Concentrations Of Gas Components Research Articles

Thermodynamic simulation of hydrogen production from the nano-CaO reactive sorption enhanced biomass steam reforming

Based on the principles of thermodynamic reaction equilibrium, a simulation method enhanced by the nano-CaO reactive sorption CO2 for hydrogen production from biomass steam reforming has been established. MATLAB R2022b software has been utilized to calculate the composition concentration of the product gas. Detailed simulations have been conducted to understand the changes in gas component concentration and yield under various reaction conditions, includes temperatures, steam to biomass (S/B) molar ratios, and CaO to carbon (CaO/C) molar ratios. The result demonstrated that temperature plays a significant role in both the concentration and yield of hydrogen. At an optimal reaction temperature of 650 °C, the concentration of H2 in the product reaches 77% (S/B = 2 and CaO/C = 0.5). S/B molar ratio over 2 is necessary to increase the H2 concentration. The study also reveals CaO/C molar ratio 0.5 enable successful removal of CO2 generated by reaction. The application of nano-CaO notably enhanced the efficiency of hydrogen production from biomass steam reforming, leading to a 25% increase in H2 concentration and a boost in H2 yield to 50 mL/gBiomass, and reaction temperature decrease 200 °C compared to the case without CaO.

Experimental study of gas composition in the equilibrium state of a light alkane combustion reaction

Oil field-associated gas is typically a mixture of light alkanes. To ensure production safety, it is essential to investigate the combustion characteristics and the reaction mechanism of light alkane gas mixtures to uncover the underlying mechanisms of the combustion reaction. This paper investigates the equilibrium gas component concentrations resulting from the reaction of a gas mixture of methane, ethane, and propane at specific ratios through experimental tests. The study's results demonstrate that the equilibrium concentrations of methane, ethane, and propane initially decrease and then increase with the rise of the equivalence ratio under the same initial pressure conditions. In oxygen-poor conditions, the equilibrium concentration ratio of methane gradually increases in proportion to the equilibrium ratio, confirming that ethane and propane are the preferred participants in the reaction. Furthermore, a study of the equilibrium concentration of the critical intermediate product, ethylene, revealed that it does not completely oxidize in the combustion reaction. It can persist under both oxygen-rich and oxygen-poor conditions, with an equilibrium concentration of approximately 0.02%. The findings of this paper can serve as a theoretical supplement to the research on explosive gas combustion and explosions.

Numerical simulation of altering the raw meal inlet position in a novel swirl precalciner

Conducted a numerical simulation to model a novel swirl precalciner, investigating how altering in the position of the raw meal inlet affects the internal gas flow, temperature field, and component concentration field within the precalciner. Applied the Realizable k-? two-equation turbulent model to the continuous phase. For the particle phase (pulverized coal), employed the Discrete Particle Model and the discrete random walk model. Simulated the combustion of pulverized coal and the decomposition of calcium carbonate by using the Species Transport model combined with the Finite-Rate/Eddy-Dissipation model. Modeled the generation of NOx using a NOx model. The results show that, in comparison to the condition with four raw meal inlets, the six raw meal inlets condition has a better coupling of pulverized coal combustion and raw meal decomposition. The decomposition rate of raw meal has seen a slight improvement, and there is a significant improvement in the occurrence of localized high temperatures within the precalciner, resulting in a reduction of the outlet NOx concentration from 1251 ppm to 225 ppm.

Methanol infrared spectral characteristics in offshore gas logging

Methanol infrared spectral characteristics in offshore gas logging. Methanol was found in the logging gases during offshore gas logging by infrared spectra. Logging gas spectra from over 300 offshore wells and 1,000 onshore wells were processed and analyzed, and methanol characteristics were prevalent in the offshore logging gases but not onshore logging gases. The spectra of instruments Alpha111829 and Alpha111834 are studied as examples. The methanol concentrations in some areas exceeded 1 vol%, seriously interfering with the other measurements of alkane gases. Moreover, there are rapid changes in the trends of methanol concentrations. It indicates that methanol does not originate from drilling fluid additives. The results of the correlation analysis show that there are no strong correlations between methanol and the other logging gas component concentrations. Therefore, methanol may be neither a judgmental indicator component gas for natural gas nor oil but a separate energy source. We believe methanol in the offshore logging gases originates from strata. The discovery and analysis of methanol in offshore logging gases are significant in atmospheric and marine environments, oil and gas exploration, geochemistry, and energy.

