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Radiative Properties Of Char Fly Ash And Soot Particles In Coal Flames Quarterly Report No Vi December 15 1993 March 15 1994
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Book Synopsis Radiative Properties of Char, Fly-ash, and Soot Particles in Coal Flames. Quarterly Report No. VI, December 15, 1993--March 15, 1994 by :
Download or read book Radiative Properties of Char, Fly-ash, and Soot Particles in Coal Flames. Quarterly Report No. VI, December 15, 1993--March 15, 1994 written by and published by . This book was released on 1994 with total page 23 pages. Available in PDF, EPUB and Kindle. Book excerpt: In combustion systems, particulate matter such as soot, ash, char, as well as combustion gases such as water vapor, carbon dioxide and carbon monoxide participate to radiative heat transfer. In general, the radiative properties of particles are much more important than that for combustion gases because particles absorb, emit and scatter radiation continuously in the entire wavelength spectrum. By contrast, combustion gases participate radiatively only in narrow bands centered around discrete wavelengths. The radiative properties required for typical radiative transfer calculations are absorption and scattering coefficients and scattering phase function. These properties are dependent on the partial pressures and chemical composition of combustion gases, material and physical structure, size, and volume fraction distributions of particles, and of course on the wavelength of the incident radiation. The main objective of this project is to estimate the volume fractions of combustion products by observing their scattering and absorption behaviour when subjected to external electromagnetic radiation.
Book Synopsis Radiative Properties of Char, Fly-ash, and Soot Particles in Coal Flames. Quarterly Report No. 5, September 15--December 15, 1993 by :
Download or read book Radiative Properties of Char, Fly-ash, and Soot Particles in Coal Flames. Quarterly Report No. 5, September 15--December 15, 1993 written by and published by . This book was released on 1993 with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt: The soot formation model formulated in this study is a simple one and considered mainly to determine the order-of-magnitude variations of soot volume formation distribution in a flame. To this extent the model is considered sufficient. First of all, the soot formation is to be coupled closely with the chemical kinetics models. Recent studies suggest that acetylene formed during the combustion of heavy hydrocarbons play a key role in the formation of PAH molecules and in soot inception. Lindstedt and his coworkers (Fairweather et al., 1992; Leung et al., 1992) used a flamelet model and considered global reactions for soot formation. They derived instantaneous relationships between mixture fraction, density, temperature, and gaseous composition of a combusting mixture. Leung et al. (1991) suggested a four-step soot formation/destruction mechanism, and they connected it to the presence of intermediate pyrolysis products, primarily to acetylene. Two separate competing mechanisms were thought to be responsible from soot mass formation: the formation of incipient particles and the particle surface growth due to adsorption of acetylene molecules.
Book Synopsis Radiative Properties of Char, Fly-ash, and Soot Particles in Coal Flames. Technical Progress Report, December 15, 1994--March 30, 1995 by :
Download or read book Radiative Properties of Char, Fly-ash, and Soot Particles in Coal Flames. Technical Progress Report, December 15, 1994--March 30, 1995 written by and published by . This book was released on 1996 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this paper we present a methodology for measuring the elements of the Mueller (Scattering) matrix, which in turn can be used to determine the size of soot monomers and agglomerates in flames. The experimental system to be used is composed of two linear polarizers, two quarter wave plates and a half wave plate along with a light source (Nd:YAG Laser). The preliminary independent parameters in this setup are the polarizer angles?1,?2 and the retarder angles?1,?2 and?3, which can be varied to obtain different condition numbers (CN). If the CN is large, then the Mueller matrix elements determined from experiments would not be reliable. However by using a proper set of? and? values, one can reduce the CN to be less than 10. This concept is discussed for different fractal-like soot agglomerates. It is shown that even if there is ±7.5% error in measured intensities, the recovered S11 and S12 elements are virtually identical to the true values. These S{sub ij} elements can be used in an inverse algorithm to identify the size of soot monomers and agglomerates.
