Burner positioning refers to precisely adjusting the burner nozzle to a specific location at the kiln mouth of the rotary kiln, ensuring that the high-temperature flame generated by combustion maintains optimal clinker quality. At the same time, proper positioning helps the rotary kiln develop a dense, uniformly thick and thin kiln skin of ideal length, preventing erosive damage to the refractory bricks inside the kiln. The three key elements of burner positioning are the vertical (y-axis) value, the horizontal (x-axis) value, and the front-to-back position—all representing the relative placement of the burner nozzle in relation to the kiln mouth. Typically, when we talk about burner positioning, we’re referring specifically to determining the vertical (y-axis) and horizontal (x-axis) values.

2.1.1 Vertical Value (Y-axis)

The burner height value refers to the relative position of the burner nozzle center in the vertical cross-section at the kiln mouth of the rotary kiln (along the y-axis). It determines the tendency and length of the burner's free-impingement jet flame when unaffected by disturbances from the secondary air supplied by the cooler. Setting the burner height value too high or too low will both influence the length of the burner flame.

2.1.1.1 High-Direction Value Oversetting

If the burner height setting is set too high, the burner jet tendency and firing point will shift toward the far end of the kiln, resulting in an excessively long flame length. This positioning setup is suitable for kiln conditions where coal powder has a high calorific value, raw materials exhibit excellent burnability, and clinker bulk density and free calcium oxide (f-CaO) content are easily controlled. However, it’s important to note that when the burner height is set too high, the refractory bricks in the upper and lower transition zones of the rotary kiln may be prone to erosion, while the kiln skin in the latter half of the burning zone tends to become thinner, and the temperature in the heat-releasing reaction zone may rise excessively.

2.1.1.2 Low Setting for Vertical Value

If the burner height setting is too low, the burner jet will tend to shift toward the near end of the kiln, resulting in a shorter flame length. This positioning setup is particularly suitable for kiln conditions where coal powder has lower calorific value, raw materials are harder to burn, and it’s challenging to control the clinker bulk density and f-CaO content.

2.1.2 Horizontal Value (X-axis)

The burner's horizontal position value refers to the relative left-right placement of the burner nozzle's center along the horizontal cross-section at the kiln mouth of the rotary kiln (along the x-axis). If the horizontal position value is set toward the material layer (i.e., "biased toward the material"), the high-temperature point of the burner flame will be closer to the material layer, enhancing the material calcination process. Conversely, if the horizontal position value is adjusted toward the kiln's internal space (i.e., "biased toward the air"), the pulverized coal will burn more completely, helping to reduce the formation of "yellow-core material."

2.1.3 Forward and Backward Direction Values

The front-to-back position value of the burner refers to the relative positioning of the burner nozzle face in relation to the rotary kiln's kiln mouth face, typically measured with the cold-state kiln mouth face as the reference point. When the burner extends into the kiln mouth, coal powder combustion experiences minimal disturbance from the secondary air supplied by the grate cooler, making it easier to control the cylinder temperatures both upstream and downstream of the kiln head's wheel band. However, the burner nozzle tip tends to accumulate material buildup, requiring frequent cleaning. On the other hand, if the burner is retracted outside the hot kiln mouth for calcination, the coal powder combustion is significantly influenced by the higher-temperature secondary air from the grate cooler, which enhances combustion efficiency. Yet, under these conditions, the refractory bricks at the rotary kiln's kiln mouth area are subjected to even higher temperatures. Moreover, when kiln operating conditions are unfavorable, the fixed bed within the grate cooler is more likely to form "snowman" accumulations.

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