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Structure-Based Predictive Model for Coal Char Combustion

Description: Progress was made this period on a number of separate experimental and modelling activities. At Brown, the models of carbon nanostructure evolution were expanded to consider high-rank materials with initial anisotropy. The report presents detailed results of Monte Carlo simulations with non-zero initial layer length and with statistically oriented initial states. The expanded simulations are now capable of describing the development of nanostructure during carbonization of most coals. Work next quarter will address the remaining challenge of isotropic coke-forming coals. Experiments at Brown yielded important data on the "memory loss" phenomenon in carbon annealing, and on the effect of mineral matter on high-temperature reactivity. The experimental aspects of the Brown work will be discussed in detail in the next report.
Date: April 8, 1998
Creator: Hadad, Christopher; Calo, Joseph; Essenhigh, Robert & Hurt, Robert
Partner: UNT Libraries Government Documents Department

CORROSION OF Fe-10Al-Cr ALLOYS BY COAL CHAR

Description: Corrosion of iron-base alloys at 982 C (1800 F) by coal char is observed and the phase morphologies discussed. No sulfidation was observed at 50 hours exposure. After 100 hours, internal aluminum-rich sulfides were observed along with thick outer scales of iron oxide. The species causing the high-temperature induced corrosion are probably sulfides and sulfates, present in most coal chars. Possible mechanisms for the corrosion are also discussed.
Date: October 1, 1977
Creator: Gordon, B.A. & Nagarajan, V.
Partner: UNT Libraries Government Documents Department

Real time assessment of RF cardiac tissue ablation with optical spectroscopy

Description: An optical spectroscopy approach is demonstrated allowing for critical parameters during RF ablation of cardiac tissue to be evaluated in real time. The method is based on incorporating in a typical ablation catheter transmitting and receiving fibers that terminate at the tip of the catheter. By analyzing the spectral characteristics of the NIR diffusely reflected light, information is obtained on such parameters as, catheter-tissue proximity, lesion formation, depth of penetration of the lesion, formation of char during the ablation, formation of coagulum around the ablation site, differentiation of ablated from healthy tissue, and recognition of micro-bubble formation in the tissue.
Date: March 20, 2008
Creator: Demos, S G & Sharareh, S
Partner: UNT Libraries Government Documents Department

Heterogeneous Reburning By Mixed Fuels

Description: Recent studies of heterogeneous reburning, i.e., reburning involving a coal-derived char, have elucidated its variables, kinetics and mechanisms that are valuable to the development of a highly efficient reburning process. Young lignite chars contain catalysts that not only reduce NO, but they also reduce HCN that is an important intermediate that recycles to NO in the burnout zone. Gaseous CO scavenges the surface oxides that are formed during NO reduction, regenerating the active sites on the char surface. Based on this mechanistic information, cost-effective mixed fuels containing these multiple features has been designed and tested in a simulated reburning apparatus. Remarkably high reduction of NO and HCN has been observed and it is anticipated that mixed fuel will remove 85% of NO in a three-stage reburning process.
Date: March 31, 2009
Creator: Hall, Anderson
Partner: UNT Libraries Government Documents Department

STRUCTURE-BASED PREDICTIVE MODEL FOR COAL CHAR COMBUSTION

Description: Significant progress continued to be made during the past reporting quarter on both major technical tasks. During the reporting period at OSU, computational investigations were conducted of addition vs. abstraction reactions of H, O(3 P), and OH with monocyclic aromatic hydrocarbons. The potential energy surface for more than 80 unique reactions of H, O ( 3 P), and OH with aromatic hydrocarbons were determined at the B3LYP/6-31G(d) level of theory. The calculated transition state barriers and reaction free energies indicate that the addition channel is preferred at 298K, but that the abstraction channel becomes dominant at high temperatures. The thermodynamic preference for reactivity with aromatic hydrocarbons increases in the order O(3 P) < H < OH. Abstraction from six-membered aromatic rings is more facile than abstraction from five-membered aromatic rings. However, addition to five-membered rings is thermodynamically more favorable than addition to six-membered rings. The free energies for the abstraction and addition reactions of H, O, and OH with aromatic hydrocarbons and the characteristics of the respective transition states can be used to calculate the reaction rate constants for these important combustion reactions. Experimental work at Brown University on the effect of reaction on the structural evolution of different chars (i.e., phenolic resin char and chars produced from three different coals) have been investigated in a TGA/TPD-MS system. It has been found that samples of different age of these chars appeared to lose their "memory" concerning their initial structures at high burn-offs. During the reporting period, thermal desorption experiments of selected samples were conducted. These spectra show that the population of low temperature oxygen surface complexes, which are primarily responsible for reactivity, are more similar for the high burn-off than for the low burn-off samples of different ages; i.e., the population of active sites are more similar for the �younger� ...
Date: January 13, 1999
Creator: HADAD, CHRISTOPHER M.; CALO, JOSEPH M.; ESSENHIGH, ROBERT H. & HURT, ROBERT H.
Partner: UNT Libraries Government Documents Department

