Waste incineration in rotary kilns: a new simulation combustion tool to support design and technical change

This article presents a tool based on a simplified model developed for the combustion processes in a rotary kiln incinerator (slightly
inclined rotating primary combustion chamber). The model was developed with the aim of supporting the design phase of the
incinerator combustion chamber and, at the same time, of investigating possible technical changes in existing plants in order to
optimise the combustion process and the dimension of the rotary kiln (length, diameter) as a function of the characteristics of the
fed waste. The tool has been applied and the obtained results compared with a real incineration plant operating on healthcare waste
located in Rome (Italy). The mass and thermal balances were taken into account, together with kinetic parameters for the combustion
of the specific waste stream. The mass balance considered only the major mass components (carbon, hydrogen, oxygen, nitrogen and
sulphur). The measured external temperatures appear to be in good agreement with the simulated results. A sensitivity analysis of the
plant under different operating conditions was carried out using different input flow rates and excess air ratios, and an assessment was
made of the refractory and insulator properties of the kiln’s behaviour. Some of the simulated results were used during the periodical
maintenance to improve the refractory characteristics in order to reduce the fret and corrosion process.