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APPLICATIONS AND PERSPECTIVES OF A NEW INNOVATIVEXRF-XRD SPECTROMETER IN INDUSTRIAL PROCESS CONTROLD. Bonvin, R YellepeddiARL Applied Research Laboratories S.A., 1024 Emblem (Switzerland)

A. BumanARC Applied Research Laboratories, Dearborn, MI 48120 (USA)1. INTRODUCTIONWavelength Dispersive X-ray fluorescence (WDXRF) is a well established technique forprocess control in var ious industries. Its versatility in handling both conducting and non-conducting solids, its accuracy and excellent precision for the majority of the elements andthe wide dynamic range (from ppm to 100%) gave WDXRF the place it enjoys in the processand quality control. Elemental analysis of raw materials, intermediate products (sintered,calcinated or electrolysis related) and final products (cement, mining, pure metals and alloys)is routinely carried out using a typical configuration with about 10 to 20 XRFmonochromators for rapid analysis and an XI@ goniometer for flexible analysis of otherelements. In the metals industry, XRF is employed in conjunction with optical emissiontechniques or a more complete analysis.Due to the ever increasing demand for the detection and reliable analysis of trace elements nthe production of pure metals as well as for the tighter control of alloy or final productcompositions, there is a need for enhanced sensitivities in XRF and correspondingly lowerlimits of detection. In addition, there are needs to monitor specific phases or compoundseither in the raw materials or in the intermediate products for better utilization and processoptimization. Since XRF is essentially capable of measuring total elemental compositiononly, wet chemical methods are generally used for the analysis of a given compound, forexample free lime in cement clinkers, differentiation of iron oxides in terms of magnetite andhematite content, analysis of Fe2+ (FeO) in sinters or alumina related phases etc. Thesemethods are not only time consuming but are usually off-line with respect to the processintegration. X-ray diffraction can, in suitable cases,quantify the different forms of iron oxidesin ores or the Fe2+ n sinters or distinguish alpha-A1203 n alumina, or free CaO in clinker, etc.However, a traditional X-ray diffractometer can hardly be justified for such on-line processcontrol applications due to its complexity, its poor repeatability and the maintenance costsinvolved.The usefulness of having both XRF and XRD data on the same sample has been discussedearlier. Various combinations using WDX and EDX techniques have been proposed.Thepossibility of an energy dispersive diffraction/spectroscopy was first developed by Giessenand Gorden and Buras et.a1.23 he occurrence of diffraction peaks in an energy dispersiveXRF spectrum has been described4.Prediction and detection of diffraction peaks n an energydispersive XRF spectrum of a given sample and their exploitation in some applications hasbeen discussed4.Quantitative phase dentification and analysis using the data from XRF andXRD has been demonstrated in cases such as synthetic corrosion product, limestone andmullite5. It was hoped that such a combined analysis would become available in a singleprogram5.A combined XRF and XRD instrument for on-line processcontrol applications wasdescribed earlier 6. This system is based on a diffraction tube excitation of the sample and

Copyright(C)JCPDS-International Centre for Diffraction Data 2000, Advances in X-ray Analysis, Vol.42

Copyright(C)JCPDS-International Centre for Diffraction Data 2000, Advances in X-ray Analysis, Vol.42 126

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separate proportional counters to detect diffracted beams and fluorescence radiation. Anintegrated XRD-XRF system for the on-stream analysis of slurries was also described earlier.Here again, a standard XRD platform is used with fixed geometry goniometer and an EDXdetector for the XRF analysis. A combined XRD and XRF system for portable and remoteapplications (planetary explorations) has been developed . Built around low power excitationand CCD position sensitive detector, such an instrument was shown to be feasible andapplicable2. INSTRIJMENTATIONTaking into account these analytical needs, a new X-ray spectrometer has been developed(Figure 1) which integrates both X-ray fluorescence and X-ray diffraction in one singleinstrument (Figure 2).

fTiprr 2:Irl/e.gralior/ qf Xh!F ami XfW IN /he .sarneIl&pl:g.~. ( h.Y.S .%?oiotI of 1he itr!egl~rl/ed XIU~- nairrtnwnt: me xample, one it~slrunwr~l, oneAK/ 1 .yec/mniefer L7~lCllj5l.S

The salient features of this new X-Ray instrument are listed below:.

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.

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.

.

.

.

.

.

