Chemical Kinetic Aspects of Solid State Reaction Producing Wollastonite from Rice Husk Silica and Limestone

An industrial mineral wollastonite (CaSiO3) was produced under solid state conditions from rice husk silica and limestone. Reaction was carried out at 900’C to 1300’C for 1 h. The product batches were subjected to XRD and chemical analysis techniques specific for wollastonite. Mole fractions of different product batches were calculated on the basis of accumulated data to study the kinetics. Specific rate constants and reaction rate were also found out. Various probable models of mechanism for reaction were considered and testified with the laid down criterion for suggesting the suitable one. The resulting data were treated with Arrhenius equation as well and activation energy was calculated--therefrom. In addition to finding it’s value from the slope of Arrhenius curve, an alternate method was also applied for this purpose. Both of the values were observed to be comparable. The activation energy required for performed reaction was found to be almost one third of that reported for synthesizing CaSiO3 by using quartz. This referred to the economical preparation of wollastonite by using rice husk as a source of silica instead of quartz.

A tool model for predicting atmospheric chemical kinetics with sensitivity analysis

A package(a tool model) for program of predicting atmospheric chemical kinetics with sensitivity analysis is presented. The new direct method of calculating the first order sensitivity coefficients using sparse matrix technology to chemical kinetics is included in the tool model, it is only necessary to triangularize the matrix related to the Jacobian matrix of the model equation. The Gear type procedure is used to integrate a model equation and its coupled auxiliary sensitivity coefficient equations. The FORTRAN subroutines of the model equation, the sensitivity coefficient equations, and their Jacobian analytical expressions are generated automatically from a chemical mechanism. The kinetic representation for the model equation and its sensitivity coefficient equations, and their Jacobian matrix is presented. Various FORTRAN subroutines in packages, such as SLODE, modified MA28, Gear package, with which the program runs in conjunction are recommended. The photo\|oxidation of dimethyl disulfide is used for illustration.

Numerical study of CNG engine combustion using CFD with detailed chemical kinetics

A three dimensional model which considers the effects of turbulence and detailed chemi cal kinetics is built to simulate the combustion process of engine fueled by compressed nature gas （CNG）. The model is accomplished by integrating CFD software KIVA3V and chemical kinetic soft- ware CHEMKINII. Meanwhile, a turbulence combustion model which is suitable for describing the reaction rate under the coupled simulation is developed to balance the effects of turbulence and de tailed chemical kinetics. To reduce the computation time, subsequent development of the simulation code is realized, which enables the simulation code to have the function of parallel computing and run on parallel computing facility based on message passing interface （MPI）. The coupled software is used to simulate the combustion process of spark ignition CNG engine. The results show that sim ulation data have a good consistency with experimental results and parallel computing has good effi ciency and accelerate ratio.

ChemNODE: A neural ordinary differential equations framework for efficient chemical kinetic solvers

Solving for detailed chemical kinetics remains one of the major bottlenecks for computational fluid dynamics simulations of reacting flows using a finite-rate-chemistry approach.This has motivated the use of neural networks to predict stiff chemical source terms as functions of the thermochemical state of the combustion system.However,due to the nonlinearities and multi-scale nature of combustion,the predicted solution often diverges from the true solution when these machine learning models are coupled with a computational fluid dynamics solver.This is because these approaches minimize the error during training without guaranteeing successful integration with ordinary differential equation solvers.In the present work,a novel neural ordinary differential equations approach to modeling chemical kinetics,termed as ChemNODE,is developed.In this machine learning framework,the chemical source terms predicted by the neural networks are integrated during training,and by computing the required derivatives,the neural network weights are adjusted accordingly to minimize the difference between the predicted and ground-truth solution.A proof-of-concept study is performed with ChemNODE for homogeneous autoignition of hydrogen-air mixture over a range of composition and thermodynamic conditions.It is shown that ChemNODE accurately captures the chemical kinetic behavior and reproduces the results obtained using the detailed kinetic mechanism at a fraction of the computational cost.

