Classified by purposePower station boilers: boilers used in thermal power plants with large capacity, high parameters, new technology and strict requirements.

Industrial boilers: boilers that provide steam or hot water in the processes, heating, and refrigeration of textiles, printing and dyeing, pharmaceuticals, chemicals, oil refining, papermaking, etc. in various industries.

Life boilers: boilers that provide low-parameter steam or hot water for industrial and mining, enterprises and institutions, hotels, and service industries. Such boilers are in great demand, and there are many manufacturing plants throughout the country.

Special boilers: such as dual working medium two steam circulating boilers, nuclear fuel, ships, locomotives, waste liquid, waste heat, once-through boilers, etc.

Classified by pressure
Atmospheric pressure boiler (no pressure boiler, that is, a boiler that works under a normal atmospheric pressure)
Low pressure boiler (pressure less than or equal to 2.5MPa)
Medium pressure boiler (pressure less than or equal to 3.9MPa)
High-pressure boiler (pressure less than or equal to 10.0MPa)
Ultra-high pressure boiler (pressure less than or equal to 14.0MPa)
Subcritical boiler (pressure between 17-18MPa)
Supercritical boiler (pressure between 22–25MPa)

According to working fluid type and output status
The working fluid of the steam boiler is water, and the output working fluid is steam. Steam is divided into saturated steam and superheated steam. The working fluid of the hot water boiler is water, and the output working fluid is unsaturated hot water. Special working fluid boilers Boiler working fluids other than water are chemical fluids, such as historical mercury mercury steam boilers.

According to the body structure
The combustion and heat absorption and evaporation of shell-type boilers are all completed in a cylindrical body, which can be divided into horizontal and vertical types, such as the early blue development and fire fighting furnace. The main heating surface of the water tube boiler is a tube boiler, which is a major improvement of the early boiler, and its safety and reliability are greatly improved.
Drum-type boilers and boilers whose drums are placed outside of the fire side are not heated. There are double drums, single drums and multiple drums. The drums have horizontal and vertical installations.

According to the type of fuel or energy
When the boiler burns different fuels, it is called a boiler of that fuel or a mixed-burning boiler of two fuels. Fire bed burning boiler The fuel is placed on the material bed to burn the boiler or grate furnace or layer burning furnace. It is generally lump granular raw coal with the largest capacity. Room-fired boiler fuel is burned in the furnace room or furnace. Generally, there are pulverized coal boilers, oil-fired boilers, gas-fired boilers, etc. The largest capacity of the current generation unit is also called suspended combustion boiler, and there is a semi-suspension between stratified and indoor Burning boilers, such as mechanical stoker, wind stoker boiler, etc.
Cyclone combustion boilers are boilers that burn pulverized coal or fine-grained coal in a cyclone tube. There are two types of boilers: horizontal and vertical. The combustion heat intensity in the cyclone tube is very high. It is suitable for low ash melting point coal and hard-to-ignite coal.
The boiling combustion boiler is placed on the fire bed with granular fuel, and the fuel layer is bounced and boiled into fluidized under the blow of high pressure wind, also known as the fluidized bed boiler.

According to the slagging method
Slag discharge is divided into solid and liquid. It is well known that liquid slag discharges the ash in coal to form a liquid when it is burned at high temperature, and it flows into water to crack into translucent crystals for building materials.

According to the flue gas pressure in the furnace
The pressure of the flue gas from the furnace to the outlet of the negative pressure and slightly positive pressure combustion boiler is lower than the atmospheric pressure, so that the suction force of the induced draft fan is greater than that of the blower to establish a negative pressure system. Conversely, when the air supply pressure of the blower is greater than the suction capacity of the induced draft fan, a slight positive pressure combustion is formed. Slightly positive pressure combustion can reduce the leakage heat loss, but the requirements for the sealing of the boiler are much higher. The pressurized combustion boiler increases the combustion flue gas pressure to several atmospheres. The pressure flue gas is used as the working fluid of the gas turbine to drive the generator to generate electricity or drive the air compressor to obtain higher pressure air as the combustion-supporting medium. Combustion at higher pressure can accelerate the combustion speed And improve the heat transfer effect.

According to the circulation method
The flow circulation of the working fluid in the water wall tube of the natural circulation boiler relies on the specific gravity difference between the ascending and descending tubes to establish the circulation pressure head to produce natural circulation. This kind of boiler is only suitable for subcritical pressure.
Control the auxiliary circulation boiler to add a circulation pump between the water wall and the downcomer to overcome the flow resistance to ensure the safety and reliability of the water circulation. It is suitable for subcritical and near-critical pressure boilers.
The once-through boiler passes from the water to the superheated steam outlet and relies on the pressure of the feed water pump to pass through each heating surface at a time. It is suitable for high pressure above to supercritical pressure.
The combined cycle boiler is equipped with a boiler with a controllable forced recirculation system in the evaporation section of the once-through boiler, so that the water wall can be kept in good operating conditions during low load or during startup, and it will enter pure once-through operation at high load.
The principle of the low-rate circulating boiler is similar to that of the controlled circulating boiler, which promotes the reduction of the circulating ratio of the water wall to about and accelerates the evaporation speed.

According to the overall layout
The overall layout of the boiler is roughly divided into “D” type, “T” type, “π” type, “tower” type and “box” type, etc., and will not be described in detail.

According to the layout of the boiler room
Boilers in open-air layout
Part of the boiler in the semi-outdoor layout is in the open air, and the other part is equipped with simple houses. Indoor layout of boilers The boilers are all in the boiler house.

According to ventilation method
The combustion air of the natural draft boiler is naturally sucked by the induced wind from the chimney, which is used by small boilers.
The resistance of the flue gas system of large boilers with mechanical ventilation balance ventilation is relatively large. The air required for combustion is forced in by the blower, and the combustion flue gas is sucked out by the induced draft fan to maintain the resistance balance of the flue duct.