Pyrometallurgy: Roasting, Smelting, Refining & Electrowinning

Pyrometallurgy: Roasting, Smelting, Refining & Electrowinning 2017-03-23T09:55:18+00:00
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Carbon Life Cycle (14 replies)

Tarun Karakoti
1 year ago
Tarun Karakoti 1 year ago

I need some data for approximate carbon losses as fines after regeneration of carbon (every cycle) and after new carbon attrition.

Marshal Meru
1 year ago
Marshal Meru 1 year ago

Carbon losses depend on several factors including ore hardness and whether you are using pump-cells, and are higher in CIL than CIP due to faster agitation. That said loss is normally 20-60g carbon per tonne of ore treated.

You should also talk to your carbon supplier. Larger companies such as Jacobi (Goldsorb), have several carbon grades that suit different ore types and loading requirements. http://is.gd/HsNC8l

Fine carbon can be captured using flotation, but this is only cost effective when the losses are high, as large cells are required see ROWE, J. and MCKNIGHT, S. Characterization and recovery of gold associated with fine, activated carbon. World Gold Conference 2009, the Southern African Institute of Mining and Metallurgy, 2009.

There is a very dated paper by David Seymour of Newmont presented at Randol 1992 on typical carbon losses at 26 major mines that looks at carbon management and factors like regeneration temperature and inductors or pumps.

Suggest you start by asking your current carbon supplier and competitors what data they have.

Bob Mathias
1 year ago
Bob Mathias 1 year ago

My experience is in the order of 60-80 grams carbon per ton, as it points out there are many factors that contribute, agreed that the Kilns may be the source of higher losses due to abrasion, heat ranges/ashing/oxidation, cracking in quenching, carbon inventory concentration, attrition due to grind, interstage transferring, screen aperture losses etc.

Sturmbann
1 year ago
Sturmbann 1 year ago

I agree with your 20-60gpt. I used to budget 40gpt of total carbon losses per tonne of ore treated and that is based on historical data in operating plants of around 850k -1.0M tpa.

Tarun Karakoti
1 year ago
Tarun Karakoti 1 year ago

Around 60 grams losses of carbon can be thought at CIL&CIP operation as I understand. But what about a CIC operation! I assume it should be lower as we only treat solution with carbon after heap leach operation.

Subhash-Kumar-Roy
1 year ago

In CIC operation, carbon losses are 10-12 grams per 1 ton ore. This is the standard for everywhere and you can decrease carbon losses from higher levels to 10-12 grams. Maybe carbon shapes effect to these losses. You can search cubic carbons which can be less affected by flows and pumping or etc, but at that time you can be thinking about gold adsorption and recoveries. Maybe those can be affected badly, less carbon adsorption low production. Piping systems, carbon transfer pipelines and other mechanical factors effect to this losses. Firstly, this mechanic abrasion effects should be decrease.

Marshal Dienes
1 year ago
Marshal Dienes 1 year ago

I suggest carbon consumption depends as much on the type of carbon (supplier?) as well as operational factors and practices. From my experience at large scale gold plant operations, I have seen about 25 g/t consumption. This was true for both conventional CIL/CIP (both agitated tank and Pachuca - air agitated) and pump cell operations. When we went from conventional CIP type operation we did not see increase in carbon consumption, maintaining the same carbon supplier. As for the CIC (treating heap leach solutions), we saw about 10 g/t. Again at the CIC plant we operated, we were able to reduce carbon consumption significantly when we switched from mechanical pumps to air-lift pumps. Using correct type of carbon advance pump (true recessed impeller pumps preferred) will be beneficial to carbon consumption. Another important factor to consider is the type of carbon regeneration kiln and how the regeneration is carried out. Recovering carbon fines at the back end of the plant are usually done cheaply by using screens, spirals and / or water only cyclones. This way you do not need to contaminate the carbon with flotation reagents; especially if the clean carbon is coarse and good enough quality to be used at the plant (getting rid of flotation reagents requires higher temperatures in the kiln).

