The function of the primary and secondary air dampers in the heating furnace

The hot air is regulated by a butterfly valve and enters the air box; part of it goes into an annular channel formed by the nozzle and adjustable internal components, where it mixes with the fuel gas emitted by the nozzle. This gas is referred to as primary air； Another portion enters the annular space between the adjustable internals and the burner bricks, where it mixes again with the already mixed fuel gas; this portion of gas is known as secondary air. The ratio of primary air to secondary air is adjusted by a wave-shaped nut mounted on an adjustable component.

Primary air is used to regulate the combustion condition of the flame and its color, while secondary air is mainly used to control the length of the flame.

The primary air is ejected from the circumferential nozzles around the burner to mix with the fuel; if its volume is too large, it can blow the flame away from the burner chamber or even extinguish it. The secondary air is ejected parallel around the fire basin; it serves as auxiliary air and can be adjusted slightly to prevent the flame from damaging the fire basin.

Primary air flows through the furnace chamber to ensure proper combustion, while secondary air flows along the furnace walls to cool down the furnace and maintain the temperature at its outlet.

The air supplied to the primary combustion chamber is primary air; the valve for the primary combustion chamber is located near the burner, while the valve for the secondary combustion chamber is connected to the primary combustion chamber. The function of the primary air damper is to control the air supplied for combustion, stabilize the combustion process, and reduce the formation of carbon black. The air supply for the secondary combustion is called secondary air, and it is controlled by a secondary air damper. Its function is to provide supplementary air when the primary air is insufficient for combustion, as well as to adjust the angle of the flame.

I’ve learned a lot from everyone’s replies; I’d like to add a few more points. Primary air is used for the main burners – mainly the fuel nozzles – to control the combustion of the flame, and the adjustment range for this air flow should not be too large. Secondary air is used with dry gas or gas; it has a higher flow rate and its main purpose is to control the combustion throughout the entire burner area, while also helping to protect the flame barrier around the burners.

The hot air is regulated by a butterfly valve and enters the air box; part of it goes into an annular channel formed by the nozzle and adjustable internal components, where it mixes with the fuel gas emitted by the nozzle. This gas is referred to as primary air； Another portion enters the annular space between the adjustable internals and the burner bricks, where it mixes again with the already mixed fuel gas; this portion of gas is known as secondary air. The ratio of primary air to secondary air is adjusted by a wave-shaped nut mounted on an adjustable component. This expression is correct.

Primary air is mainly used to regulate the combustion in the burner, while secondary air is used to assist in combustion

Answer: At startup, it is used to heat the catalyst in the regenerator; primary air enters the furnace to provide the oxygen required for combustion； The secondary air enters the jacket of the cylinder to serve a cooling purpose, preventing the steel plates from overheating. If all of the primary air were to enter the furnace, the wind velocity would be too high, affecting the stability of the flame and even extinguishing it; it would also be impossible to reignite the flame. Therefore, adjusting the amount of primary air is essential to ensure stable and complete combustion. When the load increases, it is necessary to adjust the amount of primary air promptly. The adjustment of both primary and secondary air amounts not only serves to meet the requirements of combustion but also helps to prevent the furnace from overheating, as well as to accommodate changes in the temperature of the regenerator bed.

What was mentioned upstairs refers to the primary main air and secondary main air for the auxiliary combustion chamber in catalytic cracking. It is used to heat the catalytic feed oil at the start of catalytic operation. The narration is also correct. The primary and secondary air dampers here clearly refer to the air used in ordinary heating furnaces to regulate the furnace temperature. Other means for regulating the furnace temperature include flue dampers, inlet air duct butterfly valves, and on-site fuel gas manual valves