scholarly journals Modeling of the combustion process of methane hydrate taking into account the kinetics of the decomposition process

2021 ◽  
Vol 2094 (2) ◽  
pp. 022053
Author(s):  
A S Chiglintseva ◽  
I K Gimaltdinov ◽  
I M Bayanov ◽  
M V Stolpovsky
Keyword(s):  
Combustion Process ◽  
Decomposition Process ◽  
Dominant Factor ◽  
Initial Moment ◽  
Conductive Heat ◽  
Closed Volume ◽  
Hydrate Decomposition ◽  
Large Particles ◽  
Basic Equations ◽  
Kinetics Of

Abstract This paper presents a mathematical model of the combustion process of methane gas hydrate in a closed volume, taking into account the kinetics of its decomposition. The system of basic equations, which includes the equations of conservation of mass (for the entire mixture of gases and each component separately), momentum and energy, is supplemented by the conditions for the balance of mass and heat at the boundary of the phase transition. In this case, the dominant factor determining the intensity of hydrate decomposition is the Arrhenius-type kinetics and conductive heat transfer. Based on the numerical solution of the obtained system of equations based on the method of large particles, the temperature and concentration fields of the system are obtained and analyzed. It is shown that at the initial moment of time, the rate of decomposition of the hydrate according to the model that takes into account the kinetics of the decomposition process is higher than that according to the model that does not take it into account.

scholarly journals Determining the mass-related reaction effectiveness factor of large, nonspherical fuel particles for bridging between intrinsic and apparent combustion kinetics

2019 ◽  
Vol 141 (2) ◽  
pp. 797-806 ◽  
Author(s):  
Tibor Szűcs ◽  
Pal Szentannai
Keyword(s):  
Combustion Process ◽  
Effectiveness Factor ◽  
Cfd Modeling ◽  
Combustion Kinetics ◽  
Kinetic Measurements ◽  
Environmental Requirements ◽  
Fuel Particles ◽  
Related Reaction ◽  
Kinetics Of ◽  
Internal Pore

AbstractThe utilization of challenging solid fuels in the energy industry is urged by environmental requirements. The combustion kinetics of these fuel particles differs markedly from that of pulverized coal, mainly because of their larger sizes, irregular (nonspherical) shapes, and versatile internal pore structures. Although the intrinsic reaction kinetic measurements on very small amounts of finely ground samples of these particles are mostly available, a bridge toward their apparent reaction modeling is not evident. In this study, a method is introduced to build this bridge, the goodness of which was proved on the example of an industrially relevant biofuel. To do this, the results of a macroscopic combustion measurement with real samples in a well-modelable environment have to be used, and for considering some not negligible effects, 3D CFD modeling of the experimental environment is also to be applied. The outcome is the mass-related reaction effectiveness factor as a function of the rate of conversion. This variable can be considered as the active fraction of the entire particle mass on its periphery, and it can be used as the crucial element in modeling the combustion process of the same particle under other circumstances by including the actual boundary conditions. Another advantage of this method is its covering inherently the entire combustion process (water and volatile release, and char combustion) and also its applicability for reactors utilizing bigger particles like fluidized bed combustors.

Mechanisms and kinetics of initial pyrolysis and combustion reactions of 1,1-diamino-2,2-dinitroethylene from density functional tight-binding molecular dynamics simulations

2019 ◽  
Vol 97 (11) ◽  
pp. 795-804 ◽  
Author(s):  
Dong Xiang ◽  
Weihua Zhu
Keyword(s):  
Activation Energy ◽  
Molecular Dynamics ◽  
Density Functional ◽  
Tight Binding ◽  
Combustion Process ◽  
Exponential Factor ◽  
Three Stages ◽  
Dynamics Simulations ◽  
Combustion Processes ◽  
Kinetics Of

The density functional tight-binding molecular dynamics approach was used to study the mechanisms and kinetics of initial pyrolysis and combustion reactions of isolated and multi-molecular FOX-7. Based on the thermal cleavage of bridge bonds, the pyrolysis process of FOX-7 can be divided into three stages. However, the combustion process can be divided into five decomposition stages, which is much more complex than the pyrolysis reactions. The vibrations in the mean temperature contain nodes signifying the formation of new products and thereby the transitions between the various stages in the pyrolysis and combustion processes. Activation energy and pre-exponential factor for the pyrolysis and combustion reactions of FOX-7 were obtained from the kinetic analysis. It is found that the activation energy of its pyrolysis and combustion reactions are very low, making both take place fast. Our simulations provide the first atomic-level look at the full dynamics of the complicated pyrolysis and combustion process of FOX-7.

scholarly journals 3D Numerical Study of External Axial Magnetic Field-Controlled High-Current GMAW Metal Transfer Behavior

Materials ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 5792
Author(s):  
Lei Xiao ◽  
Ding Fan ◽  
Jiankang Huang ◽  
Shinichi Tashiro ◽  
Manabu Tanaka
Keyword(s):  
Magnetic Field ◽  
Axial Magnetic Field ◽  
Numerical Study ◽  
Metal Transfer ◽  
Temperature Fields ◽  
Dominant Factor ◽  
Conductive Heat ◽  
High Current ◽  
Spray Transfer ◽  
Transfer Behavior