STRUCTURE BASED PREDICTIVE MODEL FOR COAL CHAR COMBUSTION

Description: This report is part on the ongoing effort at Brown University and Ohio State University to develop structure based models of coal combustion. A very fundamental approach is taken to the description of coal chars and their reaction processes, and the results are therefore expected to have broad applicability to the spectrum of carbon materials of interest in energy technologies. This quarter, the project was in a period no-cost extension and discussions were held about the end phase of the project and possible continuations. The technical tasks were essentially dormant this period, but presentations of results were made, and plans were formulated for renewed activity in the fiscal year 2001.
Date: June 15, 2001
Creator: Hurt, Robert; Calo, Joseph; Essenhigh, Robert & Hadad, Christopher
Partner: UNT Libraries Government Documents Department

STRUCTURE-BASED PREDICTIVE MODEL FOR COAL CHAR COMBUSTION

Description: During the past quarter of this project, significant progress continued was made on both major technical tasks. Progress was made at OSU on advancing the application of computational chemistry to oxidative attack on model polyaromatic hydrocarbons (PAHs) and graphitic structures. This work is directed at the application of quantitative ab initio molecular orbital theory to address the decomposition products and mechanisms of coal char reactivity. Previously, it was shown that the �hybrid� B3LYP method can be used to provide quantitative information concerning the stability of the corresponding radicals that arise by hydrogen atom abstraction from monocyclic aromatic rings. In the most recent quarter, these approaches have been extended to larger carbocyclic ring systems, such as coronene, in order to compare the properties of a large carbonaceous PAH to that of the smaller, monocyclic aromatic systems. It was concluded that, at least for bond dissociation energy considerations, the properties of the large PAHs can be modeled reasonably well by smaller systems. In addition to the preceding work, investigations were initiated on the interaction of selected radicals in the �radical pool� with the different types of aromatic structures. In particular, the different pathways for addition vs. abstraction to benzene and furan by H and OH radicals were examined. Thus far, the addition channel appears to be significantly favored over abstraction on both kinetic and thermochemical grounds. Experimental work at Brown University in support of the development of predictive structural models of coal char combustion was focused on elucidating the role of coal mineral matter impurities on reactivity. An �inverse� approach was used where a carbon material was doped with coal mineral matter. The carbon material was derived from a high carbon content fly ash (Fly Ash 23 from the Salem Basin Power Plant. The ash was obtained from Pittsburgh #8 coal (PSOC ...
Date: June 4, 1998
Creator: HADAD, CHRISTOPHER M.; CALO, JOSEPH M.; ESSENHIGH, ROBERT H. & HURT, ROBERT H.
Partner: UNT Libraries Government Documents Department

STRUCTURE-BASED PREDICTIVE MODEL FOR COAL CHAR COMBUSTION

Description: Progress was made this period on a number of tasks. A significant advance was made in the incorporation of macrostructural ideas into high temperature combustion models. Work at OSU by R. Essenhigh in collaboration with the University of Stuttgart has led to a theory that the zone I / II transition in char combustion lies within the range of conditions of interest for pulverized char combustion. The group has presented evidence that some combustion data, previously interpreted with zone II models, in fact takes place in the transition from zone II to zone 1. This idea was used at Brown to make modifications to the CBK model (a char kinetics package specially designed for carbon burnout prediction, currently used by a number of research and furnace modeling groups in academia and industry). The resulting new model version, CBK8, shows improved ability to predict extinction behavior in the late stages of combustion, especially for particles with low ash content. The full development and release of CBK8, along with detailed descriptions of the role of the zone 1/2 transition will be reported on in subsequent reports. ABB-CE is currently implementing CBK7 into a special version of the CFD code Fluent for use in the modeling and design of their boilers. They have been appraised of the development, and have expressed interest in incorporating the new feature, realizing full CBK8 capabilities into their combustion codes. The computational chemistry task at OSU continued to study oxidative pathways for PAH, with emphasis this period on heteroatom containing ring compounds. Preliminary XPS studies were also carried out. Combustion experiments were also carried out at OSU this period, leading to the acquisition of samples at various residence times and the measurement of their oxidation reactivity by nonisothermal TGA techniques. Several members of the project team attended the ...
Date: September 11, 1998
Creator: HADAD, CHRISTOPHER M.; CALO, JOSEPH M.; ESSENHIGH, ROBERT H. & HURT, ROBERT H.
Partner: UNT Libraries Government Documents Department

