The function of the boiler is to convert the chemical energy of the fuel into heat energy, and use heat energy to heat the water in the boiler to make it superheated steam with sufficient quantity and certain quality (steam temperature and pressure) for use by the steam turbine. Currently, boilers in thermal power plants have large capacity, high parameters, complex technology, and high levels of mechanization and automation. Therefore, the fuel is mainly coal, and coal is first made into pulverized coal before combustion, and then sent to the boiler for combustion and heat release in the furnace. To sum up, the main working processes of a boiler are fuel combustion, heat transfer, water heating and vaporization, and steam overheating.

The entire boiler consists of two parts: the boiler body and auxiliary equipment. Let me briefly introduce their composition.

Boiler body:

The boiler body is the main part of the boiler equipment, which is composed of two parts: "boiler" and "furnace". "The boiler" is a steam-water system whose main task is to attract the heat released from the fuel, heat, evaporate, and transform the water into superheated steam with certain parameters. It consists of equipment such as economizers, steam drums, downcomers, headers, water cooled walls, superheaters, reheaters, and their connecting pipes and valves.

"Furnace" is a combustion system whose task is to make fuel burn well in the furnace and emit heat. It consists of a furnace, a burner, an ignition device, an air preheater, smoke and air ducts, furnace walls, and a framework.

(1) Furnace. It is converted from furnace walls and water cooled walls for fuel combustion. The fuel is combusted in a suspended state in this space, releasing a large amount of heat.

(2) Burner. Located on the four corners or walls of the furnace, its function is to inject fuel and air into the furnace at a certain speed to ensure a good mixing in the furnace to ensure timely ignition and rapid and complete combustion of the fuel. There are two basic types of direct flow burners and swirl burners.

(3) Air preheater. Located at the tail flue of the boiler, its function is to heat the air required for fuel combustion using the residual heat of flue gas, which not only can further reduce the exhaust gas temperature, but also is beneficial for enhancing combustion in the furnace, improving combustion economy, drying, and conveying pulverized coal. The boiler efficiency can be improved by about 2%. There are two types of split pipe and rotary type.

(4) Smoke and air duct. It is a pipe composed of furnace walls, some heating surface pipes, and wrapped wall pipes, which is used to guide the flow of flue gas and conduct heat exchange through various heating surfaces. It is divided into horizontal flue and tail flue.

auxiliary equipment

Auxiliary equipment includes ventilation equipment (forced and induced draft fans), fuel transportation equipment, pulverizing system, ash and dust removal equipment, desulfurization equipment, etc.

Workflow of power station boiler

When the electric boiler reaches the heat storage period, the water make-up electric valve will be opened, and the heat storage tank will start to replenish water. When the water level reaches a predetermined high level, the water make-up electric valve can be closed by itself. When the temperature of the heat storage tank reaches the preset temperature or the heat storage period ends, the electric boiler stops working. After one minute, the circulating booster pump starts to stop operating, and the circulating booster pump operates at the set frequency. After 30 seconds, the electric boiler starts operating, and heat storage begins.

Open the water supply electric valve, close the heat storage electric valve, start the circulating booster pump to supply water in a frequency conversion, speed regulation, and constant pressure manner. After about 30 seconds, start the electric boiler to supply water to the user in a direct supply manner. At the end of water supply, stop the circulating booster pump first, and then stop the electric boiler 60 seconds later. When the water supply period is reached, the electric boiler water supply electric valve is opened, the heat storage electric valve is closed, and the electric boiler does not work. The circulating booster pump provides water at constant pressure through frequency conversion and speed regulation. During the water supply period of the electric boiler, the water make-up electric valve is always closed and no water make-up operation is performed to avoid supplying cold water to the user. If during the heat storage period and the temperature of the heat storage tank is lower than the set temperature of 5 ° C, the circulating booster pump is put into operation again, and 30 seconds later, the electric boiler starts working.

The above is the working principle of power station boilers, which you can learn more about.