CMA

36 Dr Karstensen, Kåre Helge, Chief scientist, Mr Saha, Palash Kumar and Dr Engelsen, Christian J Foundation for Scientific and Industrial Research (SINTEF), Oslo, Norway Utilisation of municipal solid waste incineration ash as a raw ingredient in cement manufacturing ABSTRACT This article discusses about the use of MSWI ash (bottom ash and fly ash) as a raw ingredient for cement production. Municipal Solid Waste incinerators (MSWI) are facilities specifically constructed to reduce the mass and volume of the MSW and utilize the generated heat for power or heating. But these facilities generate bottom ash (typically 20-30 per cent of the original waste feed by weight) and hazardous Air Pollution Control (APC) residues (typically 2-6 per cent of the original waste feed by weight). When MSWI ash residues are co-processed in cement kiln, the ash is partly replacing one or more of the feedstock raw materials. However, high alkali, chlorine, trace elements, and organics in untreated ash limit addition to below 10%. Pre-treatment such as washing is proven to effectively reduce the limiting constituents and increase utilisation rate to around 30-50%, with some exceptions. CO2 emissions are mitigated by the introduction of MSWI ash, and life cycle assessments point to MSWI ash kiln feed as an environmentally favourable and cost-effective management strategy. Brief introduction to the use of Alternative Fuels and Raw materials (AFRs) in Cement manufacturing The cement industry has many opportunities to replace a portion of the virgin natural resources it uses with waste and by-products from other processes. These may be used as fuels, raw materials, or as constituents of cement, depending on their properties. This is called co-processing which is defined as use of a waste in an industrial process as an input material, additionally or in substitution of standard (primary, natural) input materials. Co-processing in cement kilns started in the mid- seventies when the petroleum crisis had increased drastically the cost of the fuel oil and when, in different countries, new regulation was issued on waste disposal. As a large amount of energy-rich waste (mainly solvents) was available, the co-processing of waste in cement kilns was the most logical answer to the situation on both environmental and economic fronts. Then, to increase energy saving, more and more sophisticated pre-treatment processes were developed, first to produce liquid substitution fuel and more recently, in the Nineties, to produce solid substitution fuel.