Modular construction enabling the selection of analytical devices such as XRFgoniometer, XRF monochromators and integrated XRD system. Most appropriateconligurations can be defined to achieve speed of analysis, sample throughput or limits ofdetection as required.High sensitivity thanks to optimized X-ray optical design for monochromators andgoniometers.Latest generation end-window tube with Rh anode providing broad spectrum excitation.Extra-thin window (75 micrometers) increases sensitivity for light elements. 70 kV excitationprovides higher sensitivity for heavy elements.Geometry with X-ray tube above sample preventing damage to instrument in case of defectivesamples (pressed pellets) and ensuring high uptime in routine use.Fast, simple and highly reliable sample introduction system.Fast gearless XRF goniometer with such positioning accuracy that precision is equivalent totixed channels. Allows also semi-quantitative and standardless analysis through state-of-the-art QuantAS and UniQuant software options.Integrated XRD system providing XRD measurements with the same tube on the samesample.High stability of analysis thanks to global and local thermal control systems.WinXRF software compatible with Windows TM NT environment, integrating analyticalexpertise in its Analytical Assistant to help the operator through the use of the spectrometer.Modem support available to prevent or diagnose instrument or analytical problems.



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3. APPLICATIONS3.1. IRON AND STEEL INDUSTRYThe analytical needs of the modern iron and steel industry (see Figure 3 below) increasinglydemand more comprehensive and process-integrated instrumentation. Two trends seem toemerge in the way the analytical instruments are positioned in this industry: there is a clearmove towards decentralization of the measurements and there is a need for higher levels ofinformation content from each analytical instrument. Indeed, most iron and steelmanufacturers would like to see that the analytical capability moves closer to the processwhere the answer is truly needed

TOTAL IRON X-RAY ANALYZERA mplele an- I&immiy In a d&c hstmment

Iron ores

Low dKh$ dloy 1 :;,;.* $

Coating thiekness(nqh2)y

Hematitqhlagnetite)

monoelemcnt on shd plate Eli,

Fiqure 3:Typicul applications in the iron and steel industry for an integrated XRF-XRll spectrometer

3.1.1 Analysis of hematite and magnetite in iron oresFigure 3 shows an XRD scan on three iron ore samples. Two distinct peaks can be seen: thepeak around 2.96 Ang. is due to magnetite (Fe303) while the peak around 2.7 Ang. is due tohematite (Fe,O,). The peak intensities are quite high allowing their use for quantitativeanalysis based on peak intensities as there is no observable peak shift as seen in Figure 4.However, the XRD program allows a search for the exact position of the peak beforemeasuring the intensity. This is particularly useful if iron ores of different origin are mixedand slightly varying polymorphic structures exist. It is also possible to do a peak integrationwith or without suitable background correction.

10MJIF2 18.$ IIg *o1 IIII8I0I

I Bare currr witho, corre ctionr I

Fe304-II-,A+ ,-&&J&.& 4

3.1 3.0 2.9 2.8 2, 2.6dspocing (Alptrom, 1Fiqure 4:XRD scans on 3 iron ore samples showing

507p JO$6r-Ij 3

20

JO 60 80 100

bure 5:CRD calibration curve of Fe203 in a series_the hemafite and magnetite phases ot u-on ore samples



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Figure 5 presents he calibration curve for the hematite phase n a series of iron ore samples.The accuracy of the XRD measurement eflects that of the wet chemical method. One of themost important aspects of the integrated XEW system is its reproducibility and long termstability. The XRD measurementsbenefit from the same optical encoder technology used onthe XRF goniometer as well as from the vacuum environment and the high precision of thesample positioning system. Apart from the quantification of different mineral species n theiron ore, the XRF part of the instrument is also used for analysis of trace elements or oxidespresent n the sample.3.1.2 Analysis of Fe0 in sinters:Analysis of Fe0 in sinters can be made much faster and on-line with the help of the integratedXRD system, ypically in less than 100s with very good precision. A series of sinter sampleswere measured to establish the calibration curve using concentrations determined by wetchemistry.A typical range of Fe0 may be between 4 to 9%. This means that very high sensitivities arenecessary o achieve good precision. Thanks to the closely coupled optics, the integratedXRD system offers the necessary peak to background intensities to achieve satisfactoryperformance.Figure 6 shows a calibration curve obtained for a series of sinter samples. Excellentcorrelation is obtained between the XRD intensities and the chemical concentrations of FeO.Table 1 provides the corresponding regression results. A typical standard error of estimate(accuracy) of around 0.2% is achieved.

4.44.2

h 3.8.0

% 3.6I 3.4

P 3.2

2 if2.6

Base Curve wihtoutCar,ectionr

3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0Fe0 Concentration P/o>

Figure 6: XRD calibration for Fe0 in sinters

SinterNr.

