The boiler and steam turbine, the two major main engines in the power plant, have different emphases in the operation process. The boiler focuses on regulation, and the steam turbine focuses on monitoring. Whether the boiler burns well or not will directly affect the power generation of the power plant. It is no surprise that 300MW generating units participate in peak regulation. During peak regulation, the minimum load is only 130MW, the load rate is low, and the economy is poor. The combustion of the boiler is unstable at low load, and it is easy to flame out. Calculated according to the power loss of 90,000 kW·h and fuel consumption of 3 to 4 tons each time the flame is turned off, the direct economic loss is 40,000 yuan. The service life of the equipment is reduced, and at the same time, it greatly affects the safe operation of the power grid.
the
A power plant boiler is a 1025t/h forced circulation drum furnace produced by Harbin Boiler Factory, a positive pressure direct-blowing pulverizing system, equipped with five sets of MPS coal mills, and an equal air distribution DC burner. When the plant is running at low load, the main reasons for the flameout are unstable combustion, equipment defects, coal failure, and improper handling. The following countermeasures can be formulated for the main reasons for flameout:
1. The operating personnel should keep abreast of the coal quality at any time, especially pay attention to the volatile matter content and the fineness of the coal powder. The fineness of the coal powder should not be too large. If it is found to be too large, the opening of the mill outlet should be adjusted to minimize the mill air volume. , to reduce the wind speed once. While doing a good job in the medium test, the coal blending work should be done well, and the coal blending situation should be connected with the centralized control to prevent coal failure during low-load operation. Under the premise of ensuring a sufficiently high steam temperature, try to use the lower layer pulverizing system to operate, and try not to operate in separate layers. For general coal quality, use B, C, D three-layer pulverizing system to operate.
2. When the load is low, the swing angle of the burner should not be lifted up, but should be kept horizontal or slightly downward, and can be switched to manual control. Prevent the center of the flame from rising, the diameter of the inscribed circle in the furnace decreases, and the fullness becomes poor. It is best not to adjust the swing angle of the burner frequently. Because the swing angle is not adjusted, it will easily cause disturbance in the furnace and cause flameout. The air volume, negative pressure, and auxiliary wind baffles should be adjusted carefully, and can be switched to manual control.
3. Since the negative pressure adjustment of the boiler is operated by the inlet baffle of the centrifugal induced draft fan, the adjustment performance becomes poor between 30% and 40% of the stroke, and it is easy to get stuck. Poor interference ability, easy to flameout. If the negative pressure is kept low and unstable, it should be switched to manual adjustment.
4. Pay close attention to the change of oxygen content, which is the most important parameter to reflect the combustion, especially when the coal quality deteriorates, the oxygen content rises rapidly. Generally, the amount of oxygen should be controlled at 4% to 6%. Closely monitor the operation of the pulverizing system, such as whether the coal feeder is broken, slipped, deviated, and blocked; whether the hot and cold air baffles are stuck; whether the air powder pipe is blocked; When it is found that the combustion is unstable, add oil in time to stabilize the combustion; increase the outlet temperature of the pulverized coal mill to make the pulverized coal easier to catch fire.
5. Increase the primary and secondary air temperature. When the temperature is low, you can turn on the primary and secondary air hot air recirculation, and try to automatically control the gap between the fan-shaped plates of the air preheater. When the load is high, the soot blowing of the water wall and horizontal flue should be strengthened to prevent the large pieces of coke from falling and affecting the combustion when the load is low. Pay attention to the operation of the furnace body, such as: water seal at the bottom, whether the soot blower is stuck, the condition of each heating surface, and whether the fire holes are all closed to prevent cold air from leaking into the furnace.
6. The principle of air distribution
The principle of air distribution is to ensure ignition stability and complete combustion. For the once-through burner with equal air distribution, the mixing time of the primary and secondary air is early, which is suitable for bituminous coal and lignite with relatively high volatile content, because the volatile content of the combustible base of the coal used in this plant is 16% to 20% (the design is 33%) , basically belong to lean coal. When the coal quality is poor or suddenly deteriorates, the combustion should be adjusted in time, especially at the low load stage, attention should be paid to:
(1) The primary wind speed and wind pressure should not be too high or too low. The air volume of the pulverized coal mill is low under the premise of ensuring that the mill is not blocked, so as to increase the flue gas temperature and coal powder concentration near the burner, and improve the ignition stability.
(2) The auxiliary air baffle between adjacent running mills should be relatively closed, and the upper secondary air should be opened larger, using an inverted pagoda for air distribution, similar to graded air distribution burners, so that the secondary air can mix with the flue gas later , stable combustion.
(3) Due to the late mixing of the secondary air and the primary air, the secondary air is required to have sufficient momentum to penetrate the high-temperature flue gas and contact with the coke particles. A higher differential pressure of the secondary air box and the furnace should be ensured. The worse the coal quality, The differential pressure should be higher.
(4) When the load is low, the fuel air should be turned down as much as possible, which can increase the concentration of pulverized coal and reduce the amount of cold air at the initial stage of combustion, especially for coals with low volatile content. Using the above method to adjust the running combustion can significantly reduce the number of flameouts, save fuel and improve the economy of unit operation.
