What is Loeffler Boiler?
Loeffler boiler is a water tube boiler used for generating steam by the burning of fuel which is coal and further that is used for the generation of power. It is another extension of the Lamont Boiler.
Loeffler Boiler is a high-pressure, forced circulation and water tube boiler with an internal furnace. In this boiler, 65 percent of superheated steam is used to evaporate the water. Everything happens in the Evaporating Drum. All done with the help of a Mixing Nozzle. Remain 35 percent of superheated steam, uses by two Steam Turbines.
Both the LaMont and Loeffler boiler generates steam with the use of saltwater but in the Loeffler boiler, there is no problem with Salt and sediment under the boiler but in the case of the LaMont boiler there is a problem of salt and sediment under the boiler surfaces.
Components of Loeffler Boiler
- Feed pump: The main function of Feed pump is to feed the water to the main system.
- Air preheater: The air preheater preheats the air before sending it to the combustion chamber.
- Blower: It supplies hot air
- Economizer: It preheats the feed water before entering into the evaporating drum and the economizer increases the boiler efficiency.
- Evaporating drum: It is placed at the lower position of the boiler. It contains the mixing nozzle. Here the feed water is converted into saturated steam with the help of the superheated steam from the superheater.
- Steam Circulating Pump or Centrifugal Pump: It is present in between the evaporating drum and radiant superheated. It circulates the steam into the boiler.
- Radiant Superheater: It superheats the steam with the help of radiation produced by the burnt fuel in the boiler.
- Convective Superheater: It superheats the steam to the desired temperature of above 500 degrees Celsius.
- Turbine: The superheated steam is sent to the turbine blade for rotation and the blade is attached to the shaft which also rotates and, is connected to the induction motor for the generation of electricity.
- Mixing Nozzle: It is present inside the evaporating drum. The main function of mixing nozzles is to mix the steam from the superheater with feed water and evaporates them.
- Chimney: The function of chimneys is to exhaust the burnt gases into the atmosphere.
- Water Level Indicator: It indicates the water level inside the boiler.
- Fusible plug: It protects the boiler against damage due to overheating.
Working of Loeffler Boiler
Its main working principle is to evaporate the feed water by means of superheated steam from the superheater. The hot gases from the furnace are used for superheating. The total produced superheat steam is used in two ways. About 75% is used to evaporate the water and 25% is used to drive the prime mover of the turbine.
The feed water from the economizer tubes is forced to mix with the superheated steam in the evaporating drum.
In the evaporator drums, nozzles are provided. The two-thirds (70%) of superheated steam from the superheater enters into the drum nozzles. The nozzles mix this superheated steam with feed water. This converts the feed water into saturated steam.
The saturated steam, thus formed, is drawn from the evaporating drum by a steam circulating pump. This allows the saturated steam to pass through the radiant superheaters. In radiant superheater, It superheats steam by the method of radiation produced by the burnt fuel in the boiler. Heat transfer to water occurs through the radiation produced.
After the radiant superheater, steam is routed to the convection superheater. The convection superheater is located in the path of hot exhaust gases. In the convection superheater, it superheats steam by the method of convection to the desired temperature of about 500° C.
This steam then passes through the tubes of the combustion chamber walls and then enters the superheater. From the superheater, about one-third (30%) of the superheated steam passes to the turbine and the remaining two-thirds (70%) is used to evaporate the feed water in the evaporating drum.
The Loeffler boiler has the capability to generate 100 tons/hour of steam at a temperature of 500° C and a pressure of 140 bar.
Advantages of Loeffler Boiler
- It uses super-heated steam in evaporator for generation of steam as of heated water. Thus, the operation is salient and clean.
- High circulation rate of steam over tubes reason low temperature difference between the tube and steam.
- Loeffler boiler uses forced circulation of water and is therefore capable to carry high salt concentration than any other type.
- By the use of a radiant superheater, it makes better heat recovery as of the boiler furnace.
- It is capable to react rapidly to sudden variation of load.
- Boiler is compact in design.
Disadvantages of Loeffler Boiler
- Bubbles are formed at inner face of heating tube. Because of which it reduces the heat transfer rate.
- The disadvantage of this boiler is tightness of high-pressure gas passage is essential.
- Evaporating drum is used which increase bulkiness of plant with cost.