12345678910111213

Standar

Inten-sityKcps3.55833.53842.96263.57433.22993.74893.59813.42943.91153.8248

3.74223.72743.0838

PCNominal

5.05.34.45.44.85.65.55.26.46.25.65.84.6

5.415.384.275.444.795.785.495.176.095.935.775.744.51

Absolute0.410.08-0.130.04-0.010.18-0.01-0.03-0.3 1-0.270.17-0.06-0.09

Error of Estimate: 0.20Table I: XRLI calibration results of Fe0 in sinters

T-Concentration of-Calcul. l- ifference



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Table 2 shows short term repeatability results on a sinter sample. Since the instrument iscapable of analysing all the elements or oxides by XRF together with the Fe0 concentrationby XRD in the same sample, one can effectively combine the results from the two methodsand exploit the synergy between total elemental concentration and the specific phase contentof the same element. The standard deviation shown in Table 2 for most of the constituentsdoes confirm the suitability of the instrument in a typical processcontrol environment.Run Fe0 FeTotal56.2556.2456.2556.2556.2656.2756.27

56.2756.2756.2756.28

SiOz A1203 CaO Ml@ TiOz Mn S P VI> 8.322> 8.313> 8.304> 8.325> 8.306> 8.327> 8.308> 8.309> 8.29lO> 8.31ll> 8.32

5.81 2.145.82 2.135.81 2.135.82 2.145.83 2.145.82 2.135.82 2.135.83 2.135.82 2.145.83 2.145.82 2.14

A% 8.31 56.26 5.82 2.14Sd 0.01 0.01 0.01 0.00Sd% 0.13 0.02 0.10 0.23

10.2110.2110.2010.2110.2010.2110.2010.2010.2110.2010.2010.200.000.04

1.781.791.791.791.791.791.791.791.781.791.791.790.000.17

0.220.220.220.220.220.220.220.220.220.220.220.220.000.39

0.32 0.004 0.098 0.0290.32 0.004 0.098 0.0280.32 0.004 0.098 0.0290.32 0.004 0.097 0.0290.32 0.004 0,099 0.0300.32 0.004 0.097 0.0290.32 0.004 0.098 0.0300.32 0.004 0.099 0.0280.32 0.004 0,099 0.0300.32 0.004 0.097 0.0290.32 0.004 0.099 0.0300.32 0.004 0.098 2.430.00 0.000 0.001 0.000.39 1.748 2.130 0.11

Table 2.* Short term repeatability results on sinter sample using the integrated XRD-XRF spectrometer

3.1.3 Direct Reduced Iron:Direct Reduction (DR) has been defined as the processof reduction of iron oxides to metalliciron using a lower temperature than required for a conversion to liquid state. The iron oxidescan be in the form of sized ores, concentrates,pellets or mill scale etc. The reduction processitself can be gas based or coal based. Direct Reduced Iron (DRI) is a metallic product whichis used as a feedstock for electric arc furnace steelmaking, in blast fwnaces, and in other ironand steelmaking applications. Its main advantagesare a low level of impurities and chemicaland physical consistency.Hot Briquetted Iron (EIBI) is a densified form of DRI.The DRI process is being implemented in various parts of the world thanks to its manyadvantages.Since the process nvolves reducing the iron ore directly using a gas mixture ofcarbon monoxide and hydrogen, for example, the analysis of iron ore as it goes through aseries of reactors would allow a continuous control of the reduction process. t is obvious thatthe concentration of iron oxide (hematite for example) decreases o near zero levels when themost of the iron is in the metallic form. The integrated XRF-XRD spectrometer,named in thiscase Total Iron X-ray Analyzer may be used to monitor this processby measuring the oxidecontent by XRD, total Fe content by XRF and the difference accounting for the metallic Fe.



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3.2. ALUMINIUMINDUSTRYProduction of aluminium involves electrolysis of aluminium oxide. Starting from the rawmaterials (bauxite, aluminium bearing minerals) through alumina to aluminium metal and itsalloys, XRF can be positioned in different areasof processand quality control in this industry(see Figure 7 below). X-ray diffraction (XRD), on the other hand, is commonly used, forexample, to perform the electrolytic bath analysis in addition to any other off-lineapplications.

luEAL ALUMINIUM X-RAY ANALYZERAcompleteanntysislaboratoryiuasingle~

Alumlns(a-Al203)

Electrolyte Bath;cess AlF3,C&?, BR:

Alumtntum metalAlloys

,Fisure 7:Typical applications in the aluminium industry for an integrated XRF-Xm spectrometerFigures 8 and 9 show as examples he calibration curves or the excessAlF3 and total calciumrespectively, using the integrated XRD system of the Total Aluminium X-Ray Analyzer.Figure 10 shows the calibration curve obtained for a-Al203 in a series of alumina samplesusing the sameXRD system.

