Cement rotary kiln is the core equipment of cement production line. In the daily production process, we will encounter a series of equipment faults caused by equipment itself or improper operation. If not handled properly and in time, it will cause considerable economic losses to the cement plant. Therefore, when the above problems arise, we should have correct judgment and be able to choose the best solution. Only in this way can the production system of dry method cement rotary kiln run safely, smoothly, with low energy consumption and high efficiency.
Generally speaking, the reason why a cement rotary kiln system can run stable and have high production efficiency is usually due to the continuous exploration, research and optimization of technical personnel. They effectively analyze and solve every system problem, at the same time, optimize the rotary kiln system to ensure that the problem will not occur next time, which lays the foundation for future stable production. Next, we will introduce some common faults and their preventive measures in the production system of the dry process cement kiln.
Large Pressure Fluctuation of Roots Fan
Reasons: in the normal operation process, the pressure fluctuation of Roots blower at kiln head or kiln tail should be controlled within 100 Pa. The purpose is to make pulverized coal burn uniformly, steadily and quickly, so as to release its maximum heat to ensure the stability of the kiln heating system. But because of the following two reasons: (1) the filter cotton at the feeding port of Roots blower is too dirty and exceed its service life, leading to the difficulty of intake when Roots blower works, then the outlet pressure will be low and cause a large fluctuation. (2) The wrong Roots blower model selection. When Roots blower is running at full speed, the pressure will fluctuate if the pulverized coal can’t be fed into the kiln at reasonable wind speed.
When the filter cotton is very dirty, the most direct performance is that the pressure fluctuation of coal feeding at the kiln head becomes larger (long-term fluctuation range: 2,000 Pa), and the outlet pressure of Roots blower in operation will be as low as 28,000 Pa. However, after the filter cotton is replaced or cleaned by the workers, the pressure of Roots blower increases instantaneously (33 000 Pa), and the fluctuation of outlet pressure is also greatly reduced.
Result: when the pressure of Roots blower at the kiln head fluctuates greatly, the continuous stability of coal feeding will be affected, and the pulverized coal will not burn completely in the kiln. Therefore, the heat output in the kiln will be unstable, and the output of the rotary kiln will also reduce.
Preventive measures: (1) Reduce the dust content in the air so that the roots blower can breathe in clean air while working. (2) Clean up the filter cotton of Roots blower regularly. (3) Do the regular maintenance of the Roots blower. (4) Make a correct model selection of Roots blower. We’d better select a Roots blower with large power and change it to frequency converter control, so as to ensure the normal input of pulverized coal and reduce the unnecessary power consumption.
The Rapid Current Decreasing of Rotary Kiln Motor
Cause: In general, the motor current track of rotary kiln is very stable, and the fluctuation range is small (the general fluctuation value is between 100 and 200A). This kind of current can reflect the operation condition of rotary kiln well. However, due to the change of raw material composition and improper temperature control at the outlet of the decomposition furnace, the motor current of the rotary kiln will decline slowly at first, then rapidly, appearing the material channeling phenomenon.
The current value is usually about 1 000-1 200 A when the motor current track of the rotary kiln is normal. However, in some cases, when the raw material feeding quantity does not change, the outlet temperature of the decomposition furnace slowly decreases. After we increase the coal feeding quantity at the kiln tail, the outlet temperature does not rise, and the motor current of the rotary kiln begin decreases. The reason for this phenomenon may be the change of raw meal feeding rate. Because the saturation ratio of raw meal is high and the outlet temperature of decomposition furnace decreases, a lot of low-temperature raw material enters the kiln, which leads to the current drop and eventually material channeling.
Result: it is a terrible thing that the material channeling occurs in the rotary kiln system. It not only affects the output and quality of the rotary kiln but also prone to personal injury and equipment damage. The consequences are very serious.
Preventive measures: (1) Strengthen operators’ technical level. When the current changes abnormally, operators need to analyze carefully and judge accurately. (2) The raw material feeding rate should be stabilized in a reasonable range. And the raw material should be rationally homogenized and proportioned to avoid material mixing and material fixed-point distribution.