I. Basic Definitions

Rotary kiln burners are the core heating equipment for all types of rotary kilns. They precisely meter and inject fuel together with primary air, entrain high‑temperature secondary hot air from within the kiln, and generate a controllable flame, providing a stable heat source for material calcination. They are widely used in rotary kilns for cement, lime, zinc oxide, expanded clay, pelletizing, lithium mining, alkali sulfide production, hazardous waste incineration, metallurgical roasting, and other applications.

II. Mainstream Classification

(1) Classified by Fuel Type

Pulverized coal burner (most widely used)

Fuel: bituminous coal, anthracite, semi-coke, petroleum coke;

Auxiliary equipment: pulverized coal fan, pulverized coal silo, and pulverized coal preparation system.

Representative: three‑pass and four‑pass low‑NOx pulverized‑coal burners.

Gas burner

Fuels: natural gas, coke oven gas, blast furnace gas, producer gas, liquefied petroleum gas;

Features: precise temperature control, dust-free operation, and a high degree of automation; low-calorific-value gas requires a dedicated flashback‑prevention design.

Fuel/ Methanol Burner

Fuels: diesel, heavy oil, tar, and methanol; commonly used for kiln ignition and small-scale kilns.

Multi-fuel co-firing burner

Dual-fuel operation with pulverized coal and natural gas, or coal and oil, allows for flexible fuel switching and adapts to fluctuating fuel prices.

(2) According to the duct structure (main coal-powder flow)

Three-channel burner

Channel (inner → outer): Central air → Coal air → Axial flow air

Advantages: simple structure, moderate cost; suitable for high-volatile bituminous coal.

Weakness: The flame‑control range is limited, and its adaptability to low‑volatile coals is moderate.

Four-channel burner (currently the mainstream recommendation)

Flow path (inner → outer): Central airflow → Swirl airflow → Coal airflow → Axial airflow

Central air: stabilizes the flame, protects the nozzle, and incorporates a built-in igniter;

Swirl air: creates a recirculation zone, enhancing ignition; increasing its flow rate results in a short, stout flame.

Coal air: conveys pulverized coal;

Axial airflow: high‑velocity jet that controls flame length and stiffness; increasing the flow rate elongates the flame.

Advantages: low primary air ratio (5%–8%), high burnout rate, strong adaptability to low-volatile coals, wide flame‑adjustment range, and low NOₓ emissions.

Old‑style single- or dual‑channel kilns: being phased out; used only in small, simple kilns.

III. Key Structural Components

Main nozzle: 310S heat-resistant stainless steel, with a high-temperature castable protective layer on the combustion tube;

Airflow regulation mechanism: manual/electric damper, with independent adjustment of swirl airflow and axial airflow.

Ignition System: Ignition torch (diesel/natural gas), UV ultraviolet flame detector;

Mobile trolley: electrically driven for forward and backward movement, allowing adjustment of the burner’s insertion depth into the kiln;

Combustion control system: PLC interlocks, high- and low-pressure protection, emergency shut-off, and flame-out protection.

IV. Flame Regulation (Four-Channel Pulverized Coal)

Increased swirl air: the flame becomes shorter and thicker, with high root‑zone temperatures, making it prone to eroding the kiln lining.

Increasing the axial airflow: the flame elongates, its rigidity increases, and it penetrates more deeply.

Excessive central airflow: the flame becomes diffuse and the temperature drops; insufficient airflow can easily cause nozzle burnout.

Ideal operating conditions: the flame does not erode the kiln lining, the temperature distribution is uniform, there are no localized hot spots, and no black smoke is emitted from the kiln tail.

V. Key Considerations for Selection Across Different Fields

Cement rotary kiln

Primarily a four‑channel pulverized‑coal burner, with an emphasis on low NOx emissions; primary air pressure of 35–55 kPa; with particular focus on maintaining stable kiln skin.

Zinc Oxide / Zinc Suboxide Rotary Kiln

Local overheating and clinker ring formation are strictly prohibited; a four‑channel, fully adjustable design is preferred; the flame should not be excessively short, while ensuring both pre‑kiln oxidation and a weakly reducing atmosphere in the kiln.

Lime and ceramic aggregate rotary kiln

Natural gas kilns are equipped with multi‑channel gas burners; pulverized coal kilns ensure uniform flame spread to prevent underburning.

Hazardous waste incineration rotary kiln

High‑power modulation ratio (1:6 or greater), combined with high‑temperature‑resistant, corrosion‑proof materials, ensures stable operation in the high‑temperature zone and suppresses dioxin formation.

VI. Common Faults

Nozzle ablation and coking: insufficient central air, flame backflow, and high ash content in the coal.

Flame drift and lack of rigidity: insufficient axial‑flow fan pressure and an overall primary air flow that is too low.

Incomplete combustion of pulverized coal and smoke at the furnace outlet: swirl intensity too low, poor mixing, and inadequate pulverized‑coal fineness.

Excessive NOₓ: The peak temperature at the flame root is too high; optimize the swirl-to-axial flow ratio and implement staged combustion.

7. Parameters must be provided for model selection.

Rotary kiln specifications (diameter × length) and design capacity;

Fuel type, calorific value, and coal quality (volatile matter, ash content, fineness);

Target calcination temperature and kiln atmosphere requirements (oxidizing / weakly reducing);

Primary fan pressure and environmental emission indicators;

Is a furnace ignition torch, automatic retract‑and‑advance mechanism, and fully automated combustion control system required?

Rotary Kiln Burner: Information on Combustion and Application Fields

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