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Ronald J. Pugmire, Chair
Thomas H. Fletcher, Assoc. Chair
INTRODUCTION
Coal pyrolysis or devolatilization and char oxidation play key roles in nearly all coal conversion processes of current or potential commercial interest (combustion, gasification, carbonization, etc.). In spite of many years of active research in these fields and the existence of several working models, a clear consensus is only now beginning to emerge on the nature of coal pyrolysis and char oxidation. Moreover, experimental data needed to model these processes, particularly as they occur in the combustion of U.S. coals, are either fragmented or generally lacking. Gas formation during pyrolysis can often be related to the thermal decomposition of bridge material and specific functional groups in the coal and can be predicted with reasonable accuracy by models employing first-order reactions with ultimate yields. On the other hand, tar and char formation is more complicated, and progress in mechanistic modeling of tar and char formation has been less successful. Tar yields vary substantially depending on reactor conditions (pressure, heating rate, final temperature, bed geometry, particle size, etc.). In combustion or gasification, tar is often the volatile product of highest initial yield and thus controls ignition and flame stability. It is also a precursor to soot, which is important to radiative heat transfer. Char surface properties and structure affect ignition, particle temperature, and carbon conversion, and hence boiler size. An understanding of the chemical reactions occurring in coal devolatilization and char oxidation is vital and the coupling of these reactions with heat and mass transport processes is critical for construction of a reliable combustion model.
OBJECTIVES AND APPROACH
Research in Thrust Area 1 has been tailored to understand and integrate the factors relating to devolatilization and char oxidation identified as key issues, but it also reflects capabilities of ACERC personnel. The overall objective of the research in Thrust Area 1 continues to be the development of submodels for fossil fuel devolatilization and char oxidation which: (1) relate to coal rank/ structure, (2) are coal general for a variety of (ACERC) coals, (3) are computationally efficient, and (4) can be integrated into the 2-D and 3-D codes.
Development of operational coal devolatilization, char oxidation, soot formation, and NOx release submodels is pursued through an integrated approach of model development and experimental work to support the comprehensive code development. The experimental work is of two types: (1) development of fundamental knowledge of coal and char structure and properties; and (2) applied experiments that provide sufficient data for verification of the models and identification of mechanistic relationships for incorporation into the models.
No single laboratory or program can address all of the relevant problems. The approach in Thrust Area 1 is based on utilization of resources available in ACERC together with collaborative efforts with researchers in other laboratories. With the present collaboration and utilization of new as well as existing data, good progress is being made on the key issues to achieve the stated objectives. In addition to substantial knowledge-based results relating to coal structure, kinetic mechanisms and rates, advanced, structure-based coal devolatilization and char oxidation submodels have been developed.
RELATIONSHIP TO ACERC MISSION
The success of ACERC will, in part, be measured by its capacity to meet the needs of the combustion industry by means of a robust, reliable, efficient 3-D combustion code. The success of this code depends on reliable, efficient submodels that adequately describe devolatilization and char oxidation behavior for a wide range of coal types. The development of adequate submodels requires a detailed understanding of coal structure, lattice statistics, coal/char/tar/gas structural relationships, and the dynamic nature of the lattice/volatile production. The effects of mineral matter must also be evaluated and factored into the evolution of the organic substituents if the behavior of the latter are to be adequately understood. Results from this thrust area are critical for the development and evaluation of submodels which adequately describe the role played by the fuel in the 3-D comprehensive furnace model.
ANTICIPATED PRODUCTS
The important research products anticipated from this thrust area include the following:
ACTIVE RESEARCH PROJECTS
| No. | Project Title | Principal Investigator(s) | Univ. | Class.1 |
| 1A | NMR Analysis of Coal and Char Structure 2 | Ronald Pugmire/David Grant | U of U | Fund., Foc. |
| 1B | Mechanisms & Kinetics of Rapid Devolatilization 2 | Henk Meuzelaar | U of U | Fund., Exp. |
| 1C | Chem. Characterization of Coals & Comb. Products 2 | Milton Lee | BYU | Fund., Exp. |
| 1D | Char Oxidation 2 | William Hecker | BYU | Fund., Foc. |
| 1F | Production of Char/Tar/Gas Samples 4 | Tom Fletcher | BYU | Fund., Foc. |
| 1K | High Pressure Oxidation Rates 7 | P. Radulovic/D. Smoot | BYU | Fund., Foc. |
| 1L | Devolatilization Submodel Development 5 | David Grant | U of U | Fund., Foc. |
| 1N | Soot Formation 9 | Thomas Fletcher/Brent Webb | BYU | Fund., Foc. |
1 Fund.=Fundamental, App.=Applied 2 Initiated First Year 4 Initiated Third Year 6 Pending 8 Initiated Fifth Year 10 Initiated Eighth Year
Exp.=Exploratory, Foc.=Focused 3 Initiated Second Year 5 Initiated Fourth Year 7 Other Funding 9 Initiated Sixth Year 11 Initiated Ninth Year
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