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Articles 31 - 60 of 77
Full-Text Articles in Chemical Engineering
Char Combustion And Late Burnout Reactivity, Rhett Brewer, Dr. William Hecker
Char Combustion And Late Burnout Reactivity, Rhett Brewer, Dr. William Hecker
Journal of Undergraduate Research
To study the effects of the carbon structure on coal reactivity during the late stages of combustion, it was necessary to be able to know what effect mineral content had on the reactivity. Two coals, dietz (high mineral content) and pitt 8 (low mineral content), were chosen for the experiment so that their behavior during the late stages of combustion could be compared.
Coal Char-Co2 Gasification Measurements And Modeling In A Pressurized Flat-Flame Burner, Randy C. Shurtz, Thomas H. Fletcher
Coal Char-Co2 Gasification Measurements And Modeling In A Pressurized Flat-Flame Burner, Randy C. Shurtz, Thomas H. Fletcher
Faculty Publications
A pressurized flat-flame burner (PFFB) was used to conduct coal gasification studies. The PFFB was designed to provide an environment with laminar, dispersed entrained flow, with particle heating rates of ∼105 K/s, pressures of up to 15 atm, and gas temperatures of up to 2000 K. Residence times were varied from 30 to 700 ms in this study. Char gasification studies by CO2 were conducted on a subbituminous coal and 4 bituminous coals in the PFFB. Pressures of 5, 10, and 15 atm were used with gas compositions of 20, 40, and 90 mol % CO2. Gas conditions with peak …
Coal Swelling Model For Pressurized High Particle Heating Rate Pyrolysis Applications, Randy C. Shurtz, Joseph W. Hogge, Kade C. Fowers, Gregory S. Sorensen, Thomas H. Fletcher
Coal Swelling Model For Pressurized High Particle Heating Rate Pyrolysis Applications, Randy C. Shurtz, Joseph W. Hogge, Kade C. Fowers, Gregory S. Sorensen, Thomas H. Fletcher
Faculty Publications
A model was previously developed to describe the decrease in swelling during coal pyrolysis at atmospheric pressure when maximum particle heating rates increase from 104 K/s to 105 K/s. That model included effects of coal type using chemical structure properties. This paper presents results of new experiments to study the effects of elevated pressure and high heating rates on coal pyrolysis. A pressurized flat-flame burner (PFFB) was designed and built to conduct these studies. The pyrolysis experiments reported in this paper were conducted at particle heating rates of ∼105 K/s and maximum gas temperatures of 1700 to 1900 …
Analysis Of Coal By Static Time-Of-Flight Secondary Ion Mass Spectrometry (Tof-Sims), Lei Pei, Guilin Jiang, Larry Lin Baxter, Matthew R. Linford
Analysis Of Coal By Static Time-Of-Flight Secondary Ion Mass Spectrometry (Tof-Sims), Lei Pei, Guilin Jiang, Larry Lin Baxter, Matthew R. Linford
Faculty Publications
Coal remains a primary fuel for power generation. Herein we present time-of-flight secondary ion mass spectra (ToF-SIMS data) taken with a Ga primary ion beam from ca. 30 coal specimens. These commercially different coal specimens were obtained from coal mining companies and/or power plants. They represent all major coal types used in power generation (bituminous coals, subbituminous coals, and lignites), and include low-rank materials (lignites and subbituminouscoals), which are represented as a minor portion of the data. Often, inorganic ions (Na, Al, Si,and K) are pronounced in the spectra, overshadowing peaks from organic moieties. This reflectsthe high sensitivity of SIMS …
Effects Of Pressure On The Properties Of Coal Char Under Gasification Conditions At High Initial Heating Rates, Randy C. Shurtz
Effects Of Pressure On The Properties Of Coal Char Under Gasification Conditions At High Initial Heating Rates, Randy C. Shurtz
Theses and Dissertations
The effects of elevated pressure and high heating rates on coal pyrolysis and gasification were investigated. A high-pressure flat-flame burner (HPFFB) was designed and built to conduct these studies. The HPFFB was designed to provide an environment with laminar, dispersed entrained flow, with particle heating rates of ~10^5 K/s, pressures of up to 15 atm, and gas temperatures of up to 2000 K. Residence times were varied from 30 to 700 ms in this study. Pyrolysis experiments were conducted at particle heating rates of ~10^5 K/s and maximum gas temperatures of ~1700 K at pressures of 1 to 15 atm. …
