Browsing by Author "John, John Pius"

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    An Investigation for Energy Sustainability in Cement Industries in Tanzania: The Case of Mbeya Cement
    (Technische Universität Berlin Institut für Energietechnik, 2017) John, John Pius
    Cement production processes are facing crucial sustainability issues such as inefficient en‐ ergy and raw material use, product supply, production cost and environmental pollution. High energy and material use dominated by inefficient characteristics of cement production processes, in turn, lead into depletion of non‐renewable resources, increased production costs as well as environmental degradation due to emissions. The main objective of the study was to investigate performance of cement industry in Tanza‐ nia relative to sustainable energy utilization. Most of past researches have evaluated the per‐ formance of cement production processes using first law of thermodynamics alone (mass and energy balances) with the objective of improving energy efficiency. Although this ap‐ proach sheds light on the question of improvement of energy use in the processes, it has some limitations. The limitations are imposed by the internal irreversibility due to combustion and other physico‐chemical nature of reactions dominating the whole processes. The current emerging approach, which overcomes limitations imposed to the first law approach is ex‐ ergy‐based method, relatively new in evaluation of performance of cement production pro‐ cesses. However, owing to complexity of cement production processes, applying an exergy‐ based method manually is very difficult and complex. The current study proposes combined approach of exergy based method and modeling as well as simulation. The model was successfully developed, validated using real plant data and was used to predict the performance of the cement dry rotary kiln system of Mbeya Cement production processes. Data obtained from modeling and simulation were further used to evaluate the performance of processes, individual components, sub‐systems and overall kiln system at large using exergy based method. The approach not only simplifies the analyses but also gives detailed insight of real processes, source and type of real imperfections, its magnitudes and how imperfections can be minimized. Major findings indicated that the rotary kiln sub‐systems and the overall kiln system have poor exergetic performance, suggesting that potential for improvement exists. The overall exergy efficiency of the kiln system is around 33 %. Also results indicated that the rotary kilns have the lowest exergetic efficiency of about 14 % followed by the clinker cooler with exergetic efficiency of about 41.11 %. The highest source of irreversibility encompassed chemical reactions, especially calcination and clinker burning processes with exergy destruc‐ tion of 2,813.75 kJ⋅kgcl−1 and 1,148.17 kJ⋅kgcl−1. Results from parametric analysis suggested that if measures for improvements of processes, components and sub‐systems are taken, a significant amount of fuel and specific energy could be saved. Furthermore, it was confirmed that if the avoidable exergy destruction is minimized, processes, system components and sub‐systems performance could be improved from exergetic point of view.