In this article, I will share the type, requirements and working principle of a pulverized fuel burner.
It’s called pulverized fuel burner because it burns fuel that has been crushed into powder.
The coal that is supposed to be used in a burner is first crushed by a rolling action and then blown to the burner.
I will share more about the working principle of this fuel burner later on in this article.
Before you know the types of pulverized fuel burners, let me share with you some of the components of a pulverized fuel burner.
Main components of the pulverized fuel burner
1. The pulverizer.
Pulverizer is the component that crashes the coal when before it’s fed into the burner.
It’s in the pulverizer where the coal is also dried by hot air as it’s being crashed.
2. Primary air fan.
The primary air fan is used to blow the pulverized coal to the burner.
It’s hard for the powdered coal to reach the burner at the required speed without the help of the fan.
The fan is installed between the pulverizer and the burner.
3. Burner with adjustable length.
It’s in the burner where the coal is burned to produce the heat needed in the boiler.
The burner has a nozzle at the outlet to enhance the pressure at which the flames go out to the furnace.
4. Pipework.
Pipework is needed to help convey the pulverized coal from the pulverizer to the burner.
It’s important that the coal is conveyed in closed tubes to ensure that it’s not wasted by wind since it’s in powder form.
Types of pulverized fuel burners.
1. Streamlined pulverized fuel burner.
The other names of this burner are Long-flame and U-flame pulverized burner.
It’s called a long flame or since the flame has to travel to a certain distance, to get sufficient air for it to burn the fuel completely.
This type of burner is used with fuel that has poor combustion properties.
2. Turbulent pulverized fuel burner.
A turbulent pulverized fuel burner is also called a short flame burner.
The name suggests that this type of burner produces a short flame which is very hot.
It mixes the coal with plenty of air which makes the combustion to be complete.
The coal enters the burner with a mixture of primary air and then before it’s fed into the furnace it’s mixed again with secondary air.
3. Tangential pulverized fuel burner.
The tangential burner is designed in a square manner in such a way that the burners are installed at each corner of the square.
This means it has four burners that all direct flame at the centre point of the square (which is the furnace).
There is a great mixture of air and fuel at the centre of the furnace which results in a high rate of energy being produced.
4. Cyclonic pulverized fuel burner.
Cyclone burner has a cyclone cylinder that receives the coal before supplying it to the furnace.
It’s in the cyclone cylinder where the secondary air is added and mixed with the coal.
The secondary air is preheated and supplied under pressure to ensure that the coal mixes sufficiently with the air to provide complete combustion.
Cyclonic pulverized burners can burn low-grade fuels because the preheated air supplied is of very high temperature (about 20000C) and the fuel is supplied by a force draught fan (which adds up on the air used for combustion).
Requirements of the pulverized fuel burners
1. Thorough mixing of the fuel with air.
For the pulverized fuel burner to be effective this is one of the requirements it should fulfil.
The pulverized fuel burner should be able to mix the fuel with the primary air thoroughly before injecting the mixture into the furnace.
This is to ensure that the fuel burns completely due to sufficient air in the furnace.
There is a very big chance that the fuel in the furnace will not burn properly if there is a limited supply of air.
Since the fuel will be pulverized when entering the burner the air won’t flow easily through it unless an action of mixing it with the primary air happens.
We all know that without enough air in the furnace, the combustion won’t be sufficient enough to produce the heat needed to heat the water in the boiler.
2. Proper turbulence.
Pulverized fuel burner should create proper turbulence to ensure that there is stable combustion going on.
Stable combustion is necessary to produce enough heat as long as the boiler needs it.
This is an important requirement of the pulverized fuel burner one should consider before putting it into use.
Stable combustion is essential since it saves fuel and the steam produced is going to be of higher pressure.
Unstable combustion on the other hand will not be effective for high-pressure steam production.
And this is going to slow down the processes that require high-pressure steam for them to work.
3. Flame shape should be controllable.
Another requirement of the pulverized burner should be this; it should be able to control the shape of the flame produced by the burner.
If the burner can’t control the shape of the flame produced then it’s not effective to be used.
Controlling the shape of the flame helps in controlling the amount of heat produced.
This is a very important factor, especially when trying to control the steam production from the boiler.
4. It should be able to avoid flashbacks.
The flashback in the pulverized fuel burner should be avoided at all costs.
This is a requirement that the pulverized fuel burner should ensure that it fulfils.
The pulverized fuel burner should be able to move the coal air mixture away from the burner at a rate equal to the flame to avoid flashback.
5. Proper projection.
The orientation of the pulverized fuel burner is another requirement that should be taken into consideration.
The pulverized fuel burner should be projected the right way so as to prevent overheating, wear and internal flames.
The angle at which the pulverized fuel burner should be oriented, it should allow the burner to release the flame without heating other parts of the burner.
The wrong projection of the pulverized fuel burner will result in a waste of heat and the life of the burner will be shortened.
Working principle of pulverized fuel burner.
The raw fuel is first fed into the pulverizer where it’s crashed down and hot air is fed into the pulverizer to dry the coal.
The hot air can be from the burner (bleed air) or it can even be from the air preheaters.
You might like this: Air Preheaters in Steam Boilers: Function, Types and Working Principles
It’s necessary to crash the coal into powder form to make it easy for the fan to blow it to the burner.
After the coal has been crashed and dried it’s taken to the primary air fan where it will be blown to the blown burner.
The fan also aids in mixing the air with the coal to ensure that complete combustion will be facilitated in the boiler.
The burner after receiving the pulverized coal from the fan also mixes the powdered coal in the air suspension with additional preheated combustion air (secondary air) and forces it out through the nozzle.
The action of mixing the powdered coal with preheated combustion air is to ensure stable combustion is achieved to produce enough heat needed to heat the water in the boiler.
Final thoughts
This is the summary of pulverized fuel burner. There is still much to learn about pulverized fuel burners.
There is the design factor, advantages and disadvantages and efficiency of this burner compared to other like rotary cup oil burner.
That will be a topic to talk about in the future.
If you have any questions about what I have shared in this article, don’t be afraid to leave a comment.
Thanks for reading the article, see you in my next article.
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