Volatile matter in coal – combustion behavior A coal with a high percentage of volatile matter will most likely:

Introduction / Context:
Volatile matter (VM) is the fraction released as gases and vapors when coal is heated in the absence of air. VM strongly influences ignition characteristics, flame length, smoke formation, and coking behavior. Understanding VM helps in boiler design and selection of suitable combustion systems.

Given Data / Assumptions:

• High-VM coal contains a larger fraction of hydrocarbons and oxygenated volatiles.
• Combustion system aims for complete burnout with minimal smoke.
• Carbonisation behavior is also affected by VM (more tar/gas).

Concept / Approach:
High VM lowers ignition temperature and increases the release of combustible gases early in heating, producing long flames that can be smoky if air–fuel mixing is inadequate. Such coals typically need larger, not smaller, combustion space to complete afterburning of volatiles and reduce smoke. During carbonisation, high-VM coals generate more tar and gas, not less.

Step-by-Step Solution:

Verification / Alternative check:
Boiler and kiln practice confirms that high-VM bituminous coals need sufficient secondary air and residence time to oxidize volatiles fully.

Why Other Options Are Wrong:

• Smaller combustion chamber: Opposite of typical design guidance for high VM.
• Very little tar/gas on carbonisation: High VM yields more tar and gas.
• All of the above: Contains incorrect statements, so cannot be right.

Common Pitfalls:
Assuming high VM always means cleaner combustion; without proper air staging, smoke and CO can increase.

Final Answer:
ignite easily and burn with a long, smoky flame