1. What is a boiler?

　　A boiler is a device that converts other thermal energy into the thermal energy of other working fluids to produce working fluids with specified parameters and quality.

　　In boiler equipment, the heat-absorbing part is called the "pot," and the part that generates heat is called the "furnace." For example, the heat-absorbing parts such as water walls, superheaters, and economizers can be considered as the "pot"; while the furnace, burner, fuel pump, and induced draft fan can be considered as the "furnace."

　　Modern boilers are not as clearly divided into pots and furnaces as those used in ordinary households. For example, an air preheater is both a heat-absorbing part and a heat-generating part; it can be considered as part of both the pot and the furnace.

　　2. How are boilers classified?

　　Boilers can be classified in different ways:

　　① According to the fuel used, boilers can be classified into: coal-fired boilers, oil-fired boilers, and gas-fired boilers.

　　② According to the combustion method, they can be classified into: layer combustion boilers, chamber combustion boilers, and fluidized bed boilers (between the two).

　　③ According to the boiler water circulation method, they can be classified into: natural circulation boilers, forced circulation boilers, and combined circulation boilers.

　　④ According to whether there is a steam drum, they can be classified into: drum boilers and once-through boilers.

　　⑤ According to steam pressure, they can be classified into: low-pressure boilers, medium-pressure boilers, subcritical pressure boilers, high-pressure boilers, ultra-high-pressure boilers, subcritical pressure boilers, and supercritical pressure boilers.

　　⑥ According to whether water or flue gas passes through the tubes, they can be classified into: fire-tube boilers, water-tube boilers, and water-fire tube combined boilers.

　　⑦ According to the purpose of the boiler, they are classified into: domestic boilers, industrial boilers, power plant boilers, and hot water boilers.

　　3. What is a fire-tube boiler?

　　A fire-tube boiler is one in which the flue gas produced after fuel combustion flows through the fire tube or flue tube, heating the water, steam, or steam-water mixture outside the fire tube or flue tube.

　　4. What is a water-tube boiler?

　　A water-tube boiler is one in which water, steam, or a steam-water mixture flows inside the tubes, while the flame or flue gas burns and flows outside the tubes.

　　5. What is a circulating fluidized bed boiler?

　　A circulating fluidized bed boiler is a new type of boiler improved and developed based on the fluidized bed boiler (also known as a bubbling bed or boiling bed boiler). The circulating fluidized bed boiler retains all the advantages of the fluidized bed boiler while avoiding and eliminating

　　the disadvantages of low thermal efficiency, serious wear and tear of buried tubes, insufficient utilization of desulfurization agent limestone, high consumption, and difficulty in large-scale production of fluidized bed boilers.

　　The bed material in a circulating fluidized bed boiler is in a fluidized state, which is the same as that in a fluidized bed boiler. The main difference between the former and the latter is that the former has a higher fluidization velocity, and the concentration of materials in the flue gas at the furnace outlet is very high. A large amount of material is

　　separated by the material separator at the furnace outlet and returned to the furnace, that is, a large amount of material circulates between the furnace and the material separator.

　　Commonly used boiler terminology explanation

　　6. Steam boiler

　　A steam boiler is a device that uses thermal energy to heat water (working fluid) to produce steam. It consists of two parts: a pot and a furnace. The pot is the heat receiving surface system of the boiler that receives heat and transfers it to the working fluid; the furnace is the space in the boiler where the chemical energy of the fuel is converted into

　　thermal energy and the channel for flue gas flow. The capacity of a boiler is usually expressed in "ton/hour" or "t/h". The rated pressure of a boiler is expressed in "Mpa" or "megapascals" (old units use "kgf/cm2"), and the temperature of saturated steam and superheated steam at rated pressure is expressed in "°C" (Celsius).

