Shrinking Core Model Research Articles

On the Kinetic Mechanisms of the Reduction and Oxidation Reactions of Iron Oxide/Iron Pellets for a Hydrogen Storage Process

This work aims at investigating the kinetic mechanisms of the reduction/oxidation (redox) reactions of iron oxide/iron pellets under different operating conditions. The reaction principle is the basis of a thermochemical hydrogen storage system. To simulate the charging phase, a single pellet consisting of iron oxide (90% Fe2O3, 10% stabilising cement) is reduced with different hydrogen (H2) concentrations at temperatures between 600 and 800 °C. The discharge phase is initiated by the oxidation of the previously reduced pellet by water vapour (H2O) at different concentrations in the same temperature range. In both reactions, nitrogen (N2) is used as a carrier gas. The redox reactions have been experimentally measured in a thermogravimetric analyser (TGA) at a flow rate of 250 mL/min. An extensive literature review has been conducted on the existing reactions’ kinetic mechanisms along with their applicability to describe the obtained results. It turned out that the measured kinetic results can be excellently described with the so-called shrinking core model. Using the geometrical contracting sphere reaction mechanism model, the concentration- and temperature-dependent reduction and oxidation rates can be reproduced with a maximum deviation of less than 5%. In contrast to the reduction process, the temperature has a smaller effect on the oxidation reaction kinetics, which is attributed to 71% less activation energy (Ea,Re=56.9 kJ/mol versus Ea,Ox=16.0 kJ/mol). The concentration of the reacting gas showed, however, an opposite trend: namely, to have an almost twofold impact on the oxidation reaction rate constant compared to the reduction rate constant.

Sulfonation of 1,4-diaminoanthraquinone leuco by chlorosulfonic acid: Kinetics and process intensification

The work herein employed a rotating packed bed (RPB) to intensify the sulfonation process of 1,4-diaminoanthraquinone leuco (DL) in an attempt to improve the yield of the product 1,4-diaminoanthraquinone-2-sulfonic acid (DSA). First, the effects of operating conditions in a stirred tank reactor (STR), including stirring speed, chlorosulfonic acid/DL molar ratio (η), solvent/DL mass ratio (ζ), reaction temperature and dropping speed of chlorosulfonic acid, on the yield of DSA were investigated. The yield of DSA can reach 87.34% under the optimal operating conditions: stirring speed of 500 r·min−1, η of 4.5, ζ of 7, reaction temperature of 150 °C, dropping speed of 0.61 ml·min−1. In addition, the kinetics of the sulfonation process via the shrinking core model revealed that the reaction is controlled by diffusion via a product layer under the reaction temperature of 140 °C. Furthermore, the RPB was employed to intensify the mass transfer between liquid and solid phases during the sulfonation reaction process. The results showed that the DSA yield of 92.69% obtained by RPB was 5.35% higher than that by STR, indicating that RPB can significantly intensify the mass transfer in the liquid–solid phase sulfonation reaction process.

Comparative evaluation of chemical and bio techniques for uranium leaching from low grade sandstone rock sample, Abu Thor, southwestern Sinai, Egypt

Ferruginous sandstone considered as a one of the economically significant uranium mineralized areas in the southwestern part of the Sinai that located at the lower member of Um Bogma Formation in Abu Thor area. The studied sample was characterized geologically as a sandstone rock contain 450 mg/kg of uranium. This work is aimed to compare between eco-friendly bioleaching and conventional leaching processe. The uranium bioleaching efficiency achieved 80% by using a native fungal strain; Aspergillus nidulans as a green technology with the optimimum conditions as; 3 pH value, 3% pulp density, 7 days incubation period, and 30 °C incubation temperatures. Whereas the traditional technique using alkaline and sulphuric acid leaching attained 68.5% and 95% respectively at the best condition. Finally, the shrinking core model was represented the layer diffusion process by acquiring apparent activation energy 18.28 and 16.82 kJ/mol for carbonate and sulphuric acid leaching, respectively.

