Aero-Shields: New Product Improves Boiler Performance and Maintenance

Abstract

Aero-Shields were developed by Covanta Energy in 2005 to address excessive fouling and accelerated tube metal wastage in certain heat transfer areas of a large Municipal Solid Waste (MSW) fired boiler. Computational Fluid Dynamic (CFD) modeling and a Cold Flow model were used to investigate flue gas flow distribution, velocities, temperatures, and other parameters in specific areas of the boiler. The intent of this effort was to identify the problematic areas and develop a solution to better distribute gas flow within these specific areas of the boiler. The result of this development effort was named “Aero-Shield”. The Aero-Shield provides a dual benefit of being a tube-shield and gas baffling device by incorporating extended tapered sides. The shape, size and installation location was developed through the use of CFD modeling. Initial testing of the shields was performed in December 2005 at the Lee County facility Boiler#2 at the top and bottom of the third pass. The Lee County boiler is a typical horizontal boiler design using Martin GMBH technology to process solid waste. This paper demonstrates how CFD modeling plays an extremely important role in designing and optimizing Aero-Shields for new applications. It also describes additional applications which have been tested in multiple facilities and boilers types since 2005. It covers design guidelines for the material, geometry, and installation procedure. The paper will also highlight a number of benefits which have been confirmed through extensive field testing which include: • Significant heat transfer increase in a targeted boiler area. This increases boiler efficiency and generates additional MWs at the same fuel rate. • In Energy-from-Waste (EfW) applications, capital and maintenance costs are often more important than saving fuel. Aero-Shield applications provide significant savings by requiring less heat surface for the same heat recovery in a targeted boiler component. • Reduced ash deposits which results in reduced maintenance. • Improved gas flow distribution allows Aero-Shields to reduce peak gas temperatures and velocities, resulting in lower wastage rates for critical boiler components. • Simple, quick, and economical installation: typically performed in a few hours. Covanta currently has a patent pending on this application and product. Additional testing is ongoing to address other areas within the boiler that may benefit from this technology recognizing that the “Aero-Shield” is a customized solution for each application.