how to build an acid resistant hood & scrubber _hood_

[HAuCl4]

Goldie: Our fellow refiner kadriver has a fine thread in the chemical processes section, where he goes through the steps with pictures one by one. if you study that thread, then you can build the rest of your setup around that core process.

He also has another thread for silver.

Good luck, and take it slowly, one step at a time, and start with a small amount first.

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=37&t=8322

 

[golddie]

Hi qst42know
Thanks for your help I appreciate that
I bought it as a 6 inch pipe but I think it is a bit larger and it is something like 7 or 8 inches
I will go to my shop and measure it to say exactly how much it is
I have a damper right above the fume hood would I have to change that as well and how about the pipe that is connected to the blowers exiting rectangular hole

I have drawn a new sketch to show in detail about my system
http://img687.imageshack.us/i/26984497.jpg/
I think I have many flaws with the arrangement
The pipe that is attached to the bucket is making a sharp turn and it is affecting the force of the blower
This blower model can be moved around so that you can change the angle of the blower but if I remember right I thought it was not possible to move it the get better angle for performance


Hi HAuCl4
Thanks for that link I appreciate that

 

[qst42know]

A couple questions.

The 3" lines in your drawing are these the only connection to your hood?

I see your manifold feeds through the scrubber. Is there a reason the hood itself doesn't feed through the scrubber as well?



I think you would be happier with the performance of your hood if you went with 10" PVC duct like this.

http://www.usplastic.com/catalog/item.aspx?itemid=23954&catid=723

 

[golddie]

Hi qst42know
Thanks for your help

The 3" lines in your drawing are these the only connection to your hood?

Yes
I made the system according to the sketch 4metals posted
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=40&t=4776
I never knew what a scrubber was until I started using this forum

10" PVC duct

If you look in the picture I have written bucket I think a 10" pipe would be difficult to fit in there.
It will be a very difficult task to change those pipes and I said maybe I can just refine small amounts for now and maybe later on I will do changes to this system.
It seems like an easier task to add a small blower and let the air out the window that will be easier like Emmjae hood
Also I can bring more air from the front part of the room with a fan or a blower
Today all I did was close all the leaks and there was so many because I used duct tape and that was no good so what I did was I used aluminum tape to cover over those duct tape and it seemed like it was perfect.
Barren was the one who gave me the idea to use aluminum tape thanks to him.
The biggest leaks were at the places where the pipe that lead to the entrance and exit holes of the blower
If I have the chance I will test the system tomorrow.
Thanks again

 

[qst42know]

The further your components are and the more turns you need to make the larger the duct would need to be. 10" may be excessive but 3" seems to restrictive for all but the smallest bench top hood. I suppose I assumed your system was very large based on your large scrubber.

Something is very wrong with the system if you are considering a space suit to work in.

 

[golddie]

Hi qst42know
I thought it would be a better idea to have 2 pipes that was 3" in the sides of the hood way I the system might work better than to have 6" in center.
Also I patched up lots of leaks yesterday so that means there was a major problem with leaks.
But one thing is for sure if the air is not clean I will not do any refining there
There are tools for testing the quality of air and I was wondering what kind of a meter would be suitable for this purpose
Thanks

 

[PreciousMexpert]

I thought it would be a better idea to have 2 pipes that was 3" in the sides of the hood way I the system might work better than to have 6" in center.

I am wondering if this is a good idea or by having 2 pipes you reduce the suction power of those 2 holes

 

[Barren Realms 007]

I thought it would be a better idea to have 2 pipes that was 3" in the sides of the hood way I the system might work better than to have 6" in center.

I am wondering if this is a good idea or by having 2 pipes you reduce the suction power of those 2 holes

You have a chance of reducing the airflow by a small percentage but if you have everything calculated for flaws you will be ok. Any time you desighn something that has to do with air flow you ever desighn for your airflow because you have things like 90's, filters and unseen things that can effect your flow rate. Never figure on the bare minimum.

 

[golddie]

I am removing all the duct tape and replacing them with aluminum and I boiled a small amount and already the air seemed very clean

 

[golddie]

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=40&t=4776

Next to the scrubber there is a smaller container and when I open that the smell is very strong.
There is lye in there and the usual brown colored liquid and I see that those carbon masks are not effective when it comes to nitric acid.
How about in this case can I use those carbon masks.
Thanks

 

[rbramsey]

Hi qst42know
I thought it would be a better idea to have 2 pipes that was 3" in the sides of the hood way I the system might work better than to have 6" in center.

FYI, two 3" pipes are not = one 6" pipe. It takes 4 - 3" pipes to equal the area of 1 - 6" pipe. Two 3" pipes would be equivalent to 4.5" pipe. This is not accounting for any efficiency loss or drag.