John Koenig
1 year ago
John Koenig 1 year ago

What type of carbon are you using? I have found on an operation that extruded carbon are very unpredictable whereby for extended periods your consumption is very low and then increase for a period due to losses, the reason being that batches are added and all carbon is uniform in size thus your "breakdown" is almost uniform thus they all reach minimum size at virtually the same time that increase your consumption tremendously over this period until your inventory has been restored.

Unterstarm
1 year ago
Unterstarm 1 year ago

My experience is that transferring carbon with WEMCO Hydrostal pumps and 4d elbows significantly reduced carbon losses in CIC. In regeneration, the key thing is to control the ingress of air into the kiln. When a particle of carbon burns it makes the carbon near it more friable making it more susceptible to breakage in the operation. Capture of fine carbon is easily accomplished with a filter press.

Dizzy Flores
1 year ago
Dizzy Flores 1 year ago

Attrition of carbon is the sum of attrition in each stage of the circuit; as pointed out above. The variables are ore type, carbon transfer method (airlift or pump), frequency of regeneration, regeneration temperature, size of carbon screens in the tanks, hardness of carbon, carbon management strategy (excellent point which many people overlook - add carbon regularly to avoid this), and a bunch of other variables.

In Australia, the attrition rate is typically in the range of 20-25g/t; as we have predominantly oxide ores which are not as abrasive as "hard" ores.

Look at your process and make improvements based on efficiency of intertank screens, Do pumps have the right impellors, do you have too many elbows? Too much oversize rock in your circuit! Your regeneration kiln (is it burning carbon?), are your trash screens holed? etc. Benchmark similar plants flowsheets, and try to do better than them.

Tarun Karakoti
1 year ago
Tarun Karakoti 1 year ago

That question was for one of project I am nowadays working on.
I have discussed with Weir about pumps. They have changed Hydrostal pumps at a mine (CIC operation) to Wemco recessed impeller pumps and thus they decrease the carbon lost. I assume those pumps are new trends for carbon transfer.

Helena Russell
1 year ago
Helena Russell 1 year ago

What are the experiences using hose pumps for carbon transfer and pumping? They use those for moving fish at fisheries to transfer to trucks, other raceways, etc. without harming fish (maybe confuses them for a time!). Can't see why not work for carbon and certainly little to no abrasion concerns.

Unterstarm
1 year ago
Unterstarm 1 year ago

In carbon transfer, the primary factors for carbon degeneration are pipeline fluid velocity, elbows (should be at least 3d if not 4d), pump. Neither recessed impeller nor hydrostal is good if heads are high and consequently pump rpm is high. My experience designing and starting near 30 plants is that velocity below 8 ft/sec and elbows with a radius of 4 times the diameter never caused me a problem with either recessed or screw type pumps. Pump rpm was maintained below 1350 rpm. Given the opportunity, the preferred design was to pre-atritt carbon in the kiln by adding dry carbon to the kiln feed. One of the problems with carbon floating in CIC is that even after 24 hours of attrition was that carbon was still not thoroughly wetted. Quenching at temperature thoroughly wetted the carbon.

Ace Levy
1 year ago
Ace Levy 1 year ago

My notes tell me that 25g/t is the industry norm. Higher consumption occurs when there are other factors at play (the wrong transfer pumps being the classic carbon killer). Lower consumption is certainly possible if you follow a carbon-gentle regime of carbon movement (but NEVER do that at the expense of gold losses of course).

The extruded carbon tends to be very regular in size distribution which gives the effect that speaks of. The carbon particles all abrade at the same rate and then bang! You have a large part of you inventory that becomes fine very quickly.

Oberstorm
1 year ago
Oberstorm 1 year ago

The manufacturer considers normal to lose up to 4% of carbon after each cycle. In the regeneration process are the main attrition.

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