Correct Answer - Option 1 : Injector
Explanation:
In boiler operation the Injector is used to feed water into the boiler and superheater, economiser, preheater are related to the flue gas operation.
Injector:
The function of the injector is to feed water into the boiler and thus it is not related to flue gas operation.
- In an injector, water is delivered to the boiler by steam pressure. The kinetic energy of steam is used to increase the pressure and velocity of feed water.
- It is commonly used for vertical and locomotive boiler and is not used in large capacity high-pressure boilers.
- It is also used where space is not available for the feed pump.
Superheater:
The function of the superheater is to increase the temperature of the steam above its saturation point.
- It is a boiler accessory and can be used on both water-tube and fire-tube boilers.
- The use of a superheater reduces the erosion of turbine blades, steam consumption of the engine or turbine.
- Superheater increases the efficiency of a steam plant.
Economizer:
It is a device in which waste heat of the flue gases is utilized for heating the feed water. There are two types of Economiser
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Independent type: It is installed at the passage of a flow of flue gases from the boiler to the chimney.
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Integral type: It is a part of the boiler heating surface and is installed within the boiler setting.
The advantages of economizer use are -
- The temperature range between various parts of the boiler is reduced which results in a reduction of stresses due to unequal expansion.
- The evaporative capacity of a boiler increases.
- The overall efficiency of the plant is increased.
Air Preheater:
Its function is to increase the temperature of the air before it enters the furnace.
- It is placed after an economizer so the flue gases pass through the economizer and then to the preheater.
- Preheated air accelerates the combustion and facilitates the burning of coal.
- Degree of preheating depend upon:
- Type of fuel.
- Type of fuel-burning equipment.
- Rating at which the boiler and furnace are operated.