Nanotechnology combining photoacoustic kinetics and chemical kinetics for thrombosis diagnosis and treatment

Thrombotic disease is a major problem that endangers human health. At present, MRI and CT are commonly used clinically to diagnose thrombosis, and thrombolytic drugs are used for treatment), but the diagnosis time is lagging, the utilization of drugs is low, and the resulting systemic toxicity problems such as side effects lead to poor treatment effects. Nanotechnology combining photoacoustic dynamics and chemical dynamics has shown great application value in tumor targeting, diagnosis, detection and treatment. It has also become a new direction in the diagnosis and treatment of thrombotic diseases, and has created new applications in the field of nanomaterials. This review summarizes the new progress of this combination in the diagnosis and treatment of thrombotic diseases according to the differences in the construction of the nanotherapy system, at the same time, we put forward some new problems and prospects for the integration of thrombosis diagnosis and treatment.

Comparison of Invariant Manifolds for Model Reduction in Chemical Kinetics

A modern approach to model reduction in chemical kinetics is often based on the notion of slow invariant manifold.The goal of this paper is to give a comparison of various methods of construction of slow invariant manifolds using a simple Michaelis-Menten catalytic reaction.We explore a recently introduced Method of Invariant Grids(MIG)for iteratively solving the invariance equation.Various initial approximations for the grid are considered such as Quasi Equilibrium Manifold,Spectral Quasi Equilibrium Manifold,Intrinsic Low Dimensional Manifold and Symmetric Entropic Intrinsic Low Dimensional Manifold.Slow invariant manifold was also computed using the Computational Singular Perturbation(CSP)method.A comparison between MIG and CSP is also reported.

EFFECTIVE SOLUTION METHOD OF CHEMICAL REACTION KINETICS WITH DIFFUSE

The time integration method with four-order accuracy, self-starting and implicit for the diffuse chemical reaction kinetics equation or the transient instantaneous temperature filed equation was presented. The examples show that both accuracy and stability are better than Runge-Kutta method with four-order. The coefficients of the equation are stored with sparse matrix pattern, so an algorithm is presented which combines a compact storage scheme with reduced computation cost. The computation of the competitive and consecutive reaction in the rotating packed bed, taken as examples, shows that the method is effective.

The Impact of Aqueous Medium on Gas Yields and Kinetic Behaviors of Hydrogen Isotope Fractionation during Organic Matter Thermal Degradation

In order to recognize the impact of aqueous medium on gas yields and the kinetic behaviors of hydrogen isotope fractionation during organic matter thermal degradation, the gold tube apparatus was used to conduct thermal simulation experiments by mixing the nC18 with the water of different properties and proportions. The yields of natural gas components, the relation among hydrogen isotope composition of each component and the experimental temperatures vs. heating rates have been obtained, and the results indicate that under the higher temperature conditions, the hydrous experiment has obvious impact on gas yields, such as when more water is added, higher amounts of hydrocarbon gas and H2 are yielded, and the existence of water obviously prolongs the temperature interval with the existence of heavy hydrocarbon gas. It also shows that the hydrogen isotope of hydrocarbon gas generated by the hydrous experiment is obviously lighter than that generated by the anhydrous experiment, and with the increasing amount of added water, the δD value of hydrocarbon gas gradually decreases. Compared with gas yields, the variation of δD value is more sensitive to aqueous medium in the thermal simulation experiment. However, compared with the amount of the added water, the aqueous medium property has smaller impact on the gas yields, which still shows the inherit effect on hydrogen isotope composition of aqueous medium. Through the model simulation and the isotope fractionation behavior analysis, it is validated that the hydrogen isotope fractionation process can be well described by the chemical kinetic model. The difference of reaction fraction of normal methane and D-containing methane is large, corresponding to the same activation energy. The content of normal methane is obviously higher in the part with lower activation energy, while the content of D-containing methane is higher in the part with higher activation energy. Therefore, it will result in larger hydrogen isotope fractionation amplitude, and the δD values will be more sensitive to the variation of maturity. Meanwhile, the average activation energy of methane generation from nC18 in the hydrous experiment is higher than that in the anhydrous experiment, and the greater amount of added water, the larger the average activation energy of methane generation reaction. This has laid foundation for its exploratory application in the study of gas reservoir forming history and the gassource correlation, which indicates the research and application prospects in this orientation.

