1. Primary Air
Primary air is used to transport heated pulverized coal, allowing it to enter the furnace through the primary air duct. It also provides the oxygen necessary for the volatile components in the pulverized coal to ignite and burn. Primary air, delivered by hot air, also preheats the pulverized coal. Besides maintaining a certain concentration of the gas-pulverized coal mixture for easier transport, it also provides sufficient oxygen for the fuel during the initial combustion phase. Primary air can be divided into cold and hot primary air. Hot primary air ensures the pulverized coal reaches a certain temperature upon entering the boiler, improving energy efficiency. Cold primary air regulates the temperature of the hot primary air to maximize heat exchange efficiency. After entering the furnace, the pulverized coal carried by the primary air is supplied with oxygen by the secondary air.
2. Secondary Air
Secondary air is hot air delivered to the furnace through a separate duct in the burner. It gradually mixes with the primary air upon entering the furnace. Secondary air provides oxygen for carbon combustion and enhances airflow turbulence, promoting the recirculation of high-temperature flue gases and the mixing of combustibles with oxygen, thus ensuring complete combustion. The secondary air volume is the largest of the primary and tertiary air volumes, accounting for a significant proportion of the total air volume.
3. Tertiary Air
Tertiary air is the dry exhaust air from the pulverizing system, commonly known as "exhaust gas." It serves as the medium for transporting pulverized coal. It is called primary air during pulverization and tertiary air only when introduced into the furnace through separate nozzles. Tertiary air contains a small amount of pulverized coal and has a high velocity, providing a strong mixing effect during the pulverized coal combustion process and replenishing the oxygen required for the burnout phase. Due to its low temperature and high water vapor content, it has the effect of lowering furnace temperature.
4. Center Air
The center air serves to increase the rigidity of the primary air, preventing pulverized coal segregation and scattering, and to supplement air volume, reducing carbon losses due to incomplete combustion. The center air is the fundamental difference between four-channel and three-channel burners. Its functions are: 1. Cooling the burner tip and protecting the nozzle. 2. Creates a bowl effect (airflow recirculation) at the burner end, making the flame more stable. 3. Reduces the end flame temperature and reduces the formation of harmful NOx gases.
5. Auxiliary Air
The auxiliary air control system uses the differential pressure of the secondary air box as the controlled variable. The set value of the windbox/furnace pressure differential is determined as a function of the load. The auxiliary air control system is a single-impulse, multi-output control system. The control system output simultaneously controls the auxiliary air dampers on each floor. During operation, the load of each pulverizer floor may vary, requiring different air distribution. Therefore, each floor's auxiliary air damper is equipped with an operator offset station. When the oil gun is programmed to ignite, the corresponding auxiliary air damper automatically moves to the "oil gun ignition" position.
6. Fuel Air (Ambient Air)
The fuel air (ambient air) control system is a ratio-based control system. The opening of the fuel air damper is determined by the speed of the corresponding coal feeder. The fuel air damper's opening is a function of the corresponding coal feeder speed.
7. Overburn Air
The overburn air control system is also a ratio-based control system, with the overburn air damper opening being a function of boiler load.
1. Primary Air
Primary air is used to transport heated pulverized coal, allowing it to enter the furnace through the primary air duct. It also provides the oxygen necessary for the volatile components in the pulverized coal to ignite and burn. Primary air, delivered by hot air, also preheats the pulverized coal. Besides maintaining a certain concentration of the gas-pulverized coal mixture for easier transport, it also provides sufficient oxygen for the fuel during the initial combustion phase. Primary air can be divided into cold and hot primary air. Hot primary air ensures the pulverized coal reaches a certain temperature upon entering the boiler, improving energy efficiency. Cold primary air regulates the temperature of the hot primary air to maximize heat exchange efficiency. After entering the furnace, the pulverized coal carried by the primary air is supplied with oxygen by the secondary air.
2. Secondary Air
Secondary air is hot air delivered to the furnace through a separate duct in the burner. It gradually mixes with the primary air upon entering the furnace. Secondary air provides oxygen for carbon combustion and enhances airflow turbulence, promoting the recirculation of high-temperature flue gases and the mixing of combustibles with oxygen, thus ensuring complete combustion. The secondary air volume is the largest of the primary and tertiary air volumes, accounting for a significant proportion of the total air volume.
3. Tertiary Air
Tertiary air is the dry exhaust air from the pulverizing system, commonly known as "exhaust gas." It serves as the medium for transporting pulverized coal. It is called primary air during pulverization and tertiary air only when introduced into the furnace through separate nozzles. Tertiary air contains a small amount of pulverized coal and has a high velocity, providing a strong mixing effect during the pulverized coal combustion process and replenishing the oxygen required for the burnout phase. Due to its low temperature and high water vapor content, it has the effect of lowering furnace temperature.
4. Center Air
The center air serves to increase the rigidity of the primary air, preventing pulverized coal segregation and scattering, and to supplement air volume, reducing carbon losses due to incomplete combustion. The center air is the fundamental difference between four-channel and three-channel burners. Its functions are: 1. Cooling the burner tip and protecting the nozzle. 2. Creates a bowl effect (airflow recirculation) at the burner end, making the flame more stable. 3. Reduces the end flame temperature and reduces the formation of harmful NOx gases.
5. Auxiliary Air
The auxiliary air control system uses the differential pressure of the secondary air box as the controlled variable. The set value of the windbox/furnace pressure differential is determined as a function of the load. The auxiliary air control system is a single-impulse, multi-output control system. The control system output simultaneously controls the auxiliary air dampers on each floor. During operation, the load of each pulverizer floor may vary, requiring different air distribution. Therefore, each floor's auxiliary air damper is equipped with an operator offset station. When the oil gun is programmed to ignite, the corresponding auxiliary air damper automatically moves to the "oil gun ignition" position.
6. Fuel Air (Ambient Air)
The fuel air (ambient air) control system is a ratio-based control system. The opening of the fuel air damper is determined by the speed of the corresponding coal feeder. The fuel air damper's opening is a function of the corresponding coal feeder speed.
7. Overburn Air
The overburn air control system is also a ratio-based control system, with the overburn air damper opening being a function of boiler load.