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This paper describes an industrial process for stabilising sewage sludge (SS) with lime and evaluates the
viability of the stabilised product, denominated Neutral, as a raw material for the cement industry. Lime
not only stabilised the sludge, raised the temperature of the mix to 80–100 C, furthering water evaporation,
portlandite formation and the partial oxidation of the organic matter present in the sludge.
Process mass and energy balances were determined. Neutral, a white powder consisting of portlandite
(49.8%), calcite (16.6%), inorganic oxides (13.4%) and organic matter and moisture (20.2%), proved to be
technologically apt for inclusion as a component in cement raw mixes. In this study, it was used instead
of limestone in raw mixes clinkerised at 1400, 1450 and 1500 C. These raw meals exhibited greater reactivity
at high temperatures than the limestone product and their calcination at 1500 C yielded clinker
containing over 75% calcium silicates, the key phases in Portland clinker. Finally, the two types of raw
meal (Neutral and limestone) were observed to exhibit similar mineralogy and crystal size and
CitacióHusillos, N. [et al.]. Evaluation of a lime-mediated sewage sludge stabilisation process. Product characterisation and technological validation for its use in the cement industry. "Waste management", Març 2012, vol. 32, núm. 3, p. 550-560.