WDXRF Pressed Powder Method for Industrial Analysis

The ZSX Primus III+ is suited for quantitative analysis of cement raw meal by the pressed powder method and for quality and process control of iron ore products. These two applications are discussed in detail in this article.

Cement Raw Meal Analysis on ZSX Primus III+

As we are all aware, cement is a very important material for construction. The mineral compositions of clinker are changed to render a number of physical properties to cement hence one must control the chemical compositions of cement raw meal.

Due to simple sample preparation, high precision and rapid analysis, the method of choice for chemical composition analysis in cement production processes has been XRF spectrometry.

The ZSX Primus III+ can be used for quantitative analysis of cement raw meal by the pressed powder method, as shown here.

Standard and Sample Preparation

For the calibration, a series of reference materials of cement raw meal certified by CSBTS were used.

Cement raw meal powder samples that were pulverized before, were pressed into aluminum rings at 120 kN to form pressed pellet specimens.

Measurement and Results

Measurements were done on the ZSX PrimusIII + with a 3kW Rh-target X-ray tube.

Measurement conditions are shown in Table 1. The RX25 multilayer analyzer, present in the standard configuration, has increased sensitivity for Mg and Na and can reduce higher-order lines such as Ca-Kα-3^rd, which would interfere with Mg-Kα.

The calibration results are listed in Table 2 and the calibration curves for the representative analytes are shown in Figure 1.

Table 1. Measurement condition

Figure 1. Representative calibration curves for cement raw meal

Table 2. Calibration result

Repeatability Test

One reference material specimen was used for the calibration and measured 10 times consecutively to demonstrate the performance of the ZSX PrimusIII+ with respect to short-term stability. The test results, shown in Table 3, prove that it is possible to analyze pressed pellet specimens of cement raw meal with high repeatability on the ZSX PrimusIII+.

Summary for Cement Raw Meal Analysis

It is possible to routinely analyze cement raw meal samples with high accuracy and precision on the ZSX PrimusIII+ by the pressed powder method, a simple sample preparation.

Quality and Process Control of Iron Ore Products by the Pressed Powder Method

Iron ore is a mineral resource available in abundance and iron is also one of the most important materials in modern industries. The increase in the amount of seaborne trade and prices has made analytical requirements to become more stringent. Total iron concentration in iron ore is the key point for trading hence analysis for determination of total iron requires high precision.

In mining sites, laboratory analysis includes grade check for beneficiation and blending, quality check of run-of-mine and products, and also research for area exploring. Similarly, iron ore analysis is required in pelletizing plants near mining sites and in sintering plants and stock yards at steel manufacturing sites. Wet chemical analysis is a traditional analytical technique for complete iron determination however it requires analytical skill and is time-consuming. Along with being accurate these analyses must be quick, simple and cost effective.

The pressed powder method is the ideal solution in terms of quickness and simplicity. As iron ore has a complex matrix owing to its various mineral assemblages, suitable corrections for that matrix effect are required in XRF analysis. The conventional correction technique for total iron by XRF is a method using Compton scattering as the internal standard also known as the Compton scattering ratio method, however this method does not satisfy the requirements of the iron ore industry. An enhanced Compton scattering method was developed by Rigaku by combining it with a theoretical alpha correction, which has improved analysis accuracy significantly.

The ZSX PrimusIII+ can be used for iron ore analysis, especially for determining total iron in iron ore and products by the pressed powder method, as shown below.

Standard and Sample Preparation

Six commercially available certified reference materials (CRMs) supplied by Japan Iron and Steel Federation (JISF) and Bureau of Analysed Samples Ltd (BAS) were used as the standard samples for calibration. These standards include hematite ore, sintered ore, pellet and pure iron oxide. The range of total iron concentration in these CRMs is wide, from 39.8 mass% to 69.8 mass%. The well-dried (two hours at 105°C) powder samples were ground in a tungsten carbide container and the powders obtained were pressed at 250 kN using sample cups without any binder.

Measurement and Calibration Method

The ZSX PrimusIII + with a 3kW Rh target X-ray tube was used to determine the element lines of Fe, Si, Al, P, Mg, S, Ca, K, Ti, Mn, V and Rh-Ka Compton. For the Fe-Ka measurement, the attenuator was used to minimize intensity without changing the tube loading.

The calibration equation for "total iron" is as follows,

α_j : theoretical alpha of element j
W_j : weight fraction of element j
I_Fe : intensity of Fe-Kα
I_Comp : intensity of Rh-Kα Compton.

The integrated FP software was used to calculate matrix correction coefficients (alphas) applied to the matrix correction in the calibrations. The theoretical alphas for total iron calibration were measured in consideration of the Compton scattering ratio by the Quant Scattering FP Method, an optional program for the ZSX PrimusIII+.

Results

In this study the accuracy of total iron calibration was really high. The calibration accuracy for all the components analyzed in this study is listed in Table 4. The accuracy is calculated from the formula

C_i: calculated value of standard sample
Cˆ_i: reference value of standard sample(check in original)
n : number of standard samples
m: degree of freedom (2: linear, 3: quadratic).

Measurements were performed with duplicated pressed pellet specimens. The test results are shown in Tables 3.

Table 3. Analysis result of sintered ore.

Summary of Iron Ore Analysis

X-Ray fluorescence spectrometry is a rapid, precise and accurate method to satisfy the requirements of the iron ore industry. It can also bring down cost and time in iron ore analysis. The results show that this method can be practiced with minimal dependence on mineral assemblages. They also indicate that the pressed pellet method with Rigaku's advanced correction technology is widely available to people in the iron ore industry such as suppliers, producers and steel manufacturers with high cost-efficiency and higher throughput when compared to traditional methods.

This information has been sourced, reviewed and adapted from materials provided by Rigaku Corporation.

For more information on this source, please visit Rigaku Corporation.