Cement Manufacturers Association (CMA)

22 • Composition of the conventional raw materials at the considered plant; • Local availability and cost of de-carbonated raw materials; • Their composition and particularly their silica, alumina, magnesia, sulphur, VOC, or trace materials content • Possibilities to improve the qualities of raw materials by further processing Portland cement is made from mixtures of mainly natural mineral materials, principally chalk/ limestone and clay/shale. These raw materials can be partially replaced by wastes, tertiary materials and by-products from other industries in order to ‘fine tune’ the overall chemical composition. Replacement raw materials currently in use include cement kiln dust, construction waste, ceramic moulds, refractory bricks, road sweepings, power station fly ash, foundry sand, mill scale (steel production) and iron from used tyres. Less commonly, China clay wastes and colliery shale have been used. Work is also underway to introduce wastes rich in silica, iron, alumina, and lime minerals from, for example the water and automotive industries. The wastes used are mainly inorganic in nature, carefully sourced and subject to specifications. These replacement raw materials are processed through the high temperature kilns (solids at 1450 o C, flames at 2000 o C) in the same way as are natural materials. However mostly used Alternate Raw Materials in Cement Industry are Fly Ash, Granulated Blast Furnace Slag & Limestone. Alternative Fuels in Cement Manufacturing process Most alternative fuels come from a blend of hazardous, municipal, and industrial waste. Depending on the kind of component and its organic composition, alternative fuels utilised in the cement industry can be either liquid or solid with the right amount of chemical content. These fuels typically consist of petroleum-based wastes, miscellaneous wastes, hazardous and chemical wastes, agricultural and non-agricultural biomass residues. The calcinedr and clinker-forming kiln are where most of the fuel use and CO 2 generation occurs. The rate of CO 2 emissions can be significantly reduced by substituting low-carbon fuel with a high hydrogen-to-carbon (H/C) ratio for traditional fossil fuels. Using alternate fuels has been demonstrated to prolong refractory life while also generating less CO 2 . Since most alternative fuels (AFs) are produced from wastes that would otherwise be disposed of, AFs are typically less expensive than fossil fuels. Using these AF typically just requires a small amount of pre-processing expense but in todays’ scenario is a hurdle considering the logistic aspects. The protection of non-renewable energy sources and the elimination of waste disposal sites are two major benefits of substituting alternative fuels. Since AF often exhibit distinct combustion characteristics, the procedure must be modified to accommodate AF usage. Additionally, to balance the process’s degree of adoption, the rate at which AF (thermal substitution rate; TSR) replaces fossil fuels can be steadily increased. When waste is combusted in cement kilns, there is a greater net worldwide decrease in CO 2 emissions because of its amount of biogenetic carbon, which varies with each distinct AF. When waste is co-processed in cement kilns, the CO 2 balance is far more favourable than if it were just burned in special incinerators. As a result, although the use of alternative fuels has already grown considerably in wealthy nations in recent years, this trend may continue. Compared to developed nations, the