For gas metal arc welding (GMAW), increasing the welding current is the most effective way to improve welding efficiency. However, much higher current decreases the welding quality as a result of metal rotating-spray transfer phenomena in the high-current GMAW process. In this work, the external axial magnetic field (EAMF) was applied to the high-current GMAW process to control the metal transfer and decrease the welding spatters. A unified arc-droplet coupled model for high-current GMAW using EAMFs was built to investigate the metal rotating-spray transfer behavior. The temperature fields, flow fields in the arc, and droplet were revealed. Considering all the heat transferred to the molten metal, the Joule heat was found to be the dominant factor affecting the droplet temperature rise, followed by the anode heat. The conductive heat from the arc contributed less than half the value of the other two. Considering the EAMFs of different alternating frequencies, the arc constricting effects and controlled metal transfer behaviors are discussed. The calculated results agree well with the experimental high-speed camera observations.

Molecular simulation of non-equilibrium methane hydrate decomposition process

2012 ◽  
Vol 44 (1) ◽  
pp. 13-19 ◽  
Author(s):  
S.Alireza Bagherzadeh ◽  
Peter Englezos ◽  
Saman Alavi ◽  
John A. Ripmeester
Keyword(s):  
Molecular Simulation ◽  
Methane Hydrate ◽  
Decomposition Process ◽  
Hydrate Decomposition ◽  
Non Equilibrium

Kinetics of Peroxide Vulcanization of Natural Rubber

2012 ◽  
Vol 28 (4) ◽  
pp. 201-220 ◽  
Author(s):  
Rejitha Rajan ◽  
Siby Varghese ◽  
K.E. George
Keyword(s):  
Mechanical Properties ◽  
Natural Rubber ◽  
Crosslinking Agent ◽  
Decomposition Reaction ◽  
Dominant Factor ◽  
Compression Set ◽  
Cure Time ◽  
Minimum Residual ◽  
Vulcanization Kinetics ◽  
Kinetics Of

This study was undertaken to optimize the vulcanization conditions and explore the effect of residual peroxide in the peroxide vulcanization of natural rubber. The study was followed through the kinetics of the vulcanization reaction at various temperatures viz. 150,155,160 and 165°C. Dicumyl peroxide (DCP) was used as the crosslinking agent. The Monsanto Rheometer was used to investigate the different crosslinking stages and vulcanization kinetics. The thermal decomposition of peroxide followed a first order free radical decomposition reaction. Half-lives at various temperatures were determined. The percentage of residual peroxide was calculated from the cure kinetic data. The effect of residual peroxide on mechanical properties was studied at various peroxide levels and also by extending the cure time (from t90 to t95 and then to t100). Mechanical properties such as tensile strength, elongation at break, modulus and compression set (70 and 100°C) were measured. Excess peroxide was found to cause a high compression set at elevated temperature and the cure time was selected to achieve minimum residual peroxide in the product. Results indicate that peroxide concentration is the dominant factor controlling the crosslink density and hence the properties of the vulcanizates.

scholarly journals Kinetics study and simulation of CO2 absorption into mixed aqueous solutions of methyldiethanolamine and hexylamine

2018 ◽  
Vol 73 ◽  
pp. 19
Author(s):  
Ammar Mehassouel ◽  
Ratiba Derriche ◽  
Chakib Bouallou
Keyword(s):  
Combustion Process ◽  
Co2 Absorption ◽  
Kinetics Study ◽  
Regeneration System ◽  
First Order ◽  
Gas Streams ◽  
Lewis Cell ◽  
Cell Reactor ◽  
Pseudo First Order ◽  
Kinetics Of

This study investigated kinetics of CO2 absorption into mixed methyldiethanolamine (MDEA) and hexylamine (HA) solutions in a Lewis cell reactor. The experiments were conducted in the temperatures 298, 313 and 333 K with mass concentrations MDEA 37 wt.% + HA 3 wt.%, MDEA 35 wt.% + HA 5 wt.% and MDEA 33 wt.% + HA 7 wt.%. Our results showed that adding a small amount of hexylamine enhances the kinetics of CO2 absorption and that the kinetics of CO2 absorption with aqueous MDEA 37 wt.% + HA 3 wt.% is pseudo first order regime with reduced activation energy compared to that of MDEA 40 wt.%. The absorption/regeneration system was simulated using Aspen plus™ software for the treatment of gas streams from cement plant in a post-combustion process. The analysis of our results established that blended solvent MDEA 37 wt.% + HA 3 wt.% gives lower energy consumption than that of MDEA 40 wt.%.

