Coal preparation practice: the washability of coal, used to predict how effectively ash and impurities can be removed at different cut densities, is routinely determined using which separation test?

Introduction / Context:
Washability curves guide dense medium cyclone and bath operations by showing the yield–ash relationship achievable at various specific gravities. Accurate characterization is essential for plant design and economic optimization.

Given Data / Assumptions:

• Coal is sized prior to testing.
• Liquids of known specific gravities are prepared.
• Test determines mass fractions floating or sinking at each density.

Concept / Approach:
Heavy media float–sink tests are the standard method. By stepwise immersion, the proportion of floats and sinks is measured, and ash content of each fraction is analyzed to construct washability curves and ideal separation results.

Step-by-Step Solution:
Identify the technique that separates based on relative density (specific gravity).Recognize float–sink (heavy media) as the canonical washability test.

Verification / Alternative check:
Coal preparation standards and text references designate float–sink analysis as the benchmark for washability assessment.

Why Other Options Are Wrong:
Tabling: thin-film gravity concentration influenced by size and shape, not used for washability profiling.Elutriation: hydraulic classification by size/settling velocity, not a density-only cut test.

Common Pitfalls:
Using process yields directly in place of washability curves; plant yields include inefficiencies, while washability curves represent the ideal potential at a given cut density.

Final Answer:
Heavy media (float–sink) separation