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Heterogeneous kinetics of coal gasification. Quarterly technical progress report, 1 May 1982-31 July 1982. [Equipment design]

Description: During the reporting period significant progress was made on two fronts: (1) the steam addition system for transient steam-char kinetic experiments; and (2) the automated data acquisition system for rapid mass programming (control) of the mass spectrometer and data logging. Steam Addition System: Although it is a relatively straightforward matter to produce steam for the reactor, we found that it is quite a challenge to develop a system capable of maintaining a steady and accurately-known flow rate of steam-argon mixtures at high pressure and temperature in alternate flow circuits (i.e., the reactor and purge lines), while simultaneously protecting downstream valving and instrumentation. Thus, the scheme originally proposed has been modified to eliminate potential operating problems associated with the preliminary design. Automated Data Acquisition System: Although the CO/sub 2/ gasification data were obtained manually, the ultimate objective of the project to develop a quantitative understanding of the complete gasification rate process in the complex synthesis gas milieux calls for automated programming (control) of the mass spectrometer. In addition, the current mass spectrometer signal processing technique requires the use of a lock-in amplifier to extract the modulated portion of the total signal due to the beam species only, in an analog mode. In order to allow fast scanning of a number of species, the characteristic dwell time required by the lock-in amplifier on a particular mass peak must be decreased. These requirements are being met by implementing automated mass programming and data collection, and direct digital, phase-sensitive pulse counting.
Date: August 1, 1982
Creator: Calo, J.M.
Partner: UNT Libraries Government Documents Department

SPOUTED BED ELECTRODES (SBE) FOR DIRECT UTILIZATION OF CARBON IN FUEL CELLS

Description: This Phase I project was focused on an investigation of spouted bed particulate electrodes for the direct utilization of solid carbon in fuel cells. This approach involves the use of a circulating carbon particle/molten carbonate slurry in the cell that provides a few critical functions: it (1) fuels the cell continuously with entrained carbon particles; (2) brings particles to the anode surfaces hydrodynamically; (3) removes ash from the anode surfaces and the cell hydrodynamically; (4) provides a facile means of cell temperature control due to its large thermal capacitance; (5) provides for electrolyte maintenance and control in the electrode separator(s); and (6) can (potentially) improve carbon conversion rates by ''pre-activating'' carbon particle surfaces via formation of intermediate oxygen surface complexes in the bulk molten carbonate. The approach of this scoping project was twofold: (1) adaptation and application of a CFD code, originally developed to simulate particle circulation in spouted bed electrolytic reactors, to carbon particle circulation in DCFC systems; and (2) experimental investigation of the hydrodynamics of carbon slurry circulation in DCFC systems using simulated slurry mixtures. The CFD model results demonstrated that slurry recirculation can be used to hydrodynamically feed carbon particles to anode surfaces. Variations of internal configurations were investigated in order to explore effects on contacting. It was shown that good contacting with inclined surfaces could be achieved even when the particles are of the same density as the molten carbonate. The use of CO{sub 2} product gas from the fuel cell as a ''lift-gas'' to circulate the slurry was also investigated with the model. The results showed that this is an effective method of slurry circulation; it entrains carbon particles more effectively in the draft duct and produces a somewhat slower recirculation rate, and thus higher residence times on anode surfaces, and can be controlled completely ...
Date: December 1, 2004
Creator: Calo, J.M.
Partner: UNT Libraries Government Documents Department

