The M44 Test Run & Process Details

[Shark]

Thank Lou,

Quite often while reading I had wondered just where the limit was in "plain English". I have never been close to running 6 pounds of pins at one time, especially in nitric, but it is nice to know the limits in the terms you have used to describe it here.

 

[Geo]

Thank Lou,

Quite often while reading I had wondered just where the limit was in "plain English". I have never been close to running 6 pounds of pins at one time, especially in nitric, but it is nice to know the limits in the terms you have used to describe it here.

How are you doing Jeff? I hope you are feeling better.

 

[Shark]

Thank Lou,

Quite often while reading I had wondered just where the limit was in "plain English". I have never been close to running 6 pounds of pins at one time, especially in nitric, but it is nice to know the limits in the terms you have used to describe it here.

How are you doing Jeff? I hope you are feeling better.

Been better, Geo, but then I have been a lot worse. Short update, it is still debatable if I will ever be able speak right again. If I talk more than short conversation's it feels like something stabbing me in the throat.

 

[4metals]

I recently have discovered that in some states, Ohio for example, that 10 pounds per day de minimis status exists. Other states, like Indiana for example, it is an annual limit. So in theory you can run it all out in 1 day and still be under the limit of 1 ton of NOx. Still in any state, if you p*ss off the neighbors you can be forced to use a scrubber. And strict lot logs and chemical usage logs are required to document consumption.

But in most states you cannot simply stay under the limit and skate free. If you are audited you must provide the study done by a licensed PE in your state to show that your reasonably calculated PTE (Potential to Emit) is under the limit either daily or annually. A PTE can be calculated as all your equipment can produce (emission) in 24 hours 7 days a week. It is up to the generator to prove by lot logs and chemical purchases that even though your PTE can exceed the limit, the actual emission, based on work load and chemical usage, is less.

Even if you have a scrubber this still applies, but a fine tuned scrubber lowers the NOx emission by 99%.

 

[modtheworld44]

You know, I see a lot of mention here about just using nitric acid on pins.

While nitric often works fine (especially so with Au/Cu systems where tin is not present) and provides pretty much the best accountability, it is not at all acceptable NOR LEGAL IN THE UNITED STATES to just dump 50 lbs of pins in a drum and 20 gallons of nitric acid and let 'er rip.

Bear in mind that the federal limit for NOx, which are a hazardous air pollutant (HAP) is 10 lbs/day. Below that, it's considered a source so minor it is de minimis and therefore not regulated (though stipulations apply--namely that you better have your records together if you claim this). Also, different municipalities have different rules. The federal rules serve as the minimum guide.

So, copper dissolves in nitric acid in one of two ways--a pathway that makes NO which ultimately ends up as NO2 and one that just makes straight NO2:

3 Cu (s) + 8 HNO3 (aq) = 3 Cu(NO3)2 + 2 NO (g) + 4H2O (1)
1 Cu (s) + 4 HNO3 (aq) = 1 Cu(NO3)2 + 2 NO2 (g) + 2 H2O (2)

Reaction 1 occurs in dilute systems, typically below 3.9 M HNO3 (so called reagent, or azeotropic nitric acid is ~15.7-16 M).
Anyway, what does this mean? It means for every pound of copper digested (454 g/lb) / (63.55 g/mol Cu) X 2 mol NOx = 14.3 mol NOx per lb. As it ultimately ends up as NO2, that's how the emission factor should be calculated.
NO2 is 46.01 g/mol so 1.45 lbs of NOx per lb of copper dissolved.

That said, please don't dissolve more than 6.5 lbs of copper/day unless you have a permit to install and operate a fume scrubber or want to risk a fine and/or possible criminal sanctions!

Lou

Is that for the use of 68% nitric or 50/50 split of 68%? Can you do that calculation vs the 16% sodium nitrate I use so I can see if there is an emissions difference, Please Sir.Thanks for your input so far on this process.



modtheworld44

 

[kurtak]

As Kurt said it is labor intensive the way they are documinting it to be done. They can eliminate some of that by doing their calculations on how much sodium nitrate they will need to dissolve the base metals and put in 90% of what is needed on the front end. Then they can let the solution run and have a set time frame on when they need to go look at the solution between additions of HCL, and having a set amount of HCL to add each time. They will need to be careful on the additions of HCL because the gold that cements out and settles can cause a boil over when they add their HCL, especially with the heat turned up so high on their solutions.

First off I want to thank you all for your question - good questions are being asked - but right now I do not have time to answer them all - yesterday we got our first snow fall & though it melted away by end of day it is a clear sign that winter is on the way - the next forecast for bad weather is 3 days (which could be rain - or - snow) so I have things I must absolutely get done to get ready for winter in this next 3 days so just don't have time for posting much right now --- however will answer 2 questions now

First is - yes of course stannous testing was done --- it is always done on all solutions involving gold or PGMs that have been dissolved &/or have the "potential" to dissolve gold or PGMs - that is just standard operating procedure --- just as using the stock pot treatment is standard procedure before sending solutions to waste treatment --- the stannous test was negative - the filtered solution still goes to stock pot with copper added & given time for settling

Barren - per the underlined above - based on my observation when running the test I don't "think" (meaning I could be wrong) that will work - I will post in detail my observations & why I "think" that ASAP - but first I "must" get some things done before the next snow flies

I did run the M44 one more time & I will post those results as well as soon as I get caught up on what I need to do before the snow flies

Kurt