CH4 Gas Research Articles

Effect of incorporation of multi-walled carbon nanotubes on the CO2/CH4 separation performance of sulfonated poly (ether ether ketone) / polyetherimide composite membranes using design of experiments and molecular dynamics simulation methods

Blend membranes were prepared based on sulfonated poly (ether ether ketone) (SPEEK) and poly (etherimide) (PEI) using different amounts of multi-wall carbon nanotubes (MWCNTs) (up to 2 wt%). PEEK has been sulfonated directly to reach 70 % degree of sulfonation. The manufactured membranes were examined by X-ray diffraction (XRD), scanning field emission electron microscopy (FESEM), Fourier transformed infrared spectroscopy (FTIR). The effect of the composition of SPEEK / PEI on membrane selectivity was investigated under different feed pressures (2 to 8 bar) and temperatures (25 to 55 °C). The values of selectivity and gas permeability were varied between the value of the individual polymers, fluctuating systematically with SPEEK / PEI content variation in the blends. TGA and tensile tests result obtained for prepared membranes shown that the hybrid membrane had good thermal and mechanical properties. The addition of MWCNTs to the blend led to simultaneously improve the selectivity and permeability of the pair gases of CO2 and CH4. The permeability of CO2, as well as CH4/CO2 selectivity for the membrane with the same weight of SPEEK and PEI, and 1 wt% of MWCNTs (coded SP55M1) experienced an increase of about 22 % compared with the neat membrane. Molecular dynamics simulations (MDS) were performed by employing the COMPASS force field to estimate the diffusivity of CH4 and CO2 gases through selected membranes. At last, with compared to the obtained experimetal data, the optimized nanocomposite membrane, integrated with MWCNTs was efficient, which makes it promising platform to separate mixed gase flows of CO2 and CH4 and other related environmental processes.

Tuning cyclopropanecarboxaldehyde clathrate hydrates for enhancement of methane storage

This study investigates the tuning behavior of guest molecules in gas hydrates to achieve an optimal balance between the storage capacity and moderate formation conditions for CH4 gas storage. A new structure II hydrate-forming agent, cyclopropanecarboxaldehyde (CPCAld), was examined, and the guest inclusion behavior, crystal structure, and tuning behavior of the binary (CPCAld + CH4) clathrate hydrate were analyzed using 13C solid-state nuclear magnetic resonance (NMR), Raman spectroscopy, and synchrotron powder X-ray diffraction (PXRD). The phase equilibria and CH4 storage capacity of the binary (CPCAld + CH4) clathrate hydrates were also investigated. The experimental results provide insights into the design and optimization of gas hydrate storage systems for CH4 gas and other applications. The study demonstrates the potential for tuning CH4 content in clathrate hydrates by adjusting the concentration of CPCAld from 0.5 mol% to 5.56 mol%, which enhanced the storage and transportation of CH4 gas. The CH4 storage capacity of the binary (CPCAld + CH4) clathrate hydrate at 3.0 mol% CPCAld concentration was approximately 25 % higher than that of (CPCAld + CH4) hydrate at 5.56 mol% of CPCAld concentration. Overall, the exploration of a new hydrate former, CPCAld, and the understanding of the tuning behaviors of the binary (CPCAld + CH4) hydrate provide important insights into enhancing the storage capacity and contribute to the development of efficient and safe CH4 gas storage technologies using gas hydrates.

Solvent-Directed Construction of a Nanoporous Metal-Organic Framework with Potential in Selective Adsorption and Separation of Gas Mixtures Studied by Grand Canonical Monte Carlo Simulations.

In this report, a microporous metal-organic framework of [Ca(TDC)(DMA)]n (1) and a two-dimensional coordination polymer of [Ca(TDC)(DMF)2 ]n (2), (TDC2- =Thiophene-2,5-dicarboxylate, DMA=N, N'-dimethylacetamide and DMF=N, N'-dimethylformamide) based on Ca(II) were designed by the effect of solvent, and X-ray analysis was performed for the single crystals of 1 and 2. Then, compound 1 was synthesized in three different methods and identified with a set of analyses. Compared to other adsorbents, MOFs are widely used in the field of adsorption and separation of various gases due to a series of distinctive features such as diverse and adjustable structures pores with different dimensions, high porosity and surface area with regular distribution of active sites. Therefore, the ability of 1 to uptake single gases (CH4 , CO2 , C2 H2 , H2, and N2 ) and separation of several binary mixtures of gases (CO2 /CH4 , CO2 /N2 , CO2 /H2 and CO2 /C2 H2 ), were investigated using Grand Canonical Monte Carlo simulations. Volumetric and gravimetric adsorption isotherms in various operating conditions, the isosteric heat of adsorption (qst ), the chemical potential for each thermodynamic state, and snapshots during the simulation process were reported in all cases. The results obtained from the adsorption simulation indicate that compound 1 has a high capacity for uptake of H2 (16 mmol g-1 ) and N2 (12.5 mmol g-1 ), CO2 (6.6 mmol g-1 ), C2 H2 (5 mmol g-1 ) and CH4 (1.5 mmol g-1 ) gases at 1 bar. It also performs well in separating CO2 in binary mixtures, which can be attributed to the presence of open metal sites in nodes of 1 and their electrostatic tendency to interact with CO2 containing the higher quadrupole dipole moment compared to other components of the mixture.

