Operation Methods for Adjusting Rotary Kiln Flame Length via Burner

Note: This operation applies to multi-channel pulverized coal burners (swirl-axial combined type) of cement rotary kilns under working conditions with phosphate refractory bricks. Direct flame scouring on kiln lining is strictly prohibited.

1. Basic Principles

1. Swirl Air (Inner Air): Generates swirling airflow, entrains high-temperature flue gas inside the kiln, advances pulverized coal ignition, and forms a shorter and thicker flame.

2. Axial Air (Outer Air): Forms high-speed axial jet flow with strong penetration, pushes the flame deep into the kiln, and forms a longer and thinner flame.

3. Total Primary Air Volume: Excessive volume reduces kiln head temperature and increases heat consumption; insufficient volume causes poor coal-air mixing and severe post-combustion.

4. Burner Forward and Backward Position: Pushing the burner deeper into the kiln lengthens the flame; retracting the burner close to the kiln mouth shortens the flame.

Core Principle: Prioritize adjusting the ratio of inner and outer air, then fine-tune the burner position. Avoid large-scale adjustment of total primary air volume.

2. Adjustment for Overlong Flame

(Phenomena: Burning zone moves backward, kiln tail temperature rises, rear ring formation easily occurs, flame scours rear refractory bricks)

Operation Steps

1. Increase the opening of swirl air (inner air) and appropriately reduce axial air (outer air) to strengthen swirling intensity, advance coal ignition and shorten the flame.

2. Retract the burner outward close to the kiln mouth and avoid excessive deep insertion.

3. Appropriately reduce kiln tail negative pressure within process allowable range to lower system exhaust volume and flue gas flow velocity in the kiln.

4. Check pulverized coal condition: excessively coarse coal and high moisture will cause flame elongation; improve coal fineness if conditions permit.

5. Increase secondary air temperature and properly control tertiary air volume to avoid excessive tertiary air.

6. Observation standard: Flame length shortens, burning zone moves forward, and kiln tail temperature drops. Strictly prevent over-short flame from causing concentrated high temperature and erosion of kiln coating and phosphate bricks.

3. Adjustment for Over-short Flame

(Phenomena: Over-concentrated high temperature, excessive kiln mouth temperature, kiln coating and brick burning damage, over-burned clinker)

Operation Steps

1. Increase axial air (outer air) and appropriately reduce swirl air (inner air) to enhance jet penetration and lengthen the flame.

2. Push the burner deeper into the kiln to extend the flame backward.

3. Properly increase kiln tail negative pressure, raise system exhaust volume and flue gas flow velocity inside the kiln.

4. Appropriately relax pulverized coal fineness (avoid over-coarse coal to prevent post-combustion and ring formation).

5. Keep secondary air temperature within normal range and match tertiary air volume reasonably.

6. Monitoring standard: Flame is moderately lengthened, high-temperature zone moves backward, kiln mouth temperature decreases, and rear ring formation caused by overlong flame is avoided.

4. Key Points for Burner Position Operation

1. Adjust forward and backward position in small increments of 20‑50 mm each time. Keep stable for 10‑20 minutes after adjustment to observe kiln temperature, kiln coating and clinker condition. Large one-time displacement is forbidden.

2. Under normal working conditions, keep the burner center aligned with the kiln cylinder center. Deviation upward, downward or sideward is prohibited, which will cause local flame scouring on refractory bricks (phosphate bricks are most vulnerable to long-term flame scouring).

3. Clean thick coating at the kiln mouth timely, as it will distort the normal flame shape.

5. Total Primary Air Volume Control

1. Avoid large adjustment of total primary air volume; adjust flame shape preferentially by changing the distribution ratio of inner and outer air.

2. Excessive primary air: cools the kiln head, increases heat consumption and NOₓ emission.

3. Insufficient primary air: leads to poor coal-air mixing, incomplete combustion and serious post-combustion.

6. Important Linked Operation Notes

1. When adjusting burner flame, synchronously monitor secondary air temperature, tertiary air volume, kiln tail negative pressure, kiln speed and coal feeding rate. Independent single-factor adjustment is not allowed.

2. For burning zones lined with phosphate bricks: the flame shall not directly scour the brick lining, and stable kiln coating must be maintained for protection.

3. Observe kiln coating changes after flame adjustment to prevent local overheating, coating peeling and subsequent phosphate brick damage.

4. NOₓ control: Increased swirl air usually raises NOₓ emission; increased axial air reduces NOₓ emission. Balance combustion effect and environmental protection emission during adjustment.

7. Troubleshooting for Common Abnormalities

1. Floating and divergent flame: Insufficient swirl intensity, burner center deviation or unreasonable primary air ratio. Correct burner alignment first, then adjust swirl air volume.

2. Unstable fluctuating flame: Fluctuations in coal supply, air pressure or tertiary air. Stabilize system operating conditions preferentially.

3. Flame lift-off and delayed ignition: Low secondary air temperature, high pulverized coal moisture or insufficient swirl air.

8. Concise Operation Formula

Overlong flame: Increase swirl air, decrease axial air, retract burner, reduce kiln tail negative pressure.

Over-short flame: Increase axial air, decrease swirl air, insert burner deeper, raise kiln tail negative pressure.

Priority to adjust air ratio, fine-tune position, operate in small and slow steps, and monitor kiln coating and refractory bricks continuously.