Views: 0 Author: Site Editor Publish Time: 2026-09-24 Origin: Site
In many concentrators, when the accounts are carefully examined, the grinding section accounts for 50%–60% of total power consumption—making it a true “power hog.” This proportion is typical for sulphide ore concentrators using a conventional crushing–grinding–flotation circuit. Autogenous grinding circuits, gravity concentrators, and magnetic separation plants may differ because of their different process structures, but the general pattern holds: grinding is the single largest energy consumer in most mineral processing operations.
Most people accept this as inevitable. After all, to liberate valuable minerals from the ore, the ore must be ground fine—and grinding consumes power. But after visiting numerous sites, one finds that concentrators of the same scale treating the same type of ore can differ by 20%–30% in grinding power consumption per tonne of ore. This difference is not solely due to ore hardness or throughput fluctuations. To a large extent, it comes from hidden waste caused by inefficient equipment and poor operating matching.
Much of this electricity is simply wasted—paid for but never converted into useful grinding work. The following sections examine the four most common sources of hidden waste in grinding circuits, the on-site signals that reveal them, and the practical steps to eliminate them.
In many concentrators, mill liners are replaced only when they crack or break. The prevailing attitude is, “If it isn’t broken, it can still be used.” But this ignores a fundamental mechanism of mill operation: once liners are worn flat and lifter bars are worn down, the ball throw height drops directly, and the impact and grinding force weaken greatly.
The equipment appears to still be running. The motor current may look normal. But the effective grinding work has already fallen, while power consumption has not decreased. The result is electricity wasted without corresponding throughput—a classic hidden loss.
This type of loss is especially typical in grate ball mills with high-manganese steel liners processing medium-hard sulphide ore. For highly abrasive ores, liners wear even faster, and the loss appears earlier in the wear cycle.
On-site signals: The mill sound becomes dull, with a weak impact feel. The main motor current does not look low, but mill throughput drops and fineness keeps running coarse.
Power loss: When lifter bar height wears to two-thirds of its original height—exceeding the normal wear limit—grinding efficiency drops by 15%–20%, and power consumption per tonne of ore rises by 10%–15%. For a medium-sized concentrator with a typical grinding unit consumption of 10–15 kWh/t, this is equivalent to an extra 1.5–2 kWh consumed for every tonne ground.
Quick judgment:
Listen to the sound: the impact sound changes from crisp to dull, and the rhythm becomes unclear.
Check the data: current is normal, but both throughput and fineness decline.
Shut down and inspect: lifter bar height has worn by more than one-third of the original height.
Optimization direction: Inspect regularly according to the wear cycle, and replace promptly when the wear limit is reached. For highly abrasive ores, give priority to high-manganese steel or rubber liners, and match the selection to the ore properties.
Energy-saving benefit: Under conditions of severe liner wear approaching failure, after replacing with liners that meet specifications, grinding power consumption can drop by 8%–12%, with a simultaneous increase in mill throughput.
In many on-site grinding adjustments, the first reaction is to add steel balls or add larger balls. The assumption is that the more and larger the balls, the finer the grinding. But this assumption is often wrong.
If the size distribution is incorrect and the ratio of large to small balls is imbalanced, either coarse particles cannot be ground, or fine particles are overground. The current may appear very high, but effective grinding work is very low, and power is wasted entirely on balls colliding with each other and striking empty. The mill is busy, but it is not doing useful work.
The optimal ball charge differs greatly between primary and secondary grinding, and closed-circuit flowsheets require much greater ball-charge stability than open-circuit flowsheets. The harder the ore, the more sensitive power consumption is to ball charge size distribution.
On-site signals: Mill current is on the high side, but discharge fineness alternates between coarse and fine. Although quite a few steel balls are added, mill throughput does not increase.
Power loss: When the ball charge size distribution clearly deviates from the optimal range, power consumption per tonne of ore rises by 8%–12%, and fineness often still fails to meet target.
Quick judgment:
Screen the mill discharge product; the size distribution is large at both ends and small in the middle.
Shut down and clean out the mill for inspection; the proportion of broken balls and deformed small balls is too high.
Optimization direction: Determine the ball charge scheme according to ore hardness, feed size, and target fineness. Regularly add qualified steel balls, and regularly clean out the mill to screen out broken and deformed balls. The cleanout cycle should be adjusted according to ore abrasiveness; for medium-hard sulphide ore it can be carried out quarterly, while for highly abrasive ore it should be shortened to 1–2 months.
