What are the main components of power plant boilers?
Structure and classification Taking coal-fired boiler as an example, the power plant boiler body is composed of furnace, burner, water-cooled wall, superheater, economizer, air preheater and steel frame furnace wall. In addition, there are important auxiliary equipment, such as milling equipment, dust removal equipment, dust removal devices, automatic control devices and instruments, valves, etc. Modern power plant boilers also use industrial televisions and computers. The specific structure of power plant boilers varies with different boilers.
There are many ways to classify power plant boilers. According to the fuel used, there are mainly:
① coal-fired boilers using coal as fuel;
② fuel oil boilers using heavy oil or crude oil as fuel;
③ gas boilers using natural gas or liquefied petroleum gas as fuel. Classified by combustion method, there are layer furnace, chamber furnace, cyclone furnace, boiling combustion boiler (that is, fluidized bed combustion boiler). According to the steam pressure classification:
① medium pressure boiler with a pressure of 2.45 ~ 3.92 MPa;
② high pressure boiler with a pressure of 9.8 MPa;
③ ultra high pressure boiler with a pressure of 12.79 ~ 13.72 MPa;
④ pressure of 16.66 ~ 18.33 MPa Subcritical pressure boiler;
⑤ supercritical pressure boiler with a pressure of 24.1 ～ 26.6 MPa. According to the flow mode of working fluid (water) in the boiler (Figure 1):
① Natural circulation boiler, which flows by the weight difference between the water column in the unheated descending water pipe and the steam-water mixture water column in the heated rising pipe;
② Mandatory Circulation boiler flows by the pressure of the recirculation pump installed in the large-diameter downcomer loop that is not heated;
③ Once-through boiler, feed water is preheated, evaporated, and superheated by the pressure of the feed water pump, and flows through each heating surface of the boiler ;
④ The compound circulation boiler is improved from the once-through boiler, in addition to the feed water pump, it is also equipped with a recirculation pump. When this kind of boiler is below 60 ～ 80% of rated load, it operates in recirculation mode, and above 80% of rated load, it operates in once-through boiler mode. The cycle ratios of several types of pressure boilers are shown in the table. The cycle ratio refers to the ratio of the weight of the circulating steam-water mixture at the outlet of the boiler evaporator tube to the weight of the evaporated steam. Power plant boiler Characteristics and process