A kinetic model for pyrite transformations in a combustion environment

Srinivasachar, S.; Boni, A.A.

doi:10.1016/0016-2361(89)90116-6

Cited by 90 publications

(62 citation statements)

References 6 publications

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“…If the particle temperature is less than the pyrrhotite melting point (1356 K) the oxidation kinetics are given by Equation 4 using the appropriate particle temperature (inherent or extraneous). The parameters, ~ and E p ' were 5x10 9 cm sec-1 and 150 kJ mole-1 as proposed by Srinivasachar et al (1989) from work by Asaki et al (1985). (4) The gas mass transfer coefficient (~) is that given by equation 5 using the…”

Section: Iron Oxide Formationmentioning

confidence: 99%

“…or liquid, mass transfer coefficient used for this work was also proposed by Srinivasachar et al (1989). This coefficient depends on several unknown parameters, such as the recirculating rate inside the particle and liquid phase diffusivities.…”

Section: Iron Oxide Formationmentioning

confidence: 99%

“…These parameters, seen in Table 5.7.1, include the peak gas temperature (and the gas temperature profile), the coal composition, and the stoichiometric ratio This fit is especially good for the superstoichiometric cases, but fails slightly at the lower stoichiometries and particle temperatures. This behavior may be due to the use of the liquid/solid mass transfer coefficient derived by Srinivasachar et al (1989).…”

Section: Particle Enerty 831ancesmentioning

confidence: 99%

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The partitioning of iron during the combustion of pulverized coal

Bool

Peterson

Wendt

1995

Combustion and Flame

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Section: Iron Oxide Formationmentioning

confidence: 99%

Section: Iron Oxide Formationmentioning

confidence: 99%

Section: Particle Enerty 831ancesmentioning

confidence: 99%

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The partitioning of iron during the combustion of pulverized coal

Bool

Peterson

Wendt

1995

Combustion and Flame

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“…These experimental observations, when coupled with those in the previous quarterly report, suggested that the ratelimiting step of pyrite combustion changes with the extent of conversion. The pyrite oxidation pathway proposed in the new model differs from that of the prevailing model [2]. Srinivasachar and Boni's model was based on the following transformations:…”

Section: Technical Progress During Current Quarter Summarymentioning

confidence: 99%

Mechanisms of pyrite oxidation to non-slagging species. Quarterly report, January 1, 1995--March 31, 1995

Akan-Etuk¹,

Mitchell²

1995

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Phone: 415-725-2015 RESEARCH OBJECTIVESThis document is the third quarterly status report on a project conducted at the High Temperature Gasdynamics Laboratory at Stanford University, Stanford, California and concerned with enhancing the transformation of iron pyrite to non-slagging species during staged, low-NOX pulverized coal (P. C.) combustion. The research project is intended to advance PETC's efforts to improve our technical understanding of the high-temperature chemical and physical processes involved in the utilization of coal. The work focuses on the mechanistic description and rate quantification of the effects of fuel properties and combustion environment on the oxidation of iron pyrite to form the non-slagging species magnetite. The knowledge gained from this work is intended to be incorporated into numerical codes that can be used to formulate anti-slagging strategies involving minimal disturbance of coal combustor performance. This project is to be performed over the three-year period from September 1994 to August 1997.The project aims to identify the mechanisms of pyrite combustion and to quantify their effects, in order to formulate a general rate expression for the combustion of pyrite that accounts for coal properties as well as furnace conditions. Pyrite is introduced into a P. C. combustor as pure (extraneous) pyrite particles, pyrite cores within carbon shells, and inclusions in carbon matrices. In each case, once oxygen is transported to a pyrite particle's surface, the combustion of the pyrite involves the diffusion of oxygen from the particle's surface to its unreacted core and reaction of the diffused oxygen with the core. Consequently, a key feature of the program's approach to quantifying pyrite combustion is the sequential formulation of a reaction rate resistance network by isolating and quantifying the rate resistance induced by pyrite intraparticle mass transfer and pyrite intraparticle kinetics mechanisms.Crucial to the project's methodology is the utilization of feed materials with carefully controlled properties to eliminate the'uncertainty inherent in interpreting data obtained with natural coals (a consequence of the heterogeneity of natural coals). Homogeneous materials facilitate the modeling of specific combustion mechanisms without complications of non-uniform chemical composition and morphology.In general, the project has the following objectives: 1) the characterization of the various mechanisms of intraparticle mass transfer and chemical reaction that control overall pyrite combustion rates and 2) the synthesis of the reaction rate resistances of the various mechanisms into a general rate expression for pyrite combustion. The knowledge gained from this project will be incorporated into numerical codes and utilized to formulate slagging abatement strategies involving the minor adjustment of firing conditions. Ultimately, the benefit of this research program is intended to be an increase in the range of coals compatible with staged, low-NOX combustor retrofits. IFollowing...

