71. Which of the following has the least calorific value (kcal/Nm³) ?
Blast furnace gas
Coke oven gas
Sewage gas
Natural gas
✅ The correct answer is option A.
Fuel and Combustion MCQs
72. Which of the following is not increased by using preheated combustion air in place of ordinary air at room temperature?
Calorific value of the fuel
Flame temperature achieved
Speed of combustion of fuel
Heat transfer rate to the stock in the furnace
✅ The correct answer is option A.
73. With increase in calorific value of fuels, their adiabatic flame temperatures
Increase
Decrease
Remain unchanged
May increase or decrease ; depends on the quantity of products of combustion
✅ The correct answer is option D.
74. Stack (chimney) height in a big thermal power plant is dictated by the
Pollution control aspect
Draught to be created
Limitation of constructional facilities
None of these
✅ The correct answer is option B.
75. Quantity of coke oven gas produced by high temperature carbonisation of one ton of dry coal may be around __________ Nm³.
30
300
3000
30, 000
✅ The correct answer is option B.
76. Tolerable concentration of toxic carbon monoxide in atmospheric air is about __________ PPm.
50
1000
5000
10000
✅ The correct answer is option A.
77. A coal having higher volatile matter content, has lower
Smoking tendency on burning
Coke oven gas yield on carbonisation
Chance of catching fire during storage in open space
Ignition temperature
✅ The correct answer is option D.
78. Temperature of coke oven gas just before entering into saturator (for recovery of NH₃) is about __________ °C.
30
65
120
180
✅ The correct answer is option B.
79. Bomb calorimeter is used for the determination of calorific value of the __________ fuels.
Gaseous
Solid
Liquid
Both B and C
✅ The correct answer is option D.
80. Which of the following accentuates clinker-ing trouble on furnace grate burning coal?
Low reactivity of carbonised residue containing high proportions of iron & sulphur
Low forced draught and fuel bed temperature
Thick fire bed and preheated primary air
All of the above
✅ The correct answer is option D.