Experimental study on the displacement effect and inerting differences of inert gas in loose broken coal

The pre-injection of inert gas before coal self-ignition is a common key measure for preventing and controlling spontaneous coal combustion in a goaf. Previous studies have mainly considered inerting to reduce the concentration of ambient gas components and explored the influence of oxygen or inert gas concentration on the inerting effect of loosely broken coal, but seldom considered the replacement of oxygen by an inert gas, especially the replacement of adsorbed oxygen. Here, we quantitatively investigated the difference in room-temperature inerting of loosely broken coal by N2 and CO2 by conducting one-factor experiments on replacing oxygen in coal with an inert gas at room temperature and pressure. The results reveal that the replacement process can be divided into three stages and that the different adsorption capacities of coal for N2 and CO2 are the main reasons for the asynchrony of each replacement stage. The stronger the adsorption capacity, the stronger the displacement of adsorbed oxygen in the adsorbed state by the inert gas. CO2 exhibits an inerting strength 2.3–2.6 times higher than N2 and 5.7–8.8 times higher than He. The experiments also revealed that optimizing the key parameters of inert fire protection technology should consider the adsorption effect.

Study of the effectiveness of diagnostic method for respiratory system diseases by analyzing the exhaled air using a gas analytical complex

Aim: To study in patients the dependence of the exhaled air composition on pathological processes occurring in the respiratory system, including: lung cancer, community-acquired pneumonia and COVID-19.Material and Methods. The studies were carried out on the basis of a gas analytical complex using the method of neural network data analysis. The gas analytical complex includes semiconductor sensors that measure the concentrations of gas components in exhaled air with an average sensitivity of 1 ppm. Based on signals from sensors, the neural network classifies and identifies patients with certain pathological processes.Results. The statistical data set for training the neural network and testing the method included samples from 173 patients. Our study collected exhaled air samples from groups of patients with lung cancer, pneumonia, and COVID-19. In the case of lung cancer, the parameters of the diagnostic device have been determined at the level of sensitivity – 95.24%, specificity – 76.19%. For pneumonia and COVID-19, these parameters were 97.36% and 98.63, respectively.Conclusion. Taking into account the known value of diagnostic methods such as computed tomography (CT) and magnetic resonance imaging (MRI), the sensitivity and specificity indicators of the gas analytical complex achieved during the study reflect the promise of the proposed technique in the diagnosis of tumor processes in patients with lung cancer, COVID-19 and community-acquired pneumonia.

Research on an Ultraviolet Spectral Denoising Algorithm Based on the Improved SVD Method

The utilization of ultraviolet (UV) absorption spectroscopy for monitoring the concentration of specific decomposition gas components in gas-insulated switchgear (GIS) can provide a means to assess its insulation status. Nevertheless, UV optical modules currently deployed in the field are susceptible to external interferences like ambient noise and equipment vibrations. Real-time spectral data acquisition often suffers from significant noise contamination, directly impinging on subsequent feature extraction and detection accuracy. This paper presents an optimized singular value decomposition (SVD) noise reduction method for mitigating noisy spectral signals. First, each singular value within the noisy signal is transformed into a component signal. Next, the highest frequency value in the signal serves as an indicator to characterize the signal. Finally, the primary frequency values are arranged based on the decreasing singular values of the original noisy signal. The singular value corresponding to the first primary frequency value surpassing a preset threshold is selected as the effective order for denoising. Random noise with varying intensities was intentionally introduced to the UV spectral signal of sulfur dioxide (SO2), followed by noise reduction procedures. It is shown that the improved SVD noise reduction algorithm proposed in this paper enhances the signal-to-noise ratio (SNR) by 18.02% and 16.86%, and reduces the root-mean-square error (RMSE) by 15.13% and 14.92%, respectively, compared with the singular value difference spectrum (SVDS) denoising method and wavelet transform denoising method under the condition of low SNR. Furthermore, there exists a linear relationship between the concentration of SO2 samples and the eigenvalues of the UV spectra, demonstrating a higher linear goodness with a coefficient of 0.99735. The denoising method proposed in this paper does not require the manual setting of various types of parameters, and has a better ability to deal with the noise of UV spectral signals in engineering sites with complex environments.

