scholarly journals High-Temperature Carbon Deposition on Oxide Surfaces by CO Disproportionation

2016 ◽  
Vol 120 (3) ◽  
pp. 1795-1807 ◽  
Author(s):  
Michaela Kogler ◽  
Eva-Maria Köck ◽  
Bernhard Klötzer ◽  
Thomas Schachinger ◽  
Wolfgang Wallisch ◽  
...  
Keyword(s):  
High Temperature ◽  
Carbon Deposition ◽  
Oxide Surfaces ◽  
Co Disproportionation

Active Chemistry Control for Coolant Helium Applying High-Temperature Gas-Cooled Reactors

2008 ◽  
Author(s):  
Nariaki Sakaba ◽  
Shimpei Hamamoto ◽  
Yoichi Takeda
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Heat Exchanger ◽  
Chemical Composition ◽  
Structural Integrity ◽  
Carbon Deposition ◽  
Control Technology ◽  
Equilibrium Study ◽  
Intermediate Heat Exchanger ◽  
High Temperature Gas

Lifetime extension of high-temperature equipment such as the intermediate heat exchanger of high-temperature gas-cooled reactors (HTGRs) is important from the economical point of view. Since the replacing cost will cause the increasing of the running cost, it is important to reduce replacing times of the high-cost primary equipment during assumed reactor lifetime. In the past, helium chemistry has been controlled by the passive chemistry control technology in which chemical impurity in the coolant helium is removed as low concentration as possible, as does Japan’s HTTR. Although the lifetime of high-temperature equipment almost depends upon the chemistry conditions in the coolant helium, it is necessary to establish an active chemistry control technology to maintain adequate chemical conditions. In this study, carbon deposition which could occur at the surface of the heat transfer tubes of the intermediate heat exchanger and decarburization of the high-temperature material of Hastelloy XR used at the heat transfer tubes were evaluated by referring the actual chemistry data obtained by the HTTR. The chemical equilibrium study contributed to clarify the algorism of the chemistry behaviours to be controlled. The created algorism is planned to be added to the instrumentation system of the helium purification systems. In addition, the chemical composition to be maintained during the reactor operation was proposed by evaluating not only core graphite oxidation but also carbon deposition and decarburization. It was identified when the chemical composition could not keep adequately, injection of 10 ppm carbon monoxide could effectively control the chemical composition to the designated stable area where the high-temperature materials could keep their structural integrity beyond the assumed duration. The proposed active chemistry control technology is expected to contribute economically to the purification systems of the future very high-temperature reactors.

Effect of oxide on carbon deposition behavior of CH4 fuel on Ni/ScSZ cermet anode in high temperature SOFCs

2006 ◽  
Vol 177 (5-6) ◽  
pp. 541-547 ◽  
Author(s):  
K KE ◽  
A GUNJI ◽  
H MORI ◽  
S TSUCHIDA ◽  
H TAKAHASHI ◽  
...  
Keyword(s):  
High Temperature ◽  
Carbon Deposition ◽  
Deposition Behavior

High-Temperature Decomposition of Diisopropyl Methylphosphonate (DIMP) on Alumina: Mechanistic Predictions from Ab Initio Molecular Dynamics

2021 ◽  
Author(s):  
Sohag Biswas ◽  
Bryan Wong
Keyword(s):  
Molecular Dynamics ◽  
High Temperature ◽  
Metal Oxide ◽  
Large Scale ◽  
Activation Barrier ◽  
Chemical Warfare Agents ◽  
Ab Initio Molecular Dynamics ◽  
Oxide Surfaces ◽  
Metal Oxide Surfaces ◽  
Warfare Agents

The enhanced degradation of organophosphorous-based chemical warfare agents (CWAs) on metal-oxide surfaces holds immense promise for neutralization efforts; however, the underlying mechanisms in this process remain poorly understood. We utilize large-scale quantum calculations for the first time to probe the high-temperature degradation of diisopropyl methylphosphonate (DIMP), a nerve agent simulant. Our Born-Oppenheimer molecular dynamics (BOMD) calculations show that the gamma-Al2O3 surface shows immense promise for quickly adsorbing and destroying CWAs. We find that the alumina surface quickly adsorbs DIMP at all temperatures, and subsequent decomposition of DIMP proceeds via a propene elimination. Our BOMD calculations are complemented with metadynamics simulations to produce free energy paths, which show that the activation barrier decreases with temperature and DIMP readily decomposes on gamma-Al2O3. Our first-principle BOMD and metadynamics simulations provide crucial diagnostics for sarin decomposition models and mechanistic information for examining CWA decomposition reactions on other candidate metal oxide surfaces.

The Study of Catalytic Reforming of Coke Oven Gas Producing Hydrogen-Rich Gas

2012 ◽  
Vol 512-515 ◽  
pp. 2271-2276
Author(s):  
Peng Liang ◽  
Jian Hui Li ◽  
Yan Xia Liu ◽  
Tao Liu
Keyword(s):  
High Temperature ◽  
Reaction Temperature ◽  
Carbon Deposition ◽  
Catalyst Surface ◽  
Space Velocity ◽  
Coke Oven ◽  
Coke Oven Gas ◽  
Model Compounds ◽  
Catalytic Reforming ◽  
Catalyst Composition

Two series of nickel-based catalyst, NiO/Al2O3and NiO/MgO/Al2O3were prepared by the impregnation and step-by-step impregnation methods in the experiment. Toluene as the tar model compounds, the effect of catalyst composition and reaction condition on the catalytic conversion of tar components in coke oven gas were investigated. The results showed that to get more methane at higher reaction temperature, catalyst of 0.1% NiO loading is prefered. MgO could reduce the carbon deposition on the catalyst surface. The high temperature was conducive to the formation of H2and CO, but was not favorable for the CH4formation in the investigated temperature. The space velocity had little influence on the production of H2and CO, but the larger space velocity was good for the formation of CH4. In addition, higher H2O /toluene ratio brought a higher H2production, but lower CO and CH4production.

Thermodynamic Analysis of SOFC Systems Using Different Fuel Processors

2004 ◽  
Author(s):  
Roberto Bove ◽  
Nigel M. Sammes
Keyword(s):  
High Temperature ◽  
Solid Oxide Fuel Cells ◽  
Thermodynamic Analysis ◽  
Carbon Deposition ◽  
Solid Oxide ◽  
Temperature Gradients ◽  
Oxide Fuel ◽  
Internal Temperature ◽  
Internal Reforming ◽  
Fuel Cell Operation

Solid oxide fuel cells operate at high temperature and consequently the internal reforming of hydrocarbons, for example methane, can easily be achieved. Nevertheless, since the reforming process is strongly endothermic, internal temperature gradients can be generated, thus producing considerable limitations to the fuel cell operation. Moreover, total internal reforming can lead to carbon deposition in the anode component. In order to avoid these problems total internal reforming is generally not conducted, and part of the fuel is externally pre-reformed. In the present study, different options for the pre-conversion process are considered. The relative system performances are evaluated through a thermodynamic analysis and numerical simulations.

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