Chemical Gas Research Articles

Design of smart nose system for hazardous zone

The sole goal of the project is to develop design along with production of a novel smart nose system capable of accurately sensing and identifying a wide range of chemical gases. This innovative technology will utilize advanced gas sensors, data processing, and machine learning techniques to enable real-time gas detection and identification, with potential applications in various fields, including environmental monitoring, industrial safety, and healthcare. The vital goal is to create a reliable, user-friendly, and versatile device that enhances our ability to detect and respond to hazardous gases in our surroundings, ultimately contributing to safety, environmental preservation, and public health. The system will integrate wireless communication for remote monitoring and control, ensuring convenience and accessibility for end-users. Furthermore, the smart nose will be designed to have low power consumption, making it suitable for deployment in remote and resource-limited settings. Prototyping and rigorous testing will be conducted to validate the system's performance and robustness. The project aims to push the boundaries of current gas sensing technologies, paving the way for future advancements in smart environmental sensing.

Effective Strategy toward Obtaining Reliable Breakthrough Curves of Solid Adsorbents.

Metal-organic frameworks (MOFs) have demonstrated their versatility in a wide range of applications, including chemical separation, gas capture, and storage. In industrial adsorption processes, MOFs are integral to the creation of selective gas adsorption fixed beds. In this context, the assessment of their separation performance under relevant conditions often relies on breakthrough experiments. One aspect frequently overlooked in these experiments is the shaping of MOF powders, which can significantly impact the accuracy of breakthrough results. In this study, we present an approach for immobilizing MOF particles on the surface of glass beads (GBs) utilizing trimethylolpropane triglycidyl ether (TMPTGE) as a binder, leading to the creation of MOF@GB materials. We successfully synthesized five targeted MOF composites, namely, SIFSIX-3-Ni@GB, CALF-20@GB, UiO-66@GB, HKUST-1@GB, and MOF-808@GB, each possessing distinct pore sizes and structural topologies. Characterization studies employing powder X-ray diffraction and adsorption isotherm analyses demonstrated that MOFs@GB retained their crystallinity and 73-90% of the Brunauer-Emmett-Teller area of their parent MOFs. Dynamic breakthrough experiments revealed that, in comparison to their parent MOFs, MOF@GB configurations enhanced the accuracy of breakthrough measurements by mitigating pressure buildup and minimizing reductions in the gas flow rate. This work underscores the significance of meticulous experimental design, specifically in shaping MOF powders, to optimize the efficacy of breakthrough experiments. Our proposed strategy aims to provide a versatile platform for MOF powder processing, thereby facilitating more reliable breakthrough experiments.

Low loss and ultra-broadband design of an integrated 3 dB power splitter centered at 2 µm.

Because chemical gas is sensitive to absorption in the 2µm band, and 2µm matches the absorption band of the remote sensing material, many remote sensors and optical sensors are designed to operate in the 2µm wavelength region. In this paper, we designed an integrated 3dB power splitter centered at 2µm. The study of this device is built on a silicon-on-insulator (SOI) platform. We introduced a subwavelength grating (SWG) to improve the performance of the device. We used the three-dimensional finite-difference time-domain (3D FDTD) method to analyze the effect of the structure on the power splitter. The insertion loss (IL) of the fundamental TE mode is only 0.04dB at 2µm and its bandwidth of IL <0.45d B is 940nm (1570-2510nm). It is suitable for multidomain and all-band photonic integrated circuits at 2µm.