Quartz-Enhanced Photoacoustic Spectroscopy Assisted by Partial Least-Squares Regression for Multi-Gas Measurements.

We report on the use of quartz-enhanced photoacoustic spectroscopy (QEPAS) for multi-gas detection. Photoacoustic (PA) spectra of mixtures of water (H2O), ammonia (NH3), and methane (CH4) were measured in the mid-infrared (MIR) wavelength range using a mid-infrared (MIR) optical parametric oscillator (OPO) light source. Highly overlapping absorption spectra are a common challenge for gas spectroscopy. To mitigate this, we used a partial least-squares regression (PLS) method to estimate the mixing ratio and concentrations of the individual gasses. The concentration range explored in the analysis varies from a few parts per million (ppm) to thousands of ppm. Spectra obtained from HITRAN and experimental single-molecule reference spectra of each of the molecular species were acquired and used as training data sets. These spectra were used to generate simulated spectra of the gas mixtures (linear combinations of the reference spectra). Here, in this proof-of-concept experiment, we demonstrate that after an absolute calibration of the QEPAS cell, the PLS analyses could be used to determine concentrations of single molecular species with a relative accuracy within a few % for mixtures of H2O, NH3, and CH4 and with an absolute sensitivity of approximately 300 (±50) ppm/V, 50 (±5) ppm/V, and 5 (±2) ppm/V for water, ammonia, and methane, respectively. This demonstrates that QEPAS assisted by PLS is a powerful approach to estimate concentrations of individual gas components with considerable spectral overlap, which is a typical scenario for real-life adoptions and applications.

Methods to investigate the temperature distribution of heated ceramic gas sensors for high-temperature applications

Abstract. The temperature-dependent properties of sensor films for measuring the concentration of various gas components affect, to a large extent, the sensor characteristics of planar gas sensors. Therefore, it is important to know the temperature distribution of the gas-sensitive films of such sensors precisely. Using screen-printed thermocouples and a thermal-imaging camera, two principles for determining the temperature profile of gas sensors inside of a protection cap are shown and compared in this study. The data agree well, and the results can be used in future to determine the influences of varying flow and temperature conditions on the temperature profile of a sensor and to reduce such effects by adapting the periphery, e.g., by designing appropriate protection caps.

Combustion behaviour of plastic waste – A case study of PP, HDPE, PET, and mixed PES-EL

Plastic production is skyrocketing due to convenience needs and thus, the amount of plastic waste is increasing. There are several different methods to handle plastic waste, within which waste-to-energy processes are viable options in certain settings. However, the combustion of materials is a complicated and complex process that can take place in a number of ways. When exposed to heat, different polymers behave differently (e.g. have different emission factors) and thus, not all types of plastic waste recommended to be handled through combustion. Therefore, it is vital to achieve a deeper understanding of these processes in order to decide on the end use of plastic materials. Four common types of polymers were studied: polypropylene (PP), high-density polyethylene (HDPE), polyethylene terephthalate (PET), and polyester-elastane (PES-EL) mixture. The combustion properties of the plastic materials were investigated. The experiments were carried out in a laboratory electric resistance tube furnace at two different temperatures (650 and 900 °C). The behavior of these mainly single-use plastic wastes and the changes in the concentrations of CO, CO2, NOx, and O2 flue gas components generated during combustion was studied to determine the quality of potential waste-to-energy processes.

