A new method for the calorific characterization of wastes based on combustion calculations

• Theoretical basis of a complementary calorific characterization of wastes. • Theoretical basis for the interpretation of the Tanner diagram for wastes. • Proposal of a calorific classification of wastes which require incineration with sound basis. • Simplified approach for assessing co-incineration of waste with wide range of applicability. Waste incineration is and will remain an essential element of waste disposal in the future since it eliminates the toxicity of waste and reduces its volume. Therefore, a meaningful calorific characterization of wastes is important. However, since the heating value of a waste alone does not capture the energetic role of wastes in an incineration process sufficiently well, a complementary method is introduced in this contribution. It enables to quantify for low-calorific wastes the demand of supporting energy for incineration, and for high-calorific wastes the energy surplus which serves as supporting energy in co-incineration. The developed equations are based on idealized but nonadiabatic combustion calculations which consider the ‘standard’ characterization of a waste (calorific value and content of combustible matter, water and ash) and the main characteristics of an incineration process (including the relation between heat release and oxygen consumption, the dependencies of flue-gas properties on waste composition, oxygen excess and heat loss from the furnace). This approach provides a theoretical basis for the Tanner diagram, which is often used to characterize the limits of self-sustained combustion of municipal wastes; but its applicability is much broader in that it allows also to characterize hazardous wastes ranging from low-calorific wastewaters to high-calorific spent solvents both qualitatively and quantitatively. Moreover, the quantitative characterization of energy demand and surplus of a waste allows for a simplification of the waste energy balance which is useful for approximate calculations in practice.