Advanced Fluidized Bed Waste Heat Recovery Systems

Abstract

The U.S. Department of Energy, Office of Industrial Programs, has sponsored the development of a Fluidized Bed Waste Heat Recovery System (FBWHRS) and a higher temperature variant, the Ceramic Tubular Distributor Plate (CTDP) Fluidized Bed Heat Exchanger (FBHX) system. Both systems recover energy from high-temperature flue gases and produce steam. In a one-year evaluation test on an aluminum remelt furnace, the FBWHRS generated about 26 million lb of saturated steam at 150 psig. Before entering the FBWHRS, the flue gases were diluted to 1100°F to protect the fluidized bed distributor plate. In a second project, this FBWHRS concept was further developed by replacing the metallic distributor plate with a Ceramic Tubular Distributor Plate (CTDP), a closely spaced row of alumina rods. The ceramic unit permitted energy from flue gases to be recovered without diluting gases. Elimination of the air diluent system reduced the FBHX fluidized bed volume by 70% and increased heat recovery by 30%. Both systems offer several advantages. The fluidized bed particles enhance heat transfer and continually clean the finned tubes in the fluidized beds. Also, only the distributor plate is exposed to the hot fouling and corrosive flue gases since the fluidized bed quickly cools these gases to a uniform 500°F.