Book Synopsis Radiative Properties of Char, Fly-ash, and Soot Particles in Coal Flames. Quarterly Reports 1 and 2, September 15, 1992--March 15, 1993 by :
Download or read book Radiative Properties of Char, Fly-ash, and Soot Particles in Coal Flames. Quarterly Reports 1 and 2, September 15, 1992--March 15, 1993 written by and published by . This book was released on 1993 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this research program is to determine (a) the radiative properties of coal particles, and (b) concentration distribution of char, fly-ash and soot particles in coal laden gaseous flames. During the first six months, we have concentrated on determining the effective optical and radiative properties of coal particles. This information is necessary to separate coal concentration from that of other particles. For this (1) in situ scattering and (2) ex situ spectrometer experiments were completed, and (3) a computer program was developed to model non-homogeneous, irregular shaped coal/char particles as radially inhomogeneous effective spheres. In addition to these studies, the new experimental system has been designed and built to perform the required experiments.
Download or read book Energy Research Abstracts written by and published by . This book was released on 1995 with total page 782 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Radiative Properties of Char, Fly-ash, and Soot Particles in Coal Flames. First Annual Report by :
Download or read book Radiative Properties of Char, Fly-ash, and Soot Particles in Coal Flames. First Annual Report written by and published by . This book was released on 1993 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report covers the first twelve months of the project {open_quotes}Radiative Properties of Char, Fly-Ash, and Soot Particles in Coal Flames{close_quotes}, that is from September 15, 1992 to September 15, 1993. The objectives of this project can be summarized as follows: (1) obtain the effective radiative properties of pulverized coal/char and soot particles, and (2) determine the concentration distribution of char, fly-ash, and soot particles in coal laden flames as a function of different flame conditions. Research accomplishments in the following areas are described: effective properties of coal and char particles; multilayer sphere model; soot formation model; and soot radiative properties. The experiments are described and plans for future work are outlined.
Book Synopsis Radiative Properties of Char, Fly-ash, and Soot Particles in Coal Flames. Technical Progress Report, Second Year, October 1994--December 1994 by :
Download or read book Radiative Properties of Char, Fly-ash, and Soot Particles in Coal Flames. Technical Progress Report, Second Year, October 1994--December 1994 written by and published by . This book was released on 1995 with total page 23 pages. Available in PDF, EPUB and Kindle. Book excerpt: In large-scale coal-fired flames, radiative transfer is significant as a large portion of the energy generated during the char pyrolysis and soot oxidation is transferred to the surroundings by radiation (due to emission). The relatively cold gases and particles which are not burning yet are heated by this incoming energy (absorption), which may have originated not only from the immediate surroundings of the control volume of interest but the entire flame. It is obvious that if the emission and absorption of radiation in such a flame are not accounted for correctly, it is not possible to determine other underlying phenomena with accuracy, as the fundamental principle of conservation of energy would be violated. In order to consider the effect of radiation heat transfer in coal-fired furnaces, we have to (1) model the radiative transfer equation to satisfy the conservation of radiant energy principle; (2) use the correct radiative properties of combustion gases and particles; (3) account for the interaction of radiation with the flow and energy equations. The radiative properties for a participating medium of spherical particles can be expressed in terms of the spectral absorption, extinction, and scattering efficiencies and the phase function for a single particle, and can be calculated from the Lorenz-Mie theory. For small size particles, the expressions are based on the Rayleigh limit of Lorenz-Mie theory, and are significantly simpler. The details are readily available in the literature.
