Combustion System of Steam Boiler

Combustion is the name given to the chemical reaction between fuel and oxygen which results in the production of heat. The oxygen is usually derived from the air, which unites chemically with the carbon, hydrogen, and a few minor elements in the fuel to produce heat. A steam boiler designer and operator should understand the fundamental principle of combustion process to assure satisfactory service and high efficiency.

Combustion of steam boiler will not start in air or be maintained below a certain temperature, known as the ignition temperature. Once the fuel is ignited, it must supply sufficient heat to raise the temperature and establish continuous combustion. Thus the three requirements for combustion to be established are fuel, temperature/heat and air.

The combustion process of steam boiler should consider as follow:
1.            Control of air supply
The amount of air required depends upon the fuel, the equipment used for combustion. It is important that the best proportion of air to fuel be determined and maintained in order to obtain the highest efficiency possible. Too much air results in excessive release of hot gases from the stack with a correspondingly high heat loss and reduction in efficiency.
If therefore exactly the right amount of air is provided to burn the fuel completely, the waste gases will only contain CO2, steam, SO2, and N2. The CO2 content will be less than 21% for burning pure carbon completely. 

2.            Mixing of air and fuel
Air and fuel must be thoroughly mixed since each combustible particle must come into intimate contact with oxygen contained in the air before combustion can take place. Combustion steam boiler equipment is designed to obtain the best possible mixing of fuel and air.

3.            Temperature required for combustion
Combustion will start in certain temperature to accelerate oxidation. Operator steam boiler should maintain the air and fuel mixture at a temperature sufficiently high to promote combustion

4.            Time required for combustion
An appreciable amount of time is required to complete the process of combustion of steam boiler. Fuel and air should have enough time to permit complete combustion, if equipment of steam boiler is operated at excessively high ratings, the time may be insufficient to permit complete combustion.


agil said...

Pak guru tolong dibahas proses first firing yang ideal donk...

taufik said...

In the case of new boiler, first firing ideally should be done with requirements as follow:
1. All of equipments that are required for combustion or firing process must be ready
a. Air system must be ready: ID Fan, FD Fan, and SA Fan are ready to use include backfeeding power
b. Fuel system must be ready: supply coal, coal conveyor, coal crusher, coal yard, etc must be perfectly installed.
c. Water treatment system must be ready because water should be suitable for boiler; water treatment plant should be ready to use.
2. Steam will be generated should ready to be distributed to steam blow process.
3. Discharge ash system should be ready: ash submergible conveyor, cooling tower, etc.
4. Interlock instrument system for safety must be ready, such us if low level of water in steam drum occurs, boiler should be shut down, etc
5. If all of equipments above are intalled, first firing can be done.