Lime and gypsum plants: kilns and dryers run on late lab values

Stone and fuel quality vary in lime kilns

What happens. The limestone from the quarry changes in size, density and purity from one delivery to the next, and so does the fuel. The kiln burns whatever arrives, with settings chosen for an average.

What it costs. Fuel per tonne of lime and the quality of the lime. When the stone is more difficult, the kiln needs more fuel or leaves residual carbonate in the product.

Why the usual fix fails. Operators add fuel margin to be safe, which burns the lime harder than needed. Changing the settings by hand for every delivery is not possible in a shift.

How a fixed-price remote diagnosis checks it. From kiln logs (fuel, temperatures, air, exhaust gas), the stone and fuel data and lab results I estimate the product quality and check whether predictive kiln control could keep quality with less fuel. The fixed-price remote diagnosis tells you what it would take on your kiln.

Background: Predictive control of process plants

Residual carbonate in lime is known only from the lab

What happens. The residual carbonate in the lime shows how fully the stone was burnt. It is measured in the lab on samples, and the result arrives well after the lime has left the kiln.

What it costs. Fuel, because kilns are fired harder to be on the safe side, and off-spec lime if they are not. The kiln runs for hours before the lab value tells the crew what happened.

Why the usual fix fails. More frequent sampling takes lab time and still gives a late answer. A continuous analyser on the product is difficult in the hot, dusty discharge.

How a fixed-price remote diagnosis checks it. From kiln data and the lab values you already have I estimate the residual carbonate continuously and check how well it follows the lab. The fixed-price remote diagnosis answers whether a computed value is accurate enough to steer the burn.

Background: Computed measurements

The feed size to the lime kiln changes

What happens. The size distribution of the stone changes with the quarry face, the crusher and the screen. Fine material blocks gas flow, coarse stone burns through slowly.

What it costs. Fuel and quality: the same settings give a different result with a different feed. Uneven gas flow in the kiln creates hot and cold zones.

Why the usual fix fails. Re-screening costs yield. Operators change air and fuel by feel when the pressure drop or the exhaust temperature changes, which is after the effect.

How a fixed-price remote diagnosis checks it. From pressure-drop trends, temperatures, feed records and quality values I check how strongly feed size shows in the kiln data and whether adaptive control could follow it. The fixed-price remote diagnosis tells you if that is realistic for your kiln.

Background: Control that adapts to drift and wear

Combined water in calcined gypsum is known only from the lab

What happens. When gypsum is calcined, the amount of water that stays in the product decides how it sets later. It is measured on samples in the lab, after the batch has already moved on.

What it costs. Setting problems in plaster and board: too fast, too slow or uneven. Corrections come hours late and the material in between is off.

Why the usual fix fails. Setting the calciner conservatively gives a safe but costly product. Spot samples cannot follow changes in the feed gypsum.

How a fixed-price remote diagnosis checks it. From calciner temperatures, residence times, feed data and lab values I estimate the combined water of the product continuously. The fixed-price remote diagnosis shows whether the computed value is good enough to steer the calciner and where the lab stays necessary.

Background: Computed measurements

Plasterboard dryers dry for the worst board

What happens. The dryer runs at a temperature and speed that make even the wettest, thickest board dry. Most boards are drier and sit in hot air longer than they need to.

What it costs. Gas, which is the largest cost of board drying, and line speed. Over-drying also harms the board surface and the board’s core.

Why the usual fix fails. A moisture sensor at the exit shows what has already happened. Reducing the setting by hand holds until a wet batch arrives and boards leave damp.

How a fixed-price remote diagnosis checks it. From dryer temperatures, line speed, gas use and exit moisture readings I estimate the moisture of the boards inside the dryer and check how much heat is wasted. The fixed-price remote diagnosis tells you whether a computed board moisture could lead the dryer and what it would take.

Background: Computed measurements

The gypsum supply changes as coal power ends

What happens. A large part of the gypsum used for plaster and board has come from flue-gas desulphurisation at coal power plants. As these plants close (ingenieur.de), natural gypsum and recycled gypsum make up a growing share, and new quarries are contested.

What it costs. A changing mix of natural and recycled gypsum means that calcination and board quality vary with the origin, purity and moisture of the feed.

Why the usual fix fails. Settings that were tuned for the very uniform flue-gas gypsum do not fit each new source. Testing each mix in the lab and adjusting by hand takes time and ends in conservative settings.

How a fixed-price remote diagnosis checks it. From feed analyses, calciner and board-line data I check how much each raw material moves the process and whether properties can be computed in time to adapt the control. The fixed-price remote diagnosis shows how far adaptive calcination and board-line control could cope with a changing mix.

Background: Control that adapts to drift and wear