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.
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 - 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 - 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 - Forced recirculation of furnace gases is practised_______________?
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. - 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. - 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 - Out of the following fuels used in a furnace exhausting flue gas at a temperature of 600°C, the percentage stack loss will be maximum in case of complete combustion of_________________?
A. Furnace oil with air
B. Furnace oil with oxygen
C. Blast furnace gas with air
D. Blast furnace gas with oxygen
