Simulation of soot formation using particle dynamics with one dimensional nucleation mode

Journal ArticleTwo soot formation models using particle dynamics with one-dimensional nucleation mode directly coupled with gas phase chemistry are tested on three ethylene and three methane laminar premixed flames. These models demonstrate strength in the prediction of concentration profiles of major combustion products and critical intermediates, and the characteristics of soot particles. These models extend the practicability of simulation beyond the prediction of soot volume fraction and estimate the mean particle diameter quite well especially for methane flames. In particular, our second model expands the range of fuels that can be simulated, and also correctly predicts the effects of C/O ratio on the soot formation process. The strength and weakness of these models are investigated and new features are identified for the development of next generation of soot models

Transformation of coal mineral matter during pulverized coal combustion

The theoretical development of a sequence of mathematical sub-models capable of calculating the fouling tendency of a coal based on microscopic analysis of the coal mineral matter is described. The sub-models interpret computer controlled-scanning electron microscope analysis data in terms of mineral size and chemical composition distributions; follow the transformation of these mineral property distributions during the combustion of the coal; determine the probability of the resultant fly ash particles impacting on boiler-tube surfaces and of their sticking upon impaction. The sub-models are probabilistic, and take account of the particle-to-particle variation of coal mineral matter and fly ash properties by providing mean values and variances for particle size, chemical composition and viscosity. The various sub- models are combined into a Coal Fouling Tendency (CFT) computer code. Comparison of CFT modeling results obtained for any coal or coal blend with those obtained for a coal whose behavior in a given boiler plant is known, can give useful information on their relative fouling tendencies. The report also includes data on the deposition characteristics of five coals or coal blends, obtained from combustion experiments in the 1-2 MW flame tunnel at MIT. The measurement data were used for validation of the CFT calculations, and for ranking the five fuels with respect to their fouling behavior. Similar ranking of other coals, without combustion testing, can be based solely on results from the CFT model, and examples are given in the report.New England Power Service Co., ABB-Combustion Engineering, Public Service Electric & Gas Co., Empire State Electric Energy Research Corp., ENEL S.p.A., and Electric Power Research Institut

Numerical combustion of aviation fuel part I: a cross-model comparison of n-heptane premixed flame

Journal ArticleFour different n-heptane mechanisms were used to simulate a fuel rich n-heptane premixed flame and their results were compared with experimental measurements. In addition to discussion of the numerical performance of each mechanism, flux analysis coupled with the atomic distribution technique was used to find the major reaction pathways for fuel consumption, product formation, and the evolution of olefins and other intermediates. Hydrogen abstraction followed by B scission is the major fuel consumption route overtaken by unimolecular decomposition only at 1400-1500K. At that high temperature, however, not much fuel remains so that unimolecular decomposition reactions contribute insignificantly toward the overall fuel decomposition process. Low temperature chemistry of peroxy radicals forms a minor fuel consumption route in this premixed flame. Olefins are formed by B scission and consumed by direct decomposition, radical addition, and hydrogen abstraction reactions. The techniques and pitfalls of flux analysis were also discussed in order to map out a methodology that can be used to identify the true nature of the combustion chemistry. The results obtained from this study for n-heptane is critical to build practical combustion mechanisms for large paraffins, which are major components of liquid aviation transportation fuels. It should be recognized that the conclusions derived here arc for premixed flames, and may not apply to diffusion flames

Muiltifunctional fuel additives for reduced jet particlate emissions

ReportUsing Government drawings, specifications, or other data included in this document for any purpose other than Government procurement does not in any way obligate the U.S. Government. The fact that the Government formulated or supplied the drawings, specifications, or other data does not license the holder or any other person or corporation; or convey any rights or permission to manufacture, use, or sell any patented invention that may relate to them

Combustion generated fine carbonaceous particles

Soot is of importance for its contribution to atmospheric particles with their adverse health impacts and for its contributions to heat transfer in furnaces and combustors, to luminosity from candles, and to smoke that hinders escape from buildings during fires and that impacts global warming or cooling. The different chapters of the book adress comprehensively the different aspects from fundamental approaches to applications in technical combustion devices

