pretty simple, stop trying to re-invent the wheel and just make what is in the picture, I don't know what else to say.



After finishing my fume hood same as phil and on your design. On the way to make a tower scrubber . 
Make column with concrete and use 3 50 kg crucibles. Inside 2 gas burners and coal to get a maximum600 c tamp. Looking to scrub fumes with your design. 
I want these changes in your design see if these can work
install a blower before concrete column to push the air , air goes through 300 liter tank(half full) with naoh and bubble fumes then fumes goes to another 300 liter tank 
Half filled with water and add a tower 8 inch pvc 10 feet high . Water is sprayed from water tank with pump and spray setup. Not creating a venturi..... add a valve to controle air right after the blower. Blower is 1 Hp 3 phase. 
Water first or naoh first is another topic. 
Not use ventri because can not get venturi ducts in pakistan(somwhere fertilizer suppliers agreed and its 1 month and they are still chcking there stock.. also unable to find required water pumps related to venturi eductor and my personal thoughts are that a 1 or 2 inch vent cannot creat such vaccume that work on 3 crucibles..
Need to install a condenser to keep the scrubber calm w.r.t temprature. 
Long story but i thinks it was necessary to describe so i can get a batter help. . Thanks


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## ashir

4metals said:


> I have been following the thread on building a hood and a scrubber for a long time now and it has gotten pretty long. This scrubber works on a different principle than the one in that thread and was inspired by a client of mine who didn't want to spend the money on a good vacuum system and a good scrubber, but he needed both.
> 
> I had posted a thread on building a vacuum system https://goldrefiningforum.com/phpBB3/viewtopic.php?f=40&t=4640]How to build a vacuum filtration system[/url] some time ago and it is the type of system required for a strong, commercial operation. Usually refiners processing 100 oz plus lots will benefit from the system.
> 
> This scrubber uses a feed similar to the vacuum system and is based on the principle that the eductor pulls air through the venturi and in addition to creating a vacuum, it pumps the air it pulls. By pumping that air into an air tight scrubbing chamber the fume has no place to go but along the airpath and through the scrubber. Plus with a 10 CFM eductor, the time the fumes remains exposed to your scrubber chemistry is exceptionally long for an effective reaction.
> 
> As a bonus to this design by using the exhaust over a sealed reactor, 100 ounce digestions are completely handled by the 10 cfm flow. A side bonus is that by shutting off the feed line that pulls air for scrubbing and opening up a line set up to vacuum filter, you can filter and scrub fumes with the same piece of equipment, just not at the same time.venturi scrubber.jpg
> 
> This setup can be pH controlled automatically or for a small shop, daily opening the access port to adjust the pH should suffice. The principles of scrubbing are the same, as is the packing but for someone digesting 100 ounce lots, this system is effective.
> 
> Now it's time to have our DIY crowd tear into this design to see what we end up with.



I got two venturi educters. 1 inch on 1-1/2 inch



To its suction size they install a shield and a ball with spring




With and without spring and ball, eduCter not produce vacume or very little vaccume.
I have a magnetic motor pump. I think pump is too small.



See its label and there is not much info about pump.
Any help?


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## Martijn

The washer, spring and ball are a checkvalve to prevent backflow into your vacuum line. 
The pump produces 15 l/h at 0.8 bar if i read it correct. 
What is the operating pressure of the venturi? It should be in the manual or on the box it came in? You need enough pressure and flow for the venturi to work. 
Martijn.


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## butcher

There is not really that much difference between an air compressor and a vacuum pump, except maybe which end of the machine the hose is being used on, being on the end that sucks instead of blows.

You can build a simple homemade vacuum pump, using a barrel of water with a spout or bung, one at the top and one on the bottom of the barrel, the bottom valve is to let water out of the barrel, the valve at the top of the barrel is used to fill the barrel with water or for the vacuum hose attachment.

From this closed barrel full of water, opening the bottom valve the water drains from the barrel by gravity, the barrel being closed begins to pull a vacuum from the top valve, a hose attached to the top valve becomes a suction source or vacuum, this vacuum will continue as long as there is water being drained from the main barrel

by using another barrel that can act as a receiver or storage container for the water to drain into from the first (vacuum barrel), and you can then reuse the water from this second barrel to re-fill the first working vacuum barrel, you can use a pump or just transfer the water or just transfer the water by hand from the receiver barrel back into the main vacuum barrel.


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## ashir

butcher said:


> There is not really that much difference between an air compressor and a vacuum pump, except maybe which end of the machine the hose is being used on, being on the end that sucks instead of blows.
> 
> You can build a simple homemade vacuum pump, using a barrel of water with a spout or bung, one at the top and one on the bottom of the barrel, the bottom valve is to let water out of the barrel, the valve at the top of the barrel is used to fill the barrel with water or for the vacuum hose attachment.
> 
> From this closed barrel full of water, opening the bottom valve the water drains from the barrel by gravity, the barrel being closed begins to pull a vacuum from the top valve, a hose attached to the top valve becomes a suction source or vacuum, this vacuum will continue as long as there is water being drained from the main barrel
> 
> by using another barrel that can act as a receiver or storage container for the water to drain into from the first (vacuum barrel), and you can then reuse the water from this second barrel to re-fill the first working vacuum barrel, you can use a pump or just transfer the water or just transfer the water by hand from the receiver barrel back into the main vacuum barrel.



Martijin thanks. I did massage to supplier and he was nable to provide any info. 

Thanks butcher , i will check today as you said and inform you. For fume hood i use phildig design with 7 cfm vaccume pump. 

I was building a furnance to maximum 600 tamp. 
The furnance has it own saperate outlet. But fumes from crucibles are to be scrub. 
Fumes from the crucbles are corrosive . Looking to push fumes inside scrubbing liqued and the pass from a paked tower. Looking to use one already shown pum for mixing gases from furnance and a saperate pump in pcked tower.


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