Influence of competitive adsorption, diffusion, and dispersion of CH4 and CO2 gases during the CO2-ECBM process

The displacement mechanisms of adsorbed CH4 by injected CO2 at high pressures in CO2-enhanced coalbed methane (CO2-ECBM) processes involve competitive adsorption, diffusion, and dispersion. Inherent coal heterogeneity and the complexity of the CO2-CH4 displacement model make CO2-ECBM modelling and optimal process design challenging. The pure gas isotherms and Langmuir adsorptions constants for CO2 and CH4 were determined using the manometric method. Notably, CO2 shows higher adsorption capacity than methane, and Langmuir volume (VL) for CO2 is 2 to 2.3 times that of methane. High pressure adsorption isotherms and experimentally determined diffusion coefficients set the sorption kinetics. The diffusion coefficient of CH4 for all four samples was in the range between 1.35×10-12 and 7.42×10-12 m2/s, while for CO2, it varied from 10.9×10-12 to 15.48×10-12 m2/s. The new concept of caucus time was introduced in the sorption kinetics of CO2 and CH4. Each sample has distinct caucus time and was positively correlated with Langmuir volumes of CO2 and CH4 with R2 > 0.9. The critical desorption pressure above which CH4 exhibits retrograde adsorption behaviour is evaluated from co-adsorption isotherms adopting Ideal Adsorption Solution Theory (IAST). The critical desorption pressure for the four samples were 1220, 460, 575 and 740 psi respectively. IAST also predicts a critical mole fraction (∼30 %) in the gas phase above which CO2 becomes the dominant adsorbed phase on coal surfaces. The results of Advective-Dispersion modelling at a larger scale illustrate the value of the Dispersion coefficient in forecasting and screening. Since the time available for diffusion versus dispersion depends upon flowrate, high values of dispersion coefficient can negatively influence favourable competitive adsorption expectations through higher operational cost in CO2 separation. This work suggests the existence of both an optimal operational pressure and flowrate to maximize the potential of CO2-ECBM technology demonstrated in competitive adsorption modelling.

Thermodynamic design and experimental study of a condensation recovery system for VOCs

During the storage and transportation process of crude oil on tankers, the light hydrocarbon components in liquid form have the tendency to evaporate and vaporize easily, resulting in wasted resources and environmental pollution. The current petroleum volatile organic compounds (VOCs) recovery system such as absorption and membrane separation applied to crude oil tankers is unable to fulfil the requirements of existing VOCs emission standards. In contrast, the condensation method of VOCs recovery technology has the benefit of a straightforward process principle, and the recovered liquid hydrocarbons can be utilized directly. It is thus vital to develop a condensation recovery system for petroleum VOCs that is compatible with crude oil tankers. To attain the condensation and recovery of the non-azeotropic gases, such as CH4, C2H6, C3H8, and N2 in the feed gas, this paper proposes a low-temperature VOCs condensation recovery system with graded cooling and liquefaction separation for crude oil tankers. The proposed system initially utilizes a R404A/R23 double-stage cascade refrigeration cycle to cool the VOCs below −75 ℃ to liquefy most heavy hydrocarbons. Then, a low-temperature nitrogen expansion cooling cycle is utilized to cool the VOCs to approximately −160 °C to recover the remaining light hydrocarbons. The condensation process is simulated by Aspen HYSYS to study the variable operating conditions. The recovery of total hydrocarbons in the outlet tail gas in the simulation results is analyzed and found to be up to 95.50 %. Under identical refrigeration capacity circumstances, decreasing the inlet pressure, increasing the inlet flow rate, and increasing the methane mole fraction in VOCs component, all lead to declining trends of total hydrocarbon recovery and methane recovery rate. Specifically, the effects of four different hydrocarbon component ratios on total hydrocarbon recovery and total cooling load are investigated at a constant nitrogen content and refrigeration capacity. Furthermore, the optimal design and analysis process for the flow path section of the turbine expander under the cryogenic conditions is discussed. The results demonstrate that the outlet temperature through the turbine expander is at least −172.1 °C, and the cooling capacity can be up to 4.5 kW with a margin of 80 %. Finally, through the comprehensive VOCs condensation recovery experiments, the proposed system successfully achieves the liquefied separation and recovery of CH4, C2H6, and other hydrocarbons. The recovery rate of the total hydrocarbons in the outlet tail gas reaches 96.21 %, conforming to the VOCs emission standards and regulations. The findings of this study provide a viable technical resolution in the field of petroleum VOCs recovery from crude oil tankers.

