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This work presents an unconventional use of capacitively coupled contactless conductivity detector (C4D) for detection of gas absorption by moist paper with potential application for chemical analysis. To be suitable for measuring conductivity of moist paper absorbent, the C4D sensor was therefore designed in planar configuration. A layer of dry filter paper, only 20 mm × 25 mm in size, was placed on the C4D sensor and the device installed inside a specifically designed vaporization chamber. A vial (16 mm i.d., 8 mm high) containing a 150-μL solution of sodium bicarbonate was placed alongside. The filter paper was loaded with 110 μL of deionized water through an injection hole in the cover lid. A 100-μL aliquot of 2 M hydrochloric acid solution was directly dispensed into the vial through a second hole in the lid to generate CO 2 gas from the bicarbonate solution. It was observed that the C4D sensor gave real-time response that corresponded to the absorption of the gas and subsequent production of H+ and HCO 3 − in the moist paper. The monitored signal reached a constant value at 160 s after the addition of the acid. Chemistry of the absorption process and equivalent circuit for the C4D are proposed. Direct measurement of cement powder was chosen to demonstrate the potential use of this device for quantifying the CaCO 3 content of the cement. The calibration curve for 0.5–3 mg CaCO 3 was linear for signals recorded at 160 s: V dc = (0.172 ± 0.005) · (mg CaCO 3) + (0.016 ± 0.009), with coefficient of determination of 0.9965. Linear calibrations were also observed when the signals were monitored at various time less than 160 s. The limit of quantitation (3 SD of intercept/slope) was 0.17 mg CaCO 3. The method provided acceptable precision with %RSD of 4.6 (2 mg CaCO 3 , n = 10). Image 1 • Unconventional use of planar contactless conductivity detector is presented. • Real-time in-situ detection of CO 2 absorption by moist paper was demonstrated. • The absorption chemistry by moist paper and C4D equivalent circuit are proposed. • Potential application in direct measurement of cement powder is demonstrated. [ABSTRACT FROM AUTHOR]

In this study, a novel cellulose nanocrystal/metal-organic framework composite (MC) was developed as a stabilizer for alkenyl succinic anhydride (ASA) Pickering emulsions, demonstrating remarkable sizing performance and antimicrobial properties for advanced food packaging applications. The MCs exhibited superior emulsion stabilization capabilities compared to pure metal-organic frameworks, with the optimum MC concentration identified as 1.0 wt% CNC. The hydrophobicity of the sizing paper was found to be enhanced with increasing CNC content. The MC-ASA sized paper demonstrated commendable storage stability, robust gas adsorption, and resistance to water vapor or water droplets. The MCs-ASA sized paper showed excellent food preservation efficacy, maintaining the freshness of strawberries for up to seven days, compared to ASA-sized paper without MCs. The antimicrobial assays targeting Escherichia coli and Staphylococcus aureus highlighted the intrinsic antimicrobial properties of the MCs, contributing to the extended freshness of the encased strawberries. The water vapor barrier efficacy and water retention capabilities of MCs-ASA sized paper were found to be superior to those of the paper without MCs, emphasizing the potential of the developed composite as an innovative and effective food packaging solution. This study offers valuable insights into the synthesis and implementation of CNC/MOF composite particles for versatile applications in food packaging, water-resistant materials, and environmental protection. [Display omitted] • CNC/MOF composites boost ASA Pickering emulsions' sizing performance. • MCs elevate hydrophobicity, gas adsorption, and sizing paper stability. • MCs-ASA paper extends strawberry freshness to 7 days in food packaging. • Research paves way for sustainable, eco-friendly advanced packaging solutions. [ABSTRACT FROM AUTHOR]

A novel method has been developed for the determination of the diffusion ( D ) and solid–air partition ( K d ) coefficients of methanol in paper materials. The method used a solvent-assisted vapor absorption based headspace analysis technique to increase the driving force of the mass transfer process in the solid phase. Equations based on the established physical models described the process allowed the calculation of D and K d of methanol in paper materials from the GC signals and experimental settings. The results showed that the amount of methanol transferred from the paper sheet can be significantly increased by the presence of the assisting triacetin. The solvent-assisted vapor absorption equilibrium can be obtained in 20 min. The method also generated equations allowing for the calculation of D and K d of methanol in paper materials at any temperature. The present method is simpler and quicker than the chamber methods that are in widespread use today and should be of special interest to those concerned about the impact of food and beverage packaging on human health. [ABSTRACT FROM AUTHOR]

In this study, preparation of a nylon film–TiO 2 composite sheet with both physical durability under UV irradiation and TiO 2 photocatalysis functionality was investigated. First, a nylon film was directly prepared on paper by interfacial polymerization using ethylenediamine and terephthaloyl chloride in a cyclohexane–chloroform mixture (3:1, v/v). Next, the nylon-coated paper was treated with tetraethyl orthosilicate and 3-aminopropyltrimethoxysilane to prepare polysiloxane on its surface. This was followed by fixation of TiO 2 powder via electrostatic interactions with the polysiloxane. Although nylon films on paper usually decompose under TiO 2 photocatalysis, the nylon film–TiO 2 composite sheets prepared using 0.5%–1.0% (w/v) TiO 2 did not decompose under photocatalysis. The residual rate of strength of the sheet remained at almost 100% after 240 h, which could be attributed to protection of the sheet by the polysiloxane layer. The nylon film was fibrous and could effectively adsorb acetaldehyde gas. All of the nylon film–TiO 2 composite sheets prepared using 0.5%–5.0% TiO 2 photocatalytically removed acetaldehyde under UV irradiation and no acetaldehyde gas was detected after 240–300 min. These results show the nylon film–TiO 2 composite sheet can effectively remove acetaldehyde gas by photocatalysis and adsorption and could be applied to removal of volatile organic compounds in indoor air. Image 1 • A nylon film is directly prepared on paper using interfacial polymerization. • The nylon can adsorb acetaldehyde gas. • Polysiloxane is coated on the nylon by electrostatic interactions and fixes TiO 2. • The nylon film–TiO 2 composite sheet is durable under TiO 2 photocatalysis. • The nylon film–TiO 2 composite sheet is photocatalytic. [ABSTRACT FROM AUTHOR]

Abstract: Single-walled carbon nanotube (SWCNT) and multi-walled carbon nanotube (MWCNT) membranes (buckypaper) and carbon nanofiber (CNF) paper were incorporated onto the surface of epoxy carbon fiber composites, as proposed fire shields. Their flammability behaviors were investigated by a cone calorimeter. SWCNT buckypaper and CNF paper did not show notable improvement on fire retardancy. However, MWCNT buckypaper acted as an effective flame-retardant shield, reducing the peak heat release rate by more than 60% and reducing smoke generation by 50% during combustion. The pore structures of buckypapers and CNF paper were characterized by scanning electron microscopy (SEM), mercury intrusion porosimetry, and N2 adsorption isotherms. Gas permeability of buckypaper and carbon nanofiber paper was measured. The correlation between buckypaper and CNF paper properties and their fire retardancy was discussed. [Copyright &y& Elsevier]

In the accident conditions, the operational behavior of passive autocatalytic recombiners (PARs) has garnered significant attention, particularly with regards to the complicated atmosphere in the containment. This paper aims to systematically study and analyze the PAR performance under post-accident conditions. CFD simulation resolving individual catalytic channels of PARs provide valuable insights into hydrogen consumption performance and temperature distribution. A simplified model of PARs, consisting of a gas channel and two catalyst plates, was developed using the CFD software STAR-CCM+. One-step reaction mechanism was used in this model to define the hydrogen consumption rate on the catalytic surface. To study the variation in gas concentration and temperature distribution, physical values of interest were extracted from designated locations. An analysis of catalyst section was conducted to provide a comprehensive understanding of the reaction process occurring within PARs. Subsequent tests were conducted using the developed simplified model to examine the effect of inlet gas components variation and operating conditions on PAR performance under post-accident conditions. Our findings show that the variation of steam concentration primarily alters the heat absorption capacity of the gas mixture, rather than the catalytic reaction rate. Furthermore, inlet velocity and operating pressure play a role in controlling the inlet mass flow rate, thereby influencing the reaction process of the gas channel by introducing varying amounts of hydrogen. • An analysis of catalyst section behavior in passive autocatalytic recombiners. • Examinations of different inlet gas components and operating conditions. • Hydrogen concentration and gas temperature directly change the reaction rate. • Steam concentration mainly alters the gas heat absorption capacity. • Inlet velocity and operating pressure control the inlet mass flow rate. [ABSTRACT FROM AUTHOR]

• Particle affects the output laser intensity and absorbance received by detector. • Extinction of particles can be represented by the slope of output laser intensity. • Exact measurement of gas concentration can be realized in the presence of particles. Tunable Diode Laser Absorption Spectroscopy (TDLAS) technology is widely used for monitoring the gas pollutants. But in actual measurement environments, there are usually particles, which will affect the TDLAS direct absorption spectroscopy. In this paper, the influence of particles on the direct absorption spectroscopy of TDLAS was analyzed by using TDLAS-DAS technology combined with particle extinction method. According to analysis, it was found that the presence of particles does not affect the gas characteristic absorption spectral line strength and the gas absorption spectroscopy broadening, but it does affect the output laser intensity and absorbance received by the detector. The transmittance of particles can be obtained through the slope of the output laser intensity, which can be used to correct the absorbance to achieve accurate measurement of gas concentration. This paper analyzed the effects of particle size, incident wavelength, and composition on particle extinction coefficient and obtained the extinction coefficient of soot. If the laser wavelength is 1.53 μm and the particle size of soot is 45 μm, the extinction coefficient of soot is 2.1016. The magnitude of laser intensity attenuation at different particle concentrations can be obtained based on the extinction coefficient of particulate matter. When the concentration of soot is greater than 26290 mg/m3 and the optical path is 100 cm, the transmittance is less than 0.1 and the laser intensity attenuation reach over 90 %, which may affect the detection of gas absorption spectroscopy information and the accuracy of measurement. On this basis, this paper established the relationship between gas concentration and corrected absorbance to invert the gas concentration in the presence of particulate matter when the concentration of soot is less than 26290 mg/m3. The inversion gas concentration error obtained by the absorbance peak calibration method is within 3 %, and the inversion gas concentration error obtained by the absorbance integration method is within 1 %. From the inversion results, it can be seen that the accurate measurement of gas concentration in the presence of particulate matter can be achieved by extracting the slope of the output laser intensity to correct absorbance. [ABSTRACT FROM AUTHOR]