The boiler and steam turbine, the two major main engines in the power plant, have different emphases in the operation process. The boiler focuses on regulation, and the steam turbine focuses on monitoring. Whether the boiler burns well or not will directly affect the power generation of the power plant. It is no surprise that 300MW generating units participate in peak regulation. During peak regulation, the minimum load is only 130MW, the load rate is low, and the economy is poor. The combustion of the boiler is unstable at low load, and it is easy to flame out. Calculated according to the power loss of 90,000 kW·h and fuel consumption of 3 to 4 tons each time the flame is turned off, the direct economic loss is 40,000 yuan. The service life of the equipment is reduced, and at the same time, it greatly affects the safe operation of the power grid.
the
A power plant boiler is a 1025t/h forced circulation drum furnace produced by Harbin Boiler Factory, a positive pressure direct-blowing pulverizing system, equipped with five sets of MPS coal mills, and an equal air distribution DC burner. When the plant is running at low load, the main reasons for the flameout are unstable combustion, equipment defects, coal failure, and improper handling. The following countermeasures can be formulated for the main reasons for flameout:
1. The operating personnel should keep abreast of the coal quality at any time, especially pay attention to the volatile matter content and the fineness of the coal powder. The fineness of the coal powder should not be too large. If it is found to be too large, the opening of the mill outlet should be adjusted to minimize the mill air volume. , to reduce the wind speed once. While doing a good job in the medium test, the coal blending work should be done well, and the coal blending situation should be connected with the centralized control to prevent coal failure during low-load operation. Under the premise of ensuring a sufficiently high steam temperature, try to use the lower layer pulverizing system to operate, and try not to operate in separate layers. For general coal quality, use B, C, D three-layer pulverizing system to operate.
2. When the load is low, the swing angle of the burner should not be lifted up, but should be kept horizontal or slightly downward, and can be switched to manual control. Prevent the center of the flame from rising, the diameter of the inscribed circle in the furnace decreases, and the fullness becomes poor. It is best not to adjust the swing angle of the burner frequently. Because the swing angle is not adjusted, it will easily cause disturbance in the furnace and cause flameout. The air volume, negative pressure, and auxiliary wind baffles should be adjusted carefully, and can be switched to manual control.
3. Since the negative pressure adjustment of the boiler is operated by the inlet baffle of the centrifugal induced draft fan, the adjustment performance becomes poor between 30% and 40% of the stroke, and it is easy to get stuck. Poor interference ability, easy to flameout. If the negative pressure is kept low and unstable, it should be switched to manual adjustment.
4. Pay close attention to the change of oxygen content, which is the most important parameter to reflect the combustion, especially when the coal quality deteriorates, the oxygen content rises rapidly. Generally, the amount of oxygen should be controlled at 4% to 6%. Closely monitor the operation of the pulverizing system, such as whether the coal feeder is broken, slipped, deviated, and blocked; whether the hot and cold air baffles are stuck; whether the air powder pipe is blocked; When it is found that the combustion is unstable, add oil in time to stabilize the combustion; increase the outlet temperature of the pulverized coal mill to make the pulverized coal easier to catch fire.
5. Increase the primary and secondary air temperature. When the temperature is low, you can turn on the primary and secondary air hot air recirculation, and try to automatically control the gap between the fan-shaped plates of the air preheater. When the load is high, the soot blowing of the water wall and horizontal flue should be strengthened to prevent the large pieces of coke from falling and affecting the combustion when the load is low. Pay attention to the operation of the furnace body, such as: water seal at the bottom, whether the soot blower is stuck, the condition of each heating surface, and whether the fire holes are all closed to prevent cold air from leaking into the furnace.
6. The principle of air distribution
The principle of air distribution is to ensure ignition stability and complete combustion. For the once-through burner with equal air distribution, the mixing time of the primary and secondary air is early, which is suitable for bituminous coal and lignite with relatively high volatile content, because the volatile content of the combustible base of the coal used in this plant is 16% to 20% (the design is 33%) , basically belong to lean coal. When the coal quality is poor or suddenly deteriorates, the combustion should be adjusted in time, especially at the low load stage, attention should be paid to:
(1) The primary wind speed and wind pressure should not be too high or too low. The air volume of the pulverized coal mill is low under the premise of ensuring that the mill is not blocked, so as to increase the flue gas temperature and coal powder concentration near the burner, and improve the ignition stability.
(2) The auxiliary air baffle between adjacent running mills should be relatively closed, and the upper secondary air should be opened larger, using an inverted pagoda for air distribution, similar to graded air distribution burners, so that the secondary air can mix with the flue gas later , stable combustion.
(3) Due to the late mixing of the secondary air and the primary air, the secondary air is required to have sufficient momentum to penetrate the high-temperature flue gas and contact with the coke particles. A higher differential pressure of the secondary air box and the furnace should be ensured. The worse the coal quality, The differential pressure should be higher.
(4) When the load is low, the fuel air should be turned down as much as possible, which can increase the concentration of pulverized coal and reduce the amount of cold air at the initial stage of combustion, especially for coals with low volatile content. Using the above method to adjust the running combustion can significantly reduce the number of flameouts, save fuel and improve the economy of unit operation.