consolidation of Loss Gold thread

[orvi]

I would just add that reaction of sulfamic acid with nitric acid starts around 75-80 °C, but it is wise to heat it past this temperature to speed up the process. Timed additions are necessary to see if the nitric/NOCl/nitrous acid are still present.

Easily said for Gold.refinery:

Generally, you add sulfamic acid similarly as urea - heat the solution to at least 80 °C, add sulfamic SLOWLY until it stop fizzing (not to foam over), then you wait at least 15 minutes - or better 30 minutes and add little ammount and observe if there is some fizzing. If it still reacts, add more and repeat the waiting step.

Be aware of the fact, that fizzing liquid in open beakers or reactors create aerosols, which carry your gold solution away. Best is to prevent this by using larger container, so liquid is well below the top of the vessel and popping bubbles cannot shoot the liquid out of the vessel

I know so2 creates the best gold Sediment.
Is the smell of sulfur created by so2 gas Sedimentation more or by SMB?

Now, We have food grade SMB available.
If we want to use SMB to deposit gold in the next operation, what points should we follow?

For example, what is the ratio of adding smb to gold? (Helps for less gas and less pollution of gold dust).

Do we have to dissolve it with water and add it or can it be added solid?

In terms of time, how long does smb deposition take (compared to hydrazine)?

Both reagents (SO2 and SMB) smell like SO2, because SO2 is formed from SMB when reacting with acid in solution. SO2 gas coulld be very well regulated and bubbled from the cylinder - very very convenient. You can set up, open the valve and happily observe how the solution is losing the yellow colour while gold settle to the bottom And you will see with stannous how much gold you have in solution - so you adjust the next addition of gas.

Also, there is another advantage of using SO2 gas over metabisulfite. With sodium metabisulfite, you consume one equivalent of HCl to generate active SO2 gas - which actually reduce your gold.
SO2 is already an acidic gas - so it does not deplete your acid.

If the acid is depleated (concentration/strength goes down), impurities like silver chloride or copper (I) chloride become less soluble and drop together with gold.

That is why SO2 gas produce cleanest precipitate of gold. As established refinery, I would suggest to invest and purchase SO2 gas cylinder. It can be regulated very well, do not add contaminants, easily added to the solution via tube...

We need some photos or details about your scrubber - if it can scrubb the NOx gasses, I think it will scrubb also SO2 gas. Or there can be added simple NaOH bubbler at the end of your system - which catch like 90% of SO2 in first pass. And that would be enough to reduce the smell.

 

[nickvc]

The Sulfur Dioxide fume is much more water soluble than a NOx fume and European standard fume scrubbing usually can accommodate Sulfur Dioxide, it's NOx where there is a retention time issue, which we can discuss later.
Another option for dropping the gold is Sulfur Dioxide gas cylinders. It can drive off the excess Nitric by dropping gold and allowing the nitric to burn off by re-dissolving gold until the gold drops and stays dropped because the nitric is gone. And gaseous Sulfur Dioxide drops gold very clean.

A last option which has very low odor is Vitamin C or Ascorbic Acid. I know some smaller scale refiners using it and maybe someone with first hand experience with it will chime in here.

4metals I have used ascorbic over many years but have tended to use ferrous for the majority of the drop and finished with ascorbic to limit the amount of iron in the precipitate , again I fed ferrous directly into the pregnant solution so long as it was bright green and I did drops of 2-3 kilos regularly with little problem.

 

[Gold.refinery]

Important:

Brainstorming is great, different suggestions will also be helpful.
But we need to know that we want to implement these solutions for a large-scale refinery.
We should not reinvent the wheel.

Here different members offer their suggestions, but a refiner will definitely come up with a solution that they can repeat every day.
With maximum efficiency and minimum pollution.
Refining is a very dirty job, and its fees are very low. (But in large volumes).
So our suggestions must be Accurate.

I stopped refining operations to summarize the results of the topics in the forum.

 

[Gold.refinery]

I asked several times about the ratio of chemicals used in the reactions, but only suggestions were made on how to calculate the acids, for the other of the chemicals did not provide ratios: precipitator (SMB,So2,Hyd,FeSo4,Ascorbic) , diluent water , Urea, Sulfamic Acid, NaOH,…

A table in Excel can specify the entire ratio of values.

 

[Yggdrasil]

I asked several times about the ratio of chemicals used in the reactions, but only suggestions were made on how to calculate the acids, for the other of the chemicals did not provide ratios: precipitator (SMB,So2,Hyd,FeSo4,Ascorbic) , diluent water , Urea, Sulfamic Acid, NaOH,…

A table in Excel can specify the entire ratio of values.

One of the issues here is that for
most if us, no batch is identical.
So we depend upon a general idea,
but have to differentiate each reaction on what we observe and can
measure (Stannous).

For SMB it is simple,
if you have a Nitric free,
relative acidic and clean Gold solution, you need 1:1 by weight.

But that is paper values that are not much worth in the real world of precipitating Gold from various
solutions,
each one needs individual attention,
it’s own TLC to perform the best.