Mechanism of carbon nanotube growth in expanded graphite via catalytic pyrolysis reaction using carbores P as a carbon source.

Carbon nanotubes (CNTs) had potential applications in energy conversion and storage devices, and it could be prepared by expanded graphite loaded with catalyst at high temperature, however, the mechanism of carbon nanotube growth in expanded graphite need further confirmation. In this work, carbon nanotubes' in situ growth in expanded graphite (EG) were prepared via catalytic pyrolysis reaction using carbores P as a carbon source and Co(NO3)3•6H2O as a catalyst. The results of X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray spectroscope (EDS) indicated the carbon nanotubes could generate in, EG with the presence of carbores P as a carbon source and cobalt nitrate as a catalyst. More interestingly, the growth mechanism of carbon nanotubes could be concluded by the results of differential thermal analysis-thermogravimetry-mass spectrometry (DTA-TG-MS) and X-ray photoelectron spectroscopy (XPS) analysis. The pyrolysis products of carbores P were mainly hydrocarbon gas such as CH4 gas, which reacts with Co(NO3)3·6H2O catalyst to reduces CoOx to Co particles, then the carbon form pyrolysis was deposited the on the surface catalyst Co particles and, after continuous solid dissolution and precipitation, carbon nanotubes were at last generated in EG at last.

Annual fluctuation of gas concentration within the landfill surface layer in a tropical climate: A case study of a municipal wasteyard

AbstractThis study looks at the annual variations in landfill gas concentrations within the surface layer of the dump as well as the effect of climatic factors on these variations under the tropical climate. The experiment was carried out at part of the Karadiyana landfill, Sri Lanka, containing old mixed municipal solid waste covered by vegetation. The gas concentrations of the landfill surface layer were measured from three gas wells established on the dump surface layer, which contains 2.5 m depth, throughout the year with the measuring of climatic factors. The results show the annual fluctuation of temperature, cumulative rainfall, relative humidity, and atmospheric pressure were 27–42°C, 66.7–357.7 mm, 24.7%–78.2%, and 999.5–1014 mbar around the studied landfill area, and the average concentration value of the CH4, NH3, H2S, and VOCs gases were 18.94 ± 11.49%, 15.48 ± 15.17 mg m−3, 15.06 ± 19.02 mg m−3, and 0.83 ± 0.99 mg m−3, respectively. The rainfall and atmospheric temperature were significant metrological factors influencing the surface layer gas concentrations and showed a significant positive correlation with cumulative rainfall and a negative correlation with atmospheric temperature. The relative humidity shows a moderate positive correlation, and there was no evidence of a considerable impact of atmospheric pressure on the surface layer concentrations. Annual fluctuation is a critical factor for landfill gas emission quantification, and surface layer concentration variation can be used to study the emission fluctuation by considering their relationship.

Assessment of the in situ biomethanation potential of a deep aquifer used for natural gas storage

