Canadian Mining Journal


PERSPECTIVE: Going forward or back?

One the news releases that landed in my inbox last week made me wonder about the advancement of mineral proces...

One the news releases that landed in my inbox last week made me wonder about the advancement of mineral processing technology. Is it going forward … or back?

The item in question came from a Canadian company testing a South American property for its zinc potential. The company and project shall remain nameless. What caught my eye was that the favourable results were obtained in a kiln. That made me wonder why hydrometallurgical methods were not being tested.

Anytime an ore is subjected to heating it gives off gases. The worst case scenario is the burning of sulphide ores and resulting clouds of SO2 and NOx responsible for widespread environmental damage. Such was the case in the early days of smelting nickel and copper ores from the mines near Sudbury, ON.

Fortunately today we have gas containment units, acid plants and various means of controlling particulate and other emissions. These technologies help protect the environment, but they come with certain costs and limitations.

Hydrometallurgical means of metal recovery does not produce such deleterious emissions. Methods have been adapted in recent history to leach almost every kind of ore imaginable and to create the purest metals. Hydrometallurgy is considered far cleaner than roasting ores.

Leaching comes with its own set of startup and operating costs, but the byproducts are frequently solids that are more easily managed than gaseous emissions.

That is what made me wonder: Is this South American project going backwards on the technology continuum? Why not test and consider modern leaching methods?

From where I sit, choosing a mineral processing technology (roasting) that would harm even a small corner of South America is a non-starter. When a better environmental option is at hand (hydrometallurgy), should not it be tested, too? Somewhere along the line the operator would have to do his sums on both options and balance them against environmental risk. It might be determined that roasting is the most cost-effective option. But if the company doesn’t test leaching, how can it make an informed decision?

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4 Comments » for PERSPECTIVE: Going forward or back?
  1. John Pursel says:

    Marilyn the ones that own this property are most likely clueless. The ones that did this test got paid to do what the likely clueless ones told them to do.

  2. Alex Doll says:

    Sulphur is fuel. A pyrometallurgical process creates heat energy which can be converted to electrical energy. In contrast, hydrometallurgical processes generally consume energy which is wasteful in a location that is short of electrical generating capability.

    Also keep in mind that coal is the largest source of electrical energy in the world. Substituting pyromet for hydromet means substituting burning coal for burning sulphide minerals.

  3. Mike Dry says:

    It might not be all that dumb. They may have been testing the first step (after concentration) in the RLE (roast-leach-electrowin) technology. Putting it very simplistically, the ore, assuming it to be sphalerite (ZnS) would be roasted in air to zinc oxide (ZnO) and sulphur dioxide (SO2). The sulphur dioxide would go to an acid plant to be converted to concentrated sulphuric acid and energy in the form of steam that could be used for heating or to generate electricity, depending on the specifics of that case. The concentrated acid would be a valuable by-product, unless the plant is too remote for easy shipping of acid to customers. Modern acid plants capture essentially all the sulphur, so pollution is not an issue as long as the acid plant is designed and operated correctly. The zinc oxide would be leached in sulphuric acid, the resulting solution of zinc sulphate would be purified and then zinc metal would be recovered by electrowinning, which also regenerates the sulphuric acid used to leach the zinc oxide. Overall, if there is a secure market for the concentrated sulphuric acid, the tried-and-tested RLE technology may well be a great way to go. It’s only the roaster and the acid plant step that’re not hydrometallurgy…

  4. Dj Corovic says:

    Let’s assume the author of this article is an investment advisor. Than this would be another example how uninformed opinions, guesses or general way of thinking may take as into wrong directions. How many money advisors are doing similar guess work and improvised way of thinking? How scary would be to have our money under their control?
    And as mentioned before technology selection depends on ore types.

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