SUDDEN INCREASE IN COPPER LEVELS

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vjodhani

Active member
Joined
Nov 14, 2018
Messages
39
We are using Bottom Blown Oxygen converter (4 ton) to convert 95% pure silver to 99.5% silver. This silver is casted into anodes for electrolysis process.Before casting when we send a sample to the lab copper is around 3000 ppm.After casting anodes when the sample is sent again by drilling the anodes the copper again shoots up-to 5500-6000 ppm.Why this phenomenon is happening?
Further I want to reduce copper ppm to <2000, so what can be added to remove copper selectively from the melt or what are the alternatives without incurring heavy investments?
 

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Both copper and lead increases from the melt to after casting. Since we can't change one element into another element there has to be some other process behind the results. I would suspect how samples are taken, the melt or the anodes might not be homogeneous. When a melt solidifies crystals are formed and contaminants are pushed out to the grain boundaries. Slow cooling would make that effect more pronounced.
Try to take a couple of samples on different places of an anode, as well as from the first and last anode in a batch. If the melt isn't homogeneous then the values between different anodes from the same batch will vary.
If the effect is from the cooling of the anode then different points of the same anode would get different values. Highest values of contaminants should be in the part that solidifies last.

There is another way lead and copper might increase after the melt, and that is if there are any carbon sources that might reduce some copper and lead oxides back to metal. for example you might use a gas burner to heat while pouring the anodes.

Göran
 
snoman701 said:
Are you adding the lead?

How are you sampling the pre-melt?


Sent from my iPhone using Tapatalk

Yes lead addition is there.
We are making a button cooling it and then sampling it.
 
g_axelsson said:
Both copper and lead increases from the melt to after casting. Since we can't change one element into another element there has to be some other process behind the results. I would suspect how samples are taken, the melt or the anodes might not be homogeneous. When a melt solidifies crystals are formed and contaminants are pushed out to the grain boundaries. Slow cooling would make that effect more pronounced.
Try to take a couple of samples on different places of an anode, as well as from the first and last anode in a batch. If the melt isn't homogeneous then the values between different anodes from the same batch will vary.
If the effect is from the cooling of the anode then different points of the same anode would get different values. Highest values of contaminants should be in the part that solidifies last.

There is another way lead and copper might increase after the melt, and that is if there are any carbon sources that might reduce some copper and lead oxides back to metal. for example you might use a gas burner to heat while pouring the anodes.

Göran
Yes we use high speed diesel for combustion.
You are right about the first and last sample of anodes. But why are we getting high copper after casting from the initial anodes also.The sample is sent from the top layer of the melt.Both the sample button and anodes are cooled with water after casting.Also we purge nitrogen for better homogeneity of the melt.
 
The copper didn't just appear. The copper was already there at the beginning or it wouldn't be there at the end. When smelting, There are different types of flux. Oxidizing flux and reducing flux. Oxidizing flux will dissolve base metal which is absorbed into the borax and a reducing flux reduces base metal which reports in the final metal casting. If you can't remove the copper before melting, try to use an oxidizing flux but be sure to use enough borax to absorb all the base metal.
 
Geo said:
The copper didn't just appear. The copper was already there at the beginning or it wouldn't be there at the end. When smelting, There are different types of flux. Oxidizing flux and reducing flux. Oxidizing flux will dissolve base metal which is absorbed into the borax and a reducing flux reduces base metal which reports in the final metal casting. If you can't remove the copper before melting, try to use an oxidizing flux but be sure to use enough borax to absorb all the base metal.

How to calculate the amount of borax needed to absorb the copper? (By mass balance?)
U mean to add anhydrous borax, right?
Also there is more soluble copper at high temperatures,the data shown above are of solid samples where copper levels are effectively high due to precipitation of copper with falling temperature?
Have you used borax before in your operations? Does it effect the purity of anodes?
Why do you warn of "try to use an oxidising flux but be sure to use enough borax to absorb all the base metal"?
 
I am not the best person to ask about smelting. Think of the borax as a solution which it is at high temperatures. How much copper are you dealing with? How much liquid solution would be needed to hold that amount of copper? It will not be accurate by no means but find out how much anhydrous borax will it take to fill a container that is 2000ml's by volume while melted. That should hold a half kg of copper. The flux will also need an oxidizer so add sodium nitrate to the melt to oxidize the copper. Avoid flux components such as sodium carbonate as it is a reducer. A true smelter will have to give you a better answer.
 