In response to the challenges of sustainable development and the H2 sector, it is foreseeable that H2 will be stored into geological storage, such as deep aquifers. However, CO2 evolves in deep aquifers because it may be naturally present there; it may also be a constituent of the stored gas mix, or could even be voluntarily stored in the context of the fight against global warming. Autochthonous microorganisms can consume them as sources of energy and carbon (methanogens, (homo)-acetogens and sulfate-reducers). This was already demonstrated in a previous experiment (Haddad 2022) and under operating conditions (Lobodice, Czech Republic ; Smigan 1990). Understanding these mechanisms and quantifying them appear necessary to assess the modifications generated by this type of microorganisms on the properties of the gas. The methanogenesis reaction (CO2 gas + 4H2 gas → CH4 gas + 2H2O liquid) induces a lowering of pressure, since 5 gas molecules are transformed into a single gas molecule: CH4 (water being condensed at subsurface conditions). In situ biomethanation technique could represent a potential on several scales larger than conventional catalytic or biological methanation reactors, due to the very large reservoir volumes involved. Biomethanation in geological reservoirs would enable us to reduce our consumption of fossil fuels, so as not to emit more CO2, while meeting the growing energy needs of a region and ensuring its independence from hydrocarbon-producing countries. A deep aquifer already used as UGS was selected for this study. Formation waters from 17 control wells in this aquifer (Fig. 1) were sampled to assess the potential activity of indigenous methanogenic populations, as well as sulfate-reducers. Despite relatively low sulfate concentrations for a deep aquifer (0.025-1.35 mM), sulfate reducers were found at all sites targeting and quantifying the dsrB gene, which is characteristic of this metabolic group (between 1.8∙101 ±2.0x100 and 1.3∙104 ±2.0∙103 dsrB gene copy numbers.mL-1). In contrast, methanogenic archaea based on the mcrA gene quantification were detected at only 10 of the 17 sites (up to 4.3∙102 ±8.3∙101 mcrA gene copy numbers.mL-1). The choice was made to focus the rest of the study on 7 of these 10 sites. The potential for methanogenesis was assessed on cultural tests with formation water alone or supplemented with calcite (CaCO3), a mineral present in the formation. Results indicate that initial times and controls are controlled by the sulfate variable, since the latter was not consumed by sulfate-reducers. Biotic trials in the presence of calcite and H2/CO2 (abiotic controls and final times) are logically characterized by higher concentrations of calcite, bicarbonate and calcium, but this is not the case for trials in the presence of H2 alone. We therefore deduce that methanogenesis took place mainly via gaseous CO2, but that without the latter, calcite was a source of carbon for lithoautotrophs. Cultures incubated with H2 as the sole gas phase have the highest methane concentrations, logically associated with the lowest sulfate concentrations (consumed by sulfate-reducers), the lowest Eh (probably due to the presence of sulfides) and more alkaline pH values up to 10 (which may have led to precipitation of carbonate and calcium ions). All the sites studied showed sulfate consumption and methane production. Analysis of taxonomic diversity (MiSeq; 16S rRNA gene V4-V5) showed the dominance of three genera of sulfate-reducers with Thermodesulfovibrio-Desulfovibrio-Desulfotomaculum and methanogenic populations belonging to the Methanobacterium genus. These initial results show a strong potential of in situ biomethanation for the deep aquifer studied. All these experiments were carried out at near-atmospheric pressure, and the results still need to be confirmed and refined in the laboratory under conditions that simulate real-life conditions as closely as possible (rock, pressure, nature of gases).

Adsorption and sensing of dissolved gases in transformer oil by Ni-modified h-BN monolayer: A DFT study

The use of high-sensitivity gas sensors to detect dissolved gases in the oil is a repeatable and effective method to assess the operating condition of a transformer. Based on DFT calculations, analysis of the adsorption and sensing performance of Ni-doped h-BN monolayer on three major dissolved gases H2, CH4 and C2H4 in transformer oil were performed. The gas adsorption and sensing mechanisms were explored using the geometry optimization, adsorption energy, band structure, charge transfer, deformation charge density, molecular orbitals, density of states and recovery time. The results show that the doped modified Ni-BN has the sensing ability for all three gases. The adsorption energies for H2, CH4 and C2H4 are −1.418, −1.300 and −2.633 eV, respectively. In particular, it has the best adsorption capacity for C2H4, but is difficult desorb with a desorption time of 4.39 × 1014s at 498 K; the adsorption performance for CH4 is excellent, while the desorption time is 14.10 s when the temperature is 498 K. In conclusion, this work provides a reference for the selection of materials for the detection of dissolved gases in transformer oil and provides theoretical guidance for the development of Ni-BN gas-sensitive sensors.