• The α -Fe 2 O 3 nanomaterials were prepared using a simple one-step hydrothermal method. • S1-250 sensor has a lower operating temperature (225 °C) and the highest response(88.47/100 ppm). • The long-term stability, selectivity and resistance to moisture of the S1-250 sensor were better than that of the S2-350 sensor. • The structure-activity relationship between material structure and gas-sensitive properties is studied to provide new ideas for the design of gas-sensitive materials. In different environments, high concentration of n-butanol will have certain harm to the human senses and nervous system, meanwhile the electrochemical sensor limits its widespread use due to its high power consumption, so it is very meaningful to develop a semiconductor n-butanol sensor with low energy consumption. In this paper, α-Fe 2 O 3 nanorods were prepared by one-step hydrothermal method and then assembled into a n-butanol sensor capable of detecting n-butanol, and the effects of two different calcination temperatures on the performance of the sensor were investigated. Due to its higher Fe3+ content, higher oxygen vacancy content and larger specific surface area, S1-250 provided more active sites for gas adsorption, which making the response of S1-250 to 100 ppm n-butanol at 215 °C reached to 88.4. Finally, the effect of the calcination temperature on the sensor and the response mechanism were discussed. This paper offers promising applications for low-energy n-butanol sensors assembled from a single material α −Fe 2 O 3. [ABSTRACT FROM AUTHOR]

Recent years, sensors based on perovskite nanomaterials have become one of the most interesting fields while their instability remains as one of the major obstacles for further advancement. In this work, for the first time, a facile and controllable strategy was proposed for in-situ growth of stable CsPbBr 3 nanocrystals in SiO 2 network on poly (vinylidene fluoride) membrane. The formation of SiO 2 network was triggered by the fast hydrolysis of (3-aminopropyl)triethoxysilane as the precursor. Characterization results including UV–vis, FTIR, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) indicate successful formation of CsPbBr 3 –SiO 2 nanocomposites. With the protection from SiO 2 network, the fluorescence intensity of CsPbBr 3 nanocrystals maintains 88.11% of initial intensity after 104 days in ambient environment and is stable during the humidity test (RH = 90%, for 30 min). CsPbBr 3 –SiO 2 nanocomposite based membrane can be applied as fluorescent sensors for NH 3 determination in high concentration range based on fluorescence quenching, which shows good linearity, accuracy, precision, and specificity toward NH 3 over common organic vapors. [Display omitted] • With the protection from SiO 2 network, CsPbBr 3 nanocrystals own high stability in ambient environment. • Porous structure of PVDF membrane is beneficial for the nucleation and growth of CsPbBr 3 nanocrystals and gas adsorption. • The whole process of fabrication literally consists of stirring and dropping. • The sensor shows good selectivity, precision and accuracy for NH 3 sensing. • The sensor fills in the shortage of devices capable of high concentration monitoring of NH 3. [ABSTRACT FROM AUTHOR]

To feature fast hydrogen detection, a new design of surface acoustic wave (SAW) based hydrogen sensor integrated with a micro-heater is proposed in this paper. A 200 MHz delay-line patterned SAW sensing chip coated Pd/Ni alloy hydrogen sensitive film and a micro-heater are prepared on a Y35oX quartz wafer. The hydrogen gas adsorption in Pd/Ni thin-film modulates the SAW propagation, and against the temperature interference, the corresponding changes in acoustic attenuation are collected as the sensor signal. The Micro-heater is designed to catalysis the gas-sensitive effect by regulating the working temperature, and the influence law of heating temperature towards response speed is revealed theoretically, allowing determination of the optimal working temperature. The experimental results verify the theoretical prediction. Fast response (t 90 < 2 s), lower power consumption (<1.35 W), and the low detection limit (<15 ppm) are achieved at low working temperature of 75 °C. Furthermore, very low crossed humidity sensitivity and excellent long-term stability are observed. • The novel design of SAW hydrogen sensor integrated with a micro-heater. • The influence law of heating temperature towards response speed is studied. • The optimal working temperature determined by the experiment is 75 °C. • The SAW sensor shows fast response of 2 s to 1% H 2 concentration. • The sensing system with small size and low power consumption is implemented. [ABSTRACT FROM AUTHOR]

This paper presents the first systematic study on the characterization of dynamic adsorption regimes of gas in porous media using the ratio of inter- to intraparticle diffusion coefficients. The effect of the ratio between the two diffusion coefficients on the adsorption dynamics was investigated in combination with the adsorbent particles size and the disorder parameter, which numerically describes pore space heterogeneity, by mathematical modelling using the lattice Boltzmann simulations for fluid flow and the convective-diffusive transport of an adsorbate dissolved in a fluid. To characterize the dynamic adsorption regimes, for the first time, a relationship between the surface and total adsorption amount was used. The obtained results during simulations in two-dimensional synthetic porous structures showed that the size of the adsorbent particle strongly affects the surface and the total adsorption dynamics. An increase in the particle size promotes an increase in the rate of surface adsorption. Depending on the ratio of inter- to intraparticle diffusion coefficients, increasing particle size promotes either an acceleration or slowdown of the total adsorption dynamics. The results revealed in two-dimensional structures were verified by simulations in three-dimensional digital models of natural sandstones, which were obtained using X-ray computed tomography. • Adsorption dynamics regimes are characterized using diffusion coefficients. • Reducing particle size can both speed up and slow down total adsorption dynamics. • Pore space heterogeneity decelerates total adsorption dynamics. • The results obtained for 2D structures are validated for 3D natural rocks. [ABSTRACT FROM AUTHOR]

• Seasonal performances of gas-driven NH 3 -H 2 O absorption heat pumps are compared. • Single effect, Generator Absorber eXchange, and Vapor cycles are considered. • Fixed, double, and variable restrictors in the solution branch are considered. • The use of variable restrictors increases the seasonal gas utilization efficiency. • Performances increase up to 12%, especially for the advanced cycles (GAX and VX). Gas-driven absorption heat pumps are a valid alternative to condensing boilers for non-insulated buildings with radiators as emission system. In fact, they can provide high supply water temperatures with limited performance degradation. However, their seasonal performance is often limited by suboptimal operation at partial load conditions, due to the reduced generator temperature. In this paper, the use of variable and double restrictor on the solution branch between generator and absorber are investigated as possible options to optimize the generator temperature at different operating conditions. The seasonal gas utilization efficiency (SGUE) of three different absorption cycles is compared through numerical simulations using the approach proposed by the standard EN12309. The considered cycles are the single effect cycle (SE), the Generator-Absorber eXchange cycle (GAX), and a version of the Vapor eXchange cycle (VX). Results show that the use of a double restrictor provides an improvement of the SGUE of 7% for the VX cycle, 6% for the GAX cycle and 2% for the SE cycle, compared to the classic fixed restrictor cases. The variable restrictor provides an increase of the SGUE of 12%, 10%, and 2.3% for VX cycle, GAX cycle, and SE cycle respectively. The variable restrictor provides the best performances because it can optimize the generator temperature for every working condition, while the double restrictor gives remarkable improvements with a simpler and easier to be controlled approach. Advanced cycles obtain the highest performance improvements because an appropriate temperature in the generator is of paramount importance for their correct operation. [ABSTRACT FROM AUTHOR]

The escalating gas turbine (GT) inlet temperature and the amplifying radiation effect of multi-component radiation gases aggravate the thermal radiation phenomena. In addition, the omission of radiation effect in the classical film cooling scaling criteria makes the research data obtained under relative low temperature conditions invalid. This paper provided a mechanistic-level explanation of the influence of the thermal radiation term on the energy equation, and subsequently introduced two novel dimensionless parameters (radiation number and optical thickness) that can effectively reflect the radiation impact on scaling criteria. Furthermore, three parameter matching schemes were proposed to enable the data match of high and low temperature conditions for adiabatic cooling effectiveness, overall cooling effectiveness, and dimensionless radiation heat flux. Compared to the high temperature test method, the scaling criteria can provide valuable insights into the film cooling behavior under realistic GT conditions. The method proposed in this paper can not only help prevent material loss and energy waste but also align with the principles of energy conservation, emission reduction, and sustainable development. • R n and τ g were introduced to effectively reflect the radiation impact on scaling criteria. • The determination process of wall emissivity and gas absorption coefficient was proposed. • Three schemes of novel scaling criteria were presented. [ABSTRACT FROM AUTHOR]

