Structure of boiler
Structure of boiler
1、 A boiler consists of two parts: a “pot” and a “furnace”
(1) The basic components of a boiler
1. Boiler
Including drum, tube bundle, water-cooled wall, header, and downcomer. The steam water system in the boiler body transfers heat from the high-temperature combustion product flue gas to the lower temperature water inside the boiler through the heating surface. The water is heated, boiled, and vaporized to generate steam.
2. Stove
Including coal hopper, grate, furnace, slag removal plate, air supply device, etc. The combustion equipment in the boiler body converts the chemical energy of the fuel into thermal energy through combustion.
3. Security attachments
Water level gauges, pressure gauges, safety valves, as well as boiler metal steel frames and platform stairs.
(2) Components of a ‘pot’
1. Economizer
Placed in the vertical flue at the tail of the boiler. Utilizing the waste heat of flue gas to heat boiler feedwater, reducing exhaust gas temperature, improving boiler efficiency, and saving fuel.
2. Steam drum
Located at the top of the boiler. This is a cylindrical pressure vessel with water at the bottom and steam at the top. They form a water circulation loop together. The steam water mixture generated by the heat absorption of water in the water-cooled wall is collected in the steam drum. After the steam water separation, the saturated steam is sent to the superheater.
3. Downward tube
It is the water supply pipeline of the water-cooled wall, which is used to introduce the water in the steam drum into the lower header and redistribute it to various water-cooled wall pipes. There are two types of pipes: small diameter dispersed downcomers and large diameter concentrated downcomers. The diameter of the small-diameter downcomer is small, which is not conducive to water circulation.
4. Lower header of water-cooled wall
The main function of the header is to collect the fluid or redistribute the working fluid through the header to other pipelines. The lower header of the water-cooled wall is a thick tube with closed ends, which connects the downcomer with the water-cooled wall to collect, mix, and redistribute the working fluid.
5. Water-cooled wall
Around the stove. Its main function is to absorb radiation heat and evaporate moisture inside the furnace. It is the main heating surface in modern boilers and can also protect the furnace wall.
6. Superheater
Its function is to heat the saturated steam in the steam drum into superheated steam at a certain temperature.
7. Reheater
Its function is to heat and raise the temperature of the steam that has done some work in the turbine again, and send it into the turbine to continue doing work.
(3) The components of a furnace
1. Furnace
It is converted from furnace walls and water-cooled walls for fuel combustion, and the fuel burns in a suspended state in the space, releasing a large amount of heat.
2. Burner
Place it on the four corners or walls of the stove. Its function is to inject fuel and air into the furnace at a constant speed. The fuel is ignited in a timely manner, burning rapidly and completely. There are two basic types: DC burners and track burners.
3. Air preheater
It is a heat exchanger that exchanges heat between flue gas and air in the combustion system. Air preheaters are generally installed in the tail flue of boilers, using the waste heat of flue gas to heat ambient temperature air, heating the air to the temperature required for fuel combustion, and then sending it into the furnace.
4. Smoke duct
A tube composed of furnace wall, several heat transfer surface tubes, wall tubes, etc., used to guide the flow of flue gas and exchange heat on each heat transfer surface, divided into horizontal flue and tail flue. Auxiliary equipment includes ventilation equipment (supply and induced draft fans), fuel transportation equipment, powder production system, ash and dust removal equipment, desulfurization equipment, etc.