Nickel leaching kinetics of high-grade nickel matte with sulfuric acid under atmospheric pressure

The nickel leaching kinetics of high-grade nickel matte with sulfuric acid under atmospheric pressure were studied. The effects of stirring speed, high-grade nickel matte particle size, reaction temperature and sulfuric acid concentration on the percentage of nickel dissolved were investigated. In the leaching process, the Ni3S2 in the dense high-grade nickel matte is decomposed which conforms to the shrinking core model. The results show that the unreacted Cu2S solid film has little effect on the reaction product diffusion, while the reaction temperature and particle size of the high-grade nickel matte have significant effects on the leaching process. The activation energy of the decomposition reaction is 39 kJ mol−1 according to the Arrhenius equation and the reaction order is 0.24 with respect to acid concentration. The corresponding kinetic expression for the leaching process is 1 − (1 − x)1/3 = 1.32 × 103c0.235r0−1exp(−39,034/RT)·t which indicates that the process is controlled by the interfacial chemical reaction.

Recovery of oils and antioxidants from olive stones

The olive oil industry generates enormous amounts of olive stones each year, which have the potential to be used as a biofuel but have high oil content, which negatively impacts the combustion process. In addition, olive stones contain high-value antioxidants, and their exploitation can provide additional revenues for the biofuel industry.In this work, we report the effect of different extraction solvents on the extraction of antioxidants and their activity. In addition, in vitro gastrointestinal digestion was used to evaluate the content and antioxidant activity of the olive stone extracts after gastrointestinal digestion. The extracts obtained by aqueous ethanol solvent (50% vol) exhibited the highest antioxidant activity with the DPPH IC50 of 1.27 mg mL−1 and ferric reducing antioxidant power (FRAP) of 6.33 mg AAE g−1. After in vitro digestion composed of gastric and intestinal processes, the antioxidant activity of olive stones decreased: DPPH IC50 value increased three times (a higher value of IC50 indicates lower antioxidant activity) and FRAP decreased almost five times with respect to the values obtained for original extracts.Furthermore, both phenomenological and shrinking core models were used to fit experimental oil extraction kinetics data and showed good agreement. Thermodynamic analysis showed that the extraction process is endothermic and irreversible while spontaneous and thermodynamically favourable for all conditions except for oil extraction from olive stones of 3.10 mm particle size at 20 °C. The calculated value for temperature coefficient is in good agreement with the previously reported values for the oil extraction from similar biomass.

Iron Extraction from South African Ilmenite Concentrate Leaching by Hydrochloric Acid (HCl) in the Presence of Reductant (Metallic Fe) and Additive (MgSO4)

The high content of iron in ilmenite ore poses a great challenge, particularly in the synthesis of titanium-containing products due to high susceptibility of iron (Fe) to corrosion. Direct leaching of ilmenite ore in hydrochloric acid (HCl) encouraging Fe dissolution was investigated. The influence of variable parameters, the use of additives, and the addition of metallic iron powder were studied to establish the optimum leaching parameters. The results showed that ilmenite with the particle size distribution of +150 µm yielded better efficiencies when leaching was performed with an acid concentration of 7.5 M and a solid-to-acid ratio of 1:10 at 90 °C. An agitation speed of 450 rpm yielded a superior Fe extraction of about 92.32% and a 2.40% titanium (Ti) loss. The addition of both metallic Fe and the MgSO4 additive significantly enhanced Fe dissolution and decreased Ti recovery in a leach solution. It was found that leaching under optimum conditions produced a solid residue with 1.37% Fe impurity while 98.63% was extracted. The leached residue was comprised of 91.4% TiO2 rutile phase and contained a high content of the ilmenite FeTiO3 (4.37%) and SiO2 (2.23%) impurities, while Al2O3, MgO, MnO2, CaO, V2O5, MnO2, and Cr2O3 were below 0.13%. The high TiO2 content in the leached residue makes it suitable for use as feed in the production of synthetic rutile. The leaching kinetics of Fe dissolution was found to conform to the shrinking core model, where diffusion through the product layer is rate controlling. The calculated activation energy according to the Arrhenius equation was 19.13 kJ/mol.

Metal sulfate-catalyzed methanolysis of cellulose at high solid loadings: Heterogeneous degradation kinetics and levulinate synthesis

Increasing efforts have been devoted to the production of bio-based chemicals from high solid content of renewable biomass to pursue optimal process efficiency and economics. In this study, the preparation of methyl levulinate (ML) by metal sulfate-catalyzed methanolysis from high solid content of cellulose was investigated. When the cellulose loading was 15%, 38.67% of ML yield can be obtained under the optimum reaction conditions. Al2(SO4)3 can be reused more than five times while maintaining high activity in the process. The characterization of cellulose particles confirmed that cellulose particles shrunk over the reaction time. The heterogeneous degradation kinetics of high solid content of cellulose in methanol could be explained by a shrinking core model. High solid loadings led to a decrease of the reaction rate constants of methanolysis. Using cellulose with a small particle size can improve the methanolysis reaction rate. The study also proposed comprehensive reaction pathways for ML production from high solid content of cellulose. To elucidate the methanolysis mechanism, an assessment of density functional theories for the calculation of glucose methanolysis at the molecular level is presented. All these results can inspire the development of ML synthesis technology through methanolysis from renewable biomass with high solid loadings.