COAL CLEANING VIA LIQUID-FLUIDIZED CLASSIFICAITON (LFBC) WITH SELECTIVE SOLVENT SWELLING

Description: The concept of coal beneficiation due to particle segregation in water-fluidized beds, and its improvement via selective solvent-swelling of organic material-rich coal particles, was investigated in this study. Particle size distributions and their behavior were determined using image analysis techniques, and beneficiation effects were explored via measurements of the ash content of segregated particle samples collected from different height locations in a 5 cm diameter liquid-fluidized bed column (LFBC). Both acetone and phenol were found to be effective swelling agents for both Kentucky No.9 and Illinois No.6 coals, considerably increasing mean particle diameters, and shifting particle size distributions to larger sizes. Acetone was a somewhat more effective swelling solvent than phenol. The use of phenol was investigated, however, to demonstrate that low cost, waste solvents can be effective as well. For unswollen coal particles, the trend of increasing particle size from top to bottom in the LFBC was observed in all cases. Since the organic matter in the coal tends to concentrate in the smaller particles, the larger particles are typically denser. Consequently, the LFBC naturally tends to separate coal particles according to mineral matter content, both due to density and size. The data for small (40-100 {micro}m), solvent-swollen particles clearly showed improved beneficiation with respect to segregation in the water-fluidized bed than was achieved with the corresponding unswollen particles. This size range is quite similar to that used in pulverized coal combustion. The original process concept was amply demonstrated in this project. Additional work remains to be done, however, in order to develop this concept into a full-scale process.
Date: December 1, 2000
Creator: Calo, J. M.
Partner: UNT Libraries Government Documents Department

Heterogeneous kinetics of coal gasification. Technical progress report, 1 August 1981-31 January 1982

Description: The continuing development of an experimental apparatus for the study of the heterogeneous reactions of coal-char gasifiction under conditions of industrial significance is described. The apparatus consists of: (1) a continuous gas flow, fixed solids gradientless reactor; (2) an automatic gas addition system for generating concentration perturbations in the reactor feed stream under conditions of constant flow rate, temperature, and pressure; and (3) a supersonic, modulated molecular beam mass spectrometer sampling system to monitor and resolve the transient response of the gas phase composition at the reactor exit. Work was concentrated on experimental runs of the transient behavior of the char-CO/sub 2/ reaction system. In addition, reactor mixing performance and estimates of possible interphase heat and mass transfer limitations on the kinetic rates were also determined. Modifications, testing and calibration of the beam sampling system and the mass spectrometer were also performed. Computer codes were written to simulate the transient response of the reaction system under varying experimental conditions for different mechanisms found in the literature. These codes are primarily used for model discrimination. An optimization code based on the Marquardt technique was also written for model parameter estimation from the data.
Date: February 1, 1982
Creator: Sy, O. & Calo, J.M.
Partner: UNT Libraries Government Documents Department

Characterization of porosity via secondary reactor

Description: In this quarterly technical Progress report, we summarize the progress which has been achieved with the development of the small angle scattering capability to be used in the current project. In particular, the following was accomplished during the reporting period. The parameter estimation code, MARQFIT, has been tested and is fully operational. The code has been applied to small angle neutron scattering (SANS) data on coals swollen with deuterated solvents. Application of the FPPS model to these data indicated that the large sphere distribution apparently requires a mean greater than 1000[Angstrom]. This was attributed to the influence of interparticle voids. Specific surface areas were also estimated for these coals. Application of this model to the coal chars used in the current project will not be subject to the same effects.
Date: January 1, 1992
Creator: Calo, J.M.
Partner: UNT Libraries Government Documents Department

Characterization of porosity via secondary reactions

Description: The new TPD-MS/TGA system has been constructed and successfully tested. This system is constructed around a new Cahn D-200 digital recording microbalance, which was purchased for this purpose. The TPD reactor is the hangdown'' tube for the microbalance. The system can operate at pressures from vacuum to atmospheric. Control and data logging of this new experimental system are performed using a Macintosh II microcomputer with a GW Instruments 625 Jr. interface. All the control software has been written and tested. A new furnace with low thermal capacitance'' was constructed for this system which allows linear heating rates to 1100{degree}C at rates as high as 20OK/min. This system will become a principal apparatus for obtaining some of the data required for the development of porosity characterization techniques via TPD. Software has been written for the analysis of small angle scattering (SAS) data, obtained with either X-rays (SAXS) or neutrons (SANS), which will be used in addition to gas adsorption techniques to characterize porosity for comparison with secondary reaction data.
Date: January 1, 1992
Creator: Calo, J.M.
Partner: UNT Libraries Government Documents Department

