The burner at the kiln head of a cement plant plays a pivotal role in clinker calcination. There are many different types of burners, and their usage and maintenance methods vary considerably. Almost every kiln shutdown involves an inspection of the burner head; any issues detected are addressed promptly to ensure the burner continues to function properly. However, since burners are relatively expensive to purchase, most companies lack clear guidelines on when a burner needs to be replaced during operation. They tend to assume that as long as the flame appears normal and there are no significant changes in kiln output or quality, the burner is still in good condition and can continue to be used without replacement. Most critically, burner manufacturers themselves do not provide a standardized criterion for determining when a burner should be replaced. As a result, our operating units typically only consider replacing a burner when they notice obvious signs of abnormal flame behavior—only after attempts at repair prove unsuccessful. Below, we’ll discuss the issue of replacing the burner head from the perspectives of burner performance and overall economic efficiency.

I. Current Status of Kiln Head Burner Usage

1. In many enterprises, the castable material of burners tends to fall off during operation, or localized wear and shedding can cause the burner body temperature to rise, leading to deformation and even damage from overheating.

2. Currently, most burners have relatively high air pressures, with the highest reaching 90 kPa. Typically, high-thrust burners operate at pressures between 60 and 70 kPa. The high pressure is mainly due to small clearances in the burner or large air volumes and high air velocities. As a result, during operation, the clean-air passage and coal-air passage of the burner are prone to wear. If the material quality used by the manufacturer during the burner’s fabrication process is substandard, severe wear will occur even after a short period of use. Some new burners show extensive and fairly deep wear grooves (approximately 5–8 mm) just two months after installation. Due to the irregular nature of this wear, the flame shape is seriously affected.

3. During the design process, burners are optimized for low air volume and high kinetic energy. As a result, the burner body diameter tends to be relatively small. However, the overall length of the burner remains unchanged. Consequently, the burner’s resistance to deformation deteriorates. Moreover, it is virtually impossible to monitor whether the burner deforms under thermal conditions, and many companies do not place much emphasis on this issue.

4. When burners in most enterprises show signs of wear or localized damage, to save on repair costs, some companies opt to repair them themselves by spot welding. In other cases, if the lower part of a burner is worn out and damaged, the company simply rotates the burner head by 180 degrees, placing the worn area on top for continued use. Still other companies, after their flame-deflecting shields become damaged, weld steel plates onto them themselves and keep using them.

The above-mentioned situations did not result in major quality or equipment accidents; otherwise, the company would still find ways to replace either the entire unit or just the burner’s local components.

II. The main factors affecting the performance of burners are as follows:

1. The technical level of the burner design unit.

2. The level of burner manufacturing and processing.

3. If there is a significant deviation between the actual operating conditions of the burner and its designed specifications, the performance will certainly be poor. For example, using a burner designed for bituminous coal to calcine anthracite will definitely result in suboptimal performance.

4. Adjustment of burner parameters—such as modifying the ratio of primary and secondary air or the gap in the air ducts during operation, based on the kiln conditions and material characteristics—is crucial. If these adjustments are not appropriate, the operational performance will be compromised.

5. The burner body itself shows signs of wear or damage. For example, the support blocks in the coal passage may become worn, leading to inconsistent gaps in the coal-air passage. This can affect the radial distribution of pulverized coal within the burner, thereby impacting the shape of the flame. Another example is the variation in the gap between the inner and outer air streams—particularly in burners whose head sections use small holes as outer-air passages to increase air velocity. Since these small holes typically have diameters around 20 mm, even minor wear can cause significant deviations. If a hole wears down by just 1 mm, this represents a 10% change relative to its original diameter of 20 mm. It’s easy to imagine that such a condition would undoubtedly affect the burner’s performance. Yet, detecting a 1-mm wear during routine inspections is often quite challenging.

6. Due to strength issues, the burner has deformed during operation. Although this deformation does not cause damage to the kiln’s refractory bricks, there is a high likelihood that the pulverized coal will burn poorly or end up entering the clinker.

III. Consequences of Issues Such as Burner Deformation and Wear

1. The most severe consequence I’ve witnessed is that, within a few hours, flame deformation can burn through the refractory bricks and the kiln shell in the firing zone. This situation is more likely to occur during the mid- or night shifts, or when the kiln head camera is malfunctioning and unable to provide monitoring of the kiln head area.

2. Slight deformation of the burner, or conditions that do not directly affect the equipment’s performance, can lead to a decline in clinker quality and an increase in coal consumption. It is very difficult to pinpoint the burner as the direct cause of such issues, which means the losses will persist. The cost of these ongoing losses will far exceed the expense of purchasing a new burner.

IV. Discussion on Burner Replacement Status

1. If the flame shape is noticeably deformed, or even causes damage to the equipment, the burner needs to be replaced—specifically, at least the burner head must be replaced.

2. If the inspection reveals that the burner head is burned through or cracked, do not attempt to repair it yourself. After being exposed to high temperatures, the weldability of the burner head will no longer meet the required standards, making it highly prone to failure. The burner head should be replaced promptly.

3. If the channel wear reaches around 10%, it is recommended to replace the burner head or the components with small holes.

4. A private business owner has stipulated that even if the burner surface appears to be in good condition, the burner—or rather, its head—must be replaced after three years of use. I wonder whether this practice will inspire others or whether they’ll still choose to repair it themselves or keep using it for longer just to save a bit on maintenance costs.

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