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The thermal decomposition behavior of ammonium perchlorate and of an ammonium-perchlorate-based composite propellant

Description: The thermal decomposition of ammonium perchlorate (AP) and ammonium-perchlorate-based composite propellants is studied using the simultaneous thermogravimetric modulated beam mass spectrometry (STMBMS) technique. The main objective of the present work is to evaluate whether the STMBMS can provide new data on these materials that will have sufficient detail on the reaction mechanisms and associated reaction kinetics to permit creation of a detailed model of the thermal decomposition process. Such a model is a necessary ingredient to engineering models of ignition and slow-cookoff for these AP-based composite propellants. Results show that the decomposition of pure AP is controlled by two processes. One occurs at lower temperatures (240 to 270 C), produces mainly H{sub 2}O, O{sub 2}, Cl{sub 2}, N{sub 2}O and HCl, and is shown to occur in the solid phase within the AP particles. 200{micro} diameter AP particles undergo 25% decomposition in the solid phase, whereas 20{micro} diameter AP particles undergo only 13% decomposition. The second process is dissociative sublimation of AP to NH{sub 3} + HClO{sub 4} followed by the decomposition of, and reaction between, these two products in the gas phase. The dissociative sublimation process occurs over the entire temperature range of AP decomposition, but only becomes dominant at temperatures above those for the solid-phase decomposition. AP-based composite propellants are used extensively in both small tactical rocket motors and large strategic rocket systems.
Date: March 24, 1998
Creator: Behrens, R. & Minier, L.
Partner: UNT Libraries Government Documents Department

Flamelet/flow interaction in premixed turbulent flames: simultaneous measurements of gas velocity and flamelet position

Description: An experimental technique for obtaining simultaneous measurements of fluid velocity and flamelet position in premixed flames is described and applied in a turbulent V-flame. The flamelet position information is used to calculate conditional velocity statistics, conditional on both zone (reactants or products) as well as conditional on distance from the flamelet. The conditional zone statistics demonstrate that increases (or decreases) in turbulence across the flame are dependent on axial position and location within the flame brush. The product- zone conditional covariance, coupled with the measured conditional mean velocity profiles, indicate that turbulence generation by shear may be a significant contribution to product zone turbulence levels. Velocity statistics conditional on distance from the flamelet demonstrate a considerable interaction between the flamelet and velocity field. Man and rms velocities vary significantly with proximity to the flamelet, such that differences in velocities which which occur just across the flamelet surface. The change in rms velocities just across the flamelet is found to be anisotropic, with the largest increase (smallest decrease) occurring in the axial velocity component. Rms velocities conditional on flamelet position further support the hypothesis that increased product gas velocity fluctuations may have a significant component associated with turbulence generation by mean shear.
Date: December 1, 1996
Creator: Miles, P.C. & Gouldin, F.C.
Partner: UNT Libraries Government Documents Department

VAPOR PRESSURES AND HEATS OF VAPORIZATION OF PRIMARY COAL TARS

Description: This project had as its main focus the determination of vapor pressures of coal pyrolysis tars. It involved performing measurements of these vapor pressures and from them, developing vapor pressure correlations suitable for use in advanced pyrolysis models (those models which explicitly account for mass transport limitations). This report is divided into five main chapters. Each chapter is a relatively stand-alone section. Chapter A reviews the general nature of coal tars and gives a summary of existing vapor pressure correlations for coal tars and model compounds. Chapter B summarizes the main experimental approaches for coal tar preparation and characterization which have been used throughout the project. Chapter C is concerned with the selection of the model compounds for coal pyrolysis tars and reviews the data available to us on the vapor pressures of high boiling point aromatic compounds. This chapter also deals with the question of identifying factors that govern the vapor pressures of coal tar model materials and their mixtures. Chapter D covers the vapor pressures and heats of vaporization of primary cellulose tars. Chapter E discusses the results of the main focus of this study. In summary, this work provides improved understanding of the volatility of coal and cellulose pyrolysis tars. It has resulted in new experimentally verified vapor pressure correlations for use in pyrolysis models. Further research on this topic should aim at developing general vapor pressure correlations for all coal tars, based on their molecular weight together with certain specific chemical characteristics i.e. hydroxyl group content.
Date: July 1, 1997
Creator: Suuberg, Eric M. & Oja, Vahur
Partner: UNT Libraries Government Documents Department

