The cement rotary kiln is the core equipment of the cement production line. In the daily production process, we will encounter a series of equipment faults caused by the 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 a 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 stably and have high production efficiency is usually due to the continuous exploration, research, and optimization by technical personnel. They effectively analyze and solve every system problem; at the same time, they 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 the Roots blower at the 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 for the following two reasons: (1) the filter cotton at the feeding port of the Roots blower is too dirty and has exceeded its service life, leading to difficulty in intake when the Roots blower works; then the outlet pressure will be low and cause large fluctuations. (2) The wrong Roots blower model selection. When the Roots blower is running at full speed, the pressure will fluctuate if the pulverized coal can’t be fed into the kiln at a reasonable wind speed.
When the filter cotton is very dirty, the most direct performance effect 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 the 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 the Roots blower increases instantaneously (33 000 Pa), and the fluctuation of outlet pressure is also greatly reduced.
Result: When the pressure of the 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 be reduced.
Preventive measures: (1) Reduce the dust content in the air so that the Roots blower can breathe in clean air while working. (2) Clean the filter cotton of the Roots blower regularly. (3) Do the regular maintenance of the Roots blower. (4) Make a correct model selection of the 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 unnecessary power consumption.
The Rapid Current Decreasing of Rotary Kiln Motor
Cause: In general, the motor current of the 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 operating condition of the rotary kiln well. However, due to changes in 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, indicating 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 begins to decrease. The reason for this phenomenon may be the change in the raw meal feeding rate. Because the saturation ratio of raw meal is high and the outlet temperature of the 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 material channeling occurs in the rotary kiln system. It not only affects the output and quality of the rotary kiln but is 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. The raw material should be rationally homogenized and proportioned to avoid material mixing and fixed-point distribution.