A passive wireless surface acoustic wave (SAW) sensor system for detecting warfare agents based on fluoroalcohol polysiloxane film

Long-term monitoring of environmental warfare agengts is a challenge for chemical gas sensors. To address this issue, we developed a 433 MHz passive wireless surface acoustic wave (WSAW) gas sensor for dimethyl methylphosphonate (DMMP) detection. This WSAW gas sensor includes a YZ lithium niobate (LiNbO3) substrate with metallic interdigital transducers (IDTs) etched on it, and an antenna was placed near the IDT. A DMMP-sensitive viscoelastic polymer fluoroalcoholpolysiloxane (SXFA) film was prepared on a LiNbO3 substrate, and mode modeling coupling was used to optimize the design parameters. The sensor can function properly in an environments between −30 °C and 100 °C with humidity less than 60% RH. When the wireless transmission distance was within the range of 0–90 cm, the sensor noise increased with distance, and the stability was less than 32°/h. While optimizing the film thickness of SXFA, a relationship was observed between sensor sensitivity and film thickness. When the film thickness of SXFA reached 450 nm, the optimal value was reached. At a distance of 20 cm between the transmitting and receiving antennas, DMMP was detected at different concentrations with the developed WSAW gas sensor. The lower detection limit of DMMP was 0.48 mg/m3, the sensitivity of the sensor was 4.63°/(mg/m3), and repeatable performance of the sensor was confirmed.

Совершенствование технологии внутрипластовой генерации СО2 с компенсацией технологических потерь концентрации химреагентов

The paper is about the enhanced oil recovery technology, based on in-situ carbon dioxide generation, after stoichiometric reaction between gas releasing chemical agent and gas producing one. Two ways of technology improvement are considered: for more uniform in-situ CO2 generation and for more safety when chemicals injection. Both ways require sufficient increase of buffer water, which divides reactive chemicals. Larger buffer water volumes, when being mixed with chemicals water solutions, sufficiently drop down chemical concentration. It also decreases CO2 concentration in water solution. Finally, chemicals and CO2 concentrations, for in- situ generation, decrease. To prevent such decrease, it is necessary to adjust, increase chemicals concentration, when preparing chemical water solution, so to consider further dilution in buffer water and to ensure required stoichiometric concentration in reservoir conditions. Increase of chemicals concentration can be also from decrease of chemicals solutions volumes. Quantitative estimates are given for increase of buffer water volumes, for impact of such increase on decrease of initial chemicals concentrations and decrease of CO2 concentration, in water solutions, as well. Working formulas are provided for calculations on buffer water volumes, adjusted, increased concentrations and decrease volumes of chemicals water solutions, at their preparation stage.

Utilization of Gaseous Chemicals in Food Storage and their Effects on the Indoor Environment

Utilization of Gaseous Chemicals in Food Storage and their Effects on the Indoor Environment

Source Localization of the Chemical Gas Dispersion Using Recursive Tracking With Transformer

Source Localization of the Chemical Gas Dispersion Using Recursive Tracking With Transformer

CFD Investigation of Shell and Tube Heat Exchanger: Impact of Various Tube Bundle Combinations on Heat Transfer Coefficient and Pressure Drop

Shell and tube heat exchangers play a crucial role in various industries, including chemical processing, oil and gas, power generation, and HVAC systems. These exchangers are widely used for transferring heat between two fluids while maintaining their separation. The design of a shell and tube heat exchanger consists of a bundle of tubes enclosed within a larger shell. The hot fluid flows through the tubes, while the cold fluid circulates around them in the shell, facilitating efficient heat transfer and pressure drop of the system. The performance of a shell and tube heat exchanger is influenced by various factors, including the configuration of the tube bundle. The choice of different tube bundle combinations can significantly impact the overall performance of the heat exchanger. In this paper, a numerical study is conducted to examine the effects of two combination of circular and square tube bundle with the simple arrangement: i) circular, ii) square, on a shell and tube heat exchanger. COMSOL Multiphysics is employed to model and simulate this heat exchanger under various mass flow rates. The result shown that the combined geometry heat exchanger exhibits the highest overall heat transfer coefficient compared to heat exchangers with single arrangements. The pressure drop on the tube and shell side was also studied for all cases of heat exchangers. The placement of circular tubes in the center and near the shell has a significant effect on heat transfer and pressure losses. It has been demonstrated that the tubes located at the ends of the shell have a much greater impact on heat transfer compared to the tubes positioned in the center.