Coupling experimental data and a prototype model to probe the physical and chemical processes of 2,4-dinitroimidazole solid-phase thermal decomposition

Description: The time-dependent, solid-phase thermal decomposition behavior of 2,4-dinitroimidazole (2,4-DNI) has been measured utilizing simultaneous thermogravimetric modulated beam mass spectrometry (STMBMS) methods. The decomposition products consist of gaseous and non-volatile polymeric products. The temporal behavior of the gas formation rates of the identified products indicate that the overall thermal decomposition process is complex. In isothermal experiments with 2,4-DNI in the solid phase, four distinguishing features are observed: (1) elevated rates of gas formation are observed during the early stages of the decomposition, which appear to be correlated to the presence of exogenous water in the sample; (2) this is followed by a period of relatively constant rates of gas formation; (3) next, the rates of gas formation accelerate, characteristic of an autocatalytic reaction; (4) finally, the 2,4-DNI is depleted and gaseous decomposition products continue to evolve at a decreasing rate. A physicochemical and mathematical model of the decomposition of 2,4-DNI has been developed and applied to the experimental results. The first generation of this model is described in this paper. Differences between the first generation of the model and the experimental data collected under different conditions suggest refinements for the next generation of the model.
Date: December 31, 1998
Creator: Behrens, R.; Minier, L. & Bulusu, S.
Partner: UNT Libraries Government Documents Department

Mechanistic and kinetic studies of the thermal decomposition of TNAZ and NDNAZ

Description: The authors have studied the mechanism and detailed reaction kinetics of the thermal decomposition of 1,3,3-trinitroazetidine (TNAZ), and separately, its key decomposition intermediate, 1-nitroso-3,3-dinitroacetidine (NDNAZ), using a simultaneous thermogravimetric modulated beam mass spectrometer (STMBMS). These decompositions were conducted in a sealed alumina cell with a 2.5 {micro}m orifice, at varying temperatures and at a range of isothermal temperatures (at 10 C intervals from 120--160 C for NDNAZ and 160--210 C for TNAZ). The gaseous products have been identified and their rates of formation have been measured as a function of time, temperature, and pressure. This system is complex, with TNAZ decomposing by four separate routes, one of which leads to NDNAZ, which itself decomposes by at least two distinct routes.
Date: December 31, 1998
Creator: Anderson, K.; Homsy, J.; Behrens, R. & Bulusu, S.
Partner: UNT Libraries Government Documents Department

Hydropyrolysis of biomass

Description: The pyrolysis and hydropyrolysis of biomass was investigated. Experimental runs using the biomass (Poplar wood sawdust) were performed using a tubular reactor of dimensions 1 inch inside diameter and 8 feet long heated at a temperature of 800 C and pressures between 450 and 750 psig. At low heat-up rate the reaction precedes in two steps. First pyrolysis takes place at temperatures of 300 to 400 c and subsequent hydropyrolysis takes place at 700 C and above. This is also confirmed by pressurized thermogravimetric analysis (PTGA). Under conditions of rapid heat-up at higher temperatures and higher hydrogen pressure gasification and hydrogasification of biomass is especially effective in producing carbon monoxide and methane. An overall conversion of 88 to 90 wt % of biomass was obtained. This value is in agreement with the previous work of flash pyrolysis and hydropyrolysis of biomass for rapid heat-up and short residence time. Initial rates of biomass conversion indicate that the rate increases significantly with increase in hydrogen pressure. At 800 C and 755 psig the initial rate of biomass conversion to gases is 0.92 1/min.
Date: January 1, 1992
Creator: Kobayashi, Atsushi & Steinberg, M.
Partner: UNT Libraries Government Documents Department

Core-Based Integrated Sedimentologic, Stratigraphic, and Geochemical Analysis of the Oil Shale Bearing Green River Formation, Uinta Basin, Utah

