Initial Gas Mixture Research Articles

STUDY ON KINETICS OF BIOMASS PYROLYSIS IN THE FIXED BED. 2. ANALYSIS OF THE RESULTS OF CALCULATING THE THERMAL DECOMPOSITION OF DIFFERENT TYPES OF SOLID FUEL

Using the constructed non-stationary model of the dynamics of the release of volatile substances in a fixed bed [1], extensive numerical studies on three types of biomass pyrolysis Wood Birch, Wood quebracho and Bagasse were performed in order to determine the light gas composition satisfactorily coinciding with experimental data. As a result of research, the following composition of light gas (in mass fractions) was determined for the first time: CO = 0.464, CO2 = 0.101, H2 = 0.01, H2O = 0.23, C6H6.2O0.2 = 0.058, and C1.16H4 = 0.137, which differs from the light gas composition given in modern sources copies [2−4] (in mass fractions): CO = 0.396, CO2 = 0.209, H2 = 0.019, H2O = 0.249, and C6H6.2O0.2 = 0.127 [3], also CO = 0.46, CO2 = 0.08, H2 = 0.015, H2O = 0.23, C6H6.2O0.2 = 0.058, and CH4 = 0.157 [2]. Obtained calculation results for Wood quebracho with refined composition of light gas in terms of dry mass at a temperature of 800 °С: H2 = 15.56 %, CO2 = 7.134 %, CO = 51.4 %, C1.16H4 = 23.71 % (CH4 = 16.6 %, C2H4 = 7.46 %), and C6H6.2O0.2 = 2.21 % — agree satisfactorily with the experimental data. At the exit from the retort, mixed pyrolysis gas composition changes little over time and differs in the values of the gas components from the pyrolysis gases compositions obtained in the elementary volumes of the retort. This discrepancy is explained by the fact that the initial gas mixture contains components obtained at low temperatures with a high content of H2 and CO2 and a low concentration of CO and C1.16H4. Bibl. 20, Fig. 11, Tab. 4.

Use of ceramic fiber modified with ferrites for the cleaning of flue gases of graphitization furnaces

Gaseous emissions of industrial enterprises as a result of their economic activities adversely affect the ecological situation, and even worsen the sanitary and hygienic working conditions of the personnel. Carrying out chemical reactions in the furnace equipment of metallurgical and electrothermal production, as a rule, lead to the formation of gases containing various toxic impurities, including carbon monoxide, the disposal of which is an important environmental task. As the calculations show, the total amount of annual CO emissions in Ukraine is 704344.218 t/year, which in percentage terms is 31.42% of the total emissions of pollutants and greenhouse gases, except for carbon dioxide - 2242020.75 t/year. The release of significant amounts of poisonous CO into the atmosphere is a serious problem that must be solved at the level of industrial production. One of the effective directions in the field of purification of industrial gas emissions from toxic carbon monoxide is the application of catalytic technologies due to the use of compositions based on transition metals, especially ferrite materials. Recently, systems for neutralizing toxic gases, including glass fiber catalysts, have become widely popular. The study of the CO oxidation process was carried out on a flow-type installation with a stationary weight of the catalyst. Catalytic purification of the gas mixture from CO was studied in the range of 50-450 °C. The concentration of carbon monoxide in the initial gas mixture at the entrance to the reactor was varied in the range of 1-2 vol. %. If necessary, helium was used as an inert gas. Ceramic fiber was used as a fiberglass support for catalytic systems for the oxidation of gaseous emissions containing CO. Ferrite catalysts were applied to ceramic fiber by the method of impregnation from sulfate solutions of iron, copper, and potassium bichromate. From the temperature dependences of the conversion of carbon monoxide with a concentration of 1-2% on ferrite catalysts on a ceramic fiber carrier, it can be seen that 100% conversion of carbon monoxide is not achieved even at a temperature of 450 ºС. In the case of using a mixture of magnetite and copper ferrite, the degree of conversion of CO was 97% at temperatures above 300 ºС and stably ensured the neutralization of CO until the conversion degree of 98% was reached at a temperature of 450 ºС. At a temperature of 450 ºС, the highest degree of conversion of 99% was ensured by using chromium ferrite, but the specified chromium-ferrite catalyst at a temperature of 400 ºС provided a slightly lower oxidation efficiency, that is, the specified catalyst has less advantages for use in fluctuating gas temperatures in industrial conditions. When magnetite and copper ferrite were used separately, the degree of CO conversion was 40% and 75%, respectively. Therefore, the conducted studies showed that the use of ceramic fiber modified with ferrites can be effectively used for the purification of flue gases of electrode graphitization furnaces, in particular, the neutralization of toxic carbon monoxide. Obtaining ceramic fiber modified with ferrite material does not require significant capital investments, as it is based on the use of liquid waste from etching, copper plating, and chrome plating of galvanic production. Laying ceramic fiber on top of the thermal insulation of the graphitization furnaces of electrode production will also reduce the inflow of oxygen into the porous space and reduce the formation of carbon monoxide, which will contribute to the improvement of the ecological situation at the electrode production. The obtained results on the use of ceramic fiber modified with ferrite material as a catalyst for the neutralization of carbon monoxide are a highly effective and affordable measure to reduce the man-made burden of electrode production on the environment.

