Benson Boiler: 13 Facts You Should Know

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FAQ/SHORT Note

  • What are the major disadvantages of Benson boilers
  • Benson boiler is drumless
  • Maintenance of Benson boiler

Benson boiler

Mark Benson invented Benson boiler, in year 1922.

It can be known by following,

  • High-pressure boiler,
  • Supercritical,
  • Water-tube category,
  • Forced circulation boiler (Water and steam)

It is a supercritical boiler as the feed water is pressurized at supercritical pressure. The reason behind compressing water is to eliminate bubble formation inside the water tube. The appearance of the bubble can not be possible due to the same density of compressed water and steam. Here in the Benson boiler, the water is compressed at supercritical pressure. Because of this process, the latent heat  is going to be zero. There is no latent heat of vaporization, so the water is directly converted into steam. The intermediate stage of bubble formation is eliminated in this boiler.

Working of Benson boiler | Benson boiler experiment

In the this boiler, the water is compressed by feed water pump at supercritical pressure ( order of 225 bar ). There is no latent heat of vaporization, so the water is directly converted into steam. The intermediate stage of bubble formation is eliminated in this boiler. This prevention of bubble formation is the main benefit of the this boiler compared to other average boilers.

We can quickly notice from the figure given in this article,

The feedwater pump is used to compress water and circulate it through the system. The feedwater pump is used to raises the pressure nearly 225 bar. The water is passed through an economizer to absorb waste heat and feed water heating.

After getting primarily heated by the economizer, the water is getting passed through the radiant heater. In a radiant heater, The water is getting heat by radiation, and the temperature of the water increase such that it partly changes its phase into steam. Its temperature is nearly supercritical.

This two phase mixer of steam and water is passed through a convective evaporator in the next step. Here in the convective evaporator, the two phase mixer turned into steam. We can consider it as superheated steam to some degree.

In this boiler, steam from the convective superheater is passed through the superheater to raise its pressure at the required level. This superheated steam is capable of turning a turbine and valuable for electricity generation.

The turbine is rotated with this superheated steam. The turbine is coupled with an electricity generator. Ultimately, the rotation of the electricity generator produces electricity.

Benson boiler design

The different design approach is applied to the this boiler to control proper operating conditions and different high pressure conditions. The boiler should be capable of allowing perfectly stated dry out. The control of the boiler steam generator is such that which includes considering the initial start to an endpoint. It should consist of the water entering into the economizer to superheater outlet.

The two phase flow is maintained at a critical point, and with load around 55%, the flow is turned single phase from two phases.

The control and design of Benson boiler should possess the following criteria,

  • Starting of boiler in cold condition
  • A restart of boiler in warm condition
  • Sustain Cycling load
  • Shut down.

The design is carried out based on Benson point. The Benson point is the point at which the vertical steam separator should operate dry. The fluid inserted in the boiler should be converted into steam due to this vertical steam separator.

The boiler circulation pump kept off during the Benson point. The water is pressurized with the feedwater pump to meet the required operation of the furnace with the required enthalpy raise. With this method, The function of the evaporator and superheater is controlled according to load. The load on the system will get stabilized.

The steam will get reheated if it violates the requirement. The setpoint load is maintained with control of temperature at various stages.

The temperature in these conditions is maintained by the use of spray at temperature.

Advantages, disadvantages of Benson boiler

There are many benefits of high pressure boilers. Out of them, some benefits are stated below for study,

  • The weight of the Benson boiler is expected less compared to other boilers because there is no drum in the this boiler. The drum is the central part of weight increment. It can reduce about 20% weight of the boiler.
  • As we know that the supercritical pressure is provided to water. The bubble formation is eliminated in this boiler. The water is directly converted into steam because of it.
  • This boiler is considered a lightweight boiler.
  • The maintenance of this boiler can be possible in a smaller floor area. The erection requires less area.
  • The diameter of water tubes in the this boiler is smaller. The benefit of small diameter tubes reduces the chances of explosion.
  • This type of boiler is rapid as it can start in few minutes, around 15 minutes.
  • This boiler is easily transportable compared to other boilers.
  • It is noticed that the thermal efficiency of this boiler is expected about 90%. For any boiler, thermal efficiency states its performance

There are few disadvantages of the boiler.

