Raw materials XRF application for the cement industry using a universal borate fusion methodology

Introduction

A previous paper portrayed sample preparation by fusion methodology and the X-ray fluorescence (XRF) spectrometry analytical conditions for the calibration of cement materials[1]. Experiments were conducted according to the guidelines of two well-known cement chemical analysis International Standard Methods and results were presented. The results proved that this robust analytical method is able to qualify by the ASTM C 114[2] and ISO/DIS 29581-2[3] norms.

This analytical method was developed using a Claisse® M4TM fluxer, an automated fusion instrument for the sample preparation and the Zetium, Wavelength Dispersive X-Ray Fluorescence (WDXRF) spectrometer, for the determination of all the elements of interest relating to the cement industry. The method was used to prepare finished products, process materials, as well as a very large range of raw materials which will be described in this second paper. Cement, blended cement, cement with additions, aluminate cement, clinker, kiln feed, raw mix, limestone, gypsum, sand, clay, bauxite, silica fume, slag, fly ash and iron ore are among the raw materials covered by this analytical application. This sample preparation was also transferred and optimized for TheOx® fluxer, a fully electric fusion instrument, by executing a robust validation of the method’s performance.

Due to the fact that powders are affected by mineralogy and particle size effects[4, 5], it is almost impossible to use a single XRF calibration curve for the analysis of such a wide range of different materials using the pressed powder preparation method. When fused in a borate glass, all mineralogy and particle size effects are eliminated. A single XRF calibration curve covering the whole range of concentrations for all elements of interests for the cement industry raw materials analysis can be made.

This paper examines all the XRF analytical conditions for the calibration of the entire range of raw materials using the robust borate fusion sample preparation methodology as well as the numerous Reference Materials (RMs) used for this analytical application. The results of this general and unique XRF raw materials calibration will also be presented in terms of precision, accuracy, and limit of detection.

Experimental

Apparatus and instrumental conditions 

All information regarding instruments, sample preparation methodology development, final optimized conditions of using a Claisse® M4 fluxer and robustness analysis of the preparation method for sample preparation by fusion was presented in the previous paper[1].

In the following, a sequential WDXRF spectrometer with a rhodium end-window X-ray tube of 1000 watts was used for data generation. The spectrometer analytical conditions, peak-line, background measurements, background position, pulse-height, counting time and other parameters were defined and optimized by the wavelength step-scanning of standard disks representative of the application. The spectrometer analytical conditions for the measurement of all the elements used for the raw materials application were presented in a previous paper[6]. The analytical lines for certain elements were added to the analysis method because the reference values for these elements were available from the raw materials RMs. The measurements were executed under vacuum using a 28 mm collimator mask.

Calibration preparation

The calibration of the WDXRF raw materials application was executed using a wide variety of RMs from the following origins:

  • Bureau of Analysed Samples Ltd. (BAS): British Chemical Standard Certified Reference Materials 
  • Domtar® Inc. Research Center: Canadian Certified Reference Materials 
  • China National Analysis Center for Iron and Steel: NCS DC Reference Material 
  • European Committee for Iron and Steel Standardization 
  • European Coal and Steel Community (ECSC): Euro-Standard 
  • Geological Institute for Chemical Minerals: GBW Reference Material 
  • Institut de Recherches de la Sidérurgie (IRSID) : Échantillon-Type
  • Instituto de Pesquisas Tecnológicas (IPT) : Reference Material 
  • Japan Cement Association (JCA): Reference Materials for Xray Fluorescence Analysis
  • National Institute of Standards & Technology (NIST): Standard Reference Material® 
  • Slovak Institute of Metrology (SMU): Slovak Reference Material 
  • South Africa Bureau of Standards: SARM Certified Reference Material

Table 1 demonstrates the certified element concentration ranges in both the original sample base and the ignited base.

Table 1. RM element concentration as an oxide equivalent
CompoundConcentration Range of the Certified Reference Materials
Original Sample Base  (%)LOI Free Base (%)
SiO20,02 - 99,780,03 - 99,86
Al2O30,004 - 85,070,005 - 85,32
Fe2O30,005 - 85,30,005 - 91,03
CaO0,006 - 700,006 - 98,58
MgO0,001 - 21,250,001 - 39,66
SO30,02 - 46,30,02 - 58,54
Na2O0,001 - 4,810,001 - 4,84
K2O0,001 - 4,990,001 - 5,02
TiO20,004 - 3,760,004 - 3,77
P2O50,003 - 8,420,003 - 8,62
Mn2O30,0001 - 4,930,0002 - 5,05
SrO0,001 - 0,6380,001 - 0,649
Cr2O30,0002 - 0,4740,0004 - 0,486
ZnO0,0001 - 0,1070,0001 - 0,109
ZrO20,005 - 0,140,005 - 0,2
V2O50,0006 - 0,720,0007 - 0,75
BaO0,0012 - 0,660,0012 - 0,66

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