Loeffler Boiler is a high pressure, forced circulation and water tube boiler with the internal furnace. In this boiler, 65 percent of superheated steam is used to evaporate the water. Everything happens in the Evaporating Drum. All done by the help of Mixing Nozzle. Remain 35 percent of superheated steam, uses by two Steam Turbines.
Construction of Loeffler Boiler:
Loeffler Boilers consist of a feedwater pump and it circulates water to the Economizer. Generally hot flue gas passes through the economizer and feed water pre-heated by flue gas. Then an Evaporating Drum which is connected with Economizer. Another side of the Evaporating Drum connected with Radiant Super Heater. There is a Convective Super Heater which is connected with a Super Heater.
By the way, don’t forget about the internal furnace. Furnace usually stays at the middle and flue gas pass through the Economizer, Radiant Super Heater, Convective Super Heater, and Blower. You will also find a Mixing Nozzle inside the Steam Evaporating Drum. Mixing Nozzle mixes the steam from the superheater with feed water and evaporates them in Evaporating Drum.
Working Principle of Loeffler Boiler:
When Furnace generates enough heat by burning fuel then, flue gas passes through the Economizer. This means Economizer is already heated. Now Feed Water Pump forces the water to get in Economizer Tube. Then water becomes pre-heated by the Economizer. This arrangement generally increases the efficiency of the boiler. Feed Pump force the pre-heated feed water from Economizer Tube to the Evaporating Drum. From Evaporating Drum steam is supplied to the Radiant Super Heater. Radiant Super Heater usually stays at the top of the combustion chamber.
Steam generated by the Radiant Super Heater called Saturated Steam. Then Saturated Steam passes through the Convective Super Heater. It is one of the most important components of the Loeffler Boiler. Convective Super Heater increases the temperature of Saturated Steam to a temperature of 500 Degree Calicoes. Then Super Heated Steam supply to the Evaporating Drum through the Mixing Nozzle which stays in the Evaporating Drum.
But between Convective Super Heaters to Evaporating Drum a High-Pressure Steam Turbine use 35 present of Super Heated Steam. Remaining 65 percent Super Heated Steam supplies to the Evaporating Drum. After that from the High-Pressure Steam Turbine stem supply to the Steam Re-heater. Then from Steam Re-heater steam supply to the Low-Pressure Steam Turbine. From this Low-Pressure Steam Turbine, steam supplied to the Prime Mover.
Fresh air needs to supply to the Combustion Chamber in Loeffler Boiler. There is a Blower you will find at the top of this boiler. The air before entering the Blower it passes through the air pre-heater. It pre-heats the air by the flow of flue gas before entering the Loeffler Boiler Combustion Chamber. This agreement also increases the total efficiency of the boiler like the Economizer.
Advantage and Disadvantage of Loeffler Boiler:
The best advantage of Loeffler Boiler is it can use salt water for steam generation. Because deposition of salt and sediments in the inner surface of the water tube has been removed in this boiler. In this boiler, Feed Water converted into steam by its generated superheated steam and this is a specialty of this boiler. Loeffler Boiler has the capacity to produce 100 tonnes per hour of steam at a temperature of 500 Degree Calicoes and at a pressure of 140 Bar (142.76 Kilogram Force Per Square Centimeter). But Loeffler Boiler only converts energy just using 35 percent of the generated steam.