Energy and exergy analysis/modelling at a parallel flow precalciner cement plant

Keywords: Cement production; Parallel flow precalciner; Energy analysis; Mathematical modelling The mathematical balance described can be used for calculation the heat and material transfer phenomena from when kiln meal is fed into a cyclone preheater to discharge of the clinker from the cooler. In this study, it is based on energy and material balance, and consist of individual models for the plant components, namely preheater, calciner, gas off-take (bypass), rotary kiln and grate cooler. The balances are linked mathematically to one another through the flows of kiln feed, gas and dust, and make it possible to calculate a steady-state continuation for the entire cement plant. In this study, mathematical model which solve mass equilibrium and energy in four stage precalciner of parallel flow cement product systems with simultaneous flow has been developed. A computer program that suitable for this mathematical model has also been prepared. Temperature, mass, energy and exergy values in every unity have been obtained in this program as a function of different fuels and the running conditions. The energy equilibrium system is fully or aparatly calculated for preheater cyclone, rotary kiln and cooler unity. The model is based on energy and material balances and consists of individual models for the plant components, namely preheater, calciner, gas off-take (bypass), rotary kiln and grate cooler. Mass balances are developed for four individual components, namely CaC03, CaO, MgCÛ3 (or MgO) and other oxides. Thus, recarbonization in cyclone stages, calcination in the last cyclone stage or calciner, calcination in the rotary kiln and associated heat effects have been calculated separately to construct a detailed mass and energy flow diagram. Detailed exergy balances have also been calculated based on a proper definition on environment and references substances. The effects of different operating parameters such as apparent calcination ratio, recarbonization ratio, rotary kiln inlet temperature, dust content of stack gas, excess air coefficient, heat losses from rotary kiln and clinker cooler and the ratio of tertiary air to seconder air on energy and exergy efficiencies have been investigated by varying the numerical values of these parameters within predetermined intervals and evaluating the numerical results obtained via the computer program. Energy, exergy and mass graphics were plotted using numerical results from computer software. The graphics were analyzed according to predetermined standard parameters. XXIV