CarbonProcessdocumentation.docVIP

Carbon Process documentation 1 3 -13 This control system enables the specific energy input to the paste to be optimized continuously, thereby avoiding any likelihood of clogging. Its introduction on the plant has yielded an increase of 0.04 g/cm3 in baked anode densities for equivalent raw materials. III - ADJUSTMENT OF PITCH CONTENT It is well established that the majority of the characteristics of the baked anode are determined by percentage pitch content. The production of high-quality anodes therefore depends on an effective method of regulating this parameter. The procedure employed by A.P. in the case of vibro-compacted anodes [6] is set out below. 11I.2 – Theory Work on carbon-based anodes has been strongly influenced by soil mechanics. It is known from studies of the mechanics of multiple-phase media that plotting the results of compacting a soil of variable water content yields a dry density curve exhibiting a maximum, dry density being defined as that of the solids present in the medium being compacted. An increase in compactive effort (static or dynamic loading) is accompanied by an increase in maximum density paralleled by a reduction in water content. This is explained by reference to the concept of saturation water content, i.e. the threshold above which, for a given compactive effort, density reduces owing to the forcible separation by the liquid of the grains constituting the solid matrix. The set of curves obtained by varying the compactive effort is contained by an envelope, the saturation curve, which defines the maximum density attainable for a given water content. The compacting of carbon-based materials can be seen as presenting analogies with the case of soils to the extent that they are also made up of: - a gaseous medium : air - a liquid medium : the carbon binder (pitch, resins, coaltar) - a solid medium : the carbon matrix (petroleum coke, pitch coke, anthracite) 2 3 -14 One major difference, however, resides in the pore structure of th