The working principle of the boiler

Environmental protection boiler parameters are the main indicators of boiler performance, including boiler capacity, steam pressure, steam temperature, feed water temperature, etc.

The boiler capacity can be expressed by the rated evaporation capacity or the maximum continuous evaporation capacity. The rated evaporation capacity is the amount of steam continuously produced per unit time under the specified outlet pressure, temperature and efficiency. The maximum continuous evaporation is the maximum continuous production of steam per unit time under the specified outlet pressure and temperature.

Steam parameters include the steam pressure and temperature of the boiler, usually referring to the superheated steam pressure and temperature at the outlet of the superheater and reheater. If there is no superheater and reheater, it refers to the saturated steam pressure and temperature at the outlet of the boiler. The feed water temperature refers to the inlet water temperature of the economizer. When there is no economizer, it refers to the inlet water temperature of the drum.

Environmental protection boilers can be classified according to different methods. Boilers can be divided into industrial boilers, power station boilers, marine boilers and locomotive boilers according to their purpose; according to the outlet pressure of the boiler, they can be divided into low pressure, medium pressure, high pressure, ultra high pressure, subcritical pressure, supercritical pressure and other boilers; The flow path of flue gas can be divided into fire tube boilers, fire tube boilers and water tube boilers. The fire tube boilers and fire tube boilers are also called shell boilers. According to the circulation mode, they can be divided into natural circulation boilers and auxiliary circulation boilers (ie forced circulation). Boilers), once-through boilers and combined circulation boilers; according to the combustion method, boilers are divided into chamber-fired furnaces, layer-fired furnaces and boiling furnaces.

In the water vapor system, the feed water is heated to a certain temperature in the heater, and then enters the economizer through the water supply pipe, and is further heated and then sent to the drum, mixed with the boiler water, and descended to the water wall inlet header after being mixed with the boiler water. The water absorbs the radiant heat of the furnace in the water wall tube to form a steam-water mixture through the riser pipe to reach the drum, and the steam-water separation device separates the water and steam. The separated saturated steam flows from the upper part of the drum to the superheater, and continues to absorb heat to become superheated steam of a certain temperature (currently, the main steam temperature of most 300MW and 600MW units is about 540℃), and then sent to the steam turbine.

In the combustion and flue gas system, the blower sends air into the air preheater to heat it to a certain temperature. The pulverized coal, which is ground to a certain fineness in the coal mill, is carried by a part of the hot air from the air preheater and injected into the furnace through the burner. The pulverized coal and air mixture sprayed by the burner is mixed and burned with the rest of the hot air in the furnace, releasing a lot of heat. The hot flue gas after combustion flows through the furnace, slag tube bundle, superheater, economizer and air preheater in sequence, and then passes through the dust removal device to remove the fly ash, and finally is sent to the chimney by the induced draft fan to be discharged to the atmosphere.

The nature of scale varies with the type of scale. The thermal conductivity and hardness of the scale have a great impact on the boiler's physical properties. The thermal conductivity of scale is a coefficient indicating how fast the scale conducts heat, which directly affects the heat transfer effect and metal of the boiler. The wall temperature affects the safety and economy of the boiler; the hardness of the scale refers to the hardness of the scale, which is related to whether the boiler is easy to remove after scaling, whether it takes a high price to remove the scale, whether it damages the boiler, and is safe for the boiler Economic operations also have an important impact.