Ask most plants where their grinding energy leaks and they will point at the mill. Often the real culprit is quieter and sits right after it: the separator. The dynamic classifier is the gatekeeper of the circuit, deciding with every revolution which particles are fine enough to leave as product and which get sent back to be ground again. When it classifies poorly, it makes a costly mistake over and over — returning particles that were already fine enough, forcing the mill to re-grind material that should have left. That is wasted energy and lost throughput hiding in plain sight. iFactory's AI optimization engine reads separator performance in real time and right-sizes classifier speed to the current grindability and fineness target — lifting separator efficiency and cutting return fines.
Grinding Optimization for Cement Plants
AI-Powered Cement Mill Separator and Classifier Efficiency
iFactory reads the separator's real classification performance — cut size, sharpness, and bypass — and tunes classifier speed and air to sharpen the cut. Fewer fines returned, lower circulating load, and fineness held on target as the clinker changes.
A grinding circuit is a loop. The mill grinds, the separator sorts, the coarse returns, and around it goes. The separator's only job is to make a clean split at the right size — send the finished product out and return only what still needs work. Every time it gets that split wrong, it either lets coarse material escape into product, hurting quality, or it sends already-fine particles back to the mill, wasting energy on material that was done. The circulating load balloons, throughput drops, and the specific power creeps up. The separator, not the mill, is quietly setting the ceiling.
Read the Separator by Its Tromp Curve
There is one picture that tells you exactly how well a separator is working: the Tromp curve. For each particle size, it shows the probability that a particle of that size is sent back to the coarse stream. A perfect separator would send everything above the cut size back and everything below it out. Real separators fall short, and the shape of the curve shows precisely how. The goal is a steep curve that drops to near zero at the fine end. iFactory works to move your curve toward that shape.
The Tromp curve: before and after optimization
The shaded band is fine material wrongly sent back to the mill. Sharpen the curve and drop the fine-end floor, and that whole band stops being re-ground for nothing.
Three Numbers Hidden in the Curve
The Tromp curve compresses separator health into three numbers. Together they say whether your classifier is helping the circuit or holding it back.
Cut size (d50)
The size at which a particle is equally likely to leave or return. It sets your fineness, and it must be right-sized to the current clinker grindability and target — not left fixed.
Sets fineness
Sharpness
How steeply the curve rises. A sharp cut cleanly separates coarse from fine; a shallow cut misclassifies in both directions, mixing coarse into product and fines into returns.
Sets cleanliness
Bypass
The fine-end floor of the curve — fines that should have left but were sent back anyway. This is the return-fines tax, paid in re-grinding energy on every pass.
Sets the waste
The Hidden Tax: Return Fines
Bypass is the most expensive number on the curve because it compounds. Every fine particle wrongly returned goes back into the mill, takes up grinding capacity, gets ground it did not need, and lands in the separator again — where some of it bypasses a second time. The reject stream that should be almost entirely coarse is instead carrying a load of finished product in circles.
What is actually in the reject stream
Coarse, correctly returned
Fines bypassed
These bypassed fines are sent back to the mill, re-ground, and re-classified — inflating circulating load and burning energy on cement that was already finished.
How much of your reject stream is finished product going in circles? Book a 30-minute demo and we'll estimate your separator's bypass and what sharpening the cut would return.
Right-Sizing the Cut to the Material
The reason a fixed separator setting cannot win is that the material never sits still. Clinker grindability changes with mineralogy, cooling, and storage, and the fineness target changes with the product. The classifier speed that made a clean cut this morning is wrong by this afternoon. iFactory tracks these shifts and continuously adjusts, so the cut size and sharpness stay right for the material actually in the circuit right now.
Read
Infers cut size, sharpness, and bypass from product fineness, returns, separator speed, air, and power.
Adjust
Moves classifier speed and air to match the current grindability and fineness target.
Sharpen
Steeper cut, lower bypass, on-target fineness, and a lighter circulating load.
What Sharper Classification Delivers
Fixing the separator fixes the whole loop. When the cut is sharp and bypass is low, the mill grinds only what needs grinding, and every number in the circuit moves the right way.
↑
Separator efficiency
a sharper cut, less misclassification
↓
Return fines
lower bypass, lighter circulating load
↓ kWh/t
Grinding energy
no energy spent re-grinding finished cement
On target
Held fineness
cut size tracked to grindability and product
Frequently Asked Questions
Do we need to run Tromp curve tests to use this?
Periodic Tromp curve tests are valuable and remain useful as a reference, but iFactory does not depend on running them constantly. It infers separation performance from the signals the circuit already produces — product fineness, returns, separator speed, air, and power — so it can track cut size, sharpness, and bypass continuously between any physical tests you do.
How is this different from just controlling separator speed?
Setting a speed controls the cut size at one moment. iFactory optimizes for the quality of the separation itself — sharpness and bypass, not just the target fineness — and it re-optimizes as grindability and product change. It coordinates speed with air and the mill so the whole loop stays efficient, rather than chasing fineness with speed alone.
Can it detect separator wear?
Yes. Worn rotor cages, guide vanes, and seals degrade the cut and raise bypass in characteristic ways. Because iFactory continuously tracks the separation performance, a gradual drift toward higher bypass or a softer cut that speed changes no longer fix is a signal that separator condition is deteriorating and maintenance is due.
Does it work for ball mill and VRM circuits?
Yes. Both use dynamic classifiers, and the same principles apply: make a sharp cut at the right size with minimal bypass. The engine is configured to your specific separator and circuit, whether it sits on a ball mill circuit or a vertical roller mill.
How soon do we see the benefit?
Once the engine is configured and reading your circuit, the separation tightens as it takes over classifier optimization, and the energy and throughput gains follow the drop in bypass. The best next step is a demo on your own mill and separator data — bring your process history and any Tromp curve tests, and we will estimate the bypass and return fines you could recover.
Stop Re-Grinding Finished Cement.
See Your Separator's Bypass and What a Sharper Cut Returns
Bring your mill and separator data and any Tromp curve tests. We'll show how much finished product your reject stream is carrying in circles, where classification is losing efficiency, and what right-sizing the cut would return in energy and throughput.