Geo said:
The copper didn't just appear. The copper was already there at the beginning or it wouldn't be there at the end. When smelting, There are different types of flux. Oxidizing flux and reducing flux. Oxidizing flux will dissolve base metal which is absorbed into the borax and a reducing flux reduces base metal which reports in the final metal casting. If you can't remove the copper before melting, try to use an oxidizing flux but be sure to use enough borax to absorb all the base metal.

vjodhani - I recieved this PM from you last week

Hi kurtak
got you reference from Geo it will be great if you could help me out with this.
viewtopic.php?f=49&t=27534#p290586
I have reached a almost dead end to it.
I am myself a metallurgist and I have seen a lot of precipitation in steels and aluminium but such thing is highly unlikely.Geo says you are very professional in smelting of precious metals.I hope if you could share you knowledge in that thread so that it will help other smelters also.Please share you views.
Regards,
vjodhani

I am not sure I am the one that can help with your problem as my smelting experience is (I believe) different then the process you are dealing with - my experience in smelting is recovering of PMs (Precious Metals) from low grade concentrates (like ore - or in my case electronic components that have been incinerated) where in a collector metal is used to collect the PMs & a "flux" is used to slag off the impurities --- that said - there are other members more experienced then I am - so maybe this post can kick off a more complete discussion to solving your problem

Geo - thanks for the reference to my smelting experience but (again - I believe) - per the underlined in your above quote - we are talking about two different process here

In the smelting we generally discuss here - we use chemical fluxes - such as borax, soda ash, silica, etc.to slag off unwanted elements from the concentrates of processing electronic scrap - which is a lot like smelting the concentrates of ore --- in this smelting process we are primarily slagging off the organics in the concentrate - but as well are able to slag of "certain" metal oxides that for the most part already exist as oxides - while at the same time using a collector metal (such as copper or silver) to collect the PMs in our concentrates & "to some" degree we can control oxidation &/or reduction with variations of our "chemical" fluxes - in other words - with different chemical fluxes we can oxidize (or keep them oxidized) some of the less noble metals & slag them off while at the same time keeping more noble metals such as copper or silver) in there reduction state for a collecter - which results in a dore metal that can then be further refined (copper or silver cell)

on the other hand - vjodhani is trying to "upgrade" - in a smelting process - an already existing dore metal (primarily silver) to produce a better grade anode for his silver cell

Because vjodhani is starting out with dore metal (silver "alloyed" with other metals) normal smelting with chemical fluxes doesn't work --- at best - "some" base metals "may" oxidize at the "surface" of the melt which "may" slag off "some" oxides - but you wont make a notable upgrade in the melt because the (chem) flux is only going to slag off the oxides at the surface of the melt while the majority of the melt remains nothing more then a molten alloy of metals

Hence the use of the BBOC (Bottom Blown Oxygen converter)

:arrow: https://en.wikipedia.org/wiki/Bottom-blown_oxygen_converter

The BBOC works by injecting blown oxygen at the "bottom" of the melt & as the oxygen passes up through the molten dore metal thereby allowing the less noble (base) metal to oxidize - the base metal oxides are then supposed to float to the surface of the melt producing a metal oxide slag (or dross) which is then taken off the top of the melt resulting in an upgrade of the starting dore


This - I think - explains the difference between smelting concentrates with chemical fluxes in order to get a dore metal & that of smelting with the BBOC to up grade the dore


But that doesn't explain the question vjodhani is asking & that may be that I don't fully understand the question - so -----

vjodhani - Metal going into the BBOC is (+/-) 95% Ag

After smelting operation in BBOC is run - metal is tested & test shows (about) 99.6% Ag


But when anodes are cast - & tested again - test shows (about) 99.3% Ag


so a difference of (about) .3% between BBOC test & cast anode test


Several questions

How is the BBOC metal test (sample) taken - (you said; - We are making a button cooling it and then sampling it.)

is the button made by taking a pin tube sample - then re-melting to make a button for testing - or are you dipping a sample from the top of the melt & pouring to a cone mold to get the button - or pouring a sample off the top off the melt & then producing a button from that sample pour - or ???


