Hydrometallurgy: Leaching in Heap, Vat, CIL, CIP, Merrill–Crowe, SX Solvent Extraction

Hydrometallurgy: Leaching in Heap, Vat, CIL, CIP, Merrill–Crowe, SX Solvent Extraction 2017-04-04T06:57:36+00:00
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Correlation between pulp density in to gold and silver recovery in CIP Cyanidation (13 replies and 1 comment)

Kumar Choudhry
1 year ago
Kumar Choudhry 1 year ago

Would you please help give information how is the correlation of density (%solid) to gold and silver recovery in gold Cyanidation (CIP) leach process. Is there any typical optimum value? And what is the explanation?

1 year ago
Obersturmbann 1 year ago

The rheology of each ore is different. The first thing that comes to mind is keeping carbon in suspension. Once you get below about 45% solids, carbon starts to settle in the CIP tanks, and can be difficult to re-suspend because of lime agglomeration.

We aim typically for 50-55% solids. Above this, viscosity starts to impact negatively on slurry flux through the interstage screens, and mixing efficiency.

9 months ago

aiming at 50-55% solids, would the dissolution be high. on the part 55% percent part, i thought carbon would float and the residence time increases

Kumar Choudhry
1 year ago
Kumar Choudhry 1 year ago

Thank you very much for the explanation, yes you are right, we are using quick lime for controlling the pH and fix motor speed agitator.

David Kano
1 year ago
David Kano 1 year ago

The rheological characteristics of any slurry and ore dependent! You can have ore containing swelling clays, exhibit thixotropic properties, or become viscous with increases in pH. There is, in fact, no real typical value and slurry densities can be 'ideal' anywhere from 30% solids to 65% solids.

The folks at Lakefield (SGS Lakefield Canada) have a working model for establishing optimum density for leaching. The model has been used on operating plants and does a good job of predicting optimal densities, carbon concentrations, etc.

Bill Rico
1 year ago
Bill Rico 1 year ago

General rule of thumb is the pulp density is approximately the same as the specific gravity of carbon. But the viscosity of the slurry can influence this.

Carmen Ibanz
1 year ago
Carmen Ibanz 1 year ago

Porosity of carbon is 0.8, fill this with water and add to the bulk density of carbon, 0.5, which gives you the density of carbon in the circuit of 1.3. Carbon is suspended by the pulp, mixing and viscosity. All the variables discussed above apply.

Kumar Choudhry
1 year ago
Kumar Choudhry 1 year ago

Correct me if I am wrong, initially Carbon density is lower than pulp because its pores are not fully loaded with gold and Silver yet, then by the time during the CIL process, the Au and Ag Cyanide will fill the Carbon pores hence the Carbon density will be increased and the possibility to settle down will be higher. On the other hand during the initial loading process our Carbon pores are only filled by water therefore their density will be lower than 1, then the Carbon will tend to float (?)

1 year ago
Standartenfurer 1 year ago

Preparation and removal of fines broken in transit fills the pores so carbon is added as a wet material not a dry one. As soon as they are wet SG goes to 1.3 (0.8water +0.5C in same volume space) addition of gold will take carbon into 1.4 range which is the density of 50% (w/w) solids slurry of an 2.8sg ore

Carmen Ibanz
1 year ago
Carmen Ibanz 1 year ago

One thing I did not mention is that with some scaling and some occluded dirt, the bulk density of carbon during use in CIL/CIP can rise to 0.65 from 0.5 (for fresh carbon).

Tony Verdeschi
1 year ago
Tony Verdeschi 1 year ago

Some of my good friends have already elaborated on the carbon aspect of the leach and I agree with what he states.
What you should not ignore is the cost of reagents and water which is also density related

Besides the threat of sinking carbon due to low densities, the cost of reagents like cyanide which is added into the slurry is also an issue is you save a lot of cyanide by running higher densities.

The recoveries also improve with higher densities as the residence time increases, higher slurry mass, lower volume displacement. Agitation is improved with higher densities, the carbon suspension which we touched on improves and that inhibits soluble losses

Inventory management improves, all density related start controlling the leach feed density and the process improves. But it all needs professional management systems in place to really see the returns, automate as much as possible (Ph. control, density control, cyanide control).

1 year ago
Gruppen 1 year ago

As usual you have got it spot on-the additional cyanide added and wasted due to low densities can also result in higher costs for cyanide destruction at the tail end of the circuit. The majority of spillages within the leach area including hosing of bund areas are returned back to the leach due to containing cyanide but often a proper process audit of dilution sources can leverage significant benefits for all the reasons earlier described.

Zander Barcalow
1 year ago
Zander Barcalow 1 year ago

Talking about the density of pulp cyanidation circuits, the pulp density is a control parameter that directly impacts the contact zones of the mineral. Residence time in the consumption of reagents and mainly in the process-ability. Lower density cyanide consumption is increased and the values are diluted and increasing draw process-ability required in the washing and extraction equipment and precipitation at higher densities no greater contact areas values in higher concentrations of the cyanide solutions and therefore washing equipment and precipitation are more efficient and less capacity. In addition to the solutions that must be treated for cyanide destruction plant lower costs and more than minimum capacity with less consumption of reagents are required. At low densities greater capabilities in thickening tanks requiring higher flocculants consumption directly impacts the extraction of values in the leaching tanks are required. The operation for gold and silver extraction work with 45 % solids as minimum!

Victor Bergman
1 year ago
Victor Bergman 1 year ago

Some interesting comments! As a few have commented reagent costs must be considered. This is why spending $1/t on a viscosity modifier to allow pulp density to be increased by 5% pays back just in cyanide savings, and delivers significant operational benefits, especially if it has scale dispersion properties, as your carbon will stay cleaner.

1 year ago

I agree with most of the comments above. It’s usually best to run the highest leach feed density that can be achieved without causing flow or agitation issues - this helps out with cyanide and lime consumption, and also allows the highest possible contact time between carbon and your pregnant solution, assisting in achieving good solution tail values.

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