Characterization of porosity via secondary reactions

Description: During the course of recent work applying temperature programmed desorption (TPD) to the determination of energetic distributions of oxygen complexes on the surfaces of oxidized coal chars, we discovered that secondary interactions occurring within the char structure during TPD produce characteristic features in the resultant spectra that appear to be quite sensitive to char porosity. The relative and absolute extents of these secondary interactions from the basis of a potential characterization technique. The use of such a method to characterize coal char porosity is potentially attractive because the requisite spectra can be obtained in a single TPD experiment -- a very facile experimental procedure. However, the unambiguous and quantitative interpretation of such data in terms of parameters that can be used to characterize coal char porosity still requires development and an improved understanding of the controlling phenomena. These issues define the primary focus of the current proposal.
Date: January 1, 1991
Creator: Calo, J.M. & Lilly, W.D.
Partner: UNT Libraries Government Documents Department

Development of High Activity, Coal-Derived, Promoted Catalytic Systems for NOx Reduction at Low Temperatures

Description: This project is directed at an investigation of catalytic NO{sub x} reduction mechanisms on coal-derived, activated carbon supports at low temperatures. Promoted carbon systems offer some potentially significant advantages for heterogeneous NO{sub x} reduction. These include: low cost; high activity at low temperatures, which minimizes carbon loss; oxygen resistance; and a support material which can be engineered with respect to porosity, transport and catalyst dispersion characteristics.
Date: May 1, 1998
Creator: Calo, J. M.
Partner: UNT Libraries Government Documents Department

Characterizadtion of porosity via secondary reactions. Quarterly technical progress report, 1 July 1994--30 September 1994

Description: The following was accomplished during the reporting period: Comparisons between porosity characterization data obtained from nitrogen adsorption isotherms, and that revealed by CO and CO{sub 2} temperature programmed desorption (TPD) spectra were performed for Pittsburgh {number_sign}8 coal char samples prepared at various degrees of burn-off, ranging from 0--72% burn-off, in 0.1 MPa oxygen at 470{degrees}C. Conclusions derived from these analyses include: The CO TPD spectra correlate the development of the microporosity; and the CO{sub 2} spectra correlate the development of the larger, external porosity. This behavior is the same as we have observed for Wyodak coal char. This behavior is currently attributed to the restriction of formation of the larger C0{sub 2}-liberating oxygen surface complexes (e.g., lactones, carboxylic acid anhydrides) to the larger, external porosity, while the smaller CO{sub 2}-liberating complexes (e.g., carbonyls, semi-quinones) form on the surfaces of all they porosity, but since the microporosity accounts for the bulk of the surface area, the latter correlates the microporosity quite well. Together with the Wyodak coal char results, these data represent the first time that this particular connection has been made between porosity development and TPD spectra.
Date: December 31, 1994
Creator: Calo, J.M. & Zhang, L.
Partner: UNT Libraries Government Documents Department

Characterization of porosity via secondary reactions: Quarterly technical progress report, 1 October 1994--31 December 1994

Description: Specific surface area, as well as its accessibility to gaseous reactants, are of paramount importance for all heterogeneous interactions occurring at coal char surfaces. Accessibility of this surface area is governed by the pore structure morphology of the char; i.e., pore size distribution, tortuosity, intersections, shape, etc. The porosity morphology of coal chars varies over a considerable range and is determined by a large number of factors including the nature of the porosity of the precursor material prior to carbonization, the carbonization process, and extent and method of any subsequent activation or gasification. A persistent problem in this area has been the reliable, quantitative measurement and characterization of the resultant porosity, especially the micropores. The following was accomplished during the reporting period: use of the random pore model as a method of rationalizing the data obtained from CO and CO{sub 2} TPD spectra has been initiated; and {alpha}-plot data obtained for Wyodak coal char samples prepared at various degrees of burn-off, ranging from 0--75% burn-off, in 0.1 MPa oxygen at 470 C, were used to compare with random pore model predictions. Conclusions derived from this analysis include: the random pore model predictions are consistent with the evolution of sample surface area and porosity with burn-off as determined for the Wyodak coal char samples; and the parameters obtained from the random pore model provide a reasonably good comparison with the {alpha}-plot data.
Date: May 1, 1995
Creator: Calo, J.M. & Zhang, L.
Partner: UNT Libraries Government Documents Department

