Fuels and Combustion Solved Problems - Set 26 - ObjectiveBooks

# Practice Test: Question Set - 26

1. Flue gas discharge velocity through chimney of a big thermal power plant may be around __________ m/sec.
(A) 0.5
(B) 10
(C) 50
(D) 500

2. Grindability index of a coal is 100. It implies that the
(A) Coal can be pulverized with great difficulty
(B) Coal can't be pulverized
(C) Coal can be easily pulverized
(D) Power consumption in grinding the coal will be very high

3. When steam is passed over coal resulting in the endothermic reaction represent by, C + H2O = CO + H2, it is called the __________ of coal.
(A) Carbonization
(B) Oxidation
(C) Coalification
(D) Gasification

4. Naphthalene recovered from coke oven gas is used
(A) As moisture proof coating on fibres
(B) As moth balls (insecticides)
(C) As a fuel in furnaces
(D) For making electrodes

5. Dust content in raw blast furnace gas is about __________ gm/Nm3; hence it is cleaned to the dust level of about < 10 mg /Nm3 before use.
(A) 15-30
(B) 1-2
(C) 70-100
(D) 150-200

6. When incomplete combustion loss is high, the flue gas analysis shows large amount of
(A) CO2
(B) CO
(C) O2
(D) C

7. Rate of low temperature oxidation of coal due to bad storage conditions
(A) Decreases with increase in surface area
(B) Does not vary with increase in surface area
(C) Is more for low volatile coal compared to high volatile coal
(D) Is accelerated by storage in large heaps with small surface to volume ratio

8. One kg of carbon for theoretically complete combustion requires __________ kg of air.
(A) 11.5
(B) 0.5
(C) 23
(D) 12

9. Which of the following is called "blue gas”?
(A) Coke oven gas
(B) Water gas
(C) Natural gas
(D) Producer gas

10. __________ process is meant for direct hydrogenation of coal to produce liquid fuel.
(A) Fischer-Tropsch
(B) Bergius
(C) Lurgi
(D) None of these

11. Temperature of preheated air used for the transportation of pulverized 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 combustion chamber
(B) Risk of explosion
(D) Incomplete combustion of coal

12. During combustion of a gaseous fuel, the presence of a non-luminous flame is an indication of the
(A) Incomplete combustion
(B) Complete combustion
(C) High oxygen in flue gas
(D) None of these

13. Use of excess of combustion air in the combustion of fuels results in
(A) Heat losses
(B) Long flame
(C) Condensation of water vapor from the fuel gas
(D) None of these

14. If oxygen content in the flue gas rises too high, fuel is being wasted by
(A) Incomplete combustion
(B) Dry gas/stack gas loss
(C) Moisture loss
(D) None of these

15. Which of the following fuels is generally not used in thermal power plant boiler firing?
(A) Furnace oil, light diesel oil and tar/PCM
(B) Pulverized coking coal
(C) Coal middling from washeries
(D) B.F. gas, coke oven gas and L.D. converter gas

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