New fume scrubber design

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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. IMG_1725.jpg

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.
beaker hood with drops 2.JPG
 
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?
 
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
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Thank you for all the information, it's really appreciated. When I get rolling I'll post my progress.
 
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.
 
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.
 
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.
Click to expand...
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 )
sqau__lk_ygigy.jpg
 
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.
 
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. :D
http://www.tlv.com/global/TI/calculator/air-flow-rate-through-orifice.html
... just saying, imperial units makes my head ache... :twisted:

Göran
 
Thank you understood

Göran
Do you use venturi hood ?
Can you say what is your blower CFM and your hood size ?
 
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
 
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:
rmq6_5841.jpg
 
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
 
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.
 
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.
Click to expand...

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
 
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.
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I got two venturi educters. 1 inch on 1-1/2 inch
IMG_20210121_143812.jpg

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

IMG_20210121_143840.jpg

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.
IMG_20210121_143901.jpg

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