Extremely deuterium depleted methane revealed in high-temperature volcanic gases

Active volcanoes often discharge hot (T ≫ 100 °C) magmatic gases whose original composition has been modified through partial interaction with an externally fed hydrothermal system. The study of methane (CH4) in these volcanic discharges may provide useful information on the interplay between deep magmatic gases and shallow circulation of hydrothermal fluids. However, the origin of CH4 in high-temperature volcanic gases and the factors exerting control on its abundance and stable isotope composition are still largely unknown. Here, we present the abundances and stable isotopic composition of CH4 in hot (99–387 °C) volcanic gases from the La Fossa volcanic crater of Vulcano Island (Southern Italy).Our investigation revealed low (<1.5 μmol/mol) CH4 concentrations and an extraordinarily large variability in CH4 stable isotopic composition, with δ13C and δ2H values being positively correlated and varying from −35 to −9.2 ‰ and −670 to −102 ‰, respectively. Notably, CH4 isotopes measured at Vulcano almost encompasses the global-scale variability observed in natural fluids, with δ2H values ≤ −500 ‰ being the first ever reported in nature. Gases showing extremely negative δ13C-CH4 and δ2H-CH4 values systematically display higher CH4 abundances.We propose two possible scenarios in order to explain the observed huge variation in δ13C and δ2H: (1) mixing of 13C- and 2H-depleted CH4 with 13C- and 2H-enriched CH4 of thermogenic origin formed under hydrothermal conditions; (2) post-genetic removal and isotopic alteration of 13C- and 2H-depleted CH4 occurring during the ascent of volcanic gases. Comparing our dataset with available isotopic data from naturally occurring and artificially produced CH4, a thermogenic origin for the isotopically light CH4 seems unlikely. We postulate that the 13C- and 2H-depleted CH4 may have formed via kinetically-controlled abiotic synthesis through CO (or CO2) hydrogenation reactions in the hot ascending gas phase, possibly at temperatures intermediate between those typical of magmatic and hydrothermal conditions. Further investigations of methane in high-temperature volcanic gases are necessary to test this hypothesis.

Estimated mangrove carbon stocks and fluxes to inform MRV for REDD+ using a process-based model

Mangrove forests are important due to their strong capability for carbon storage, especially in soils. Understanding carbon dynamics in these forests is fundamental to estimate their roles in carbon storage and mitigating climate change. This study used a process-based model, MCAT-DNDC, to assess mangrove carbon sequestration and fluxes at a 30-m spatial resolution in three African countries, Gabon, Mozambique and Tanzania. The simulated above- and below-ground biomass at inventory plots in each country was approximate to actual observations with mean errors <5% for aboveground biomass and <8% for belowground biomass, indicating that the MCAT-DNDC model can be a useful tool for assessing mangrove carbon storage and fluxes. The results from assessing mangrove carbon storage and fluxes for the three countries showed that the mangroves in these countries are large carbon pools, they export large amounts of dissolved and particulate carbon components to riverine and oceanic ecosystems, and they bury a large amount of carbon in soils. However, soil-borne greenhouse gases CO2, CH4 and N2O fluxes from mangrove forest lands were low. There were large differences in all mangrove carbon components among the mangroves in the three countries, indicating that regional or global mangrove carbon stocks estimated using a process-based model may be better than the extrapolations using limited inventories.

Characterization of a novel two-stage high ash coal gasifier for low tar and high calorific value gas

The high ash content of coal poses two critical challenges in conventional gasifiers: (a) ash agglomeration and (b) low-quality syngas. The ash agglomerations are caused by the interaction of alkali and alkaline earth metals with other inorganic compounds, localized temperature generation, and unoptimized process parameters. Whereas low-quality gas is due to moderate temperature operations and the mixing of syngas with pyrolysis products. Recognizing these challenges, the current work discusses the design, development, and performance characterization of a novel two-stage gasification system that strategically segregates oxidative pyrolysis in a cyclone reactor and oxy-steam char gasification in a packed bed reactor. Such segregation provides explicit control over parameters like local temperatures, particle and gas residence time, enabling the configuration to handle coal with a wide range of ash content. Thermodynamic analysis and performance characterization experiments have been carried out with varied temperatures, oxygen, and steam flow rates. While operating the system up to 950˚C, there was no indication of clinker formation. The gravimetric tar content was found 52 ± 3 mg/Nm3. The concentration of CO, CO2, CH4, and H2 in the product gas during experiments was 40 ± 5, 20 ± 5, 2 ± 1, and 45 ± 5%, respectively. The carbon conversion was greater than 77%, with further scope for improvement.