:

EfB

MVR Graphical Results:XRD for excess AIF

sase curve WIthoUt CorreCtloB

0 2 4 s 8Cancmtratlan [%,

/23.623.2t 22822.4

i-:r:-:$ 22D 21.6

21.24.8 4.9 6 5.1 6.2

I Concentration ml 1Figure 8: XRD calibration curve or the excessofAlF3 in Figure 9: XRF calibration curve for the total calciuma seriesof bath samples in the bath samples IIMVR Graph14 Results:

XRD of Alpha4203 in AluminaBase Curve without Corrections

Figure IO: XRD calibration curve for the a-AlJO in aseriesof alumina samples



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3.3 CEMENT INDUSTRYThe analytical requirements of the cement industry have evolved in the past few years toencompass a wide range of materials and qualities. While it is difficult to substitute thedifferent physical and chemical methods used in a cement laboratory by a single technique,most cement manufacturers are looking for rationalization and integration of analyticalmethods. This is in accordance with the drive to (a) optimize the use of raw materials andadditives, (b) reduce the production costs, (c) improve and stabilize the quality and (d) keepthe maintenance and running costs under control. In addition, environmental issues arebecoming more and more important in the cement industry both in terms of using the kiln toincinerate and eliminate waste products and using by-products from other industries asfillers, i.e. coal ash, metallurgical slags, silica dust etc.

TOTAL CEMENT ANALYZERA~pMecement t+slshbora~inazin~madtb~e

(Slags, Fly Ash,Limestone, etc.)

(Heavy mctsl, In du.st) CementFiaure 11:Typical applications in the cement ndustryforan integrated XRF-Xm spectrometer

While the role of XRF in the analysis of major andminor oxides in the raw materials, clinker, cementand additives is universally accepted, the use ofXRD for the analysis of free lime in clinkers andother crystalline phases such as limestone in theprocess of precalcination or as an additive incement has been limited until recently. Only anintegrated XRD system can be justified in such on-line process control applications due to itssimplicity of use, high repeatability and the lowmaintenance costs nvolved. A summary of variousapplications in the cement industry is given inFigure 11 and in Table 3.

TOTAL CEMENT ANALYZERXRFFixed channels

l Simultaneous andrapid analysis(

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3.4. STANDARD-LESS ANAL YSISFrom the analyst point of view, one of the most useful recent developments n WDXRF hasbeen the availability of semi-quantitative or so called standard-less analysis programs.These programs enable to handle all kinds of samples irrespective of the availability ofmatching standardsand calibrations. A universal goniometer covering most of the elementsfrom Boron to Uranium is used for this purpose.The semi-quantitative analysis can be based on a global scan followed by spectral processing(QuantAS) or peak and background measurements at fixed spectral positions followed byintensity processing UniQuant@).The accuracy and reliability of these programs s improvingconstantly as more efticient matrix correction algorithms, overlap and background correctionmodels are developed. Applications such as alloy sorting or characterization of specialtyalloys, on-the-spot analysis of raw materials, analysis of irregular solids etc. can be handledusing these programs. Indeed, both QuantAS and UniQuant@ programs bring a very highvalue to the XRF goniometer by fully exploiting its flexibility, precise angular positioning andoptimized collimator-crystal-detector combinations.Although the X-ray instruments in any industrial process control are predominantly appliedfor the analysis of routine samples, there is still a need for flexibility to handle ad hoc oroccasional samples.For example, the quality of the incoming raw materials or fluxes or coalor environmental dust or any other specialty products may need to be characterized rom timeto time. Difficulty arises when these non-routine samples do not fit into any of the calibratedprograms. Semi-quantitative programs can handle such situations and report theconcentrations directly. The following three examples (tables 4, 5 and 6) illustrate the typicalperformance of such programs n comparison with certified concentrations

----I- Zn 1 25.3% 25.2%_--.Al I 5.10% 5.18%~~~

Table 4: Sample BERM CDA 863 - Copper Alloy

Table 5: Sample NlsT 195 - Ferro-Silicon ---------->

>

Cl 1 740ppmAl 650o~m / 650o~m /I Ca I 530ppm I 540ppm I

S I 1Oppm I 31 wm 1



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ConcentrationsElement Given UQ j QuantASI Fe 1 31.2% / 30.8% I 30.5% I

