Papers by Keyword: Kinetic Model

Abstract: Experimental studies of some physical properties of paulownia wood and identifies differences in comparison with other popular species are presented. In particular, the regularities of hydration and dehydration processes were investigated. Based on the results obtained, reliable data on the hygroscopic properties of paulownia were obtained for the first time. It was found that the hydration rapidity of paulownia (V_pl = 1.493) exceeds the similar rate of pine (V_pn = 1.1313) at a temperature of 20 °C. Changing the temperature of the liquid in which the wood is modified leads to an increase in the impregnation rapidity and, therefore, increases the productivity of the process. The dehydration rapidity of both species is almost the same (k = –0.002), which allows them to be dried simultaneously in the same chamber, optimizing production logistics. The dependence of liquid absorption on concentration was investigated. It has been found that a higher concentration outside causes a greater diffusion flux into the sample, while a higher concentration inside leads to a decrease in the sample weight. During the hydration stage, the weight of paulownia samples increased by 4 times, and pine samples – by 2.5 times. A two-stage kinetic model of wood hydration has been developed, which adequately describes the dynamics of the process. The resulting S-shaped curve clearly characterizes the features of the kinetics processes with saturation. Verification showed a high correlation – 85 % – for hydration and over 90 % for dehydration, which allows for accurate modeling and prediction of the technological processes of wood impregnation and drying.

Abstract: The article is devoted to mathematical modeling and fuzzy logic in controlling the process of adsorption purification of isobutane and isobutylene from impurities. The article also conducted research on the production of high-purity isobutane and isobutylene from the isobutane-isobutylene fraction of pyrolysis gas. A method has been developed for increasing the purity of isobutane and isobutylene fractions isolated from pyrolysis gas using sulfuric acid. It is proposed to introduce adsorption units into the plant technological scheme for separating the hydrocarbons isobutane and isobutylene from the C4 fraction of pyrogas, with the help of which it has been proven to obtain isobutane and isobutylene hydrocarbons of high purity up to 99.9%. The processes of selecting adsorbents for the additional purification of the isobutane fraction from isobutylene impurities were also studied and activated carbon of the AP-3 grade was selected, and for the additional purification of the isobutylene fraction from impurities of normal butylene’s, CaA zeolite was selected. The main reactions have been studied and a mathematical model of the processes for producing pure isobutylene and isobutane has been developed, taking into account recycling; also, artificial intelligence (AI) has been used when selecting adsorbents to optimize the processes of purifying the pyrolysis gas fraction of isobutane and isobutylene from impurities.

Abstract: The utilized adsorption kinetic models, i.e., pseudo-zero order, pseudo-first-order, pseudo-second order, intraparticle diffusion, Bangham’s pore diffusion, liquid film diffusion, modified Freundlich and Elovich models have been cultivated the hexavalent chromium adsorption process. A high correlation coefficient (R²) and a small residual root mean square error (RMSE) and Chi-square (χ²) can be depicted in the pseudo-first order for the kinetic adsorption process of hexavalent chromium adsorption on the activated mangosteen shell with potassium hydroxide and carbonized at 400 °C for 2 h as a biochar adsorbent which has a specific surface area of 164 m²/g.

Abstract: This study discusses the development of Indonesian natural zeolite and agricultural waste i.e bagasse ash and rice husk ash as natural adsorbents. These materials were used as an adsorbent for methyl orange and methylene blue adsorption for isotherm and kinetic study. Adsorption kinetic models for methyl orange and methylene blue with all adsorbents were a pseudo-second-order except methyl orange adsorption with bagasse ash adsorbent (MA) that followed pseudo-first-order. Isotherm models for all adsorption experiments were Langmuir type except methyl orange adsorption using rice husk adsorbent (MS) that followed Freundlich type.

Abstract: The removal of magnesium from garnierite in Yuanjiang area of Yunnan was performed by carbothermal reduction in vacuum. The effects of reduction temperature and reduction time on the removal rate of magnesium were investigated. The kinetics of the removal of magnesium by carbothermal reduction in vacuum was studied. The thermodynamic calculation results show that it is feasible to remove magnesium from garnierite by carbothermal reduction in vacuum. The experimental results show that the removal rate of magnesium in garnierite can reach 93.23% under the conditions of 1823K for 120min. The reduction process conforms to the chemical reaction kinetics model, which indicated that the reduction process is controlled by chemical reaction and whose expression is 1-(1-α)^1/3=(-22850.1/T+2.6296) t, the apparent activation energy (Ea) and the pre-exponential factor (A) are 189.97 kJ/mol and 13.87 s^-1, respectively. The results of XRD and SEM analysis show that the condensate obtained by carbothermal reduction in vacuum of the garnierite is magnesium, which is mainly obtained by the reduction reaction between magnesium silicate produced by the decomposition of serpentine in minerals and coal. At the same time, it is proved that it is feasible to directly extract magnesium metal from the garnierite.

