consolidation of Loss Gold thread

[4metals]

If I add sulfamic acid to Tumbler after the reaction was over, would it be a good time? Will we not need heat?

I believe you will get the temperature you need to use sulfamic acid to kill off the excess nitric if you add it in the tumbler when the last addition of nitric has gone to completion and the reaction is still hot enough. The question is if the reaction is hot enough to begin with. This is something you will have to physically measure.

Originally I was skeptical about adding sulfamic to the tumbler because it will be difficult to add from the holes you can open up on the end of the tumbler where the exhaust to the scrubber exits. But then I remembered the charging hole. I added a red arrow pointing to the charging hole on a photo Gold Refinery provided.
This hole is where scrap material is added to the tumbler and it is convenient because it is directly opposite the drain hole where the tumbler empties into the filter. If you stop the tumbler with this port on top, it can be opened and you can measure the temperature. If you have 80ºC or close, you can add sulfamic acid there.

Using the charging hole is good because it will allow you to carefully add the sulfamic and to monitor it closely so it doesn't foam too high.

Re-read the posts in this thread by Geo and Orvi about adding the sulfamic and add it carefully if it is at 80ºC or higher. do not over-add and look for the signs as described to determine when you have added enough.

Then you can add ice through the same hole and let the solution cool before filtering.

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.

This is not as simple as it sounds. It is nearly impossible to know how much of the nitric you added has actually reacted and how much remains in solution. However your working experience can show you the right quantity for subsequent reactions. The nitric (70%) weighs 1.4 grams per ml. You know how many milliliters of nitric you added. Weigh out the quantity of sulfamic acid you will need to neutralize 100% of the acid you used (this will be too much, but it will help you do this properly in the future). Add the sulfamic, paying attention to the way it reacts and stop when it is complete. The activity of the reaction of the sulfamic acid on the solution should provide enough mixing that you need not seal up and spin the tumbler for this part. Simply place the cover over the hole to provide stronger exhaust from the scrubbing duct.

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 amount and observe if there is some fizzing. If it still reacts, add more and repeat the waiting step.

When you are done, weigh the remaining sulfamic that you haven't used. Now you can calculate what percent of the calculated sulfamic acid you actually used. Do this for a few lots and soon you will have a working value for future use. I would be surprised if it is more than 25% of the calculation made for 100% of the acid added.

I realize your system has the capability to add peroxide. I have never used peroxide in this fashion and the 4:1 aqua regia quantities I gave you per ounce of material should provide sufficient oxidizer.

Gold Refiner, please inquire what the wetted parts of the dosing pump provided for peroxide additions are. If compatible, the pump could be used for a slow constant nitric feed which will give you a continuous controlled reaction which could control NOx generation and provide a more constant warming effect for the reaction.

 

[Gold.refinery]

Several misunderstandings seem to have happened.
Please look at the two photos I sent.
We have 4 holes on door in the top of the tumbler. The central hole is for Fumes to exit and connect to the condenser.
Two holes is covered with glass , to look at the reaction.
A hole to add urea or sulfamic acid or…. Also, in the second photo, it is clear that through the outlet pipe, there is a thin hose that is connected to the dosing pump.

After explaining this image, I have to point out that we do not Fill scrap through the valve into the Tumbler,
we open the door on top of the Tumbler and fill the scrap in the Tumblr .
We can also use the hole you saw in the picture to measure the temperature of the solution with laser thermometer. Also to add sulfamic acid.
The valve you mentioned with red arrow ,
we open for the final washing of Tumbler.

 

[4metals]

The reason I suggested the charging port (as some manufacturers refer to it) as the place to add and monitor the sulfamic additions is because it is lower than the exhausted end and the fumes are drawn towards the exhaust. Opening a port on the high end will allow fumes to escape more easily. The second reason is the charging port is closer to the solution level and any slight rise from the rate you are adding chemistry will be easier to notice. As far as the chemistry goes, it is the same on each end.

