Thermo-Cognitive Advanced Process Control (TC-APC) models, simulates and optimizes your process in real time to improve yield, conversion and throughput, and reduce energy use, with a quick payback.
Sugar crystallization, vacuum pans
Supersaturation decides the crystal. In seventy years nobody has measured it online.
The one variable that governs whether a crystal grows or a new one forms has been called unmeasurable for seventy years.
It does not have to be measured. It can be estimated.
A narrow zone, and an operator steering by feel.
A strike has to be held inside the metastable zone. Below it, crystals stop growing and the strike stalls. Above it, the solution nucleates on its own and you get new grain you did not ask for. The zone between the two is narrow, it moves as the strike proceeds, and no instrument in the pan reports where you are inside it.
So the pan is run on experience. An operator who has watched thousands of strikes reads the proof, the movement, the boiling pattern and the look of the massecuite, and he is often very good at it. But he is reading proxies for a quantity nobody has been able to derive, the pans do not all behave alike, and he cannot be on every shift.
Model developed and validated against laboratory and plant data
Every excursion above the line makes grain nobody wanted. Every excursion below it stalls the strike and burns steam for nothing. Both are invisible while they are happening.
The operator is not steering badly. He is steering by proxies for a number nobody has been able to produce.
False grain is not a small defect. It is trash you pay to make.
It passes straight through
Fine grain goes through the centrifugal screens and has to be re-melted and re-crystallized. You paid steam and time to make it, and you pay again to unmake it.
It slows everything around it
It thickens the syrup, slows the purging of the good crystals, and clings to clean crystal surfaces where it makes drying harder.
It ends as dust
Through attrition in drying and storage. The white powder on your shoes when you walk into a sugar factory is the same trash, already on the floor.
Formed early in the strike
It conglomerates into a fragile ball grain. Unless it is melted out, at the cost of time and steam, it grows alongside the true grain and takes the mass average down with it.
Formed later in the strike
New grain lowers the mass average and widens the coefficient of variation at the same time, which is a larger loss of quality and yield than either on its own.
This is the same problem as every other application on this site. The variable that determines the money is not measured, so the plant runs a fixed recipe with a margin built into it.
What was built
Supersaturation, decoded from instruments the pan already has.
The claim that supersaturation cannot be derived online is a claim about a function nobody had constructed, not about a quantity that does not exist. So it was constructed, from more than ten thousand laboratory readings taken specifically to map it, combined with the thermodynamics of the sucrose system.
What came out is an estimator that reads what the pan already measures and returns supersaturation continuously, through the strike, without a new analyzer in the vessel.
ss = F ( py, t, Pabs, wts, l, fl )
Purity, temperature, absolute pressure, weight of total solids, level and flow. Every one of them is already on the pan. The work is in the function, not in the instruments.
It holds the zone
Feed and steam are controlled against the estimate, so the strike stays inside the metastable band instead of crossing it and being corrected afterward.
It works without the water valve
Strikes are managed without reaching for water to kill a nucleation that should not have been allowed to start.
It improves with use
Each strike adds to what the model knows about that pan, the incoming liquor and the way that vessel behaves, which is not the same as the pan beside it.
Where this actually stands
The model exists. It was built on more than ten thousand laboratory readings and has been validated against laboratory and plant data. That is a real thing and it is not the same as a deployment.
We have one deployment and it is not this one. It is fourteen carbonation towers in a soda ash plant, named, with a signed certificate and a man who takes reference calls. Everything on this page rests on that being true, so we are not going to blur the two. The deployment, and the letter.
What this cannot do.
It cannot improve poor liquor
Holding the zone gets the best crystal the liquor in front of it can give. It does not get you better liquor, and it will not hide a juice purification problem upstream.
It cannot fix a pan with bad circulation
If the massecuite is not moving, the estimate will report accurately that conditions differ across the vessel. That is worth knowing and it is a mechanical problem, not a control one.
It does not replace your laboratory
Your purity and grain measurements remain the reference. The estimate is checked against them and the bias between the two is shown.
It does not set your grain specification
What mass average and coefficient of variation you are aiming at is your decision and your customer's. The engine holds whatever target you set.
The mark
Find the optimum. Hold it while it moves.
The curve is a yield or selectivity response. The amber point is the optimum, and the dashed drop is where it sits on the operating axis.
The second half of the line is the part that matters. Finding an optimum is a study, and studies end up in drawers. Holding one while the feed, the fouling, the weather and the wear keep moving it is a control problem, and that is the work.
Start with one pan
Send strike data from one vacuum pan with the laboratory results beside it
We will tell you how often the strike is leaving the zone and what it is costing in boiling time and reprocessing, with the uncertainty stated openly. No charge, and no commitment either way.
projects@yielddynamics.in Talk to IIT Bombay engineers Call +91 94230 07004Monday to Saturday, 9:00 to 19:00 IST
Or look at what we have actually run
Fourteen carbonation towers, validated over six months
The one deployment we own, named, with the signed letter and the General Manager who coordinated it and still takes reference calls.