What is a Benson Boiler? | How does a Benson Boiler work?

What is Benson Boiler?

A Benson boiler is a supercritical, drumless, high pressure, and forced circulation water tube boiler. In 1922, Mark Benson invented the Benson boiler. It has the capability to generate high steam pressure. It is a supercritical boiler.

The Benson boiler compresses the water up to supercritical pressure due to that bubbles don’t produce on the surface of the water. These bubbles don’t generate because as the water is compressed at supercritical pressure, the latent heat of the water becomes equal to zero, and the density of the water becomes equal to the density of the steam. 

As the water’s latent heat is zero, it directly converts into steam without producing bubbles on the water surface.

Therefore, this type of water tube boiler doesn’t require a drum to separate the air bubbles from the surface of the water.

Working of Benson Boiler

A Benson boiler works on the thermal convection principle. It directly transforms water into steam. A Benson boiler works in the following way:

Benson Boiler

  • First of all, a blower gets air from the atmosphere. It increases the speed and pressure of the air and transfers it into the preheater.
  • As the preheater receives air, it increases the temperature of the air and converts it into hot gases. After this preheating process, the preheater transfers final hot gases into the furnace.
  • A feed pump raises the water pressure up to supercritical pressure and transfers this water in the economizer. The economizer preheats the water by utilizing the heat of the hot flue gases. The economizer increases the boiler efficiency.
  • After passing through the economizer, the water enters the radiant superheater. It increases the water temperature up to supercritical temperature. This superheater takes heat from the combustion chamber and transfers this heat to water. In this process, the water partially remains in a liquid state and partially converts into steam. This mixture of water and steam is sent to a convective superheater.
  • As the mixture of steam and water reaches into the convective superheater, it fully converts the mixture of steam and water into superheated steam.
  • As the water fully converts into steam, it transfers to the steam turbine for electricity production.
  • This type of water tube boiler is also called a lightweight boiler because it doesn’t use any water and steam separation drum.
  • The Benson boiler has up to 90% thermal efficiency.
  • It has a steam generation rate of up to 135 tons/hour and steam pressure up to 250 bar.

 Parts of Benson Boiler

The major components of the Benson boiler are given below:

  1. Blower
  2. Benson Chamber
  3. Feed Pump
  4. Economizer
  5. Furnace
  6. Chimney
  7. Safety Valve
  8. Convection superheater
  9. Convection evaporator
  10. Radiant superheater

Benson Boiler parts

1) Feed Pump

The main objective of this pump is to supply water at supercritical pressure (i.e., 225 bar) from the hot well into the boiler. It increases the pressure of the water by using an impeller (in case of a centrifugal pump) or a piston (in case of a reciprocating pump) and sends this increases pressure water into the boiler. There are different types of feed pumps used to pump the water into the boiler.

Read Also: Types of Pumps

2) Benson Chamber

The Benson is the most important of the boiler. This is an external part of the boiler. It contains all other components of the boiler.

3) Blower

The blower uses to direct the air with very high speed in a specific direction. In the case of a boiler, the blower connects with the air preheater.

It takes air from the atmosphere and increases the air speed. After increasing the air speed, it transfers air into the air preheater.

Read More: Different types of Water Tube Boilers

4) Air Preheater

The main objective of the air preheater is to heat the air. As the blower transfers air into the air preheater, the preheater gets heat from the furnace, heats the air, and converts the air into hot flow gases.

This component of the boiler increases the thermal efficiency of the fuel.

5) Furnace

It uses to burn fuel. It is also known as a firebox. This part of the Benson boiler has the highest temperature.

As the furnace burns the fuels, the heat generates, which increases the temperature of the flue gases, and flue gases start moving outside the water tubes. The furnace has a fire hole and a grate.

Read Also: Different types of Fire-tube Boilers

6) Economizer

This is another most important part of the water tube boiler. It uses to heat the water before water entry into the boiler. 

Firstly, the feed pump transfers water into the economizer, and the economizer increases the temperature of the water. After the heating process, a centrifugal pump uses to transfer this heated water into the boiler. The economizer increases the overall efficiency of the boiler.

7) Radiant Superheater

The radiant superheater increases the temperature of the water by getting heat from the radiation produced due to the combustion of fuel. It increases the water temperature up to supercritical temperature. These radiations are generated due to the fuel-burning inside the furnace.  

8) Convection Evaporator

The main objective of convection evaporation is to evaporate the water completely. This component of the Benson boiler completely transforms the superheated water into steam. In this process, the heat transfers from the hot flue gases to water through the convection process.

9) Convection Superheater

This superheater increases the temperature of steam according to the requirements (i.e., up to 650° C).

10) Steam Outlet Pipe

This pipe uses to supply superheated steam from the boiler to the steam turbine.

11) Chimney

As the fuel burns, it emits smoke. This produced smoke and waste gases enter the chimney from where it transfers into the atmosphere.

12) Ash pit

As the fuel is burnt, it produces ash. This ash collects into the ashpit, which installs below the boiler grate.

Read Also: Different types of Boilers

Advantages and Disadvantages of Benson Boiler

The Benson boiler has the following advantages and disadvantages:

Advantages of Benson Boilers

  1. This type of the boiler has less weight than other water tube boilers.
  2. It doesn’t need a drum for the separation of water and steam.
  3. There is no formation of bubbles on the water surface.
  4. It can start within 15 minutes.
  5. It has a high steam generation rate of up to 135 tones/hour.
  6. The Benson boiler has low cost because it doesn’t use a drum.
  7. It is portable. You can easily transfer it from one place to another.
  8. This is one of the most efficient boilers. It has the capability to achieve up to 90% thermal efficiency.
  9. It has small tubes with a low diameter.

Disadvantages of Benson Boiler

  1. It is very hard to control for various load conditions.
  2. If there is not a sufficient supply of water, the tubes may overheat.
  3. Due to its low storage capacity, close coordination of water inlets, water supply, and steam is required.
  4. The use of unclean water causes large amounts of deposits to form on the heated surface.
  5. This boiler needs a regular inspection to avoid an explosion.

Applications of Benson Boiler

  1. This boiler uses in various applications to produce steam for electricity or mechanical power production.
  2. The Benson boiler is used in large hydroelectric power plants because it has a high steam generation rate (i.e., 135 tones/hour).

FAQ Section

What Are Benson Boilers Used For?

A Benson Boiler uses to convert water into steam for generating mechanical power or electricity for different equipment. It has the capacity to produce 135 tones/hour steam and 250 bar pressures.

Who invented the Benson Boiler?

In 1922, Mark Benson invented the Benson boiler.

What are the Features of the Benson Boiler?

  • It has low weight.
  • These boilers don’t need any drum for separating steam from water.
  • It has a high steam generation rate.
  • It doesn’t generate bubbles on the water surface.

What is the thermal efficiency of the Benson Boiler?

The thermal efficiency of the Benson boiler is up to 90%.

Read More
  1. Different types of Boilers
  2. Types of Water Tube Boilers
  3. Types of Fire-tube Boilers
  4. Working of Locomotive Boiler
  5. Working of Lancashire Boiler

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