The Loeffler boiler is one of the most famous types of water tube boiler. This article explains the Loeffler boiler working, parts, and applications.
What is a Loeffler Boiler?
Loeffler Boiler is a high-pressure, forced circulation, and internally fired water tube boiler. This type of boiler has a steam circulation pump which uses to circulate steam inside the boiler.
This is an improved model of the Lamont boiler. One main problem with the Lamont boiler is the build-up of salt and debris in the water pipes through which the water flows.
This build-up of debris and salts reduces the heat transfer rate in the water tube’s internal area. The Lamont boilers may also face overheating issues due to the build-up of salts and debris. Due to these reasons, the scientist designed the Loeffler boiler and solved the Lamont boiler issues by blocking the flow of water inside the water tubes.
In this boiler, 70% part of the superheated steam is utilized for the water evaporation in the evaporating drum, and 30% part of the superheated steam is utilized to run the steam turbine.
Working Principle of Loeffler Boiler
The main working principle of the Loeffler boiler is to evaporate the water by taking superheated steam from the superheater. The 30% steam of the superheated steam is used to run the turbine, and 70% steam is used to evaporate the water.
The Loeffler boiler works in the following way:
- A feed pump takes water from the external water source, increases the water pressure, and sends it into the economizer. This economizer preheats the water and sends it into the evaporator drum.
- The 70% part of the superheated steam is sent into the nozzles of the evaporator drum. The nozzle mixes the feed water with this received superheated steam and transforms water into saturated steam.
- After the generation of the saturated steam, the steam circulating pump uses to transfer this output saturated steam into the radiant superheater.
- The radiant superheater uses radiations produced by the fuel combustion, increases the temperature of the saturated steam, and transforms it into supersaturated steam.
- The tubes of the superheater are installed inside the furnace.
- As the steam converts into the superheated steam, it transfers into the convective superheater.
- The convective superheater installs in the path of the hot flue gases. This superheater further increases the temperature of the superheated steam up to 500°C and converts the remaining water particles into steam.
- After passing through the convective superheater, 70% steam is sent to the evaporating drum for evaporating the feed water, and 30% steam is used to run the prime mover of the steam turbine.
- As the steam strikes the steam turbine blades, the blades further transfer their rotation to the generator coil and produce electricity.
- The Loeffler boiler has the capability to generate 140 bar pressure and 100 tonnes/hour of steam.
Read More: Working of Lamont Boiler
Parts of the Loeffler Boiler
The Loeffler boiler has the following major types:
- Safety valve
- Feed pump
- Pressure indicator
- Evaporating drum
- Radiant superheater
1) Water feed Pump
The major component of the Loeffler boiler is the feed pump. This pump is employed to transfer the water into the economizer.
This pump receives water from a reservoir, increases the pressure of the water, and then transfers water to the economizer. The quantity of the pumped water must be equal to the evaporated water in the boiler.
Some types of water tube boilers use an injector to inject the water inside the boiler.
Read More: Different Types of Pumps
The main objective of the economizer is to preheat the water. It collects waste heat from the boiler and transfers this heat to the feed water. This water preheating process increases the efficiency of the boiler and saves energy costs.
The economizer is made of cast iron. It is linked with horizontal pipes. After this preheating process, the water is transferred to the evaporating drum.
Read Also: Different Types of Boilers
3) Evaporating Drum
The main purpose of the evaporating drum is to transform the preheated water into saturated steam.
The evaporating drum uses the superheater’s superheated steam for this process. It has mixing nozzles used to mix preheated water with superheated steam and evaporate the water.
4) Centrifugal Pump or Steam Circulating Pump
The Loeffler boiler has a centrifugal pump which uses for the steam circulation in the boiler. It installs between the radiant superheater and evaporating drums.
The centrifugal pump or steam circulating pump has an impeller and a diffuser. The impeller increases the speed of the steam and the diffuser is employed to convert this increased speed into pressure.
Read More: Working of Centrifugal Pump
5) Mixing Nozzle
The mixing nozzle plays an important role in the conversion of the water into steam. This nozzle is located inside the evaporating drum. This nozzle uses to mix the preheated feed water and the superheated steam and evaporates the water.
The drain uses to clean the evaporating drum. When the contaminations are gathered inside the evaporating drum, the drain uses to clean and remove the contamination from the drum.
7) Radiant Superheater
This Superheater takes heat from the radiation of the combustion chamber and increases the temperature of the saturated steam. It converts the saturated into superheated steam.
Read More: Types of Fire-tube Boilers
8) Convective Superheater
After passing through the radiant superheater, the produced superheated steam is transferred to the convective superheater. The convective superheater increases the steam temperature up to 500℃ and fully converts water vapors into steam. This process increases the temperature of the boiler.
After this process, the 30% superheated steam transfers to the steam turbine, and the remaining 70% steam sends to the evaporating drum.
As the steam enters the turbine, it strikes the blades of the turbine. The steam turbine blades extract the pressure energy of the steam and convert this energy into the shaft’s rotational energy. This rotational energy of the shaft uses to rotate the generator coil, which produces electricity.
The turbine has two types:
- High-Pressure Turbine: This steam turbine uses to extract the pressure energy from the high-pressure superheated steam.
- Low-Pressure Turbine: It uses to extract pressure energy from the low-pressure superheated steam.
Read Also: Working of Steam Turbine
10) Fan Blower
It uses to direct the air from the air preheater inside the combustion chamber for burning the fuel.
Advantages of Loeffler Boiler
- The Loeffler boiler has the capacity to use salt water for steam production.
- It has a compact design.
- It has a quiet operation.
- These types of water tube boilers have a clean operation.
- It has the capability to work under very high pressure than fire-tube boilers.
Disadvantages of Loeffler Boiler
- It uses an additional evaporating drum which increases the weight of the boiler.
- It has large size.
- There is the formation of bubbles on the water’s surface, which reduces the rate of heat transfer.
- It has a high cost.
Applications of Loeffler Boilers
- Loeffler boilers are most commonly used to generate steam for power production.
- They are used in the marine industry.
What are the applications of Loeffler Boiler?
The Loeffler boilers are used in medical, textiles, and many other industries. These types of boilers also use in power plants for power generation.
What is a High-Pressure boiler?
A boiler that operates at high pressure is known as a high-pressure boiler. All water tube boilers operate at high pressure.
Is the Loeffler boiler a high-pressure boiler?
A Loeffler boiler is a high-pressure boiler. It has the capacity to operate up to 100 bars.
Why evaporating drum is used in the Loeffler boiler?
An evaporating drum uses to evaporate the water. It has a nozzle used to mix the superheated steam and water. After the mixing process, the water is evaporated.
What are the parts of the Loeffler Boiler?
- Steam Main
- Air Preheater
- Mixing Nozzle
- Radiant Superheater
- Steam Circulating Pump
- Evaporating Drum
- Convective Superheater
- Feed Pump