1 Working principle of plasma ignition pulverized coal burner
The basic principle of plasma ignition technology is to directly ignite pulverized coal with a high-power arc. The ignition device uses direct current (greater than 200 A) to strike the arc through the contact of cathode and anode under the condition of medium pressure greater than 0.01MPa, and obtains stable power direct current air plasma under strong magnetic field. Its continuously adjustable power range is 50-150 kW, and the core temperature can reach 6000 ℃. The primary air powder is fed into the plasma ignition pulverized coal burner and separated from thick and thin, so that the dense phase pulverized coal enters the central area of the plasma torch and ignites rapidly within about 0.1s, and provides a high temperature heat source for the light phase pulverized coal, so that the light phase pulverized coal Also catches fire quickly, eventually forming a steady burning flare. The wall of the burner adopts film cooling technology, which can cool the wall of the burner, prevent burning and slagging, and use desalted water to cool the electrodes and coils.
2 plasma combustion system
The plasma combustion system is composed of two parts: ignition system and auxiliary system. The ignition system is composed of plasma burner, plasma generator, power control cabinet, isolation transformer, control system, etc.; the auxiliary system is composed of compressed air system, cooling water system, image flame detection system, primary wind online speed measurement system, etc.
.3 Plasma burner structure
The plasma burner adopts the internal combustion method and is three-stage powder feeding, which is composed of a plasma generator, air powder pipe, outer casing, nozzle, thick-thin block, and main burner. Since the wall of the burner is subjected to high temperature, film cooling air is added.
Plasma ignition burner system operation mode
In order to ensure the safety of the unit and the normal operation of the plasma ignition system, in the logic of the furnace safety monitoring system (FSSS), the C coal mill realizes the switching between "normal operation mode" and "plasma operation mode". In the "normal operation mode", the first layer of burners realizes the function of the main burner; in the "plasma operation mode", part of the starting conditions of the C coal mill is shielded, and the first layer of burners realizes the function of the ignition burner. ?
3.1 Operation mode of cold plasma ignition
a) According to the requirements of the operating regulations, the boiler is filled with water to the ignition water level, the fan is started, and the furnace purging procedure is completed. ?
b) Comprehensively inspect the subsystems of the plasma burner, and confirm that the parameters of compressed air, cooling air, cooling water, etc. are normal, and the plasma generator has the starting conditions. ?
c) The boiler is ignited, and a layer of diagonal oil burner is put into operation. After 30 minutes, another diagonal oil burner is added according to the cold start curve of the boiler. ?
d) Set C coal mill to run in "plasma operation mode", check that the pulverizing system is normal, the secondary air temperature reaches 90-130°C, start the primary fan and sealing fan, the starting conditions of the coal mill are met, and the C pulverizing system is put into operation Warm grind. Start the slag removing machine and the slag breaking machine to run. ?
e) Set the given current of the plasma generator to 300 A to start the arc, and after 5 minutes of stabilization, control the power of the plasma generator within the range of 80-120 kW according to the coal type. ?
f) Adjust the peripheral wind of the first layer of burners, and maintain the opening of the damper at 15%. ?
g) Start C pulverizing system. ?
h) Observe the combustion situation of the plasma burner on the spot, adjust the primary air volume and the opening of the perimeter air door, and determine the reasonable primary air speed and opening of the air door. ?
i) After the plasma burner burns stably, gradually reduce the oil burner until the oil burner is completely cut off and put into operation in the fourth electric field of the electrostatic precipitator.
j) Gradually increase the amount of fuel after the turbine is running fast, at a constant speed, and connected to the grid. ?
k) The output of C pulverizing system reaches 70%, put into the upper layer pulverized coal burner. Afterwards, according to the requirements of the regulations, the temperature is raised, the voltage is increased, and other electric dust removal fields are put into operation. ?
l) When the operating load reaches 110 MW and exceeds the minimum stable combustion load of the boiler, put the C pulverizer in the "normal operation mode", gradually stop using the four-corner plasma generator, and the boiler turns into normal operation. ?