Kinetics and fractionation of hydrogen isotopes during gas formation from representative functional groups

A gold tube simulation device was used to study the cleavage of representative compounds into gas.The goal of this study is to investigate hydrogen isotope composition change of gaseous hydrocarbons during maturity.Gas chromatography and isotopic analyses were conducted to determine how the yield of natural gas components and their hydrogen isotopic composition were related to experimental temperature and heating rate.A chemical kinetic model for the generation of each component of the natural gas and for the hydrogen isotopic fractionation was established and calibrated based on the results.Results indicate that the hydrogen isotopic fractionation during the evolution of various gas-forming organic materials can be satisfactorily described by chemical kinetic models.During regular methane generation,the reactions at low-activation-energy region had a greater contribution than the high-activation-energy region.While the reactions with high-activation-energy region had greater contribution of deuterium-rich methane.Compared with carbon isotope fractionation,this results in a greater hydrogen isotopic fractionation,which is more sensitive to changes in maturity.This study lays a foundation for further investigations of genesis and maturity of natural gas provided by hydrogen isotopic fractionation.It also provides fundamental knowledge for investigating the filling history of natural gas reservoir and for identifying.

Theoretical estimation of sonochemical yield in bubble cluster in acoustic field

In order to learn more about the physical phenomena occurring in cloud cavitation,the nonlinear dynamics of a spherical cluster of cavitation bubbles and cavitation bubbles in cluster in an acoustic field excited by a square pressure wave are numerically investigated by considering viscosity,surface tension,and the weak compressibility of the liquid.The theoretical prediction of the yield of oxidants produced inside bubbles during the strong collapse stage of cavitation bubbles is also investigated.The effects of acoustic frequency,acoustic pressure amplitude,and the number of bubbles in cluster on bubble temperature and the quantity of oxidants produced inside bubbles are analyzed.The results show that the change of acoustic frequency,acoustic pressure amplitude,and the number of bubbles in cluster have an effect not only on temperature and the quantity of oxidants inside the bubble,but also on the degradation types of pollutants,which provides a guidance in improving the sonochemical degradation of organic pollutants.

Chemical Analysis of NO_x Removal Under Different Reduced Electric Fields

This work presents a chemical kinetic analysis of different species involved in nitrogen-oxygen mixed gas induced by stationary corona discharge at room temperature and atmospheric pressure.This study takes into account twenty different chemical species participating in one hundred and seventy selected chemical reactions.The reaction rate coefficients are taken from the literature,and the density is analyzed by the continuity equation without the diffusion term.A large number of investigations considered the removal of NOx showing the effects of N,O and O3 radicals.The aim of the present simulation is to complete these studies by analysing various plasma species under different reduced electric fields in the range of 100-200 Td（1 Td=10-21 V·m^2）.In particular,we analyze the time evolution of depopulation（10^-9-10^-3s）of NOx.We have found that the depopulation rate of NO and NO2 is substantially affected by the rise of reduced electric field as it grows from 100 Td to 200 Td.This allows us to ascertain the important role played by the reduced electric field.

Reaction mechanism and kinetics of pressurized pyrolysis of Chinese oil shale in the presence of water

A study of reaction mechanisms and chemical kinetics of pressurized pyrolysis of Chinese Liushuhe oil shale in the presence of water were conducted using an autoclave for simulating and modeling in-situ underground thermal degradation.It was found that the oil shale was first pyrolyzed to form pyrobitumen,shale oil,shale gas and residue,then the pyrobitumen was further pyrolyzed to form more shale oil,shale gas,and residue.It means that there are two consecutive and parallel reactions.With increasing temperature,the pyrobitumen yield,as intermediate,first reached a maximum,then decreased to approximately zero.The kinetics results show that both these reactions are first order.The activation energy of pyrobitumen formation from oil shale is lower than that of shale oil formation from pyrobitumen.

