Question

Identify the INCORRECT statement(s)

• A. Calcination is typically exothermic and roasting is usually endothermic.
• B. Coking of coal is carried out in a shaft furnace.
• C. The aims of extractive metallurgy processing are separation, compound formation, metal production, and metal purification.
  (D) The secondary steelmaking offers steel cleanliness, composition adjustments, and temperature adjustments.
• D. The secondary steelmaking offers steel cleanliness, composition adjustments, and temperature adjustments.

Hint:

Remember the basic thermal nature of common pyro-processes: - {Roasting (Oxidation)} \(⇒\) Generally Exothermic (releases heat). - {Calcination (Decomposition)} \(⇒\) Generally Endothermic (requires heat). Also, associate processes with furnace types: coking with coke ovens, ironmaking with blast furnaces (a type of shaft furnace).

Answer 1

The Correct Option is A, B

Step 1: Understanding the Concept:
This question asks to identify statements about metallurgical processes that are factually incorrect. This requires a broad knowledge of different stages and equipment in extractive metallurgy.
Step 2: Detailed Analysis of Each Statement:
- (A) Calcination is typically exothermic and roasting is usually endothermic.
- Calcination is the thermal decomposition of an ore, usually a carbonate or hydroxide, to drive off CO\(_2\) or H\(_2\)O (e.g., \( \text{CaCO}_3 ⇒ \text{CaO} + \text{CO}_2 \)). Breaking chemical bonds requires energy, so these decomposition reactions are typically endothermic (they require heat input).
- Roasting is the heating of an ore (usually a sulfide) in the presence of air to convert it to an oxide (e.g., \( 2\text{ZnS} + 3\text{O}_2 ⇒ 2\text{ZnO} + 2\text{SO}_2 \)). These oxidation reactions are generally highly exothermic (they release heat).
- The statement claims the opposite (calcination is exothermic, roasting is endothermic). Therefore, statement (A) is INCORRECT.
- (B) Coking of coal is carried out in a shaft furnace.
- Coking is the process of heating coal to high temperatures (\(>1000^\circ\)C) in the absence of air to drive off volatile components, producing coke. This process is carried out in specially designed ovens called coke ovens, which are a type of recovery or non-recovery horizontal chamber furnace, not a shaft furnace. A shaft furnace (like a blast furnace) is a vertical furnace where materials move downwards against an upward flow of gas. Therefore, statement (B) is INCORRECT.
- (C) The aims of extractive metallurgy processing are separation, compound formation, metal production, and metal purification.
- This statement accurately summarizes the overall goals of extractive metallurgy.
- Separation: Concentrating the valuable mineral from the gangue (beneficiation). - Compound formation: Converting the mineral to a more suitable compound for reduction (e.g., roasting sulfide to oxide).
- Metal production: Reducing the compound to produce the metal (smelting).
- Metal purification: Refining the crude metal to remove impurities. - Therefore, statement (C) is CORRECT.
- (D) The secondary steelmaking offers steel cleanliness, composition adjustments, and temperature adjustments.
- Secondary steelmaking (or ladle metallurgy) refers to processes performed on the liquid steel after it leaves the primary furnace (like BOF or EAF) and before casting. Its main purposes are exactly as listed: removing impurities like sulfur and dissolved gases (cleanliness), adding alloying elements to achieve the precise target chemistry (composition adjustment), and fine-tuning the steel's temperature for casting (temperature adjustment). Therefore, statement (D) is CORRECT.
Step 3: Final Answer:
The question asks for the incorrect statements. Based on the analysis, statements (A) and (B) are incorrect.