Energy-saving benefit: If the original ball charge is clearly imbalanced and the proportion of broken balls is high, after optimization grinding power consumption can drop by 5%–10%, and fineness stability improves greatly.
Many people think that as long as the mill is turning, power consumption is roughly the same, and feeding a little more or less makes little difference. This is a costly misconception.
A ball mill has an optimal load range. Too little feed means “starving,” with steel balls striking empty, and power spent on collisions among themselves. Too much feed means “overfeeding,” with the mill bogging and rotating sluggishly, and grinding efficiency plummeting. Both situations waste power—often dramatically.
From a professional perspective, grinding load is measured mainly by filling degree, ore-to-ball ratio, and grinding density. For conventional primary closed-circuit grinding, the optimal filling degree is usually 35%–45%, corresponding to a throughput generally 70%–90% of the design value. However, the specific values need to be calibrated in combination with ore grindability tests; there is no universal fixed standard.
On-site signals:
Load too low: current is on the high side, throughput is low, and power consumption per tonne of ore soars.
Load too high: current drops, discharge runs coarse, and the mill may even bog and spit ore.
Power loss: When the actual load deviates from the optimal range by 20%, power consumption per tonne of ore rises by 10%–18%. When the load is too low, empty-striking losses are more prominent, and the increase in power consumption is usually higher than when the load is too high.
Quick judgment: Cross-verify using feed rate, current, and discharge fineness. For conventional closed-circuit grinding, the reasonable throughput range is usually 70%–90% of design throughput, for empirical reference only.
Optimization direction: According to mill specifications and ore properties, lock in the optimal feed rate and grinding density. Stabilize feeding and avoid large fluctuations.
Energy-saving benefit: If the original load deviates greatly from the optimal range, after optimized matching, power consumption per tonne of ore can drop by 10%–15%, and throughput can also increase by 5%–10%.
When there are no obvious equipment faults such as cracked liners or severe bogging, it is recommended to troubleshoot in order of lowest to highest cost and easiest to hardest adjustment, so as to avoid detours. If obvious faults have already occurred, address the fault point first.
Step 1: Stabilize the load first. Check the feed rate and grinding density, bring the load back into the optimal range, stabilize feeding, and avoid large fluctuations. This is the lowest-cost and fastest-acting adjustment.
Step 2: Then adjust the ball charge. Inspect the steel ball size distribution, screen out broken balls, add steel balls of suitable sizes as required, and carry out regular addition and regular mill cleanout.
Step 3: Finally check the liners. After ruling out the first two factors, if grinding efficiency is still low and power consumption still high, shut down and inspect liner wear, and replace when the limit is reached.
This sequence ensures that the cheapest and most easily corrected problems are addressed first, avoiding unnecessary shutdowns or parts replacement before simpler causes have been eliminated.
The following is an example calculation for a given operating condition. Actual energy-saving benefits depend on the original equipment condition, ore properties, and management level.
Take a medium-sized sulphide ore concentrator processing 2,000 tonnes per day as an example. Original comprehensive power consumption is 24 kWh/t, grinding accounts for 60%, i.e., grinding unit consumption is 14.4 kWh/t. Conservatively assuming a 15% reduction in grinding power consumption after optimization—under conditions where the original equipment has obvious waste:
Power saved per tonne of ore: 14.4 × 15% = 2.16 kWh/t
Daily power saved: 2,000 t × 2.16 kWh/t = 4,320 kWh
Daily electricity cost savings: 4,320 kWh × 0.6 yuan/kWh = 2,592 yuan
Annual electricity cost savings: 2,592 yuan × 330 days ≈ 855,000 yuan
Note that the above calculation only covers the direct benefit of electricity cost savings. It does not include the replacement cost of spare parts such as liners and steel balls, nor does it include the benefit from improved beneficiation recovery brought by higher mill throughput and stable fineness. In practice, the total economic benefit of a well-executed grinding optimization program is often significantly higher.
Grinding is the largest energy consumer in most concentrators, but much of that energy is wasted through liner wear, poor ball charge design, and mismatched mill loading. These are not inevitable costs—they are correctable inefficiencies. By listening to the mill, watching the data, and following a logical troubleshooting sequence, plants can reduce grinding power consumption by 5%–15% or more, while simultaneously improving throughput and fineness stability. The savings are not merely incremental; they can amount to hundreds of thousands of yuan per year for a medium-sized operation. In an industry where margins are increasingly tight, eliminating hidden grinding waste is one of the most direct and reliable paths to improved profitability.