Char Crystalline Transformations During Coal Combustion and Their Implication for Carbon Burnout

Description: Recent work at Sandia National Laboratories, Imperial College, and the U.K. utility PowerGen, has identified an important mechanism believed to have a large influence on unburned carbon levels from pulverized coal fired boilers. That mechanism is char carbon crystalline rearrangements on subsecond times scales at temperatures of 1800 - 2500 K, which lead to char deactivation in the flame zones of furnaces. The so-called thermal annealing of carbons is a well known phenomenon, but its key role in carbon burnout has only recently been appreciated, and there is a lack of quantitative data in this time/temperature range. In addition, a new fundamental tool has recently become available to study crystalline transformations, namely high resolution transmission electron microscopy (HRTEM) fringe imaging, which provides a wealth of information on the nature and degree of crystallinity in carbon materials such as coal chars. Motivated by these new developments, this University Coal Research project has been initiated with the following two goals:  to determine transient, high-temperature, thermal deactivation kinetics as a function of parent coal and temperature history.  to characterize the effect of this thermal treatment on carbon crystalline structure through high-resolution transmission electron microscopy and specialized, quantitative image analysis. Work is currently underway on the following three tasks: Task 1 Experimental technique development. The goal of this task is to develop and demonstrate an apparatus and procedure for measuring transient, high-temperature, thermal deactivation of coal chars. While peak gas temperatures in boilers are often in the range 1800 - 2000 K, peak particle temperatures can be much higher due to high rates of heat release at the particle surface due to exothermic carbon oxidation. The prototype transient heat treatment apparatus is based on an inert-gas purged graphite-rod sample holder that is subjected to rapid Joule heating to temperatures approaching 3000 o ...
Date: December 30, 1997
Creator: Hurt, Robert H.
Partner: UNT Libraries Government Documents Department

Engineering Development of Coal-Fired High-Performance Power Systems

Description: The concept uses a pyrolyzation process to convert coal into fuel gas and char. The char is fired in a High Temperature Advanced Furnace (HITAF). It is a pulverized fuel- fired boiler/ air heater where steam and gas turbine air are indirectly heated. The fuel gas generated in the pyrolyzer is then used to heat the gas turbine air further before it enters the gas turbine. The project is currently in Phase 2 which includes engineering analysis, laboratory testing and pilot plant testing. Research and development is being done on the HIPPS systems that are not commercial or being developed on other projects. Pilot plant testing of the pyrolyzer subsystem and the char combustion subsystem are being done separately, and then a pilot plant with a more integrated HIPPS arrangement will be tested. The High Performance Power System is a coal- fired, combined cycle power generating system that will have an efficiency of greater than 47 percent (HHV) with NOx and SOx less than 0.025 Kg/ GJ (0.06 lb/ MMBtu). This performance is achieved by combining a coal pyrolyzation process with a High Temperature Advanced Furnace (HITAF). The pyrolyzation process consists of a pressurized fluidized bed reactor which is operated at about 926 o C (1700 o F) at substoichiometric conditions. This process converts the coal into a low- Btu fuel gas and char. These products are then separated. The char is fired in the HITAF where heat is transferred to the gas turbine compressed air and to the steam cycle. The HITAF is fired at atmospheric pressure with pulverized fuel burners. The combustion air is from the gas turbine exhaust stream. The fuel gas from the pyrolyzation process is fired in a Multi- Annular Swirl Burner (MASB) where it further heats the gas turbine air leaving the HITAF. This ...
Date: December 15, 1997
Creator: Shenker, J.
Partner: UNT Libraries Government Documents Department

