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Chemical Engineering
Fuels And Combustion
Quiz 5
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Q.1
During coking of coal, the ash content (percentage)
Increases
Decreases
Remains constant
None of these
Q.2
Abel apparatus is used for those oils, whose flash points are___°F.
<120
>120
>280
300-600
Q.3
Pick out the wrong statement.
Theoretical flame temperature is the temperature attained by the products of combustion, when the fuel is burned without loss or gain of heat
Burning the fuel with theoretically required amount of pure oxygen results in attainment of maximum adiabatic flame temperature
Burning the fuel with excess pure oxygen results in maximum theoretical flame temperature
Adiabatic flame temperatures of actual combustions are always less than the maximum values
Q.4
With increase in moisture content of coal, its
Calorific value increases
Caking properties diminish
Swelling during carbonisation becomes excessive
None of these
Q.5
White flue gas (resembling steam) coming out of the chimney of a thermal power plant indicates that the fuel used in the boiler furnace is
Tar
Coke oven gas
Pitch
Pulverised coke
Q.6
Calorific value of both the solid & liquid fuels can be determined by using __________ calorimeter.
Junker's
Bomb
Boy's
None of these
Q.7
Oxygen percentage (by weight) in atmospheric air is
19
21
23
29
Q.8
Sometimes water is sprayed during coal charging in the coke oven, which helps in
Prevention of clinker formation in the oven
Controlling the dust nuisance while charging the coal
Reducing the cracking of hydrocarbons in the gas and increasing the percentage of CO & H₂ in the gas (due to the endothermic reaction represented by C + H₂O = CO + H₂)
All of the above
Q.9
High rate of heating of coke ovens
May damage its walls due to abrupt excessive swelling of coal
Produces larger size coke
Increases the time of carbonisation
None of these
Q.10
Pick out the wrong statement.
Percentage of ash in coke produced from medium coking coal is more than that in coal
The calorific value (kcal/Nm³) of coke oven gas reduces on removal of hydrogen from it by cryogenic method
Ash is normally removed as
Coal based fertiliser plants in India at Talcher (Orissa) and Ramagundam (A.P) employ Kopper-Totzek process of coal gasification
Q.11
Very __________ coals are completely devoid of cokability i.e, it is non coking.
Young
Mature
Both A & B
Neither A nor B
Q.12
Preheating of __________ the flame temperature.
The gaseous fuel before combustion decreases
Combustion air decreases
Either the fuel or the air or both, increases
Either the fuel or the air does not affect
Q.13
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
Q.14
Which of the following fuel gases has the highest calorific value ?
Natural gas
Coal bed methane (CBM)
Liquefied petroleum gas (LPG)
Sewage gas
Q.15
By-products are __________ recovered in 'Beehive ovens'.
Fully
Partially
Not at all
Negligibly
Q.16
Naphthalene is removed from coke oven gas by
Scrubbing with wash oil (a petroleum product)
Adsorbing on bog iron bed
Absorbing in vetro-coke solution
None of these
Q.17
Low temperature oxidation of stored coal results in the
Decrease in its caking power & calorific value
Decrease in its carbon & hydrogen content
Increase in its oxygen content
All of the above
Q.18
Adiabatic flame temperature of a fuel is dependent on the initial temperature of
Fuel
Air
Both A & B
Neither A nor B
Q.19
L.D. converter gas (produced in steel plant) comprises mainly of
CO (upto 65%) & CO₂
CO₂ & H₂
CO & O₂
CO₂ & O₂
Q.20
Which of the following fuel gases is heavier than air?
Blast furnace gas
Coke oven gas
Natural gas
Water gas
Q.21
Low temperature carbonisation of coal takes place at __________ °C.
300
1100
700
150
Q.22
High temperature carbonisation of coal takes place at __________ °C.
2000
600
1100
1600
Q.23
Actual flame temperature is always lower than the adiabatic flame temperature, because there is
No possibility of obtaining complete combustion at high temperature
Always loss of heat from the flame
Both A & B
Neither A nor B
Q.24
Stack heat losses can be minimised by
Controlling the excess air
Oxygen enrichment of combustion air
Using low c.v. fuels
Maintaining proper draft in the furnace
Q.25
The gas which contributes maximum to the heating value of natural gas is
CO
CO₂
H₂
CH₄
Q.26
Which of the following has the highest calorific value?
