A. 21% excess air has been used for combustion
B. 21% excess oxygen has been used for combustion
C. Complete combustion of fuel has taken place
D. No excess air has been used for combustion
Related Mcqs:
- A liquid/gaseous fuel containing hydrocarbons and high amount of sulphur is burnt with 40% excess air. The flue gas still contains large amount of carbon monoxide. This may be due to the_________________?
A. Presence of large quantity of hydrogen in the fuel
B. Low calorific value of the fuel
C. High sulphur content in the fuel
D. Lack of thorough mixing of fuel with air - The maximum percentage of CO2 in a flue gas (from a carbonaceous fuel) can be_________________?
A. 21
B. 77
C. 79
D. 29 - Explosion limit of blast furnace gas is 37 to 71% gas in gas-air mixture. It means that the blast furnace gas will explode when burnt in a confined space, if its concentration in the gas-air mixture is _______________ percent?
A. 71%
C. In between 37 & 71%
D. None of these - 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 __________________?
A. 20
B. 12.5
C. 0
D. 10 - A fuel containing carbon and carbon monoxide (but containing no hydrogen or its compounds) is burnt in pure oxygen at constant pressure. Its gross calorific value as compared to net calorific value will be_________________?
A. More
B. Less
C. Same
D. Data insufficient; can’t be predicted - A sample of natural gas containing 80% methane (CH4) and rest nitrogen (N2) is burnt with 20% excess air. With 80% of the combustibles producing CO2 and the remainder going to CO, the Orsat analysis in volume percent is_________________?
A. CO2 : 6.26, CO : 1.56, O2 : 3.91, H2O :15.66, N2 : 72.60
B. CO2 : 7.42, CO : 1.86, O2 : 4.64, N2:86.02
C. CO2 : 6.39, CO : 1.60, O2 : 3.99, H2O:25.96, N2:72.06
D. CO2 : 7.60, CO : 1.90, O2 : 4.75, N2 : 85.74 - Fuel gases containing hydrocarbons (e.g. coke oven gas) are not preheated before burning, mainly because __________________?
A. The hydrocarbons crack thereby choking and fouling the heat transfer surface by carbon soot
B. It reduces its calorific value tremendously
C. It reduces its flame temperature tremendously
D. There are chances of explosion during preheating - The calorific value of a gas of composition CO2 = 20%, H2 = 50%, CH4 = 30%, is y. If the composition of gas is changed to H2 = 50%, CH4 = 30%, CO2 = 10%, N2 = 10%, then the calorific value will be___________________?
A. y
B. 0.95 y
C. 1.05 y
D. 1.8 y - Theoretical flame temperature of a fuel is that temperature which is attained, when the fuel is completely burnt ‘using theoretical amount of air in___________________?
A. Air
B. Oxygen
C. Either A. or B.
D. Either A. or B. without gain or loss of heat - The average molecular weight of a flue gas having the composition by volume as CO2 = 25%, O2 = 25%, N2 = 50% will be___________________?
A. 27.6
B. 23
C. 47.3
D. 42.9