Hydrate phase equilibrium conditions for H2S and CO2 gas mixture removal from natural gas: modeling and optimization study

In this study, for the first time, a comprehensive mathematical modeling of the optimal conditions for the gas hydrates formation of hydrogen sulfide (H2S) and carbon dioxide (СО2) was carried out with the aim of them removing from natural gas. The study was carried out on a model gas mixture close to the natural gas composition: CH4 – C2H6 – С3Н8 – n-С4Н10 – СО2 – H2S – N2. A temperature range of 268.15–283.15 К and a pressure range of 2.00–8.00 MPa were investigated. The efficiency was assessed based on the gas hydrate distribution coefficients. It was found that the gas hydrate extraction of H2S is more significantly affected by the concentration of H2S in the initial gas mixture. The gas hydrate extraction of СО2 is more significantly affected by the temperature and pressure of the gas separation unit. The maximum gas hydrate distribution coefficient of H2S is 42.05 at T = 268.15 K, p = 8.00 MPa. The maximum gas hydrate distribution coefficient of СО2 is 0.49 at T = 283.15 K, p = 8.00 MPa. Due to the small amounts of CO2 entrapped in gas hydrates, a scheme that combines a multi-stage hydrate-based and membrane technology has been suggested to purify natural gas further.

Tailoring gas hydrate lattice dimensions for enhanced methane selectivity in biogas upgrading

Gas hydrates, specifically clathrate hydrates, have emerged as a potential separation medium for biogas containing methane (CH4) and carbon dioxide (CO2). However, the efficient separation of CH4 and CO2 remains challenging due to their similar cage occupation behavior within the hydrate structure. This study aimed to enhance CH4 selectivity by modifying the hydrate lattice to exclude CO2 from large cages and reduce the size of small cages through lattice engineering. To achieve this, tert-butyl alcohol (TBA) and trimethylene oxide (TMO) were employed as thermodynamic promoters, inducing strong and weak cage expansion, respectively. The results revealed that TMO hydrates, with their weak cage expansion, exhibited improved CH4 selectivity compared to TBA hydrates, which displayed strong cage expansion due to the larger size of TBA. Multi-stage separation experiments demonstrated that TMO hydrates required four unit stages, while TBA hydrates necessitated more than five unit stages to obtain purified CH4 (> 85%) from an initial gas mixture of CH4 (50%) and CO2 (50%). Additionally, TMO hydrates consistently exhibited higher separation factors than TBA hydrates in all unit stages. The findings emphasize the influence of the thermodynamic promoter's size on the separation performance of gas hydrates in separating CH4 from CH4 + CO2 mixtures. The study provides valuable insights into enhancing CH4 selectivity through lattice engineering and offers guidance in selecting suitable thermodynamic promoters for gas hydrate-based biogas upgrading applications.