One thing I have learned from a lifetime of refining is that there are two types of refiners. Refiners who have experienced a run away reaction with loss of values, and those that lie and deny it. If you refine enough it will happen. One general rule of refining is to leave at least 50% of your vessel to accommodate a rise due to chemical additions. If your tumbler reactor is operating at design capacity (25kg) or close, you will not have that 50% for a rise. The reaction will rise and it will produce aerosols of gold containing acid which will rise above the exhaust airflow and be sucked into the condenser circuit.

In the case of your equipment, if the temperature rise of the reaction gives you the heat to use sulfamic acid, you can CAREFULLY add the sulfamic and closely monitor your additions as the reaction rises. That is the only benefit of adding sulfamic to the tumbler reactor. Urea will work on a cold solution so I would never add it to the tumbler because it bubbles excessively and will cause aerosol losses. This I am sure has happened to you because in the photo you just sent, is an employee with a full scoop of urea just waiting to be poured into the funnel. That is a lot of urea to drop in at once, especially in a reaction vessel where you cannot have a 50% capacity for the reaction to rise.
This is precisely why you should add chemicals based on the reaction and not off a scripted sheet saying add X.

The safest option for you will undoubtedly be adding Sulfur Dioxide gas to both de-NOx the solution and drop the gold.

While you still have urea and sodium metabisulfite you can use the urea in the precipitating tank to de-NOx the solution. (sparingly based on reaction and certainly not in large scoops) followed by additions of sodium metabisulfite while mixing the solution until the gold is dropped. And then mix the dropped gold to be sure you have dropped the gold from the solution hiding under the gold precipitate.

 

[Gold.refinery]

Excellent ,Points was very effective and useful. Thanks 4metal

Opening a port on the high end will allow fumes to escape more easily. The second reason is the charging port is closer to the solution level and any slight rise from the rate you are adding chemistry will be easier to notice

I agreed to add sulfamic acid to Tumblr from the bottom valve, because I saw the reaction up close. Question: Is it better to open the door to exit the fumes or is it closed? I think it is open. Right?

If your tumbler reactor is operating at design capacity (25kg) or close, you will not have that 50% for a rise. The reaction will rise and it will produce aerosols of gold containing acid which will rise above the exhaust airflow and be sucked into the condenser circuit.

There are dimensions of Tumblr:
Diameter :63 cm , Length : 100cm

you should add chemicals based on the reaction and not off a scripted sheet saying add X.

I am convinced that seeing the reaction is more important than the values on paper, especially documenting the values in different reactions will be useful to find Amounts.

While you still have urea and sodium metabisulfite you can use the urea in the precipitating tank to de-NOx the solution. (sparingly based on reaction and certainly not in large scoops) followed by additions of sodium metabisulfite while mixing the solution until the gold is dropped. And then mix the dropped gold to be sure you have dropped the gold from the solution hiding under the gold precipitate.

I will follow up to launch SO2 because it both precipitates gold and de-noxx the solution.

But before that , I will use SMB, urea. Also sulfamic acid.
I'm looking to test scrubbers when I use SMB. I will also check the small size of the exhaust above the gold tank in the next operation.

 

[Gold.refinery]

I have a few days to summarize the problems of Refining machine for a serious follow-up from the manufacturer.
So far we have reached the stage of gold precipitate .
I noticed problems in the parts

1) I noticed there is a BIG problem with the filters. There is not enough vacuum space between the floor and the paper or fabric filter, nor is the grid suitable.

2)I noticed that the chimney outlet of the gold tank is weak.

3)I realized that the gold tank needs a mixer, not a hand mixer.
I realized that the gold tank should have a heating system.

Of course, we have not study scrubbers, waste treatment system and filter press untill now.
I hope in the end I can summarize the problems of all parts to follow the manufacturer.

 

[Geo]

The reaction between sulfamic acid and nitric acid is only violent when the solution is at or near 94°C. The reaction will happen at a lower temp with a much more subdued reaction but the process takes more time. If your reaction vessel is set at a certain volume and there is no room for a more violent reaction, you may have to work with the sulfamic acid to discover the correct temperature and amount to add at one time. 4metals gave you the best process by measuring your sulfamic acid against the nitric acid used. The factors that might change would be temp, amount added at one time and time needed to complete the process.

 

[silver1]

Is that a fresh water filter or what is that i have circled?

