Multizonal thermochemical modelling of heavy metal transfer in incineration plants

Heavy metals enter an incineration plant as trace components in the fuel and are inhomogeneously distributed into the ash streams exiting the plant. Their concentration in the respective ash streams mainly depends on their chemical properties, especially on their volatility. Several authors already modelled the chemical state within an incinerator by one single thermochemical equilibrium calculation and achieved qualitative characterization of the heavy metals’ behavior.In the work at hand, a multizonal thermochemical process model of an incineration plant is developed. The chemical reactions within the incinerator are modelled as a sequence of thermochemical equilibria. Reaction kinetic as well as mass transport related inhibitions are accounted for by choosing a proper model structure.Test calculations for a waste and a biomass fired incinerator show that the model is capable of simulating the distribution of As, Cd, and Sn into the ash streams with better quantitative accuracy compared to the abovementioned single-equilibrium approach. The distribution of Cu and Pb is found to be closely coupled to the volatility of Cl on the grate.

► Development of a multizonal thermochemical model of an incineration plant for prediction of heavy metal transfer.
► Test calculation performed for a waste and a biomass incinerator.
► Transfer of As, Cd and Sn into different ash stream simulated in accordance with measurement values.
► Transfer of Cu and Pb found closely coupled to volatility of Cl on the grate.