GEOCHEMICAL PATTERNS OF DISTRIBUTION OF DISPERSED GAS COMPONENTS IN THE SHALLOW SUBSURFACE OF WEST SIBERIA

Despite the modern trends for the decarbonization of power engineering, transportation, and industry, fossil fuels remain in high demand. On the other hand, the gas and oil industries are also interested in energy efficiency and reduced environmental impact. Drilling of the wells is one of the most environmental danger processes, and reducing the number of wells is an important task that also provides an increase in the overall energy efficiency of the oil/gas mining technological process. Deposit exploration is a necessary part of the petroleum mining industry that determines the presence of fuel resources. The reliable and fast identification of the oil/gas deposits allows for a decrease in the number of drilled research holes. The authors of this article investigated the depth distribution of the hydrocarbon and non-hydrocarbon components of dispersed gas sampled from the cores of West Siberia shallow wells to quickly refine the boundaries of the layers using a priori information in the form of geochemical correlation. The correlations were established based on the amount of methane, the sum of homologs of methane, hydrogen, and olefines. The results show a decrease in the concentrations of gas components at the boundaries of layers with different lithologies. The term "geochemical seal" is introduced to describe such a phenomenon.

Insights into the gas sensor materials: Synthesis, performances and devices

Recently, the intelligent, smart gas sensing devices have shown great prospects in applications of gas component recognition and concentration detection, which largely depends on the precise structures and compositions of sensing layers. Various synthetic strategies are promising for the scalable production and performance optimization of the sensing materials. In this review, different gas sensing materials with controlled preparation such as wet-chemical synthesis, electrospinning method, vapor-phase synthesis and exfoliation routes are summarized. Then, the representative design strategies and gas sensing performances in gas sensors are also discussed. Finally, the recent progress of some gas sensing devices is presented, with the emphasis on their device structure, circuit design, and applications. It is believed that this review will provide some guidelines for designing novel gas sensing materials with controllable synthetic methods and sensing behaviors for advanced gas sensors.

A Thermal-Hydrological-Mechanical-Chemical Coupled Mathematical Model for Underground Coal Gasification with Random Fractures

In this paper, in order to understand the development process and influencing factors of coal underground gasification, taking the two-dimensional underground gasification area of the plane as the simulation object, the characteristics of the multi-physical field coupling process of exudate mass heat transfer and combustion gasification reaction in the process of horizontal coal seam underground gasification are analyzed, and a two-dimensional mathematical model of thermal-hydrological-mechanical-chemical coupling of a porous medium is established. The temperature distribution of coal rock from the gasification point, the distribution of gas water vapor pressure and stress-strain, the temperature contour distribution of fractured coal rocks of different densities of heterogeneity, and the influence of different water-oxygen ratios and different fractured coal rocks on the gas components generated by the gasification reaction were studied. The results show that the tensile damage caused by the tensile strain volume expansion of the coal underground gasification center, the shear damage caused by the compression of the edge compressive strain volume, and the temperature conduction rate decrease with the increase in the coal rock fracture, but in the heterogeneous coal rock, the greater the fracture density, the faster the temperature conduction rate, which has a certain impact on the gasification combustion reaction. The ratio of CO2, H2 and CO in the case of simulating that the water-to-oxygen ratio is 1:2, 1:1, and 2:1 is 1:0.85:0.73, 1:1.1:0.97, and 1:1.76:1.33, respectively. At a water-oxygen ratio of 2:1, the concentration ratio is the most ideal, and the main gases, CO, CO2, and H2, are 32%, 21%, and 37%. Furthermore, the reaction rate increases with the increase of fracture density. The gas component concentration simulated in this paper has good consistency with the results of the previous experimental data, which has important guiding significance for the underground coal gasification project.