Abstract: In view of the constant search for new sources of renewable energy, the particulate agro-industrial waste reuse emerges as an advantageous alternative. However, despite the advantages of using the biomass as an energy source, there is still strong resistance as the large-scale replacement of petroleum products due to the lack of scientifically proven efficient conversion technologies. In this context, the pyrolysis is presented as one of the most widely used thermal decomposition processes. The knowledge of aspects of chemical kinetics, thermodynamics these will, heat and mass transfer, are so important, since influence the quality of the product. This paper presents a kinetic study of slow pyrolysis of coffee grounds waste from dynamic thermogravimetric experiments (TG), using different powder catalysts. The primary thermal decomposition was described by the one-step reaction model, which considers a single global reaction. The kinetic parameters were estimated using nonlinear regression and the differential evolution method. The coffee ground waste was dried at 105°C for 24 hours. The sample in nature was analyzed at different heating rates, being 10, 15, 20, 30 and 50 K/min. In the catalytic pyrolysis, about 5% (w/w) of catalyst were added to the sample, at a heating rate of 30 K/min. The results show that the one-step model does not accurately represent the data of weight loss (TG) and its derivative (DTG), but can do an estimative of the activation energy reaction, and can show the differences caused by the catalysts. Although no one can say anything about the products formed with the addition of the catalyst, it would be necessary to micro-pyrolysis analysis, we can say the influence of the catalyst in the samples, based on the data obtained in thermogravimetric tests.

Abstract: This work studied on the kinetics of Vitamin C extraction from banana peel at different solvent/solid concentration and temperature. Musa Acuminata was ground into smaller sizes before contacted with methanol as a solvent in an ultrasonic bath. To study the effect of solvent/solid ratio, 4.5, 5.0 and 10.0 ml/g ratio were used for the extraction at fixed temperature. Then, the temperature was varied with the heating element available in the ultrasonic bath at 30, 45 and 60 °C, to study the effect of temperature on the extraction kinetics. It was found that high solvent/solid ratio (10 ml/g) provides more solute-solvent contact and prevents the extracted Vitamin C from coming into contact with the air. Besides, higher temperature (60 °C) contributes sufficient kinetic energy for Vitamin C distribution in the solvent which is important to prevent degradation with air. The best fitted kinetic model for Vitamin C extraction from Musa Acuminata is Ana et al. (2007) with equilibrium concentration of 0.05 g/L and 0.40 g/L.hr extraction rate.

Abstract: Photodegradation of 5-Methoxypsoralen (5-MOP), 4', 5'-dimethyl-3,4-cyclogeksilpsoralen (KC5) and 4'-methyl-3,4 cycloheptylpsoralen (KC4) has been carried out in an XeBr exilamps, both in the presence of H2O2, and a kinetic model, which explains the dependence of the pseudo-first order kinetic parameter on the substrate concentration and other operational variables, has been developed. In the development of the model, mass transfer of 5-MOP, KC5 and KC4from the bulk solution to the wall of the vessel was assumed as the step determining the rate of the photodegradation process, which successfully explains some singularities observed in the experimental results.By fitting the experimental data to the model, a detailed study of the influence of all operational variables on the pseudo-first order kinetic parameter has been done, in good agreement with the model hypotheses.

Abstract: Although the wide applications of the fractional order of dierential equations hasbeen reported in the physics, astronomy, and bioengineering elds, little attention has beenpaid to the fractional kinetic models in the literature. In this research, we are conned with theapplication of Jacobi polynomials for solving fractional order of l dierential equation arising inchemical reaction model into the Palm oil in the sense of fuzzy context. The results demonstratethe capability of the method which can be a reliable numerical technique to be utilized in thesimilar reaction models.

Abstract: In this paper, the kinetics of precipitate growth in metastable binary solid solutions is analyzed considering two mechanisms: (i) diffusion of the one component from the bulk of composition matrix and its incorporation in the precipitate, and (ii) emission and outdiffusion of the second component from the interface of precipitate with surrounding matrix. A kinetic model is proposed that enables a description of these both mechanisms in a unique way. Using this model, the mechanism of oxygen emission and outdiffusion from the interface of Si precipitates with the silicon oxide surrounding is confirmed to determine the phase separation kinetics upon high temperature annealing nonstoichiometric silicon oxide films.