How it works
Comminution is the controlled application of mechanical stress until particles fracture. A particle stores elastic strain energy as it is loaded; once the local stress exceeds the material’s strength at a flaw, it breaks into fragments. The energy required scales with the new surface area created, which is why producing fine powder costs far more energy than coarse crushing.
How the stress is applied selects the breakage mechanism: compression cleaves particles into a few large fragments, impact shatters them into many with a broader spread, and attrition chips fines off the surface. Real machines combine these, and the dominant mechanism shapes the product — how much the size is reduced and how broad the distribution.
How far the size comes down in a single pass depends on the material and on the stressing: the strength and flaw density of the particles, the stress intensity the machine applies, and how many stress events each particle experiences before it leaves the crushing zone. Small particles carry fewer flaws and are harder to break, which is why every real comminution step produces a distribution of sizes rather than a single one.
The model
Dyssol Pro describes comminution at the population level: the crusher takes the feed particle size distribution and shifts mass from coarse size classes to finer ones — mass-conserving, for every solid compound, at every time point of the dynamic flowsheet.
How far the size comes down follows from the grinding power the machine puts into the material stream: the same power gives a finer product at lower throughput, and a harder material needs more work for the same size reduction.
Which particles break, and where their mass ends up, is set by two material functions: the selection function gives the probability that a particle of a given size is broken, and the breakage function distributes the mass of every broken particle over the finer size classes. On this basis, Dyssol Pro covers the full spectrum of comminution equipment — from jaw crushers to jet mills — and even machine-specific behavior beyond the standard descriptions can be brought into the flowsheet.
Equipment this model can represent
Any process where applied mechanical stress fractures particles to reduce size.
Jaw crushers
Coarse primary crushing of hard rock by compression between a fixed and a moving jaw.
Cone & gyratory crushers
Secondary and tertiary compression crushing; product top size is set by the close-side setting.
Impact crushers & hammer mills
Breakage by high-speed impact, giving strong size reduction with more fines.
Ball, rod & SAG mills
Tumbling mills where grinding media — or, in SAG mills, the coarse ore itself — reduce size by impact and attrition, from primary grinding down to fine wet or dry grinding.
High-pressure grinding rolls (HPGR)
Two counter-rotating rolls compress a particle bed at high pressure; inter-particle stressing breaks the material at low specific energy.
Jet mills
Particle-on-particle impact in a high-velocity gas jet for very fine, contamination-free powder.
Typical engineering studies
What teams investigate with the crusher and mill models.
Product PSD prediction
Predict the product size distribution for a given crusher setting and feed.
Energy & throughput
Relate power input and Bond work index to the achievable product size through Bond’s law.
Mill–classifier circuits
Couple the crusher with a screen or classifier and study recycle load and circuit performance.
Process-parameter sensitivity
Map how the model parameters and feed PSD move the product size and the fines fraction.
Feed-variability studies
See how changes in feed PSD propagate to the product and downstream units.
Model-based Design of Experiments
Screen experiments in simulation before running them on the plant.
Scale-up & optimization
Fit parameters to lab data, then run the validated unit at production throughput and optimize against targets.
Technical FAQ
How do I reduce particle size in a mill without generating too many fines?
Run the mill in closed circuit with a screen or classifier, so particles leave the loop as soon as they reach product size — most fines come from over-grinding material that was already fine enough. Keeping the specific energy per pass moderate and accepting a higher recycle load also shifts breakage toward cleaner fracture. In Dyssol Pro you simulate exactly this recycle loop and tune cut size and recycle ratio against the fines fraction.
What causes overheating during milling?
Only a few percent of the grinding energy actually creates new surface — the rest dissipates as heat, so thermal load rises directly with specific energy input and peaks at fine grinding targets with poor heat removal. Relaxing the fineness target, staged grinding, and better ventilation or cooling are the countermeasures. Dyssol Pro quantifies the specific energy behind that heat load for every operating point in the flowsheet.
How can I choose the right mill for brittle powder?
Brittle materials fracture readily under impact, so hammer, pin, and jet mills are the natural candidates; the final choice follows from target fineness, abrasiveness, and heat sensitivity. In Dyssol Pro you parameterize each candidate and compare the predicted product distribution and specific energy at your throughput.
How do mill speed and grinding media affect particle size?
Higher speed and larger or denser media raise the stress intensity per event and push the product finer — but past the optimum the extra energy mainly produces fines and heat, while media that are too small fail to break the coarse feed at all. Once the breakage model is calibrated, these effects map onto its parameters, so a Dyssol Pro sensitivity study shows the response of the product distribution before you change the machine.
How can I reduce energy consumption in grinding?
Energy demand rises steeply toward fine sizes, so the biggest lever is not grinding finer than the specification requires; the second is a closed circuit that stops over-grinding. Bond’s law links power, grindability, and throughput to the achieved product size — in Dyssol Pro you optimize size target and circuit configuration against specific energy.