You said ; - You are right about the first and last sample of anodes.

Are the anodes being poured/cast directly from the BBOC & if so - what is the difference between first & last pour &/or those between first & last

You said; - But why are we getting high copper after casting from the initial anodes also

I don't understand this - what's the difference between "initial anodes" - and "after casting - are you saying you make a pour from the BBOC (like into ingots) & then re-melting the ingots to cast anodes

hopefully other more experienced members will chime in here

Kurt
 
vjodhani

I am not in a place, nor will I be for 2 weeks, to combine your posts on this issue. You are asking questions about one issue and doing it in several places. Please stick to one thread and you will get the most results. Your questions are good and the expertise exists here to help you but you do not help your case by starting new threads which all emanate from the same issue.

If another moderator doesn't do it first I will merge the topics about your problem when I am back home in front of a computer.
 
4metals said:
vjodhani

I am not in a place, nor will I be for 2 weeks, to combine your posts on this issue. You are asking questions about one issue and doing it in several places. Please stick to one thread and you will get the most results. Your questions are good and the expertise exists here to help you but you do not help your case by starting new threads which all emanate from the same issue.

If another moderator doesn't do it first I will merge the topics about your problem when I am back home in front of a computer.

8) 8) 8) AWESOME - I for see another thread worthy of the library coming :mrgreen:

Personally - I am looking forward to following this one :G :!:

Two weeks is only going to seem like a long wait - but WELL worth it in the end :p

Kurt
 
Copper is one of the most problematic metals to remove by cupellation with lead. It requires a lot of lead (about 20g Pb for each 1g Cu present) to remove the copper completely. Loss of silver is another problem caused by copper. Nickel in the presence of Cu makes the matter even worse.

Everything is written in this book:
 

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kurtak said:
Geo said:
The copper didn't just appear. The copper was already there at the beginning or it wouldn't be there at the end. When smelting, There are different types of flux. Oxidizing flux and reducing flux. Oxidizing flux will dissolve base metal which is absorbed into the borax and a reducing flux reduces base metal which reports in the final metal casting. If you can't remove the copper before melting, try to use an oxidizing flux but be sure to use enough borax to absorb all the base metal.

vjodhani - I recieved this PM from you last week

Hi kurtak
got you reference from Geo it will be great if you could help me out with this.
viewtopic.php?f=49&t=27534#p290586
I have reached a almost dead end to it.
I am myself a metallurgist and I have seen a lot of precipitation in steels and aluminium but such thing is highly unlikely.Geo says you are very professional in smelting of precious metals.I hope if you could share you knowledge in that thread so that it will help other smelters also.Please share you views.
Regards,
vjodhani

I am not sure I am the one that can help with your problem as my smelting experience is (I believe) different then the process you are dealing with - my experience in smelting is recovering of PMs (Precious Metals) from low grade concentrates (like ore - or in my case electronic components that have been incinerated) where in a collector metal is used to collect the PMs & a "flux" is used to slag off the impurities --- that said - there are other members more experienced then I am - so maybe this post can kick off a more complete discussion to solving your problem

Geo - thanks for the reference to my smelting experience but (again - I believe) - per the underlined in your above quote - we are talking about two different process here

In the smelting we generally discuss here - we use chemical fluxes - such as borax, soda ash, silica, etc.to slag off unwanted elements from the concentrates of processing electronic scrap - which is a lot like smelting the concentrates of ore --- in this smelting process we are primarily slagging off the organics in the concentrate - but as well are able to slag of "certain" metal oxides that for the most part already exist as oxides - while at the same time using a collector metal (such as copper or silver) to collect the PMs in our concentrates & "to some" degree we can control oxidation &/or reduction with variations of our "chemical" fluxes - in other words - with different chemical fluxes we can oxidize (or keep them oxidized) some of the less noble metals & slag them off while at the same time keeping more noble metals such as copper or silver) in there reduction state for a collecter - which results in a dore metal that can then be further refined (copper or silver cell)

on the other hand - vjodhani is trying to "upgrade" - in a smelting process - an already existing dore metal (primarily silver) to produce a better grade anode for his silver cell

