Principles for adding rods to coal mills
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What are the principles for adding rods to a coal grinder? How often should it be added, and what is the basis for adding it?
The principle for adding rods is \"small at both ends and large in the middle.\"
2# GSP: Could you explain in detail what it means by small at both ends and large in the middle?
It means that the number of rods of medium size is the highest, while the numbers of rods of the smallest and largest sizes are lower.
When added for the first time in a 3:4:3 ratio, the diameters usually are 50, 65, and 75. On a weight basis, after an initial trial grinding with 30%, the amount of steel rods is gradually increased to 90%. Add it to the design rod addition amount after one month. During use, replenishing rods is primarily done to check for any broken rods and to ensure that the particle size range of the coal slurry at the mill outlet meets the specified standards.
I agree with the view above; when choosing rods, it mainly depends on the particle size distribution – if there are too many large particles, add more 50-size rods, and if there are too many small particles, add more 75-size rods.
After the mill has been operating for a period of time, the steel rods experience wear to varying degrees. After new rods are added and the mill continues to operate, both the old and new rods continue to wear, resulting in a gradient. When replenishing the rods again, the severely worn thin rods are usually removed and thicker rods are added to maintain the gradient.
For 65 bar, it is usually 55-60-70, with these amounts added in a 3-4-3 ratio. Depending on the quality of the coal, if a more precise adjustment is needed, a bit more of the 55-grade material can be used; if a coarser texture is required, then some 70-grade material can be added
I would like to ask what the feeding rate is for the new grinder with dimensions of Φ4300mm*6000mm. They say it’s 30% of full capacity, so what is full capacity? Our steel rods are of sizes 55, 65, and 75; how much reinforcement should be added? I would appreciate some advice from the experts here.
With our company’s mills, when 50% of the rods are added at once, a strange phenomenon occurs: all the rods become scattered inside, in a chaotic mess; some of them are even almost touching the feed inlet.
This phenomenon is known as the “random rod phenomenon.” There are three reasons for this: first, the rods were not installed properly when adding them, and the steel rods were not arranged neatly； Secondly, the quality of the steel rods is substandard, with bent rods included ； Third, long-term idling or turning of the shaft.