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Examoogle • User • info@examoogle.com • EE-2024-8821
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Pulverized coal is
Coal free from ash
Non-smoking coal
Coal which burns for long time
Coal broken into fine particles
Coal broken into fine particles
Pulverized coal is raw coal that has been mechanically ground or crushed into a very fine powder, typically to the consistency of talcum powder. This pulverization process significantly increases the surface area of the fuel, which enhances its combustion efficiency.
Pulverized coal is raw coal that has been mechanically ground or crushed into a very fine powder, typically to the consistency of talcum powder. This pulverization process significantly increases the surface area of the fuel, which enhances its combustion efficiency.
SA=d6 — Relationship where Surface Area (SA) is inversely proportional to particle diameter (d), justifying higher combustion rates for smaller particles.
The coal is fed into a pulverizing mill (like a ball mill or bowl mill) where mechanical grinding reduces it to a particle size where approximately 70% passes through a 74-micron sieve. This fine powder is then mixed with preheated primary air and injected into the boiler furnace as a turbulent jet, where it burns almost instantaneously in suspension, similar to a gaseous fuel.
Pulverization allows coal to be burnt in suspension within the boiler furnace.
Higher surface-to-volume ratio results in rapid ignition and stable flames.
Allows for precise control of combustion by adjusting fuel-to-air ratio.
Essential for modern large-scale utility thermal power plants.
Improved combustion efficiency due to large surface area
Rapid response to load fluctuations
Capability to use lower-grade coal
Reduced excess air requirement
High power consumption for the grinding mill
High maintenance cost due to erosion from abrasive coal particles
Requires complex dust collection and handling systems
Utility scale Thermal Power Plants
Industrial boilers for steam generation
Cement manufacturing kilns
Standard fineness: 70-80% through a 200 mesh (74 micron) sieve.
Option A is incorrect as coal contains ash content that remains after combustion.
Option B is incorrect; pulverized coal still produces smoke depending on combustion control.
Option C refers to the burn rate, but the specific term 'pulverized' refers to the physical state of the material, not the duration of combustion.
D is correct — Pulverized coal refers to coal that is ground into a very fine, dust-like powder to maximize its surface area for rapid and efficient combustion.
In exams, always distinguish between 'pulverized' (physical size) and 'grade' (chemical quality). Pulverization is a mechanical process for efficiency, not a refining process for purity.