Coal briquetting binders: Which of the following is NOT commonly used as a binder in coal briquetting operations?

Introduction / Context:
Coal briquetting agglomerates fine coal into usable blocks. Binders provide cohesion during pressing and strength after curing. Knowing typical binders aids in selecting recipes that balance strength, cost, and combustion behavior.

Given Data / Assumptions:

• Focus on common industrial binders for coal fines.
• Options include organic tars/pitches and alternative additives.
• Single best answer expected.

Concept / Approach:
Classic binders include coal tar, pitch (bituminous binders), and molasses (often with lime as a hardener but not as the primary binder). Lime is primarily a flux/desulfurizer or hardening additive rather than the main binding medium; it lacks the viscoelastic properties of tars/pitches that provide strong green and cured strength.

Step-by-Step Solution:
Identify principal binders: tar and pitch are standard.Molasses can serve as a carbohydrate-based binder (often combined with lime or cement).Lime (CaO) itself is not typically the binder; it is used to modify chemistry/strength but not as the main cohesive agent.Therefore, the item not used as a binder, in the primary sense, is lime.

Verification / Alternative check:
Industrial manuals list tar and pitch as dominant binders; molasses–lime systems classify molasses as the actual binder with lime acting as a hardener/activator.

Why Other Options Are Wrong:
Tar and pitch are standard petroleum-derived binders; molasses is a recognized alternative binder.

Common Pitfalls:

• Confusing hardeners/fluxes (lime, cement) with true binders.
• Assuming any additive that improves strength qualifies as the binder.

Final Answer:
Lime (CaO)