Power Plant Engineering Multiple Choice Questions on “Coal Firing Systems – II”.
1. Presence of free moisture in coal is most disadvantageous during __________
a) combustion of fire slacks on the grates
b) its pulverisation
c) handling (e.g. when emptying wagons)
d) none of the mentioned
Answer: b
Clarification: As pulverisation of coal is a power consuming process, the presence of free moisture in coal is most disadvantageous.
2. Abrasion index of blast furnace coke should be around __________ percent.
a) 20
b) 35
c) 80
d) 55
Answer: c
Clarification: Abrasion index of blast furnace coke should be around 80 percent. More this abrasion index, which is an indicator of Abrasion; more is the combustibility.
3. Which of the following petrographic constituents of coal is non-coking?
a) Durain
b) Vitrain
c) Clarain
d) Fussain
Answer: d
Clarification: Among the mentioned petrographic constituents, Fussain is non-coking.
4. ‘Fat’ coal means a coal having __________
a) low ash content
b) non-smoking tendency
c) high volatile matter
d) low calorific value
Answer: c
Clarification: ‘Fat’ coal means a coal having high volatile matter.
5. Initial pressure of oxygen introduced into the ‘bomb’ of the bomb calorimeter for determination of calorific value of coal/fuel oil may be around __________ atm.
a) 20-30
b) 60-65
c) 95-100
d) 3-5
Answer: a
Clarification: Initial pressure of oxygen introduced into the ‘bomb’ of the bomb calorimeter for determination of calorific value of coal/fuel oil may be around 20-30 atm.
6. Proximate analysis of coal determines its __________ content.
a) moisture, ash, sulphur & volatile matter
b) moisture, volatile matter, ash & fixed carbon
c) moisture, sulphur, nitrogen & fixed carbon
d) none of the mentioned
Answer: b
Clarification: Proximate analysis of coal determines its moisture, volatile matter, ash & fixed carbon content.
7. If the specific heat of gaseous products of combustion of a fuel is high, the abiabatic flame temperature will be?
a) very high, if the fuel is of low calorific value
b) low
c) high
d) none of the mentioned
Answer: b
Clarification: If the specific heat of gaseous products of combustion of a fuel is high, the abiabatic flame temperature will below.
8. “Overfire burning” in a furnace is a phenomenon characterised by the __________
a) burning of carbon monoxide and other incombustibles in upper zone of furnace by supplying more air
b) supply of excess fuel
c) supply of excess air
d) none of the mentioned
Answer: a
Clarification: “Overfire burning” in a furnace is a phenomenon characterised by the burning of carbon monoxide and other incombustibles in upper zone of furnace by supplying more air.
9. Atomising steam to fuel oil ratio in a burner should be around __________
a) 0.5
b) 1.5
c) 2.5
d) 3.5
Answer: a
Clarification: A low atomising fuel oil ratio is favourable enough to ensure good combustion.
10. Presence of free moisture in coal during its high temperature carbonisation __________
a) increases the loss of fine coal dust from the ovens when charging
b) protects the volatile products from pyrolysis (cracking) in the presence of hot coke and hot oven walls
c) reduces the coking time
d) none of the mentioned
Answer: b
Clarification: The presence of free moisture in coal during its high temperature carbonisation protects the volatile products from pyrolysis (cracking) in the presence of hot coke and hot oven walls.