Experimental research on bimetallic ion crosslinked gel to inhibit the spontaneous combustion of coal

To address the environmentally friendly issue of fire prevention and extinguishing materials in coal mines, a new type of mine fire prevention and extinguishing gel was prepared using sodium carboxymethyl cellulose (CMC) as the matrix, ferro aluminum citrate (Fe-AlCit) as the cross-linking agent, and gluconic acid-δ-lactone (GDL) as the pH modifier. The preferred ratio was 2.5 % CMC + 4 % Fe-AlCit + 2 % GDL of No. 23 gel material by gelation time, thermal stability, strength, and permeability performance tests. The results show that the gelation time of No. 23 gel was 10 min, and its complete water loss time was 1.97 times that of water at a high temperature of 180 °C. The gel for sealing the surface of the coal body still maintained good stability after two weeks. Furthermore, A metal coordination bond favorable to the stability of gel is formed by the carboxylate ion in CMC and the double high-valent metal ions Fe3+ and Al3+ ionized by Fe-AlCit. No. 23 gel exhibits excellent fire prevention and extinguishing properties. The temperature-programmed test showed that the CO and C2H4 gas inhibition rate of the coal sample treated with No. 23 gel reached 33.42 % and 56.86 % at 220 ℃, and the activation energy growth rate reached 26.5 % and 21.1 % in the first and second stages, respectively. The fire extinguishing test indicated that No. 23 gel can significantly reduce the temperature of the coal sample and extinguish the coal fire quickly. The study is useful to develop efficient and environmentally friendly coal mine fire prevention and extinguishing materials.

Atomic-level prediction of V–Ni–Al, V–Ni–Co and V–Ni–Fe ternary alloys as highly selective hydrogen separation membranes

VB-group-based ternary alloys membranes for hydrogen separation have attracted great attention because of their superiorities on selectivity and permeability of hydrogen. However, atomic-scale hydrogen separation properties of the ternary alloys are still not studied, further related study is critical for developing high-performance V–Ni-based alloys membranes. In this work, molecular dynamics (MD) and first-principles calculation are incorporated to predict performances of V–Ni–Al, V–Ni–Fe and V–Ni–Co ternary alloys for separation of H2 from N2, CO2, CO, CH4, H2O and H2S mixed gases. Based on calculations of adsorption properties, diffusion energy barrier, selectivity and charge density difference, it reveals that the alloys membranes show excellent permeance and selectivity for separation of hydrogen gas. In particular, V–Ni–Al membrane presents superior diffusion and permeability properties for hydrogen gas. Our calculations provide an insight into atomic-level mechanism of V–Ni–Al, V–Ni–Fe and V–Ni–Co alloys as high-performance hydrogen separation membranes.

Characterization and gasification of end-of-life banknotes rich in cotton content

Many central banks are reviewing their environmentally sustainable activities, including the disposal of end-of-life banknotes, within the scope of green finance policies aimed at reducing environmental impacts. The total amount of banknote production waste and end-of-life (non-reusable) banknotes is estimated to exceed 185.000 tons per year worldwide. End-of-life banknotes are commonly disposed of as combustion, incineration for energy recovery, and landfill. In this study, the characterization and gasification of end-of-life banknotes rich in cotton content, which are classified as lignocellulosic waste, were investigated to bring them into the economy more effectively. The proximate, calorific value, lignocellulosic, elemental, and metal analyses were performed as characterization tests. Thermogravimetric analysis was performed at six different heating rates from 5 to 30 °C. The gasification experiments were carried out in a laboratory-scale fluidized bed reactor. With the gas analyzer, CO, CO2, CH4, H2, and O2 compositions as the mole fraction were determined simultaneously. The effects of temperature, particle size, and H2O/O2 ratio at the inlet intake on the experimental mole fractions were examined. The gasification main reactions that could be effective in gas composition were examined. The cotton-based banknote sample presented high levels of calorific value, C, O, H, cellulose, and lignin concentrations. The sample contained various transition metals such as Fe, Cu, Co, and Cr, which can be used as catalysts in gasification. The activation energy was calculated as 171.13 kJ/mol according to Kissinger method. In gasification experiments, the production of CO (12.11 %) and H2 (8.77 %) in a high composition was carried out.