Description: An integrated detailed sedimentologic, stratigraphic, and geochemical study of Utah's Green River Formation has found that Lake Uinta evolved in three phases (1) a freshwater rising lake phase below the Mahogany zone, (2) an anoxic deep lake phase above the base of the Mahogany zone and (3) a hypersaline lake phase within the middle and upper R-8. This long term lake evolution was driven by tectonic basin development and the balance of sediment and water fill with the neighboring basins, as postulated by models developed from the Greater Green River Basin by Carroll and Bohacs (1999). Early Eocene abrupt global-warming events may have had significant control on deposition through the amount of sediment production and deposition rates, such that lean zones below the Mahogany zone record hyperthermal events and rich zones record periods between hyperthermals. This type of climatic control on short-term and long-term lake evolution and deposition has been previously overlooked. This geologic history contains key points relevant to oil shale development and engineering design including: (1) Stratigraphic changes in oil shale quality and composition are systematic and can be related to spatial and temporal changes in the depositional environment and basin dynamics. (2) The inorganic mineral matrix of oil shale units changes significantly from clay mineral/dolomite dominated to calcite above the base of the Mahogany zone. This variation may result in significant differences in pyrolysis products and geomechanical properties relevant to development and should be incorporated into engineering experiments. (3) This study includes a region in the Uinta Basin that would be highly prospective for application of in-situ production techniques. Stratigraphic targets for in-situ recovery techniques should extend above and below the Mahogany zone and include the upper R-6 and lower R-8.
Date: April 11, 2011
Creator: Birgenheier, Lauren P. & Michael D. Vanden Berg,
Partner: UNT Libraries Government Documents Department

METHANE de-NOX FOR UTILITY PC BOILERS

Description: The project seeks to develop and validate a new pulverized coal combustion system to reduce utility PC boiler NO{sub x} emissions to 0.15 lb per million Btu or less without post-combustion flue gas cleaning. Work during previous reporting periods completed the design, installation, shakedown and initial PRB coal testing of a 3-million Btu/h pilot system at BBP's Pilot-Scale Combustion Facility (PSCF) in Worcester, MA. Based on these results, modifications to the gas-fired preheat combustor and PC burner were defined, along with a modified testing plan and schedule. A revised subcontract was executed with BBP to reflect changes in the pilot testing program. Modeling activities were continued to develop and verify revised design approaches for both the Preheat gas combustor and PC burner. Reactivation of the pilot test system was then begun with BBP personnel. During the current reporting period, reactivation of the pilot test system was completed with the modified Preheat gas combustor. Following shakedown of the modified gas combustor alone, a series of successful tests of the new combustor with PRB coal using the original PC burner were completed. NO{sub x} at the furnace exit was reduced significantly with the modified gas combustor, to as low as 150 ppm with only 36 ppm CO (both corrected to 3% O{sub 2}). Concurrent with testing, GTI and BBP collaborated on development of two modified designs for the PC burner optimized to fire preheated char and pyrolysis products from the Preheat gas combustor.
Date: October 29, 2002
Creator: Rabovitser, Joseph; Bryan, Bruce; Nester, Serguei & Wohadlo, Stan
Partner: UNT Libraries Government Documents Department

Thermal decomposition studies of 1,3,3-trinitroazetidine (TNAZ) and 1-nitroso-3,3-dinitroazetidine (NDNAZ) by simultaneous thermogravimetric modulated beam mass spectroscopy

Description: The initial results from a study of the thermal decomposition of TNAZ, TNAZ-1-{sup 15}NO{sub 2} and NDNAZ using the simultaneous thermogravimetric modulated beam mass spectrometer (STMBMS) are presented. The major products formed in the decomposition of TNAZ are NO{sub 2} and NO with slightly lesser amounts of H{sub 2}O, HCN, CO/N{sub 2}, CO{sub 2}/N{sub 2}O and NDNAZ. The major product formed in the decomposition of NDNAZ is NO with lesser amounts of H{sub 2}O, HCN, CO/N{sub 2}O. The lower molecular weight products are similar to those observed in RSFTIR and IRMPD studies conducted previously by others. However, this study has shown that the mononitroso analogue of TNAZ, NDNAZ, is an important intermediate formed during the decomposition of TNAZ. It plays an important role in determining the identity of the products formed in the decomposition of TNAZ. The temporal behaviors Of the ion signals associated with the various thermal decomposition products from TNAZ, TNAZ-1-{sup 15}NO{sub 2} and NDNAZ are also presented. The illustrate the evolution sequence of the various products that are associated with the different reaction pathways that control the decomposition of these materials. In particular, the study of the {sup 15}N-labeled sample revealed that NO{sub 2} originates from both the likely sites in the TNAZ molecule and that the cleavage of the nitramine-NO{sub 2} group precedes that of the C-NO{sub 2} cleavage, resulting in similar sequences in the formation of NO and NDNAZ also.
Date: December 1, 1995
Creator: Behrens, R., Jr. & Bulusu, S.
Partner: UNT Libraries Government Documents Department

