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?

Related Mcqs:

1. Correct viscosity of furnace oil at the burner tip for proper atomisation is about 25 centistokes. To reduce the viscosity of high viscosity furnace oil (250 centistokes) to the correct atomisation viscosity (i.e. 25 cst), it should be preheated to about ______________°C?

   A. 70
   B. 85
   C. 105
   D. 145

2. Temperature of preheated air used for the transportation of pulverised coal through pipes to the burner of a boiler furnace is restricted to a maximum limit of about 300° C to avoid the___________________?

   A. Requirement of large volume combustion chamber
   B. Risk of explosion
   C. Chances of clinker formation
   D. Incomplete combustion of coal

3. Use of preheated air for combustion of fuel in the furnace, increases the___________________?

   A. Scale losses of the furnace stock
   B. Calorific value of the fuel
   C. Flame temperature
   D. None of these

4. Which of the following is not increased by using preheated combustion air in place of ordinary air at room temperature ?

   A. Calorific value of the fuel
   B. Flame temperature achieved
   C. Speed of combustion of fuel
   D. Heat transfer rate to the stock in the furnace

5. 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

6. 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

7. Use of excess of combustion air in the combustion of fuels results in__________________?

   A. Heat losses
   B. Long flame
   C. Condensation of water vapour from the fuel gas
   D. None of these

8. Deficiency of combustion air during combustion of a gaseous fuel_____________________?

   A. Lengthens the flame
   B. Causes heat loss of fuel by its partial combustion
   C. Both A. & B.
   D. Shortens the flame

9. Pitch creosote mixture (PCM) as compared to furnace oil is a better fuel, because its ___________________?

   A. Emissivity factor is higher
   B. Sulphur content is lower
   C. Flue gas has lower dew point thereby facilitating more waste heat recovery
   D. All A., B. and C.

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

    A. 0.1
    B. 0.2
    C. 0.5
    D. 1.0