High pressure/high temperature thermogravimetric apparatus. Final report

Description: The purpose of this instrumentation grant was to acquire a state-of-the-art, high pressure, high temperature thermogravimetric apparatus (HP/HT TGA) system for the study of the interactions between gases and carbonaceous solids for the purpose of solving problems related to coal utilization and applications of carbon materials. The instrument that we identified for this purpose was manufactured by DMT (Deutsche Montan Technologies)--Institute of Cokemaking and Coal Chemistry of Essen, Germany. Particular features of note include: Two reactors: a standard TGA reactor, capable of 1100 C at 100 bar; and a high temperature (HT) reactor, capable of operation at 1600 C and 100 bar; A steam generator capable of generating steam to 100 bar; Flow controllers and gas mixing system for up to three reaction gases, plus a separate circuit for steam, and another for purge gas; and An automated software system for data acquisition and control. The HP/TP DMT-TGA apparatus was purchased in 1996 and installed and commissioned during the summer of 1996. The apparatus was located in Room 128 of the Prince Engineering Building at Brown University. A hydrogen alarm and vent system were added for safety considerations. The system has been interfaced to an Ametek quadruple mass spectrometer (MA 100), pumped by a Varian V250 turbomolecular pump, as provided for in the original proposed. With this capability, a number of gas phase species of interest can be monitored in a near-simultaneous fashion. The MS can be used in a few different modes. During high pressure, steady-state gasification experiments, it is used to sample, measure, and monitor the reactant/product gases. It can also be used to monitor gas phase species during nonisothermal temperature programmed reaction (TPR) or temperature programmed desorption (TPD) experiments.
Date: December 1, 1999
Creator: Calo, J.M. & Suuberg, E.M.
Partner: UNT Libraries Government Documents Department

Characterization of porosity via secondary reactions. Quarterly technical progress report, 1 July 1995--1 October 1995

Description: The following was accomplished during the reporting period: The random pore model was extended to correlate the development of microporosity in resin and Wyodak coal char. Conclusions derived from this analysis include: the random pore model can be extended to microporosity development for chars which are initially (i.e., at zero burn-off) microporous, assuming a normal micropore volume distribution. The resultant mean pore radius and variance prior to oxidation were, respectively, 1.04 nm and 0.24 nm for Wyodak coal char, and 0.64 nm and 0.18 nm for resin char. Consequently, the pore size is larger, and the pore distribution is broader for Wyodak coal char than for resin char prior to activation. The rate of mean micropore radius decrease with burn-off at high conversion is slower for resin char than for Wyodak coal char. This result suggests that the percentage of micropores converted to larger pores is smaller for resin char than for Wyodak coal char; i.e., resin char remains more microporous with burn-off. The nonmicroporous surface area was estimated by difference from the total surface area as determined from nitrogen adsorption data. These values correlate reasonably well with nonmicroporous surface areas determined from the {alpha}{sub s}-plot method.
Date: December 31, 1995
Creator: Calo, J.M. & Zhang, L.
Partner: UNT Libraries Government Documents Department

Active sites in char gasification. First quarterly progress report, September 1983-December 1983

Description: This report reviews the background and motivation for this work, and discusses some initial scoping studies on chars similar to the model compounds to be used in later phases of the work. Some preliminary synthetic methodologies for model compounds are presented. 69 references.
Date: January 1, 1983
Creator: Suuberg, E. M.; Calo, J. M.; Wojtowicz, M. & Lilly, W.
Partner: UNT Libraries Government Documents Department

NO sub x -char reactions: Kinetics and transport aspects

Description: The present project is motivated by the need to reduce NO{sub x} emissions from combustors, especially coal combustors. Reactions with carbon are known to be effective at reducing No to N{sub 2}, and remain interesting candidates in a wide variety of possible applications. These reactions are known to be important in reducing NO{sub x} emissions from fluidized bed coal combustors, in which the coal char itself serves as the reducing agent. The principal goal of this project is to develop a mechanistic understanding of the processes by which carbons reduce NO to N{sub 2}. The carbon was a char derived from phenol-formaldehyde resin. This material has been noted to be a reasonable model for coal chars in most respects, expect that its gasification behavior is not complicated by catalytic processes due to minerals. In the first phases of the project, the global kinetics of the process were established. In more recent work, attention has been turned to the individual steps in the mechanism. Recent quarterly reports have detailed the role of both chemisorption and desorption processes in determining the course and kinetics of the process. This report continues the reporting of results obtained along these lines, and draws an important new conclusion concerning the number of separate processes involved in determining the kinetics. 40 refs., 3 figs., 2 tabs.
Date: January 1, 1990
Creator: Calo, J.M. & Suuberg, E.M.
Partner: UNT Libraries Government Documents Department

