MIT Libraries logoDSpace@MIT

MIT
View Item 
  • DSpace@MIT Home
  • MIT Libraries
  • MIT Theses
  • Doctoral Theses
  • View Item
  • DSpace@MIT Home
  • MIT Libraries
  • MIT Theses
  • Doctoral Theses
  • View Item
JavaScript is disabled for your browser. Some features of this site may not work without it.

High-temperature microfluidic systems for thermally-efficient fuel processing

Author(s)
Arana, Leonel R
Thumbnail
DownloadFull printable version (25.72Mb)
Other Contributors
Massachusetts Institute of Technology. Dept. of Chemical Engineering.
Advisor
Klavs F. Jensen.
Terms of use
M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission. http://dspace.mit.edu/handle/1721.1/7582
Metadata
Show full item record
Abstract
Miniaturized fuel cell systems have the potential to outperform batteries in powering a variety of portable electronics. The key to this technology is the ability to efficiently process an easily-stored, energy-dense fuel. In many cases, use of these fuels requires a fuel processor-a high temperature chemical reactor that generates a hydrogen-rich stream for use by the fuel cell. In high-temperature microfluidic systems, where heat transfer rates are often very high, thermal management is a major challenge. This thesis investigates the use of silicon microfabrication technology to fabricate high-temperature submillimeter-scale fuel processors designed to maximize thermal efficiency. A prototype MicroElectroMechanical Systems (MEMS) chemical reactor/heat exchanger for fuel processing has been designed and fabricated. The fuel processor, measuring 8x 10x 1.5 mm, consists of thin-walled silicon nitride tubes and a suspended silicon reaction zone. This structure couples the energy between catalytic combustion and decomposition or steam reforming reactions to produce hydrogen. The design enables a high level of thermal isolation of the reaction zone while allowing heat exchange between process streams. Thermal management in the fuel processors has been characterized up to 825⁰C through experimental testing using integrated resistive heaters and temperature sensors and through finite element modeling. Catalyst localization, for controlled catalytic combustion of premixed fuels in the reaction zone, has been achieved using passive fluidic stop valves. Ammonia decomposition (cracking) and combustion of various fuels over washcoated supported-metal catalysts have been investigated.
 
(cont.) Using the energy provided by the integrated heater to drive the reaction, up to 1.6 WLHV (based on the lower heating value) of hydrogen has been produced by catalytic ammonia decomposition at temperatures exceeding 800⁰C. Hydrogen burns stably in stoichiometric mixtures with air to >99% conversion for flow rates of hydrogen between 2 and 12 ml-min-1 and steady-state reactor temperatures between 400 and 930⁰C. At higher hydrogen flow rates and reactor temperatures, homogeneous combustion has been observed. Self-sustained (autothermal) combustion of butane at atmospheric pressure and ammonia under reduced ambient pressure (down to 4 Pa) have also been demonstrated. Hydrogen has been produced via ammonia decomposition using energy from hydrogen, butane, and ammonia combustion to drive the reaction.
 
Description
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2003.
 
Includes bibliographical references (p. 231-238).
 
Date issued
2003
URI
http://hdl.handle.net/1721.1/7995
Department
Massachusetts Institute of Technology. Department of Chemical Engineering
Publisher
Massachusetts Institute of Technology
Keywords
Chemical Engineering.

Collections
  • Doctoral Theses

Browse

All of DSpaceCommunities & CollectionsBy Issue DateAuthorsTitlesSubjectsThis CollectionBy Issue DateAuthorsTitlesSubjects

My Account

Login

Statistics

OA StatisticsStatistics by CountryStatistics by Department
MIT Libraries
PrivacyPermissionsAccessibilityContact us
MIT
Content created by the MIT Libraries, CC BY-NC unless otherwise noted. Notify us about copyright concerns.