COMPUTER MODELING AND EVALUATION OF THE POSSIBILITY OF CONTROLLING THE CATALYTIC PROCESS IN THE POLYTROPIC MODE OF OPERATION OF A TUBULAR REACTOR

The results of the development of a mathematical model for quantifying the current profile of the conversions of the key component of a chemically active reaction gas mixture in the course of its movement in a polytropic tubular reactor of the "pipe in a pipe" type are presented. The volume of the inner tube of the reactor is filled with catalyst granules and is an exothermic chemical reaction zone. To develop models of concentration and temperature fields in the reaction zone, the corresponding balance differential equations were used. Such a mathematical model allows for an operational analysis of the technological regime of the reactor when preparing initial data for the design and development of an automatic control system. For computer simulation, the mathematical description of the reactor is represented by a system of differential equations in the form of a Cauchy. The model was tested on the example of evaluating the process of catalytic contact oxidation of sulfur dioxide in a reactor with a direct-flow circuit of heat carriers and the return of a heated initial gas mixture to the inlet of pipes with a catalyst. The obtained dependence of the conversion on the temperature during the course of the reactor has a characteristic form that coincides with that described in the literature sources. A structural model of the automatic control system of a polytropic tubular reactor is proposed, which is oriented to the use of computer simulation. The model of the automatic control system was tested on a specific example of stabilization of the conversion of sulfur dioxide at the reactor outlet with an unstable flow rate of the initial gas mixture at the inlet. To assess the capability and quality of the developed control system, the SimInTech dynamic modeling environment of technical systems was used. It is assumed that the mathematical model developed in the article can be used to create adaptive or self-adjusting process control systems that use tubular reactors. For citation: Andreev A.S., Aksenchik K.V. Computer modeling and evaluation of the possibility of controlling the catalytic process in the polytropic mode of operation of a tubular reactor. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2023. V. 66. N 2. P. 120-127. DOI: 10.6060/ivkkt.20236602.6727.

Possibility of application of high silicon keolitic catalyst with thermal and mechanochemical treatment for catalytic flavoring of the propane-butane fraction

The studies were carried out in a flow catalytic device in the stationary phase of the catalyst (catalyst volume 6 cm3), at 450–6000C, at normal atmospheric pressure (P = 0.1 MPa), was carried out under conditions in which the volumetric velocity of the initial gas mixture was 600–1000 h-1. Qualitative and quantitative composition of propane-butane fraction and reaction products were analyzed on the chromatograph “Chromatic-Crystal 5000M” under the following favorable conditions: separation of gaseous products was carried out in a column thermal conductivity detector (TCD) with a length of 3 m and a diameter of 3 mm filled with 8% NaOH / Al2O3. The separation of liquid products was carried out in a DV-1 capillary quartz column (30 m x 0.25 μm), and detection was carried out in a flame ionization detector. Check the acidity of the catalysts. The acid characteristics of the samples were studied by the method of the programmed desorption of ammonia in the automatic chemisorption analyzer “USGA-101”. X-ray phase analysis: X-ray examination of the samples (X-ray phase analysis) was performed on a diffractometer XRD-6100 (Shimadzu, Japan). Phase identification was performed based on radiographs of individual components (JSPDS card index) based on data from the literature. The purpose of this work is to study the possibility of using thermally and mechanochemically treated high-silicon zeolite catalysts in the catalytic aromatization of the propane-butane fraction and acid properties.

Experimental and Simulation Study on Coproduction of Hydrogen and Carbon Nanomaterials by Catalytic Decomposition of Methane-Hydrogen Mixtures

Among all hydrocarbons, the methane molecule contains the highest amount of hydrogen with respect to carbon. Therefore, the catalytic decomposition of methane is considered as an efficient approach to produce hydrogen along with nanostructured carbon product. On the other hand, the presence of hydrogen in the composition of the initial gas mixture is required for the stable operation of the catalyst. In present work, the experiments on the catalytic decomposition of methane–hydrogen mixture were performed in a flow-through quartz reactor equipped with McBain balances under atmospheric pressure. The catalyst NiO-CuO/Al2O3 was prepared by the mechanochemical activation technique. The maximum carbon yield of 34.9 g/gcat was obtained after 2 h of experiment at 610 °C. An excess of hydrogen in the reaction mixture provided the long-term activity of the nickel–copper catalyst. The durability tests ongoing for 6 h within a temperature range of 525–600 °C showed no noticeable deactivation of the catalyst. Two kinetic models, D1a and M1a, were proposed for the studied decomposition of the methane–hydrogen mixture over the nickel–copper catalyst. The kinetic constants for these models were determined by means of mathematical modelling.