Active sites in char gasification. Quarterly technical progress report, 1 January 1984-31 March 1984. [Polymers of phenol-formaldehyde family; chars produced from model compounds]

Description: This project is concerned with the study of the nature and behavior of active sites in gasification of chars produced from synthesized model compounds, primarily of the phenol-formaldehyde family of resins. The current technical progress report presents further developments on resin synthesis and characterization and the design of a pyro-gasifier reactor for transient kinetic studies of the chars produced from the model compounds. 7 references, 12 figures, 2 tables.
Date: May 1, 1984
Creator: Calo, J.M.; Suubers, E.M.; Wojtowicz, M. & Lilly, W.
Partner: UNT Libraries Government Documents Department

Characterization of porosity via secondary reactions. Quarterly technical progress report, 1 July 1993--30 September 1993

Description: Specific surface area is of paramount importance for all heterogeneous interactions occurring at coal char surfaces. Accessibility of this surface area is governed by the pore structure morphology of the char, which varies over a considerable range and which is determined by a large number of factors including the nature of the porosity prior to carbonization, the carbonization process, and extent and method of any subsequent activation or gasification. A persistent problem in this area has been the reliable, quantitative measurement of the resultant porosity, especially the micropores. The current project is directed at the development of a new approach to this very old problem. During the course of recent work applying temperature programmed desorption (TPD) to the determination of energetic distributions of oxygen complexes on the surfaces of oxidized coal chars, the authors discovered that secondary interactions occurring within the char structure during TPD produce characteristic features that appear to be quite sensitive to char porosity. The relative and absolute extents of these secondary interactions form the basis of a potential characterization technique. Here the authors report on the progress that has been made in the construction, development and testing of a new TPD-MS/TGA system being developed in their laboratory. The project plan also includes the use of other techniques to characterize porosity for the purposes of comparison, quantification, and validation. It is noted that at least two other more well established methods will be used in such a manner: specifically, gas adsorption techniques and small angle scattering.
Date: December 31, 1993
Creator: Calo, J. M. & Zhang, L.
Partner: UNT Libraries Government Documents Department

Active sites in char gasification: Final technical report

Description: Among the key variables in the design of gasifiers and combustors is the reactivity of the chars which must be gasified or combusted. Significant loss of unburned char is unacceptable in virtually any process; the provision of sufficient residence time for complete conversion is essential. A very wide range of reactivities are observed, depending upon the nature of the char in a process. The current work focuses on furthering the understanding of gasification reactivities of chars. It has been well established that the reactivity of char to gasification generally depends upon three principal factors: (1) the concentration of ''active sites'' in the char; (2) mass transfer within the char; and (3) the type and concentration of catalytic impurities in the char. The present study primarily addresses the first factor. The subject of this research is the origin, nature, and fate of active sites in chars derived from parent hydrocarbons with coal-like structure. The nature and number of the active sites and their reactivity towards oxygen are examined in ''model'' chars derived from phenol-formaldehyde type resins. How the active sites are lost by the process of thermal annealing during heat treatment of chars are studied, and actual rate for the annealing process is derived. Since intrinsic char reactivities are of primary interest in the present study, a fair amount of attention was given to the model char synthesis and handling so that the effect of catalytic impurities and oxygen-containing functional groups in the chemical structure of the material were minimized, if not completely eliminated. The project would not be considered complete without comparing characteristic features of synthetic chars with kinetic behavior exhibited by natural chars, including coal chars.
Date: September 1, 1987
Creator: Wojtowicz, M.; Lilly, W.D.; Perkins, M.T.; Hradil, G.; Calo, J.M. & Suuberg, E.M.
Partner: UNT Libraries Government Documents Department