Исследование аэрогазодинамических процессов переноса радона из горных массивов

Introduction. Drying tailings are a source of gaseous chemicals, in particular radon222, which is carried by air currents along the slopes of the gorge. These processes need constant monitoring. Purpose of research. Establishment of climatic conditions most influencing the measurements of mountain radon and its dispersion in the atmosphere. Research methods and materials. The data of weather stations located in the Alagir mountain gorge and the data of the mathematical model of this gorge were used to establish the characteristic wind roses at the points of the gorge selected for field measurements of mountain radon. Research results. It has been established that at the nearby points of the mountain gorge, the prevailing direction and strength of the wind can differ significantly. The differences depend on the landscape features of the surface of the slopes of the mountain gorge. This factor determines the direction of migration of chemical elements and decay products of mountain radon. This conclusion is confirmed by direct measurement of wind speed at two points in the gorge, as well as by the results of mathematical modeling. Discussion of research results. A preliminary calculation of the passive impurity concentration field within the mountain gorge shows the most characteristic places on the slopes of the gorge from the point of view of measurements. Preliminary algorithm for choosing the location of measurements. Determination of 210Pb content in natural «traps» or sediments can determine the migration paths of «mountain» radon and estimate the magnitude of its interaction with the nature of the gorge, subject to the following assumptions: 1) certain sampling sites are not subject to significant seasonal disturbances; 2) natural and climatic conditions, especially the amount of precipitation, in the studied gorge should not have abnormal changes before sampling; 3) sampling should preferably be carried out in autumn on fallen leaves in hollows, where post-sedimentary migration is limited. Approbation of the proposed measurement technique is discussed. Conclusion. The prevailing winds in the side arms of mountain gorges can differ significantly from the wind rose observed in the main part of the gorge and are determined mainly by landscape features near the observation point. This must be taken into account when measuring and analyzing the direction of migration of chemicals in mountain gorges. Mathematical modeling of aerodynamic processes in mountainous regions is a proven method for studying physical processes in mountain gorges, as well as the processes of dispersion of volatile geochemical elements emitted by sources in mountain gorges. It is shown that at the nearby points of the mountain gorge, the wind roses can differ significantly, which is confirmed by both measurements and mathematical modeling. This dictates the need for observations and taking into account the local wind rose at each measurement point. The results of radon measurements are presented, confirming the effectiveness of the proposed technique. Resume. 1. The article presents the results of mathematical modeling of aerodynamic processes in mountain gorges and the spread of gaseous impurities in the air. 2. It has been established that wind roses at nearby points on the slopes of a mountain gorge can differ significantly, both in the results of the mathematical model and in the results of measurements from weather stations. It is shown that the agreement between the modeling and measurement results is satisfactory. 3. The research results can be useful in planning measurements of radon concentrations as a predictive map of the distribution of mountain radon concentrations.

Thermally stimulated exoelectron emission from the surface of black aluminum layers prepared by PVD methods

There is an increasing trend in the utilization of highly nanostructured materials, especially as light absorbers or chemical gas sensors. However, for most applications a more detailed study of surface processes and phenomena is necessary or at least highly beneficial.The present paper describes the surface processes of black aluminum prepared by different PVD methods (magnetron sputtering at room and liquid nitrogen temperature, and thermal evaporation) studied by thermally stimulated exoelectron emission. The actual investigation of the interaction between surface and adsorbed atoms and molecules was carried out after UV irradiation. For the samples prepared in this way, thermostimulated exoelectron emission was measured in the temperature range: liquid nitrogen temperature to 400 °C. SEM analysis revealed significant differences in the morphology of the layers, which were associated with a change in the position of the maxima in the thermostimulated exoelectron emission spectra.The activation energies for the electron emission were calculated. The binding process on the surface of the individual samples and their dependence on the type of black aluminum thin film preparation were described.The results could determine which type of thin film preparation is suitable for use as chemical gas sensors.

