Rapid Compositional Analysis of Cement Using EDXRF

In the cement industry, it is important to closely monitor production stages on a routine basis to ensure meeting the demands on composition uniformity and overall product quality. In cement manufacturing, the S2 RANGER is a suitable supplementary system for process control. The pulse processing performance and the energy resolution of the XFlash detector enable the S2 RANGER to measure not just the usual cement compounds in pellets but also to directly calculate cement modules, such as the Bogue compounds, C3S, C2S, C3A, and C4AF, and the ratios LSF, SM, and AM, used for process control.

Cement calibrations based on pressed pellets vary considerably from plant to plant; hence it is important that calibration is always fine-tuned to the in-house cement standards and preparation. This report describes the analytical performance of the S2 RANGER with XFlash detector for pressed powder pellets of cements.

Instrumentation

The S2 RANGER is a comprehensive benchtop energy-dispersive X-ray fluorescence (EDXRF) spectrometer with TouchControl, which is a convenient touch screen interface. The system needs only electrical power. Its distinct XFlash detector easily processes input count rates of 100,000 cps while enabling superior resolution, low dead time and high signal stability.

Sample Preparation

The cement samples used for this report were formed as powder pellets of 35 mm in diameter in steel rings. About 12.2 g cement was ground with three grinding aid tablet of approximately 0.93 g and pressed in rings with the help of a Polysius Polab APM automatic milling and pressing instrument.

Measurement Parameters

Measurements were conducted on an S2 RANGER with XFlash detector, in vacuum with a 30 mm sample holder mask. The measurement conditions given in Table 1 were used.

Table 1. Measurement conditions

Voltage [kV] Current [ìA] Beam Filter Live Time [s] Elements Analyzed
20 130 none 200 Mg, Al, Si, S, K, Ca, Ti, Mn, Fe

In order to reach the best measurement statistics, a counting time of 200 s and a constant current of 130 ìA was used. The total processing time for every sample along with sample handling, evacuating the sample chamber and actual counting time for the measurement was measured as six minutes.

Calibration

The superior energy resolution of the XFlash detector separated the spectral lines of Al, Si and Mg. Figure 1 shows the low-energy range of the spectrum from a typical cement sample.

Spectrum of a typical cement sample1 including Pd Lá1 tube.

Figure 1. Spectrum of a typical cement sample1 including Pd Lá1 tube.

A calibration based on seven Dillinger Huette certified reference samples for MgO, Al2O3, SiO2, SO3, K2O, CaO, TiO2, Mn3O4 and Fe2O3 was set up, covering the concentration ranges in Table 2.

Table 2. Calibrated concentration ranges

  Concentration Range [wt. %]
MgO 1.01 10.95
Al2O3 4.97 6.55
SiO2 19.34 24.00
SO3 2.56 4.60
K2O 0.11 1.54
CaO 51.59 64.96
TiO2 0.314 0.721
Mn3O4 0.053 0.138
Fe2O3 2.09 4.01

Accuracy of Measurement

Measurement of a single cement pellet (DH 203) was repeated 12 times against the calibration. The sample was unloaded and reloaded each time between the measurements. The composition results of one sample and the corresponding C3S and SM ratio calculations as displayed on the S2 RANGER touch screen are shown in Figure 2.

Composition results, C3S and SM as on the touch screen

Figure 2. Composition results, C3S and SM as on the touch screen

Table 3 demonstrates the impressive stability of the results obtained with the S2 RANGER.

Table 3. Short-term reproducibility of main components in a cement sample

Sample MgO [wt. %] Al2O3 [wt. %] SiO2 [wt. %] SO3 [wt. %] K2O [wt. %] CaO [wt. %] TiO2 [wt. %] Mn3O4 [wt. %] Fe2O3 [wt. %] C3S SM
Rep-1 1.2607 5.2096 21.0017 2.6333 0.6062 64.6438 0.3415 0.0510 3.2779 56.3560 2.4744
Rep-2 1.2379 5.1903 20.9600 2.6397 0.6023 64.6138 0.3451 0.0473 3.2732 56.6692 2.4765
Rep-3 1.2685 5.2075 20.9699 2.6350 0.6058 64.5789 0.3450 0.0496 3.2734 56.3491 2.4726
Rep-4 1.2810 5.2178 21.0041 2.6412 0.6095 64.7567 0.3469 0.0496 3.2829 56.7132 2.4709
Rep-5 1.2460 5.1971 20.9943 2.6333 0.6055 64.6684 0.3465 0.0508 3.2769 56.5984 2.4775
Rep-6 1.2661 5.2145 20.9772 2.6393 0.6027 64.7063 0.3473 0.0504 3.2763 56.7496 2.4706
Rep-7 1.2587 5.2145 20.9681 2.6387 0.6039 64.6454 0.3503 0.0509 3.2745 56.5747 2.4700
Rep-8 1.2734 5.2070 20.9746 2.6360 0.6033 64.5973 0.3443 0.0487 3.2658 56.4002 2.4755
Rep-9 1.2777 5.2209 20.9703 2.6315 0.6041 64.6814 0.3401 0.0507 3.2785 56.6769 2.4672
Rep-10 1.2979 5.2247 20.9819 2.6311 0.6126 64.7157 0.3504 0.0511 3.2782 56.7033 2.4676
Rep-11 1.2473 5.2024 20.9799 2.6415 0.6080 64.6748 0.3485 0.0530 3.2787 56.6726 2.4737
Rep-12 1.2876 5.2205 20.9770 2.6349 0.6127 64.6407 0.3512 0.0509 3.2775 56.4543 2.4685
Average 1.2669 5.2106 20.9799 2.6363 0.6064 64.6603 0.3464 0.0503 3.2762 56.5765 2.4721
Abs.Std.Dev. 0.0171 0.0099 0.0130 0.0035 0.0035 0.0490 0.0033 0.0014 0.0040 0.1413 0.0033
Rel.Std.Dev 1.35 0.19 0.06 0.13 0.57 0.08 0.96 2.70 0.12 0.25 0.13

As observed, the values for SiO2 and CaO show an absolute deviation of 0.01% and 0.05%, respectively. The reproducibility for C3S is an exceptional 0.14% at 56.6 absolute.

Conclusion

The unique characteristics of the XFlash detector make sure that monitoring of the composition of cement with superior repeatability of more than 0.2% relative for major elements is possible in 200 s counting time with the S2 RANGER EDXRF benchtop spectrometer. The detectors are used both to satisfy the enhanced need for process control and to serve as a backup for an existing wavelength dispersive X-ray fluorescence (WDXRF) system. They are convenient and user friendly and can be used with minimal operator training. The stability and ease-of-use of the S2 RANGER system makes it the ideal addition to any cement plant or terminal laboratory.

This information has been sourced, reviewed and adapted from materials provided by Bruker AXS Inc.

For more information on this source, please visit Bruker AXS Inc.

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