Definition and Classification of Boiler

A boiler refers to equipment that utilizes the thermal energy released from fuel combustion or other heat sources to heat water or other working fluids, producing steam, hot water, or other working fluids with specified parameters (temperature, pressure) and quality.

As an energy conversion device, the energy input to the boiler can be in the form of chemical energy from fuel, electrical energy, or thermal energy from high-temperature flue gas. After conversion by the boiler, steam, high-temperature water, or organic heat carriers with a certain amount of thermal energy are output. The original meaning of "boiler" refers to a water container heated over a fire, while "furnace" refers to a place where fuel is burned. A boiler consists of both a boiler and a furnace. The hot water or steam generated in the boiler can directly provide the required thermal energy for industrial production and people's lives. It can also be converted into mechanical energy through steam power plants or further converted into electrical energy through generators.

A boiler that provides hot water is called a hot water boiler, mainly used for daily life, with a small amount of application in industrial production. A boiler that produces steam is called a steam boiler, often referred to as a boiler, mostly used in thermal power plants, ships, locomotives, and industrial and mining enterprises.

Overview

A boiler consists of a boiler and a furnace. The water-holding component above is called a boiler, and the heating part below is called a furnace. The integrated design of the boiler and furnace is referred to as a boiler.

According to the "Regulations on Safety Supervision of Special Equipment," a boiler is defined as equipment that uses various fuels, electricity, or other energy sources to heat the contained liquid to certain parameters and output thermal energy.

The scope is defined as a pressure steam boiler with a volume greater than or equal to 30L; a pressure hot water boiler with an outlet water pressure greater than or equal to 0.1MPa (gauge pressure) and a rated power greater than or equal to 0.1Mw; and an organic heat carrier boiler.

Classification: There are many classification methods for boilers, which can be classified according to the purpose of the boiler, the structure of the boiler, the type of fuel, the form of water circulation, and pressure.

1. Classification by boiler purpose:

Boilers can be classified as thermal power boilers and heating boilers. Power boilers include power station boilers, marine boilers, and locomotive boilers, which are used for power generation, marine propulsion, and locomotive propulsion, respectively.

Heating boilers include steam boilers, hot water boilers, heat pipe boilers, hot blast stoves, and heat carrier heating furnaces, which correspondingly obtain steam, hot water, hot air, and heat carriers.

2. Classification by boiler body structure:

According to the boiler structure, it is mainly divided into fire tube boilers and water tube boilers. Fire tube boilers include vertical boilers and horizontal boilers, while water tube boilers include horizontal water tube boilers and vertical water tube boilers.

3. Classification by boiler fuel type:

According to the type of boiler fuel, it is divided into coal-fired boilers, oil-fired boilers, and gas-fired boilers, as well as upgraded technologies for coal-fired boilers, such as pulverized coal boilers and dual-fuel boilers (coal and gas). Coal-fired boilers can be classified into layer-burning boilers, chamber-burning boilers, and fluidized bed boilers according to their combustion methods.

4. Classification by boiler capacity:

Boilers with an evaporation capacity of less than 20t/h are called small boilers, those with an evaporation capacity of more than 75t/h are called large boilers, and those with evaporation capacities between the two are called medium-sized boilers.

5. Classification by boiler pressure: Boilers with a pressure below 2.5MPa are called low-pressure boilers, those above 6.0MPa are called high-pressure boilers, and those with pressures between the two are called medium-pressure boilers. In addition, there are ultra-high pressure boilers, subcritical boilers, and supercritical boilers.

6. Classification by boiler water circulation form:

Boilers can be classified into natural circulation boilers and forced circulation boilers (including once-through boilers) according to the water circulation form.

7. Classification by device form:

It can be divided into quick-assembly boilers, assembled boilers, and bulk boilers. In addition, there are forms such as wall-mounted boilers, vacuum boilers, and modular boilers.

8. Classification by flue gas flow:

Water tube boilers, shell boilers (fire tube boilers), and water-fire tube combination boilers.

9. Classification by drum placement:

Vertical boilers and horizontal boilers.

10. Classification by the number of drums:

Single-drum boilers and double-drum boilers.

11. Classification by purpose:

Household boilers, industrial boilers, power station boilers, and marine and vehicle boilers.

12. Classification by medium:

Steam boilers, hot water boilers, steam and water boilers, and organic heat carrier boilers.

13. Classification by installation method:

Quick-assembly boilers, assembled boilers, and bulk boilers.

14. Classification by water circulation:

Natural circulation, forced circulation, once-through boilers, and combined circulation.

15. Classification by pressure:

Atmospheric boilers, low-pressure boilers, medium-pressure boilers, high-pressure boilers, and ultra-high-pressure boilers.

16. Classification by combustion:

Internal combustion boilers and external combustion boilers.

17. Classification by manufacturing level:

Steam pressure is classified as low-pressure boilers (P < 2.45MPa), medium-pressure boilers (3.8 < P < 5.8MPa), high-pressure boilers (5.9 < P = 12.6MPa), ultra-high-pressure boilers (12.7 < P = 15.8MPa), subcritical boilers (15.9 < P = 18.3MPa), supercritical boilers (22.115 < P < 30MPa), and ultra-supercritical boilers (> 30MPa).