Process and apparatus for calcination of gypsum
A calcination process where near-infrared spectroscopy measures moisture on both the raw gypsum feed and the calcined stucco stream, and the burner fire rate is adjusted in a closed loop from both signals.
- Assignee
- Knauf Gips KG
- Inventors
- Olaf Johannsmann, Rainer Schulte, Juan José Ruiz
- Jurisdiction
- WIPO (PCT)
- Filed
- 2016-11-18
- Published
- 2018-05-24
- Priority
- 2016-11-18
Kettle calcination is a moving target: incoming raw gypsum moisture varies hour by hour with quarry weather and stockpile depth. A fixed fire rate therefore produces a calcined stucco whose water content — the practical proxy for the ratio between hemihydrate, soluble anhydrite and residual dihydrate — drifts through the day.
This patent inserts a live measurement on both ends of the kettle and uses both signals to drive the burner.
- 01A continuous feed of raw gypsum enters the calcination unit.
- 02An NIR sensor measures the water content of the raw gypsum in the feed stream.
- 03The calcination unit fires at an adjustable fire rate; a second NIR sensor measures the water content of the calcined gypsum on the exit stream.
- 04The controller adjusts the fire rate on the basis of both moisture measurements, keeping calcined moisture inside a selected setpoint range continuously.
| Parameter | Value | Source |
|---|---|---|
| Feed sensor | NIR moisture on raw gypsum, continuous | claim 1 |
| Product sensor | NIR moisture on calcined stucco, continuous | claim 1 |
| Control variable | fire rate of the calciner burner | claim 1 |
| Control law | fire rate adjusted from raw feed and calcined product moisture | abstract |
- 01NIR probes on hot dusty streams are not maintenance-free — a proper install includes a purge system and a scheduled window-cleaning routine, otherwise the feedback loop starts lying to itself.
- 02The control benefit shows up as a narrower distribution of calcined moisture — worth trending against your existing DTA / TGA quality checks.
- 03Because the loop reacts on the feed side too, upstream stockpile management (roof cover, blend piles) still matters — the loop compensates, it does not cancel raw variability for free.
The invention pertains to a process for modifying gypsum, wherein a continuous feed of raw gypsum is provided; the water content of the raw gypsum is determined in the continuous feed by near infrared spectroscopy (NIR) measurement; the raw gypsum is calcined in a calcination unit at a fire rate to remove water from the raw gypsum and to obtain a continuous feed of calcined gypsum having a water content within a selected range; a water content of the calcined gypsum is determined by near infrared spectroscopy, and the fire rate is adjusted based on the water content of the raw gypsum and of the calcined gypsum. Further, the invention pertains to an apparatus for performing said process.
Process for dehydrating gypsum, wherein a continuous feed of raw gypsum is provided; the raw gypsum is calcined in a calcination unit at a fire rate to remove water from the raw gypsum and to obtain a continuous feed of calcined gypsum having a water content within a selected range; a water content of the calcined gypsum is determined by near infrared spectroscopy, and the fire rate is adjusted based on the water content of the calcined gypsum.
Further claims, drawings, prosecution history and legal status: see the official record.
- [1]WO 2018/091062 A1 — Process and apparatus for calcination of gypsum — Google Patents · 2018-05-24