Why is my mill product particle size distribution too broad?
In an open circuit every particle sees a different stressing history — some pass barely broken, others are ground repeatedly — which inevitably broadens the product. Narrowing it requires classification: remove particles at product size and return only true oversize. In Dyssol Pro you couple the crusher with a classifier and see directly how cut size and recycle sharpen the distribution.
How do I prevent material buildup inside a crusher?
Buildup is almost always a moisture or stickiness problem: keep the feed moisture below the material’s caking threshold, condition or dry the feed, and avoid fines accumulating in dead zones. Dyssol Pro tracks moisture through the upstream flowsheet, so critical feed conditions can be identified and corrected before material reaches the mill.
What is the difference between impact milling and compression milling?
Compression loads particles slowly between two surfaces and cleaves them into a few coarse fragments at low specific energy; impact loads them abruptly and shatters them into many finer fragments, with more fines and heat. In Dyssol Pro either route is represented by calibrating the crusher model to the machine’s measured product.
How can I model breakage kinetics in a mill?
The standard description is a population balance with two material functions: a selection function for the breakage probability of each size class and a breakage function for the fragment size distribution. That is exactly how Dyssol Pro’s crusher model works — calibrate the functions to milling data, or implement custom kinetics in Model Maker.
How do I scale up milling from lab scale to industrial scale?
Scale up via material functions, not geometry: grindability and the selection–breakage behavior are fitted at lab scale and remain valid at production rates, while machine-specific effects are corrected against pilot data. In Dyssol Pro you fit the model to lab measurements, then run the validated unit at full throughput inside the complete flowsheet.
How do I prevent product contamination during milling?
Contamination comes from wear of media and liners, so the countermeasures are autogenous comminution — jet mills with no grinding media — ceramic or hardened linings, and moderate stress intensities. Dyssol Pro predicts PSD and stream composition through the circuit, so the process design is settled before committing to a contamination-critical machine.
Why is my mill throughput decreasing over time?
The usual suspects are wear — liners and gap opening up, media charge degrading — or a drift toward harder, coarser, or moister feed. In Dyssol Pro you can separate the two: vary the effective machine setting and the feed properties independently and see which reproduces the observed product change.
How does feed particle size affect mill performance?
Coarser feed needs more energy per ton for the same product size and can hit the machine’s capacity limit, while feed already near product size wastes grinding volume. In Dyssol Pro you vary the inlet PSD and see the effect on product size, specific energy, and recycle load directly.
How can I avoid excessive wear in a crusher?
Wear scales with specific energy, feed abrasiveness, and circulating load, so it is limited by running at the coarsest acceptable product size, keeping tramp and oversize material out of the feed, and matching liner hardness to the material. Dyssol Pro computes the specific energy and recycle load of an operating point, so you can steer toward the settings that reduce its main drivers.
What causes agglomeration during fine grinding?
Below a few micrometres, adhesive surface forces exceed the particle weight, so freshly created fines stick to each other and to walls — the practical limit of dry grinding. If re-agglomeration matters for your product, place an agglomeration unit downstream of the crusher in the same Dyssol Pro flowsheet and study the net result.
How do I choose between ball mill, hammer mill, and jet mill?
Rule of thumb: hammer mills for coarse-to-medium brittle feed, ball mills for medium-to-fine grinding at large scale, jet mills for ultra-fine, heat-sensitive, or contamination-critical powders. Dyssol Pro turns the shortlist into numbers by comparing predicted product PSD and specific energy for each candidate at your throughput.
How can I control temperature-sensitive materials during milling?
Limit the specific energy input, remove heat actively — chilled air, inert gas, or cryogenic milling — and avoid over-grinding, which is pure heat generation. Dyssol Pro computes the specific energy behind that heat, so you can minimize the source and size the cooling and gas-handling units in the same flowsheet.
How does classifier integration affect milling efficiency?
A classifier in closed circuit removes product-size particles immediately, so grinding energy goes only into true oversize — throughput rises and over-grinding drops at the same power. In Dyssol Pro you simulate the mill–classifier recycle dynamically and optimize cut size and circulating load.
How do I calculate specific energy consumption in milling?
Bond’s law gives it directly: specific energy equals ten times the material’s work index times the difference between one over the square root of the product’s 80%-passing size and one over the square root of the feed’s 80%-passing size, with energy in kilowatt-hours per tonne. Dyssol Pro applies this relation directly in the flowsheet, linking power, throughput, and achieved product size.
How can I simulate particle breakage and classification in a mill circuit?
Represent the mill with a selection–breakage (population-balance) model and the classifier with a separation curve, connect them with a recycle stream, and solve to steady state. That is a standard Dyssol Pro flowsheet: crusher plus screen or classifier, solved dynamically for product PSD and circulating load.