1 Large adjustment range for flame shape

After the internal, external, and coal winds are ejected, the resulting velocity difference at the outlet promotes a rapid transfer of momentum, leading to efficient mixing. Meanwhile, the scorching secondary air from the clinker cooler helps ignite the pulverized coal, enabling it to reach its combustion point and form a stable flame. The internal, external, and coal winds collectively create three coaxial jets. The tangential velocity of the swirling inner wind, upon exiting, entrains the outer coal wind, inducing rotational motion in the entire flow. The magnitude of this angular momentum precisely controls the divergence angle of the jet—and thus determines the shape of the flame. Moreover, the level of angular momentum within the jet can be finely tuned by adjusting the flow rate ratio between the inner and outer winds. This flexibility allows for precise control over the flame’s geometry, ensuring it meets the specific requirements of the rotary kiln’s clinker calcination process.

When the raw material entering the kiln is not properly preheated in the decomposition furnace, and the feed rate at the kiln head is relatively high, the central control operator should reduce the material flow and slow down the kiln speed while simultaneously increasing the proportion of internal air to intensify calcination, thereby significantly minimizing the risk of "material backflow."

2 Energy-Saving Advantages

(1) This approach can significantly reduce the primary air consumption, achieving the goal of coal savings. Typically, the primary air previously accounting for 20% of the total air volume can be lowered to just 7-8%. This creates favorable conditions for increasing the use of high-temperature secondary air, while also reducing the electricity required for primary air supply.

(2) Increasing the primary air velocity enhances the thrust of the coal pipe against the flame, accelerating the combustion rate of the pulverized coal and promoting complete burning.

(3) It demonstrates strong adaptability to different coal qualities, making it possible to utilize low-quality coals such as anthracite and high-ash, low-calorie fuels. Nevertheless, the design should still be based on a relatively stable coal quality as the fundamental requirement.

(4) The role of the central air. Multi-channel burners are equipped with an additional central air supply—though it’s not high in volume or pressure—but its function should not be underestimated. Introducing a small amount of cool air into the flame center not only helps lower the local temperature, but also counteracts the negative pressure zone created by swirling airflow near the nozzle, effectively preventing "backflow" or "flashback." This, in turn, extends the lifespan of the nozzle. Additionally, the reduced temperature at the flame center further minimizes NOx emissions.

3 High combustion intensity

Traditionally, the central jet of a single-airway burner has a very high pulverized coal concentration—about three times higher than the kiln's outer diameter—and the flame region within this area suffers from severe oxygen deficiency, making it difficult to achieve higher flame temperatures. In contrast, multi-airway burners incorporate an inner air stream that serves as combustion-supporting air at the flame’s core, significantly enhancing the overall combustion efficiency. Additionally, the angular momentum generated by the swirling jets and the velocity differences among individual jet streams intensify turbulence at the nozzle exit, further boosting flame intensity. As a result, this improved combustion process not only enhances clinker quality but also boosts production output.

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