Kinetics of Low-Grade Scheelite Leaching with a Mixture of Sodium Phosphate and Sodium Fluoride

The current technology of leaching low-grade scheelite with sodium hydroxide or sodium carbonate has the disadvantages of large leaching reagent dosage and low leaching efficiency of tungsten. In order to extract scheelite efficiently, the kinetics of low-grade scheelite leaching with a mixture of sodium phosphate and sodium fluoride was investigated. In this study, the effects of temperature, phosphate concentration, and fluoride ion concentration on the leaching rate of tungsten were investigated. Our results showed that the leaching rate of tungsten was greatly influenced by the temperature and less affected by the concentration of phosphate and fluorine ions. The leaching process was controlled by a chemical reaction with an apparent activation energy value of 51 ± 0.2 kJ/mol. The apparent reaction orders with respect to phosphate and fluorine ions were 0.49 and 0.11, respectively. The reaction product calcium fluorophosphate was a loose, rod-like crystal, which would not tightly wrap on the surface of scheelite to prevent the diffusion process. The leaching kinetics of low-grade scheelite was in accordance with the shrinking core model, and the corresponding kinetic equation was also established.

Quantitative Leaching of Awo Mica Ore in Acetic Acid Solutions

Mica is mined and processed throughout the world and used as functional filler in many applications, such as in joint compound, electrical insulation, and plastics. The single most important feature of mica is high aspect ratio, the ratio of width to thickness. High aspect ratio mica filler is desirable in specialty applications, such as in automotive plastics, electrical industry. Considering these applications, Awo mica was quantitatively leached using acetic acid with focus on the determination of elemental composition of the ore using XRF technique, the determination of mineralogical purity of the ore using XRD, SEM and EDS techniques, the determination of the dissolution rate using acetic acid so as to predict the optimum conditions for the beneficiation of the ore for industrial applications and lastly, to investigate the potential for developing flake muscovite deposits in Southwestern Nigeria. Various parameters like effect of leachant concentration, temperature and the particle size have been investigated. Increase in leachant concentration and temperature brings about increase in dissolution rate and decrease in particle size increases the dissolution rate. The calculated reaction order and Activation energy (Ea) was 0.9437 and 21 kJ/mol respectively. The shrinking core model employed showed diffusion-controlled mechanism as the rate determining step for the dissolution process. Detailed ore characterization, for example the XRF for the elemental analysis shows that SiO2 is the most abundant compound (58.30%). It also contains other major compound like Al203 (18.70%) with the other detected compounds found to occur in minor to trace levels (< 1%). The residual product was quantitatively characterized by XRD and SEM instrumentations.

Kinetics Study of Alumina Leaching from Ogbunike Clay Using Hydrochloric Acid

The kinetics study of alumina leaching from ogbunike clay was carried out using a solution of hydrochloric acid (HCl) for alumina dissolution. Variations in process parameters such as calcination temperature, leaching temperature, acid concentration, particle size, and solid-to-liquid ratio were considered for the leaching of alumina. The shrinking core model was used to analyze the experimental data. Alumina removal is feasible with 24.035% extractable alumina, and this can improve the economic value of ogbunike clay, which can be an alternative raw material in Nigeria’s aluminum industries. According to the data the dissolution rate increases with increasing calcination temperature, leaching temperature and acid concentration and decreasing particle size and solid-to-liquid ratio. The statistical and graphical analysis revealed that the dissolution followed the product layer diffusion-controlled semi-empirical kinetic model. The activation energy was calculated to be 18.36 kJ/mol for HCl. The optimum conditions for the dissolution of the alumina in HCI include activation temperature of 700 ⁰C for 60 minutes, leaching temperature of 90 ⁰C, HCl concentration of 3 M, particle size of 75 µm, and the solid-liquid ratio of 0.2 g/ml yielding the alumina dissolution rate of 84.72%. The kinetic data can be used to construct large-scale manufacturing equipment.

