Non-Chemical techniques for ASH

[alb320]

Hi guys,
I have a 60 kg of refractary ash then contains 194,4 gr of gold.
What is the best way for recover it? AR or MELT it?
If I have to melt it, what melting additive I have to use?
Thank you a lot

 

[Harold_V]

It would be difficult to recover by melting due to the nature of the refractory material. It also may not respond well to chemical treatment.

It might help to know more about the nature of the refractory material, and the gold as well. Can you better describe each of them? How the gold is disseminated in the refractory could make a huge difference in how it might be successfully processed. Something as simple as crushing and panning could yield acceptable results.

Harold

 

[alb320]

I had some used little crucible like this:

 

[alb320]

I have crushied it and burned it.
I have make analysis from this ash and I have found 194,4 gr.
I don't know how the gold is disseminate... I know that crucilbes has used for melt gold's filings....
Have you some advice for me?
Thank you a lot...

 

[Harold_V]

It's a shame you crushed them. They could have been cleaned with soda ash and borax, yielding nice buttons of alloy. I'm assuming they were melting dishes used by jewelers, not assay items, where they may be contaminated with lead. If they contain lead, I'd advise you not mess with them unless you can control the fumes.

I'm not sure it would work, but you may be able to heat the crushed material in a large crucible with borax, soda ash and some silver to act as a collector. It would be hard on the furnace and crucible, but if you have the flux thin enough, and cook them long enough, it's possible you'd recover the values. Flux can be thinned by the addition of a little fluorspar, but it is very hard on crucibles and furnace lining. I can provide a flux recipe, but a decent furnace is a requirement.

Harold

 

[alb320]

Thank you Harold!!
I have 4 furnace in my little foundry... and I think that I could test your fluxe recipe...

 

[Harold_V]

Ok, here's what I used:

(3) parts waste material

(1 1/2) parts silica sand

(3 1/2) parts soda ash

(1/2) part fluorspar

(2) parts borax

My material had a great deal of silver chloride included, which acted as a collector. My results were very acceptable, with the flux being totally free of prills and assaying well under a value that would warrant further treatment.

I recommend you assay your flux after a pilot run to insure that you are achieving the success you desire. My material was high in silica, which I think is unlike yours. This may not work as well for you, depending on the nature of the crushed material you have. If the crushed dishes are silica based, you will achieve very good results, and may even be able to eliminate the addition of the silica sand that is mentioned in the flux formula. It will be to your advantage to use a collector with your material. Silver or gold will work well, but you can even resort to using some copper.

In order to eliminate dusting of my material, and loss in the exhaust, I mixed the above ingredients in a small bucket, then added enough water to form a batter that would pour easily. It was then poured to lids from plastic ice cream buckets. A rapid chemical reaction turned the batter to hard cakes, which were then removed from the plastic forms and allowed to air dry. Before introducing them to the furnace, I would strike each one in the center with a small hammer, breaking them into pie shaped pieces, making it easy to introduce them to the furnace. In my case, the furnace used no crucible, melting directly in the lining.

When the material is heated, it will grow in volume, frothing up as it melts. Allow room for the frothing, so you don't overflow your crucible. Once you understand how much it froths, you will know how much you can start with. I suggest you start with a crucible filled only about 25% to avoid overflowing.

Be certain to heat long enough for the material to melt totally, and become tranquil. Pour to a cone mold only when you have insured an adequate heating period. The flux should be very thin, not viscous. If you find it pours quite stiff, you must either heat longer (hotter), or add more fluorspar. Add more fluorspar only if you absolutely must-----it accelerates the destruction of your furnace and crucible.

Hope some of this helps!

Harold

 

[alb320]

Thank you a lot harold,
next week I try your recipe.
I am intrigued of your furnace... without crucible, How does it work?
how can you heat your lining? Is the flame inside furnace?

 

[scrapdealer]

Hi Harold
That's a good looking pot you've got there... Very professional.
Have you a fixed spout type crucible inside.? What material is it made of.?
Regards
Peter

 

[Harold_V]

The furnace was cast with a 94% alumina castable material. The trunnion on the far side, through an elbow, acts as the port, which is also the igniter. No crucible is used, nor is there anywhere for one. The chamber of the furnace resembled the shape of a bilge type crucible, however. Melting is accomplished directly in the lining.

To fire the furnace, all that was required was to start the fan, open the gas valve and throw the ignition switch. Combustion was instantaneous, at which time the switch was turned off. A spark plug in the elbow leading to the port ignited the flame. It works in every way the same way a crucible furnace does, but without a crucible, and it tilts to pour. The flame entered the furnace tangent to the inside diameter, such that it created a swirl of flame around the perimeter of the cavity. The entire interior of the furnace became yellow hot in short order. A furnace of this type is commonly known as a reverberatory furnace. They rely on reflected heat to heat the charge. I was limited in volume by the location of the port, but had a capacity of about two gallons. Needless to say, it's very important to keep the port free from the contents of the furnace.

