Cement, Energy and Environment

can be made as to the operating parameters of the kiln, the efficiency of the raw feed milling and homogenization and the potential properties of the clinker in cement. With regard to raw feed preparation the presence of a siliceous component which is difficult to reduce in size is betrayed by the presence of coarse alite crystals, associated with pores and including belite crystals. Evidently the extent of this characteristic and whether it may be problematic in free lime reduction will be explored by examination of further field of view from this clinker nodule and from othPrs from the same clinker sample. The variability in shape of the smaller alite crystals suggests poor homogenization of the raw feed and possibly poor assimilation of components introduced from the fuel. Irregular distribution of magnesium may be due to poor blending of a dolomitic portion of the limestone quarry with the purer limestone. Again, of course, the rest of this clinker sample needs to be examined to determine whether this is an isolated occurrence or a potentially significant issue. Belite clusters indicate poor distribution of the siliceous component of the raw materials. In the case of the coarser silica grains the presence of sufficient free lime to convert belite to alite is indicated in this particular field of view. The cluster of fine belite crystals has not, however, been converted despite the presence of the liquid phase to transport dissolved lime. There is no free lime apparent in this picture and it will be necessary to examine the rest of the clinker to determine the amount of free lime which might be available. It would be a reasonable starting point to assume that free lime was not available because the lime saturation of the clinker, whether locally or generally, was low and the free lime was not present. The discovery of further free lime elsewhere in the clinker, particularly if in clusters, would cause this view to be revised and would point to further homogeneity issues with the kiln feed. Thus the process of examination will inevitably lead to revised opinions as to the state of the whole process until reasonably firm conclusions are reached. The fineness of the liquid phase points to a moderately fast cooling rate. This, combined with the generally fine alite crystals, apart from in the exceptional circumstances of the coarse silica grains, and the fine formation of the crystals indicates as well-formed flame with a short relatively hot profile. In the case of a feed with a relatively hot profile. In the case of a feed with relatively low lime saturation factor, perhaps less than 95 , the clinker can form with low free lime and moderate performance. If improvements in strength are required, however, simply increasing either the saturation or the silica ratio will inevitably lead to difficulty in reducing free lime and a more radical improvement in the raw feed preparation would be required. Evidently it would be unwise to form a diagnosis of a cement plant performance from the examination of a single picture of a clinker section. It is also clear that even this small fragment leads to an indication of the nature of the clinker and with the further examination of the rest of the sample the questions which need to be asked about feed preparation and mix design will become apparent. Courtesy: International Cement Review, July 2010, Pp-68-70. METHODICAL PROCEDURE FOR RIETVELD ANALYSIS In 2009, the specialist Building Chemistry Group of the German Chemical Society (Gesellschaft Deutscher Chemiker, GDCh} set up a "Rietveld Analysis" workgroup chaired by prof. Dr.J. Plank (TU Munich). The aim of this group is the development of a protocol for the methodical procedure in 38