• Suitable temperature range for membrane gas separation is between 300 K and 450 K. • The whole permeation process was simulated by molecular dynamics. • The bilayer graphene has better performance for CO 2 / N 2 separation than the single-layer. • Adsorption of gas molecules on graphene membrane at different temperatures was analyzed. • The best pore size for the graphene membrane gas separation was found to be 4.5 Å. Carbon capture technology can directly reduce the emission of CO 2. Due to its advantages in low operating cost and fewer requirements on the installation environment, membrane separation is regarded as the most potential carbon capture technology. In this paper, the gas separation process through graphene membrane is studied by molecular dynamics simulation. The effects of layers, and temperature of gases on the separation effect were studied respectively. It was found that as the temperature increases, reduced selectivity of graphene membranes for CO 2 and N 2 , and the double-layer graphene membrane had a higher penetration flux but low selectivity. The influences of pore size on the separation effect of the two gases were also studied. The results show that CO 2 has the best permeability when the pore size is 4.5 Å. Besides, the change of the diffusion rate of CO 2 molecules from the retentate side to the permeate side with time was also studied by the method of molecular simulation. Meanwhile, the adsorption situation of gas molecules with time was also studied. The adsorption phenomenon on the surface of graphene membranes explains the ability of graphene membranes to achieve separation of CO 2 and N 2 molecules. The current study of membrane separation provides valuable theoretical support for the theoretical basic research work in the field and the research of membrane materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • Introduced metal-catechol groups to adsorb SO 2 in UiO-66, HBU-20, and MFM-601. • MOFs with different pore types have different abilities to adsorb SO 2 molecules at different partial pressures and temperatures. • Significantly improved adsorption performance of Cat(Cu)-UiO-66 and Cat(Cu)-MFM-601. Sulfur dioxide (SO 2) is a polluting gas that poses a significant threat to the environment and human health. Adsorption and removal of SO 2 is an effective means in its control process, and MOFs have garnered widespread attention due to their immense potential in the field of gas adsorption. In this paper, the adsorption process of SO 2 in the pore structures of three Zr-based MOF materials, UiO-66, MFM-601, and HBU-20, was firstly simulated based on MD and GCMC. The ability of different pore structures to adsorb SO 2 gas at varying temperatures and pressures was analyzed with emphasis. Subsequently, the three MOFs were modified by introducing metal-catechol into each of them. The effect of Cat(M) (M = Cr, Mn, Fe, Ni, Cu, Zn) on the SO 2 adsorption properties of the MOF materials was deeply analyzed based on DFT. The results indicated that the introduction of Cat(M) significantly enhanced the adsorption capacity of UiO-66 and MFM-601 for SO 2. Notably, UiO-66-Cat(Cu) and MFM-601-Cat(Cu) exhibited the most significant enhancement effects, reaching 30.8 % and 102.7 %, at room temperature and pressure. Furthermore, Cat(M) enhanced the thermal stability of UiO-66 and MFM-601. These findings hold guiding significance for the study of MOF modification for the removal of SO 2 gas. [ABSTRACT FROM AUTHOR]

When organic molecules are detected by gas-sensitive test, an oxidation-reduction reaction is triggered to consume adsorbed oxygen, and the change of material conductance resulting from the consumption of adsorbed oxygen is detected. In this paper, the molecular adsorption and gas-sensitive behavior of WO 3 (200) and (002) crystal planes are investigated. Density functional theory (DFT) simulations reveals that ethanol (C 2 H 5 OH) and oxygen molecules (O 2) have different adsorption active sites on the (200) and (002) crystal planes, there is no adsorption competition between C 2 H 5 OH molecules and O 2 molecules on the crystal plane, resulting the two crystal planes exhibit excellent selectivity for ethanol gas. Compared with other molecules, acetone (C 2 H 6 CO) and O 2 occupy the closest adsorption active sites on the (200) crystal plane, resulting in increased adsorption competition, which prolongs the response time and reduces the gas-sensitive selectivity. The molecular adsorption behavior holds important theoretical significance for studying the gas-sensitivity properties of materials. • The co-adsorption of ethanol and O 2 molecules makes selectivity of ethanol better. • Acetone molecules produce competitive adsorption with O 2 molecules. • WO 3 (200) and (002) crystal planes have different gas-sensitive selectivity. [ABSTRACT FROM AUTHOR]

• A novel ZnO@ZIF-8 nanorods array film was successfully synthesized via a template-free solvothermal method. • The film exhibited excellent response to Cl₂ gas at a low operating temperature of 40 °C. • The synergistic effect between ZnO and ZIF-8 in promoting Cl₂ adsorption was also explored. Real-time monitoring of chlorine gas (Cl 2) with a strong irritating odor is an indispensable means of avoiding its contamination of the air and harm to the body. To achieve this purpose, a novel gas-sensitive material capable of detecting low concentrations of Cl 2 at near room temperature is developed in this paper. ZIF-8 with a kinetic diameter of 3.4 Å in the designed ZnO@ZIF-8 composites is able to sieve gas molecules with different kinetic diameters, enabling effective improvement of the selectivity of the gas-sensitive materials. In addition, the porous structure of ZIF-8 can provide more reactive sites, which is conducive to improving gas adsorption capacity and providing of channels for gas diffusion. In this study, ZnO@ZIF-8 heterojunction composites are prepared by combining the advantages of ZnO and ZIF-8, which provides a new method for real-time monitoring of low concentrations of Cl 2 , and also has potential practical applications in fields such as environmental monitoring and industrial safety. [ABSTRACT FROM AUTHOR]

In the paper, the findings demonstrated that the pore volume and specific surface area within tectonic coals increase as the particle size decreases. The pores consisted of different proportions of bottleneck pores, cylindrical pores, and slit−/plate-like pores. The ultimate gas desorption volume and initial gas desorption rate of tectonic coals varied exponentially and quadratically with macropore volume, respectively. The variation law of gas desorption rate states that when the particle size is below the limiting particle size, the coal matrix sustains significant damage. This results in a shortened gas diffusion length and reduces the gas diffusion resistance, leading to an extremely rapid increase in the initial gas desorption rate. Due to the limitation of pore scale in coals, the gas diffusion coefficient of tectonic coal rises with particle size. The effective diffusion coefficient increases with a decrease in coal particle size, providing an intuitive representation of the fundamental diffusion behavior. Eight tectonic coal samples with different particle sizes, which were obtained by sieving using different size sieves, were prepared. The experiment tested and analyzed the pore structure and adsorption characteristics of tectonic coals with different particle sizes, as well as examined the desorption/diffusion laws under varying pressure conditions. The impact of the pore structure on gas adsorption/desorption characteristics and diffusion kinetics laws in coal was investigated. The results can be used to establish a theoretical foundation for the preclusion of gas dynamic catastrophes in tectonic coal seams. [Display omitted] • The pores in tectonic coal can be divided into three types. • The pore volume of tectonic coal determines the gas adsorption capacity. • The effective diffusion coefficient can index the nature of diffusion behavior. [ABSTRACT FROM AUTHOR]

This paper introduces the adsorption of four harmful gases (CH 4 , HCHO, SO 2 , NO 2) on MoTe 2 monolayer and transition metal (V, Cr, Mn) decorated MoTe 2. Based on the density functional calculation (DFT), the adsorption energy, charge transfer, density of state, deformation charge density, and molecular orbitals are analyzed. It was found that transition metal decoration significantly promoted the adsorption ability of MoTe 2. [Display omitted] • Adsorption properties of pristine MoTe 2 decorated with V, Cr, Mn monolayers towards CH 4 , HCHO, SO 2 , NO 2 gases were discussed. • V-MoTe 2 had the highest adsorption energy, making it a better gas removal material. • Sensor response and recovery time were evaluated. For the detection and removal of four hazardous gases (CH 4 , HCHO, SO 2 , NO 2), we used density functional theory to investigate the properties of the pristine MoTe 2 and MoTe 2 decorated with V, Cr, and Mn atoms. By examining the density of state, adsorption energy, and charge transfer of four gases adsorbed on the surface, it was showed that the adsorption capability of MoTe 2 was significantly enhanced after the decorating of transition metals. V-MoTe 2 had the highest adsorption energies (−0.527, −2.574, −1.480, −3.363 eV) of the four gas molecules, making it a better gas removal material. The adsorption energies on Cr-MoTe 2 and Mn-MoTe 2 were lower than that of V-MoTe 2 , and their desorption time were shorter, making them more suitable for the application of gas sensors. This study revealed that V, Cr, and Mn-decorated MoTe 2 were potential materials for the detection or removal of CH 4 , HCHO, SO 2 and NO 2 gases, V-MoTe 2 was more suitable for the removal, while Cr and Mn-MoTe 2 were more suitable for the detection of harmful gases. [ABSTRACT FROM AUTHOR]

• The integrated flash-binary and two-phase binary layouts are analyzed and compared. • The two plant layouts integrate the water absorption and reinjection of H 2 S and CO 2. • The net power output approaches that of a layout with condensing steam turbine. • The power penalties are reduced by the better integration with the abatement section. • The H 2 S and CO 2 abatement reach 99% and 90% if brine can be used for gas absorption. The power production from geothermal resources with a high content of non-condensable gases (NCG) is concerning an increasing number of regions and may affect the sustainability relating to geothermal projects. The selection of an emission abatement system based on water absorption and reinjection of NCG back to the reservoir could solve the environmental impact, yet it implies significant power output penalty and water demand, as demonstrated in a recent paper by the authors (Manente et al., 2019) focused on the retrofit of existing flash steam power stations. A reconsideration of the plant design could result in a better integration with the absorption and reinjection section and finally reduce the associated requirements. To address this point, two "greenfield" plant layouts are investigated in this paper for utilization of a high enthalpy liquid dominated reservoir, where the single flash steam generation unit is complemented or even totally replaced by air cooled binary cycle units. The first layout is an "integrated flash-binary" plant based on a backpressure steam turbine and a bottoming ORC system, whereas the second layout consists in a "two-phase binary" plant. The performance of the two novel layouts is compared against that of a brownfield layout, first proposed in Manente et al. (2019), based on an existing single flash plant retrofitted with the absorption and reinjection system, using a consistent set of assumptions. The results show that the net power output remains almost unaltered because in the novel layouts the lower parasitic loads for gas compression counterbalance the lower production dictated by the air-cooled system and the irreversibility in the heat transfer between geothermal fluid and organic fluid. Thus, due to the better integration between power block and emission abatement section the net power output penalty of the novel layouts is contained within 2%. On the other hand, the hydrogen sulfide and carbon dioxide abatement efficiencies markedly increase as the removal of the cooling tower eliminates the secondary gaseous emissions and makes the entire steam condensate available for NCG absorption. In the integrated flash-binary plant design the overall H 2 S and CO 2 abatement efficiencies reach 99% and 90%, respectively, without any external water demand, provided that measures are taken for a controlled precipitation of silica and other minerals from the geothermal brine prior to using it for NCG absorption. [ABSTRACT FROM AUTHOR]