We are not avoiding the questions,
but they do not have an answer
set in stone.
Stochiometric calculations can be done easily enough, but it will not take you all the way home.

 

[Gold.refinery]

I know everyone has their own solution.
And this is achieved after various experiences.

Since an inexperienced operator works first with skepticism, knowing the approximate values will be helpful.
By approaching the values, it can detect more confidently.
Of course, I know that after a while, these numbers will only remain on paper.

Guys, please provide stoichiometric calculations of all chemical.

 

[Yggdrasil]

I’m not sure what your main language are, but you did not understand what I tried to tell you.
I’ll try this way:
No two batches are identical.
Most approach this by adding what they expect is needed, and adjust as necessary.
Almost always more are needed.
There are adaptations of course,
like with the Nitric as you have picked up already. If time is of little concern the AR process or any other Nitric process can be completed lower than stochiometric.

But you surely have an chemist at hand to do your calculations?

Are you able to read or balance chemical reactions?

 

[Yggdrasil]

I know everyone has their own solution.
And this is achieved after various experiences.

Since an inexperienced operator works first with skepticism, knowing the approximate values will be helpful.
By approaching the values, it can detect more confidently.
Of course, I know that after a while, these numbers will only remain on paper.

Guys, please provide stoichiometric calculations of all chemical.

It’s hard to give any answer to this:
The processes you have outlined so far is AR for dissolving,
Hydrazine for dropping
(should be swapped to SMB)

For AR the most chemically effective method is with all HCl and half or so Nitric to start with, then batch wise addition until completed, with heating and a reflux condenser.
Since this is outside your specs, you can do the same without heating and overshoot the Nitric.
For completing the reaction in short time, you will have to overshoot quite a bit and as such no parts can be calculated other than the initial estimation.
For Sulfamic Acid the same goes, since it is completely dependent on how much you overshot the Nitric.

If you go through these two steps, with proper filtering so you end up with a completely clear Nitric free and highly acidic solution, the SMB to Gold Ratio is 1 to 1 in weight. 1 gram SMB gives 1 gram Gold.
Most will overshoot the SMB quite a bit to make sure all the gold drop.

So you see it is not possible to answer your question with X parts this and Y parts that will give Z parts this.
The rest of the alphabet mingles in.

 

[4metals]

No two batches are identical.
Most approach this by adding what they expect is needed, and adjust as necessary.
Almost always more are needed.
There are adaptations of course,
like with the Nitric as you have picked up already. If time is of little concern the AR process or any other Nitric process can be completed lower than stochiometric.

Very true and cannot be overstated.

How would you calculate an exact amount of Sulfur Dioxide gas to add? Can you tell us the depth of solution you will gas into, or the bubble size the sintered glass frit provides? Or the temperature of the solution. These factors effect the quantity of gas used, as does the gold concentration. It is not as easy as looking at a balanced equation and saying add X and you’re done.

Gold Refiner, since your last flurry of insistence for specifics I have heard by PM from members frustrated with your attitude. And you have again started PMing me to ask questions off forum.

Let me make this clear, I will no longer be answering questions on this topic by PM and it is my hope neither will others. All questions should be on the open forum. That is what forums are about, helping each other. And you seem to want a one way street.

If your inquiries when you purchased your refining system matched the degree of your questioning here maybe you wouldn’t be having these issues. You are being given good advice here and it will result in solving your issues to the point where they will meet your goals. Something the manufacturer either didn’t give you, or you were unwilling to pay for.

As you may sense, I’m a bit irritated this morning. As another member often reminds us, it’s time for more coffee.

 

[Shark]

Thank you 4metals for trying to keep this on the forum. This discussion has been a real glimpse into the professional side of refining and a real eye opener for us small refiners.

 

[4metals]

To get back on track here we should ask if it is feasible for Gold Refinery to get bottles of Sulfur Dioxide gas.
I have used sulfamic acid extensively but as Geo mentioned it has always been in heated Phaudler reactors. I think for this application perhaps a hybrid application is in order.
The precipitating tank Gold Refinery is using is not heated and that will be an issue. I would be trying gaseous Sulfur Dioxide and allowing the reaction to heat up as the Sulfur Dioxide reacts. When it gets warm and is still blowing red fumes, powdered sulfamic acid can be added to assist in the consumption of the free nitric. This scenario is desirable because the rate of NOx coming off the reaction is directly proportional to the Sulfur Dioxide addition rate. So simply throttling back on the feed will give Gold Refinery control if there are scrubbing issues.
Even if sulfamic acid is not added the Sulfur Dioxide will drop the gold completely and eliminate the free nitric.
Gold Refinery has mentioned using a flocculant. I would like to hear more about what is used and the logic behind it.

 

[Gold.refinery]

Sorry about that, I should have shared these topics before buying machines from the manufacturer. Too late unfortunately .

Our Tumbler can not heated , The gold precipitation tank also can not be heated.
So we do not have an easy way to use sulfamic acid. To run the hybrid way mentioned by 4metal, operator has a difficult Mission , we have to use So2 gas to raise the temperature.
( more gas and more smell)

Then adding sulfamic acid in those conditions will not be easy for the operator.We have to try this way once, with or without sulfamic acid.

