I. Distinguishing between high- and low-concentration ranges (applicable to non-ferrous metals and gold ores)
Optimal concentration: 68%–74% for primary grinding; 62%–68% for secondary fine grinding.
Excessively high concentration: >75%
Excessively low concentration: <60%

II. Comprehensive impacts of excessively high grinding concentration (slurry too thick)
1. Impact on the grinding process itself
High slurry viscosity causes ore particles to adhere to the surfaces of steel balls and liners; this enhances the effective grinding action of the media, improving grinding efficiency and reducing specific energy consumption, resulting in finer grinding within the same timeframe.
Slurry fluidity deteriorates, hindering discharge from the ball mill and easily clogging discharge ports and return sand pipes; coarse sand accumulates in the classifier, causing a surge in return sand volume and a vicious cycle of over-grinding.
Fine slimes cannot be discharged promptly, leading to over-pulverization of the ore and the generation of excessive ultra-fine slime particles.
2. Impact on classification operations (spiral classifiers / hydrocyclones)
Thick slurry slows particle settling speeds, causing coarse particles to escape into the overflow and significantly reducing classification efficiency; coarse sand that should have settled out enters the flotation circuit via the overflow, resulting in substandard particle sizes for flotation.
Hydrocyclone underflow concentration becomes excessively high, leading to clogging; overflow concentration and particle size fluctuate drastically, destabilizing system operating conditions.
3. Impact on core flotation performance indicators (critical)
Over-grinding generates large amounts of slime: the slime indiscriminately adsorbs collectors, causing a sharp rise in reagent consumption and production costs.
Fine slimes coat the surfaces of valuable minerals, inhibiting bubble attachment and significantly reducing the recovery rates of gold, copper, lead, and zinc.
Froth becomes sticky and slow to break, making skimming difficult; concentrate becomes contaminated with significant amounts of gangue, lowering the concentrate grade.
Excessive slurry concentration impairs aeration; the pulp surface in the flotation cell becomes turbulent with uneven bubble sizes, reducing separation selectivity. 4. Other negative impacts
Accelerated wear on slurry pipelines and sand pumps, leading to frequent pump and pipeline blockages;
Increased load on dewatering operations, difficulty in thickener settling, and turbid overflow water.
III. Comprehensive impacts of excessively low grinding concentration (slurry that is too dilute)
1. Impact on the grinding process itself
High water content in the slurry separates steel balls and increases the cushioning effect of the ore; this weakens grinding impact and friction, reduces grinding efficiency, and prevents fine grinding.
At the same feed rate, product particle size becomes coarser, and valuable minerals fail to achieve sufficient liberation.
Processing the same ore requires larger mill volume, leading to increased specific power and steel consumption.
2. Impact on classification operations
Dilute slurry causes particles to settle too rapidly; coarse sand sinks quickly into the underflow (recirculating load), resulting in coarser overflow fineness and an increased classification recirculating load.
Cyclone overflow volume is high with very low concentration, increasing the processing pressure on classification equipment.
3. Impact on key flotation performance indicators
Low solid content in the slurry means fewer valuable mineral particles per unit volume; effective flotation throughput drops, resulting in wasted equipment capacity.
Reagents are heavily diluted, leading to insufficient concentration in the slurry and weakened collecting or depressing effects; achieving target separation results requires increased reagent dosage, raising costs.
Bubble carrying capacity for mineral particles decreases, resulting in less mineral flotation, increased metal loss in tailings, and reduced recovery rates.
The froth layer becomes thin and prone to collapse, leading to low concentrate yield and poor production stability.
4. Other negative impacts
Large volumes of water enter thickening and pressure filtration stages, overloading dewatering equipment and disrupting the water balance in the clear water circulation system;
Dilute slurry causes scouring of pipelines and equipment, leading to increased leakage and spillage. IV. Benefits of Maintaining Concentration Within an Optimal Range
Adequate mineral liberation is achieved with a uniform particle size distribution, avoiding significant over-grinding or under-grinding;
High classification efficiency and stable overflow particle size ensure the flotation circuit receives feed slurry that meets specifications;
Flotation froth exhibits optimal thickness and good selectivity, resulting in high concentrate grades, low tailings grades, and maximized metal recovery;
Consumption of reagents, steel grinding media, and energy (electricity and water) is kept at low levels;
Operational stability is maintained across the entire process—including classification, flotation, and dewatering—minimizing the risk of pipe or pump blockages and reducing equipment failure rates.