Catalytic pyrolysis of plastic wastes - Towards an economically viable process

Description: The ultimate goal of our project is an economically viable pyrolysis process to recover useful fuels and/or chemicals from plastics- containing wastes. This paper reports the effects of various promoted and unpromoted binary oxide catalysts on yields and compositions of liquid organic products, as measured in a small laboratory pyrolysis reactor. On the basis of these results, a commercial scale catalytic pyrolysis reactor was simulated by the Aspen software and rough costs were estimated. The results suggest that such a process has potential economic viability.
Date: July 1, 1996
Creator: McIntosh, M.J.; Arzoumanidis, G.G. & Brockmeier, F.E.
Partner: UNT Libraries Government Documents Department

Experimental investigation of hydrous pyrolysis of diesel fuel and the effect of pyrolysis products on performance of the candidate nuclear waste repository at Yucca Mountain, Nevada

Description: It is thought that a significant amount of diesel fuel and other hydrocarbon-rich phases may remain inside the candidate nuclear waste repository at Yucca Mountain after construction and subsequent emplacement of radioactive waste. Although the proposed repository horizon is above the water table, the remnant hydrocarbon phases may react with hydrothermal solutions generated by high temperature conditions that will prevail for a period of time in the repository. The preliminary experimental results of this study show that diesel fuel hydrous pyrolysis is minimal at 200{degrees}C and 70 bars. The composition of the diesel fuel remained constant throughout the experiment and the concentration of carboxylic acids in the aqueous phases was only slightly above the detection limit (1-2 ppm) of the analytical technique.
Date: January 1, 1994
Creator: Jackson, K.J. & Carroll, S.A.
Partner: UNT Libraries Government Documents Department

A study of the solid-phase thermal decomposition of NTO using simultaneous thermogravimetric modulated beam mass spectrometry (STMBMS)

Description: The solid phase thermal reaction chemistry of NTO between 190 and 250 C is presently being evaluated by utilizing STMBMS, a technique that enables the authors to measure the vapor pressure of NTO and to explore the reaction mechanisms and chemical kinetics associated with the NTO thermal decomposition process. The vapor pressure of NTO is expressed as Log{sub 10} p(torr) = 12.5137 + 6,296.553(1/t{sub k}) and the {Delta}H{sub subl} = 28.71 {+-} 0.07 kcal/mol (120.01 {+-} 0.29 kJ/mol). The pyrolysis of NTO results in the formation of gaseous products and a condensed-phase residue. The identity of the major gaseous products and their origin from within the NTO molecules are determined based on the results from pyrolysis of NTO, NTO-3-{sup 13}C, NTO-1,2-{sup 15}N{sub 2} and NTO-{sup 2}H{sub 2}. Identification of the products show the major gaseous products to be N{sub 2}, CO{sub 2}, NO, HNCO, H{sub 2}O and some N{sub 2}O, CO, HCN and NH{sub 3}. The N{sub 2} is mostly derived from the N-1 and N-2 positions with some being from the N-4 and N-1 or N-2 positions. The CO{sub 2} is derived from both carbons in the NTO molecule in comparable amounts. The residue has an elemental formula of C{sub 2.1}H{sub .26}N{sub 2.9}O and FTIR analysis suggests that the residue is polyurea- and polycarbamate-like in nature. The temporal behaviors of the rates of formation of the gaseous products indicate that the overall thermal decomposition of NTO in the temperature range evaluated involves four major processes: (1) NTO sublimation; (2) an apparent solid-solid phase transition between 190 and 195 C; (3) a decomposition regime induced by the presence of exogenous H{sub 2}O at the onset of decomposition; and (4) a decomposition regime that occurs at the onset of decomposition and continues until the depletion of NTO. Decomposition pathways that are ...
Date: January 1, 1997
Creator: Minier, L.; Behrens, R. & Burkey, T.J.
Partner: UNT Libraries Government Documents Department