Highlights • An analytical radiation thermometry model considering both reflected ambient radiation and absorption and emission of radiation by interfering gas is developed. • The temperature errors caused by interfering gas and reflected ambient radiation are quantitatively analyzed. • The selection methodologies of spectral pass-band of radiation thermometer to minimize the influences of reflection and gas mixture absorption and emission under different conditions are proposed. Abstract To investigate the coupling effects of reflection and absorptive gas mixture on surface temperature determined by single color pyrometer, an analytical radiation thermometry model combined with a mathematical radiative heat transfer model, which simultaneously considering both the reflected ambient radiation and the gas absorption and emission of radiation, was established in this paper. The temperature errors caused by the combination of intervening gas mixture and reflected ambient radiation were quantitatively analyzed under three practicable measurement strategies depending on the relative target and gas temperatures. As the results indicate, the investigated wavelength ranges can be roughly divided into three parts depending on the relative importance of reflection and gas mixture. Correcting for the hot/cool gas mixture effect through use of a low/high temperature reflector is usually effective because these two effects will cancel each other out. The selection methodology of spectral pass-band of radiation thermometer to minimize the influences of reflection and gas mixture absorption and emission under different conditions was presented. Sensitivity analysis of the derived temperature error to the variations in ambient temperature, target surface emissivity, gas mixture temperature and concentration, and viewing path length was investigated. Considering the case T 1 = 1200 K, T 2 = 1400 K, T g = 2000 K, ε 1 = 0.85, L = 100 cm, X H 2 O = 0.2, X C O 2 = 0.1, p = 1 atm, the most influential factor is gas mixture temperature for wavelength longer than 1.33 µm, followed by other factors. For wavelength shorter than 1.33 µm, the high ambient temperature is the main contributor to the imprecision in the proposed model output. The analyses in the paper may provide the necessary theoretical supports for the design and application of a radiation thermometer in the presence of intervening gas. [ABSTRACT FROM AUTHOR]

Abstract In this paper, the various optimized generators for H 2 O/LiBr absorption chiller with multi-heat sources are discussed. While the previous optimization has been mainly conducted for a single element, the integrated generation system including high/low temperature generator and waste heat recovery generator is optimized in this paper. A practical modeling method is proposed for the high/low temperature generator and it has been verified by comparing with experimental results. Meta-models for the volume and the generation rate are built with kriging method, and the generators are optimized by multi-objective optimization technique using the meta-models. The total volume is minimized and the total generation rate is maximized according to five design variables of the generators. It is found that from the optimization process the total volume is decreased by 59.06% and the total generation rate is increased by 31.46% compared to the baseline point. It is concluded that the contribution of the waste heat recovery generator and the high temperature generator are dominant for the total volume reduction and the total generation rate improvement, respectively. Moreover, the effects of the key variables on the performance of each generator are analyzed according to the optimization of the integrated generation system. Highlights • A practical modeling method is proposed for generators with multi-heat sources for tri-generation systems application. • The generators are optimized by multi-objective optimization technique using the meta-models. • The total volume is decreased by 59.06% while total generation rate is increased by 31.46% by the optimization. • The waste heat recovery generator is dominant for the total volume reduction. • The high temperature generator is dominant for the total generation rate improvement. [ABSTRACT FROM AUTHOR]

The rotating packed bed (RPB) is a promising advanced reactor used in industrial gas-liquid two-phase reaction processes because of its high phase contact efficiency and mixing efficiency. Investigation of RPBs using CFD simulations will improve the understanding of physical behaviours of gas and liquid flows in such reactors. Currently, CFD simulations on the RPBs only focus on the volume of fluid (VOF) method. However, the VOF method is not suitable for simulations of pilot-scale 2D and 3D RPBs due to the limitations in computer resources, while the Eulerian method using a porous media model is a promising alternative method but it is rarely reported. The reason is that there are no suitable porous media models that accurately describe the drag force between the gas and liquid, the gas and solids and the liquid and solids due to the high porosity and the stacked wire screen packing used in RPBs. Therefore, the purpose of this paper is to propose a new model for modelling RPBs. The new proposed model is based on the Kołodziej high porosity wire screen one-phase porous media model. In this work, two experimental counter-current gas–liquid flow cases from the literatures have been used for validating the CFD simulation results. Finally, the new model has been compared with the current porous media models for traditional spherical or structured slit packed beds, which are the Attou, Lappalainen, Iliuta and Zhang models. The simulation results show that the proposed new model is the most appropriate and accurate model for the simulation of RPBs among all the models investigated in this paper. [ABSTRACT FROM AUTHOR]

Highlights • Studied the dissipation process of the supersaturated TDG in water with vegetation based on first-order kinetic model. • Developed an adsorption model of the vegetation’s effect on the supersaturated TDG. • The adsorption rate in the model is determined by the material properties. • The model is suitable for static conditions. Abstract Flood plays a vital role in aquatic organisms’ subsistence and reproduction. It can bring spawning signals to fishes and excessive foods fattening fishes up in the flood plain. Nowadays, with an increasing number of high dams being put into operation, huge changes have happened in the process of natural flood. In order to maintain the ecological function of flood, sometimes hydropower stations have to make artificial flood peak by the power station’s spillway discharging. Water discharge from high dams leads to the supersaturation of total dissolved gas (TDG), thus causing fish to suffer from gas bubble disease (GBD) and even death. The downstream water level rises during the period of discharge, inundating part of the vegetation on the bottomland. The existence of vegetation can affect the hydrodynamic characteristics of flood water flows and then change the transportation and dissipation of the supersaturated TDG. The stems and leaves of the submerged vegetation provide a large amount of solid-liquid interfaces, which adsorb gas dissolved in water, consequently influencing the dissipation process of supersaturated TDG. In this paper, research about the effect of vegetation on supersaturated TDG is conducted underpinned by laboratory mechanism experiments. The supersaturated TDG dissipation process with vegetation existing in the water was obtained. The results indicate that planting vegetation in water can effectively bolster the releasing of TDG, and as the density of vegetation increases, the promotion effect is commensurately enhanced. Based on the experimental data, this paper proposes a supersaturated TDG dissipation model describing the function of the vegetation’s wall adsorption of the TDG, and the formula for the adsorption flux F a of supersaturated TDG in a unit area over a unit time is achieved. This paper obtains a significant parameter representing how fast the vegetation’s surfaces adsorb the supersaturated TDG, namely, the adsorption rate k a. It is determined that k a is solely related to the vegetation’s material and surface characteristics. [ABSTRACT FROM AUTHOR]

• Aerogel and flue gas were utilized together in advancing heavy oil development. • The heat transfer characteristics of flue gas coupled with aerogel were clarified. • The mechanism of steam migration under the action of aerogel was revealed. • Negative impacts stemming from steam breakthrough and uplift had been mitigated. • The proposed technical solution resulted in an oil recovery increase of up to 9.3%. High carbon emissions and low efficiency in thermal utilization are pivotal challenges in heavy oil development. Addressing the urgent need to enhance heavy oil production, this paper introduces an innovative approach in which aerogel and flue gas serve as supplementary additives in steam thermal recovery. To investigate the mechanisms behind the improved heat transfer and oil recovery facilitated by the combination of aerogel and flue gas, condensation heat transfer experiments and 2-D visual oil displacement experiments were carried out. The condensation heat transfer coefficient, oil displacement performance, and heat utilization efficiency were analyzed and compared. The results showed the porous structure of the aerogel enhances its thermal insulation properties by adsorbing flue gas, thereby reducing the steam-to-cold object condensation heat transfer coefficient by 60.6%. The cementation between aerogel nanoparticles (NPs) retained in the formation and rock particles formed an insulating layer that impedes the upward propagation of steam heat. Combined with efficacy of flue gas foam in improving fluid flow, this promoted the horizontal expansion of the steam chamber, resulting in an 8.2% and 3.4% increase in the steam chamber's extent compared to using steam and a combination of steam with aerogels, respectively. Moreover, the profile control and thermal insulation impacted following the NPs, lowering the water cut in the produced fluid and enhancing the oil recovery by 7.9%. Upon the application of flue gas, this enhancement in recovery extended to 9.3%. [ABSTRACT FROM AUTHOR]

This study systematically investigates the gas adsorption characteristics of silicon carbide (SiC) as a potential contributor to defects, including shrinkage and porosity, in SiC particle reinforced Aluminum (SiCp/Al) composites. Key factors affecting these composite materials defects such as SiC particle size, gas atmosphere, and gas pressure, are comprehensively explored. The research begins by elucidating the mechanism through which the melt absorbs gas during the processing flow. Additionally, mathematical models correlating [O] growth with temperature and [N] peak contentwith gas pressure are established. The paper concludes by proposing effective strategies to diminish defects and enhance the purity of composite materials. These strategies include reducing melting time, decreasing melting temperature, increasing the vacuum during melting, and implementing high-temperature degassing. • The fundamental factor of porosity defects in aluminum matrix composites is pointed out, that is the characteristic of SiC adsorbing gas. • Key factors affecting these composite materials defects such as SiC particle size, gas atmosphere, and gas pressure, are comprehensively explored. • The inspiratory mechanism of aluminum melt in three stages of the preparation process is described, and some suggestions for reducing inspiratory and degassing at high temperature are given. [ABSTRACT FROM AUTHOR]

