Limitation to widespread pulverised-coal firing in boilers Which factor has historically been one of the most important deterrents to extended use of pulverised coal for boiler firing?

Introduction / Context:
Pulverised coal firing improves combustion efficiency and response, but it also creates large quantities of fine ash (fly ash) entrained in flue gas. Before the widespread adoption of effective particulate control, environmental and housekeeping concerns constrained the technology’s deployment in some settings.

Given Data / Assumptions:

• Historical and practical considerations for utility/industrial boilers.
• Focus on a major deterrent to extended use rather than a minor drawback.

Concept / Approach:
The key challenge is controlling and disposing of fine particulate matter. Without high-efficiency electrostatic precipitators, fabric filters, or multistage cyclones, pulverised firing leads to excessive fly-ash emissions, violating environmental limits and causing operational fouling. While ash disposal, power for conveying, and erosion are concerns, the stack emission issue has been pivotal for broad adoption and regulatory compliance.

Step-by-Step Solution:

Verification / Alternative check:
Regulatory thresholds for particulate emission directly restrict operation unless high-efficiency collectors are installed.

Why Other Options Are Wrong:

• Ash disposal problems: Important but manageable with ash-handling systems; less constraining than direct stack emissions.
• Higher power consumption: A cost penalty but rarely a showstopper.
• Erosion of I.D. fan blades: Engineering design mitigates this with materials and layout; not usually the primary deterrent.

Common Pitfalls:
Confusing on-site ash handling logistics with off-site air-quality compliance; the latter typically dictates technology feasibility.

Final Answer:
Excessive fly-ash discharge from the stack