Composition, structure, and magnetic properties of SiCxNyFez films produced by the PECVD method from a gas mixture of 1,1,1,3,3,3-hexamethyldisilazane, ferrocene, and helium

Composite SiCxNy:Fez films with magnetic properties were obtained by plasma-enhanced chemical vapor deposition from gas mixtures of hexamethyldisilazane, ferrocene, and helium. In the work, the ratio of elements of the initial gas phase was varied at a constant synthesis temperature of 873 K, which made it possible to obtain films that differ significantly in the content of elements, but are similar in structure. Using a complex of modern research methods: infrared spectroscopy, Raman spectroscopy, energy-dispersive X-ray spectroscopy, the relationship between changes in the concentration of elements of the initial gas mixture and changes in the composition of SiCxNy:Fez films was established. The structure of the obtained samples was studied by X-ray photoelectron spectroscopy, extended X-ray absorption fine structure, and X-ray phase analysis. Based on the data obtained, it is assumed that, in the studied range of conditions, the obtained films can be attributed to two different materials. Films containing less than 13% iron consist of an amorphous SiCxNy matrix with inclusions of disordered carbon and iron silicides. Films containing more than 27% iron are composite. The composite includes disordered carbon, iron silicides, and iron carbides. As well as inclusions of silicon nitride, silicon oxide and carbon nitride. It is assumed that the magnetic properties of the films are due to the content of iron silicides and iron carbides in them. Films containing more than 27 at% iron have ferromagnetic properties with a Curie temperature above room temperature.

Laminar burning velocities of cyclopropane flames

Cyclopropane, c-C3H6, the simplest cycloalkane, is seldom included in detailed kinetic mechanisms for hydrocarbons, though it may exhibit unusual kinetic features yet to be analysed due to a lack of studies of its combustion characteristics. In this work, laminar burning velocities of cyclopropane flames have been determined using the heat flux method at atmospheric pressure and an initial gas mixture temperature of 298 K. The fuel consisting of 50% c-C3H6 + 50% N2 was burnt with air covering the range of equivalence ratios 0.6 – 1.5. The detailed kinetic model of the authors was extended by the reactions of cyclopropane and cyclopropyl radical, c-C3H5, with the rate constants selected from the literature. This mechanism, as well as the most recent mechanisms for c-C3H6 of Wang et al. (2022) and of Lei et al. (2022), have been compared with the burning velocities of propylene + air flames and with the new experimental results for cyclopropane flames. The model of Lei et al. (2022) significantly underpredicts the burning velocities for both fuels, on the other hand, good agreement with predictions of the present model and of Wang et al. (2022) was observed at 1 atm. However, further sensitivity and rate-of-production analyses revealed important differences in the pathways of c-C3H6 oxidation predicted by the two mechanisms. The present kinetic model was also tested using all available measurements of cyclopropane ignition delays in shock tubes, which combined cover the range of equivalence ratios from 0.33 to 3, at pressures 1 - 10 atm, and temperatures 1100 – 2100 K. Overall good performance of the model was demonstrated across these ranges of conditions and compositions of the mixture. A direct comparison of the experimental data shows that ignition delays of propylene are slightly longer than those of cyclopropane, yet in most cases within the overlapping uncertainties or scattering between different experimental facilities. The laminar burning velocities of c-C3H6 + air are slightly higher than those of C3H6 + air at least according to the predictions of the present mechanism and the model of Wang et al. (2022).

Molecular dynamics studies on separation of CO2/CH4 by the ionic liquids encapsulated ZIF-8

The utilisation of ZIF-8 membrane with encapsulated ionic liquids (IL@ZIF-8 composite membrane) has been demonstrated as one of the most efficient approaches for CO 2 /CH 4 separation. However, compared to pure ZIF-8 membrane, the mechanisms behind the CO 2 /CH 4 selectivity enhancement caused by the encapsulation of ILs still remain indistinct. Here, molecular dynamics (MD) simulations have been performed to investigate the separation and diffusion of gas molecules in the IL@ZIF-8. The simulated results show that the selectivity enhancement is because the adsorbed CO 2 /CH 4 ratio has been increased when ILs are encapsulated into ZIF-8. Detailed analysis indicates that the diffusion of CO 2 /CH 4 molecules follows three different pathways of the hexagonal microstructure of IL@ZIF-8 composite, of which the route to the nearest composite cells (route I ) has the highest possibility, and gives the smallest mean diffusion displacement. Lastly, the effect of CO 2 /CH 4 ratio in the initial gas mixture has been explored, and we found that CO 2 /CH 4 selectivity is related to the concentration of CO 2 , where three regions with different slopes have been classified. The diffusion mechanisms of CO 2 /CH 4 in IL@ZIF-8 composite were investigated by MD simulations, including diffusion routes and effects of CO 2 concentration. • The diffusion mechanisms of CO 2 /CH 4 molecules in IL@ZIF-8 composite were fully investigated by MD simulations. • A route with minimum length for gas molecules diffusion has been identified based the mean diffusion displacement analysis. • MD simulation reveals a general relationship between the CO 2 /CH 4 selectivity and CO 2 concentration.