In the paper, a novel dual circulating fluidized bed (DCFB) reactor is introduced, which can be widely applied in catalytic cracking, chemical looping combustion, coal/biomass combustion and gasification, and gas adsorption, etc. The study mainly investigates the effects of specific operating parameters on pressure balance and solid circulation rate, including total solids inventory, riser gas velocity, bubbling fluidized bed gas velocity and pot-seal gas velocity. It is found that changes of those parameters lead to variations in pressure balance and riser axial voidage in DCFB system, and further affect solid concentration and solid circulation rate in the system. To be more specific, total solids inventory, riser gas velocity and bubbling fluidized bed gas velocity have a major impact on solid concentration and solid circulation rate, while pot-seal gas velocity only exerts a minor impact. Besides, the changing of overall pressure drop across the bubbling fluidized bed is consistent with variations in pressure drops in the other parts of the system, with the former equaling △ P r + △ P c + △ P p-t + △ P ud1 + △ P ud2 . In this way pressure balance in the system is maintained. Eventually the paper reaches the conclusion that relevant operating parameters can be adjusted to control pressure distribution and solid circulation rate in different parts of the system and further to ensure the safe and stable operation of DCFB reactors. [ABSTRACT FROM AUTHOR]

Atomic force microscopy (AFM) serves as a prominent micro- and nano-scale observation method in various scientific domains encompassing biology, materials science, physics, and chemistry. Its application in the characterization of coal and rock, has gained significant attention in recent years, resulting in numerous valuable research findings. These findings offer fresh insights and novel perspectives for related research endeavors. This paper presents a systematic review of the progress made in utilizing AFM to measure coal and rock. It summarizes the key achievements and the significance of the current research in the areas of coal and rock pore structure, micro-surface mechanics, and electricity. Furthermore, based on the existing progress and challenges, this review also proposes potential avenues for future research directions of this measurement method. The application of AFM not only introduces a new approach for investigating the pore structure of coal and rock but also offers experimental support and innovative conceptual frameworks for exploring the mechanical mechanisms behind coal and rock fracture, the microscopic processes of gas adsorption, outbursts, and the generation of electromagnetic radiation induced by coal and rock fractures. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel isotherm model for the thermodynamic study of ion exchange reactions is proposed. • The results calculated by the novel isotherm model agree well with the experimental data. • The physical meaning of the parameters involved in the novel isotherm model is clear. • It is applicable to various situations of ion exchange reactions and has good versatility. Ion exchange is a separation and purification technique widely employed in chemistry, environment and metallurgy. Commonly, the isotherm models used for thermodynamic study are the Langmuir model and the Freundlich model. However, these two models are initially used to study the adsorption of gas molecules onto solids, and there are some limitations if they are applied to ion exchange reactions. In this paper, a novel isotherm model (NIM) for ion exchange reactions was derived based on the process of ion exchange, the principle of electroneutrality and the law of conservation of mass. The NIM was utilized to study the reactions of anions (F-, WO 4 2 - , MoO 4 2 - , PO 4 3 - , AsO 4 3 - , MoS 2 O 2 2 - , MoS 4 2 - ) with chloride-form strongly basic anion exchange resins. Moreover, the reactions of cations (K+, Ca2+) with sodium-form cation exchange resins were also explored. The results indicated that the calculation data based on the NIM matched up well with the experiments, even though the ions have various valences and different affinities for the resin, which proved the reliability of the model. In addition, the compatibility of the NIM with the Langmuir and Freundlich models was theoretically analyzed, and the conclusions were also verified by the experimental data. By contrast, the physical meaning of the parameters involved in the NIM was clear and had a good generality, which can be applicable to various situations of ion exchange reactions. Therefore, the NIM proposed in this work can effectively obtain the thermodynamic parameters of ion exchange reactions, and is expected to provide theoretical basis for the design, optimization and control of ion exchange processes. [ABSTRACT FROM AUTHOR]

This paper proposes the general design of a Wet Electrostatic Scrubber aimed at mitigating fine and ultrafine particles emissions from domestic heating boilers. The design is based on particle capture modelling supported by specific experiments and technical literature information. Results indicate up to 96.6% removal efficiency, consuming 1.2 kg/h of water and 0.3 W per 1 m3/h of gas treated. Comparative analysis highlights the balanced performance of Wet Electrostatic Scrubber in particle capture, energy and water usage, pressure drop, and space occupancy, with the additional benefit of more efficient absorption of gas pollutants. • Wet electrostatic scrubbing is proposed for biomass boilers. • Removal efficiencies estimated through a robust stochastic model up to 96% in number and 99% in volume can be achieved. • Energy consumption is around 0.3 Wh/m3 for water consumption of 1 kg/kg. • WES performance ranks high among consolidated techniques. • Water losses at the scrubber walls are the main sources of efficiency reduction. [ABSTRACT FROM AUTHOR]

Deep eutectic solvents (DESs) are considered to be potential absorbents for CO 2 capture compared to traditional amine solutions, because they have many advantages such as lower volatility and better thermal stability. In this study, a series of novel γ− and ε− m−based amino acid salts (AASs) were prepared through one-step hydrolysis reaction of accessible and cheap lactams as hydrogen bond acceptor (HBA). The chemical structures of these AASs were characterized by ESI-MS and NMR. Dihydric alcohol was selected as hydrogen bond donor (HBD) to prepare AAS-based DESs because of its low specific heat capacity and high boiling point. The physical properties of AAS-based DESs, such as density at 313.2–353.2 K, viscosity at 313.2–353.2 K, the melting temperature from 173.2 to 273.2 K, and thermal decomposition temperature from 300 to 750 K, were also determined. The gas absorption experiments were carried out on a dual-chamber at temperatures from 313.2 to 333.2 K and pressures up to 1.1 bar. It is found that K[Gaba]-EG has the largest CO 2 uptake capacity with 0.12 g·g−1 at 1.0 bar and 313.2 K, better than almost all absorbent with AASs reported in literatures (0.02 g·g−1 ∼ 0.07 g·g−1). The CO 2 absorption mechanisms were proved to be a combination of 2:1 and 1:1 stoichiometric reaction through thermomechanical analysis and NMR. This paper will present distinctive insights into the preparation of CO 2 absorbent for effective carbon capture. • Novel metal-based amino acid salts were prepared via one-step hydrolysis. • The superior absorption capacity of CO 2 can reach 0.12 g·g−1 at 313.2 K. • Amino acid salts react with CO 2 through a combination of 1:1 and 2:1 mechanism. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel fractal Langmuir adsorption equation on coal based on the fractal characteristics of pore heterogeneity is proposed. • The proposed equation achieves a breakthrough in the calculation of the methane adsorption capacity in pores with different pore diameter ranges. • The proposed equation can more accurately reflect the methane adsorption in coal pores compared with the conventional Langmuir equation. The conventional Langmuir equation based on the homogeneous surface assumption is failed to characterize the gas adsorption in coal due to the obvious heterogeneity of the coal pore structure. Therefore, a novel fractal Langmuir adsorption equation on coal is proposed based on the fractal characteristics of pore heterogeneity in this paper. The pore heterogeneity in coal displays obvious fractal characteristic, which can be characterized by the fractal dimension for the pore tortuosity (D T) and the fractal dimension for the pore size (D f). The principles and methodology of the proposed equation are deduced and summarized in detail. The results indicate that the proposed fractal Langmuir adsorption equation displays the higher accuracy than the conventional Langmuir equation. In addition, the proposed equation is the function of the fractal dimension for the pore tortuosity (D T), the fractal dimension for the pore size (D f), and the pore structural parameters (λ min , λ max , and L), which more comprehensively reflects the influence of pore structure on adsorption. Therefore, the proposed equation achieves a breakthrough in the calculation of the methane adsorption capacity in pores with different pore diameter ranges, which can more accurately reflect the methane adsorption in coal pores compared with the conventional Langmuir equation. [ABSTRACT FROM AUTHOR]

Insulation performance testing of gas-insulated switchgear (GIS) and treatment of SF 6 decomposition products under partial discharge are two crucial studies. In this paper, the adsorption behavior and sensor properties of five characteristic decomposition gases of SF 6 (HF, H 2 S, SO 2 , SOF 2 , SO 2 F 2) on intrinsic and CoO-doped SnSe monolayers are investigated in detail based on density-functional theory. The results showed that the adsorption behaviors of HF, H 2 S, SOF 2 and SO 2 F 2 on SnSe monolayers were all physisorption among which the best adsorption was SO 2 with an adsorption energy of −0.618 eV, which is a weak chemisorption. After doping with CoO, the adsorption capacity of SnSe monolayer for five gases was significantly enhanced, in which the adsorption energies for SO 2 and SOF 2 reached −1.356 eV and −1.175 eV, respectively. In addition, the conductivity of the system is greatly improved, with the bandgap changing from 1.129 eV to 0 eV. The microscopic mechanism of the interaction of gas molecules with CoO-SnSe monolayers has been revealed by energy band structure (E g), density of states (DOS), Milligan charge analysis (∆ Q) and electrostatic potential. Finally, the sensitivity (S) and desorption time (τ) of the five adsorption systems were calculated to illustrate the macroscopic gas-sensitive properties of the system. This work will help to explore the application of CoO-SnSe monolayers in SF 6 decomposition gas sensing detection and adsorption treatment. [Display omitted] • Doping greatly improves the conductivity of the system, and the adsorption effect of doped system on SO 2 and SOF 2 is significantly improved. • The change of electronic characteristics of doped system is expounded. • The sensing characteristics of adsorption system are calculated, and the possibility of SOF 2 as the target gas for CoO-SnSe sensing device to evaluate GIS insulation performance is explored. [ABSTRACT FROM AUTHOR]

