Doctoral Defense - Michael Hayes

About the Event

The Department of Mechanical Engineering
Michigan State University
Ph.D. Dissertation Defense

Monday, April 29th, 2024 at 2:00 PM
Conference Room 3405 Engineering Building and Zoom
Contact Department or Advisor for Zoom Information
 
ABSTRACT

DESIGN AND CONTROL OF A BENCH-SCALE MOVING-BED THERMOCHEMICAL OXIDATION REACTOR FOR MAGNESIUM-MANGANESE OXIDE PARTICLES

By: Michael Hayes

Advisor: Dr. André Benard

The intermittency of renewable energy sources necessitates storage technologies that can help to provide consistent output on-demand. A promising area of research is thermochemical energy storage (TCES), which utilizes high-temperature chemical reactions to absorb and release heat. While promising, TCES technologies often rely on storing chemically charged materials at high temperatures, complicating handling and posing serious challenges to long-duration storage. A pioneering approach known as SoFuel (solid state solar thermochemical fuel) proposed using counterflowing solid and gas streams in a particle-based moving-bed reactor to achieve heat recuperation and allow flows to enter and exit the reactor at ambient temperatures. Previous work has successfully demonstrated operation of a reduction (charging) reactor based on this concept; this dissertation describes the development of a companion oxidation (discharging) reactor.

The countercurrent, tubular, moving bed oxidation setup permits solids to enter and exit at ambient temperatures, but the system also features a separate extraction port in the middle of the reactor for producing high-temperature process gas. A bench-scale experimental apparatus was fabricated for use with 5 mm particles comprised of a 1:1 molar ratio of MgO to MnO, a redox material that exhibits high oxidation temperatures (around 1000° C) and excellent cyclic stability. The experimental reactor system successfully demonstrated self-sustaining thermochemical oxidation at temperatures exceeding 1000° C. Many trials achieved largely steady operation, showcasing excellent operational stability during hours-long experiments. With the aid of user-manipulated inputs, the reactor produced extraction temperatures in excess of 950° C and demonstrated efficiencies as high as 41.3%. An extensive experimental campaign revealed thermal runaway in the upper reaches of the particle bed as a risk to safe, stable reactor operation.

To better understand reactor dynamics and evaluate potential control schemes, a three phase, one-dimensional finite-volume computational model was developed. The model successfully emulated behavior from the on-reactor experiments and further illustrated the impacts of the three system inputs - solid flow rate, gas extraction flow rate, and gas recuperation flow rate - on overall behavior. A five-zone adaptive model predictive controller (MPC) was developed using a linearized control-volume model as its basis. The controller sought to regulate the size, temperature, and position of the chemically reacting region of the particle bed through several novel approaches. These approaches were tuned and refined iteratively using the 1D computational model, after which they were successfully deployed on the experimental setup. Future work concerns scaling up the oxidation system for larger rates of energy extraction, further analysis of optimal reactor startup procedures, and alternative controller formulations.