Analysis of limestone

Quality control for limestone

Stones from calcium carbonate occur on the whole world and are mined in many deposits as limestone. Apart from road construction and building construction also for industrial and agricultural use limestone is required - but with particularly high qualities. A low magnesium oxide (MgO) contents is desired. So far the MgO contents could only be measured in the laboratory by X-ray fluorescence analysis. In-line measurement of the MgO contents was not possible. The device uniSPEC2.2MPL with the relevant software is applied for the in-line analysis of the MgO content.

Measurement of MgO concentration with NIR spectrometry
Quantitative analysis of limestone

For reliable measurement of the MgO content in a process, the NIR device needs to be calibrated quantitatively. In this case that is performed with samples whose composition was determined by X-ray fluorescence analysis in a laboratory.
The transition from pure limestone to a dolomite compound, depending on the MgO contents, is illustrated by the results from NIR measurements. The measurement results can be passed on to process control.

MgO concentration determination by in-line measurement

NIR spectrometer uniSPEC2.2MPL for monitoring:
  • Determination of the statistical MgO contents of the material stream by surface scanning

Application of NIR spectrometer uniSPEC2.2MPL for sorting:
  • Classification of lime stone according to MgO contents
  • Measurement and analysis of every stone in the material stream
  • Pneumatic ejection of the unwanted fractions
  • Optional: in parallel application of colour identification for the identification of impurities (e. g. ferrous)

Technical specification

Measurement taskDetermination of MgO contents of limestone,
installation of the device in an industrial process
Measurement methodNear infrared
Wave length range1100 - 2200 nm
Number of measurement points across the conveyor beltMax. 64
Measurement point size per measurement pointSelectable in the range between 5 mm – 30 mm
Measurement time per single measurement200 – 480 μs selectable, depending on the number of measurement points and the conveyor belt speed
Spectra evaluationPerformed for each single measurementOptional: Object building, given separtion of the stones: Avarage across all measurements on one stone
Combination NIR and colour for identification of impurities (e.g. ferrous stones)Optional
Precondition for pneumatic separation of stonesGiven