Lignite
Sub-bituminous coal
Anthracite
Peat
Q.27
Which of the following coke has the least percentage of ash?
Petroleum coke
Beehive coke
Foundary coke
Metallurgical coke
Q.28
__________ of the coal is the basis for Seylor's coal classification.
Proximate analysis
Ultimate analysis
Caking index
Calorific value
Q.29
Low temperature oxidation of coal during storage does not decrease its
Oxygen content
Caking power
Calorific value
None of these
Q.30
The heat of combustion of a fuel
Is equal to the heat of formation
Is always negative
Can't be known without calculating it
Is always positive
Q.31
The ratio of % total carbon obtained in the ultimate analysis of coke and % fixed carbon obtained in the proximate analysis is always
1
< 1
> 1
Unpredictable
Q.32
While the first commercial low temperature coal carbonisation plant is located at Neyveli (in Chennai), the second such plant has been built at
Dankuni (West Bengal)
Dhanbad
Singreni (AP.)
Raniganj
Q.33
The maximum adiabatic flame temperature is attained, when the fuel is burnt with
Theoretically required amount of air
More than theoretically required amount of air
Less than theoretically required amount of air
Theoretically required amount of oxygen
Q.34
Pure carbon is completely burnt in oxygen. The flue gas analysis is 70%CO₂, 20%CO and 10%O₂. The percent excess oxygen used is
20
12.5
0
10
Q.35
Which of the following is not a product of tar distillation?
Phenol & naphthalene
Benzol & pitch
Anthracene & creosote
None of these
Q.36
Shatter index of metallurgical coke on 2 inches and 0.5 inch screen should be respectively around __________ percent.
80 and 97
95 and 100
40 and 70
25 and 97
Q.37
Coke oven gas produced by high temperature carbonisation of coal (as compared to that produced by low temperature carbonisation), has
Higher calorific value
Lower hydrogen content
Both A & B
Neither A nor B
Q.38
The ratio of maximum adiabatic flame temperature in air to that in pure oxygen is always
1
<1
> 1
Unpredicatable
Q.39
Natural draft created by the chimney depends upon
Temperature of the flue gas
Its height
Both A & B
Neither A nor B
Q.40
The cooling medium used in dry quenching of coke is
Nitrogen
Air
Phenolic water
Carbon dioxide
Q.41
Compound coke ovens are those which can be heated by
Both steam and electrical power
Lean gas (e.g., B.F. gas)
Rich gas (e.g., coke oven gas)
Both B and C
Q.42
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
Q.43
Which of the following is a measure of the agglutinating (i.e., binding) property of coal?
Thickness of plastic layer
Caking index
Swelling index
Gray-king index
Q.44
To avoid fire by spontaneous combustion of coal due to its low temperature oxidation, it should be stored in
Shallow and small piles
Fine sizes without the presence of any lump
Closed space without any ventilation facility
Large heaps with small surface to volume ratio
Q.45
Which of the following is not applicable to fluidised bed combustion of coal?
It can not burn low grade coal
It achieves higher fuel combustion efficiency
Less heat transfer surface area is required in boilers
None of these
Q.46
Size of blast furnace grade coke is __________ mm.
25-80
0-15
15-25
>100
Q.47
Steam is intermittently admitted into the fuel bed during the production of producer gas to
Convert CO to CO₂
Increase the combustion rate
Increase the gas production rate
Minimise the chances of clinker formation
Q.48
As the equilibrium moisture content of the coal increases, its
Calorific value increases
Swelling number decreases
Swelling number increases
Bulk density decreases
Q.49
Which of the following will generate maximum volume of product of complete combustion (Nm³/Nm³ of fuel) ?
Carburetted water gas
Blast furnace gas
Natural gas
Producers
Q.50
Use of excess of combustion air in the combustion of fuels results in
Heat losses
Long flame
Condensation of water vapour from the fuel gas
None of these
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