Refractory Bricks

The influence of frequent start and stop of rotary kiln on refractories and matters needing attention

Dec 21,2020

For the rotary kiln, the number of shutdowns of the rotary kiln directly affects the service life of the rotary kiln. There is a proverb, "The machine is afraid of turning on, the electricity is afraid of stopping, and the refractory bricks are afraid of turning on and off." This indicates that the rotary kiln has certain requirements for the thermal shock performance of refractories.
In the production of rotary kiln, due to frequent unplanned opening and closing of the kiln, due to emergency stop of the kiln, the hot surface of the refractory lining will cool rapidly, shrink too fast, and produce serious destructive force in the brick. The second shutdown of the kiln frequently acts on the castable lining, resulting in premature cracking and damage; when the kiln is opened again, the hot surface layer of the lining refractory material often peels off with the kiln skin, which also causes the brick position in the kiln lining to be distorted, reducing the use of refractory lining life.
So, how to reduce the number of kiln start-ups and shutdowns is a question that users have been concerned about. Regarding how to control the number of shutdowns of the rotary kiln:
1. Ensure the stable operation of rotary kiln equipment.
2. Secondly, we must ensure the stability of coal and material quality.
3. At the same time, the stability of the amount of coal and materials must be controlled.
Therefore, in the process of starting and stopping the kiln, the corresponding adjustment of the operating parameters of the system, the inventory of the pulverized coal silo, and the next kiln opening time must be carefully considered and deployed.
1. 2 hours before the scheduled flameout, reduce the supply of raw meal, gradually reduce the coal in the decomposition furnace, and then gradually reduce the amount of raw meal to prevent the preheater system from overheating.
2. Open the cold air valve slowly so that the inlet temperature of the high temperature fan does not exceed 400°C.
3. When the temperature at the outlet of the calciner drops to 600-650℃, stop the material completely and reduce the kiln speed to 0.5r/min to control the coal consumption of the kiln head.
4. Reduce the high temperature fan pulling wind.
5. While reducing the wind, reduce the kiln head feeding coal and prevent the raw meal from leaving the kiln.
6. Stop spraying water from the humidification tower, and then continue to reduce wind.
7. When the tail temperature drops below 800℃, stop the kiln head to feed coal, and then stop the high temperature fan, the cold air valve is fully opened, and the inlet valve of the kiln tail large bag exhaust fan is used to control the air consumption. Note that after the kiln head stops coal, the necessary primary air volume must be maintained to prevent the coal injection pipe from deforming.
8. Stop the cylinder cooling fan unit and the kiln mouth sealing ring cooling fan as appropriate.
9. The large cloth bag at the end of the kiln, the ash-returning conveying system and the raw meal feeding system.
10. When the temperature of the rotary kiln shell is below 250℃, the auxiliary rotary kiln is changed.
11. After the kiln head is turned off, pay attention to the negative pressure control of the kiln head cover, that is, reduce the soy air of the grate cooler and the exhaust air of the kiln head exhaust fan.
12. When the output of the kiln is very small, stop the grate cooler. After a period of time, the fans from the sixth chamber to the first chamber stop one by one.
13. Stop kiln head electric dust collector, clinker conveying, primary fan. The exhaust fan of the electric dust collector at the kiln head is used to control the negative pressure of the kiln.
14. Depending on the situation, stop the coal feeding fan and gradually pull out the coal injection pipe.

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