 

[4metals]

Ralph, I believe that is the canister filter that Gold Refinery showed the stannous test on its contents. It's purpose is to catch any silver chlorides that escape the filter labeled Silver Chloride filter. They are difficult to rinse free so in addition to catching silver chlorides it retained a little gold chloride too!

 

[4metals]

Of course, we have not study scrubbers, waste treatment system and filter press until now.

Please provide photos of your fume scrubber, your waste treatment system and your filter press.
There are a few technical specifications we need to know about the fume scrubber to evaluate it properly. We need to know the air flow rate through the scrubber, probably expressed in cubic meters per hour. Then we need to know the cross sectional area of the packed section of the scrubber. The packed section is the area that contains the tower packing where the chemical reactions take place. To effectively scrub NOx fumes they have to remain in the "scrubbing zone" inside the scrubber for about 8 seconds. If we know the actual area of the packing and the flow rate we can see if the scrubber has the necessary retention time for effective scrubbing of NOx. Finally, is there a pH controller and dosing pump to maintain the pH of the scrubber liquid?

I assume you are treating your waste with a process known as classic destruct. This involves adding caustic liquid to the acid waste until the metals. in solution are converted over to. metal hydroxides, these are filtered from the solution in your filter press. The use of urea, and the subsequent smell of ammonia you sensed tends to re-dissolve some of the copper and cause treatment problems, that's one reason why staying away from urea is preferred

 

[silver1]

Has he posted any inside pictures of the AgCl filter funnel yet or did i miss them? He is using seperate funnels for the gold powder vs AgCl isn't he?

Yeah i don't like them canister filters exactly for that reason.

 

[4metals]

He is using seperate funnels for the gold powder vs AgCl isn't he?

One would hope he had one for each but he has not been specific. There's only one thing worse than a filter that doesn't suck well...... that's two filters that don't suck well!

 

[Gold.refinery]

Is that a fresh water filter or what is that i have circled?

 

[Gold.refinery]

One would hope he had one for each but he has not been specific. There's only one thing worse than a filter that doesn't suck well...... that's two filters that don't suck well!

Yes, we have three filters but with the problems mentioned. For silver chloride, for gold, for sludge from the mother solution after the precipitation below the secondary tank.

 

[silver1]

Yes, we have three filters but with the problems mentioned. For silver chloride, for gold, for sludge from the mother solution after the precipitation below the secondary tank.

Dam!

 

[Gold.refinery]

is there a pH controller and dosing pump to maintain the pH of the scrubber liquid?

Yes,We have a dosing pump that regulates the pH of the water inside the scrubber. Of course, for the first pair of scrubbers, the second pair of scrubbers do not have pH control with the dosing pump.

In the tank of the first pair of scrubbers, ammonia is added to control the pH of 7. In the tank of the second pair of scrubbers, there is a caustic soda.

The white smoke I mentioned earlier comes out of the chimney (at the peak of the reaction), after the addition of ammonia. The smell of chlorine gives very little.

The electric motor has an inverter to regulate the air flow.

 

[Gold.refinery]

I assume you are treating your waste with a process known as classic destruct. This involves adding caustic liquid to the acid waste until the metals. in solution are converted over to. metal hydroxides

Our classic filtration system has 4 stations with the method of adding caustic soda according to the image.
The first station has a motor mixing with the blade. In the first station we add AL.

The second station has pipe with air injection.

The third station has a motor mixer with a dosing pump to add caustic soda.

The fourth station is for final maintenance and control only.

 

[Gold.refinery]

Finally, the liquid goes by a diaphragm pump to press the filter.

 

[4metals]

This thread is getting long and I think it best if I break it off into separate threads, one for fume scrubbing, and one for waste treatment.

Seeing as it is Memorial Day weekend here in America, my Big Green Egg and a pork roast is beckoning louder than the forum, I will try to split these threads off this weekend and start replies in earnest after the long weekend.

From this point onward it will be best to concentrate on the chemistry of getting your gold as pure as possible in this thread. Gold Refinery, we are still waiting on details of your flocculant. From what you told us we know it is used in baby diapers but maybe a bit more info?

 

[silver1]

Sodium polyacrylate ?

 

[silver1]

https://www.intechopen.com/chapters/70081