A Review on Pyroprocessing Techniques for Selected Wastes Used for Blended Cement Production Applications
Date
2020Author
Nalobile, Protus
Muthengia, Wachira J.
Thiong’o, Joseph Karanja
Marangu, Joseph Mwiti
Metadata
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Pyroprocessing is an important stage in cement manufacturing. In this process, materials are subjected to high temperatures so asto cause a chemical or physical change. Its control improves efficiency in energy utilization and hence enhances production forgood quality assurance. Kilns used in cement manufacturing are complex in nature. ey have longer time constants, and rawmaterials used have variable properties. ey are therefore difficult to control. Additionally, the inclusion of various alternativefuels in burning makes the process more complex as the fuel characteristics remain inconsistent throughout the kiln operation.Fuel intensity standards for kilns using fuel oil are very high, ranging from 2.9 GJ to 7.5 GJ/ton of clinker produced. Grinding ofclinker consumes power in the range of 2.5 kWh/ton of clinker produced. ese and other pyroprocessing parameters makecement production costly. e pyroprocessing process in kilns and the grinding technologies therefore have to be optimized forbest processing. is paper discusses the cement manufacturing and grinding processes. e traditional kiln technologies and thecurrent and emerging technologies together with general fuel and energy requirements of cement manufacturing have beendiscussed. From the discussion, it has been established that the cement manufacturing and grinding technologies are capital-intensive investments. e kiln processes are advanced and use both electricity and natural fuels which are expensive and limitedfactors of production. e raw materials used in cement manufacturing are also limited and sometimes rare. e calcination of theraw materials requires external energy input which has contributed to the high cost of cement especially to low-income populationin the developing countries. Self-calcining materials, in which the pozzolanic materials burn on their own, are potential pozzolanicmaterials with great potential to lower the cost of cement production. Such materials, as shown from the previous research study,are rice husks, broken bricks, spent bleaching earth, and lime sludge. ere is a need, therefore, for research to look into ways ofmaking cement using kiln processes that would use this property. is will be cost-effective if successful. It can be done at micro-and small-scale enterprise.