A rotary kiln is a commonly used calcining equipment in the cement building materials industry. During long-term operation, it is necessary to regularly check the operation status of rotary kiln components to ensure the safe and stable operation of the rotary kiln. While improving the economic benefits of the enterprise, it can also effectively prolong the service life of the rotary kiln.
The elastic deformation of the rotary kiln is instantaneous. The common cause of such deformation is the temperature change of the rotary kiln shell, and such deformation may occur at any time. Due to the high temperature of the rotary kiln shell and the influence of its own gravity, in the selection process of the rotary kiln shell, the cylinder is generally a flat ellipse at the support of the kiln supporting roller, and the top of it is sunken. At the rotary kiln support roller, there is the reaction force of the support roller to the kiln shell, which causes the kiln shell to sag inwardly and deform. Specifically, the measurement of the ovality of the rotary kiln has made a detailed study of this.
Due to the gap between the rotary kiln shell and the kiln tyre ring, the rotary kiln shell has elliptical deformation, which causes the kiln shell to slide relative to the kiln tyre during operation. The elliptical deformation amount of the cylinder can be judged by measuring the relative sliding displacement between them. Excessive elliptical deformation will reduce the working life of the inner lining refractory brick, and in severe cases, the lining brick will be damaged and fall off.
- According to the kiln shell thickness and structural design of the rotary kiln, it is found that the deformation of the kiln shell is mainly caused by the overheating or uneven heating of the cylinder. During clinker calcination, the kiln shell on the refractory bricks inside the cylinder is not uniform due to the uneven bonding of clinker on the lining bricks. The tearing of the kiln shell and the possible damage to the lining bricks caused by the tearing will cause the uneven heating of the cylinder. The difference due to thermal deformation may cause plastic deformation of the kiln shell.
- In addition, the local wear, tear or damage of the lining brick can lead to overheating of the rotary kiln shell, increase the local deformation of the kiln shell, and lead to the cylindrical deformation of the cylinder. It will lead to the continuous destruction of the lining bricks. Such a vicious cycle will cause the refractory bricks to fall, the damaged area will increase, and the kiln shell will be deformed. It is necessary to master the welding technology of rotary kiln shells.
- When the rotary kiln is rotating, the local deformation and bending caused by thermal deformation will generate periodic load at each support, which will cause longitudinal tension to the kiln shell. This kind of pressure near the kiln tyre ring shows the short-term elastic deformation mentioned above due to the support of the kiln tyre, while at a farther distance from the support, the kiln shell yields to axial bending, and the section of the kiln shell yields to elliptical deformation. Lateral stresses are generated in turn. These factors lead to the characteristic cylindrical deformation of the kiln shell and the axial bending deformation of the kiln shell.
- The kiln shell is heated unevenly and bends. It mostly occurs when the kiln is not turned on a regular basis; such as damage to the transmission machinery or power failure. At this time, the temperature of the lower kiln shell increases due to the action of hot clinker, while the temperature of the upper cylinder decreases due to the cooling effect of heat dissipation and airflow, so the lower part of the kiln shell is much longer than the upper part, causing the kiln shell to bend.
Tips for rotary kiln shell deformation
Although the rotary kiln shell is lined with thick refractory bricks, the temperature of the kiln shell is still much higher than that of the cold kiln due to the action of high-temperature hot air during operation, and the firing zone is as high as 300-400 °C. The temperature gradually decreases towards both ends of the rotary kiln. At the discharge end, it reaches about 300 °C, and at the feeding end, it is about 200 °C. Therefore, the length and diameter of the kiln shell during operation are elongated and expanded compared with those of the cold kiln. Due to the low temperature of the kiln tyre installed on the outer periphery of the kiln shell, their radial thermal expansion is much smaller than that of the kiln shell. Generally, a gap should be reserved between kiln tyre and kiln shell during installation. Due to the axial thermal expansion of the kiln shell, the relative positions of the kiln tyre, support roller, and the girth gears and pinion all change. During installation, carefully check the dimensions of each part and allow for movement due to thermal expansion.
The displacement of the kiln shell due to thermal expansion along the axis direction is considered in this way. The kiln tyre sandwiched between the thrust roller are limited by the thrust rollers, and their axial movement is not large, so the position of the kiln tyre is regarded as neutral. Section, that is, where the rotary kiln shell does not move.
