A. To increase heat transfer by convection
B. To ensure uniform temperature
C. In furnaces, operating below 750°C
D. All A., B. and C.
Related Mcqs:
- In a furnace, the heat taken by the charge/stock and the heat lost to the furnace structure & flue gases depends on the__________________?
A. Rate of firing and emissivity of flame
B. Thermal conductivity of the charge & structural materials of furnace
C. Nature of process; whether batch, continuous or intermittent
D. All A., B. and C. - Which furnace employs an I.D. fan for the removal of flue gases from the furnace ?
A. Coke oven
B. Blast furnace stoves
C. Beehive coke oven
D. High pressure boiler - Combustion of furnace oil in a furnace (soaking pit) with preheated combustion air at 400°C results in saving of about __________ percent furnace oil as compared to its combustion with atmospheric air, if the flue gas outlet temperature from the soaking pit is 1200°C ?
A. 5
B. 60
C. 20
D. 40 - In a furnace employing forced draught as compared to induced draught______________________?
A. Air is sucked in, so air leaks are more and hence the furnace efficiency is reduced
B. The fan operates hot and hence blades are liable to corrosion and erosion
C. Positive pressure exists in the furnace
D. None of these - Design of waste heat boiler for recovery of waste heat from furnace gases depends upon the_________________?
A. Quantity & temperature of waste gas
B. Dust concentration & nature of dust in waste gas
C. Corrosive nature of the waste gas
D. All A., B. and C. - Presence of SO2 in furnace gases attacks the ferrous metal by way of_________________?
A. Accelerating the rate of scaling
B. Causing metal embrittlement
C. Attacking the grain boundaries; particularly severe on low carbon and nickel bearing steels at
high temperature
D. All A., B. and C. - Circulation of gases in furnace is caused by the_________________?
A. Change in volume during a change of temperature
B. Difference in density between hot and cold gases
C. Furnace pressure in conjunction with draft in flues
D. All A., B. and C. - Which of the following is not a continuous waste heat recovery equipment from the flue gases going out of furnace ?
A. Economiser
B. Regenerator
C. Ceramic recuperator
D. Waste heat boiler - Which of the following is not an additive for flue gases from furnace to reduce its dewpoint ?
A. Ammonia
B. Fine dolomite
C. Alkaline powders
D. None of these - Ceramic coating material for furnace refractory, which increases its emissivity and thus the radiation heat transfer rate in the furnace, comprises of_________________?
A. Graphite powder
B. Thoria
C. Zircon powder
D. Beryllium
