Abstract: This article mainly analyzes the deviation of the centerline of the rotary kiln after long-term operation. In response to the large number of pits and cracks on the surface of the support roller, and the high risk of conventional adjustment of the support roller, a new adjustment method is proposed. The case of the author's team using the pad adjustment method to adjust the centerline of the kiln is introduced, providing reference suggestions for rotary kiln technicians.
The cement rotary kiln is mainly composed of six parts: cylinder body, support device, transmission device, hydraulic stop wheel device, kiln head, and kiln tail. The kiln body of the rotary kiln is inclined to the horizontal to a certain extent, and the entire kiln body is supported by the support roller device, rotating at a certain speed during operation. The interior of the rotary kiln is lined with bricks and materials.
The cement rotary kiln barrel will undergo bending deformation under gravity and high temperature, and the actual centerline of the barrel is a curve. When the rotary kiln is running, the center of the cylinder section rotates around an imaginary axis, causing the cylinder to bounce up and down. In order to measure and characterize, the centerline of the cylinder is usually measured as the straightness of the centerline connecting the centers of the rotary kiln cylinder at each support point. That is to say, the straightness of the cylinder is determined by connecting the center points of the cylinder at each support point into a straight line. An incorrect centerline can cause an increase in resistance during the operation of the rotary kiln, leading to an increase in power consumption; In addition, due to the uneven force caused by the swinging of the rotary kiln, it exacerbates the wear of external mechanical components and damages the refractory materials inside the rotary kiln, reducing the service life of the components; In severe cases, it can cause kiln shutdown faults such as cracking of the cylinder, falling of refractory bricks, and equipment damage. The production loss caused by shutting down the kiln, replacing parts, and replacing refractory materials is even greater. The adjustment of the kiln centerline is imperative.
1. On site measurement situation
The author conducted testing on XSL1 # Ø 4.0m × 60m kiln from January 8th to January 11th, 2022. Two horizontal measurement benchmarks were established on both sides of the rotary kiln axis, and one vertical measurement benchmark was established on the concrete pier of the rotary kiln (see Figure 1). The horizontal and vertical data measurement of the wheel belt, support roller, and support roller axle were transferred to the horizontal and vertical benchmarks for measurement, and then data processing was carried out. Direction regulation: Looking at the kiln head from the kiln tail, the direction from the kiln tail to the kiln head is the x-axis, the left and right directions of the kiln tail are the y-axis, the right direction is the positive direction, the left direction is the negative direction, and the up and down direction is the z-axis.
Figure 1: Horizontal and vertical deviation test principle diagram
The data detection results are as follows: (1) The horizontal deviation of the kiln centerline is -2.0mm, and the vertical deviation is+9.0mm (standard: horizontal deviation<1.5mm, vertical deviation<9.0mm, as shown in Figure 2). On site visual inspection revealed that the weld seam of the low-end cylinder of the second gear was cracked.
Figure 2: Kiln centerline deviation indicative diagram
(2) On January 9th, the slip of the tire belt was measured to be 24.0mm in first gear, 12.0mm in second gear, and 25.0mm in third gear. Based on this, the gap between the tire belt was calculated to be 7.6mm in first gear, 3.8mm in second gear, and 8.0mm in third gear (standard: 5-9mm in first gear, 3-6mm in second and third gears), as shown in Figure 3.
Figure 3: tyre distance and slip amount
(3)The working angle of the support roller is calculated to be 60 ° 20 ′ for the first gear, 60948 ′ for the second gear, and 60 ° 12 ′ for the third gear (standard: 60 °+1 ° 30 ′), with a kiln slope of 3.99% (design slope: 4.00%), as shown in Figure 4.
Figure 4 working diagram of support roller
(4)Measure the horizontal tilt of the support roller: 3.5mm on the left side of first gear, 1.5mm on the right side of first gear, 1.0mm on the left side of second gear, 2.0mm on the right side of second gear, 1.0mm on the left side of third gear, and 1.5mm on the right side of third gear (direction: from the kiln head to the kiln tail). Please refer to Figure 5 for specific schematic diagram.
Figure 5: horizontal inclination of support roller
(5)Measure the vertical tilt of the support roller: 2.0mm on the left side of first gear, 2.0mm on the right side of second gear, 2.0mm on the left side of second gear, 4.0mm on the right side of second gear, 2.5mm on the left side of third gear, and 1.0mm on the right side of second gear. Please refer to Figure 6 for specific schematic diagrams.
