Coal firing practice: Which factor(s) accentuate clinker formation on a furnace grate when burning coal?

Introduction / Context:
Clinkering is the formation of fused ash masses on the grate, which impedes air flow, reduces combustion efficiency, and complicates ash removal. Understanding which operating and fuel factors aggravate clinkering helps operators adjust conditions and select suitable coals to maintain reliable furnace performance.

Given Data / Assumptions:

• Ash chemistry (iron and sulphur compounds) can lower ash fusion temperature.
• Draft/airflow and fuel-bed temperature influence local melting of ash.
• Firebed thickness and preheated primary air affect heat release, bed temperature profile, and the propensity for slagging/sintering.

Concept / Approach:
Clinkering occurs when ash softens or melts, then sinters into hard masses. Conditions that increase bed temperature, create hot spots, or provide ash compositions with low deformation temperatures will intensify clinker formation. Managing air distribution, bed depth, and coal selection is central to mitigation.

Step-by-Step Solution:
Assess ash composition: high Fe/S-bearing minerals can form low-melting eutectics, promoting sintering (supports option a).Consider air and draft: insufficient or poorly distributed air (low forced draft) can cause uneven burning and localized overheating (option b).Evaluate bed configuration: thick beds and preheated primary air can elevate bed temperatures and extend high-temperature residence, increasing slagging risk (option c).Therefore, combined effects in (a), (b), and (c) accentuate clinkering → choose “All of the above”.

Verification / Alternative check:
Operational guidelines recommend moderating bed depth, balancing primary/secondary air, and selecting coals with suitable ash fusion characteristics to reduce clinker formation. These align with the analysis above.

Why Other Options Are Wrong:
Any single factor alone may not fully explain severe clinkering; the combination in (d) captures the broader practical reality.“Only high ash fusion temperature ash”: Higher fusion temperature actually reduces clinkering risk, contradicting the statement.

Common Pitfalls:
Focusing solely on ash chemistry while ignoring air management and bed depth; real furnaces require holistic control of fuel, air, and grate conditions.

Final Answer:
All of the above