Macroscopic,thermodynamic,kinetic and microscopic study of nitric acid pickling of Elektron 21(EV31A)magnesium alloy

The study of pickling of the EL21T6 substrate in a nitric acid bath firstly provided knowledge of the influence of the different experimental parameters(concentration of acid,temperature and stirring of the solution)in relation to the etching rate.This experimental part led to the choice of standard pickling(T_(bath)=25℃,moderate stirring(250 rpm),[HNO_(3)]=1.20 mol/L,duration of 2 min)so as to obtain constant removal of material,even after several uses of the pickling bath.SEM observations also confirmed that in these operating conditions,pickling concerns both the grains of the matrix and the precipitates of type Mg3(Nd,Gd),leading to uniform removal of material from the surface.Working from a number of assumptions,thermodynamic and chemical kinetic studies then allowed a pickling mechanism to be proposed and led to obtaining values for the corresponding kinetic parameters(order of reaction,constant of mean rate,activation energy)to be obtained.

Mechanism and Kinetics Analysis of NO/SO_2/N_2/O_2 Dissociation Reactions in Non-Thermal Plasma

The kinetics mechanism of the dissociation reactions in a NO/SO2/N2/O2 system was investigated in consideration of energetic electrons＇ impacts on a non-thermal plasma. A model was derived from the Boltzmann equation and molecule collision theory to predict the dissociation reaction rate coefficients. Upon comparison with available literature, the model was confirmed to be acceptably accurate in general. Several reaction rate coefficients of the NO/SO2/N2/O2 dissociation system were derived according to the Arrhenius formula. The activation energies of each plasma reaction were calculated by quantum chemistry methods. The relation between the dissociation reaction rate coefficient and electron temperature was established to describe the importance of each reaction and to predict relevant processes of gaseous chemical reactions. The sensitivity of the mechanism of NO/SO2/N2/O2 dissociation reaction in a non-thermal plasma was also analysed.

Influence of CH_3SiCl_3 Consistency on Growth Process of SiC Film by Kinetic Monte Carlo Method

CH3SiCl3 （MTS）-H2-Ar system has been applied to prepare SiC film with chemical vapor deposition （CVD） method in this paper. For three facets of SiC film, some significant influence on growth rate, surface roughness, thickness and relative density brought by MTS consistency has been mainly discussed with kinetic monte carlo （KMC） method. The simulation results show that there is a certain scale for mol ratio of H2 to MTS （H2/MTS） with different deposition temperature. When MTS consistency increases, growth rate and surface roughness of three facets all increase, which manifests approximate linearity relationship. Thickness of three facets also increases while increasing trend of three facets thickness is different obviously. Although relative density of three facets all increases, increasing trend shows a little difference with MTS consistency increasing.

Electrical Response of Silanization of Rubber Mixtures

There are a number of experimental methods aimed at the investigation of structural transformations. These methods differ from each other by a spectrum of quantitative indicators and their application is limited by the nature of investigated structures and processes. In a sense, it is also possible to consider the silanization of rubber mixtures as a structural transformation. Experimental observation of transformations of disordered rubber mixtures type structures can be quite difficult. The contribution deals with the theoretical principles of experimental methodology oriented on the investigation of silanization of rubber mixtures. We analyze the electrical response of rubber mixtures silanization. Our attention is focused on the modeling of a possible electrical response of a chemical reaction in a system consisting of several components. The results of the model are compared with experimental data measured during the silanization reaction in rubber mixtures.