Gut Microbiome, Bone Health, and Air Pressure: Construing the Axis for the Proposed Triad

Joint pain is common when there is a change in weather. Mostly, cloudy weather is associated with back pain and knee joint pain. Atmospheric pressure plays a shrouded role in inducing and regulating joint pain. Bones are the densest organs of the human body, and that is why it becomes interesting to see the effect of low-density air pressure on such high-density organs. HIF is one factor involved in air pressure sensing, but how it communicates the signal to bones and the gut will be an interesting mechanism to decipher. The surrounding atmosphere also intervenes in the gut microbiome composition and eventually can change the chemistry of gases produced in the hindgut. IL-8, IL-6, and TLR-4 are a few of the signal-carrying molecules for the hindgut. In the manuscript, an attempt has been made to establish a signaling triad between the Gut, Bone, and the environment to formulate a hypothesis.

Instant Self‐Assembly of Functionalized MXenes in Organic Solvents: General Fabrication to High‐Performance Chemical Gas Sensors

AbstractMXenes are a promising class of two‐dimensional transition metal carbides, nitrides, and carbonitrides, widely utilized in diverse fields such as energy storage, electromagnetic shielding, electrocatalysis, and sensing applications. Their potential in chemical sensing is particularly noteworthy, where optimizing surface chemistry for strong interaction with target analytes and increasing surface area for efficient gas adsorption are crucial factors. In this study, a versatile and general self‐assembly method for fabricating nanometer‐scale thin films of surface‐functionalized MXene, enabling high‐performance gas sensors is developed. By dropping MXene dispersed in organic solvents onto nonsolvents, rapid formation of nanometer‐scale films is achieved. This method allows easy adjustment of film properties by using different solvent‐nonsolvent combinations, leading to improved optoelectronic properties compared to conventional techniques. The surface‐functionalized MXenes using ADOPA ligands greatly enhance the gas response and long‐term environmental stability compared to pristine MXenes. Computational methods are also employed to gain insights into the molecular interactions and changes in electronic structure that contribute to the enhanced sensing properties. Furthermore, the environmental stability of MXene sensors is largely enhanced after surface functionalization, which can be attributed to increased surface hydrophobicity. Overall, this innovative technique opens up opportunities for tailoring MXene thin films for specific applications.

Numerical solution for cross nanofluid flow in porous medium over stretching cylinder under MHD and radiation effects

AbstractThe aim of the present study is to analyze heat source in unsteady MHD nanofluid flow subjected to convective boundary conditions past a stretching cylinder incorporated with variable thermal properties. This study is significant in industries involving chemical processing, oil and gas, and manufacturing. The problem possesses a nonsimilar solution when similarity variables are utilized in transforming governing partial differential equations into ordinary differential equations. The numerical solution is found using MATLAB package bvp4c. The velocity, temperature, and concentration curves for various parameters are plotted graphically. The values for the coefficient of skin friction, heat transfer, and mass transfer rate are tabulated for the unsteadiness parameter, Weissenberg number, Prandtl number, Schmidt number, heat source/sink, thermal conductivity parameter, thermal and solutal Biot number, thermophoresis and Brownian parameter, radiation parameter, porosity parameter, and magnetic parameter. It is noted that, rise in porosity (–) and magnetic parameter (–) contributes to the decrease in velocity profile. It is found that, radiation effects help in incrementing rate of heat and mass transfer into fluid when radiation parameter ranges from to . Moreover, present results are in good agreement with the literature published in a limiting context.

Комплексное определение ресурса высоконагруженного промышленного оборудования

Comprehensive definition of the initial, current and residual life of industrial equipment of chemical oil and gas and other industries by strength criteria is considered in the article. The multi-criteria parameters of the technical condition and the development of diagnostic methods laid the foundations for complex forecasting of the initial, current and residual life of industrial equipment. For this indicators of corrosion, degree of wear, strength reserve, material defects and the eficiency of technical diagnostics were developed, which determine the technical condition of the equipment and its transition to the limit state. The initial state is established by the resource-strength studies during the manufacture of equipment and the initial resource is determined. By comparing the initial resource with the design one, the quality of equipment design is determined. At the end of the service life, technical diagnostics is carried out again, and resource-strength studies determine its actual technical condition, calculate the current resource and assign further operation of industrial equipment. At the end of the current resource, a subsequent diagnosis is carried out, and resource-strength studies determine the remaining resource. The proposed approach can set the resource of equipment for the entire technological complex at the request of the customer. A comprehensive method of resource determination can be used to improve regulatory documents for the design of equipment for chemical, oil and gas and other industries.