Investigation Of An Iron-Based Additive On Coal Pyrolysis And Char Oxidation At High Heating Rates, John M. Sowa, Thomas H. Fletcher
Investigation Of An Iron-Based Additive On Coal Pyrolysis And Char Oxidation At High Heating Rates, John M. Sowa, Thomas H. Fletcher
Faculty Publications
Iron-based catalysts have been shown to enhance coal pyrolysis and char oxidation at low to moderate temperatures and heating rates (b1250 K and 1–1000 K/s). Such catalytic activity has not been demonstrated at high heating rates and temperatures approaching pulverized coal combustion applications. The effect of an iron-based additive on coal pyrolysis and char combustion was studied in a flat-flame burner system at high particle heating rates using a Kentucky bituminous coal. Pyrolysis and char reactivity of two treated coals with different catalyst loadings were studied and compared with the untreated coal. The total volatiles yield for the treated coals …
Coal Swelling Model For High Heating Rate Pyrolysis Applications, Randy C. Shurtz, Kolbein K. Kolste, Thomas H. Fletcher
Coal Swelling Model For High Heating Rate Pyrolysis Applications, Randy C. Shurtz, Kolbein K. Kolste, Thomas H. Fletcher
Faculty Publications
Thermal swelling of coal during pyrolysis strongly influences combustion and gasification rates. Coal swelling is known to vary strongly with coal rank, heating rate, and total pressure. New experiments confirm and clarify previous observations that maximum swelling occurs for high-rank bituminous coals at heating rates slightly below 104 K/s. Advanced swelling models based on bubble physics yield good qualitative trends at low heating rates, but they fail to predict observed decreases in coal swelling as particle heating rates increase beyond 104 K/s. An empirical swelling correlation for computational fluid dynamics (CFD) applications that correctly describes experimentally observed trends …
Investigation Of Nitrogen Release During Coal Pyrolysis In An Oxy-Fuel Combustion Process, John M. Sowa, Kolbein K. Kolste, Thomas H. Fletcher
Investigation Of Nitrogen Release During Coal Pyrolysis In An Oxy-Fuel Combustion Process, John M. Sowa, Kolbein K. Kolste, Thomas H. Fletcher
Faculty Publications
Three coals were studied in a flat flame burner (FFB) to determine nitrogen release during pyrolysis as a function of the temperature from 1600 to 1900 K in an oxy-fuel environment. The oxy-fuel environment was created by replacing the background N2 with CO2 in the FFB experiments. Both types of experiments were conducted under fuel-rich conditions, with no O2 present in the postflame gases. The oxy-fuel results were compared to previous results from FFB experiments in a N2 atmosphere. A bituminous coal showed no difference in mass and nitrogen release between the two environments. The sub-bituminous coal exhibited higher mass …
The Surface Characteristics And Reactivity Of Residual Carbon In Coal Gasification Slag, Xianglong Zhao, Cai Zeng, Yanyan Mao, Wenhua Li, Yun Peng, Tao Wang, Boris Eiteneer, Vladimir Zamansky, Thomas H. Fletcher
The Surface Characteristics And Reactivity Of Residual Carbon In Coal Gasification Slag, Xianglong Zhao, Cai Zeng, Yanyan Mao, Wenhua Li, Yun Peng, Tao Wang, Boris Eiteneer, Vladimir Zamansky, Thomas H. Fletcher
Faculty Publications
In a slagging entrained-flow coal gasifier, a large portion of the inorganic matter will form liquid slag that may have strong physical and chemical interactions with char. Understanding the char-slag interaction is important for improving the modeling and design of gasifiers. This paper reports the characteristics of residual carbon in both coarse and fine slag from a typical entrained-flow coal water slurry gasifier. The surface characteristics of slag and residual carbon in slag were evaluated by scanning electron microscopy and energy dispersive X-ray spectroscopy. The reactivity of the residual carbon in slag was compared through thermal gravimetric analysis. It was …
Studies Of Coal Nitrogen Release Chemistry For Oxyfuel Combustion And Chemical Additives, John M. Sowa
Studies Of Coal Nitrogen Release Chemistry For Oxyfuel Combustion And Chemical Additives, John M. Sowa
