ON THE USE OF X-RAY DIFFRACTION IN THE SOLID-PROCESSING INDUSTRY
Maurizio Bellotto
CTG Italcementi Group, Rue
des Technodes, 78931 Guerville Cedex, France;
e-mail: ctg@dial.oleane.com
Keywords: in-situ measurements,
quantitative analysis, chemical reaction kinetics
Industrial applications of X-ray diffraction may be classified in two different broad areas. The first, and most obvious, is the application of diffraction analysis to subjects of industrial relevance. Nowadays most of the activity of application laboratories falls in this category, and the subject may even seem trivial and unworthy of a presentation. Nevertheless the pressure of industrial interests is such that laboratories hardly have time to carry out an experimental program and «post mortem» sample analysis. The quest for the optimization of time and resources is pushing towards in-situ analysis, where a sort of miniaturized device reproducing the essential features of the industrial process is placed in the beam and analyzed «live».
The second application domain of diffraction in industry concerns the control of processes via an X-ray diffraction probe. In this case the diffraction probe behaves as any other probe to monitor the process and the outcoming signal can be used for manual regulation or it can be fed back to an automatic control loop. The most important issue for this application lies in the evolution of the process control strategies which must be able to make the best use of the diffraction signal, and not so much in the treatment of the signal itself.
Several examples of what has been exposed sofar will be presented, issued from the solid-processing industry, and in particular catalyst manufacture and cement production.
Zeolites are used in the industry as shape-selective catalysts [1], and organic-functionalized molecular sieves are beginning to be synthesized [2], thus considerably enhancing their application potential. The nature and positions of cations in zeolites will control the electrostatic fields within the pores, thus influencing the adsorption and reactivity of the sorbed molecules. Cation positions are often temperature-dependent and therefore determination of both the framework structure and the cation positions under the actual working conditions is necessary. Norby et al. [3] presented an in-situ measurement of cation migration in zeolite Y during dehydration, and showed the coupled variations of water content, cation populations, T-T distances and T-O-T angles. This investigation was performed with synchrotron radiation at the NSLS Brookhaven National Laboratory, using an image plate detector.
Studies of in-situ Portland cement early hydration have been reported by Barnes et al. [4], both as such and with polymer additives. Such studies enable to assess the mechanisms responsible for setting and for cement-polymer interactions leading to different rheological behaviors. An energy-dispersive set-up was used at CCLRC Daresbury Laboratory.
Finally the development towards in-line
Rietveld analysis of clinker (the product of cement kilns) will
be presented. The full exploitation of such an analysis is
closely linked to the evolution of process control in the cement
industry.