Book Synopsis Radiative Properties of Char, Fly-ash, and Soot Particles in Coal Flames by :
Download or read book Radiative Properties of Char, Fly-ash, and Soot Particles in Coal Flames written by and published by . This book was released on 1994 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Government Reports Annual Index by :
Download or read book Government Reports Annual Index written by and published by . This book was released on 1994 with total page 1220 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Government Reports Announcements & Index by :
Download or read book Government Reports Announcements & Index written by and published by . This book was released on 1995 with total page 564 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Radiation-turbulence Interactions in Pulverized-coal Flames. Quarterly Report No. III, March 15, 1994--June 15, 1994 by :
Download or read book Radiation-turbulence Interactions in Pulverized-coal Flames. Quarterly Report No. III, March 15, 1994--June 15, 1994 written by and published by . This book was released on 1994 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: The work concerns the development of computer codes for the simulation of radiation turbulence interactions in coal flames. Experimental studies in tandem with the turbulence calculations are based on optical observation of scattered light from coal particles under combustion conditions.
Book Synopsis Measurement and Analysis of Radiative Properties of Fly-ash Particles in Pulverized Coal Furnaces and Their Effect on Heat Transfer by : Allen Lowe
Download or read book Measurement and Analysis of Radiative Properties of Fly-ash Particles in Pulverized Coal Furnaces and Their Effect on Heat Transfer written by Allen Lowe and published by . This book was released on 1978 with total page 202 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Radiation Properties of Coal Combustion Products by :
Download or read book Radiation Properties of Coal Combustion Products written by and published by . This book was released on 1990 with total page 43 pages. Available in PDF, EPUB and Kindle. Book excerpt: An assessment is made of the experimental data and the theoretical bases for determining the absorption and scattering coefficients of the coal products of combustion. Particular attention is devoted to the complex refractive indices for char and ash. A dispersion relation is developed from sparse extinction data that can be used to estimate the optical constants of char. Considerable uncertainty and scatter is found in the literature data on ash optical constants and is attributed to variability in ash composition, lack of experimental rigor and limitations in the data reduction procedures. A correlation is presented for estimating the complex refractive indices of ash as a function of its mineral composition. A parametric study is conducted to elucidate the role of char, soot and ash particulates in determining the radiation properties of coal flames. The effects of combustion particulates are discussed in terms of the modification of the band structure of gas radiation to a luminous spectrum, introduction of scattering in radiation transport, particle size distribution, particle loading and particle composition. The results are interpreted as possible effects of coal beneficiation, coal micronization and flyash composition on heat transfer to the water walls of a coal furnace. 19 refs., 13 figs., 10 tabs.
Book Synopsis Radiation Turbulence Interactions in Pulverized Coal Flames. Technical Progress Report, Third Year, Second Quarter, December 15, 1995--March 15, 1996 by :
Download or read book Radiation Turbulence Interactions in Pulverized Coal Flames. Technical Progress Report, Third Year, Second Quarter, December 15, 1995--March 15, 1996 written by and published by . This book was released on 1996 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this paper, the authors discuss an experimental and theoretical methodology to characterize soot volume fraction fluctuations in turbulent diffusion flames via chaotic maps. The approach is based on the hypothesis that the fluctuations of properties in turbulent flames is deterministic in nature, rather than statistical. To this extent, the authors measured the time series of soot scattering coefficient in an ethylene diffusion flame from light scattering experiments. Following this, corresponding power spectra and delay maps were calculated. It was shown that if the data were averaged, the characteristics of the fluctuations were almost completely washed out. The psds from experiments were successfully modeled using a series of logistic maps.