Theses and Dissertations
Pollution is one of the greatest concerns with pulverized coal combustion. With tightening standards on pollution emissions, more information is needed to create better design models. Burner modifications are the most efficient changes that can be made to assure sufficient carbon burnout and low NOx emissions. Experiments were performed in the BYU Flat Flame Burner (FFB) lab, operating under fuel rich conditions for pyrolysis experiments and fuel lean conditions for char oxidation experiments. Effects of temperature, coal rank, residence time, and post flame oxygen content on mass release, nitrogen release, and reactivity were examined. Elemental and Inductively coupled plasma (ICP) …
Modelling Of Coal Slag Flow And Layer Thickness In A High Temperature Entrained Flow Gasifier, H. Katalambula
Modelling Of Coal Slag Flow And Layer Thickness In A High Temperature Entrained Flow Gasifier, H. Katalambula
Tanzania Journal of Engineering and Technology (TJET)
A 2-D model for the slag flow simulation in an entrained flow gasifier has been developed. In addition to mass, momentum and energy conservation equations, volume of fluid (VOF) equation was solved to track the liquid-gas interface. Liquid phase consists of melted coal ash particles which deposits on the wall and move downward. The gasification reaction is not considered here but it is postulated to have a mass flow through the interface towards the mass of the liquid phase. The reactor walls are usually kept cold so a temperature gradient and then a solid layer form within the slag layer. …
Prediction Of Light Gas Composition In Coal Devolatilization, Ravichandra S. Jupudi, Vladimir Zamansky, Thomas H. Fletcher
Prediction Of Light Gas Composition In Coal Devolatilization, Ravichandra S. Jupudi, Vladimir Zamansky, Thomas H. Fletcher
Faculty Publications
The chemical percolation devolatilization (CPD) model describes the devolatilization behavior of rapidly heated coal based on the chemical structure of the coal. It predicts the overall char, tar, and light gas yields. This paper presents an improved CPD model with improved capability for predicting light gas composition. This is achieved by incorporating a kinetic model that simulates the release of various light gas species from their respective sources/functional groups in coal. The improved CPD model is validated using experiments with a wire mesh reactor and published experimental observations
The Effects Of Inorganic Solids And Certain Gases On The Thermal Decomposition Of Catechol, Jerome Apilan Robles
The Effects Of Inorganic Solids And Certain Gases On The Thermal Decomposition Of Catechol, Jerome Apilan Robles
LSU Doctoral Dissertations
In order to investigate the effects of calcium carbonate and iron oxide on the thermal decomposition of solid fuels, we have constructed an isothermal flow reactor to perform experiments on the model compound catechol (ortho-dihydroxybenzene), a phenol-type compound representative of coal, wood and biomass. Calcium carbonate and iron oxide are inorganic components of coal and wood, which have demonstrated catalytic properties in thermal reactions and are commercially used to enhance the conversion of solid fuels. In this study, the effects of the inorganic solids on pyrolysis and combustion are conducted through identification and quantification of the products formed after subjecting …
The Decompositioning Of Volatile-Matter Of Tanjung Enim Coal By Using Thermogravimetry Analyzer (Tga), Nukman Nukman
The Decompositioning Of Volatile-Matter Of Tanjung Enim Coal By Using Thermogravimetry Analyzer (Tga), Nukman Nukman
Makara Journal of Technology
The Decompositioning of Volatile-Matter of Tanjung Enim Coal by using Thermogravimetry Analyzer (TGA). Coal is a nature material which a kind of energy source. The decompotition of coal could analyze by heat treated using thermogravimetry analyzer. The decomposition of the volatile matter for three kinds of Tanjung Enim coal could be known. The value of activation energy that be found diference, then for Semi Anthracite, Bitumonius and Sub Bituminous Coal, the initial temperatures are 60.8 oC, 70.7 oC, 97.8oC, and the last temperatures are 893.8 oC, 832 oC, 584.6oC.