Synthesis, Properties and Aging of ICP-CVD SiCxNy:H Films Formed from Tetramethyldisilazane

Amorphous hydrogenated silicon carbonitride films were synthesized on Si(100), Ge(111), and fused silica substrates using the inductively coupled plasma chemical vapor deposition technique. 1,1,3,3-tetramethyldisilazane (TMDSN) was used as a single-source precursor. The effect of the precursor’s pressure in the initial gas mixture, the substrate temperature, the plasma power, and the flow rate of nitrogen gas as an additional reagent on the film growth rate, element composition, chemical bonding, wettability of film surface, and the optical and mechanical properties of a-SiCxNy:H films was investigated. In situ diagnostic studies of the gas phase have been performed by optical emission spectroscopy during the film deposition process. The long-term stability of films was studied over a period of 375 days. Fourier-transform infrared (FTIR) and X-ray energy dispersive spectroscopy (EDX), and wettability measurements elucidated the oxidation of the SiCxNy:H films deposited using TMDSN + N2 mixture. Films obtained from a mixture with argon had high stability and maintained the stability of element composition after long-term storage in ambient air.

Gas-Phase Nucleation of Diamond Clusters upon a Sharp Rise in Temperature under Conditions of CVD Synthesis

It is shown that the predominant nucleation of diamond nuclei (instead of graphite ones) in plasma or hot-filament assisted CVD technology is due to a sharp increase in the temperature of the region of the initial gas mixture’s motion. The nucleation of diamond nuclei then occurs immediately in the gas phase. The reason for such predominant nucleation is high oversaturation by small hydrocarbon fragments in the gas mixture, due to a rapid change in temperature and substantial differences between the desorption of such fragments from the surfaces of nuclei and the oxidation of nuclei. A way is described of synthesizing massive diamonds without the use of high pressures and CVD technology in its traditional form.

Catalytic Synthesis of С2-С4-Alkenes from Dimethyl Ether

In the study, the effect of the volumetric velocity of the initial gaseous mixture on the catalytic properties of Zn-Zr-Cu/HSZ/Al$_2$O$_3$ in the conversion of dimethyl ether to olefins was studied. When the volumetric rate is increased by 5 times, the conversion of dimethyl ether decreases from 96.5 to 40.7 %, the total selectivity for C$_2$=-C$_4$=olefins decreases from 59.0 to 75.5 mas.%, at the same time, the yield of the by-products of the reaction - C$_2$ + paraffin is reduced. A decrease in the reaction temperature at the equal conversion of dimethyl ether leads to an increase in selectivity for both ethylene and propylene due to a decrease in the formation of methane and C$_2$+paraffin in the reaction products. Thus, in copper-containing zeolite catalysts, lower olefins than dimethyl ether provide higher conversion of raw material and higher selectivity of olefin formation (up to 90 mas. %.). Also, changing the initial raw material composition and regime parameters allows a significant change in the ratio of olefins to each other.

Laminar burning velocities of propionic acid + air flames: Experimental, modeling and data consistency study

Laminar burning velocities of propionic acid + air flames have been determined using the heat flux method at atmospheric pressure and initial gas mixture temperature of 348 K over the range of equivalence ratios 0.7–1.3. The detailed kinetic model of the authors was extended by the reactions of propionic acid and its intermediates. Attention has been paid to the proper description of the formation and consumption of 1,1-propenediol, methyl ketene, and acrylic acid. New experimental results have been compared with the modelling using this kinetic mechanism and the mechanism of Zhang et al. (2021). The comparison of the new and available from the literature measurements obtained at different initial temperatures with predictions of the two models allowed for analysis of the data consistency for the burning velocities of propionic acid, as well as for acetic and formic acids. Inconsistencies of some datasets for these short-chain carboxylic acids were identified and discussed.