Advanced Lost Foam Casting Technology

Description: This report describes the research done under the six tasks to improve the process and make it more functional in an industrial environment. Task 1: Pattern Pyrolysis Products and Pattern Properties Task 2: Coating Quality Control Task 3: Fill and Solidification Code Task 4: Alternate Pattern Materials Task 5: Casting Distortion Task 6: Technology Transfer
Date: November 30, 2000
Creator: Bates, Charles E.; Littleton, Harry E.; Askeland, Don; Molibog, Taras; Hopper, Jason & Vatankhah, Ben
Partner: UNT Libraries Government Documents Department

Transformations in organic sulfur speciation during maturation of Monterey shale: Constraints from laboratory experiments

Description: A series of hydrous pyrolysis experiments were conducted at temperatures ranging from 125 to 360C at 350 bars pressure to examine variations in sulfur speciation during thermal maturation of Monterey shale. The total sediment, kerogen and bitumen from each experiment in addition to unheated representatives were analyzed via x-ray absorption spectroscopy, pyrolysis-gas chromatography, {sup 30}NMR spectrometry, elemental analysis, thin-layer chromatography and reflected light microscopy. Based on these measurements, it was possible to recognize three distinct temperature regimes, within which the type and amount of sulfur in the analyzed fractions underwent transformations: (1) between 150 and 225C significant proportion of kerogen-bound sulfur is lost probably due to the collapse of polysulfide bridges; (2) between 225 and 275C, cleavage of -S-S- and -S-C- linkages within the kerogen is believed to occur, resulting in substantial production of polar sulfur-rich bitumen; (3) above 275C total bitumen yields as well as the proportion of bitumen sulfur decrease, while C-C bond scission leads to increased yields of saturated and aromatic hydrocarbons. The results from this study clearly and quantitatively establish a link between organically-bound sulfur, and more specifically, organic polysulfides, and the low-temperature evolution of soluble petroleum-like products (bitumen) from sulfur-rich source rocks.
Date: April 1995
Creator: Nelson, B. C.; Eglinton, T. I.; Seewald, J. S.; Vairavamurthy, M. A. & Miknis, F. P.
Partner: UNT Libraries Government Documents Department

Effect of pulsation on black liquor gasification. Final report

Description: Pyrolysis is an endothermic process. The heat of reaction is provided either by partial combustion of the waste or by heat transfer from an external combustion process. In one proposed system black liquor is pyrolized in a fluidized bed to which heat is added through a series of pulse combustor tail pipes submerged in the bed material. This system appears promising because of the relatively high heat transfer in pulse combustors and in fluidized beds. Other advantages of pulse combustors are discussed elsewhere. The process is, however, only economically viable if a part of the pyrolysis products can be used to fire the pulse combustors. The overall goals of this study were to determine: (1) which is the limiting heat transfer rate in the process of transferring heat from the hot combustion products to the pipe, through the pipe, from the tail pipe to the bed and through the bed; i.e., whether increased heat transfer within the pulse combustor will significantly increase the overall heat transfer rate; (2) whether the heat transfer benefits of the pulse combustor can be utilized while maintaining the temperature in the bed within the narrow temperature range required by the process without generating hot spots in the bed; and (3) whether the fuel gas produced during the gasification process can be used to efficiently fire the pulse combustor.
Date: December 1, 1998
Creator: Zinn, B. T.; Jagoda, J.; Jeong, H.; Kushari, A. & Rosen, L. J.
Partner: UNT Libraries Government Documents Department