Mechanistic Investigation Of Ash Deposition In Pulverized-Coal And Biomass Combustion, Shrinivas Sadashiv Lokare
Mechanistic Investigation Of Ash Deposition In Pulverized-Coal And Biomass Combustion, Shrinivas Sadashiv Lokare
Theses and Dissertations
This investigation details the effects of fuel constituents on ash deposition through systematic experimental and theoretical analyses of fundamental particle experiments and a suite of fuels with widely varying inorganic contents and compositions. The experiments were carried out in the Multifuel Flow Reactor (MFR) at Brigham Young University. Fuels included several biomass fuels (straw, sawdust and mixtures of straw-sawdust with other additives such as Al(OH)3, CaCO3, etc.) and four commercially-used coals (Illinois#6, Powder River Basin – Caballo and Cordero, Blind Canyon, and Lignite – Beulah Zap). The data from the series of experiments quantitatively illustrate the effects of fuel properties, …
Influence Of Fb Conditions On Processes Within A Large Fuel Particle During Initial Phases Of Conversion, Milijana Paprika, Mirko Komatina, Franz Winter, Dragoljub Dakic
Influence Of Fb Conditions On Processes Within A Large Fuel Particle During Initial Phases Of Conversion, Milijana Paprika, Mirko Komatina, Franz Winter, Dragoljub Dakic
The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering
A theoretical study has been performed in order to investigate the interaction between fluidized bed (FB) temperature and original size of coal, and the pressure rise within a large coal particle during the initial phases of the combustion process. A mathematical model, describing the devolatilization process, has included the internal and external heat transfer, primary decomposition reactions and mass transfer. The model has shown how the FB temperature and original size of coal reflect on the pressure profile of the coal particle during the devolatilization. One of the major consequences of coal devolatilization in the fluidized bed is the primary …
Fuel-Nox Formation During Low-Grade Fuel Combustion In A Swirling-Flow Burner, Chunyang Wu
Fuel-Nox Formation During Low-Grade Fuel Combustion In A Swirling-Flow Burner, Chunyang Wu
Theses and Dissertations
Insufficient knowledge of fireside behavior in the near-burner region during biomass combustion is one of major factors preventing widespread use of this renewable fuel in pulverized coal power plants. The current research is aimed to investigate the impact of biomass cofiring on NO formation in the near-burner region through interpretation of computational fluid dynamics (CFD) predictions and data collected from a series of biomass tests in a pilot-scale (0.2 MW), swirling flow burner. Two-dimensional gas species mole fraction data were collected with state-of-theart instruments from nine experiments, composing one herbaceous biomass (straw), one woody biomass (sawdust), a low sulfur sub-bituminous …
Effects Of Pressure On Coal Pyrolysis At High Heating Rates And Char Combustion, Dong Zeng
Effects Of Pressure On Coal Pyrolysis At High Heating Rates And Char Combustion, Dong Zeng
Theses and Dissertations
Clean coal technologies are now becoming popular because of their high efficiencies and minimal environmental impact. Higher operating pressures have been applied to clean coal technologies. The effect of pressure on coal pyrolysis and char combustion has been extensively studied but still remains to be further explored. The objective of this project was to characterize high pressure, high heating rate coal pyrolysis and char combustion, with emphasis on improving coal/char high pressure combustion models. A flat-flame burner was used in a high pressure laminar flow facility to conduct high temperature, high heating rate pyrolysis and combustion experiments for four coals. …
