Power Plant Engineering Multiple Choice Questions on “Pulverisation and Gasifiers”.
1. Temperature of preheated air used for the transportation of pulverised coal through pipes to the burner of a boiler furnace is restricted to a maximum limit of about 300° C to avoid the __________
a) requirement of large volume of combustion chamber
b) incomplete combustion of coal
c) risk of explosion
d) chances of clinker formation
Answer: c
Clarification: Temperature of preheated air used for the transportation of pulverised coal through pipes to the burner of a boiler furnace is restricted to a maximum limit of about 300° C to avoid the risk of explosion owing to the reacting mixture.
2. The temperature at which plastic layer formation takes place during carbonisation of coal varies from __________ °C.
a) 100-150
b) 350-450
c) 700-850
d) 550-650
Answer: b
Clarification: The temperature at which plastic layer formation takes place during carbonisation of coal varies from 350 to 450 °C.
3. Which of the following is not a by-product recovered in a high temperature coal carbonisation plant?
a) Benzol
b) Ethylene
c) Pitch-cresosote mixture (PCM)
d) Naphthalene
Answer: b
Clarification: Apart from Ethylene all the others are by-products obtained in high temperature coal carbonisation plant.
4. Pick out the wrong statement.
a) Regulation of furnace temperature and atmosphere (oxidising or reducing) is easily possible with pulverised fuel firing
b) Low grade coal can be used, but generally high volatile matter coals are more suitable for making pulverised fuel
c) Pulverised fuel can be completely burnt with less percentage of excess air compared to lump coal
d) None of the mentioned
Answer: d
Clarification: All the mentioned statements are correct.
5. Flue gas discharge velocity through chimney of a big thermal power plant may be around __________ m/sec.
a) 0.5
b) 500
c) 10
d) 50
Answer: c
Clarification: Flue gas discharge velocity through chimney of a big thermal power plant may be around 10 m/sec.
6. Calorific value of coal middling generated in coal washeries during washing of coal may be around __________ Kcal/kg.
a) 1000
b) 4000
c) 6000
d) 8000
Answer: b
Clarification: Calorific value of coal middling generated in coal washeries during washing of coal may be around 4000 Kcal/kg.
7. Combustion of pulverised coal as compared to that of lump coal __________
a) develops a non-luminous flame
b) can be done with less excess air
c) develops a low temperature flame
d) provides a lower rate of heat release
Answer: b
Clarification: Combustion of pulverised coal as compared to that of lump coal can be done with less excess air.
8. The decrease in the atomic number is not observed in case of __________
a) alpha emission
b) beta emission
c) gamma emission
d) none of the mentioned
Answer: b
Clarification: There is no change in the atomic number as the number of electrons remains the same.
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