Covanta is using a multifaceted approach to problem solving in Waste-to-Energy systems which combines several types of computer modeling with physical cold flow models, field testing, and engineering experience. This problem-solving approach is applied to boiler corrosion, gas and particulate flow patterns, reagent injection, and APC system issues. Our goals are to bring the most appropriate tools to each issue and incorporate results back into the engineering approach in order to continually improve our technical capabilities. Several types of computer modeling are used. A commercially available energy balance program is used for steam cycle evaluations and boiler energy balance and heat transfer calculations. Computational Fluid Dynamics (CFD) models are developed to investigate temperature and flow patterns where local conditions must be understood in detail. We have made extensive use of cold flow models to improve performance of APC systems, and to evaluate overfire air mixing in furnaces, and flow distribution through tube banks in boilers. Field testing is used to investigate temperature fluctuations and distributions, flow stratification, corrosion rates, and to validate modeling or analytical results. Each of these approaches has its own set of advantages, disadvantages, and limitations, and must always be combined with a healthy dose of operating and engineering experience. Analytical work is done by, or in close cooperation with, our operations and engineering staff with many years of experience operating, designing, and modifying boilers, APC systems, and related equipment. This integrated approach has yielded significant improvements in many cases and is being used in increasingly complex applications.