Influence of Compartment Fire Behavior at Ignition and Combustion Development Stages on the Operation of Fire Detectors

This paper presents experimental research findings for those involved in the early phase of fire in office buildings. Class A model fires with a reaction area from 5 cm2 to 300 cm2 were chosen for investigation. To mock up a fire, the following combustible materials typical of offices were used: wood pieces, heat-insulated linoleum, paper and cardboard. The main characteristics of a model fire were recorded: temperature in the combustion zone, heat release, time of complete burnout and concentration of flue gas components. Typical trends and histograms of changes of these characteristics over time were presented; stages of ignition, flame combustion and smoldering were illustrated. The key characteristics of fire detector activation at different stages of model fire combustion were analyzed. Dead bands and operation conditions of a group of detectors (smoke, heat, optical, flame), their response time and errors were identified. It has been established that the most effective detectors are flame and smoke detectors. Specific operational aspects of detectors were established when recording the ignition of different types of model fires. The viability of combining at least two detectors to record fire behavior was established. Recommendations were made on using the obtained findings when optimizing the systems for detecting and recording the start of a compartment fire.

Investigation of the co-firing of natural gas and RDF in a model combustion chamber**

The production and utilization of fuel derived from municipal solid waste (RDF/SFR) is an effective method for saving organic fuel and decreasing emissions of harmful substances and greenhouse gases at landfill and refuse dumps. Ukraine has a potential for the production of 1.5–2 million tons of RDF/SFR with a calorific value of 10–25 MJ/kg annually. In the case of involving these fuels to power sector, about 2500 GW-h of electricity and 4500 GW-h of heat can be produced annually. One of the promising variants to involve RDF/SFR to power sector is their combustion, including co-firing with natural gas, aimed at the production of heat and electricity, in particular, using the existing boilers of small and middle steam capacity in compliance with stringent ecological requirements (Directive 2010/75/EU etc.).
 For performing this investigation, we chose a GMP-16 gas-and-oil-fired burner, mounted into a cylindrical combustion chamber. The gas-and-oil-fired hot-water boilers of KVGM grade, designed for heating and hot water supply, are equipped with burners of this type. In computer modeling, we determined the influence of RDF additions on the co-firing with natural gas for a given geometry of the combustion chamber components (with a burner of 18.6 MW heat output). We obtained calculated dependences of temperatures, velocities, distributions of gas component concentrations, carbon remained in the solid phase, as well as the concentrations of nitrogen oxides and carbon monoxide over the combustion chamber. According to preliminary assessments, we established that additions of up to 20% RDF/SFR (by heat at input) in their co-firing with natural gas will not change substantially the technical and ecological parameters in operation of the combustion chamber.

EFFECT OF MOISTURE ON NITROGEN DIOXIDE FORMATION IN LAMINAR FLAME OF NATURAL GAS

The paper contains the results of experimental studies of the effect of moisture on nitrogen dioxide formation and on oxidation of NO to NO2 in laminar premixed flame of natural gas. The water vapor is shown to be the third very influential participant, along with fuel and oxidizer, in the combustion process. Injection of moisture into the combustion zone has an effect due to the insertion of additional quantities of HO2- and OH– radicals into the process, which contributes to the intensification of the oxidation of NO to NO2. Introduction of the concept of the “excess moisture ratio” in the combustion process is proposed. The studies were executed at the laboratory installation in conditions of formation of the V-shaped laminar flame of natural gas behind a transverse cylindrical steel stabilizer, with determining the concentrations of flue gas components.

The emission of harmful compounds from the marine diesel engine fueled by a blend of n-butanol and marine fuel

The use of renewable fuels may be an action leading to the reduction of pollutant emissions. This group includes biobutanol as a product of biomass fermentation. Some of its physicochemical properties, including the ability to mix with hydrocarbon fuels, make it suitable for use as a fuel component for marine diesel engines. The article presents the results of research on the concentration of exhaust gas components of a Sulzer 6AL20 / 24 diesel engine powered by a mixture of n-butane and diesel oil. The emission intensity were calculated for the tested components: carbon monoxide, carbon dioxide and nitrogen oxides. The emission intensity surface graphs were created based on the calculated data. The tests were carried out using different concentrations of the mixture of n-butanol and marine fuel.

