Improving the cement manufacturing process
With over 300 million tonnes of cement produced in India each year and global demand set to grow, the importance of understanding how to increase production of this vital substance has never been clearer. Traditional means cement analysis, such as the Blaine measurement, have served their purpose well, but with production increasiang worldwide the reproducibility and slow nature of such techniques, along with the lack of information they generate, are becoming major drawbacks. In order to cope with the demands of modern construction cement, manufacturers are turning to methods that allow them to fully understand what they are producing in order to optimise process efficiency and the quality of the final product.
Laser diffraction method allows simple, rapid generation of information-rich data. Figure 1 shows particle size distribution data for 2 cement samples using a Malvern Mastersizer Laser Diffraction system. Sample 2 contains more fines than sample 1 but also more coarse material. Despite the clear difference between these materials it was impossible to differentiate them using the Blaine method, since the average specific surface area of both cements is the same. They are clearly, however, not the same, as demonstrated by the Malvern Mastersizer. How valuable is this new information? For answers, we need to look at how the data are used. Cement manufacturers measure Blaine to quantify product quality. The hydration speed of cement particles is a function of particle size and determines the strength of the set cement. Generally, finer particles hydrate more quickly, giving greater strength, and within certain limits finer cement is better cement.
Returning to our samples, these materials will behave differently when used. Very fine cement particles, in the 2-3 micron range can cause exothermic cracking. Conversely particles over 50 microns may not hydrate, compromising product strength. Sample 1 contains less of both types of particles and consequently is a superior cement, even though Blaine ranks it the same as sample 2. Only by obtaining a complete analysis of particle size distribution can we have confidence in how our cement will behave. The practicalities of switching to laser diffraction are equally compelling. Blaine measurement is a largely manual technique and real-time measurement is not really feasible. Laser diffraction, however, is fast and automated. In the lab this means greater productivity and better reproducibility. For processing it means on-line instrumentation and real-time measurement.
The Malvern Mastersizer 3000, which has a measurement range of 0.01 to 3,500 microns, is an essential component of a high-quality cement laboratory. Finished products, as well as replacement material such as fly ash and blast furnace slag and fuels, have varying size distributions and so behavioral understanding and prediction requires Mastersizer analysis.
With Understanding Comes Optimisation
Another advantage of the Laser Diffraction method is its applicability to online analysis. Malvern´s Insitec range of process control laser diffraction systems deliver online continuous particle size analysis needed for efficient, cost-effective monitoring and control of industrial processes. By monitoring processes in real-time we can correct process problems as soon as they occur in order to minimise waste and additional cost. This is particularly relevant during plant start-up and product specification changes, where using off-line analysis would be a time-consuming, iterative process involving sampling, analysis (repeat analysis), variable change, and more sampling. The sharp transition achieved by Insitec on-line analysis reduces the amount of out-of-specification material produced, decreasing energy consumption and increasing throughput.
Further optimisation can also be achieved through deeper analysis. Not only particle size, but also particle shape and chemical nature affect the way a cement behaves during use. A blend containing too little gypsum, for instance, will set too quickly after mixing of water, leaving little time for concrete placing. Malvern´s Morphologi G3 image analysis system, gives automated analysis of both the particle size and morphology of cement particles. The latter dictates how particles in a cement interact sterically, and therefore the setting speed and strength of a cement. Morphological analysis can be used to complement Laser Diffraction analysis, giving a useful means of researching new cements with lower water requirements and greater performance. A Raman spectroscopy add-on allows chemical identification, in addition to size and morphological analysis, allowing characterisation and optimisation of the amount of different particle types (such as gypsum, clinker, quartz, calcite etc.) in a cement. This is extremely important information for cement developers.
An Orthogonal Approach
In order to cope with the construction demands of the future, cement developers will need to be able to rapidly and inexpensively adapt their product to suit new applications. Malvern Instruments provides the technology and expertise that allows developers and manufacturers to develop new, high quality cements and optimise the processes used to manufacture them, maximizing throughput and minimising waste.
For further information:
Malvern Aimil Instruments Pvt Ltd
Naimex House, A-8 Mohan Co-operative
Industrial Estate, Mathura Road,
New Delhi - 110044
Tel : 011-30810244 | Fax : 011-26950011