scholarly journals Investigation of carbon-formation mechanisms and fuel-conversion rates in the adiabatic reformer. Annual report, March 19, 1980-March 19, 1981

1981 ◽  
Author(s):  
Keyword(s):  
Annual Report ◽  
Formation Mechanisms ◽  
Carbon Formation ◽  
Fuel Conversion ◽  
Conversion Rates

scholarly journals Catalytic Combustion of Natural Gas Over Supported Platinum: Flow Reactor Experiments and Detailed Numerical Modeling

1996 ◽  
Author(s):  
Tami C. Bond ◽  
Ryan A. Noguchi ◽  
Chen-Pang Chou ◽  
Rajiv K. Mongia ◽  
Jyh-Yuan Chen ◽  
...  
Keyword(s):  
Numerical Model ◽  
Natural Gas ◽  
Gas Phase ◽  
Conversion Rate ◽  
Catalytic Combustion ◽  
Flow Reactor ◽  
Combustion Process ◽  
Pollutant Emissions ◽  
Fuel Conversion ◽  
Conversion Rates

The use of a noble-metal combustion catalyst such as platinum or palladium in a natural-gas fired turbine can lower NOx (nitrogen oxides, consisting of both NO and NO2) emissions for two reasons. First, most of the combustion occurs on the catalyst surface; surface production of NOx is low or nonexistent. Second, the catalyst permits low temperature combustion below the traditional lean limit, thus inhibiting NOx formation routes in the gas phase. Due to the complexity of the catalytic combustion process, the catalyst has traditionally been modeled as a “black box” that produces a desired amount of fuel conversion. While this approach has been useful for proof-of-concept studies, we expect practical applications to emerge from a greater understanding of the details of the catalytic combustion process. We have constructed a numerical model of catalytic combustion based on the well-accepted CHEMKIN chemical kinetics formalism for gas-phase and surface chemistry. To support the model development, we built a research combustor. We present measured and modeled axial profiles of temperature, fuel conversion, and pollutant emissions for natural-gas combustion over platinum catalysts supported on ceramic honeycomb monoliths. NOx emissions are below 1 ppm, and CO is observed at ppm levels. The data are taken at several lean equivalence ratios and flow rates. Fuel conversion rates occur in two regimes: a low, constant conversion rate and a higher conversion rate that increases linearly with equivalence ratio. The agreement of the numerical model with the measured data is good at temperatures below 900 K; above this temperature, fuel conversion is underpredicted by as much as a factor of two. The predicted surface ignition temperatures agree well with the measured values. Results from the numerical model indicate that the fractional conversion rate of fuel has a linear dependence on the fraction of available surface reaction sites.

Molten salt bubble columns for low-carbon hydrogen from CH4 pyrolysis: mass transfer and carbon formation mechanisms

2020 ◽  
pp. 127407
Author(s):  
Brett Parkinson ◽  
Clemens F. Patzschke ◽  
Dimitrios Nikolis ◽  
Sumathy Raman ◽  
Klaus Hellgardt
Keyword(s):  
Mass Transfer ◽  
Molten Salt ◽  
Bubble Columns ◽  
Formation Mechanisms ◽  
Low Carbon ◽  
Carbon Formation

scholarly journals Formation of NDMA by Chloramination of Nitrogenous Pharmaceuticals

2010 ◽  
Vol 5 (4) ◽  
Author(s):  
J. Le Roux ◽  
H. Gallard ◽  
J.P. Croué
Keyword(s):  
Structural Characteristics ◽  
Haloacetic Acids ◽  
Formation Mechanisms ◽  
Tertiary Amines ◽  
Human Carcinogen ◽  
Conversion Rates ◽  
Water Chlorination ◽  
By Products ◽  
New Formation