Tomorrow I can ask about so2 gas supply,
But I have SMB available now.

with this condition
(I'm worried about the smell of SO2 gas, the workshop is located in a busy business district)

 

[silver1]

Shit! I didn't offer my wisdom just for the hell of it! So in other words education is not the question being ask or sought here, but just give me the answers i'm looking for. Again, this is an art! Yeah my time is more valuable to me than that! If answers and not knowledge, they are different, is all you seek then try the search function. It's all here! I understand frustration, but unless you fix the problem that lead to that frustration this is going to be a viscous circle. Your problem doesn't exist in just one area here, it's exist in all areas. From the equipment your using, to the advice you were given before you got here, all the way down to the inexperience your staff has.

Give a man a fish and he eats for a day. Teach a man to fish and he eats everyday!

 

[Geo]

As for the sulfamic acid, to answer your question, sulfamic acid destroys nitric acid on a one to one ratio by weight. One gram of sulfamic acid will destroy one gram of nitric acid in solution. As apposed to urea, which does not actually destroy the nitric acid. It binds with nitric acid creating urea nitrate. The operative word being nitrate. Under certain circumstances, the urea nitrate can be broken down and the nitrate will release the stored nitric acid back into solution. I understand that the equipment was not designed to be heated to those temps but perhaps modifications can be made? Perhaps the manufacturer may have an adaptation that can be used.

 

[Gold.refinery]

I know urea at the end of the wastewater treatment process, reacts with caustic soda to form ammonia. What problem does this cause?

What are the other benefits of using sulfamic acid over urea?

Given that we can not heat the tank, what
problems will occur if I do not use sulfamic acid?

 

[Gold.refinery]

Gold Refinery has mentioned using a flocculant. I would like to hear more about what is used and the logic behind it.

We use a flocculat to stick very small particles together. I can ask exactly the chemical of it.

The manufacturer gave us it, I remember saying that the absorbent powder used in diapers .

 

[4metals]

As Orvi pointed out the Sulfur Dioxide is easily handled by your scrubber

Nox is much difficult to scrubb or destroy. SO2 is acidic, so very simple "basic" absorber with NaOH is usually enough to catch vast majority to acceptable levels.

for this reason I will assume your existing scrubber will handle the Sulfur Dioxide generated either from adding powdered sodium metabisulfite or adding gaseous Sulfur Dioxide. The usual "problem" with fume scrubbers and refining is from NOx, which you have said your scrubber handles well.

Most refineries I work with have exhaust stacks which extend above the roofline and the fumes released are above their neighbors noses. If you have a stack on a low roof and are a few meters from a neighbors window and at the same level, that's a different story.

That being said you should add the sodium metabisulfite slowly with good agitation. You are agitating by bubbling air, we discussed this before and you know you will have to keep the solution moving.

Seeing you have a 2" (10cm) exhaust on your precipitation tank, I think your fear of Sulfur Dioxide fume should be from what escapes out the top of the vessel and not out the stack. All the more reason for slow additions.

 

[Gold.refinery]

I will assume your existing scrubber will handle the Sulfur Dioxide generated either from adding powdered sodium metabisulfite or adding gaseous Sulfur Dioxide

It will be determined after discussing the scrubber.

If you have a stack on a low roof and are a few meters from a neighbors window and at the same level, that's a different story.

Unfortunately, the height of the chimney is not high.

That being said you should add the sodium metabisulfite slowly with good agitation. You are agitating by bubbling air, we discussed this before and you know you will have to keep the solution moving.

Is adding solid SMB different from dissolving in water?
The gold tank does not have a mixer, if we want to mix the liquid well manually, is that enough?
how long does it take?
(I think once we have to try with a small volume and observe)

Seeing you have a 2" (10cm) exhaust on your precipitation tank, I think your fear of Sulfur Dioxide fume should be from what escapes out the top of the vessel and not out the stack. All the more reason for slow additions.

I am waiting for a list of problems with the machine components (Problem with vacuum filters, tank heater, Tank exhaust , scrubber, and other possibilities) to follow up with the manufacturer.

 

[Gold.refinery]

I have used sulfamic acid extensively but as Geo mentioned it has always been in heated Phaudler reactors. I think for this application perhaps a hybrid application is in order.

If I add sulfamic acid to Tumbler after the reaction was over, would it be a good time? Will we not need heat?
After this, add ice or water and filter the silver chloride.

 

[Yggdrasil]

If I add sulfamic acid to Tumbler after the reaction was over, would it be a good time? Will we not need heat?
After this, add ice or water and filter the silver chloride.

Yes you will need heat.
It need to be around 80C for the Sulfamic to react.
Sometimes I wonder if you read your
answers at all??
It is clearly stated in your answers.

If you use either a SO2 tank or a SO2 generator, you can adjust and tinker so
it won’t give off much at all.
(All SO2 is used before reaching the surface)
If you choose this route, there may not be much use of Sulfamic at all.

I’d recommend you to do some small tests for your self and maybe your staff, with a few grams just to get acquainted with the processes discussed.