Related Questions

Sphericity is the ratio of the surface area of a spherical particle having the same volume as the particle to the surface area of the particle. Which of the following has the maximum value of sphericity?
A Sphere
B Cube
C Cylinder (L/D = 1)
D Raschig rings
Combustion of pulverised coal as compared to that of lump coal
A Develops a non-luminous flame
B Develops a low temperature flame
C Can be done with less excess air
D Provides a lower rate of heat release
Combustion of pulverised coal compared to the lumpy coal
A Provides better control of furnace temperature
B Facilitates combustion with lower excess air
C Provides higher thermal efficiency & flame temperature
D All of the above
Limestone powder is injected during pulverised coal burning in boilers to __________ the flue gases.
A Reduce SO2 content in
B Catalytically convert SO2 to SO3 in
C Increase the dew point of
D None of these
In case of pulverised coal fired steam boiler, the secondary air serves the main purpose of
A Transportation of coal
B Drying of coal
C Combustion of coal by supplying it around the burner
D Preheating the primary air
Which of the following is the most important deterrants to an extended use of pulverised coal in boiler firing?
A Ash disposal problem
B Excessive fly ash discharge from the stack
C Higher power consumption in its transportation
D Erosion of induced draft fan blades
The advantages of firing pulverised coal in the furnace lies in the fact that, it
A Permits the use of high ash content coal
B Permits the use of low fusion point ash coal
C Accelerates the burning rate and economises on fuel consumption
D All of the above
The excess air required for the combustion of pulverised coal is of the order of about __________ percent.
A 5
B 15
C 30
D 45
Coal is pulverised before burning in large capacity boiler furnaces mainly to
A Ensure its complete combustion
B Facilitate easy ash removal
C Enhance its calorific value
D Provide trouble free operation
The main function of primary air in pulverised coal fired burner is to
A Burn CO to CO2
B Dry and transport the coal
C Have proper combustion by supplying it around the burner
D Preheat the tertiary air used for complete combustion of CO to CO2

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