INTRCCUI:TICN The control of chemical

and miner-

alagical compositions of both intermediate and finished products, as weil as of raw materials, is of paramount importance ta the cement industry. This is even truer today as fierce competition grows and cement prices drap, meaning that high quality analyses during the entire are required production
However, when the X-ray tube is sitting above the sampie, no liquid or loose powder sampies can be analysed.
AL TERNA TIVE FUELS Besides the standard raw materials, an increasing number of cement plants use alternative fuels ta reduce production costs. However, these materials contain additional trace elements that need ta be quantified, as they may have a negative ar positive impact an the production process ar environmenV. The need ta analyse mare elements I Figure 1. X-ray sp~ctrometer 54 EXPLORER and diffractometer 04 ENOEAVOR Integrated Into an automated laboratory in a wider range of sampie types and concentration ranges requires the use of powerful sequential XRF spectrometers, such as the 54 PIONEER (4 kW) ar 54 EXPLORER
process. Currently, determination of chemical composition and free lime are well-established methods, while full phase quantification is becoming a mare popular tool for process optimisation. Modern technology na langer requires high Iy trained specialists ta operate X-ray (XRF [a method ta eiemental composition]}
X-ray diffraction (XRD [a ta determine phase composition]} systems. allaws ever easier implementation of these reliadvanced methods in the entire production
(1 kW) from Bruker AX5. When dealing with a large variety of alternative fuels, calibrations typically fail as elements, concentration levels and matrix types vary. The reasons for this are the lack of reference sampies ar important elements such as heavy metais ar halogens. In those

YSIS plant

THRDUGHDUT control is chemical
ENTIRE PRDCESS modern cement
performed by XRF, providing vital informadifferent process steps. The production process begins with the analysis of raw materials. These can be quarry materials materials such as slags, industrial others. From those materials the oxide comare determined via XRF. In order to get reliand accurate results, the sampies need to be either as pressed pellets or fused beads. preparatlon procedures can be automathigh sampie throughputs are required. the analysis of raw materials sequential or wavelength-dispersive X-ray fluoresspectrometers are typically used. The WDX systems have a fixed configurafor a certain number of elements. As they meaall elements at the same time they achieve (WDX) sampie throughputs than sequential systems.
cases, pre-calibrated methods such as the 'OiIQuant' from Bruker AX5 easily extend the range of analytical routines. This is a universal calibration using unique variable alpha matrix correction saftware, which is an option with any of the company's spectrometers. The saftware corrects for matrix affects over a wide concentration range. With 'OiIQuant', a large variety of alternative fuels, such as used oils, paints, diesel, gasoline, and glues, as weil as waste plastic materials, can be fully quantified by just analysing the sampie. A specific calibration carried out by the user is not required.
DF PRIMARY IMPDRT ANC:E The control of the chemical composition of the raw mix is of primary importance to ensure the efficient operation of the kiln, and ultimately the quality of the finished cement. Wavelength-dispersive (WDX) and energy dispersive (EDX) X-ray fluorescence instruments have been used for many years to measure the

CEMENT

February
Figure 2. The 52 RANGER with autosamplet:
proportion of the oxides of aluminium (AI), silicon (Si), calcium (Ca) and iron (Fe) and hence to calculate the lime saturation factor (LSF), silica ratio (SR) and other modulii needed to control the mixing process. However, when the best analytical performance for oxides of sodium (Na) and magnesium (Mg) are needed, the use of WDX spectrometers is mandatory. Traditionally, composite sampies are taken periodically from the process line and then analysed as pressed pellets with a XRF spectrometer located in the central production laboratory. However, when the mineralogy of raw materials varies over a very wide range, the sampies need to be prepared as fused beads in order to achieve accurate quantifications. In larger cement plants, sampie taking, sampie transport to the central laboratory, sampie preparation and sampie analysis via XRF are fully automated to achieve accurate, reproducible results and maximum sampie throughputs. When much higher sampling and analysis frequencies are required, the raw mix control is carried out by dedicated fully automated EDX spectrometers located close to the raw mill (on-stream or on-line analysers). A composite sampie is taken up to 12 tph and is analysed as compacted powder or pressed pellet. When grain sizes vary, the raw meal is ground before analysis giving more accurate results.

Currently these dedicated EDX systems only quantify the four main oxides: A12O3, 5iOz, CaO, and Fe2O3 under He atmosphere. More powerful EDX systems such as the new 52 RANGER from Bruker AX5 can reliably quantify additionaloxides such as MgO, 503 and Mn2O3 (Table 1 shows the reproducibility). The analysis is performed under a vacuum atmosphere, reducing the costs of operation significantly. Due to its enhanced analytical performance, the 52 RANGER can also be used as a true backup system for various applications such as alternative fuels. In addition, Bruker AX5 also offers the 54 PIONEER (4 kW) and the 54 EXPLORER (1 kW) sequential WDX analysers. The first of these allows very high sampie throughputs and has the best detection limits (LOD) for light elements. The second is very similar in performance needing slightly longer measurement times, but no detector gas or water cooling, which results in minimum cost of ownership. All spectrometers were designed for easy use in the cement environment and seamless integration into any automated laboratory. C:LINKER ANAL Y515 Though clinker quality is governed more by its mineralogy and less by its eiemental composition, the determination of the chemical composition is weil established. Representative sampies are taken and analysed with a calibration. The results are used to estimate the clinker phase composition applying the Bogue calculations. Other fast methods for monitoring kiln operation were not available in the past. Complementary to chemical analysis, many plants determine the free lime content in clinker sampies using XRD. The sampies are ground. pressed and then analysed with a simple calibration. The free lime results are used together with the estimated phase composition based on Bogue to optimise kiln operation. In the past. full phase analysis via XRD was not possible due to several physical effects. These make a calibration for clinker and cement phases nearly impossible2. Now the D4 ENDEAVOR. a full diffractometer. and the TOPAS BBQ software from Bruker AXS allow the fully automatic quantification of