Combustion chemistry of methoxymethanol. Part II: Laminar flames of methanol+formaldehyde fuel mixtures

In the present study, the laminar burning velocities of mixtures of up to 16.4% (mol) formaldehyde in methanol, burning with air, were determined at atmospheric pressure using the heat flux method covering lean, stoichiometric and rich flames at initial gas mixture temperatures of 298, 318 and 338 K. Results published in the literature indicate that evaporation of CH2O+CH3OH fuel blends should lead to a gaseous mixture of formaldehyde, methanol and methoxymethanol, although the composition of these components in the gas phase was not well defined. To interpret the measurements performed in the present study, the detailed kinetic model developed by the group of Konnov was used. The recently updated mechanism was further extended by the reactions of methoxymethanol with the rate constants calculated in Part I of the present study. A comparison of the predictions of this mechanism with the new experimental data indicated that between 40% and 60% of CH2O present in the investigated CH2O+CH3OH mixtures were at 473 K evaporated as gaseous formaldehyde monomer, while the rest was released within CH3OCH2OH. Laminar burning velocity results suggest partial condensation of methoxymethanol in the CH3OH+CH2O fuel mixture with 5.84% formaldehyde at rich conditions and 298 K. These observations allowed evaluation of the partial pressure of CH3OCH2OH which was found to be between 0.35 and 0.52 kPa. The sensitivity and rate-of-production analyses revealed that the reduced reactivity with the increased amount of methoxymethanol in the fuel mixtures is explained by the conversion of CH3OCH2OH to CH3OCHOH radicals due to favored H-abstraction from the secondary hydrogen atoms predicted by ab initio calculations compared to other sites of methoxymethanol. Hydroxyl-methoxyl-methyl radicals further decompose forming slowly reacting formic acid and methyl radicals.

Methodology for creating and studying units for adsorption separation and purification of gas mixtures

Methodology for creating and studying technological processes and resource-saving units for adsorption separation and purification of gas mixtures (atmospheric air, synthesis gas) with cyclically changing pressure was developed. A problem-oriented hardware-software complex designed to study the properties and operation regimes of units for adsorption separation of gas mixtures and extraction of product gases was created. The complex can also be used to prepare initial data for the design of industrial units for separation and purification of gas mixtures by the method of pressure swing adsorption. The coefficients of mass transfer and mass conductivity in the adsorbent were calculated for the processes during adsorption and desorption of the adsorptive (nitrogen, oxygen, carbon dioxide and monoxide, hydrogen) using experimentally obtained kinetic curves, and the adequacy of mathematical models was established. Using the hardware-software complex, experimental and numerical studies of technological processes for extraction of product gases (oxygen and hydrogen with a purity of 45 to 95.5 vol.%, from 99 to 99.99 vol.%, respectively), the effect of mass and heat exchange processes and operating variables (“adsorption-desorption” cycle time, pressure at the adsorption step), disturbing influences (composition and temperature of the initial gas mixture) on the performance indicators of the pressure swing adsorption unit were carried out.

Haze Formation in Warm H2-rich Exoplanet Atmospheres

Abstract New observing capabilities coming online over the next few years will provide opportunities for characterization of exoplanet atmospheres. However, clouds/hazes could be present in the atmospheres of many exoplanets, muting the amplitude of spectral features. We use laboratory simulations to explore photochemical haze formation in H2-rich exoplanet atmospheres at 800 K with metallicity either 100 or 1000 times solar. We find that haze particles are produced in both simulated atmospheres with small particle size (20–140 nm) and relatively low production rate (2.4 × 10−5 to 9.7 × 10−5 mg cm−3 hr−1), but the particle size and production rate is dependent on the initial gas mixtures and the energy sources used in the simulation experiments. The gas phase mass spectra show that complex chemical processes happen in these atmospheres and generate new gas products that can further react to form larger molecules and solid haze particles. Two H2-rich atmospheres with similar C/O ratios (∼0.5) yield different haze particle size, haze production rate, and gas products, suggesting that both the elemental abundances and their bonding environments in an atmosphere can significantly affect the photochemistry. There is no methane (CH4) in our initial gas mixtures, although CH4 is often believed to be required to generate organic hazes. However, haze production rates from our experiments with different initial gas mixtures indicate that CH4 is neither required to generate organic hazes nor necessary to promote the organic haze formation. The variety and relative yield of the gas products indicate that CO and N2 enrich chemical reactions in H2-rich atmospheres.

