Question

Recovery of zinc from its ore is about 0.4pt percent.

• A. 96 -- 98
• B. 74 -- 76
• C. 60 -- 62
• D. 38 -- 40

Hint:

In metallurgy questions, always distinguish between plant/process efficiency and overall recovery from the ore in the ground. Overall recovery is always lower due to cumulative losses in mining and ore concentration stages.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
The term "recovery" in extractive metallurgy refers to the percentage of the valuable metal present in the ore that is successfully extracted and converted into a final product. This is a crucial metric for the economic viability of a mining and processing operation. Recovery is calculated at various stages: mining, beneficiation (ore dressing), and smelting/refining. The overall recovery is the product of the recoveries at each stage.

Step 2: Detailed Explanation:
The question asks for the overall recovery of zinc from its ore. This is a combination of efficiencies from multiple steps.

• Smelting/Refining Recovery: Modern hydrometallurgical (Roast-Leach-Electrowin) and pyrometallurgical (Imperial Smelting Furnace) processes for zinc are highly efficient, with recovery rates in the plant itself typically being very high, often in the range of 95-98%.

• Overall Recovery: However, the question refers to recovery "from its ore," which implies the entire chain from the mine. Significant losses can occur during mining (not all ore is extracted) and especially during beneficiation (concentrating the ore), where some zinc mineral is lost to the tailings.
Let's consider a hypothetical scenario for a low-grade or complex ore:

• Mining Recovery: 80% (20% of ore left in the ground)

• Beneficiation Recovery: 65% (35% of zinc mineral lost to tailings)

• Smelting Recovery: 95% (5% lost in process)
The overall recovery would be the product of these efficiencies: \[ \text{Overall Recovery} = 0.80 \times 0.65 \times 0.95 = 0.494 \quad \text{or} \quad 49.4\% \] For ores that are particularly difficult to process (e.g., very fine-grained, or containing interfering elements), the beneficiation recovery can be even lower. If the beneficiation recovery dropped to 50%, the overall recovery would be \(0.80 \times 0.50 \times 0.95 = 0.38\) or 38%. Thus, while a recovery of 38-40% is very low and represents an economically challenging operation, it is a plausible figure for the overall recovery from certain types of difficult-to-treat ores, accounting for all losses from the mine to the final metal.

Step 3: Final Answer:
Considering the cumulative losses across mining, beneficiation, and smelting stages for a complex or low-grade ore, an overall recovery in the range of 38-40% is possible, even though the final metallurgical process itself is much more efficient.