This paper describes a new simple 1H PFG NMR method that allows the direct calculation of weakly absorbing gas phase (methane and ethane) intra-crystalline molecular self-diffusion coefficients in microporous β-zeolite samples without the need for gas adsorption isotherm data or the kinetic theory of gases. The method exploits 1H PFG NMR and T 1 /T 2 relaxation measurements from two distinct regions of a single flame sealed sample: (i) the pure gas phase region well above the zeolite powder bed and (ii) the region occupied by the zeolite crystallite bed. 1H Relaxation time measurements allow the fractional population of the intercrystallite gas species within the zeolite bed, p inter , to be determined. 1H PFG NMR experiments are then used to calculate the long-range self-diffusion coefficient D long − range and the pure gas phase diffusion coefficient, D gas. The intracrystalline molecular self-diffusivity D intra is then calculated using only these three parameters. The results show that D intra is generally 2–4 times lower than D long − range and that the method is independent of zeolite crystallite size. [Display omitted] • Simple 1H NMR method to calculate intracrystalline diffusion coefficients in adsorbed gas/microporous materials. • All measurements are from a single flame sealed sample. • No other analytical techniques are required. • Method is independent of microporous material crystallite size. • Potential for routine use on Benchtop NMR systems. [ABSTRACT FROM AUTHOR]

[Display omitted] • Transition metal modification (Pt, Pd, Rh) enhances GaSe conductivity, with Rh > Pt > Pd. • Adsorption of SO 2 , SOF 2 , and SO 2 F 2 is improved, causing structural deformation in Pt-GaSe but maintaining stability in Pd-GaSe and Rh-GaSe. Chemical adsorption leads to more stable structures. • Conductivity analysis shows varying effects on Pt-GaSe, Pd-GaSe, and Rh-GaSe upon gas adsorption. Pt-GaSe holds promise for resistive SO 2 F 2 sensors, Pd-GaSe for SO 2 detection, and Rh-GaSe for multi-gas detection at specific temperatures. Detection and absorption of SF 6 decomposition products in the gas-insulated switchgear (GIS), can greatly delay the aging of insulation media. Thus, the materials with more sensitive and better adsorption performance are aimed to find. In this study, Pt, Pd, and Rh modified GaSe are proposed as the gas sensing materials for detecting the characteristic decomposed gases (SO 2 , SOF 2 , SO 2 F 2). The adsorption energy, density of states, energy band, electrical conductivity, recovery time are calculated to analyze the modification and gas adsorption processes. The applicability of the proposed material in three target gases is evaluated. The results show that GaSe doped with Pd, Pt, and Rh have better adsorption capacity for SO 2 , SOF 2 , and SO 2 F 2. Moreover, the target gases can be quickly desorbed by heating after adsorption, ensuring the reusability of the GaSe material. Research content of this paper could provide reference to select suitable materials to detect SO 2 , SOF 2 , and SO 2 F 2. [ABSTRACT FROM AUTHOR]

• Predicting a metal-organic frameworks deliverable capacity using Gaussian processes. • Locating active subspaces enables optimal dimension reduction of pore properties. • Applied to a practical exploration example comparing methane and oxygen storage. • Found top-performing oxygen structures irrelevant to the gas in the training data. • Presented an efficient method to predict and search for promising frameworks. To date over 80,000 metal-organic framework (MOF) structures have been synthesised and only ca. 3% of these have had their adsorption capabilities measured for storing oxygen alone. As such, in order to aid the process of producing top-performing MOFs for storing various gases, accurate methods to predict the deliverable capacity of MOFs that have their synthesis method already known is increasingly important. For this purpose, this paper develops a reduced order model (ROM) that can predict the deliverable capacity of synthesised MOFs irrespective to the storage gas across similar gases. The ROM is constructed by identifying the active subspaces through a Sobol' index-based global sensitivity analysis (GSA). The resulting Gaussian process (GP) regression model efficiently predicts the deliverable capacity given a MOFs pore properties with this reduced dimensional space. This approach was applied to a practical MOF exploration example by training a ROM with 2745 MOFs storing methane at 30 bar. The ROM was robustly tested and analysed before using it to predict the deliverable capacity of 82,221 synthesised MOFs storing oxygen at 30 bar. To ensure validity in the exploration example, the predictions produced from the methane trained ROM were compared to a separate ROM trained using the same MOFs but storing oxygen gas. The methane trained ROM was found to be in agreement with the oxygen trained ROM, and was shown to be a viable tool to identify the top-performing MOF structures for oxygen storage. [ABSTRACT FROM AUTHOR]

Magnesium-based hydrogen storage materials are considered as one of the most promising candidates for solid state hydrogen storage due to their advantages of high hydrogen capacity, excellent reversibility and low cost. In this paper, Mg 91.4 Ni 7 Y 1.6 and Mg 92.8 Ni 2.4 Y 4.8 alloys were prepared by melting and ball milling. Their microstructures and phases were characterized by X-ray diffraction, scanning electron microscope and transmission electron microscope, and hydrogen absorbing and desorbing properties were tested by the high pressure gas adsorption apparatus and differential scanning calorimetry (DSC). In order to estimate the activation energy and growth mechanism of alloy hydride, the JMAK, Arrhenius and Kissinger methods were applied for calculation. The hydrogen absorption content of Mg 92.8 Ni 2.4 Y 4.8 alloy reaches 3.84 wt.% within 5 min under 350 ℃, 3 MPa, and the maximum hydrogen capacity of the alloy is 4.89 wt.% in same condition. However, the hydrogen absorption of Mg 91.4 Ni 7 Y 1.6 alloy reaches 5.78 wt.% within 5 min, and the maximum hydrogen absorption of the alloy is 6.44 wt.% at 350 ℃ and 3 MPa. The hydrogenation activation energy of Mg 91.4 Ni 7 Y 1.6 alloy is 25.4 kJ/mol H 2 , and the enthalpy and entropy of hydrogen absorption are -60.6 kJ/mol H 2 and 105.5 J/K/mol H 2 , separately. The alloy begins to dehydrogenate at 210 ℃, with the dehydrogenation activation energy of 87.7 kJ/mol H 2. By altering the addition amount of Ni and Y elements, the 14H-LPSO phase with smaller size and ternary eutectic areas with high volume fraction are obtained, which provides more phase boundaries and catalysts with better dispersion, and there are a lot of fine particles in the alloy, these structures are beneficial to enhance the hydrogen storage performance of the alloys. [ABSTRACT FROM AUTHOR]

Natural coal used in experiments often contains unknown substances which endow it with strong anisotropy and affect the accuracy of experimental results. This paper is aimed at analyzing the single-factor and two-factor-coupling influences on the properties of coal-like materials with different proportions. A coal rock drillability evaluation system was developed based on the principle of Fréchet distance algorithm to evaluate the similarity between drilling simulation experiment data of coal-like materials and natural coal. The results disclose that the cement is of the most notable regulating effect on the material properties. Under the coarse-to-fine ratio of 1:4, the cement content of 20%, the molding pressure of 25 MPa and the pressure holding time of 0.5 h, the coal-like materials are of the optimal mechanical and gas adsorption properties. The fluctuation characteristics of drilling experimental data curve are the most similar to those of natural coal, with the similarity ratio being 0.54. [Display omitted] • The best drilling experimental material. • Mechanical properties, gas adsorption performance and drillability. • The coal rock drillability evaluation system is developed. [ABSTRACT FROM AUTHOR]

• In FTIR and mercury intrusion study of molecular structure change characteristics of SDS modified coal. • Correlation of coal molecular structure with wettability and methane adsorption capacity. • Essence to the explanation of the decrease of coal methane adsorption capacity under SDS modification coal. Adding ionic solution can improve the microstructure of coal, inhibit the gas absorption capacity and effectively reduce the outburst risk. In this paper, the high-quality anthracite in Jincheng, Shanxi Province is selected as the research object, and sodium dodecyl sulfate (SDS) ion solutions with different concentrations are configured. Combined with infrared spectroscopy, mercury intrusion test, the change features of coal microstructure after soak by SDS solutions with different concentrations are studied, and the variations of the contact angle and adsorption constant of samples before and after modification are tested. The paper further discusses the influence of changing coal microstructure on the wettability and gas adsorption. The experimental results show that SDS can modify the microstructure of coal to some extent: –OH, -C O, and C O C increase obviously, macropores and mesopores increase, micropores and ascospores decrease. After SDS modification, the contact angle and the maximum gas adsorption a decrease linearly as oxygen groups and vtotal increase. In addition, the hydrophilic groups in the coal body increase significantly, which makes it easier to attract water molecules, and strengthen the pore connectivity and coal wettability. The polar oxygen-containing functional group molecules of coal also increase, occupying the adsorption site of non-polar molecular methane, and the adsorption site (micropore) decreases. The conclusion of this paper establishes theoretical foundation for the exploitation of coal seam gas resources. Adding SDS can directionally ameliorate coal microstructure, and then regulate the coal wettability and its ability to adsorb methane, to utilize coal resources safely and efficiently. [ABSTRACT FROM AUTHOR]