Because vjodhani is starting out with dore metal (silver "alloyed" with other metals) normal smelting with chemical fluxes doesn't work --- at best - "some" base metals "may" oxidize at the "surface" of the melt which "may" slag off "some" oxides - but you wont make a notable upgrade in the melt because the (chem) flux is only going to slag off the oxides at the surface of the melt while the majority of the melt remains nothing more then a molten alloy of metals

Hence the use of the BBOC (Bottom Blown Oxygen converter)

:arrow: https://en.wikipedia.org/wiki/Bottom-blown_oxygen_converter

The BBOC works by injecting blown oxygen at the "bottom" of the melt & as the oxygen passes up through the molten dore metal thereby allowing the less noble (base) metal to oxidize - the base metal oxides are then supposed to float to the surface of the melt producing a metal oxide slag (or dross) which is then taken off the top of the melt resulting in an upgrade of the starting dore


This - I think - explains the difference between smelting concentrates with chemical fluxes in order to get a dore metal & that of smelting with the BBOC to up grade the dore


But that doesn't explain the question vjodhani is asking & that may be that I don't fully understand the question - so -----

vjodhani - Metal going into the BBOC is (+/-) 95% Ag

After smelting operation in BBOC is run - metal is tested & test shows (about) 99.6% Ag


But when anodes are cast - & tested again - test shows (about) 99.3% Ag


so a difference of (about) .3% between BBOC test & cast anode test


Several questions

How is the BBOC metal test (sample) taken - (you said; - We are making a button cooling it and then sampling it.)

is the button made by taking a pin tube sample - then re-melting to make a button for testing - or are you dipping a sample from the top of the melt & pouring to a cone mold to get the button - or pouring a sample off the top off the melt & then producing a button from that sample pour - or ???


You said ; - You are right about the first and last sample of anodes.

Are the anodes being poured/cast directly from the BBOC & if so - what is the difference between first & last pour &/or those between first & last

You said; - But why are we getting high copper after casting from the initial anodes also

I don't understand this - what's the difference between "initial anodes" - and "after casting - are you saying you make a pour from the BBOC (like into ingots) & then re-melting the ingots to cast anodes

hopefully other more experienced members will chime in here

Kurt

Thank you kurtak.

All your inferences from the thread were correct.Coming to your questions.

How is the BBOC metal test (sample) taken - (you said; - We are making a button cooling it and then sampling it.)

is the button made by taking a pin tube sample - then re-melting to make a button for testing - or are you dipping a sample from the top of the melt & pouring to a cone mold to get the button - or pouring a sample off the top off the melt & then producing a button from that sample pour - or ???

No the button is not prepared by pin tube. We are dipping a small mould of the size of button (250 grams),from the top of the melt.After room temperature is attained; analysis is done using ICP.

You said ; - You are right about the first and last sample of anodes.

Are the anodes being poured/cast directly from the BBOC & if so - what is the difference between first & last pour &/or those between first & last

We are casting anodes of approximately 4 tons; that is around 300 anodes.
Now suppose the first anode which is casted have copper levels lower than those casted after 250th anode (assume).
Summarising the above statement is that copper levels in the anodes casted initially have lower copper levels than the later.
You said; - But why are we getting high copper after casting from the initial anodes also

I don't understand this - what's the difference between "initial anodes" - and "after casting - are you saying you make a pour from the BBOC (like into ingots) & then re-melting the ingots to cast anodes
No we are directly casting anodes from the BBOC.
e.g., Sample analysis of melt before casting-3000 ppm Cu
Sample analysis of the first anode casted- 6000 ppm Cu (initial anodes)
Sample analysis of the last anode casted- 6500 ppm Cu.
So now I hope it clears your confusion.
 
4metals said:
vjodhani

I am not in a place, nor will I be for 2 weeks, to combine your posts on this issue. You are asking questions about one issue and doing it in several places. Please stick to one thread and you will get the most results. Your questions are good and the expertise exists here to help you but you do not help your case by starting new threads which all emanate from the same issue.

If another moderator doesn't do it first I will merge the topics about your problem when I am back home in front of a computer.

Nothing can be better than this :D
I was new I did not knew about this,so I put them accordingly :cry: ..
Now onward will stick to one thread.
4metals you are saying that all these problem emanate from the same issue; if this is true I can't just wait for your return. :D
Yes please merge all posts altogether for better clarity.
 
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