Process sample analysis is increasingly important in the cement industry. The preparation of samples is key to ensure rigorous quality control of a range of materials, from raw materials to the finished products. An automatic combination of mill and press can speed up this process significantly. By Marc Bornefeld, Andre Mehling and Jan Herzog, Herzog Maschinenfabrik GmbH & Co KG, Germany.
Sample preparation in quality control laboratories of the cement industry usually receives little attention. Often, employees rely on well-rehearsed routines that are not optimally adjusted to the actual requirements of the material and equipment. Therefore, the results obtained from X-ray fluorescence spectroscopy (XRF) and X-ray diffraction (XRD) do not always exploit the full potential of both methods. This becomes obvious, for example, by an increased variability in XRF analysis of raw meal and clinker or an inaccurate determination of the mineral constituents of clinker and cement using XRD and Rietveld analysis.
In contrast to this finding, precise analysis of process samples is becoming more and more important in the cement industry. The increased use of secondary fuels often leads to difficult conditions in the kiln. These can easily be aggravated by fluctuating raw meal compositions and are sometimes exacerbated as a consequence of inaccurate analysis. In addition, cement blending becomes more demanding and requires precise quality control to allow an accurate dosing of individual components. To be able to manage these complex production conditions the sampling frequency has to be increased, resulting in a higher laboratory workload. Many cement laboratories can compensate the higher sample throughput by implementing automated sample preparation systems. A further advantage of automated systems is standardisation of sample preparation, largely eliminating the biasing influence of the personnel because of incorrect handling.