Fuzzy based self-tuned move lengths for enhanced performance of gas source localization algorithm

The world has witnessed a lot of catastrophes in recent times due to chemical gas leaks. The core problem is untimely or sudden happenings of calamity for which humans are not prepared to take appropriate actions. Hence robotic gas source localization can be considered as an alternative to prevent such catastrophes. This paper presents an improved approach to an existing chemotactic plume tracing algorithm with self-tuned move length/step size. The technique uses the proposed fuzzy inference model to produce the move lengths for the next walk based on the input of gas concentration magnitude in the present state. The move lengths correspond to either the plume finding or plume tracing stage with which a mobile robot surges for the next step. Dynamic plumes under eight different simulated environments are created to evaluate the proposed approach rather than plumes in laminar flow for a more realistic case. Performance analysis of the algorithm is based on success rate with self-tuned move length compared with fixed move length. In addition, there is an analysis of step size parameters that vary concerning a particular environmental condition. Results show that adaptive step size can increase the success rate of the plume tracing algorithm and consequently improve search performance and efficiency.

Improved deep bidirectional recurrent neural network for learning the cross-sensitivity rules of gas sensor array

Cross-sensitivity among chemical gas sensors leads to inaccurate identification of mixed gas. Pattern recognition algorithms are usually applied to improve the recognition accuracy. However, the abilities of current methods to process sequence property of response data are not strong enough. Especially, they cannot deal with bidirectional cross-sensitive issue, leading to recognition errors. Bidirectional Recurrent Neural Network (BRNN) could well learn bidirectional association features between word sequences in natural language processing field, which is similar to the bidirectional interaction of cross-sensitivity. In this study, an improved deep BRNN model was constructed to solve the cross-sensitivity problem of chemical gas sensor array. A chemical gas sensor array with four units was fabricated and response data was thoroughly obtained. Data preprocessing methods, model structure hyperparameters and optimizers were studied. Finally, an improved deep BRNN model was developed with 3 layers and 100 hidden_size, training with Adamax optimizer. A recognition accuracy of 98.93% was achieved, attributing to the model’s excellent learning ability to the bidirectional cross-sensitivity rules among gas sensors. This improved BRNN model provided a novel idea to eliminate cross-sensitivity, exhibiting good potential for recognizing mixed gas analyte accurately.

Development and application of a semi-detailed model for lithium-Ion battery thermal runaway chemistry

To overcome the disadvantages of detailed methodologies and existing simple methodologies for modeling lithium-ion battery thermal runaway chemistry, a semi-detailed model has been developed in the present work. This is important for mitigating battery thermal runaway. The semi-detailed model contains two parts: a ‘global part’ and an ‘elementary reaction mechanism part’. The thermal kinetics parameters of a recently published model are improved so that it can be selected for the ‘global part’ to model NCM811 (LiNi0.8Co0.1Mn0.1O2), NCM622 (LiNi0.6Co0.2Mn0.2O2), and NCM532 (LiNi0.5Co0.3Mn0.2O2). Temperature and heat release evolutions during battery thermal runaway can be obtained from the simulation of the ‘global part’. In the ‘elementary reaction mechanism part’, 53 reactions with frequency factors and activation energies have been proposed and adopted for describing flammable gas formation, lithium-ion consumption, gas phase interaction, and lithium-ion gas interaction during battery thermal runway. Detailed processes for coupling the ‘global part’ and the ‘elementary reaction mechanism part’ as well as solving the 53 reactions are developed, which is the major novelty of this work. Through the coupling of the two parts, chemical venting gas species generation and lithium-ion consumption during the transient thermal runaway process of an NCM811PC (LiNi0.8Co0.1Mn0.1O2 polycrystalline) pouch cell with nail penetration were calculated and compared with available experimental data in the literature. The comparison shows that the semi-detailed model can give correct species trends, indicating the two parts and their coupling in the semi-detailed model of the present work are reliable. The simulation results with transient venting gas chemical species provide useful insights for stopping or delaying battery thermal runaway.