Direct catalytic decomposition of nitric oxide

This project investigates a suitable catalyst system for the direct NO decomposition in post-combustion gas streams. The process does not use a reductant, such as the ammonia used in Selective Catalytic Reduction (SCR) of NO[sub x] to nitrogen. Therefore, it is a greatly simplified process basically involving passing the flue gas through a catalytic converter. Catalysts are prepared by incorporating metal cations into zeolite supports according to ion exchange procedures widely used in preparation of metal/zeolite catalysts. The catalysts of primary interest include copper, palladium, silver, and nickel exchanged ZSM-5 catalysts. Particular emphasis is given in this work on promoted Cu-exchanged zeolites, especially the catalyst system Mg/Cu-ZSM-5 and a few others, which are promising for NO conversion to nitrogen at typical flue gas O[sub 2] and NO levels and over the temperature range of 723--873K. Effects of zeolite modification, copper exchange level and catalyst preparation conditions on the catalyst activity are studied in a packed-bed microreactor. Temperature-programmed desorption (TPD) and reduction (TPR) experiments will be carried out in a thermogravimetric analyzer and a single-particle electrodynamic balance (EDB). Kinetic studies of NO and O[sub 2] interaction with catalysts over a wide temperature range as well as catalyst structural investigations are planned

Effects of Catalytic Mineral Matter on CO/CO sub 2 ratio, Temperature and Burning Time for Char Combustion

In this program we are measuring the CO{sub 2}/CO ratio for both catalyzed and uncatalyzed chars over a wide range of temperature. These results will then be used to develop predictive models for char temperature and burning rates. In this report progress on modeling particle temperature under conditions where ignition occurs is reported. A comparison of preliminary modeling results with experimental results is also reported. 11 refs., 4 figs

Mechanistic and Kinetic Studies of High-Temperature Coal Gas Desulfurization Sorbents

During this quarter work on zinc titanate materials as sorbents for fuel gas desulfurization continued. On the basis of the completed parametric studies of reduction and sulfidation (effects of H{sub 2}, H{sub 2}O, see quarterly reports {number sign}7, 8), ZnO and Zn-Ti-O materials were evaluated in terms of reduction-sulfidation kinetic differences. Comparative Arrhenius plots of the initial reduction and sulfidation rates are shown for the sorbents ZnO, Z2T-a (2Zn:1Ti) and Z2T3-a (2Zn:3Ti). The reduction rate is shown for a gas containing (mol) 10%H{sub 2}-3%H{sub 2}O-87%N{sub 2}, while sulfidation is for 2%H{sub 2}S-98%N2. The point at which the initial reduction rate becomes faster than sulfidation rate is 848,872 and 942{degree}C, respectively, for ZnO, Z2T-a and Z2T3-a. Therefore, Zn-Ti-O solids can be used for the desulfurization of coal-derived fuel gas at higher temperatures than single ZnO. To determine the regenerability of Zn-Ti-O solids and their sulfidation performance after regeneration, two cycles of consecutive sulfidation-regeneration were performed with ZnO and Z2T-a. 2 figs

FT-IR and H-NMR characterization of the products of an ethylene inverse diffusion flame

ABSTRACT: Knowledge of the chemical structure of young soot and its precursors is very useful in the understanding of the paths leading to soot particle inception. This paper presents analyses of the chemical functional groups, based on FT-IR and 1H NMR spectroscopy of the products obtained in an ethylene inverse diffusion flame. The trends in the data indicate that the soluble fraction of the soot becomes progressively more aromatic and less aliphatic as the height above the burner increases. Results from 1H NMR spectra of the chloroform-soluble soot samples taken at different heights above the burner corroborate the infrared results based on proton chemical shifts (Ha, Hα, Hβ, and Hγ ). The results indicate that the aliphatic β and γ hydrogens suffered the most drastic reduction, while the aromatic character increased considerably with height, particularly in the first half of the flame. © 2006 The Combustion Institute. Published by Elsevier Inc. All rights reserved