　　7. Hot water boiler

　　Refers to a boiler whose heat transfer medium is hot water. The capacity of the boiler is usually expressed in "MW" (megawatts), and the old unit uses "ten thousand kilowatts/hour" or "ten thousand kilocalories/hour", i.e., "104kcal/h". The rated pressure of the boiler is expressed in "Mpa", and the hot water temperature is expressed in "C".

　　Hot water boilers are mainly used for northern heating and are divided into high-temperature hot water boilers (water temperature is 130°C or higher) and low-temperature hot water boilers (water temperature is below 95°C). In the past, low-temperature hot water boilers were mostly used, but in the future, high-temperature hot water boilers will be developed. Hot water boilers have two types: natural circulation and forced circulation. Our company's horizontal three-pass shell hot water boiler is natural circulation.

　　B. Organic heat carrier furnace

　　Refers to a new type of thermal energy conversion equipment whose heat transfer medium is high-temperature heat transfer oil (also known as heat carrier). It is also usually expressed in "MW" (megawatts), and the old unit also uses "ten thousand kilowatts/hour" or "ten thousand kilocalories/hour", i.e.,

　　"104kcal/h". The advantages of organic heat carrier furnaces (also known as heat transfer oil furnaces) are "high temperature and low pressure", stable operation, and are widely used. Organic heat carrier furnaces are divided into liquid phase and gas phase. Our company's organic heat carrier furnace is liquid phase.

　　9. Boiler capacity

　　Refers to the ability of a steam boiler, hot water boiler, or organic heat carrier furnace to provide thermal energy. The larger the capacity, the greater the heating capacity and output; conversely, the smaller the capacity.

　　For example, a 1t/h steam boiler means that the boiler can convert 1 ton of water into saturated steam at a certain pressure within 1 hour; a 0.7 MW hot water boiler and organic heat carrier furnace means that it can produce heat equivalent to 0.7 MW of power (equivalent to the heat of 1 ton of steam) within 1 hour.

　　10. Boiler heating surface

　　This usually refers to the surface area of metal in contact with flames or flue gas on one side (the other side is in contact with water or heat transfer oil). The heat exchange of a boiler is carried out through such a metal surface area. It is generally measured in square meters (m2), and is referred to as the heating surface area.

　　A larger heating surface area means a larger boiler capacity, and vice versa.

　　11. Temperature

　　This is a state parameter that indicates the degree of hotness or coldness of an object, generally expressed in "°C" (degrees Celsius). In the past, "°F" (degrees Fahrenheit) was commonly used in the US and UK. The boiling point of water is 100°C, which converts to 212°F.

　　12. Boiler Pressure

　　In the boiler industry, the boiler pressure (pressure) usually refers to the force perpendicular to the unit wall area of a container, expressed in "Mpa". The old unit was "kgf/cm2" (kilogram-force/square centimeter).

　　13. Saturated Steam

　　The water in the boiler boils and vaporizes into steam when heated by the heat released from the combustion of fuel under a certain pressure. The temperature of the boiler water in this boiling state is the saturated steam temperature; the higher the pressure in the boiler, the higher the saturated steam temperature. For example,

　　1.0 Mpa saturated steam temperature 184°C, 1.25 Mpa saturated steam temperature 193°C.

　　14. Superheated Steam

　　Steam with a temperature higher than the saturation temperature at the corresponding pressure is called superheated steam. Superheated steam has high enthalpy and entropy, and therefore a greater ability to do work. When used as a heat source with the same mass as saturated steam, it can raise the temperature of the heated medium higher, and when fed into a steam turbine generator, it can generate more electricity.

　　The temperature will rise higher, and more electricity can be generated when fed into a steam turbine generator.

　　15. Boiler Thermal Efficiency

　　This refers to the percentage of the heat absorbed by water, steam, or heat transfer oil during the heat exchange process in a boiler or organic heat carrier furnace, relative to the heat released by the complete combustion of the fuel entering the boiler.

　　Heat absorbed by the boiler (effectively utilized heat)

　　Heat released by the complete combustion of fuel