The use of statistical entropy to evaluate the utilisation of incinerator ashes for the production of cement

Abstract

The paper discusses the utilisation of MSW incinerator residues for the production of cement with regard to materials management. Two objectives of waste management are the protection of men and the environment and resource conservation. Thus metals have to be recycled or transferred into appropriate final sinks. For both options a concentrating step is indispensable. MSW incinerators are such concentrating processes, as they accumulate metals in their residues. The mixing of high-concentrated residues with low-concentrated clinker in order to produce cement results in dilution of metals. This contradicts the above objectives. Concentrating and dilution processes can be described by materials balances. To evaluate different uses of MSW residues in the cement production the statistical entropy of the resulting distributions of selected metals (Cd, Pb, Cu) is assessed. The result is that in order to avoid an increase in the entropy, neither fly ashes nor bottom ashes of MSW incinerators should be utilised at large scale without pre-treatment. The method can be used to determine the quality of the residues so that they can be used in accordance with the objectives of waste management.