Pulverized coal is

Question

Pulverized coal is

Examoogle · Accepted Answer

Coal broken into fine particles

Explanation: 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.

Working Principle: 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.

Key Formulas: $SA = \frac{6}{d}$ — Relationship where Surface Area (SA) is inversely proportional to particle diameter (d), justifying higher combustion rates for smaller particles.

Key Points: 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.

Advantages: Improved combustion efficiency due to large surface area; Rapid response to load fluctuations; Capability to use lower-grade coal; Reduced excess air requirement

Disadvantages: High power consumption for the grinding mill; High maintenance cost due to erosion from abrasive coal particles; Requires complex dust collection and handling systems

Applications: Utility scale Thermal Power Plants; Industrial boilers for steam generation; Cement manufacturing kilns

Additional Info: 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.

Answer: 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.

Exam Tip: 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.

Related Questions

Discussion (0)