• At present, most of the studies on competitive adsorption of gas in coal seam focus on the gas competitive adsorption of coal samples with a single metamorphic degree, and there are few studies on the gas competitive adsorption of coal bodies with different coal rank. Therefore, this paper selects three coal samples with different metamorphic degrees to conduct the gas competitive adsorption study. • At present, most of the researches on the competitive adsorption of gas in coal are focused on macroscopic experiments, and the characteristics of the competitive adsorption behavior of gas molecules on coal molecules are relatively less studied. Therefore, this paper constructs different coal rank coal molecules to simulate and explore the microscopic competitive adsorption behavior of CO 2 and CH 4 molecules. • At present, most of the coal molecules are constructed based on classical molecular models, such as Fuchs, Given, Wiser and Shinn models. In this paper, coal samples from three different areas were analyzed, and three coal molecular models with different metamorphic degrees were independently constructed, and the competitive adsorption behavior characteristics of gas molecules were studied on the three coal molecular models. To explore the competitive adsorption characteristics of a CO 2 /CH 4 binary gas in coal with different metamorphic degrees, macromolecular-structure coal models with different metamorphic degrees (anthracite coal, coking coal, and long-flame coal) were constructed based on elemental analysis, X-ray photoelectron spectroscopy (XPS), and carbon-13 nuclear magnetic resonance (13C NMR) results. Then, the competitive adsorption behaviors of CO 2 and CH 4 molecules in the different coal molecular models were simulated using molecular dynamics (MD) and grand canonical Monte Carlo (GCMC) methods, and the changes of the competitive adsorption capacity, density distribution, adsorption selectivity, adsorption heat, and energy distribution were investigated. The results showed that the variation characteristics of the total adsorption of mixed gas were similar to those of pure gases, and the increase in the pressure led to an increase in the total adsorption, which also increased with the increase in the coal deterioration degree. The distribution ranges of the gas adsorption sites in coal with different metamorphic degrees were significantly different, with anthracite coal being the most widely distributed and long-flame coal being the least widely distributed. With the increase in the coal rank, the competitive adsorption selectivity of any proportion of CO 2 /CH 4 binary mixed gas increased. The difference in the equivalent adsorption heat of single-component gases CO 2 and CH 4 in the mixed gas increased with the increase in the coal metamorphism and decreased with the increase in the CO 2 gas proportion coefficient. This paper provides a theoretical basis for the application of CO 2 enhanced coal bed methane in coal seams with different metamorphic degrees. [ABSTRACT FROM AUTHOR]

• Wettability is a crucial parameter that determines storage capacity, containment security, and amount of stored H 2. • The effects of different parameters on wettability and, consequently, H 2 geo-storage are outlined. • Recent advances in rock/H 2 /brine interactions in various geological formations are reviewed. • The influence of organic material on H 2 geo-storage capacity is deliberated. • The role of liquid-gas interfacial tension, rock-fluid interfacial tension, and gas adsorption mechanism for H 2 is presented. Hydrogen (H 2) is currently considered a clean fuel to decrease anthropogenic greenhouse gas emissions and will play a vital role in climate change mitigation. Nevertheless, one of the primary challenges of achieving a complete H 2 economy is the large-scale storage of H 2 , which is unsafe on the surface because H 2 is highly compressible, volatile, and flammable. Hydrogen storage in geological formations could be a potential solution to this problem because of the abundance of such formations and their high storage capacities. Wettability plays a critical role in the displacement of formation water and determines the containment safety, storage capacity, and amount of trapped H 2 (or recovery factor). However, no comprehensive review article has been published explaining H 2 wettability in geological conditions. Therefore, this review focuses on the influence of various parameters, such as salinity, temperature, pressure, surface roughness, and formation type, on wettability and, consequently, H 2 storage. Significant gaps exist in the literature on understanding the effect of organic material on H 2 storage capacity. Thus, this review summarizes recent advances in rock/H 2 /brine systems containing organic material in various geological reservoirs. The paper also presents influential parameters affecting H 2 storage capacity and containment safety, including liquid–gas interfacial tension, rock–fluid interfacial tension, and adsorption. The paper aims to provide the scientific community with an expert opinion to understand the challenges of H 2 storage and identify storage solutions. In addition, the essential differences between underground H 2 storage (UHS), natural gas storage, and carbon dioxide geological storage are discussed, and the direction of future research is presented. Therefore, this review promotes thorough knowledge of UHS, provides guidance on operating large-scale UHS projects, encourages climate engineers to focus more on UHS research, and provides an overview of advanced technology. This review also inspires researchers in the field of climate change to give more credit to UHS studies. [ABSTRACT FROM AUTHOR]

Low permeability reservoirs are extremely sensitive to injected fluids because of small pore throat sizes and complex connections. Alkali sensitivity damage is the primary damage mechanism in low permeability reservoirs and strongly influences rock permeability. Therefore, it is significant to study alkali sensitivity damage mechanism to prevent capacity attenuation. In this paper, we propose a method combines macroscopic core flow experiments and microscopic mineral analysis to study alkali sensitivity damage mechanism. Core flow experiments are designed to evaluate the alkali sensitivity damage degree. QEMSCAN technique is introduced to quantitatively compare changes of porosity, mineral contents and distribution forms at inlet and outlet sides before and after alkali sensitivity damage. The results indicate that pore and throat plugging is the root cause of core alkali sensitivity damage. Big pores are plugged and segmented into significantly narrow flowing channels. The inlet side is plugged mainly by precipitates generated by the reaction of hydroxide and matrix minerals including dolomite, muscovite, and K-feldspar as well as dispersion of clay minerals in alkali environments including illite and chlorite. Meanwhile, the outlet side is mainly plugged by the dispersion and migration of clay minerals. Micro minerals are selected as the research object to study the alkali sensitivity damage at both inlet and outlet sides in low permeability reservoirs. This provides references for alkali sensitivity analysis in reservoirs with similar mineral compositions. Moreover, alkali sensitivity damage mechanisms are clarified at both inlet and outlet sides in the core flow experiment, which can be correlated to actual reservoirs near and far away from wells. Then specific measures corresponding to different types of reservoirs in terms of distances to wells can be taken to restore the damage and thus achieve the recovery of reservoir capacity. The method proposed in this paper is also applicable to other reservoir sensitivity damage, such as salt and acid sensitivity damage. [ABSTRACT FROM AUTHOR]

• - An all-fiber oxygen sensor based on wavelength modulation spectroscopy using a distributed feedback (DFB) laser diode operating near 761 nm is presented. • - The setup utilizes an anti-resonant hollow-core fiber (AR-HCF) as a small-footprint gas cell, providing a convenient and scalable alternative to conventional gas absorption cells. • - A detection limit of approximately 170 ppm for an averaging time of 5 s is demonstrated with a 1.2-m-long hollow-core fiber. • - The versatility of the sensing approach is highlighted by its ability to simultaneously detect oxygen and methane within the same hollow-core fiber, using spectral lines located more than 6000 cm−1 apart from each other. Optical detection of oxygen in A-band (near 13140 cm−1 or 761 nm) with tunable laser diode spectroscopy has been investigated and demonstrated in the past. However, as the demand for miniaturization of gas sensors increases, the hollow-core optical fibers emerge as a promising alternative to conventional large-volume gas absorption cells. In this paper we present a highly convenient, robust and scalable all-fiber setup that utilizes a 1.2 m silica anti-resonant hollow-core fiber as a small-footprint gas cell. Using tunable laser diode, the absorption spectra of oxygen in range from 13133.44 to 13148.12 cm−1 have been recorded. We also performed wavelength modulation spectroscopy of oxygen for samples with various oxygen concentrations and achieved a detection limit of approximately 170 ppm for an averaging time of 5 s. Furthermore, the versatility of the sensing approach is demonstrated by showing its ability to simultaneously detect oxygen at 761 nm and methane at 1651 nm inside the same hollow-core fiber. [ABSTRACT FROM AUTHOR]

Indiscriminate use of lithium battery packs will produce gases called thermal runaway gases, the most important of which are CO, CO 2 , and H 2. Doping transition metals on the MoSe 2 surface can effectively improve the gas detection effect of the substrate, and the application of transition metal clusters can further affect the adsorption process. In this study, transition metal Cu n and Pd n (n=1–3) are used to modify the MoSe 2 substrate to detect the target gases, The process is as follows: [Display omitted] • Different from previous single transition metal and metal oxide modifications, this paper proposes metal cluster modified MoSe 2 substrate. The Cu and Pd are selected as modified metals, and the maximum number of clusters is three. • The improvement effect of Cu n and Pd n (n = 1–3) clusters on the MoSe 2 substrate is obtained through the analysis of binding energy, bandgap, DOS and charge transfer, and the conductivity of the MoSe 2 substrate has been improved. • The adsorption process of thermal runaway gases on six modified substrates is considered. The adsorption performance of the target gases on five modified substrates is ranked as follows: CO>H 2 >CO 2. However, the adsorption effect of CO 2 on the Cu 3 -MoSe 2 substrate is better than that of H 2. • The analysis of molecular orbitals, work functions and sensitivity further verified the roles of Cu n and Pd n (n = 1–3) in detecting thermal runaway gases. The manuscript mainly explores the adsorption behavior and related parameters of Cu n and Pd n (n = 1–3) clusters modified MoSe 2 substrates for thermal runaway gases (CO, CO 2 , H 2) in lithium batteries by DFT. The modified structures are analyzed through E b , band structure, Q t , and DCD. Compared with the MoSe 2 bandgap (1.710 eV), Cu n and Pd n (n = 1–3) clusters modifications reduce the bandgap and become more compact. During the modification process, the metal clusters acquire electrons from the substrate and change the DOS of the substrate. The metal clusters improve the conductivity of the substrate. The adsorption and sensing properties between target gases and the substrates through the analysis of the E d , Q t , DCD, and DOS. The adsorption capacity of target gases on Cu-MoSe 2 , Pd-MoSe 2 , Cu 2 -MoSe 2 , Pd 2 -MoSe 2 , and Pd 3 -MoSe 2 substrates is ranked as follows: CO > H 2 > CO 2. The adsorption effect of Cu 3 -MoS 2 substrate on target gases is ranked as follows: CO > CO 2 > H 2. Analysis of molecular orbitals, work functions, and sensitivity can describe the adsorption effect of the substrates on the target gases. The results provide a theoretical basis for the development of gas sensors for detecting the operating status of lithium batteries. [ABSTRACT FROM AUTHOR]

