Design and Evaluation of a High Temperature Burner Duct Recuperator System

Abstract

"The Babcock & Wilcox Company (B&W) has completed a program to design, construct, install, and field test a ceramic-based high-temperature burner-duct-recuperator (HTBDR) in an industrial setting. The unit was capable of operating in corrosive, high temperature (2250oF) flue gas streams. The HTBDR was successfully tested in a steel soaking pit at B&W's Tubular Products Division in Koppel, Pennsylvania.

The ceramic stage consisted of 50 bayonet style ceramic tube-in-tube assemblies supported by an insulated metallic tubesheet and sealed with a ceramic fiber product. The heat exchanger was designed to take maximum advantage of radiation heat transfer, minimize pressure drops on both the air and flue sides, and minimize thermal stresses and fouling. Modeling of the bayonet assemblies determined the outer-to-inner tube spacing to optimize the air-side pressure drop and heat transfer within the tubes.

During the 1400 hour operation prior to plant closing, the ceramic stage performed well with no material related problems or air-to-flue leakage. Maximum preheat air produced was 1425°F with a flue gas temperature of 2250oF. Measured fuel savings of 17-24% were obtained over the previous recuperated (metallic heat exchanger) system. This projects a savings of 41% for an unrecuperated furnace. A simple payback analysis indicated acceptable payback for installation in unrecuperated furnaces but unacceptable payback for recuperated furnaces at today's low gas prices."