Influences of thermochemical non-equilibrium effects on Type III shock/shock interaction at Mach 10

Shock/shock interactions (SSIs) often lead to high thermal loads. To understand the influences of thermochemical non-equilibrium effects on the Type III SSI, four gas models based on the assumption of thermal perfect gas (TPG), thermal equilibrium chemical non-equilibrium gas (TECNG), thermal non-equilibrium chemical frozen gas (TNCFG), and thermochemical non-equilibrium gas (TCNEG) are employed to simulate the Type III SSI at Mach 10. The intersection of incident shock and bow shock is determined by dimensionless intercept of 0.05 and 0.1. It is found that the chemical non-equilibrium effects significantly lift up the impingement position of shear layer by reducing the standoff distance of bow shock. As a result, the peaks of wall pressure and heat flux calculated by TECNG and TCNEG model are higher than TPG and TNCFG model, respectively. Type IIIa SSI occur in the flows calculated by the TECNG and TCNEG model for the case with a dimensionless intercept of 0.1. The peaks of wall pressure and heat flux calculated by TECNG model are both over four times higher than those of TPG model. The thermal non-equilibrium effects slightly increase the standoff distance of bow shock and lower the impingement position of shear layer. In addition, the thermal non-equilibrium reduces the angle to the horizontal direction of shear layer by increasing the specific heat ratio.

Detection of Volatile Organic Compounds (VOCs) in Indoor Environments Using Nano Quadcopter

The dispersion of chemical gases poses a threat to human health, animals, and the environment. Leaks or accidents during the handling of samples and laboratory materials can result in the uncontrolled release of hazardous or explosive substances. Therefore, it is crucial to monitor gas concentrations in environments where these substances are manipulated. Gas sensor technology has evolved rapidly in recent years, offering increasingly precise and reliable solutions. However, there are still challenges to be overcome, especially when sensors are deployed on unmanned aerial vehicles (UAVs). This article discusses the use of UAVs to locate gas sources and presents real test results using the SGP40 metal oxide semiconductor gas sensor onboard the Crazyflie 2.1 nano quadcopter. The solution proposed in this article uses an odor source identification strategy, employing a gas distribution mapping approach in a three-dimensional environment. The aim of the study was to investigate the feasibility and effectiveness of this approach for detecting gases in areas that are difficult to access or dangerous for humans. The results obtained show that the use of drones equipped with gas sensors is a promising alternative for the detection and monitoring of gas leaks in closed environments.

Remote Laser-Induced Breakdown Spectroscopy of Bacterial Growths in Carbonate Rocks in a Mars-like Atmosphere.

Understanding the past habitable environments of Mars increases the requirement to recognize and examine modern analogs and to evaluate the mechanisms that may preserve biosignatures in them. The phenomenon that originates and preserves possible microbial biosignatures in mineral phases is of particular interest in astrobiology. On Earth, the precipitation of carbonate matrices can be mediated by bacteria. Besides microbialites and other sedimentary structures, carbonate formations can be observed in certain karstic caves. The present work is focused on the remote laser-induced breakdown spectroscopy (LIBS) characterization of cyanobacteria, exploring the possibilities for identification and discrimination on carbonate substrates. For this purpose, the extremophile cyanobacterium Chroococcidiopsis sp. (collected from the Nerja Cave, Malaga, Spain) was analyzed under laboratory-simulated martian conditions in terms of chemical composition and gas pressure. LIBS results related to acquired molecular emission features allowed bacterial differentiation from the colonized mineral substrate. In addition, the limits of detection were estimated with a laboratory-grown culture of the cyanobacterium Microcystis aureginosa. Our results reveal LIBS's capability to detect biological traces under simulated martian conditions. Additionally, the time-resolved analysis of the biological samples demonstrates the selection of optimal temporal conditions as a critical parameter for the preferential acquisition of molecular species in organic material.