clinker phases. Together with the company.s fast VANTEC-1 detector. full analysis takes only a couple of minutes, fulfilling requirements for process control. When sampie preparation is optimised the same clinker pellet analysed with XRF can be used for phase determination. TOPAS BBQ, meanwhile, is the leading Rietveld software package used by all major cement companies (Table 2). In contrast to classical calibration-based quantifications, the Rietveld method is standardless, requiring a full diffractometer. As TOPAS BBQ was developed for the needs of the cement industry, the analysis can be performed by any operator. Expert knowledge is not necessary. For the user in the cement plant, this means that full phase quantification is obtained by simply loading the sampie and pushing the start button. This makes it easier than ever to implement XRD into quality control. Details of this powerful method are described in reference 3. The new VANTEC-1 detector (Figure 3) was designed with the high speed requirements of the cement industry in mind. The one-dimensional detector based on proprietary Microgap technology outperforms existing technologies with its excellent high-speed and very good signal-to-background ratio. The VANTEC-1 can be fitted into any diffraction system of Bruker AXS. without the need for additional infrastructure such as detector gas. The combination of fast detectors and Rietveld software makes full phase analysis available. It allows cement manufacturers a better understanding of the kiln process. One example is the increasing use of alternative fuels. This can change the clinker, and hence the cement properties, dramatically. Only when these undesirable properties are quickly monitored via XRD. can corrections be made in order to obtain constantly high clinker qualities1,4. C:EMENT ANAL YSIS In the final step of Portland cement production raw materials such as gypsum, gypsum/anhydrite mixtures or other materials are ground up with cement clinker in order to get precisely specified cement properties. Similar to clinker, the performance of cement is governed by the mineralogy and less by the eiemental composition. During the grinding procedure, the temperature of the mill feed can elevate leading to partial dehydration of the gypsum phase {CaSO4.2H2O} to hemihydrate {CaSO4.1/2H2O} {also named bassanite} or even anhydrite {CaSO4}.As all sulfate phases do considerably differ in both solubility and reactivity, the degree of dehydration has a direct effect on the setting behaviour. Knowledge about the absolute phase abundance of the sulfate phases in cements therefore allows monitoring and control of the cement mill operation. However, in the past an appropriate method was unavailable in order to determine the cement phases accurately. Quality control is weil established via XRF spectrometry, often by applying quality standards such as ASTM C114-03 or EN 197. Pressed pellets of

Figure 3. The VANTEC-l

detector:
representative sampies are analysed via calibration to determine the typical cement oxides plus the total sulfur content. The accurate and reliable monitoring of the sulfate phases, plus all other cement phases, can be achieved via X-Ray diffraction using TOPAS BBQ. Applying this new analysis tool will ultimately result in a much better control of the cement mill operation and hence in better cement qualities at reduced cost.
CDNCLUSIDN In partnership with the cement industry, Bruker AXS has developed analytical solutions designed to fulfil the needs of this modern industry. The combination of powerful analysers, precalibrated solutions and intuitive software makes it easier than ever to implement XRF and XRD systems for monitoring process steps. Though XRF has been in use many years, more valuable applications such as the analysis of alternative fuels are becoming established. The consequence is the preferred use of more flexible sequential WDX spectrometers. Complimentary to XRF, the XRD technique is becoming more popular. Besides the clinker and cement phase analysis, X-ray diffraction has the potential to analyse raw materials such as gypsum and other intermediate products. The full phase quantification will lead to a better understanding of the production process resulting in a better plant efficiency and product quality.
REFERENtE5 1. KLASKA, R., BAETZNER, S., MLLER, H., PAUL, M., and ROPPELT, Th., 'Effects of secondary fuels on clinker mineralo. gy', Cement International, 2003, No.4, pp 88 -98. SCHMIDT, R., and KERN, A., 'Quantitative XRD Phase Analysis', World Cement, February 2001, pp 35- 42. SCHMIDT, R., and FELDMANN, T. (2003): Breakthrough in phase analysis, World Cement, April 2003, pp 77 -80. PAUL, M., HORNUNG, D., ENDERS, M., and SCHMIDT, R., 'Process monitoring in a cement plant: the combination of optimized preparation procedures for clinker and cement and Rietveld analysis', Cement International, 2004, No.1, in press.

2. 3. 4.

WORlD CEMENT February 2004