Area of a circle = pi * R * R
area of 6" pipe = 3.14159 * 3 * 3 = 28.2743 sq in.
area of 3" pipe = 3.14158 * 1.5 * 1.5 = 7.0686 sq in

# of 3" pipes = 6" pipe
7.0686x = 28.2743
x= 28.2743 / 7.0686 = 3.9999

I thought this would be important with you using this for a fume hood.
Richard

 

[golddie]

Hi rbramsey
I appreciate your help
I did some testing with my fume hood and scrubbing system and I see that I have to do some changes to it.
I have a few ideas and the one that I like the most is to place a blower right behind the fume hood the way Emmjae has made his fume hood and direct it to the outside window
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=40&t=4776&start=320

I am using 2 - 120 cfm bathroom exhaust fans

http://img695.imageshack.us/i/66305214.jpg/
If I do this than I will have 2 right angles in the line and I will be about 2 feet away from the exhaust hole
Or I can bring it from the side of the fume hood and there will be about 1 feet of distance from the ingoing hole to the outgoing hole


Or I can change the 2 pipes that are 3 inches each and place a 6 inch pipe there but I will be 7 feet away from the blower and I will have 4 sharp curves in the line

 

[golddie]

120 cfm bathroom exhaust fans

I am buying 2 of these tomorrow and I have 3 questions.
1) Should I buy this since its working well for Emmjae and why change something that's working
or should I buy a more powerful blower
2) What size pipes should I use
3) Should I attach these fans to the fume hood or to the window
Thanks

 

[PreciousMexpert]

http://www.balco.co.uk/fume_enclosures.shtm

Maybe you can build something like this.
You need to have the blower sucking in the air and also another blower from the bottom suppling air
Can anyone explain this in more details like for a box like this what size of a blower is needed for sucking in air and what size to supply air

 

[Barren Realms 007]

http://www.balco.co.uk/fume_enclosures.shtm

Maybe you can build something like this.
You need to have the blower sucking in the air and also another blower from the bottom suppling air
Can anyone explain this in more details like for a box like this what size of a blower is needed for sucking in air and what size to supply air

It looks like this only has one blower. It possibly has a damper that only opens on negative pressure in the cabinet and then closes when the blower is off.

 

[golddie]

I have the option to use this
http://img243.imageshack.us/i/45799197.jpg/
http://img217.imageshack.us/i/69171836.jpg/

 

[golddie]

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=40&t=8177
If you look here this is something I can relate to and from reading this I see that maybe the motor for that blower is too week.

A 4 x 8 opening needs 3200 cfm for good exhaust.

The motor for my blower is 650 cfm
This is the blower for the fume hood and the scrubber.
The problem of changing that motor is very difficult so I have to plan well and do the right thing so that I can add the 2 bathroom fans there or something better
So any advice before I do it will be a big help
I have been making too many mistakes for something that is critical and a matter of life and death

The size of my fume hood is about the same size as Emmjaes
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=40&t=4776&start=320
Thanks

 

[Emmjae]

@ golddie

Here are the fans that I am using. They are a ceiling mount type that require an 8-1/2" x 9-1/16" opening each.

http://www.rewci.com/120-cfm-high-performance-fan.html

When I built this hood I had no clue as to what was required for fan/cfm size. I am by no means an expert or experienced at this type of construction. I keep my plexiglas front closed at all times while I'm using it. My remaining opening is 46" x 10". Based on what I have learned since I built this I am undersized by 220 cfm. What I'm not sure of is if that 100 cfm x sq.inch of opening requirement factors in for a scrubber draw too.

When I decided on using 2 - 120 cfm bathroom exhaust fans I looked at how many air changes per minute they would provide based on the total cubic foot of area inside my hood.

Inside dimensions are 46" L x 26"D x 36"H. = 52,416 cubic inch / 1728 = 30.33 Cubic Foot. Divide by 60 mins. = .5055 CFM needed for 1 air change per minute. I am using 2 - 120 cfm fans = 240 CFM / .5055 = 474.77 total air changes per minute. (If my math and figuring are correct) That seemed like enough to me and it does work well in my opinion.

Mounting my fans directly on my hood gave me no air restrictions at the entry point of the fans. I have the 4" exhaust ports pointed up and is vented straight up through my roof at a distance of about 12'. There should be some CFM loss due to that length along with the 1" filters I have mounted over each fan. I believe that with my 46" x 10" front opening I'm creating enough velocity/draft to draw the fumes up and out the exhaust fans pretty well. While experimenting with different opening sizes, I could increase the velocity/draft by decreasing the front opening size up to the point of the size of my fan openings. Keep this in mind while your constructing your hood opening.

Mike

 

[golddie]

Hi Mike

Before starting a project we do all kinds of research but when it comes to actually making the job, situations change and we are faced with unforeseen problems and that's because we are doing something that is not related to our profession.

You say this is not your field but I am really impressed with your method of calculating the measurements to find out the requirements of the cfm.

46" L x 26"D x 36"H. = 52,416 cubic inch / 1728 = 30.33 Cubic Foot. Divide by 60 mins. = .5055 CFM
needed for 1 air change per minute. I am using 2 - 120 cfm fans = 240 CFM / .5055 = 474.77 total air changes per minute.

It would be nice if someone could make these calculations more understandable for the average person


The size of my fume hood is practically the same as yours and you say you are happy with the performance of these fans.
The only thing I don't understand is this

I built this I am undersized by 220 cfm.

Those filters look like the ones I bought from my hardware but they are not 1 inch
Thanks for your help.

 

[Emmjae]

Hi Golddie

From what I have read, they recommend 1 cfm per 1 square inch of opening. My hood has an opening with the plexiglas front down of 46" x 10" = 460 square inches. That equates to needing 460 cfm of fan. I have 240 cfm of fan meaning I am undersized by 220 cfm, based on what is recommended.

And yes, my filters are just a standard furnace filter 16" x 20" x 1" from Ace hardware. I had a case of filters left over from my old furnace that's been laying around. Figured for now it was better than using nothing

Mike