GAS COMPOSITION AND MICROORGANISMS OF GROUND ICE IN RUSSIAN ARCTIC

Link for citation: Butakov V.I., Slagoda E.A., Zavatsky M.D., Ivanov V.I. Gas composition and microorganisms of ground ice in Russian Arctic. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 9, рр. 63-75. In Rus. Relevance. The increase in the concentration of greenhouse gases in the atmosphere is a fundamental problem on a planetary scale. The source of greenhouse gases in the subsurface horizon of soil can be both deep deposits of hydrocarbons and organic matter processed by microorganisms during the thawing of the ice-rich soil. To determine the source of the gas it is necessary to examine both its quantity and composition and the microorganism content in the subsurface ice. Taking into account the dynamic development of the energy complex in the north of Western Siberia it is necessary to take into account the geotechnical risks associated with the release of greenhouse gases from frozen deposits. Purpose: to study the composition and identify the sources of greenhouse gases in the ice and the ice-rich soil on account of the ice formation conditions and the microorganism content. Objects: ice wedge, hydrogenic and segregational genesis of ice, ice-rich soil of northern Western Siberia and Central Yakutia, collected by expeditions Earth Cryosphere Institute, Tyumen scientific center SB RAS in 2011–2021. Methods of research and interpretation of chemical composition. The structure of frozen deposits has been investigated by cryolitological methods. The monoliths of the ice and the frozen deposits were stored at –18 °C. Gas was extracted from the monoliths with the determination of volume fraction by thermovacuum degassing method. The composition of gases is determined by gas chromatography. Normalization of the gas composition with solubility values in water was carried out. Volume fractions of gas in free and dissolved forms was calculated. The data processing were implemented by means of «Geochem Anomaly» program. Cultivated psychrophilic microorganisms were studied by seeding on nutrient media; the total number of microorganisms was determined by epifluorescent microscopy. Results. The contents of N2 (74,9–87,8 %), O2 (11,7–20,3 %), CO2 (0,01–3,28 %), CH4 (0,003–7, 35 %), H2 (0,001–0,035 %) and hydrocarbons with an atom content from 2 to 6 (2,0×10–5–2,8×10–3 %) are determined in ice and ice-rich soil. The value of N2 and O2 in the gas composition of ice is close to atmospheric air. The ice has wide variations in gas saturation (1,1–21,1 %), CH4 and CO2 content. The freezing of gas-saturated solution occurred for the ice formation, part of the air was in a free form (from 30 to 75 %). Calculated indexes CH4/(C2H6+C3H8) and C2H6/C2H4 indicate biogenic hydrocarbon genesis. The composition of gas bubbles is recalculated for the volume of the entire sample: CH4 content is insignificant in ice wedge, closed-cavity ice and icing (averages 51, 81 and 1 ppmV, respectively). The low amounts of CH4 could be produced by forming these types of ice from the sediments of the active layer, as the dependence of the gas composition on the peat element amount is established. CH4, CO2 and H2 contents increased in samples with peat elements. In interbedding ice the CH4 content is high (216 ppmV). CO2 (up to 3007 ppmV) was accumulated in the texturing ice, and hydrogenic wedge-shaped ice showed high levels of CH4 (up to 4032 ppmV) as the ice was frozen in an enclosed volume. The ice of peat mound has a maximum content of CH4 (15545 ppmV) and high CO2 (2466 ppmV); inclosing sediments flooded with marginal-marine waters are the source of high values of CH4 and CO2. The cultivated psychrophilic microorganisms were identified in the surface ice, and their maximum quantities were identified in segregated formations – up to 1680 KOU/ml, in textural ice – up to 1032 KOU/ml. High concentrations of greenhouse gases are found in frozen peat – CO2 (1075 ppmV), H2 (9 ppmV), CH4 (262 ppmV) and other hydrocarbons due to activity of microorganisms, which results in accumulation of these gases. High gas saturation and CH4 and CO2 levels indicate the formation of gaseous composition by both aerobic and anaerobic microorganisms.

Understanding the Thermal Degradation Mechanism of High-Temperature-Resistant Phthalonitrile Foam at Macroscopic and Molecular Levels.

Polymer foam, a special form of polymer, usually demonstrates some unexpected properties that rarely prevail in the bulky polymer. Studying the thermal degradation behavior of a specific polymer foam is important for its rational design, quick identification, objective evaluation, and industrial application. The present study aimed to discover the thermal degradation mechanism of high-temperature-resistant phthalonitrile (PN) foam under an inert gas atmosphere. The macroscopic thermal decomposition of PN foam was carried out at the cost of size/weight loss, resulting in an increasing number of open cells with pyrolyzation debris. Using the TGA/DTG/FTIR/MS technique, it was found that PN foam involves a three-stage thermal degradation mechanism: (I) releasing gases such as H2O, CO2, and NH3 generated from azo-containing intermediate decomposition and these trapped in the closed cells during the foaming process; (II) backbone decomposition from C-N, C-O, and C-C cleavage in the PN aliphatic chain with the generation of H2O, CO2, NH3, CO, CH4, RNH2, HCN, and aromatic gases; and (III) carbonization into a final N-hybrid graphite. The thermal degradation of PN foam was different from that of bulky PN resin. During the entire pyrolysis of PN foam, there was a gas superposition phenomenon since the release of the decomposition volatile was retarded by the closed cells in the PN foam. This research will contribute to the general understanding of the thermal degradation behavior of PN foam at the macroscopic and molecular levels and provide a reference for the identification, determination, and design of PN material.

