Vapour is a
Pure substance
Perfect gas
Mixed phase of liquid and gas
Substance homogeneous and invariable in chemical composition
Calorific value of steam coal lies in the range
1000-2500 kcal/kg
3000-4500 kcal/kg
5000-8000 kcal/kg
9000-12500 kcal/kg
The percentage of carbon in bituminous coal is of the order of
20-40%
30-50%
50-65%
65-80%
Pulverization of coal is done
To get high burning rate
To keep the burning losses to minimum
For coals with high ash content
For coals which have high heating value
Which is not the desirable property of a good fuel?
Economical in cost
Minimum sulphur content
High ignition point
High heating value
Sulphur content in a fuel
Aids in proper combustion
Has high corrosive effect
Facilitates ash removal
Lowers the ignition point
The presence of ………….in boiler exhaust indicates incomplete combustion
Oxygen
Water vapours
CO
CO2
Turbidity in a boiler feed water causes
Scale formation
Corrosion
Sludge
Embrittlement
What salts of calcium and magnesium cause temporary hardness of boiler feed water?
Chlorides
Bicarbonates
Nitrates
Sulphites
Foaming in a boiler feed water is due to the presence of
Oil
Calcium carbonate
Manganese
Sodium chloride
Scale is formed on the boiler surface when the boiler feed water contains
Dissolved gases
Oils and suspended solids
Calcium and magnesium salts
Insoluble compounds
Deaeration of feed water is done to reduce
Necessity of priming in feed pumps
Mass of water to be handled
Corrosion caused by dissolved oxygen
Amount of heat required to convert water into steam
Oxygen can be removed from the boiler feed water by the addition of
Alum
Calcium carbonate
Sodium sulphite
Cuprous chloride
Which of the following characteristic decides that the Lancashire boiler is a fire tube boiler?
Horizontal erection
Coal firing
Use of two flue tubes through which flow the hot gases and water is kept around the tubes
All around brick-work setting for the circulation of hot gases
Choose the false statement
Draught is the small difference between the pressure of outside air and the gases at the base of chimney
Draught produced by chmney varies with external weather conditions and the temperature of furnace gases
Balanced draught is the chmney draught supplemented by induced draught
Forced steamjet draught results in more heat loss to flue gases