Reactivity of young chars via energetic distribution measurements. Final report, 1 September 1990--31 December 1994

Description: We have developed what we believe to be the very first, a priori, correlation/prediction technique for the gasification reactivity of coal char. With this method the gasification reactivity of a coal char as a function of temperature can be correlated using the data from a temperature programmed desorption (TPD) experiment following gasification under conditions where the reactivity is controlled by the thermal desorption of oxygen surface complexes formed during gasification. The current project was directed at extending and developing related techniques for the characterization and prediction/correlation of the reactivity of the ``young`` chars to CO{sub 2} and steam. Of particular interest was mapping of the reactivity behavior of the resultant chars, as revealed by the energetic heterogeneity of the complexes with char preparation conditions.
Date: January 1, 1996
Creator: Calo, J.M.; Zhang, L.; Lu, W. & Lilly, W.D.
Partner: UNT Libraries Government Documents Department

Characterization of porosity via secondary reactions. Quarterly technical progress report, 1 April 1995--30 June 1995

Description: In the previous quarterly report (DE-FG22-91PC91305-14), we presented an analysis of small angle neutron scattering (SANS) data obtained for Pittsburgh {number_sign}8 coal char. These samples exhibited considerable scattering. However, when the voids between the particles were filled with a liquid that had the same neutron scattering density as the carbon, the amount of scattering was reduced by more than two orders of magnitude. Analysis of the scattering invariant in terms of surface area showed that the char had very little porosity. To date this has been the only contrast matching SANS study of carbon and the first recognition that interparticle scattering effects are important. In this report, we focus on SANS data obtained for a very different char--a phenolic resin char (PRC). The following was accomplished during the reporting period: contrast matching, SANS data obtained for resin char has been analyzed in detail. Conclusions derived from this analysis include: contrast matching SANS has been demonstrated to be a useful technique for monitoring the activation/gasification process. It is demonstrated how this technique can be used to address such important issues as the role of ``closed`` vs ``open`` porosity, and interparticle scattering. It has been used here to establish that the development of porosity in phenolic resin char upon gasification in air proceeds primarily by ``opening `` or originally ``closed`` porosity. This is quite different than the behavior of Pittsburgh {number_sign}8 coal char. for example, as presented in the previous quarterly report.
Date: December 31, 1995
Creator: Calo, J.M.; Hall, P.J.; Antxustegi, M.M. & Zhang, L.
Partner: UNT Libraries Government Documents Department

Characterization of porosity via secondary reactions. Quarterly technical progress report, 1 January 1995--31 March 1995

Description: The following was accomplished during the reporting period: Small angle neutron scattering (SANS) data were obtained for Pittsburgh {number_sign}8 coal char samples at various levels of bum-off at the Intense Pulsed Neutron Source (IPNS) of the Argonne National Laboratory on the small angle diffractometer (SAD) instrument. The Pittsburgh {number_sign}8 samples complement previous SANS data obtained for non-mineral matter-containing phenol-formaldehyde resin char samples. A contrast-matching technique involving the comparison of scattering data for ``dry`` samples with data from the same samples saturated in deuterated toluene, show that the ungasified Pittsburgh {number_sign}8 char has very little closed porosity and, consequently, that pore development during gasification proceeds by the creation of new pores. In the early stages of gasification (< 4.5% burn-off) a pore system with significant microporosity is produced. In later stages of gasification (4.5%--13.5% bum-off) the tendency is to open these micropores, producing a pore system with a broad size distribution. Nitrogen adsorption isotherms (77K) were determined for all the same samples for which SANS data were obtained in order to provide a corroborative check on their porosity characteristics.
Date: August 1, 1995
Creator: Calo, J.M.; Hall, P.J.; Antxustegi, M.M. & Zhang, L.
Partner: UNT Libraries Government Documents Department

