Limestone Analysis

The approximately 970+ power plants that burn oil and coal to produce electricity in America have been cited as a major source of sulfur dioxide (SO2) emissions. This pollutant can irritate the upper respiratory tract and damage lung tissue, as well as yellowing plant leaves and eating away iron, steel, marble and other solid materials. The demand for limestone is increasing due to a legislated requirement for SO2 flue gas desulphurization systems (scrubbers) to be installed in these facilities. Because of this ever-increasing demand, limestone quarry lab technicians are required to take samplings frequently and respond quickly to certify product ready to release by truck or trainload.

This report demonstrates an efficient method for limestone analysis using a pressed pellet technique combined with Rigaku's Primini, a low-powered WDXRF system.

The analysis of light elements, such as sodium and magnesium, can be performed with better sensitivity and overall improved element resolution compared to similar EDXRF units and without the need of higher-powered WDXRF systems. The target area for this procedure are the limestone quarries but down-line companies can also benefit from this routine, as the method satisfies the ASTM repeatability requirements for C1271 (Standard Test Method for X-ray Spectrometric Analysis of Lime and Limestone). Quarries obtain the added bonus of also being able to analyze typical geo-exploration samples for pit development/expansion.

Concentration Ranges:

 SiO2: 0.70 — 3.84%
 Al2O3: 0.12 — 1.25%
 Fe2O3: 0.045 — 1.97%
 CaO: 47.49 — 56.03%
 MgO: 0.15 — 3.63%
 Mn: 0.0067 — 0.19%

Sample preparation:

  • 10% binder to sample weight
  • Combined in Mixermill for 2 minutes (W/C vessel)
  • Poured into aluminum caps
  • Pressed at 20 tons/sq inch for 30 sec
  • Forms 35 mm diameter pellets
  • Sample concentration information

    The sample concentration information was entered into the quant routine. The measuring parameters were established for the analysis routine thorough scanning the highest and lowest element concentrations. From this information we can set the peak locations, backgrounds if required, enter count times and adjust pulse height settings if needed.

    Sample concentration information

    Once the standards have been run, the calibrations are established. In this case an empirical calculation was selected and some minor matrix corrections added. All calibrations achieved a three 9s+ fit.

    Analysis results:

  • Analysis routine runs 6 minutes/sample (loading/unload)
  • Samples were cycled in and out of spectrometer between runs
  • ASTM calculations performed on initial runs and also average of 10 runs
  • Analysis results

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