“Overfire burning” in a furnace is a phenomenon characterised by the __________________?

Related Mcqs:

1. Which of the following accentuates clinkering trouble on furnace grate burning coal ?

   A. Low reactivity of carbonised residue containing high proportions of iron & sulphur
   B. Low forced draught and fuel bed temperature
   C. Thick fire bed and preheated primary air
   D. All A., B. and C.

2. A gaseous fuel in order to develop luminosity on burning, must contain __________________?

   A. Carbon monoxide
   B. Hydrocarbons
   C. Hydrogen
   D. Oxygen

3. A particular coal is said to be free burning when it __________________?

   A. Burns completely
   B. Gives smokeless burning
   C. Shows little or no fusing action
   D. None of these

4. 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

5. 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

6. 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

7. 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

8. Incomplete combustion of a fuel is characterised by the high _______________ in the flue gas?

   A. Smoke
   B. Temperature
   C. Oxygen
   D. Carbon monoxide

9. Coal is pulverised before burning in large capacity boiler furnaces mainly to____________________

   A. Ensure its complete combustion
   B. Facilitate easy ash removal
   C. Enhance its calorific value
   D. Provide trouble free operation

10. A travelling grate stoker is meant for the efficient burning of ______________ coal?

    A. Caking
    B. Pulverised
    C. Non-caking
    D. High ash