Research on Underground Chemical Gas Monitoring and Target Location Based on an Improved Moth Flame Algorithm

The danger of downhole work is mainly due to the chemical toxic gases and flammable gases NO2, CO, SO2, H2S, CH4, CO2, etc. When the concentration reaches a certain value, it will produce very great harm. With the continuous development of sensor technology and communication technology, it is necessary to monitor the relevant geographic features below the ground. Because of the complex environmental parameters of the coal mine roadway and the interference caused by various electrical equipment, the transmission of mine electromagnetic signals will be affected, resulting in low positioning accuracy. However, the underground chemical gas leakage leads to the life of underground workers which cannot be guaranteed, so it is necessary to effectively monitor the concentration of chemical gas components in underground mines. In this paper, a moth flame algorithm based on optimized inertia weights is proposed. By continuously improving the local inertia weights, the global optimum is determined by using the change of inertia weights in the iterative process of the algorithm. By testing the convergence and optimal value of several algorithms under common test functions, IMFO can obtain the global optimal solution. Finally, the concentrations of chemical gases NO2, CO, SO2, H2S, CH4, and CO2 are monitored by setting specific areas to see if they reach the early warning values. Then, 16 coordinates in the region are used to predict the above method, and the IMFO algorithm can achieve the best prediction effect.

Experimental study on the backdraft phenomenon of solid fuel.

In this study, a series of small-scale experiments were conducted to investigate the backdraft phenomenon in a compartment (1.1 × 0.4 × 0.75 m) with woodblocks as fuel. This research focused on the effects of compartment window woodblock areas on backdraft time, with a video recording of the experimental phenomena. Thermocouples and a gas analyzer were used to measure the temperature and the concentration of gas components in the compartment, respectively. There was no additional heat source or ignition source pre-set in the compartment at the beginning of the experiments; the experimental processes only depended on the heat released from the burning or smoldering of woodblocks. When compartment ventilation improved, smoldering of woodblocks became intense, and backdraft occurred. The results show that backdraft time is shorten with increases of compartment window and woodblock areas, and opening the upper window of a compartment could avoid the backdraft phenomenon. The results help to understand the backdraft phenomenon of solid fuel and, more importantly, could help firefighters adopt reasonable fire-fighting strategies for restraining backdraft occurrence.

Effects of methane addition on laminar flame characteristics of premixed blast furnace gas/air mixtures

As a typical low heating value fuel, blast furnace gas (BFG) is used as an alternative fuel for gas turbine combustion. Due to its high concentration of inert gas components, natural gas is usually added to improve ignition and stable combustion in the combustion chamber. In this paper, laminar flame characteristics of BFG/CH4/air mixtures were investigated using constant volume combustion chamber and CHEMKIN package using the Gri-Mech 3.0 model. Experiments and numerical simulations were conducted at an elevated pressure and temperature of 0.2 MPa and 453 K, equivalence ratios of 0.8–1.4, and mixing ratios of methane of 0, 5, 10, 15%. The results show that the laminar burning velocity decreases rapidly from 24.19 cm/s to 13.90 cm/s at ϕ = 1.4 with the increase of methane addition from 0% to 15%, but obviously increases from 16.49 cm/s to 28.68 cm/s at ϕ = 0.8, from 21.05 cm/s to 35.65 cm/s at ϕ = 1.0, from 23.52 cm/s to 32.09 cm/s at ϕ = 1.2 with the increase of methane addition from 0% to 15%. Meanwhile, methane addition has an opposite effect on the Markstein length at ϕ = 0.8–1.2 and ϕ = 1.4. The thermal, transport and chemical effects were examined, exhibiting a major role of the thermal effect in the range of ϕ = 0.8–1.2 and a significant contribution of the chemical effect at ϕ = 1.4 to the laminar flame propagation of BFG/CH4/air mixtures. Further sensitivity analysis shows that R38 (H + O2 ↔ O + OH) and R52 (H + CH3 (+M) ↔ CH4 (+M)) are the main chain branching and chain termination reactions, respectively. Analysis on flame structure indicates that concentrations free radicals, especially OH and H evidently increase with methane addition. The maximum mole fraction of OH increases almost linearly from 1.02×10-3 to 3.82×10-3 with the increase of methane addition from 0% to 15%. The maximum mole fraction of H increases with a lower gradient than that of OH from 1.31×10-3 to 2.89×10-3 with the increase of methane addition from 0% to 15%.