How do pulverized coal firing and stokers differ in fuel handling and combustion characteristics?

• A. Pulverized coal uses fine-ground coal carried by air for rapid, high-efficiency combustion; stokers burn larger coal on a grate with slower, simpler combustion.
• B. Pulverized coal burns larger chunks; stokers use fine coal with air.
• C. Pulverized coal requires no air; stokers require air.
• D. Both operate identically.

Answer: (A)

Pulverized coal firing uses coal ground into a fine powder that is carried by air and blown into the furnace as a suspended fuel. The tiny particles have a very large surface area, so they ignite quickly and burn rapidly when mixed with combustion air. This gives a high heat release rate, fast startup or load changes, and overall high combustion efficiency, provided the fuel-air mix and airflow are well controlled. Handling this fuel requires a pulverizer, precise air supply, and dust and ash management systems, but it enables tight control over combustion and flame temperature.

In contrast, stokers burn larger chunks of coal that sit on a grate. The combustion happens on the grate surface with air flowing through the bed and up through the fuel, so the burn is slower and more gradual. The fuel handling is simpler—no fine grinding or pneumatic transport—and the system is robust to varying coal sizes. However, the slower, contained burn typically means lower efficiency and slower response to load changes compared with pulverized coal firing.

So, pulverized coal is carried by air as a fine powder for rapid, high-efficiency combustion, while stokers burn larger coal on a grate with slower, simpler combustion.