Fluid Bed Combustion Applied to Industrial Waste

Abstract

Because of its unique ability to handle a wide variety of liquids and solids in an energy efficient and environmentally acceptable manner, fluid bed combustion is being increasingly applied to the utilization of waste materials and low grade fuels as alternate energy sources. A description of fluid bed combustion is provided and, from this, the advantages of fluid bed systems are derived. Various fluid bed reactor systems and their applicability as a function of feed characteristics are discussed, including cold windboxes for autogenous feeds, hot windboxes for subautogenous feeds and in-bed steam coils for superautogenous feeds. The characteristics of waste feeds which make them suitable or unstable for combustion in a fluid bed system are discussed and examples of feeds currently burned in fluid bed systems are provided. The primary considerations in the heat balance are discussed and a simplified system for initial sizing for the reactor system is developed. This system is based on the input feed SFC (Specific Feed Characteristic), which is the gross heating value (HHV) per unit mass of moisture in the feed. This characteristic may be used to establish the degree of autogenicity of the feed and, in conjunction with tables and figures provided may be used for preliminary design and sizing of a fluid bed combustion system. Examples of specific installations are discussed, including some presenting special design problems.