  • If the flow of water is not proper, the water tube will get overheated. This will affect the working of the boiler.
  • Suppose the water is not pure and contains some impurities. The formation of deposits can be found on the surface of tubes.
  • The operation can face difficulties if the load is variable.

Application of Benson boiler

For any boiler, the initial use is to generate useful steam. The generated steam is utilized for different purposes. Steam is widely used to generate electricity. The steam is being used for process heating in some applications like paper mill, milk pressurization etc. The operating conditions of Benson boiler are as below,

The pressure of steam: 250 bar,

The temperature of steam: 650 degree centigrade,

Output steam rate: 135 – 150 tonnes per hour

Benson boiler drum

It is without a drum.

The weight of the this boiler is expected less compared to other boilers because there is no drum in the this boiler. The drum is the central part of weight increment. It can reduce about 20% weight of the boiler.

Benson boiler features

Because no drum is used in this boiler, the mobility of this boiler parts is not difficult.

Benson boiler function

The function of the boiler is similar to the working of the boiler. The initial use of the boiler is to generate useful steam. How is this steam generated? Here are the answers to this question,

There is no latent heat of vaporization, so the water is directly converted into steam. The intermediate stage of bubble formation is eliminated in this boiler. This prevention of bubble formation is the main benefit of this boiler compared to other average boilers.

We can quickly notice from the figure given in this article,

In the first step,

The feedwater pump  compresses water and circulate it through the system. The feedwater pump raises the pressure at 225 bars. The water is passed through an economizer to absorb waste heat and feed water heating.

Second step

After getting primarily heated by the economizer, the water is getting passed through the radiant heater. In a radiant heater, The water is getting heat by radiation, and the temperature of the water increase such that it partly changes its phase into steam. Its temperature is nearly supercritical.

Third step

This two phase mixer of steam and water is passed through a convective evaporator in the next step. Here in the convective evaporator, the two phase mixer turned into steam. We can consider it as superheated steam to some degree.

Fourth step

In the this boiler, steam from the convective superheater is passed through the superheater to raise its pressure at the required level. This superheated steam is capable of turning a turbine and valuable for electricity generation.

Final step

The turbine is rotated with this superheated steam. The turbine is coupled with an electricity generator. Ultimately, the rotation of the electricity generator produces electricity.

Benson boiler pressure

The operating conditions of Benson boiler are as below,

  • The pressure of steam : 250 bar,
  • The temperature of steam : 650 degree centigrade,
  • Output steam rate : 135 – 150 tonnes per hour

Benson boiler schematic diagram | Benson boiler diagram

The schematic diagram of the Benson boiler is shown below with every part.

Benson high pressure boiler

Yes, It is a higher pressure boiler. It is also considered a supercritical boiler.

Benson point boiler

The design is carried out based on Benson point. The Benson point is the point at which the vertical steam separator should operate dry. The fluid inserted in the boiler should be converted into steam due to this vertical steam separator.

The boiler circulation pump kept off during the Benson point. The water is pressurized with the feedwater pump to meet the required operation of the furnace with the required enthalpy raise. With this method, The function of the evaporator and superheater is controlled according to load. The load on the system will get stabilized.

Define Benson boiler

Mark Benson invented Benson boiler, in year 1922.

It can be known by following,

  • High pressure boiler,
  • Supercritical,
  • Water-tube category,
  • Forced circulation boiler (Water and steam)

This is a supercritical boiler as the feed water is pressurized at supercritical pressure. The reason behind compressing water is to eliminate bubble formation inside the water tube. The appearance of the bubble cannot be possible due to the same density of compressed water and steam.

Efficiency of Benson boiler

It can be said that the thermal efficiency of the Benson boiler is expected about 90%. For any boiler, thermal efficiency states its performance.

FAQ/SHORT Note

What are the major disadvantages of Benson boilers?

There are few disadvantages to the boiler.

If the flow of water is not proper, the water tube will get overheated. This will affect the working of the boiler.

Suppose the water is not pure and contains some impurities. The formation of deposits can be found on the surface of tubes.

The operation can face difficulties if the load is variable.

Benson boiler is drumless

Yes, the Benson boiler is without a drum.

The weight of the this boiler is expected less compared to other boilers because there is no drum in the this boiler. The drum is the central part of weight increment. It can reduce about 20% weight of the boiler.

Maintenance of Benson boiler

The maintenance of the this boiler is already discussed in the design of the Benson boiler topic. Kindly refer to it.