Heat transfer between a supernatant gas and a flowing shallow gas- fluidized bed of solids

• Main Author: Boyd, John H.
• Other Authors: Chemical Engineering
• Format: Others
• Language: en_US
• Published: Virginia Polytechnic Institute and State University 2017
• Subjects: LD5655.V855 1984.B694; Heat recovery
• Online Access: http://hdl.handle.net/10919/76414

A novel concept (called “heat tray”) is proposed for heat recovery from hot gases and for heat management in exothermic catalytic reactions, which involves a supernatant gas (S-gas) flowing over a shallow fluidized bed of solids. This thesis presents the results of bench-scale and pilot-scale experimental studies that quantify heat transfer between the S-gas and the shallow fluidized bed. A fractional-factorial design of experiments was performed on two heat-tray systems using three different results showed that fine fluid cracking catalyst (FCC) particles out-performed larger alumina spheres as a fluidized solid. Heat transfer coefficients between the supernatant gas and the shallow fluidized bed approached 440 W/m²-K using FCC. Various S-gas inlet nozzle configurations were studied, with a nozzle height equal to one-half of the static bed height (0.051 m) giving the best results. The study showed that short heat-tray lengths (<0.8 m) are desirable and that S-gas redistributors are needed to compartmentalize the unit. An economic analysis showed that the proposed heat tray would be economically feasible for adaption as a boiler feedwater preheater in a small steam-generation facility, using boiler combustion gases as the S-gas. The payback time for the system would be as short as 1.9 years when used continuously. The heat transfer results from a S-gas to a flowing shallow fluidized bed represent the only data reported thus far, and have led to a better understanding of the new shallow fluidized-bed system for heat-exchange applications. === Master of Science