Study Advancement for Multiphase Flow and Heat and Mass Transfer Characteristics for Gas Hydrate Decomposition in South China Sea Offshore Sediment

2013 ◽  
Author(s):  
Xichong Yu ◽  
Jiafei Zhao ◽  
Weixin Pang ◽  
Gang Li ◽  
Yu Liu
Keyword(s):  
Mass Transfer ◽  
Multiphase Flow ◽  
Heat And Mass Transfer ◽  
Gas Hydrate ◽  
Flow Characteristics ◽  
Decomposition Process ◽  
Lattice Boltzmann Model ◽  
Experimental Simulation ◽  
Hydrate Decomposition ◽  
Multi Phase Flow

Gas hydrates are crystalline solids that consist of gas molecules, usually methane, surrounded by water molecules. According to the phase equilibrium characteristics of gas hydrate, there are three basic development methods, including heating, pressure decreasing and chemical injecting. The development process is actually the multi-phase flow process. Currently, there is no good commercial software used to simulate the multiphase flow, heat transmission and mass transfer in the gas hydrate decomposition process. The study is not mature, still in the development and trial stage. So in this paper, we will make a deeply study on the multi-phase flow simulation method of gas hydrate decomposition in the sediment. We try to make breakthrough in the theory and simulate method. According to the different scales, the simulation computation study of flow characteristics model has microcosmic, mesocosmic and macrocosmic scales. In this paper, mesocosmic scales is used to study for the multiphase flow, heat and mass transfer in the offshore gas hydrate decomposition process, and numerical simulation and experimental simulation are together used to study. Study advancements are shown as follows: firstly, conventional Lattice Boltzmann model is modified to new Lattice Boltzmann Model (LBM) based on sediment with gas hydrate and flow characteristics for gas hydrate decomposition, the interaction and density difference between the phases are considered, and Magnetic Resonance Imaging (MRI) visual technology is used to successfully verified to LBM methods. Secondly, contraction core reaction methods based on fractal theory is used to simulate heat and mass transfer in the offshore gas hydrate decomposition process and is successfully verified by experimental simulation for South China Sea offshore gas hydrate sediment.

NOx Emission of Diesel Fuel Blended with Different Saturation Degrees of Biofuel and with Oxygenator

2014 ◽  
Vol 660 ◽  
pp. 397-401 ◽  
Author(s):  
Mohd Fareez Edzuan bin Abdullah ◽  
Mohd Hisyamuddin bin Sulaiman ◽  
Noor Aliah Binti Abdul Majid
Keyword(s):  
Diesel Fuel ◽  
Flue Gas ◽  
Combustion Process ◽  
Nox Emission ◽  
Dominant Factor ◽  
Compression Ignition ◽  
Nox Formation ◽  
Fuel Blends ◽  
Combustion Tests ◽  
Co Emission

This paper discusses the nitrogen oxides (NOx) emission characteristics of compression ignition diesel engine operating on diesel fuel blends with different saturation degrees of biofuel and with methanol. In order to investigate the dominant factor of increased NOx in biofuels, diesel combustion tests were conducted under idling condition and the tailpipe exhaust emissions were measured by a flue gas analyzer. The general trend where NOx emission increased and reduced carbon monoxide (CO) emission in the biofuel and methanol blend cases were observed. The NOx emission levels increased as the biofuel saturation degree decreased, where it may be suggested that the prompt NOx mechanism is significant in total NOx formation of biofuel combustion process.

ANOMALOUS STRESS RELAXATION BEHAVIOR OF POLYCRYSTALLINE ALUMINUM AT LOW TEMPERATURE

2007 ◽  
Vol 21 (10) ◽  
pp. 1745-1754 ◽  
Author(s):  
I. M. GHAURI ◽  
NAVEED AFZAL ◽  
M. ANWAR ◽  
S. A. SIDDIQUE
Keyword(s):  
Stress Relaxation ◽  
Relaxation Rate ◽  
Deformation Process ◽  
Tensile Deformation ◽  
Polycrystalline Aluminum ◽  
Rate Processes ◽  
Basic Equations ◽  
Relaxation Curves ◽  
Kinetics Of ◽  
Barrier Model

The tensile deformation of polycrystalline aluminum (99.999%) was studied between 18 and 300 K. The stress-relaxation at constant strain was determined at strain intervals of about 0.5% with total strain exceeding about 3%. Stress-relaxation curves were logarithmic except at large "t" where they flatten. The relaxation rate "s" was determined by using equation s=d(Δσ)/d ln t, where Δσ(t)=σ0-σ(t) is the amount of stress relaxed at any instant of time "t" from the initial stress level σ0 at which relaxation was allowed to start. The slope ds/dσ0 was observed to attain maxima at about 30 K and minima at about 60 K. The undulation in the temperature dependence of stress relaxation rate in the range 18–60 K is an outcome of changes in the substructures of dislocations which have developed during the deformation process. These changes then require stresses higher than that applied in the basic equations which describe the kinetics of the mode of deformation. The average intrinsic height of potential barrier U0, estimated by means of the single barrier model of stress relaxation, was 1.2±0.3 eV. These values appeared to be compatible with the dislocation-dislocation intersection, controlling the rate processes in polycrystalline aluminum.

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