For every 10% increase in the excess air; the fuel consumption increases by _______________ percent?

Related Mcqs:

1. As the C/H ratio of the fuel increases, the amount of CO2 formed on combustion _______________ for the same percentage of excess air?

   A. Decreases
   B. Increases
   C. Remain same
   D. May increase or decrease depending on the type of fuel

2. The optimum percentage of excess air for combustion depends upon the _______________ of the fuel?

   A. Type (solid, liquid or gaseous)
   B. Calorific value
   C. Sulphur content
   D. Ignition temperature

3. Furnace oil consumption in a furnace for a given duty employing preheated combination air (at 300°) may be reduced by about ______________ percent as compared to the use of atmospheric combustion air?

   A. 5
   B. 10
   C. 20
   D. 35

4. For the case of a fuel gas undergoing combustion with air, if the air/fuel ratio is increased, the adiabatic flame temperature will_____________________?

   A. Increase
   B. Decrease
   C. Increase or decrease depending on the fuel type
   D. Not change

5. The main drawback of supplying more excess air in the combustion of fuel is the_________________?

   A. Excessive power requirement of air blower
   B. Enhanced sensible heat loss in the flue gas
   C. Intermittent and uncontrolled combustion of the fuel
   D. High exit flue gas temperature from the furnace

6. Supply of excess air for complete combustion of fuel is necessitated to facilitate___________________?

   A. Its thorough mixing with air
   B. Attainment of chemical equilibrium
   C. Attainment of high temperature
   D. None of these

7. 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

8. Ratio of primary air to secondary air increases with increase in the rank of coal, because the__________________?

   A. High rank coals have higher amount of volatile matter
   B. Ratio of fixed carbon to volatile matter increases
   C. Oxygen content progressively decreases
   D. Calorific value of the coal increases

9. 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

10. Oxygen content in a flue gas was found to be 4%. It implies that excess air used for combustion was around ______________ percent?

    A. 4
    B. 96
    C. 20
    D. 40