Treatment of Mixed Wastes via Fixed Bed Gasification

Description: This report outlines the details of research performed under USDOE Cooperative Agreement DE-FC21-96MC33258 to evaluate the ChemChar hazardous waste system for the destruction of mixed wastes, defined as those that contain both RCRA-regulated haz- ardous constituents and radionuclides. The ChemChar gasification system uses a granular carbonaceous char matrix to immobilize wastes and feed them into the gasifier. In the gasifier wastes are subjected to high temperature reducing conditions, which destroy the organic constituents and immobilize radionuclides on the regenerated char. Only about 10 percent of the char is consumed on each pass through the gasifier, and the regenerated char can be used to treat additional wastes. When tested on a 4-inch diameter scale with a continuous feed unit as part of this research, the ChemChar gasification system was found to be effective in destroying RCRA surrogate organic wastes (chlorobenzene, dichloroben- zene, and napht.halene) while retaining on the char RCRA heavy metals (chromium, nickel, lead, and cadmium) as well as a fission product surrogate (cesium) and a plutonium surrogate (cerium). No generation of harmful byproducts was observed. This report describes the design and testing of the ChemChar gasification system and gives the operating procedures to be followed in using the system safely and effectively for mixed waste treatment.
Date: October 28, 1998
Partner: UNT Libraries Government Documents Department

HETEROGENEOUS REBURNING BY MIXED FUELS

Description: Recent studies of heterogeneous reburning, i.e., reburning involving a coal-derived char, have elucidated its variables, kinetics and mechanisms that are valuable to the development of a highly efficient reburning process. Young lignite chars contain catalysts that not only reduce NO, but they also reduce HCN that is an important intermediate that recycles to NO in the burnout zone. Gaseous CO scavenges the surface oxides that are formed during NO reduction, regenerating the active sites on the char surface. Based on this mechanistic information, cost-effective mixed fuels containing these multiple features has been designed and tested in a simulated reburning apparatus. Remarkably high reduction of NO and HCN has been observed and it is anticipated that mixed fuel will remove 85% of NO in a three-stage reburning process.
Date: January 14, 2005
Creator: Chen, Wei-Yin & Gathitu, Benson B.
Partner: UNT Libraries Government Documents Department

COAL AND COAL CONSTITUENT STUDIES BY ADVANCED EMR TECHNIQUES

Description: Advanced electronic magnetic resonance (EMR) methods are used to examine properties of coals, chars, and molecular species related to constituents of coal. During this grant period, progress was made on setting up a separate high frequency EMR system particularly appropriate for such studies and exploring the use of low-frequency dynamic nuclear polarization (DNP) to examine the interaction between fluids such as water and the surface of suspended char particles.
Date: March 28, 1997
Creator: Belford, R. Linn & Clarkson, Robert B.
Partner: UNT Libraries Government Documents Department

HIGH PRESSURE COAL COMBUSTION KINETICS PROJECT

Description: NEA completed the CFD simulations for all NBFZ tests. SRI resumed work on HPBO experiments and conducted preliminary tests using the UCONN impactor. UCONN prepared several samples of char for cross-sectional analysis by SEM and characterization is underway. BU completed the NBFZ char characterization program. CBK model had been implemented into Fluent.
Date: July 25, 2003
Creator: Orsino, Stefano
Partner: UNT Libraries Government Documents Department

In Situ Causticizing for Black Liquor Gasification

Description: Black liquor gasification offers a number of attractive incentives to replace Tomlinson boilers but it also leads to an increase in the causticizing load. Reasons for this have been described in previous reports (FY04 ERC, et.al.). The chemistries have also been covered but will be reviewed here briefly. Experimental results of the causticizing reactions with black liquor are presented here. Results of the modeling work were presented in detail in the Phase 1 report. They are included in Table 2 for comparison but will not be discussed in detail. The causticizing agents were added to black liquor in the ratios shown in Table 1, mixed, and then spray-dried. The mixture ratios (doping levels) reflect amount calculated from the stoichiometry above to achieve specified conversions shown in the table. The solids were sieved to 63-90 microns for use in the entrained flow reactors. The firing conditions are shown in Table 2. Pictures and descriptions of the reactors can be found in the Phase 1 annual report. Following gasification, the solids (char) was collected and analyzed by coulometric titration (for carbonate and total carbon), and by inductively coupled plasma emission spectroscopy (ICP) for a wide array of metals.
Date: October 1, 2005
Creator: Sinquefield, Scott Alan
Partner: UNT Libraries Government Documents Department

The role of pore structure on char reactivity. Quarterly progress report, October 1994--December 1994