Update on Emeralds from Kagem Mine, Kafubu Area, Zambia

Kagem emerald mine in Zambia is deemed to the largest open-pit emerald mine with extremely high economic value and market share in the world. To meet the market demand for tracing the origin of emeralds, 30 emeralds from the region were tested, and some discoveries were made compared to previous studies. This study provides a full set of data through standard gemological properties, inclusions, color characteristics, advanced spectroscopic and chemical analyses, including Raman, micro micro-UV-Vis-NIR, FTIR, and LA-ICP-MS. The most common inclusions in Kagem emeralds are two-phase inclusions, which exhibit elongated, hexagonal, oval, irregular shapes or appear as negative crystals with incomplete hexagonal prism. These inclusions consist of H2O or H2O + CO2 (liquid) and CO2 + N2 or CO2 + N2 + CH4 (gas). Mineral inclusions typically include actinolite, graphite, magnetite, and dolomite. Black graphite encased in actinolite in Kagem emeralds is first reported. The FTIR spectrum of Kagem emeralds reveals that the absorption of type II H2O is stronger than that of type I H2O, indicating the presence of abundant alkali metals, which was confirmed through chemical analysis. Kagem emeralds contain high levels of Na (avg. 16,440 ppm), moderate-to-high Cs (avg. 567 ppm), as well as low-to-moderate levels of K (avg. 185 ppm) and Rb (avg. 14 ppm) concentrations.

Effect of gypsum waste inclusion on syngas production during CO2-assisted gasification of waste tires

Syngas production from co-gasification of waste tires and different amounts of drywall waste gypsum (CaSO4) was investigated using CO2 as the gasifying agent in a lab-scale reactor. Gypsum is known to react with carbon feedstocks through solid–solid reactions to produce CaS and CaO, CO, and CO2. The presence of gypsum in waste tires increased the syngas yield from the conversion of char and tars. Gypsum addition to the waste tire also increased syngas quality from increased syngas energy yield. The overall yield of syngas increased by up to 55% while the energy yield (MJ/ kg feedstock) improved by 40% with gypsum addition. The product gas yield, energy, H2, and CH4 yields increased with gypsum addition while CO only increased for lower gypsum concentrations. Higher gypsum addition increased CO2 yields. Aspen Plus simulation results revealed that for waste tires, temperatures < 1200 °C suppressed the transformation of sulfur present in gypsum into SO2 for all waste tires to gypsum feed mass ratios. At 50 wt% gypsum concentrations, only 2% of the sulfur in the feedstock was transferred into SO2. The results showed improved syngas yield and quality, without any increase in sulfur emissions showing the benefits of gypsum waste incorporation in waste tire gasification.

Life in the dark: Impact of future winter warming scenarios on carbon and nitrogen cycling in Arctic soils

The high Arctic region is warming faster than other areas globally, with widespread decreases in snow cover and longer growing seasons. This is expected to greatly influence plant-microbial carbon (C) and nitrogen (N) cycling and thus ecosystem functioning, particularly when soils remain unfrozen during the dark winter period and no photosynthesis is possible. To better understand this response, we studied the effects of different winter warming scenarios on soil C and N dynamics. We collected intact soils cores from two contrasting biomes from Svalbard, namely a moss-dominated peat mire and purple saxifrage-dominated dry tundra heath. In the laboratory, we used an Arctic annual light regime and three contrasting winter temperature regimes to simulate a range of climate scenarios: (i) current climate in which the soils were frozen in winter and thawed in the summer, (ii) a year 2050 regime in which the soils were both frozen and thawed in winter, and (iii) a year 2100 regime in which the soils remained unfrozen during winter. We monitored greenhouse gas (GHG) emissions (CO2, CH4 and N2O) and nutrients in soil solution (DOC, NO3−, NH4+, P) over a one-year period. In the peat mire, warmer winters increased CO2 emissions due to increased microbial activity but had little effect on methane or N2O fluxes. Warmer winters also decreased dissolved organic carbon and nutrients in soil solution. In the dry tundra heath, warmer winters increased nitrate availability but did not greatly alter CO2, CH4 or N2O gas fluxes or other nutrients. Warming in the dry tundra health induced earlier spring flowering and shifts in vegetation composition. Overall, we present clear evidence that warmer winter conditions are likely to alter C and N cycling in Arctic soils, with implications for plant productivity and vegetation community composition.