METHANE de-NOX FOR UTILITY PC BOILERS

Description: The project seeks to develop and validate a new pulverized coal combustion system to reduce utility PC boiler NOx emissions to 0.15 lb per million Btu or less without post-combustion flue gas cleaning. Work during previous reporting periods completed the design, installation, shakedown and initial PRB coal testing of a 3-million Btu/h pilot system at BBP's Pilot-Scale Combustion Facility (PSCF) in Worcester, MA. Based on these results, modifications to the gas-fired preheat combustor and PC burner were defined, along with a modified testing plan and schedule. A revised subcontract was executed with BBP to reflect changes in the pilot testing program. Modeling activities were continued to develop and verify revised design approaches for both the Preheat gas combustor and PC burner. Reactivation of the pilot test system was then begun with BBP personnel. During the previous reporting period, reactivation of the pilot test system was completed with the modified Preheat gas combustor. Following shakedown of the modified gas combustor alone, a series of successful tests of the new combustor with PRB coal using the original PC burner were completed. NOx at the furnace exit was reduced significantly with the modified gas combustor, to as low as 150 ppm with only 36 ppm CO (both corrected to 3% O2). Concurrent with testing, GTI and BBP collaborated on development of two modified designs for the PC burner optimized to fire preheated char and pyrolysis products from the Preheat gas combustor. During the current reporting period, one of the two modified PC burner designs was fabricated and installed in the pilot test facility. Testing of the modified pilot system (modified gas combustor and modified PC burner) during the quarter included 38 tests with PRB coal. NOx reduction was significantly improved to levels as low as 60-100 ppmv with CO in the range of ...
Date: January 31, 2002
Creator: Rabovitser, Joseph; Bryan, Bruce; Nester, Serguei & Wohadlo, Stan
Partner: UNT Libraries Government Documents Department

Viability of Applying Curie Point Pyrolysis/Gas Chromatography Techniques for Characterization of Ammonium Perchlorate Based Propellants

Description: Curie Point pyrolysis-gas chromatography was investigated for use as a tool for characterization of aged ammonium perchlorate based composite propellants (1). Successful application of the technique will support the surveillance program for the Explosives Materials and Subsystems Department (1). Propellant samples were prepared by separating the propellant into reacted (oxidated) and unreacted zones. The experimental design included the determination of system reliability followed by, reproducibility, sample preparation and analysis of pyrolysis products. Polystyrene was used to verify the reliability of the system and showed good reproducibility. Application of the technique showed high variation in the data. Modifications to sample preparation did not enhance the reproducibility. It was determined that the high concentration of ammonium perchlorate in the propellant matrix was compromising the repeatability of the analysis.
Date: July 1, 2002
Creator: BARNETT, JAMES L. & MONTOYA, BERTHA M.
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

Novel technique for coal pyrolysis and hydrogenation product analysis. Quarterly report, March 1, 1992

Description: This report covers the second to the last quarter of the last year of the three-year grant period. In the final project year, we are focusing on the pyrolysis and oxidative pyrolysis of benzene and benzene acetylene mixtures (along with the pyrolysis of other C5-C12 compounds) in order to develop the VUV-MS technique for compounds more representative of those in coal pyrolysis applications. In the first quarters of the current project year, we have carried out the pyrolysis of mixtures of these compounds without oxygen in a microflow reactor. The acetylene/benzene mixtures were used to gain a better understanding of the mechanisms of molecular growth in such systems specifically to look at the kinetics of aryl-aryl reactions as opposed to small molecule addition to phenyl radicals. Sarofim and coworkers at MIT have recently demonstrated the importance of these reactions in coal processing environments. In the past, the growth mechanism for the formation of midsized PAH has been postulated to involve primarily successive acetylene additions to phenyl-type radicals, our work confirms this as an important mechanism especially for smaller PAH but also investigates conditions where biaryl formation can play an important role in higher hydrocarbon formation. Two different temperature regimes are considered: below 1000 K, where reactivity is dominated by molecular processes, and above 1000 K, where radical chain mechanisms become the dominant pathway. These experiments were carried out at a large range of total pressures and with different diluents.
Date: December 31, 1992
Creator: Pfefferle, L. D.
Partner: UNT Libraries Government Documents Department

Novel technique for coal pyrolysis and hydrogenation product analysis. Quarterly report, January 1991--March 1991

