CFB steam boiler

6. What is heat inequality? How did it come about?

Thermal unevenness is the phenomenon of uneven heat load in the same heating surface tube group. Thermal inhomogeneities can be caused both by structural characteristics and by operating conditions. For example, the uneven distribution of smoke temperature along the width of the flue gas and the phenomenon of uneven smoke speed; the flue gas corridor of the serpentine pipe on the heated surface caused by uneven or uneven spacing; the dust accumulation on the heated surface, slagging, and the flame center deflection of the furnace; Poor operation adjustment causes the flame to deflect, move down, raise, and cause uneven heat.

(l) Ensure that the steam parameters are rated and stable.

(2) to ensure that the fire is stable, the appropriate combustion center, the flame distribution, do not burn equipment, to avoid coking ash.

(3) Safe operation of boilers and units under the most economic conditions.

7. What is the boiler's heat storage capacity? What is the size of heat storage capacity?

When the external load changes and the boiler combustion conditions do not change, the ability of the boiler working medium, heating surface, and furnace wall to release or absorb heat is called the boiler's heat storage capacity.

The size of the heat storage capacity mainly depends on the working water volume of the boiler and the amount of metal on the heating surface, and is related to the steam pressure of the boiler. That is, the larger the working water volume, the greater the amount of metal on the heated surface, and the lower the steam pressure, the greater the heat storage capacity of the boiler. For boilers with heavy furnace walls, the heat storage is also related to the furnace wall.

8. How does the boiler's heat storage capacity affect the operation regulation?

When the external load changes, the temperature and heat of the working fluid and the metal in the boiler must change. If the load increases and the vapor pressure is reduced when the combustion is adjusted in time, the corresponding saturation temperature decreases, and the liquid heat of the pan water decreases accordingly. At this time, the pan water and the heat stored in the metal will cause some of the pan water to vaporize into steam. The generation of these additional evaporations can serve to slow down the drop in steam pressure. Therefore, the greater the heat storage capacity, the slower the decrease in the vapor pressure. Contrary to this, when the combustion conditions do not change and the load decreases, the vapor pressure rises. As the saturation temperature increases, the working fluid and metal store a part of the heat, which slows the rise of the vapor pressure. Therefore, the thermal storage capacity of the boiler is beneficial to the stability of the operating parameters. However, when the boiler regulation needs to actively change the operating conditions to change the combustion rate, the load, pressure, and temperature of the boiler are changed slowly due to the heat storage capacity, and the requirements of the working conditions cannot be quickly adapted.

9. What is the role of primary, secondary, and tertiary winds?

For pulverized coal furnaces, the role of primary air is mainly to transport pulverized coal to the furnace through the burner, and to supply the oxygen needed for the combustion of the volatiles in the pulverized coal, and to use the hot air to supply the primary air. The role of pulverized coal preheating.

The role of secondary air is to supply the amount of oxygen required for complete combustion of fuel, and to enable air and fuel to be fully mixed, and the combustion of the secondary air is rapid, intense and complete.

The third air is the dry wind discharged from the pulverizing system, commonly known as the lack of gas. It is used as a medium for conveying pulverized coal and is called primary air when powder is delivered. It is called tertiary air only when it is sent to the hearth with a separate nozzle. The tertiary wind contains little pulverized coal and has a high wind speed. It has a strong mixing effect on the pulverized coal combustion process and supplements the oxygen required for the burnout stage. Because of its low wind temperature and high water vapor content, it has the effect of reducing the furnace temperature.

10. What is hot air feeding? What are the characteristics?

The hot air at the outlet of the air preheater is used as the method for conveying coal powder to enter the furnace and is called hot air feeding.

The hot blast powder can make the pulverized coal preheated in the air duct, which is conducive to the precipitation of volatile matter and the timely ignition and stable combustion in the furnace. However, for coal with high volatile content, hot blast powder should not be used to prevent the pulverized coal from burning prematurely and burning the burner.