3.2 Plasma combustion operation mode
a) When the boiler is combustion-supporting at low load and the load drops to around 110MW, put the plasma burners working in "normal operation mode" into the plasma generator one by one. When the plasma burners at the four corners are put into the plasma generator, set the C pulverizer to run in "normal operation mode" or "plasma operation mode" as required.
b) When the boiler slides to stop combustion and the load drops to around 110 MW, the plasma generator is put into operation, and the C coal mill is operated in the "normal operation mode", and the temperature and load are lowered steadily according to the regulations.
c) When the electrical load drops to 0, the unit is disconnected, the plasma burner is withdrawn, the electrostatic precipitator is shut down, and the boiler is shut down. ?
4 Plasma ignition burner system operation control parameters
4.1 System control parameters
In order to ensure the normal operation of the plasma generator, there are control requirements for power supply, compressed air, cooling water, water quality, etc.: load current 200-375 A, arc voltage 250-400V; compressed air pressure 0.12-0.3 MPa, compressed air volume flow 60 ～100 m3/h; cooling water pressure 0.15～0.40MPa, cooling water volume flow rate not greater than 10 m3/h; water quality is demineralized water, water temperature not greater than 40 ℃.
4.2 Burner control parameters
In order to ensure that the plasma burner ignites in time and burns stably when it is started and ignited, there are different requirements for the primary wind speed, air film cooling wind speed, pulverized coal supply, arc power, secondary air, etc. under different working conditions.
In short, the principle of adjusting the combustion of the plasma burner is: not only to ensure the stability of the ignition, reduce the loss of incomplete combustion, and increase the burnout rate, but also to open the atmospheric film or peripheral cooling air as much as possible with the increase of the furnace temperature and wind temperature to improve Primary wind speed, control the burner wall temperature measuring point not to exceed the temperature, the burner does not coke, and on the premise of meeting the temperature rise and pressure rise curve, put in other burners as soon as possible to increase the furnace temperature as soon as possible, which is conducive to improving the combustion efficiency.
1 Working principle of plasma ignition pulverized coal burner
The basic principle of plasma ignition technology is to directly ignite pulverized coal with a high-power arc. The ignition device uses direct current (greater than 200 A) to strike the arc through the contact of cathode and anode under the condition of medium pressure greater than 0.01MPa, and obtains stable power direct current air plasma under strong magnetic field. Its continuously adjustable power range is 50-150 kW, and the core temperature can reach 6000 ℃. The primary air powder is fed into the plasma ignition pulverized coal burner and separated from thick and thin, so that the dense phase pulverized coal enters the central area of the plasma torch and ignites rapidly within about 0.1s, and provides a high temperature heat source for the light phase pulverized coal, so that the light phase pulverized coal Also catches fire quickly, eventually forming a steady burning flare. The wall of the burner adopts film cooling technology, which can cool the wall of the burner, prevent burning and slagging, and use desalted water to cool the electrodes and coils.
2 plasma combustion system
The plasma combustion system is composed of two parts: ignition system and auxiliary system. The ignition system is composed of plasma burner, plasma generator, power control cabinet, isolation transformer, control system, etc.; the auxiliary system is composed of compressed air system, cooling water system, image flame detection system, primary wind online speed measurement system, etc.
.3 Plasma burner structure
The plasma burner adopts the internal combustion method and is three-stage powder feeding, which is composed of a plasma generator, air powder pipe, outer casing, nozzle, thick-thin block, and main burner. Since the wall of the burner is subjected to high temperature, film cooling air is added.
Plasma ignition burner system operation mode
In order to ensure the safety of the unit and the normal operation of the plasma ignition system, in the logic of the furnace safety monitoring system (FSSS), the C coal mill realizes the switching between "normal operation mode" and "plasma operation mode". In the "normal operation mode", the first layer of burners realizes the function of the main burner; in the "plasma operation mode", part of the starting conditions of the C coal mill is shielded, and the first layer of burners realizes the function of the ignition burner. ?