Characterization and kinetics of alumina leaching from calcined Akpugo kaolinite for potential aluminum recovery

The kinetics study on alumina leaching from calcined Akpugo kaolinite was considered in this study. The shrinking core model and other relevant kinetic models were used for kinetic analysis of the leaching process. The leaching rate increases with increase in acid concentration, temperature, and stirring rate from 45.0 to 81.5% for acid concentrations of 2 M and 10 M, 44.9 – 83.6% for temperatures of 30 °C and 90 °C, and 45.7 – 82.7 % for stirring rates of 90 rpm and 540 rpm; while it decreases with increase in solid/liquid (S/L) ratio and particle diameter from 82.5 to 46.1% for S/L ratios of 20 g/L and 45 g/L and from 83.5 to 45.2% for particle sizes of <75 µm and <425 µm, respectively. The experimental data fitted into the diffusion through the product layer model while surface chemical reaction was established as the rate-determining step. The activation energy was estimated to be 26.40 kJ/mol while the frequency factor was estimated as 19.99 s−1. About 83.1% alumina was recovered from Akpugo kaolinite from the kinetic study while the overall kinetic constant was estimated as 4.253 s−1. Hence, the kinetic models considered were sufficient to analyze the experimental data.

Dissolution of metallic iridium powders in hydrochloric acid oxidizing media

Iridium is one of the most chemically inert platinum group metals. It is extremely resistant to many reagents, including alkaline and mineral acid solutions. This, combined with the physical properties of iridium, defines the spectrum of its practical applications. This paper demonstrates that metallic iridium powders of various dispersion degrees can be dissolved in hydrochloric acid media in one stage in the presence of hydrogen peroxide. The morphology, as well as the phase and chemical compositions were studied by means of transmission and scanning electron microscopy, X-ray diffraction analysis, adsorption measurements of specific surface area and chemical analysis. The study looked at refined (30&ndash;150 &mu;m particles), highly dispersed (150&ndash;200 nm) and nanocrystalline (8&ndash;15 nm) iridium. It also examined the dissolution kinetics of iridium(0) with different specific surface areas at the temperatures of 190 to 210 oC. For all the studied samples, the dissolution process was established to be of kinetic nature, and the obtained experimental data can be perfectly described with the shrinking core model. The dissolution activation energy for refined, highly dispersed and nanocrystalline iridium(0) in hydrochloric acid solutions in the presence of hydrogen peroxide is 145, 108 and 88 kJ/mol, correspondingly. This way, it was proved that the activation energy tends to go down as the particles get smaller. It was confirmed that iridium is present in solutions in the form of chloride complexes of quadrivalent iridium. Thus, metallic iridium was converted into chloride forms in an environmentally friendly way, which makes it easier to perform analysis for refining purposes, as well as further synthesis of iridium complexes. This research was carried out as part of a governmental assignment allocated&nbsp;to the Institute of Chemistry and Chemical Technology at the Siberian&nbsp;Branch of the Russian Academy of Sciences (Project 0287-2021-0014) and&nbsp;using the equipment of the Krasnoyarsk Regional Shared Knowledge Centre,&nbsp;a part of the Krasnoyarsk Science Center of the Siberian Branch of the Russian&nbsp;Academy of Sciences.

Thermogravimetric kinetic analysis of the Ce‐Zr composite oxygen carrier prepared by ball milling

AbstractA series of zirconium‐doped cerium‐based composite oxygen carriers were prepared using the ball milling method. The results from X‐ray powder diffraction (XRD), H2‐temperature programmed reduction experiments (H2‐TPR), and Brunauer–Emmett–Teller (BET) show that a solid solution, formed from CeO2 and ZrO2, possesses a mesoporous structure and exhibits excellent reaction performance. In addition, carbon nanotubes (CNTs) with an addition amount of 5 wt.% greatly increased the specific surface area of oxygen carriers, thereby improving the activity of solid solutions. In order to further understand the performance of oxygen carriers, the kinetics of H2 reduction of oxygen carriers was studied by thermogravimetric analysis (TGA). The three‐dimensional diffusion model showed the best fitting effect among four typical models (viz., the diffusion‐controlled model, the unreacted shrinking core model, the uniform model, and the nucleation‐nuclei growth model). Finally, the activation energies of CeO2, Ce9Zr1Oδ, and 5 wt.% CNTs Ce9Zr1Oδ were 223.92, 170.96, and 128.60 kJ/mol, respectively, which also correspond with the reactivity sequence of the oxygen carriers.