Many disinfection by-products (DBPs) are formed during water chlorination, including trihalomethanes (THMs) and haloacetic acids (HAAs). Disinfection with chloramines is often used to reduce the production of regulated DBPs. However, chloramination can lead to the formation of N–nitrosamines, including N–nitrosodimethylamine (NDMA), a probable human carcinogen. The formation mechanisms of NDMA are not fully understood. Proposed mechanisms used dimethylamine (DMA) as a model precursor, but results show that certain widely used tertiary dimethylamines (e.g. the pharmaceutical ranitidine) show much higher conversion rates to NDMA than DMA. These amounts of NDMA cannot be explained by current proposed mechanisms. New formation mechanisms have to be proposed to explain the importance of structural characteristics of tertiary amines for NDMA formation.

scholarly journals Low-Enriched Uranium Fuel Conversion Activities for the High Flux Isotope Reactor, Annual Report for FY 2011

2012 ◽  
Author(s):  
David G Renfro ◽  
David Howard Cook ◽  
James D Freels ◽  
Frederick P Griffin ◽  
Germina Ilas ◽  
...  
Keyword(s):  
Annual Report ◽  
High Flux ◽  
Fuel Conversion ◽  
Uranium Fuel ◽  
Enriched Uranium

The dislocation structure of a 10° [110] tilt boundary in silicon

1983 ◽  
Vol 41 ◽  
pp. 114-115
Author(s):  
B. Cunningham ◽  
D.G. Ast
Keyword(s):  
Dislocation Structure ◽  
Tilt Angle ◽  
Imaging Technique ◽  
Diamond Lattice ◽  
Tilt Boundary ◽  
Formation Mechanisms ◽  
Diffraction Contrast ◽  
Lattice Fringe ◽  
Tilt Boundaries ◽  
Chemically Vapor Deposited

There have Been a number of studies of low-angle, θ < 4°, [10] tilt boundaries in the diamond lattice. Dislocations with Burgers vectors a/2<110>, a/2<112>, a<111> and a<001> have been reported in melt-grown bicrystals of germanium, and dislocations with Burgers vectors a<001> and a/2<112> have been reported in hot-pressed bicrystals of silicon. Most of the dislocations were found to be dissociated, the dissociation widths being dependent on the tilt angle. Possible dissociation schemes and formation mechanisms for the a<001> and a<111> dislocations from the interaction of lattice dislocations have recently been given.The present study reports on the dislocation structure of a 10° [10] tilt boundary in chemically vapor deposited silicon. The dislocations in the boundary were spaced about 1-3nm apart, making them difficult to resolve by conventional diffraction contrast techniques. The dislocation structure was therefore studied by the lattice-fringe imaging technique.

Formation Mechanisms for Multiply Twinned Particles During Nucleation in the Au/MICA System

1975 ◽  
Vol 33 ◽  
pp. 84-85
Author(s):  
Eal H. Lee ◽  
Helmut Poppa
Keyword(s):  
Deposition Time ◽  
High Vacuum ◽  
Dark Field ◽  
Ultra High Vacuum ◽  
Formation Mechanisms ◽  
Heat Treated ◽  
Cluster Density ◽  
Diffraction Patterns ◽  
Crystal Particle ◽  
Multiply Twinned Particles

The formation of thin films of gold on mica has been studied in ultra-high vacuum (5xl0-10 torr) . The mica substrates were heat-treated for 24 hours at 375°C, cleaved, and annealed for 15 minutes at the deposition temperature of 300°C prior to deposition. An impingement flux of 3x1013 atoms cm-2 sec-1 was used. These conditions were found to give high number densities of multiple twin particles and are based on a systematic series of nucleation experiments described elsewhere. Individual deposits of varying deposition time were made and examined by bright and dark field TEM after "cleavage preparation" of highly transparent specimens. In the early stages of growth, the films generally consist of small particles which are either single crystals or multiply twinned; a strong preference for multiply twinned particles was found whenever the particle number densities were high. Fig. 1 shows the stable cluster density ns and the variation with deposition time of multiple twin particle and single crystal particle densities, respectively. Corresponding micrographs and diffraction patterns are shown in Fig. 2.

1999 Annual Report

2000 ◽  
Vol 10 (1) ◽  
pp. 6-6
Author(s):  
Eugene B. Cooper
Keyword(s):  
Annual Report
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