2020-08-15 03:57:54 1038
It is ideal that the continuous crushing system is in dynamic balance. Once the system is unstable, the front and back processes will be affected.
When the system is in dynamic balance, the working process is a quasi-stable random process, except for various In addition to some fluctuations caused by random interference, the average value of each variable does not change with time. Taking wet open-circuit ball milling as an example, the distribution of the medium along the length of the mill and the energy input into the mill maintain the axial gradient of uniform material particle size distribution. Unchanged. Therefore, under the condition of stable input (feed water, feed, granularity, grindability), the system will have a stable output (production, product concentration, particle size distribution and working noise). Any unstable external input will cause system status Change, if the input fluctuation of the system is lower than its processing capacity, the fluctuation of the system status will only cause the fluctuation of the output (changes in output and particle size distribution), and the system itself will automatically reach a new dynamic equilibrium point. The amount of external input material is greater than When the system is capable of processing, the medium cannot grind and discharge the materials in time, and the accumulation of materials further weakens the grinding effect of the medium, so that the accumulation of materials in the mill gradually increases. This automatically growing chain of causality makes the ball milling process It enters a malignant self-reproductive state and loses stability.
This self-uniformity and self-stability trend of the ball mill system can be explained from the second law of general thermodynamics. As an independent system, no matter how internal changes are made, its moisture content always tends Extremely large, this makes the system become uniform and disordered. However, under the conditions of stable water supply and energy input outside the system, the system can continuously absorb negative entropy. When the two reach a balance, the system can rely on Its inherent law is in a stable state. The loss of stability of the ball mill indicates the rapid collapse of the original stable state of the system. This is the phenomenon of belly bulging that occurs from time to time in the ball milling operation. From the commonality of the self-reproduction process, the ball mill system also has a critical condition, namely The maximum processing capacity of the mill (the maximum processing capacity is not a fixed value, but the area determined by the operating conditions). When the system input exceeds this critical condition, self-reproduction will occur. The passive solution is to stop Input to interrupt the above-mentioned causal chain of automatic growth.
The critical condition of the maximum processing capacity of the ball mill system depends on the system structure and stability. The more stable the system, the greater the anti-disturbance ability, and the corresponding critical condition is also In actual operation, in order to avoid the phenomenon of belly bulging, the system has to work under critical conditions, which makes the working capacity of the mill not fully utilized. In the long-term stable working process of the ball mill system, the medium and lining The plate is constantly worn, and its grinding capacity is gradually attenuated, and the working state of the entire system is drifting. For medium wear, the method of intermittently supplementing the medium in actual operation is often used. From the viewpoint of stable system working state, this The method will obviously cause a sudden change in the system state and cause a large fluctuation in the output.
We can use a scheme of non-stopping and short time intervals according to the mediums wear rate to suppress the state drift and ensure the system stability. It is difficult to compensate for liner wear without stopping the machine. It can be said that although the drift of the ball mill system is inevitable, it can be artificially slowed down. Therefore, it is very necessary to grasp the adjustment input of the mills working state in time. This is an ideal method.
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