The furnace was of my own design, including the burner assembly and swivel assembly that allowed the furnace to rotate on the trunnion. It helps a great deal to be a machinist and have the necessary equipment. Much of the tilt mechanism required machining, as you might imagine.

Here's a shot of the other side.

Harold

 

[Platdigger]

That thing is a beaut Harold!
Randy

 

[scrapdealer]

Harold
Thanks for the explanation & photo. All is clear now one can see the opposite side of the furnace in the upright.
For the past 20 years or so I have played on large professionally built reverb's & rotary's for melting aluminium alloys, however it is always a real pleasure to see some of the wonderful innovative ideas you guys come up with. Very impressive....
Regards

 

[alb320]

Very cool Harold!
My little foundry is in activity since 30 years, we have change 40 furnaces, but I haven't never seen a furnace like this... This project is very interesting... I think that I will try to make one like this!
Thank you soo much!!!

Your advices has helped me!!

 

[Harold_V]

alb320,

Very happy to have been of service. I'd be pleased to hear about your results, so please keep us posted on your progress.

How's things in Italy?

My family comes from Greece----Megara, near Athens.

Harold

Edit:

If you feel more pictures would be helpful, I have several taken during construction. They show the types of forms used, and the building sequence.

 

[alb320]

Yes harlod, I have posted a question for an AR rector last month.. but I haven't installed it yet... When I test it I post my progress.

For this refractory material, I melt it next week, and I will keep you informed of my progress.

Ok, If you could post me some pictures of building sequence I'm very grateful to you.

I live in Milano, and at this time we live well... but we fell economic world crisis, it's hard to work now. I hope that it will change as soon as possible...

Ohhh... Greece... it's a beautiful country... best sea, best city... good idea to go there!

And In Washington? How is things?

 

[butcher]

harold the gas line on your furnace seems to tee into the induced air path tith a gate valve, do you have an orfice? and where in it if so. and what seals the trunion swivel? is the amount of air from fan controlled by the gate valve? that really is a well built furnace great job.

 

[Harold_V]

harold the gas line on your furnace seems to tee into the induced air path tith a gate valve, do you have an orfice?

I don't recall any of the details now, but I experimented with the venturi effect before I built the mixing chamber. The gas is introduced without an orifice, and is pulled into the main stream by the air flow. I used two sizes of pipe and experimented with the offset, one from the other. It seemed to work very well, but I have used natural gas without the mixing chamber with pretty much equal results. As long as you introduce the gas to the moving air stream, seems to work fine.

what seals the trunion swivel?

I mentioned having to machine a great deal of the furnace. I used a Teflon O ring, with the gland inside the swivel. The incoming air kept it within acceptable temperature limits. I kept the airflow going after shutting down operation, to insure that the O ring didn't get heated beyond safe limits. They're good to 500° F. To insure reasonable alignment without binding, I used a short length of wire reinforced hose to connect the blower to the swivel. You can see the hose clamps that were employed.

is the amount of air from fan controlled by the gate valve?

Yes. It's important to be able to throttle such a furnace, to keep combustion where it's desired. I also used a gate valve for the natural gas. In my case, I had 1 pound of delivery pressure, so I could get by with relatively small diameter pipe and hose. You likely know that normal pressure is only a few ounces.

that really is a well built furnace great job.

Thank you! I appreciate your comments. The project took a great deal of time, but I was rewarded with a furnace that exceeded my expectations. I was also rewarded with a huge return of values, having saved incinerated waste materials for more than 20 years. It was instrumental in my early retirement (age 54).

Harold

 

[Harold_V]

Ok, If you could post me some pictures of building sequence I'm very grateful to you.

I'll send the pictures I have in our scrap book. They've already been scanned. What I need is your email address. You need not post it here, but you can click on the email button on the bottom of this post. That will allow you to send me an email directly, on which you should include your email address. I'll send the pics to you that way. I would do it directly, but you did not provide your email address on your profile page, so I don't have it available to me.

Do you have a high speed connection? If not, I can send them one at a time, one each day, so you don't get overwhelmed. Let me know. There's only about seven pictures.

Ohhh... Greece... it's a beautiful country... best sea, best city... good idea to go there!

I've heard nothing but good about the region, but I have never been there. I have a lot of family there, almost none in the US---so it would be an interesting visit. I have never met any of my family, my father having left Greece in 1917. I thank you for the comments.

And In Washington? How is things?

We live outside a small community, in a county that is not very wealthy. People, in general, struggle here, but it's a nice place to live, especially if you are retired, which I am. We, too, are feeling the world problems, and are concerned for the future. Otherwise, life is good! Thanks for asking.

Harold

 

[alb320]

hi Harlod...
I can't send you a mail or a private message because forum give me an error of smtp.
I write here my public email: [email protected]
I have 5Mbit internet connection but size of mail max 5MB.

I have never been in US, but I would come there.

I'm very happy to talk with you.

 

[Harold_V]

I am now in contact with alb320 and have started sending pictures.

Harold