Summary

In the last decade waste incineration was dominated by environmental requirements and later by economic constraints. Hard legal requirements led to extreme technical solutions especially for the flue gas cleaning to reach very low emission values. Typically these values are lower than for fossil fired plants. 4-staged flue gas cleaning became standard (de-dust, de-SOx and de-HCl, de-NOx and removal of trace elements) and the whole plant became similar to a chemical production plant. The costs for incineration increased continuously and reached values of more than 230 Euro/ton of waste. New legal requirements for landfill in Germany changed this development within the last 5 years. The content of unburned material was to be reduced to 3 or 5 % (depending on the category of the landfill), but with a transition time to 2006. Costs of 20 Euro/ton of waste for landfill changed the whole market and waste incineration plants were forced to look actively for their fuel at a very low price level. Intermediate over-capacities were the consequence, which led to a straightforward optimisation of process steps. At the same time the lower calorific value of normal municipal waste increased with the consequence of increasing combustion temperatures and a dramatic increase of problems like corrosion, slagging and fouling in the furnace and in the flue gas pass. Technical answers are water cooled firing grates, modified furnace geometries, optimised secondary air injections and more suitable wall materials like ceramics or cladding of normal boiler steels. All these modifications made mathematical modelling and simulation more attractive even for practical applications. Some examples will demonstrate these new solutions.

For new fields of research the tendencies will be shown. One complex of these is the dust particle behaviour as a function of particle composition and gas species concentrations with respect to slagging, fouling and corrosion behaviour; the other one is the development of new ceramic materials and the application in furnaces.