Building a chemical fume hood with a plain steel blower

[butcher]

Thank you for clarifying the metal you are using, it is hard to tell the metal you are using from just seeing the pictures.

GFCI protection for electrical would be a must.

Reading 4 Metals, and many of the other member posts on fume hoods and scrubbers, should help you in building one suitable for your processing needs.

Do not process anything in your living area these fumes will kill.

 

[Clneal2003]

Now when you need to pour waste into a drum it is no longer a funnel full of stinky acid poured while holding your breath, it is simply uncapping the pipe, inserting the funnel, and pouring inside the vented hood.

Amen! I'm totally going to use your model here as my first hood if you don't mind. Did the fumes just blow out a duct on top of your shed? I'm still really small time but am constantly looking for ways to simplify this...

Right now I march back and forth from the house grabbing jug after jug of solutions and jars. Constantly putting stuff up and pulling stuff outside depending on the weather.

Oh yeah... What material did you use for the interior?

 

[saadat68]

Can someone say to me is there a hole on top of the bottle ? If no, So I think vacuum pump break it. right? :shock:

 

[4metals]

The flask is vented from a hole in the stopper on top of the flask.

 

[autumnwillow]

4metals there's a hole in that setup?

Mine doesn't have any. If he is going to use 2L nitric acid thats going to leak for sure.

Saadat make your own thread and post pictures there, we'll help you from there.
If you make a closed system like this you can work indoors. And you will use half of the acid that you normally use as a closed system is more efficient. It can also scrub 99% of the fumes while you can recycle all of the wastes generated by the scrubber.

 

[saadat68]

4metals there's a hole in that setup?

Mine doesn't have any. If he is going to use 2L nitric acid thats going to leak for sure.

Saadat make your own thread and post pictures there, we'll help you from there.
If you make a closed system like this you can work indoors. And you will use half of the acid that you normally use as a closed system is more efficient. It can also scrub 99% of the fumes while you can recycle all of the wastes generated by the scrubber.

Thanks you 4metals and autmnwillow
but if your flask doesn't have any hole, why pump doesn't break your flask ?

 

[autumnwillow]

Thanks you 4metals and autmnwillow
but if your flask doesn't have any hole, why pump doesn't break your flask ?

The vacuum is strong enough to break plastics containers, not borosilicate glass for lab use.

 

[4metals]

If you suck air out of the flask and do not replace the air (from the hole in the stopper on top) you will have a flask under vacuum. A reaction that is happening in the flask under vacuum is more inclined to boil over, in addition an erlenmeyer flask is not the most desirable vessel for a digestion because as the solution rises with the reaction, the surface area inside the vessel decreases, the higher it rises the smaller it gets and the faster it rises. The word volcano comes to mind!

The hole in the top stopper allows air in and allows air plus fume to be scrubbed to be pulled through the the scrubbing device. Without a hole there is no flow.

 

[FrugalRefiner]

I like to use a thistle tube in the hole. It makes acid additions to the flask very easy.

Dave

 

[saadat68]

Thanks guys I think I am ready to start for make a scrubber. I understood what I want now. But I must buy a stopper and drill it ? How big is the hole ? is 1.5 mm diameter enough ?

I like to use a thistle tube in the hole. It makes acid additions to the flask very easy.

Dave

Isn't it very small ? how you pour acid from this tube? :shock:
Edited: No I think it have good size
https://www.alibaba.com/product-detail/Glass-Thistle-funnel-long-stem-funnel_60098651164.html?spm=a2700.7724838.0.0.la4DLA

 

[Shark]

I like to use a thistle tube in the hole. It makes acid additions to the flask very easy.

Dave

Thanks Dave, I had been wondering what that tube was called.

 

[autumnwillow]

If you suck air out of the flask and do not replace the air (from the hole in the stopper on top) you will have a flask under vacuum. A reaction that is happening in the flask under vacuum is more inclined to boil over, in addition an erlenmeyer flask is not the most desirable vessel for a digestion because as the solution rises with the reaction, the surface area inside the vessel decreases, the higher it rises the smaller it gets and the faster it rises. The word volcano comes to mind!

The hole in the top stopper allows air in and allows air plus fume to be scrubbed to be pulled through the the scrubbing device. Without a hole there is no flow.

I agree and disagree here. I would agree if the reaction isn't that violent but I would disagree if the reaction is otherwise. As I have experienced, the rubber stopper actually bouncing out and giving off fumes. In order to prevent it, I had to increase the vacuum pressure. Now if this would happen where I had a hole in that rubber stopper, it would end up spewing gasses or liquid boil overs. I would rather have that gasses/boil overs pass through my condenser and scrubber system rather than spewing elsewhere.

I also do not think that you need to refresh the air inside the reaction vessel as the reactions usually produce gasses as their byproduct. If I were to put a hole, I would have to increase the vacuum pressure which could probably lead to fumes not being scrubbed well as retention time is a key in scrubbing NOx fumes. And everytime I increase the vacuum pressure I end up with an acidic smell at the vacuum exhaust.