2.83% 2.82%2.38% 2.20%

1 Mn 1 0.910% 1 0.928% 1 0.941%Ta-.SiAlLaTivCl

0.752% 0.807% 0.790%0.382% 0.198% 0.414%-0.134% 0.164% 0.240%

265ppm 102ppm 280ppm232ppm 292 ppm 270ppm_.---_--- 202 ppm 180ppri-

____--170 ppm--___

Table 6: Sample BS 162 - Maraging Steel

4. LINKING THE INSTRUMENT TO THE PROCESS THROUGHAUTOMATIONThere exists in process control industries requirements for simple automation requirementswhere samples are available only in one single form, typically pressedpellets in steel rings orcylindrical metallic samplesof identical size. In these casesa large sample changerpositioneddirectly in front of the instrument can be linked to a transport belt which brings the preparedsamples rom the automatic preparation machines to the instrument. The griper of the samplechanger can move on both X and Y axis in order to position itself precisely at desiredpositions above he surface of the magazine. The griper picks up the sample from the belt andbrings it to the loading port of the instrument to be introduced into the vacuum chamber ofthe spectrometer.The sample identification and the analytical program selection can be done through softwareconnection from a remote PC using the standardanalytical software. Alternatively an externalcomputer system can act as master of the whole automation system. Automation of analysiscan be performed not only for production samples but also for control standards,setting-upsamples and type standards. After the analysis the sample can be returned to the sametransport belt or to a second ransport belt (Figure 12) or filed in three classification baskets



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Belt from the right Belt from the rear andof instrument left of instrument

transport belts

Belt from the left ofinstrumentL&we 12: Illustration qf the various possibilities to link rrausport hrlt.r to the X-Y sumpIt changer.

When full automatic operation is required, the instrument can be connected to automaticpreparation machines through a robotic sample manipulation system (Figure 13). This flexibletool for automation works as the brain and arm of the whole analysis process. Thanks to theuse of an industrial robot for all manipulation operations, it can handle multiple sampleforms. It manages the sample introduction, registration, preparation and analysis, as well asthe priorities between analysis of production samples, measurement of control standards,running of setting-up samples, type standards or manual samples. Sample sorting, marking orfiling are performed quickly and efficiently. The automatic sample manipulation systemworks in order to minimize sample turnaround time. Instrument control through on-lineStatistical Process Control (SPC) and standardization are tasks which are integrated in thenormal routine work of the automation system. They are only performed when required and attimes when analy:

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5. CONCLUSIONSIn conclusion, the ARL 9800 X-ray spectrometeroffers the state-of-the-art nstrumentation tomeet the present and the future analytical requirements of process control industries, inparticular in the iron and steel, aluminium and cement industries. The modularity, reliability,reproducibility and the ease of use through total integration are the key features of this newinstrument. The integration of the well established XRF technique in conjunction with XRDis realized in a single instrument with a view to facilitate the most comprehensiveanalysis ofraw materials and products. The instrument can be configured and optimized with variousanalytical modules to handle fast routine elemental analysis as well as analysis of non-routinesamples, The compact size of this new instrument is compatible with its integration intosimple or state-of-the-art automated systems linking it to automatic sample preparationequipment.

6. REFERENCES1.2.3.4.5.6.7.8.

R. Jenkins, Interdependence of X-Ray D iffraction and X-Ray Fluorescence data, Advances in X-Ray Analysis, Vol. 2 I, pp 7-21, 1978B. C. Giessen and G.E. Gorden, Sci., Vol. 159, p. 9 73, 19708. Buras et al, Report 894/l l/PS, Inst. of Nut. Res., Mar. 1968R. G. Tissot and R. P. Goehner, Diffraction peaks in X-ray spectroscopy: friend or FOE?,Advances in X-Ray Analysis, Vol. 36, pp 89-96, 1993J. P. Engelbrecht,M, F. Garbauskas and R. P. Goehner, Complete quantitative analysis using both X-RayFluorescence and X-Ray Diffraction, Advances in X-Ray Analysis, Vol. 25, pp 285-288, 1982M. Hietala and D. J. Kalnicky, Applications of on-line XRF and XRD analysis techniques toindustrial process control, Advances in X-Ray Analysis, Vol. 32, pp 49-57, 1989J. P. R. de Villiers and SW. w. de Bruyn, The on-stream X-ray analysis of slurries for processcontrol, Advances in X-Ray Analysis, Vol. 35A, pp 661-672, 1992J.A. Kerner and E. D. France, Combined XRD and XRF analysis for potfable and remoteapplications, Advances in X-Ray Analysis, Vol. 38, pp 319-324, 1995



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