Pyrometallurgy: Roasting, Smelting, Refining & Electrowinning

Pyrometallurgy: Roasting, Smelting, Refining & Electrowinning 2017-04-21T02:33:06+00:00
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Silver and the Merrill Crowe Process (6 replies and 1 comment)

Maya Rothman
2 years ago
Maya Rothman 2 years ago

I need to know the correct dosage addition of zinc (Kg Zn / ppm Ag) to have a better precipitation of silver?

John Koenig
2 years ago
John Koenig 2 years ago

Depends on a lot of factors such as pH, other minerals/metals present, and others. This is best done by lab testing. The real amount can be calculated, see this PDF.

Bill Fraser
2 years ago
Bill Fraser 2 years ago

Right, do the lab work then hope your production guys buy the same grade of zinc dust you used in the lab tests, and a truck accident doesn't contaminate your PLS pond!

Bill Fraser
2 years ago

Doing the lab work is important and it depends on pH, other minerals/metals present, deaeration and clarification of solution.

Victor Bergman
2 years ago
Victor Bergman 2 years ago

There is no general perfect of addition Zn except theoretical calculation, however to give useful advise, one need to know a few more parameters. I have several years experience running Merrill Crowe for both Au and Ag. Is your project a plant or a leach operation. Also ore grade is important.

Alan Carter
2 years ago
Alan Carter 2 years ago

Zinc addition rate depends on Ag grade, flow rate, and expected recovery. As long as your turbidity looks good and pulling enough vacuum from the de-aeration tower. Adjusting you Zn addition should be easy.

Bob Mathias
2 years ago
Bob Mathias 2 years ago

The "perfect" addition is stoichiometric value of the ratio of Ag+Au per Zn. I suggest you look at Marsden and House on gold metallurgy or Dorr & Bosqui excellent book on cyanidation for operation of a Merrill-Crowe plant. The rule of thumb is to filter to a clarity of gin and remove the oxygen to less than 0.5 ppm to optimize zinc consumption and precious metal precipitation.

Helena Russell
2 years ago
Helena Russell 2 years ago

Please, do not forget mercury , because is another element that precipitates with zinc addition.
Another issue , higher grade Au and Ag lower ratio Zn / (Au + Ag). Keep in mind Pourbaix's diagram and that pH is very important.

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