[Display omitted] • Varied mesopore widths (5.1, 12.6, and 19.8 nm) of Co 3 O 4 nanoplates are achieved. • The Co 3 O 4 with 5.1 nm of mesopore width shows highest R g /R a value to toluene. • An actual detection limit is observed as low as 1 ppm. • Clear toluene selectivity against other gases is obtained. It remains a significant challenge for efficient detection of toluene vapor because of the low chemical reactivity. In this paper, the Co 3 O 4 nanoplates with various mesopore widths (5.1, 12.6, and 19.8 nm) onto their surfaces have been successfully achieved using a simple hydrothermal and followed annealing route. Moreover, the sensor based on this Co 3 O 4 nanoplate with mesopore width of 5.1 nm presents an obvious toluene-sensing response (including actual detection limit of 1 ppm, and excellent selectivity) at a low working temperature (140 °C). The improved toluene-sensing can be tracked from suitable mesopore size and specific catalytic activity of the Co 3 O 4 nanoplates, which are advantageous for gas adsorption and diffusion, as well as facilitating the rapid oxidation of toluene gas. This work announces a reliable strategy to detect low reactive gas by constructing rational mesopores-width over the catalytic oxide. [ABSTRACT FROM AUTHOR]

Understanding the permeability characteristics of coal under mining disturbance is crucial for ensuring coal mine safety and efficient gas extraction. Coal is a dual porosity medium consisting of matrix and fracture, and there are some differences in mechanics and permeability between matrix pores and fracture. However, research on the damage and gas seepage characteristics of dual-porosity coal is limited. In this paper, a coupled damage-permeability model considering matrix pores and fractures in coal is established, incorporating the influences of effective stress, gas adsorption, thermal expansion, and thermal cracking. And the reliability of the newly developed model was verified using experimental data of temperature and pressure variations under different stress boundary conditions. The results indicate that during the elastic stage, the total permeability and fracture permeability of coal exhibit a trend of decreasing and then increasing with pore pressure, while matrix permeability gradually increases. In the full stress-strain stage, the overall damage-permeability and fracture damage-permeability of coal exhibit an "S"-shaped variation trend with axial strain, while matrix damage-permeability shows a slow increasing trend. To accurately characterize the evolution of gas seepage in coal, contributions from matrix pores and fractures must be comprehensively considered, and the effects of gas adsorption, effective stress, thermal cracking, and thermal expansion on permeability cannot be ignored. Furthermore, through parameter sensitivity analysis, it is found that during the elastic stage, coal permeability decreases with an increase in the adsorption sensitivity coefficient and thermal expansion coefficient. In the full stress-strain process, coal permeability increases with an increase in the damage-permeability coefficient. The results of this study are of great significance for predicting the evolution of coal permeability in the working face ahead under mining disturbance. • The crack unit surface energy was introduced as a random distribution variable to characterize the crack-induced damage. • A damage-permeability model of dual-porosity coal under thermal-mechanical coupling was constructed. • The variation laws of permeability and damage variables in different structures were explored. • The effects of effective stress, gas adsorption, and temperature on dual-porosity permeability of coal were discussed. [ABSTRACT FROM AUTHOR]

• Exhaust gas CO 2 absorption (EGCA) system was installed on MW-scale marine engine. • EGCA performance was certified as per the test procedure described in NTC 2008. • 29/30 wt%(E2/E3 mode) of CO 2 absorption was obtained by EGCA system. • Pretreatment reactor needs to be combined for stable operation of EGCA system. The management of CO 2 emissions from fossil fuel-powered ships has been considered for complying with future enhancements in CO 2 emission regulations in the shipbuilding industry. These regulations are (or will be) enforced using indexes such as the energy efficiency design index, energy efficiency existing index, energy efficiency operational indicator, and carbon intensity indicator. Hence, developing technology for reducing CO 2 emissions from ships is necessary. This paper reports on the CO 2 absorption performance of a pilot-scale CO 2 capture system installed on a 1.075-MW HiMSEN 5H22CDF engine. The proposed technology is an exhaust gas CO 2 absorption (EGCA) system. Our CO 2 capture system is based on an exhaust gas cleaning system, which is already commercialized to reduce SO x emissions from ships that use heavy fuel oil. The CO 2 absorption performance of the EGCA system was evaluated following the test procedure described in the NO x Technical Code 2008 (NTC 2008). Under the certified test procedure described in NTC 2008, the EGCA system exhibited 29/30 wt% (E2/E3 test mode) of CO 2 absorption. On the basis of the test results, we expect that ships will be able to comply with future CO 2 emission regulations by using the proposed EGCA system. [ABSTRACT FROM AUTHOR]

[Display omitted] • The presence of SO 2 affects the bonding ability between chlorine atoms and alkali metals. • The presence of H 2 O can enhance the adsorption of NaHCO 3 to HCl. • Understanding of the competitive adsorption mechanism between HCl and SO 2. The utilization of sodium bicarbonate (NaHCO 3) as a solid reactant for the mitigation of acidic pollutants from industrial flue gas streams represents a straightforward and efficient process solution. The paper addresses the problem of medium- to high-temperature flue gas dechlorination by investigating the effects of base particle size, temperature, water vapour and different flue gas fractions on the removal of HCl from simulated flue gases by NaHCO 3 in a fixed-bed reactor, and the effects of the presence of SO 2 and H 2 O on the chlorination reactivity of NaHCO 3 are also investigated by density functional theory (DFT) calculations. The adsorption results implied that 300 °C was the optimum temperature for HCl removal by NaHCO 3 in a reaction system not affected by SO 2 or H 2 O; The higher the HCl concentration, the greater the HCl capture, but when the concentration is too high, due to the dense product layer makes the HCl gas molecules to the internal diffusion is blocked, the dechlorination effect becomes poor. The smaller the particle size of NaHCO 3 , the better the removal of HCl. In the system containing SO 2 , theoretical calculations based on density functional theory show that the presence of SO 2 affects the exchange of electrons between the Cl atoms in HCl and Na 2 CO 3 , and the bonding ability of the Na-Cl bond is weakened, thus weakening the dechlorination ability of Na 2 CO 3 ; However, SO 2 has little effect on HCl removal at the same concentration, due to the fact that HCl rapidly consumes the easily accessible surface of the absorber and SO 2 must diffuse deeper into the particles for the reaction to occur, suggesting a preferred reaction between HCl and NaHCO 3. After the addition of H 2 O, the adsorption energy of HCl on the surface of Na 2 CO 3 (2 0 0) was greater than the adsorption energy of SO 2 on the surface of Na 2 CO 3 (2 0 0), and HCl was preferentially adsorbed on the surface of Na 2 CO 3 (2 0 0), which preferentially reacted with the absorber. These findings help to elucidate the principle of HCl absorption by NaHCO 3 and the competition mechanism between HCl and SO 2 , and improve the theoretical knowledge of acid gas absorption by NaHCO 3. [ABSTRACT FROM AUTHOR]

• First demonstration of the detection of small amounts of methane at 8.014 µm. • Achieving the lowest detection limit of 0.063 ppb after an averaging time of 28.1 s. • Providing 1.9 times better selectivity than the frequently chosen absorption line at 7.67 µm. • Development of an OPO-DFG-based CRDS setup ensuring spectral measurements at various pressures. The paper describes the first demonstration of the detection of small amounts of methane using the 8.014 µm absorption line and cavity ring-down spectroscopy (CRDS) employing an optical parametric oscillator equipped with a differential frequency generator. The study confirmed the high stability of the system to pressure changes and the lowest detection limit of 0.063 ppb for an averaging time of 28.1 s. Experimental verification of methane spectra using a high-resolution vacuum FTIR spectrometer, tests of the developed setup presenting the influence of the wavelength resolution on the spectrum, and determining the detection limit using Alan's deviation were performed. Analysis of the achievable selectivity of methane sensors in individual water windows indicated in the range of 7.5–8.3 µm, taking into account the absorption bands of gases occurring in the standard atmosphere according to the HITRAN 2008 database was also described. Furthermore, the work presents an analysis of available solutions in the field of methane sensing, particularly on the range of longer infrared wavelengths, which showed a small number of described studies in the long wavelength infrared (LWIR) range and constituted a reference for the evaluation of the obtained result. [ABSTRACT FROM AUTHOR]

In this paper, THM model and coal molecular model are established to study the gas adsorption and desorption behavior in coal seam at different injection pressures. The results show that, the total energy decreases during the adsorption process and increases in the desorption process. CO 2 has a stronger adsorption capacity which is in a dominant position in the competition adsorption process, while N 2 is in a weak position. The order of the diffusion coefficient is N 2 >CH 4 (CH 4 –N 2) > CH 4 (CH 4 –CO 2) > CO 2. The diffusion coefficient does not necessarily increase with the increase of injection pressure. At the same injection pressure, the relative concentration of CH 4 in the CH 4 –CO 2 system is greater than that in the CH 4 –N 2 system, and injection of CO 2 to promote CH 4 desorption is significantly better than the injection of N 2. With the increase of injection pressure, the average relative concentration of CH 4 /CO 2 /N 2 in the vacuum layer increased. The optimal injection pressure for N 2 injection to promote CH 4 desorption is 2 MPa, and the reasonable injection pressure for CO 2 injection is 1–3 MPa. • THM model and coal molecular model are established to study the gas adsorption and desorption at different injection pressures. • The total energy of the system decreases during the adsorption process and increases in the desorption process. • The diffusion coefficient does not necessarily increase with the increase of gas injection pressure. • Relative concentration of CO 2 in the vacuum layer is lower than N 2 , the adsorption performance of CO 2 is greater than N 2. [ABSTRACT FROM AUTHOR]