ИССЛЕДОВАНИЕ УСИЛИТЕЛЬНЫХ СВОЙСТВ ОБЛУЧАЕМОЙ НЕЙТРОНАМИ ДВИЖУЩЕЙСЯ ГАЗОВОЙ СРЕДЫ, СОДЕРЖАЩЕЙ НАНОЧАСТИЦЫ УРАНА

The search for promising ways of nuclear energy usage has led to the emergence of a whole line of research on the direct conversion of the nuclear reaction products energy into laser radiation. In the present work, the amplifying properties of a spatially inhomogeneous nuclear-excited containing uranium nanoparticles moving argon-xenon medium irradiated by an inhomogeneous neutron field were studied. This work purpose is to investigate the dependence of the laser active medium amplifying properties on the initial gas mixture velocity, neutron pulse duration, and the neutron flux space-time distribution. As a short result, we could present the radial dependence of the laser radiation intensity gain at different points in time showed on the picture below. Summarizing laser radiation intensity gain calculations results: an active laser- medium with a length of 1 m provides a significant amplification (10 or more times) of the laser radiation in one pass. And it seems to be reasonable to continue studying the amplifying properties of such laser-active medium, considering the laser radiation’s wave nature.

Numerical study of the dynamics of synthesis gas adsorption separation

A numerical study of the dynamics of pressure swing adsorption process for synthesis gas separation and hydrogen concentration was carried out. The influence of regime parameters (compressor and vacuum pump outlet pressures, duration of the "adsorption-desorption" cycle, backflow coefficient) and design parameters (height of the adsorbent bulk layer and the internal bed diameter) on the recovery and purity of hydrogen, plant performance in a given range of changes in the temperature, composition and pressure of the initial gas mixture was studied. It is found that when the hydrogen content decreases from 68 to 48 vol. % and a simultaneous increase in the carbon dioxide content in the initial gas mixture from 27 to 47 vol. % required hydrogen purity value at 99.99 vol. % can be achieved by reducing the pressure at the outlet of the vacuum pump from 0.75?105 to 0.5?105 Pa. At the same time, the duration of the adsorption stage increases from 120 to 150 seconds, and the degree of hydrogen extraction decreases from 55 to 52% due to an increase in the proportion of the flow selected for the regeneration of the adsorbent. Increasing the temperature of the initial gas mixture from 293 to 323 K leads to the need to reduce the duration of the adsorption stage from 148 to 42 s due to a decrease in the equilibrium concentrations of carbon dioxide and monoxide in the adsorbent.

Modeling the Flow of Multicomponent Reactive Gas on Unstructured Grids

Introduction. The article deals with mathematical modeling of the subsonic flow of a multicomponent reactive mixture in a flowing chemical reactor. The numerical algorithm is based on the finite volume method; the calculation is performed on unstructured triangular grids using the Message Passing Interface parallel computing technology. Materials and Methods. To describe the flows under studying, the Navier–Stokes equations are used in the approximation for low Mach numbers. To solve these equations, the finite volume method on unstructured triangular grids is used. The study uses a splitting scheme for physical processes, namely, the chemical kinetics equations responsible for the transformations of substances are first solved, and then the equations describing the conservation laws of momentum and energy for each component of the gas mixture are solved. To find numerical flows through the edges of the grid elements, the Lax–Friedrichs–Rusanov scheme is used. To solve the equations of chemical kinetics, a compact algorithm proposed by the team led by N.N. Kalitkin is used. The METIS library is used to divide the grid into connected subdomains with an approximately equal number of cells. To organize parallel computing, Message Passing Interface technology is used. Results. The article presents a numerical algorithm for studying multicomponent gas flows on unstructured triangular grids taking into account viscosity, diffusion, thermal conductivity, and chemical reactions. As a result of the study, a numerical simulation of the flow of a subsonic multicomponent gas in a flowing chemical reactor was carried out using ethane pyrolysis as an example. Computational, known numerical solutions and experimental data of ethane pyrolysis in a flowing reactor are compared. Discussion and Conclusion. The numerical results on the conversion of the initial gas mixture are in good agreement with the known experimental data. The presented distribution patterns of the main components of the mixture and gas-dynamic parameters correspond to the flow pattern observed experimentally. Further work in this direction involves the modeling of subsonic gas flows on unstructured tetrahedral meshes using algorithms of higher accuracy for a more accurate study of ongoing processes.