The Inclusion Behaviothe Inclusion Behavior Of Sodium Compounds In Sub-Micron Particles Formed During Coal Combustionr Of Sodium Compounds In Sub-Micron Particles Formed During Coal Combustion, Iddi Mkilaha
Tanzania Journal of Engineering and Technology (TJET)
During combustion of coal, biomass and sewage sludge, metallic compounds especially alkali metals such as sodium and potassium vaporize and form fumes which are emitted with the exhaust gases. These fumes are corrosive to the turbine blades of power plants. To minimize corrosion, efforts have been made to control the condensation phase of these metals. In this study, the evolution and inclusion of sodium in sub-micron particles was investigated using a drop tube furnace and a low-pressure impactor (LPI). Four types of coal with different chemical properties were tested. The results suggest that a reaction-controlled mechanism and nucleation via chemical …
High-Pressure Coal Pyrolysis In A Drop Tube Furnace, Koichi Matsuoka, Zhi-Xin Ma, Hiroyuki Akiho, Zhan-Guo Zhang, Akira Tomita, Thomas H. Fletcher, Marek A. Wojtowicz, Stephen Niksa
High-Pressure Coal Pyrolysis In A Drop Tube Furnace, Koichi Matsuoka, Zhi-Xin Ma, Hiroyuki Akiho, Zhan-Guo Zhang, Akira Tomita, Thomas H. Fletcher, Marek A. Wojtowicz, Stephen Niksa
Faculty Publications
To obtain useful and reliable pyrolysis data under high pressures, continuous pyrolysis experiments were carried out using a drop tube furnace. To ascertain the reliability of data, a mass balance during pyrolysis was carefully checked. The pyrolysis data obtained in this equipment was compared with previous results, and it was found that the weight loss observed in the drop tube furnace was somewhat larger than those obtained with other apparatuses. The experimental results were compared with those predicted by three pyrolysis models. Although discrepancies between predictions and experimental results were observed under a certain condition, the agreement between the experimental …
High-Pressure Intrinsic Oxidation Kinetics Of Two Coal Chars, William C. Hecker, Peter M. Madsen, Michael R. Sherman, Jared W. Allen, Rebecca J. Sawaya, Thomas H. Fletcher
High-Pressure Intrinsic Oxidation Kinetics Of Two Coal Chars, William C. Hecker, Peter M. Madsen, Michael R. Sherman, Jared W. Allen, Rebecca J. Sawaya, Thomas H. Fletcher
Faculty Publications
Chars were produced from two coals (North Dakota lignite and Pittsburgh No. 8 hva bituminous coal) in a flat flame burner at atmospheric pressure. Intrinsic char reactivities to oxygen were then measured in a high-pressure thermogravimetric analyzer as a function of temperature, total pressure, and partial pressure of oxygen. Care was taken to avoid mass transfer effects. Reactivities were normalized by the available mass of char at any given time (g/(gavailâs)). Reactivity data were obtained over a wide range of char burnout and were found to be independent of burnout level between char burnouts of 20 and 60%. Data were …
Simulation Of Coal Pyrolysis In Plasma Jet By Cpd Model, Yajun Tian, Kechang Xie, Suyu Zhu, Thomas H. Fletcher
Simulation Of Coal Pyrolysis In Plasma Jet By Cpd Model, Yajun Tian, Kechang Xie, Suyu Zhu, Thomas H. Fletcher
Faculty Publications
Reaction of coal in a plasma jet is complex and extremely rapid, and acetylene and carbon monoxide are the main products in the pyrolysis gas. Coal pyrolysis is assumed as the first step reaction when coal is injected into hot plasma jet with initial average temperature of 3700 K. Chemical percolation devolatilization (CPD) is employed first to simulate this procedure in mechanism. The calculation results indicate coal pyrolysis rate in plasma jet is very fast and the retention time of coal staying in reactor is only several milliseconds. Comparing the calculation with experiment result, it was concluded that the CPD …