Book Synopsis Suppression of Fine Ash Formation in Pulverized Coal Flames. Quarterly Technical Progress Report No. 6, January 1, 1994--March 31, 1994 by :
Download or read book Suppression of Fine Ash Formation in Pulverized Coal Flames. Quarterly Technical Progress Report No. 6, January 1, 1994--March 31, 1994 written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: During the present quarter the model was coded and tested on the Illinois coal. Some features of the process need discussion. After devolatilization, the char particle heats towards its steady-state combustion temperature. At approximately 1200--1300 K, the particle quickly goes from a temperature where the equilibrium sodium vapor pressure is negligible to a temperature where it is at one atmosphere. This shows that the sodium vaporization occurs under non-isothermal conditions, although the rapid rate of sodium diffusion relative to particle heating suggests that the quasi steady-state formulation for the sodium vaporization portion of the problem is appropriate. It also illustrates the two-stage release pattern for the sodium: (1) an early rapid release of organically-bound sodium, and (2) a more delayed release of acid-washable sodium, and sodium that was complexed into clay chemicals during the organic sodium vaporization. The conditions reported for the present calculations are as follows: Coal: 8.7% ash, 12% H[sub 2]O, 33.5% volatile matter. Elemental sodium represent 0.82% of the ash. For purposes of calculation, the char particle is presumed to consist of the fixed carbon from the proximate analysis, along with the ash. This establishes the mass fraction of sodium and other minerals in the char at the start of char combustion. For the baseline condition, the char particle was assumed to be 50% covered by attached excluded mineral, and the included mineral matter was assumed to be divided into monodisperse 0.5 [mu]m particles that are evenly dispersed throughout the char. The diameter of the char particle was 25 [mu]m.
Book Synopsis Suppression of Fine Ash Formation in Pulverized Coal Flames. Quarterly Technical Progress Report No. 3, April 1, 1993--June 30, 1993 by :
Download or read book Suppression of Fine Ash Formation in Pulverized Coal Flames. Quarterly Technical Progress Report No. 3, April 1, 1993--June 30, 1993 written by and published by . This book was released on 1993 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: One of the major obstacles to the economical use of coal is managing the behavior of its mineral matter. Ash size and composition are of critical importance for a variety of reasons. Fly ash size and emissivity affect radiant furnace heat transfer. Heat transfer is also affected by the tendency of ash to adhere to heat transfer surfaces, and the properties of these deposits. Removal of ash from flue gas by electrostatic precipitators is influenced by both particle size and particle resistivity. The efficiency of fabric filter-based cleaning devices is also influenced by ash size. Both types of devices have reduced collection efficiencies for smaller-sized particles, which corresponds to the size most efficiently retained in the alveolar region of the human lung. Laboratory work and studies of full-scale coal-fired boilers have identified two general mechanisms for ash production. The vast majority of the ash is formed from mineral matter that coalesces as the char burns, yielding particles that are normally larger than 0.5 [mu]m. The second major mechanism is the generation of a submicron aerosol through a vaporization/condensation mechanism. Although these particles represent a relatively small fraction of the mass, they can present a large fraction of the surface area. Thus, they are a preferred site for the condensation of the more volatile oxides later in the furnace. This leads to a layering effect in which the refractory oxides are concentrated at the particle core and the more volatile oxides reside at the surface. This also explains the enrichment of the aerosol by volatile oxides that has been noted in samples from practical furnaces. These volatile metal oxides include the majority of the toxic metal contaminants, e.g., mercury, arsenic, selenium and nickel. Risk assessment studies suggest that toxic metal emissions represent a significant portion of the health risk associated with combustion.
Book Synopsis Determination of Local Radiative Properties in Coal-fired Flames. Technical Progress Report, September 15, 1987--September 15, 1988 by :
Download or read book Determination of Local Radiative Properties in Coal-fired Flames. Technical Progress Report, September 15, 1987--September 15, 1988 written by and published by . This book was released on 1988 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recently, an extensive, in-depth review of the modeling of radiation heat transfer in combustion chambers has been prepared (Viskanta and Menguc, 1987); therefore, there is no need to repeat that material here. It is already known that the most important missing link in the prediction of radiation heat transfer in combustion systems is the lack of detailed information about the optical and physical properties of combustion products (Viskanta and Menguc, 1987). The purpose of this research is to determine the radiative properties of coal particles. Considering the uncertainty in the fundamental optical and physical properties of coal particles, such as complex index of refraction, size, size distribution, and shape, it is difficult to predict the radiative properties of particles using available analytical methods, such as Lorenz-Mie theory. For a better understanding of radiation and radiation/combustion or radiation/turbulence interactions, it is preferable to determine the radiative properties in situ.