Description: In order to examine the role of pore structure, studies will be conducted on coal chars in the electrodynamic balance. Larger particles will also be examined using a fluidized bed to examine diffusion control reactions, and soot will also be investigated to examine the role of meso- and micro-pores without macro-pore interference. These studies will allow a full range of particles sizes and temperatures to be investigated and eventually modeled.
Date: January 1, 1995
Creator: Sarofim, A. F.
Partner: UNT Libraries Government Documents Department

Simulation of coal gasification in a fluidized bed

Description: In this analysis of coal gasification, a fundamental approach is used where a set of multiphase (Eulerian) fluid dynamic equations, obtained either by a suitable averaging technique (Anderson and Jackson, 1976; Drew, 1971) or the formulations of continuum mechanics (Drew, 1983), is used to describe the conservation of mass, momentum, and energy for three interpenetrating phases. The particles, like the fluidizing gas, are described as interpenetrating continua. Different particle types are treated as distinct phases; in this study, the feed coal and the bed char are represented as separate phases in order to account for their different histories. Constitutive laws account for the exchange of momentum between phases (``drag``) and interphase energy transfer. The stresses within the granular phases are determined by a formulation based on the kinetic theory, characterized by a ``granular temperature``. A computer code, based on this multiphase hydrodynamic model, has been developed at the Morgantown Energy Technology Center for the detailed simulation of gas and particle dynamics in heavily loaded coal conversion processes (Syamlal, Rogers, O`Brien, 1994; Syamlal, 1995). The hydrodynamic simulation showed the reactor operated in a jetting/bubbling mode. A gas jet penetrated a considerable distance into the bed, and then detached as ``bubbles`` which rose to the top of the column. The reaction scheme indicated that the feed coal did not begin to devolatilize until it had traversed this region, because of the time required to heat up. Thus, volatiles were not released in the jetting region of the bed, but higher in the bed. The oxygen fed with the coal, however, reacted immediately with the recirculating hot char. The net effect of the char reaction scheme was to created. CO, which burned in the region where.the jet detached, creating a, fairly stable ``flame``. The tar reaction scheme indicated that none of the tar ...
Date: December 31, 1996
Creator: O`Brien, T.J.
Partner: UNT Libraries Government Documents Department

Kinetics and Mechanisms of NO(x) - Char Reduction.

Description: Most industrially important carbons are produced from naturally occurring materials such as coal, oil, peat or wood by some form of thermal process. Chars are obtained from those natural materials as a residue after removal of the volatile matter. Chars (prepared from coal or other organic precursors) are non-graphitizable carbons, meaning that they cannot be transformed into graphitic carbon. Chars are comprised of elementary crystallites in parallel layers which are randomly oriented with respect to each other and are crosslinked together through weak bonds. Voids between crystallites determine the porosity of the char, and this plays an important role in char gasification behavior. Chars usually contain a pore size distribution, in which the larger macro- and mesopores play an important role in transport of reactants into the much smaller micropores, in which most gasification and combustion take place. Therefore, the effectiveness of micropores in gasification depends heavily on the numbers of meso- and macropores.
Date: December 31, 1997
Creator: Suurerg, E.M.; Lilly, W.D. & Aarna, I.
Partner: UNT Libraries Government Documents Department

Development of an advanced, continuous mile gasification process for the production of co-products. Quaterly report, April 1, 1996--June 30, 1996

Description: Two 20-ton CTC formed coke production runs were completed. The product from the first run tested at a General Motors` production cupola at a 12.5 percent of total coke charge level successfully. The second 20 tons of CTC formed coke will be evaluated in early August at a General Motors` research facility at Marquette, Michigan, using a 100 percent CTC formed coke charge. Design of a commercial plant continued with emphasis given to the calcining and briquetting operations.
Date: April 1, 1998
Creator: O`Neal, G.W.
Partner: UNT Libraries Government Documents Department

Rate inhibition of steam gasification of adsorbed hydrogen. Technical progress report, October 1, 1994--December 31, 1994

Description: Work during the fifth quarter of the grant period has involved both gasification experiments in steam and hydrogen and continued development of the reaction apparatus and analytical methods. Most of the latter work has focused on mass spectrometric analysis of the effluent gases to obtain better response factors and to reduce background signals resulting from impurities in the reacting gas stream.
Date: April 1, 1995
Creator: Miller, D.J.
Partner: UNT Libraries Government Documents Department

Structure-Based Predictive model for Coal Char Combustion.