Transformations Of Coal-Derived Soot At Elevated Temperature, Thomas H. Fletcher, Jim Rigby, Jinliang Ma, Brent W. Webb
Transformations Of Coal-Derived Soot At Elevated Temperature, Thomas H. Fletcher, Jim Rigby, Jinliang Ma, Brent W. Webb
Faculty Publications
Coal pyrolysis experiments were performed in the post-flame region of a CH4/H2/air flat-flame burner operating under fuel-rich conditions, where the temperature and gas compositions were similar to those found in the near-burner region of an industrial pulverized coal-fired furnace. Volatiles released from the coal particles formed a cloud of soot particles surrounding a centrally fed coal/char particle stream. Soot samples were collected from the cloud at different residence times using a water-cooled, nitrogen-quenched probe. The soot samples were then analyzed for their elemental compositions of carbon, hydrogen, nitrogen, sulfur, and (by difference) oxygen plus inorganic matter. …
13-C Nmr Analysis Of Soot Produced From Model Compounds And A Coal, Mark S. Solum, Adel F. Sarofim, Ronald J. Pugmire, Thomas H. Fletcher, Haifeng Zhang
13-C Nmr Analysis Of Soot Produced From Model Compounds And A Coal, Mark S. Solum, Adel F. Sarofim, Ronald J. Pugmire, Thomas H. Fletcher, Haifeng Zhang
Faculty Publications
Soot samples, including the associated organics, produced from an Illinois No. 6 coal (five samples) and two model compounds, biphenyl (three samples) and pyrene (two samples), have been studied by 13C NMR methods. The coal soot data served as a guide to selection of the temperature range that would be most fruitful for investigation of the evolution of aerosols composed of soot and tars that are generated from model compounds. The evolution of the different materials in the gas phase followed different paths. The coal derived soots exhibited loss of aliphatic and oxygen functional groups prior to significant growth …
Nitrogen Transformations During Secondary Coal Pyrolysis, Haifeng Zhang, Thomas H. Fletcher
Nitrogen Transformations During Secondary Coal Pyrolysis, Haifeng Zhang, Thomas H. Fletcher
Faculty Publications
A CO/H2/O2/N2 flame was operated under fuel-rich conditions in a flat flame reactor to provide a high-temperature, oxygen-free environment to study secondary reactions of coal volatiles. The distributions of fuel nitrogen in the devolatilization products of four coals, ranging from high volatile bituminous to lignite, were obtained at gas temperatures ranging from 1159 to 1858 K. It was found that the initial nitrogen released was contained almost exclusively in the tar for all coals. Release of nitrogen from the char as light gases started at a later stage than tar nitrogen release. During secondary reactions, …
Solid-State 13c Nmr Characterization Of Matched Tars And Chars From Rapid Coal Devolatilization, Steven T. Perry, Eric M. Hambly, Thomas H. Fletcher, Mark S. Solum, Ronald J. Pugmire
Solid-State 13c Nmr Characterization Of Matched Tars And Chars From Rapid Coal Devolatilization, Steven T. Perry, Eric M. Hambly, Thomas H. Fletcher, Mark S. Solum, Ronald J. Pugmire
Faculty Publications
Matched tar/char sets were prepared by pyrolysis of a lignite and a bituminous coal in two entrained flow reactors at temperatures between 900 K and 1650 K and heating rates of 104–105 K/s. Detailed chemical structural characterization of these tars and chars was performed using elemental analysis and solid-state 13C NMR. This is the first set of detailed solid-state 13C nuclear magnetic resonance (NMR) data on coal tar samples. The average aromatic cluster sizes of the primary tars from these experiments are quite similar to those of their parent coals, confirming an assumption often made …