Correct me if I am wrong though.

Saadat,
You can use the smallest glass funnel instead.

And here's your shopping list:
Vacuum pump 3cfm (doesn't have to be a chemical type one, a normal one will last as long as you have setup the scrubbing system well)
Bleeder valve for vacuum pump.
Condenser system.
Teflon hose (for the connection between reaction vessel and the condenser, common hoses will deteriorate fast due to heat and chemical attack)
Common hoses - for connecting one scrubber unit to another
Pipes and fittings
Filtering flasks or PVC drums as scrubber units. (Filtering flasks are expensive but they are really an eye candy, PVC drums are cheap)
Bio balls as media for scrubber unit.

 

[Barren Realms 007]

If you suck air out of the flask and do not replace the air (from the hole in the stopper on top) you will have a flask under vacuum. A reaction that is happening in the flask under vacuum is more inclined to boil over, in addition an erlenmeyer flask is not the most desirable vessel for a digestion because as the solution rises with the reaction, the surface area inside the vessel decreases, the higher it rises the smaller it gets and the faster it rises. The word volcano comes to mind!

The hole in the top stopper allows air in and allows air plus fume to be scrubbed to be pulled through the the scrubbing device. Without a hole there is no flow.

I agree and disagree here. I would agree if the reaction isn't that violent but I would disagree if the reaction is otherwise. As I have experienced, the rubber stopper actually bouncing out and giving off fumes. In order to prevent it, I had to increase the vacuum pressure. Now if this would happen where I had a hole in that rubber stopper, it would end up spewing gasses or liquid boil overs. I would rather have that gasses/boil overs pass through my condenser and scrubber system rather than spewing elsewhere.

I also do not think that you need to refresh the air inside the reaction vessel as the reactions usually produce gasses as their byproduct. If I were to put a hole, I would have to increase the vacuum pressure which could probably lead to fumes not being scrubbed well as retention time is a key in scrubbing NOx fumes. And everytime I increase the vacuum pressure I end up with an acidic smell at the vacuum exhaust.

Correct me if I am wrong though.

Saadat,
You can use the smallest glass funnel instead.

And here's your shopping list:
Vacuum pump 3cfm (doesn't have to be a chemical type one, a normal one will last as long as you have setup the scrubbing system well)
Bleeder valve for vacuum pump.
Condenser system.
Teflon hose (for the connection between reaction vessel and the condenser, common hoses will deteriorate fast due to heat and chemical attack)
Common hoses - for connecting one scrubber unit to another
Pipes and fittings
Filtering flasks or PVC drums as scrubber units. (Filtering flasks are expensive but they are really an eye candy, PVC drums are cheap)
Bio balls as media for scrubber unit.

As 4metals said you need a hole in the top of your rubber stopper to allow air in. If you feel you are in need of more vacuum capacity put you a tank between your vacuum pump and you columns. Then you can have a valve you can regulate how much vacuum you pull.

 

[4metals]

If you do not have a vent your reaction you will have a run away boil over because liquids boil at lower and lower temperatures the higher the vacuum pressure. An absolute vacuum is about 29.9 inches of mercury, at that vacuum water vaporizes quickly. But even a slight vacuum has effect on boiling points of liquid. In Denver Colorado, the mile high city, water boils at 203^oF (95^oC) because there is less atmospheric pressure bearing down on the water boiling in that city.

Your vacuum source is capable of the same result, only much more extreme as better vacuum pumps and venturi's are capable of getting a very strong vacuum.

If you don't allow atmospheric air in you may be able to shatter the glass, but I doubt that because those vacuum flasks are designed to withstand a strong vacuum, but you will greatly enhance your chances of a boil over. Aqua regia likes a little bit of pressure and it actually reacts better. Vacuum not so much!

 

[saadat68]

If you suck air out of the flask and do not replace the air (from the hole in the stopper on top) you will have a flask under vacuum. A reaction that is happening in the flask under vacuum is more inclined to boil over, in addition an erlenmeyer flask is not the most desirable vessel for a digestion because as the solution rises with the reaction, the surface area inside the vessel decreases, the higher it rises the smaller it gets and the faster it rises. The word volcano comes to mind!

The hole in the top stopper allows air in and allows air plus fume to be scrubbed to be pulled through the the scrubbing device. Without a hole there is no flow.

I agree and disagree here. I would agree if the reaction isn't that violent but I would disagree if the reaction is otherwise. As I have experienced, the rubber stopper actually bouncing out and giving off fumes. In order to prevent it, I had to increase the vacuum pressure. Now if this would happen where I had a hole in that rubber stopper, it would end up spewing gasses or liquid boil overs. I would rather have that gasses/boil overs pass through my condenser and scrubber system rather than spewing elsewhere.