Description: The first quarter of this project was used to carry out a detailed planning process to coordinate the various aspects of this collaborative effort. A workshop was held at Brown University on December 4, 1996, attended by all project participants and key visitors, in which presentations were given by the principal investigators on their respective subtasks. The planning process culminated in the completion of a comprehensive document submitted to DOE / FETC under separate cover. Following the planning exercise, research work was initiated and will be continued in the second project quarter.
Date: March 28, 1997
Creator: Hurt, R.; Calo, J.; Essenhigh, R.; Hadad, C & Stanley, E.
Partner: UNT Libraries Government Documents Department

Optimized Fuel Injector Design for Maximum In-Furnace N0x Reduction and Minimum Unburned Carbon

Description: Coal burners/injectors are an integral part of PC-fired facilities and their design plays a crucial role in many of the most cost-effective NO{sub x} control strategies (staged low NO{sub x} burners, reburning, or hybrid approaches such as reburning and SNCR). The effort described in this presentation/paper involves two of these techniques, low NO{sub x} burners and reburning, and focuses on the role of the solids, in particular, the impact of heterogeneous chemistry and two-phase mixing on NO{sub x} formation/reduction and carbon conversion. The inter-related roles of fluid mechanics and char reactivity have been evaluated experimentally and computationally in an effort to understand their effects on NO{sub x} formation/destruction and carbon burnout. Experiments will be discussed that describe chemistry and mixing phenomena relevant to both coal-fired burners and reburning. In addition, simulations focusing on similar issues in a still-scale boiler environment have been performed using simple and advanced models of char oxidation developed during the course of the program. These results provide insight into the importance of heterogeneous NO{sub x} formation/reduction mechanisms and the importance of the interaction between char reactivity and the temperature/oxygen-concentration history of coal particles. In addition, burner and particle size specific sources of carbon-in-ash can be identified.
Date: July 1, 1997
Creator: Harding, S.; Davis, K. & Valentine, J.
Partner: UNT Libraries Government Documents Department

Char particle fragmentation and its effect on unburned carbon during pulverized coal combustion. Final report, March 20, 1997

Description: This document is the final report of work on a project concerned with the fragmentation of char particles during pulverized coal combustion that was conducted at the High Temperature Gasdynamics Laboratory at Stanford University, Stanford, California. The project is intended to satisfy, in part, PETC`s research efforts to understand the chemical and physical processes that govern coal combustion. The overall objectives of the project were: (1) to characterize the fragmentation events as a function of combustion environment, (2) to characterize fragmentation with respect to particle porosity and mineral loadings, (3) to assess overall mass loss rates with respect to particle fragmentation, and (4) to quantify the impact of fragmentation on unburned carbon in ash. The knowledge obtained during the course of this project can be used to predict accurately the overall mass loss rates of coals based on both the physical and chemical characteristics of their chars. The work provides a means of assessing reasons for unburned carbon in the ash of coal fired boilers and furnaces.
Date: December 31, 1997
Creator: Mitchell, R.E.
Partner: UNT Libraries Government Documents Department

Structural evolution of carbon during oxidation. Final report

Description: The examination of the structural evolution of carbon during oxidation has proven to be of scientific interest. Early modeling work of fluidized bed combustion showed that most of the reactions of interest occurs in the micropores, and this work has concentrated on these pores. This work has concentrated on evolution of macroporosity and microporosity of carbons during kinetic controlled oxidation using SAXS, CO{sub 2} and TEM analysis. Simple studies of fluidized bed combustion of coal chars has shown that many of the events considered fragmentation events previously may in fact be {open_quotes}hidden{close_quotes} or nonaccessible porosity. This makes the study of the microporous combustion characteristics of carbon even more important. The generation of a combustion resistant grid, coupled with measurements of the SAXS and CO{sub 2} surface areas, fractal analysis and TEM. Studies has confirmed that soot particles shrink during their oxidation, as previously suspected. However, this shrinkage results in an overall change in structure. This structure becomes, on a radial basis, much more ordered near the edges, while the center itself becomes transparent to the TEM beam, implying a total lack of structure in this region. Although complex, this carbon structure is probably burning as to keep the density of the soot particles nearly the same. The TEM techniques developed for examination of soots has also been applied to Spherocarb. The Spherocarb during oxidation also increases its ordering. This ordering, by present theories, would imply that the reactivity would go. However, the reactivity goes up, implying that structure of carbon is secondary in importance to catalytic effects.
Date: April 1, 1998
Creator: Sarofim, A.F.
Partner: UNT Libraries Government Documents Department