Date of Award

8-2001

Document Type

Thesis

Department

Chemical Engineering

Abstract

The Energy and Environmental Research Center (EERC) in Grand Fork:, Morth Dakota is administering the research on the Transport Reactor Development Unit (TRDU) optimization project. This endeavor is sponsored by the Department of Energy, and it has an ultimate goal to justify the transition to a scaled-up version of the TRDU.

The focus of this research was to kinetically model char gasification in the TRDU, which will help define control parameters and optimize production. Kinetic parameters of char were determined with the use of Thermogravimetry (TGA). TGA is a thermal analysis and involves studying the change in the mass of the reacting species versus time.

A North Dakota Freedom lignite coal was used in this study. Freedom lignite is abundant, economical to gasify in North Dakota, and easier to gasify than coals with a higher fixed carbon content. The results show that at least 20 percent of the Freedom lignite is gasified at 815°C, 135 psig, six percent steam concentration, and a 45 second solids residence time of a single recycle pass in the transport reactor.

Previous analysis of TGA data by others assumed gasification was only dependent on fractional carbon conversion. Re-analysis of the TGA raw data showed that gasification depends on steam concentration as well, and not solely on fractional carbon conversion. No order dependence was observed for the other gases present (CO, CO2, H2, CH4). The TGA data only spans a range of steam concentrations up to an equivalent TRDU steam concentration of six percent. The TRDU operates at concentrations as high as 17 percent. Therefore, research on higher steam concentrations, representative of conditions in the TRDU, is necessary to obtain a more accurate model.

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