Planarization mechanism of alkaline copper CMP slurry based on chemical mechanical kinetics

The planarization mechanism of alkaline copper slurry is studied in the chemical mechanical polishing （CMP） process from the perspective of chemical mechanical kinetics.Different from the international dominant acidic copper slurry,the copper slurry used in this research adopted the way of alkaline technology based on complexation. According to the passivation property of copper in alkaline conditions,the protection of copper film at the concave position on a copper pattern wafer surface can be achieved without the corrosion inhibitors such as benzotriazole（BTA）,by which the problems caused by BTA can be avoided.Through the experiments and theories research,the chemical mechanical kinetics theory of copper removal in alkaline CMP conditions was proposed. Based on the chemical mechanical kinetics theory,the planarization mechanism of alkaline copper slurry was established. In alkaline CMP conditions,the complexation reaction between chelating agent and copper ions needs to break through the reaction barrier.The kinetic energy at the concave position should be lower than the complexation reaction barrier,which is the key to achieve planarization.

Adiabatic Decomposition of Two Kinds of Organic Peroxides by Accelerating Rate Calorimeter

The accelerating rate calorimeter was applied to study the thermal hazard of two kinds of organic peroxides, i.e. methyl ethyl ketone peroxide (MEKPO) and benzoyl peroxide (BPO). And their thermal decomposition characteristics were discussed. Meanwhile, thermal decomposition characteristics of MEKPO and BPO vvere compared. The result indicated that MEKPO is more sensitive to thermal effect than BPO. While once the thermal decomposition takes place. BPO will be more hazardous than MEKPO due to its serious pressure effect. Thermal kinetic analysis of these two kinds of organic peroxides was also taken, and the kinetic parameters for them were calculated. The study of thermal decomposition of MEKPO solution with different initial concentrations indicated that, the lower concentration MEKPO solution is, the higher onset temperature will be. And with the addition of organic solvent, it becomes more difficult for MEKPO to reach a thermal decomposition. Therefore, its thermal hazard is reduced.

Influences of Catalytic Combustion on the Ignition Timing and Emissions of HCCI Engines

The combustion processes of homogeneous charge compression ignition （HCCI） engines whose piston surfaces have been coated with catalyst （rhodium or platinum） were numerically investigated. A singlezone model and a multi-zone model were developed. The effects of catalytic combustion on the ignition timing of the HCCI engine were analyzed through the single-zone model. The results showed that the ignition timing of the HCCI engine was advanced by the catalysis. The effects of catalytic combustion on HC, CO and NOx emissions of the HCCI engine were analyzed through the multi-zone model. The results showed that the emissions of HC and CO （using platinum （Pt） as catalyst） were decreased, while the emissions of NOx were elevated by catalytic combustion. Compared with catalyst Pt, the HC emissions were lower with catalyst rhodium （Rh） on the piston surface, but the emissions of NOx and CO were higher.

A HYDRO-MECHANICAL-CHEMICAL COUPLING MODEL FOR GEOMATERIAL WITH BOTH MECHANICAL AND CHEMICAL DAMAGES CONSIDERED

A general framework of hydro-mechanical-chemical coupling model is proposed for geomaterial subjected to the dual effects of mechanical loading and chemical degradation. Mechanical damage due to microcracks in solid matrix and chemical damage induced by the increase of porosity due to dissolution of matrix minerals as well as their interactions are considered. A special model is proposed for sandstone. The reaction rate is formulated within the framework of mineral reaction kinetics and can thus take into account different dissolution mechanisms of three main mineral compositions under different pH values. The increase of porosity is physically defined by the dissolution of mineral composition and the chemical damage is related to the increase of porosity. The mechanical behavior is characterized by unified plastic damage and viscoplastic damage modeling. The effective stress is used for describing the effect of pore pressure. The elastic parameters and plastic evolution as well as viscoplastic evolution are dependent on chemical damage. The advection, which is coupled with mechanical damage and chemical damage, is considered as the dominant mechanism of mass transfer. The application of model proposed is from decoupled experiments to fully coupled experiment. The model offers a convenient approach to describing the hydro-mechanical-chemical coupled behavior of geomaterial.