Pulverised coal firing in furnaces: Which advantage best explains why finely pulverised coal improves furnace operation and fuel economy?

Introduction / Context:
Pulverised coal (PC) firing grinds coal to fine particles and conveys it with primary air into the burner. The very high surface area accelerates devolatilisation and char burnout, enabling compact, efficient furnaces with good load response and fuel flexibility.

Given Data / Assumptions:

• Coal is milled to fine powder and injected with air.
• Proper burner design ensures good mixing and flame stability.
• Appropriate slagging/ash handling is implemented.

Concept / Approach:
Fine particles heat rapidly and react quickly, raising flame temperature locally and improving thermal efficiency. The improved burnout accommodates a broader range of coals (including higher-ash) while careful staging and temperature control can also handle lower ash-fusion temperatures by limiting local hot spots and maintaining suitable slag viscosity.

Step-by-Step Solution:

Verification / Alternative check:
Heat balance comparisons show reduced excess air requirement and lower loss-on-ignition in fly ash for PC systems versus stoker firing.

Why Other Options Are Wrong:

Common Pitfalls:
Assuming any coal can be burned without considering slagging/fouling limits and burner aerodynamics; PC systems still require proper selection and tuning.

Final Answer:
all (a), (b) and (c).