Future 6 Vertical inclination of support roller
2 Drawing of conventional adjustment plan for the centerline of rotary kiln
Draw an adjustment plan based on normal adjustment experience: with a horizontal deviation of -2.0 mm, adjust the left wheel of the second gear to retreat 2.0mm to the left, and the right wheel of the gear to advance 2.0mm to the left; The vertical deviation is+9.0mm. Considering the change in tooth top clearance, the second gear vertical centerline is lowered by 9.0mm and divided into three levels of rising by 2.0mm and falling by 8.0mm. The third level rising by 2.0mm is converted into support roller adjustment, which means that the support rollers on both sides of the third gear move inward by 3.5 mm, and the second level falling by 8.0mm is converted into support roller adjustment, which means that the support rollers on both sides of the second gear move outward by 14.0mm. Overall, the adjustment is that the support rollers on both sides of the third gear move inward by 3.5 mm, the left side support roller of the second gear moves outward by 16.0mm, and the right side support roller of the second gear moves outward by 12.0mm. After this adjustment, it is calculated that the tooth top clearance increases by 0.2mm, which has a small impact on the tooth top clearance.
During the on-site inspection process, the original roller adjustment plan was not suitable for the following specific reasons:
(1) There are a large number of pits and significant deformation on the surface of the left support roller in second gear, and when measuring the wear of the support roller, it was calculated that the surface of the left support roller in first and second gear is severely worn, while the right support roller in third gear has a large area of pits and crushing deformation (see Figure 7 for details). The damaged support roller causes significant on-site vibration. Considering the abnormality of the support roller, if the support roller is adjusted according to normal conditions, the risk is high, which can easily cause rapid high temperature of the support roller. In severe cases, it can lead to kiln shutdown risk. After adjustment, the damaged support roller still needs to be replaced, and the centerline will still change;
Figure 7: pad adjustment
(2)The horizontal deflection of the left side support roller in first gear reaches 3.5mm, and the vertical deflection of the right side support roller in second gear reaches 4.0mm. The deflection value of the support roller exceeds the reasonable range. If the support roller adjustment method is continued, it will cause high temperature of the support roller bearing, which poses a greater risk;
(3) The working angle of the support roller is calculated to be 60 ° 48 ′ for the second gear. After adjusting according to the original method of adjusting the support roller, the working angle changes to 61 ° 21 ′, approaching the limit value (60 ° ± 1 ° 30 ′), which can easily cause a rapid increase in the temperature of the support roller tile and pose a high risk;
In summary, the conventional method of adjusting the centerline of the support roller can easily lead to kiln adjustment risks, and a new centerline adjustment method is imperative. Through the discussion of our testing personnel, a new centerline adjustment plan has been summarized, which comprehensively adjusts the centerline by replacing the damaged idler and reducing the thickness of the pad. After this adjustment is completed, restarting the kiln operation can still achieve the centerline adjustment goal, and it is safer and less risky.
3 Drawing of a new adjustment plan for the centerline of the rotary kiln
The specific adjustment is to replace the left side support wheel of the second gear with the designed Ø 1500mm support wheel, replace the right side support wheel of the third gear with the designed 1300mm support wheel, replace the 16mm support wheel base pad with a 4mm pad on the left and right sides of the second gear, and replace the 16mm pad with a 10mm pad on the right side of the second gear.
After providing the plan, adjustments were made to the rotary kiln during shutdown. After running for a period of time, it was found that the kiln vibration had significantly improved, and the operation was stable without any other problems. This overall plan provides new ideas for the long-term stable operation of the kiln.
4 Conclusion
By analyzing the equipment situation on the rotary kiln site, we changed the conventional kiln adjustment method and innovatively used the pad adjustment method to adjust the kiln centerline, greatly reducing the adjustment risk of problematic equipment kilns. While taking into account the replacement of support rollers and the problems found on the inspection site, we comprehensively calculated the expected adjustment value of the pad to achieve the normal centerline adjustment effect, providing a new kiln adjustment idea for the new kiln site situation. Ensure the long-term stable operation and efficient production of the rotary kiln.
Transfer from the web
