251. Coking coals are invariably
Lignites
Bituminous coals
Semi-anthracites
Anthracites
✅ The correct answer is option B.
Fuel and Combustion MCQs
252. Orsat apparatus is meant for
Gravimetric analysis of flue gas
Finding out combustion efficiency
Direct determination of nitrogen in flue gas by absorbing it in ammoniacal cuprous chloride
None of these
✅ The correct answer is option D.
253. During combustion of gaseous fuels, deficiency of air
Lengthens the flame
Tends to shorten the flame
Does not affect the flame length
Increases the flame temperature
✅ The correct answer is option A.
254. Which is the most matured coal?
Lignite
Bituminous
Semi-anthracite
Anthracite
✅ The correct answer is option D.
255. Oxygen percentage (by weight) in atmospheric air is
19
21
23
29
✅ The correct answer is option C.
256. Bomb calorimeter is used to determine the (where, GCV – Gross Calorific Value. NCV – Net Calorific Value.)
GCV at constant pressure
GCV at constant volume
NCV at constant pressure
NCV at constant volume
✅ The correct answer is option B.
257. Froth floatation is used for
Washing fine coal dust (< 0.5 mm size)
Washing lump coal (> 80 mm size)
Removing ash from the coal based on difference in specific gravity of coal and ash
All of the above
✅ The correct answer is option A.
258. Coals used for the generation of producer gas should have
High caking index
Low fusion point of ash
High volatile matter content
Very low ash content (8-10%)
✅ The correct answer is option C.
259. The main drawback of supplying more excess air in the combustion of fuel is the
Excessive power requirement of air blower
Enhanced sensible heat loss in the flue gas
Intermittant and uncontrolled combustion of the fuel
High exit flue gas temperature from the furnace
✅ The correct answer is option B.
260. Critical Air Blast (CAB) value of coke is a direct measure of its
Reactivity
Hardness
Strength
None of these
✅ The correct answer is option A.