3.1 Operation mode of cold plasma ignition
a) According to the requirements of the operating regulations, the boiler is filled with water to the ignition water level, the fan is started, and the furnace purging procedure is completed. ?
b) Comprehensively inspect the subsystems of the plasma burner, and confirm that the parameters of compressed air, cooling air, cooling water, etc. are normal, and the plasma generator has the starting conditions. ?
c) The boiler is ignited, and a layer of diagonal oil burner is put into operation. After 30 minutes, another diagonal oil burner is added according to the cold start curve of the boiler. ?
d) Set C coal mill to run in "plasma operation mode", check that the pulverizing system is normal, the secondary air temperature reaches 90-130°C, start the primary fan and sealing fan, the starting conditions of the coal mill are met, and the C pulverizing system is put into operation Warm grind. Start the slag removing machine and the slag breaking machine to run. ?
e) Set the given current of the plasma generator to 300 A to start the arc, and after 5 minutes of stabilization, control the power of the plasma generator within the range of 80-120 kW according to the coal type. ?
f) Adjust the peripheral wind of the first layer of burners, and maintain the opening of the damper at 15%. ?
g) Start C pulverizing system. ?
h) Observe the combustion situation of the plasma burner on the spot, adjust the primary air volume and the opening of the perimeter air door, and determine the reasonable primary air speed and opening of the air door. ?
i) After the plasma burner burns stably, gradually reduce the oil burner until the oil burner is completely cut off and put into operation in the fourth electric field of the electrostatic precipitator.
j) Gradually increase the amount of fuel after the turbine is running fast, at a constant speed, and connected to the grid. ?
k) The output of C pulverizing system reaches 70%, put into the upper layer pulverized coal burner. Afterwards, according to the requirements of the regulations, the temperature is raised, the voltage is increased, and other electric dust removal fields are put into operation. ?
l) When the operating load reaches 110 MW and exceeds the minimum stable combustion load of the boiler, put the C pulverizer in the "normal operation mode", gradually stop using the four-corner plasma generator, and the boiler turns into normal operation. ?
3.2 Plasma combustion operation mode
a) When the boiler is combustion-supporting at low load and the load drops to around 110MW, put the plasma burners working in "normal operation mode" into the plasma generator one by one. When the plasma burners at the four corners are put into the plasma generator, set the C pulverizer to run in "normal operation mode" or "plasma operation mode" as required.
b) When the boiler slides to stop combustion and the load drops to around 110 MW, the plasma generator is put into operation, and the C coal mill is operated in the "normal operation mode", and the temperature and load are lowered steadily according to the regulations.
c) When the electrical load drops to 0, the unit is disconnected, the plasma burner is withdrawn, the electrostatic precipitator is shut down, and the boiler is shut down. ?
4 Plasma ignition burner system operation control parameters
4.1 System control parameters
In order to ensure the normal operation of the plasma generator, there are control requirements for power supply, compressed air, cooling water, water quality, etc.: load current 200-375 A, arc voltage 250-400V; compressed air pressure 0.12-0.3 MPa, compressed air volume flow 60 ～100 m3/h; cooling water pressure 0.15～0.40MPa, cooling water volume flow rate not greater than 10 m3/h; water quality is demineralized water, water temperature not greater than 40 ℃.
4.2 Burner control parameters
In order to ensure that the plasma burner ignites in time and burns stably when it is started and ignited, there are different requirements for the primary wind speed, air film cooling wind speed, pulverized coal supply, arc power, secondary air, etc. under different working conditions.
In short, the principle of adjusting the combustion of the plasma burner is: not only to ensure the stability of the ignition, reduce the loss of incomplete combustion, and increase the burnout rate, but also to open the atmospheric film or peripheral cooling air as much as possible with the increase of the furnace temperature and wind temperature to improve Primary wind speed, control the burner wall temperature measuring point not to exceed the temperature, the burner does not coke, and on the premise of meeting the temperature rise and pressure rise curve, put in other burners as soon as possible to increase the furnace temperature as soon as possible, which is conducive to improving the combustion efficiency.