The effect of ultrasound on synthesis and energy storage mechanism of Ti3C2Tx MXene

Removal of aluminum (abbreviated to Al) accounts for the main step for synthesizing Ti3C2Tx MXene. To date, the synthesis of Ti3C2Tx MXene is hampered by the low removal efficiency of Al from Ti3AlC2. Ultrasound was therefore introduced to achieve efficient synthesis of Ti3C2Tx MXene by promoting the removal rate of Al from Ti3AlC2. It was found that ultrasonic aid can significantly boost the removal efficiency of Al. Additionally, distinct kinetics for the removal of Al was recognized as the advent of ultrasonic intervention: (i) the shrinking core model was used to describe the removal kinetics of Al in the case without ultrasound, whilst the shrinking particle model was capable for the case in presence of ultrasound; (ii) the activation energy for removal of Al with ultrasonic aid was 70.2 kJ/mol, indicating a chemical reaction-controlled process, whereas the corresponding value for the case without sonication was 28.1 kJ/mol, demonstrating a mixed kinetic feature of the removal process of Al. Morphological study showed that ultrasound can remove the surface-adhering reaction products and favors the formation of structures with flower-like morphology. The sample without sonication treatment exhibited typical capacitive behavior, whilst the contribution of diffusion-limited capacitance in addition to the capacitive behavior was readily observed for the sonication-treated sample. Surface chemistry study indicated the more prevalent oxidation of the sonication treated sample, which gave rise to a higher specific capacitance than those without sonication treatment.

Insight into the kinetic analysis of acid mine drainage treated by carbonate rock

ABSTRACT Acid mine drainage (AMD) has caused a great impact on soil, surface water, groundwater, plants or other organisms in the mining environment because of its high acidity, high sulphate content, and contains a variety of heavy metals. AMD treated by carbonate rocks have been regarded as a feasible technology for pollution control and applied widely in mine area. However, to date, the kinetics of the reaction between carbonate rock and AMD have not been investigated, resulting in the lack of systematic theoretical guidance for the implementation of this technology. In this study, effects of carbonate particle sizes and reaction temperature on AMD treatment were investigated. The dissolution efficiency of Ca2+ was used to quantitatively reflect extent of reaction, and the leaching kinetics was analysed based on the shrinking core model. The results showed that carbonate rocks with a particle size of 0.5–1.0 mm had the best pH-enhancing performance for AMD and highest removal efficiency for Fe3+ (>98.00%), while the Mn2+ and SO4 2− were temperature sensitive. The diffusion of solid product layer was the controlling step of the leaching reaction, and the apparent activation energy of the reaction was 12.63 kJ·mol−1.

Effects of silica gel nanopores and surfactants on CO2 hydrate formation kinetics—An experimental and modeling study

The carbon dioxide (CO2) hydrate formation kinetics in silica gel (SG) nanopores with the addition of surfactants are studied both experimentally and numerically. SGs with pore sizes of 50 and 100 nm are used as frameworks for hydrate formation in pores. Sodium dodecyl sulfate (SDS) or dodecyltrimethylammonium chloride (DTAC) are used as kinetics promoters which can greatly enhance gas–water mass transfer. An advanced shrinking core model considering CO2 solubility, pore size, surfactants, and capillary effect is established. The results reveal that the reaction rate constant is increased in large pores or in the presence of surfactants, saving up to 49.3 % time to achieve the same amount of gas uptake in 100-nm SG with 500-ppm SDS. The effective diffusion coefficient controlled by a reduction factor drops dramatically due to the enlargement of the reduction factor in small pores and more surfactants, thus hindering the gas diffusion through the formed hydrate shell. The initial water consumed by capillary effect is more prominent in smaller pores and with the addition of surfactants. The initial proportion of water consumed by capillary effect to the total water consumption is only 1%–26.6% without surfactants, but can be up to 74.9% in 50-nm SGs with 500-ppm SDS. This proportion is overall higher in SDS systems than that in studied DTAC systems, but it is not obviously affected by surfactant concentrations. The higher proportion of water consumed by capillaries is speculated to be due to the more capillary tubes with larger radii formed initially in the presence of surfactants. The modeling strategies in this work can be applied to hydrate formation mechanisms in other porous materials.