I also do not think that you need to refresh the air inside the reaction vessel as the reactions usually produce gasses as their byproduct. If I were to put a hole, I would have to increase the vacuum pressure which could probably lead to fumes not being scrubbed well as retention time is a key in scrubbing NOx fumes. And everytime I increase the vacuum pressure I end up with an acidic smell at the vacuum exhaust.

Correct me if I am wrong though.

Saadat,
You can use the smallest glass funnel instead.

And here's your shopping list:
Vacuum pump 3cfm (doesn't have to be a chemical type one, a normal one will last as long as you have setup the scrubbing system well)
Bleeder valve for vacuum pump.
Condenser system.
Teflon hose (for the connection between reaction vessel and the condenser, common hoses will deteriorate fast due to heat and chemical attack)
Common hoses - for connecting one scrubber unit to another
Pipes and fittings
Filtering flasks or PVC drums as scrubber units. (Filtering flasks are expensive but they are really an eye candy, PVC drums are cheap)
Bio balls as media for scrubber unit.

Very good post
Thanks a lot
I have some questions
#I don't want use Condenser lab. no problem?
#Can I use another hose or pipe instead of teflon hose ? I don't think I can find them here!
#Which type of bleeder valve I must use

 

[4metals]

#I don't want use Condenser lab. no problem?

A condenser will do 2 things for you, it will condense nitric fumes and extend the life of your acid, so you need less nitric. And second it cools off the fume making it easier to scrub effectively. That's why I like to use them.

#Can I use another hose or pipe instead of teflon hose ?

You can use PVC or even vinyl hose. The hose will get soft and go limp before it fails so just keep checking it. Teflon is the best but the best is also costly.

#Which type of bleeder valve I must use

I would just insert a short length of tubing or a thistle tube as Dave suggested. You do not want to shut it off so why add a valve.

 

[saadat68]

#I don't want use Condenser lab. no problem?

A condenser will do 2 things for you, it will condense nitric fumes and extend the life of your acid, so you need less nitric. And second it cools off the fume making it easier to scrub effectively. That's why I like to use them.

#Can I use another hose or pipe instead of teflon hose ?

You can use PVC or even vinyl hose. The hose will get soft and go limp before it fails so just keep checking it. Teflon is the best but the best is also costly.

#Which type of bleeder valve I must use

I would just insert a short length of tubing or a thistle tube as Dave suggested. You do not want to shut it off so why add a valve.

Thanks 4metals again
Yes I read in another topic bleeder valve is not necessary. and about condenser it is good idea. I don't like it!!! prefer don't use but maybe use it

 

[FrugalRefiner]

#Which type of bleeder valve I must use

I would just insert a short length of tubing or a thistle tube as Dave suggested. You do not want to shut it off so why add a valve.

Autumnwillow mentioned a "Bleeder valve for vacuum pump". I believe he's probably using this valve to control the amount of vacuul applied to the reaction vessel and scrubber system. Based on this assumption, I further assuming that he uses this valve after the scrubber system, between the scrubber and the vacuum pump. By putting a valve here, he can limit the vacuum placed on the system before it. In that way, he doesn't have a problem with extreme vacuum building up in the reaction vessel or scrubber that could break the flask or collapse a scrubber.

With some tweaking, you can combine both systems. The bleeder can slow the passage of fumes through the scrubber, increasing its efficiency, but there is the risk that without close monitoring, the bleeder could be opened too much, allowing fumes to escape through the thistle tube.

Dave

 

[saadat68]

#Which type of bleeder valve I must use

I would just insert a short length of tubing or a thistle tube as Dave suggested. You do not want to shut it off so why add a valve.

Autumnwillow mentioned a "Bleeder valve for vacuum pump". I believe he's probably using this valve to control the amount of vacuul applied to the reaction vessel and scrubber system. Based on this assumption, I further assuming that he uses this valve after the scrubber system, between the scrubber and the vacuum pump. By putting a valve here, he can limit the vacuum placed on the system before it. In that way, he doesn't have a problem with extreme vacuum building up in the reaction vessel or scrubber that could break the flask or collapse a scrubber.

With some tweaking, you can combine both systems. The bleeder can slow the passage of fumes through the scrubber, increasing its efficiency, but there is the risk that without close monitoring, the bleeder could be opened too much, allowing fumes to escape through the thistle tube.

Dave

I prefer don't use it
Thanks
Why this forum doesn't have thanks button? :?

 

[autumnwillow]

Mind you that I had no condenser before, and the hoses and pvc were deteriorating, condensations occuring everywhere. Even the scrubber liquids were overflowing due to condensations. I re-designed and used a teflon and condenser and I no longer had any clean ups to do.

I also did not have any bleeder valve before to control the vacuum. I ended up having to put very little acid in order to avoid too much fumes from being generated. And this took too much time.

As soon as I modified my lab everything was running so fast that the small money that I've spent is well worth for what it is capable now.

A bleeder valve is easy to build. Its just a valve that connects to your vacuum pump.

Vacuum pump -> hose -> T fitting (1 for scrubber, 1 for a gate valve)