Understanding of Hazardous Waste Incineration Through Computational Fluid-Dynamics Simulation

Abstract

Rotary kiln incinerators are widely used in the incineration of hazardous wastes of various types. However, the complex transport and chemical processes within the kiln system are still not well understood. The complete destruction of hazardous compounds depends very much on gas mixing behavior of different air and waste streams, the distribution of gas temperature and residence time within the kiln and the secondary combustion chamber (SCC). Due to large variations of waste types and difficulties in feed characterization (physical, chemical and thermal properties), the incineration process meets great challenges in a smooth operation, with substantial fluctuations of gas temperatures within the system. The temperature fluctuations lead to uncertainties in the process chemistry and difficulties in emission control. The newly enforced regulations from the European Union with stricter emission levels require a better understanding of the incineration process and improved process control for lower emissions and a better environmental impact. In order to get better understanding of the incineration process within the rotary kiln system, research was carried out to study the kiln behavior in relation to better process control. One of the focuses was on the process simulation by using Computational Fluid-dynamics (CFD) to characterize gas flow, temperature distribution and waste combustion in the rotary kiln incinerator. Temperature measurement of the operating rotary kiln incinerator at AVR-Chemie, located at the Rotterdam harbor in The Netherlands, was conducted to validate the CFD model and to provide the information to kiln operators at AVR. This paper will address the environmental issues related to the hazardous waste incineration, and summarize the results from the current research project for the simulation of gas flow and mixing, combustion heat transfer, and new ideas to use CFD simulation results for process control of an incineration plant.