Enhancement of leaching copper by organic agents from waste printed circuit boards in a sulfuric acid solution

Leaching copper from waste printed circuit boards (WPCBs) by hydrometallurgy has always been a hot research topic. At atmospheric pressure, hydrogen peroxide (H2O2) was used as an oxidant to study the leaching behavior of copper from WPCBs in sulfuric acid (H2SO4) solution with ethylene glycol (EG). To elucidate the leaching mechanism of copper from WPCBs, the effect of various parameters on the leaching performance with or without EG was investigated. The results showed that the copper leaching process from WPCBs in the presence of EG was found to conform to the ash diffusion-controlled shrinking core model according to the kinetic curve and a activation energy of 18.38 kJ/mol. Moreover, the presence of EG strengthened the stability of H2O2, improved dispersity and increased electrical activity of WPCBs, which enhanced the leaching of copper from WPCBs in the high leaching temperature (>323.15 K). As a result, apart from the fact that the optimal leaching concentration of H2O2 was reduced by the addition of EG, the improved copper leaching efficiency from WPCBs was achieved by the addition of EG, as demonstrated by a maximum copper leaching efficiency of 98.01% and a maximum loss rate of 29.68%. Besides, the mineralogical and morphological properties of leaching residue validated the leaching results. Based on this, our findings confirmed the enhanced leaching performance of copper from WPCBs by EG, which benefited for the efficient recovery of copper from WPCBs.

CFD Modelling of Calcination in a Rotary Lime Kiln

A 2D axisymmetric computational fluid dynamics (CFD) model, coupled to a 1D bed model, has been developed to capture the key processes that occur within rotary lime kilns. The model simulates the calcination reaction using a shrinking core model, and predicts the start of calcination and the degree of calcination at the end of the kiln. The model simulates heat transfer due to radiation, convection and conduction between the gas, wall, chains, and bed. The 2D gas and 1D bed models are coupled by mass and heat sinks to simulate heat transfer, evaporation, and the calcination reaction. The model is used to simulate two industrial kilns, one wet and one dry. The steady-state simulation results are compared to mill data, and good agreement is found. A sensitivity analysis is also presented, to obtain insight on how operating conditions and model variables impact the calcination location and degree of calcination.

Ultrasonic-assisted tetrabromobisphenol A-bis-(2,3-dibromo-2-methylpropyl ether) extraction process from ABS polymer supported by machine learning

The extensive use of electronic and electrical equipment and ever-increasing rate of renewal inevitably generate numerous e-waste plastics which need to be disposed of properly, and eliminating the brominated flame retardants (BFRs) present in them can significantly alleviate their environmental impact. In the present study, TBBPA-bis-(2,3-dibromo-2-methylpropyl ether) (TBBPA-DBMP), a novel tetrabromobisphenol A-derived BFR, was removed using an extraction process assisted by ultrasonic in alcohol extractants. Response Surface Methodology (RSM) achieved by support vector regression (SVR) was used to predict the optimum extraction conditions (extraction time, extraction temperature, liquid to solid ratio) in methanol and ethanol solvent, respectively. The maximum predicted extraction efficiencies of TBBPA-DBMP were 98.1% under the optimized conditions of 178 min, 180 mL/g, 66 °C in methanol and 99.5% under the optimized conditions of 150 min, 178 mL/g, 66 °C in ethanol. And the validity of predicted optimal extraction conditions was verified. The plastic matrix was capable of being recovered well after extraction (recovery rate > 90%). Moreover, shrinking core model was referred to conduct the kinetic analysis of the extraction, which demonstrates that the interface transfer and internal diffusion are the rate-controlling step in the extraction of TBBPA-DBMP in both methanol and ethanol extractants. • TBBPA-DBMP was extracted from ABS polymer with ultrasonic-assistance. • RSM via machine learning predicted the optimum extraction conditions. • The plastic recovery rate was above 90% after extraction. • Interface transfer and internal diffusion are rate-controlling step in the process.

2D model of the transfer processes for CO2 methanation in a microchannel reactor

A dynamic two-dimensional model was developed for transfer processes in a microchannel reactor in an innovative plant concept for CO2 methanation. The model is based on balance equations together with deactivation and sulfidation submodels taking into account the chemisorption of impurity (H2S). The deactivation of the catalyst is described by Levenspiel’s deactivation kinetic model (LDKM). Sulfidation is defined by the shrinking core model (SCM) equation. Following the rate-determining step assumption, a simplified mechanism is derived for CO2 and CO methanation in a microchannel reactor with kinetic rate expressions. The developed 2D model adequately describes transient and steady-state behavior of the microchannel methanation reactor following the trend in experimental profiles available in the literature.