Abstract
Pyroprocessing is an important stage in cement manufacturing. In this process, materials are subjected to high temperatures so as to cause a chemical or physical change. Its control improves efficiency in energy utilization and hence enhances production for good quality assurance. Kilns used in cement manufacturing are complex in nature. They have longer time constants, and raw materials used have variable properties. They are therefore difficult to control. Additionally, the inclusion of various alternative fuels 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 of clinker consumes power in the range of 2.5 kWh/ton of clinker produced. These and other pyroprocessing parameters make cement production costly. The pyroprocessing process in kilns and the grinding technologies therefore have to be optimized for best processing. This paper discusses the cement manufacturing and grinding processes. The traditional kiln technologies and the current and emerging technologies together with general fuel and energy requirements of cement manufacturing have been discussed. From the discussion, it has been established that the cement manufacturing and grinding technologies are capital‐intensive investments. The kiln processes are advanced and use both electricity and natural fuels which are expensive and limited factors of production. The raw materials used in cement manufacturing are also limited and sometimes rare. The calcination of the raw materials requires external energy input which has contributed to the high cost of cement especially to low‐income population in the developing countries. Self‐calcining materials, in which the pozzolanic materials burn on their own, are potential pozzolanic materials 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. There is a need, therefore, for research to look into ways of making cement using kiln processes that would use this property. This will be cost‐effective if successful. It can be done at micro‐ and small‐scale enterprise.
Highlights
IntroductionIts production is expensive due to high amount of energy used in its manufacture
Cement is the most commonly used binder in concrete production all over the world
Artificial pozzolanas have to be processed before use. e processing includes proper burning and grinding of the materials under carefully controlled conditions to form the amorphous form of silica which is important to their pozzolanic activity. e temperature and duration of burning are important in processing [4, 6, 8]
Summary
Its production is expensive due to high amount of energy used in its manufacture It is out of reach of a majority of the world population [1]. E high cost of cement especially in developing countries is mainly due to the high energy demand during the clinkerisation process. Ese materials have been shown to have cementitious properties and are known as pozzolana [3,4,5,6,7]. Natural pozzolanas are materials that will react with lime in the presence of water to form cementitious properties in their natural form at ambient temperature. E processing includes proper burning and grinding of the materials under carefully controlled conditions to form the amorphous form of silica which is important to their pozzolanic activity. Calcination and pyroprocessing technologies are very important for the development of low-cost cement
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