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“…Excluded minerals are known to behave differently from included minerals which are intimately associated with the char combustion process. Srinivasachar and Boni (1989) recently developed a mathematical model to describe the transformations of excluded pyrite, a mineral form that is important in the slagging of boilers burning eastern coals. They found that, for the simulated conditions, approximately 80% of the total time required to oxidize pyrite to solid magnetite was spent in the molten phase.…”

mentioning

confidence: 99%

Measurement and modeling of advanced coal conversion processes, Volume I, Part 2. Final report, September 1986--September 1993

Solomon¹,

Serio²,

Hamblen³

1995

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we are grateful for their advice and technical guidance. We wish to acknowledge the significant contributions of Professor Eric M. Suuberg of Brown University in the areas of char reactivity, pyrolysis modeling and pyrolysis kinetics. Prof. Philip E. Best of the University of Connecticut made significant contributions in the areas of coal and char optical properties, modeling of coal viscosity and swelling, and FT-IR ernission/transmission (En) tomography. in addition to the authors listed on the title page, the Senior Investigators at Advanced Fuel Research, Inc. (AFR) included Ms. Sylvie Charpenay, Dr. Zhen-Zhong Yu, and Dr. Yuxin Zhao for subtask 2.a., Mr. James R. Markham for subtask 2.c., and Dr. Marek A. Wojtowicz for subtask 2.d. The preparations of the manuscript and illustrations was ably performed at AFR by Karin Dutton, Margaret Lane, and Lori Bellone. II.E.l-1.II . E . 1-2 .ll.E.2-I. ll.E.2-2. ll.E.2-3.ll.E.3-1.II.E.4-1.ll.E.6-1. I I . E.6-2.ll.E.6-3. I xv EXECUTIVE SUMMARYThe overall objective of this program was the development of a predictive capability for the design, scale up, simulation, control and feedstock evaluation in advanced coal conversion devices. This technology is important to reduce the technical and economic risks inherent in utilizing coal, a feedstock whose variable and often unexpected behavior presents a significant challenge. This program merged significant advances made at Advanced Fuel Research, Inc. (AFR) in measuring and quantitatively describing the mechanisms in coal conversion behavior, with technology developed at Brigham Young University (BYU) in comprehensive computer codes for mechanistic modeling of entrained-bed gasification. Additional capabilities in predicting pollutant formation were implemented and the technology was expanded to fixed-bed reactors.The foundation to describe coal-specific conversion behavior was AFRs Functional Group (FG) and Devolatilization, Vaporization and Crosslinking (DVC) models, developed under previous and on-going METC sponsored programs. These models have demonstrated the capability to describe the time dependent evolution of individual gas species, and the amount and characteristics of tar and char. The combined FG-DVC model was integrated with BYU's comprehensive two-dimensional reactor model for combustion and gasification, PCGC-2, and a one-dimensional model for fixed-bed gasifiers, FBED-I . The program included: i) validation of the submodels by comparison with laboratory data obtained in this program, ii) extensive validation of the modified comprehensive codes by comparison of predicted results with data from bench-scale and process scale investigations of gasification, mild gasification and combustion of coal or coal-derived products, and iii) development of well documented user friendly software applicable to a "workstation" environment. The progress during the program is summarized below.For Subtask 2.a., the processes described were: 1) tar formation mechanisms and kinetics; 2) gas formation mechanism...

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A kinetic model for pyrite transformations in a combustion environment

Cited by 90 publications

References 6 publications

The partitioning of iron during the combustion of pulverized coal

The partitioning of iron during the combustion of pulverized coal

Mechanisms of pyrite oxidation to non-slagging species. Quarterly report, January 1, 1995--March 31, 1995

Measurement and modeling of advanced coal conversion processes, Volume I, Part 2. Final report, September 1986--September 1993

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