Reactivity of young chars via energetic distribution measurements

Description: In this report, we present some preliminary work performed on the effect of CO{sub 2} partial pressure on temperature programmed desorption spectra from CO{sub 2}-oxidized chars. The following was accomplished during the reporting period: Temperature programmed desorption (TPD) experiments were conducted on oxidized resin and Wyodak coal char samples gasified under varying different CO{sub 2} partial pressures. The following observations were made: CO{sub 2} partial pressure can be an important factor affecting TPD spectra. Generally, the total amount of surface oxygen desorbed as CO and CO{sub 2} increases with CO{sub 2} partial pressure during gasification for both resin char and Wyodak coal char. The total amount of oxygen desorbed is also a function of gasification temperature. Apparently, the higher the gasification temperature, the more CO and CO{sub 2} are desorbed. As an example, for 0.33 atm CO{sub 2} partial pressure, the peak CO desorption rates are 0.17 mmole/g/min and 0.13 mmole/g/min, corresponding to gasification temperature 1223K and 1173K. 12 refs., 8 figs.
Date: January 1, 1991
Creator: Calo, J.M.; Zhang, L.H.; Rachel, W.G. & Lilly, W.D.
Partner: UNT Libraries Government Documents Department

Reactivity of young chars via energetic distribution measurements

Description: The temperature programmed desorption (TPD) has become a standard technique for investigating the physico-chemical state of adsorbed species on surfaces. In this reporting period, a new TPD-MS/TGA (mass spectrometry/thermal gravimetric analysis) system has been designed, and all the necessary components have been acquired. This new system is built around a new Cahn D-200 digital recording microbalance, which was recently purchased for this purpose. The TPD reactor essentially becomes the hangdown'' tube for this microbalance. The control and data logging of this new experimental system will be performed using a Macintosh II microcomputer with a GW Instruments 625 Jr. interface. A new hangdown'' tube is being constructed, as well as a new furnace to accommodate it.
Date: January 1, 1991
Creator: Calo, J.M.; Zhang, L.H. & Lilly, W.D.
Partner: UNT Libraries Government Documents Department

Reactivity of young chars via energetic distribution measurements

Description: In this report, we present some preliminary work performed on the effect of inert'', diluent gases on the O{sub 2} and CO{sub 2} reactivities of chars, and the corresponding temperature programmed desorption spectra of the oxygen surface complexes. We also present some of the initial data obtained by operating the TPD reactor under vacuum. The following was accomplished during the reporting period: TPD spectra were obtained resin for resin and Wyodak coal char samples gasified in mixtures of various inert'', diluent gases and either O{sub 2} or CO{sub 2} as the oxidants. The effects of helium, argon, nitrogen, sulfur hexafluoride, and xenon diluent gases on reactivity were investigated. Although the diluent gas generally seemed to affect the reactivity, the expected trend in molecular weight was not clearly discernible. In view of these results, the reproducibility of the diluent/oxidant mixture compositions came under suspicion. As a result, we are now switching to pre-mixed gases for these types of studies. 13 refs., 8 figs., 2 tabs.
Date: January 1, 1991
Creator: Calo, J.M.; Zhang, L.H.; Rachel, W.G. & Lilly, W.D.
Partner: UNT Libraries Government Documents Department

Characterization of porosity via secondary reactions

Description: Specific surface area, as well as its accessibility to gaseous reactants, are of paramount importance for all heterogeneous interactions occurring at coal char surfaces. Accessibility of this surface area is governed by the pore structure morphology of the char; i.e., pore size distribution, tortuosity, intersections, shape, etc. The porosity morphology of coal chars varies over a considerable range and is determined by a large number of factors including the nature of the porosity of the precursor material prior to carbonization, the carbonization process, and extent and method of any subsequent activation or gasification. A persistent problem in this area has been the reliable, quantitative measurement and characterization of the resultant porosity, especially the micropores. For example, electron microscopy tends to be qualitative; small angle X-ray or small angle neutron scattering (SAXS/SANS) can suffer from sensitivity to interpretive models, and the inability to distinguish porosity that communicates with the surface from that which does not; and gas adsorption techniques also have several well known drawbacks. The latter, however, are perhaps the most reliable in general, but yield pore size distributions indirectly via surface area and pore volume measurements, and can also be laborious and time-consuming. Therefore, there is still a critical need for practical and fade techniques to characterize the porosity of coal chars.
Date: January 1, 1992
Creator: Calo, J.M.; Zhang, L. & Lilly, W.D.
Partner: UNT Libraries Government Documents Department