The rotary kiln is the core equipment in a cement plant; its working condition directly affects the production efficiency and clinker quality of the cement plant. To keep the rotary kiln in great working condition, we must learn how to maintain it properly during daily production. There are some notices and instructions for the maintenance of a rotary kiln.
The malfunctions that may occur on a cement rotary kiln include:
1) The radial swing of the kiln cylinder may become large in the long-term process, resulting in serious material leakage at the kiln end;
2) The uncontrolled up and down movement of the kiln cylinder during clinker production will affect the stability and the service life of the supporting rollers and tyres;
3) The abnormal vibration of girth gear and rollers and frequent vibration of kiln gear transmission that inhibits normal production;
4) The refractory lining bricks of rotary kiln frequently crack or fall;
5) The transmission torque of the kiln and bearing force of supporting shaft of each tyre unexpectedly change during clinker production.
What May Cause the Kiln Body to Crack?
There are mainly three factors that may cause the cylinder body of the rotary kiln to crack:
1) The corrosion. Corrosive gas generated during the clinker calcining process in the rotary kiln will cause hot and cold brittleness and hot corrosion to the kiln body. In the area rich in corrosive components, the kiln cylinder is easily corroded, resulting in thickness loss and strength decline. Under the action of bending moment for a long time, the cylinder will crack.
2) The deformation of the kiln body. The deformation of the cylinder may appear on the whole kiln body, and the ovality deformation is the most serious at the tyre, especially at the second gear tyre, where the temperature of the kiln is high. If the gap between the tyre and the lining plate of the cylinder is too large, the ovality of the cylinder will increase, resulting in the increase of the compressive stress of the refractory brick, which further causes the fragmentation and falling off of the lining brick.
3) The large straightness deviation of the cylinder. When the kiln is shut down and turned over, the pulling force between the tyre and the supporting roller is large, which may lead to the concentration of temperature stress, welding stress, and working stress, and cause the kiln body to crack.
Where to Look When Routinely Examine the Kiln
It is necessary to check whether there is abnormal noise between the tyre and the base plate, whether the block and retaining ring fall off and crack whether the contact and surface wear between the tyre and the supporting roller are good, whether the supporting roller bears uniform pressure and whether the thrust direction is consistent.
2) Drive Gear
It is mainly to check whether the large and small gears and transmission devices are running smoothly, and whether the radial and axial swing of the girth gear is within the normal range. If the large and small gears are lubricated by spraying system, their reliability should also be checked and judged.
When examining the cylinder of rotary kiln, it is necessary to focus on whether there are cracks at the butt weld of the cylinder and whether the cylinder has serious swing phenomenon when the rotary kiln is working.
4) Temperature of Kiln Shell
The maximum surface temperature of the cylinder should be kept below 380 ℃, and the maximum temperature should not exceed 415 ℃. Otherwise, the strength of the steel plate of the cylinder will be significantly reduced, causing cracking and other risks.
5) Wear Condition of Thrust Rollers
In case of serious wear or damage of the thrust roller, it is necessary to organize and deal with it in time. Excessive clearance between the thrust roller and the tyre will cause axial offset and skew of the tyre, which will lead to the deviation of the bearing force on both sides of the supporting roller, and even serious overheating of the bearing bush.
6) Tangent Plates
Tangent plates are steel plates welded to the kiln shell on the connection parts between tyre and shell. Their function is to increase the rigidity and reduce the wear of the kiln shell. The tangent plates and the kiln shell should be closely connected. The maximum insertion depth of the 0.5mm feeler gauge should not be greater than 100 mm, and the small stop should be closely connected with the plates.
7) Measurement of Cylinder
The straightness and ovality of the cylinder need to be measured and checked during the examination. The cylinder is the kiln body, it is an important part of the rotary kiln. The straightness and the ovality of the cylinder must always be kept in the normal range, or the rotary kiln will not be able to function stably.
Rotary kiln is a kind of large mechanical equipment with complex structure. Once it breaks down during operation, it will cost a large amount of both time and money to repair it.
Therefore, we must pay attention to the daily maintenance of the rotary kiln, operate the device in strict accordance with the production requirements, and carry out regular inspections on it.
AGICO is a top cement equipment supplier in China. We have rich experience in cement rotary kiln projects and provide a series of rotary kiln services including kiln manufacturing, on-site assembling, commissioning, maintenance, and repairing. Please feel free to contact us if you need help with your rotary kiln!