Description: In the second project year, we are concentrating on the pyrolysis of C{sub 6} and C{sub 7} compounds starting with cyclohexane benzene and toluene in order to develop the VUV-MS technique for compounds more representative of those in coal pyrolysis applications. In the first two quarters of the current project year, we have carried out the pyrolysis and oxidative pyrolysis of cyclohexane and toluene and mixtures of these compounds in a microflow reactor. Figures 1 and 2 show mass spectra for cyclohexane pyrolysis and cyclohexane/toluene pyrolysis at 1400 K and 2 ms residence time. The first step in cyclohexane pyrolysis is ring rupture to hexane. The hexane goes through rapid decomposition or, in the case of the hexane/toluene mixture, is also depleted by methyl addition to ultimately form mass 100. The methyl and methane radicals are formed through toluene pyrolysis to phenyl and methyl radicals. Thus mixture data yields insight into pyrolysis of pure compounds because you can titrate species that either are the same mass as the parent fuel or that are important mechanistically but never reach high steady-state concentrations. Mixture data also provides cross checks on species calibrations through reaction rate analysis. Figures 3 and 4 show mass spectra taken during the oxidative pyrolysis of cyclohexane and cyclohexane/toluene for the same conditions as Figures 1 and 2. Note that for these oxidative pyrolysis conditions an important pathway for toluene loss is a reaction with oxygen to form benzaldehyde.
Date: December 31, 1991
Creator: Pfefferle, L. D.
Partner: UNT Libraries Government Documents Department

Evaluation of products recovered from scrap tires for use as asphalt modifiers

Description: Western Research Institute performed rheological tests and water sensitivity tests on asphalt cements that had been modified with carbonous residues obtained from the pyrolysis of scrap tires and waste motor oil. These tests are part of an ongoing program at the University of Wyoming Chemical Engineering Department to evaluate, as asphalt additives, solid carbonous products recovered from the scrap tire and waste motor oil pyrolysis experiments conducted at the University. The tests showed that carbonous residues increased the viscosity and decreased the elasticity of AC-10 and AC-20 asphalts. The tests also indicatedthat asphalt cements modified with carbonous residues were less sensitive to water damage and age embrittlement than unmodified asphalt cements.
Date: May 1, 1992
Creator: McKay, J.
Partner: UNT Libraries Government Documents Department

New Combined Laser Ablation Platform Determines Cell Wall Chemistry (Fact Sheet)

Description: NREL has designed and developed a combined laser ablation/pulsed sample introduction/mass spectrometry platform that integrates pyrolysis and/or laser ablation with resonance-enhanced multiphoton ionization (REMPI) time-of-flight mass spectrometry. Using this apparatus, we can measure the cell wall chemical composition of untreated biomass materials. Understanding the chemical composition of untreated biomass is key to both the biochemical and thermochemical conversion of lignocellulosic biomass to biofuels. In the biochemical conversion process, the new technique provides a better understanding of the chemistry of lignin and will improve accessibility to plant sugars. In thermochemical conversion, the information provided by the new technique may help to reduce the formation of unwanted byproducts during gasification. NREL validated the ability of the system to detect pyrolysis products from plant materials using poplar, a potentially high-impact bioenergy feedstock. In the technique, biomass vapors are produced by laser ablation using the 3rd harmonic of an Nd:YAG laser (355 nm). The resulting vapors are entrained in a free jet expansion of helium, then skimmed and introduced into an ionization region. REMPI is used to ionize the vapors because it is highly sensitive for detecting lignin and aromatic metabolites. The laser ablation method was used to selectively volatilize specific plant tissues and detect lignin-based products from the vapors with enhanced sensitivity. This will allow the determination of lignin distribution in future biomass studies.
Date: September 1, 2011
Partner: UNT Libraries Government Documents Department

Assessment of pulverized-coal-fired combustor performance

Description: During the fifth quarterly period of the program, efforts have continued to focus on the analytical tool development and verification task, and on the bench-scale experimental reactor studies for the screening of key combustion variables. In previous quarters, the selection, upgrading and verification of the required furnace heat transfer models have been reported. These models are now fully operational and have been used to complete a series of screening studies to identify those parameters which most significantly affect the thermal performance of combustion systems. In this present period, the multizone furnace heat transfer model has been further refined by the development of a separate but fully coupled submodel for the calculation of char burnout. This aspect of combustor performance is believed to be an important consideration in the conversion of furnaces to coal firing. Char burnout will not only impact the amount of unburned carbon at the stack, but will also affect local heat transfer levels through the extension of heat-release zones and modification of the properties of the radiating species. In the experimental portion of the program, efforts have focused on the modification of the reactor feed system and measurement techniques in order to alleviate problems leading to poor data repeatibility.
Date: January 1, 1981
Creator: Richter, W.; Clark, W. & Payne, R.
Partner: UNT Libraries Government Documents Department