Modeling High Pressure Char Oxidation Using Langmuir Kinetics With An Effectiveness Factor, Jianhui Hong, William C. Hecker, Thomas H. Fletcher
Modeling High Pressure Char Oxidation Using Langmuir Kinetics With An Effectiveness Factor, Jianhui Hong, William C. Hecker, Thomas H. Fletcher
Faculty Publications
The global nth order rate equation has been criticized for lack of theoretical basis and has been shown to be inadequate for modeling char oxidation rates as a function of total gas pressure. The simple Langmuir rate equation is believed to have more potential for modeling high pressure char oxidation. The intrinsic Langmuir rate equation is applied to graphite flake oxidation data and agrees well with reaction rates at three temperatures over the entire range of oxygen pressure (1–64 atm). It also explains the change of reaction order with temperature. In this work, the intrinsic Langmuir rate equation is combined …
Modeling Nitrogen Evolution During Coal Pyrolysis Based On A Global Free-Radical Mechanism, Steven T. Perry, Thomas H. Fletcher
Modeling Nitrogen Evolution During Coal Pyrolysis Based On A Global Free-Radical Mechanism, Steven T. Perry, Thomas H. Fletcher
Faculty Publications
A global free-radical mechanism and an associated rate equation for the evolution of light gas nitrogen during coal devolatilization are presented. The light gas nitrogen rate equation was used to modify an existing nitrogen model so that only a network devolatilization model and coal-specific chemical structural input data are required to adequately predict light gas nitrogen release at a variety of pyrolysis conditions. Model predictions show good agreement with nitrogen release data from pyrolysis of coals of rank from lignite to low volatile bituminous at heating rates from 0.5 to 105 K/s, temperatures as high as 2300 K, and …
Improving The Accuracy Of Predicting Effectiveness Factors For Mth Order And Langmuir Rate Equations In Spherical Coordinates, Jianhui Hong, William C. Hecker, Thomas H. Fletcher
Improving The Accuracy Of Predicting Effectiveness Factors For Mth Order And Langmuir Rate Equations In Spherical Coordinates, Jianhui Hong, William C. Hecker, Thomas H. Fletcher
Faculty Publications
Char oxidation is often modeled using an mth order intrinsic reaction rate in conjunction with an effectiveness factor to account for intraparticle diffusion of gas species. This approach involves the use of a general modulus (MT) and using the first-order curve of effectiveness factor vs MT. This method was originally referred to as the general asymptotic solution. It has been suggested that a simple Langmuir rate equation is more suitable for modeling the effects of pressure on char reactivity. Therefore, several methods of developing general moduli for the Langmuir rate expression are shown. The general asymptotic …
Measurement Of Soot And Char In Pulverized Coal Fly Ash, John M. Veranth, Thomas H. Fletcher, David W. Pershing, Adel F. Sarofim
Measurement Of Soot And Char In Pulverized Coal Fly Ash, John M. Veranth, Thomas H. Fletcher, David W. Pershing, Adel F. Sarofim
Faculty Publications
The unburned carbon in the fly ash produced by low-NOx pulverized coal combustion has been shown by electron microscopy to be a mixture of porous coal char particles and aggregates of submicron particles, which are thought to be soot. The carbon is bimodally distributed with large soot aggregates mixed with the char in the particles larger than 10 microns and dispersed soot found with the submicron particles. A method for determining the mass of soot and char by liquid-suspension gravity separation was used with both laboratory-scale and power plant fly ash samples. For low-NOx, staged, pilot-scale combustion of bituminous coal …