Working principle and adjustment method of kiln head burner
The kiln head burner is an important component of the mature material burned in the kiln, and the reasonable adjustment of its performance directly affects the service life of the kiln forging and lining. Adjust the butterfly valve opening of the external, internal, and central air of the burner appropriately, increase the local coal powder concentration before ignition, strengthen the high-temperature gas inside, outside, and reflux of the burner, and enhance the sufficient mixing of primary air to achieve complete combustion.
However, it should be noted that the internal wind should not be set too high, otherwise it may cause the coal powder to be diluted before ignition, which is actually unfavorable. It may also generate high-temperature flames, wash away the kiln skin, and cause the kiln skin to fall off, which is not conducive to the protection of refractory bricks. The internal wind should not be set too low, otherwise the coal powder cannot mix with the air quickly after ignition, which will lead to a decrease in the reaction rate of the coal powder, causing a large amount of carbon monoxide to be unable to oxidize into carbon dioxide in time, and causing a reducing atmosphere in the kiln.
In addition, the external wind should not be set too high, otherwise it will cause the burning flame to move backwards, and there will be thick kiln skin at the tail of the kiln or formation of circles and eggs near the transition zone. The external wind should not be too small, otherwise it will not produce strong flames, which is not conducive to calcining high-quality clinker. Therefore, reasonable operating parameters should be selected based on factors such as coal quality, fineness, moisture content, and secondary air temperature, as well as the kiln environment and Saint Louis burnability. By adjusting the optimal ratio of external air, internal air, and central air, as well as the reasonable position of burners near the kiln entrance, a suitable forging and firing system should be determined.
1. Positioning of the burner. Many companies use the "light column method" for burner positioning, which is precise in control but inconvenient to operate. It is best to use a position ruler to locate on the cross-section of the kiln head. Generally, controlling the position of the X-axis of the kiln head section slightly to the right or slightly to the four quadrants is more effective. If there are special process conditions, fine adjustments can be made.
2. The influence of flame shape on forging design. The optimal flame shape is at the position of axial and swirling air (0.0) (at which point each air duct has maximum ventilation), and the flame shape is complete and powerful. By adjusting the ventilation cross-sectional area of each air duct, the adjustment of flame shape was achieved. At point (0.0), the ventilation cross-sectional areas of axial and swirling air are the largest. Due to the mutual influence and restriction between swirling and axial airflow, the flame shape is achieved by the central airflow, and the central airflow cannot be too large or too small. Normally, the central wind pressure should be controlled between 6 and 8 KPa, with a swirl wind speed of 24-26 KPa and an axial wind speed of 23-25 KPa. When the ventilation cross-sectional area of each duct is not less than 90%, all parameters should be adjusted. To change the shape of the flame, a stable outlet pressure must be maintained, which can be achieved by changing the pressure on the burner and the ventilation cross-sectional area of each branch pipe.
3. Specific flame shape changes. When adjusting the shape of the flame, extreme phenomena should be avoided. When the flame is too thick, it will still be very long and soft. When the flame is too thin, it will be too short. Burning requires the flame to have a complete, lively, and powerful shape, which requires us to observe and summarize our experience for a long time.
4. The impact of coal quality changes on flame shape:
(1) The higher the ash content, the slower the combustion speed of coal powder, the longer the flame, and the longer the flame combustion zone. The following measures should be taken: ① Increase the temperature of the secondary air or make full use of the secondary air to improve the mixing degree of the primary air, secondary air, and coal powder; ② Reduce the fineness and moisture content of coal powder; ③ Change the air consumption rate of axial and swirling air, increase the primary air volume, and reduce the concentration of coal powder in the primary and secondary air.
(2) The higher the volatile content of coal, the faster the combustion rate, and the lower the oxygen concentration around the coke particles, making it easy to form flames close to the kiln head, with low stability and longer high-temperature parts. At this time, the following should be done: ① increase the oxygen content around the flame; ② Increase the airflow and wind speed of axial flow (in the original flame state); ③ Increase the primary air volume.
(3) When the moisture content in coal increases, increasing the temperature of the grinding gas can reduce its external humidity, while the internal water needs to evaporate at around 110 ℃. It is difficult to reduce the internal moisture content in coal powder mills. After the coal powder with high internal water content enters the kiln, the flame will become longer, the combustion speed will slow down, the flame temperature will decrease, and the black flame head will become longer. When appropriately increasing the auxiliary combustion effect of secondary air on the flame, increase the mixing of secondary air and primary air, increase the temperature of secondary air, appropriately discharge a part of the burner, use secondary air to increase the flame combustion speed, and achieve the goal of increasing the flame temperature.