Main Gas Components Research Articles

High-resolution observations of 12CO and 13CO J = 3 2 towards the NGC 6334 extended filament. I. Emission morphology and velocity structure

NGC 6334 is a giant molecular cloud (GMC) complex that exhibits elongated filamentary structure and harbours numerous OB-stars, H II regions, and star-forming clumps. To study the emission morphology and velocity structure of the gas in the extended NGC 6334 region using high-resolution molecular line data, we made observations of the 12CO and 13CO $J=3 2$ lines with the LAsMA instrument at the APEX telescope . The LAsMA data provided a spatial resolution of 20" (sim 0.16 pc) and sensitivity of 0.4 K at a spectral resolution of 0.25 km $. Our observations revealed that gas in the extended NGC 6334 region exhibits connected velocity coherent structure over sim 80 pc parallel to the Galactic plane. The NGC 6334 complex has its main velocity component at $ -3.9$ km $ with two connected velocity structures at velocities $ -9.2$ km $ (the `bridge' features) and $ km $ (the northern filament, NGC 6334-NF). We observed local velocity fluctuations at smaller spatial scales along the filament that are likely tracing local density enhancement and infall, while the broader V-shaped velocity fluctuations observed towards the NGC 6334 central ridge and G352.1 region located in the eastern filament EF1 indicate globally collapsing gas onto the filament. We investigated the 13CO emission and velocity structure around 42 WISE H II regions located in the extended NGC 6334 region and found that most H II regions show signs of molecular gas dispersal from the centre (36 of 42) and intensity enhancement at their outer radii (34 of 42). Furthermore most H II regions (26 of 42) are associated with least one ATLASGAL clump within or just outside of their radii, the formation of which may have been triggered by H II bubble expansion. Typically towards larger H II regions we found visually clear signatures of bubble shells emanating from the filamentary structure. Overall the NGC 6334 filamentary complex exhibits sequential star formation from west to east. Located in the west, the GM-24 region exhibits bubbles within bubbles and is at a relatively evolved stage of star formation. The NGC 6334 central ridge is undergoing global gas infall and exhibits two gas bridge features possibly connected to the cloud-cloud collision scenario of the NGC 6334-NF and the NGC 6334 main gas component. The relatively quiescent eastern filament (EF1 - G352.1) is a hub-filament in formation, which shows the kinematic signature of global gas infall onto the filament. Our observations highlight the important role of H II regions in shaping the molecular gas emission and velocity structure as well as the overall evolution of the molecular filaments in the NGC 6334 complex.

A pilot study on a 30 t/h biomass gasification-combustion plant

As a renewable energy with zero carbon emission, the utilization of biomass has attracted widely studied. One of the most effective methods is to gasify the biomass into high-quality gas fuel. In the recent years, the majority of research on biomass gasification is conducted in the laboratory. However, it lacks the research in engineering application scale. In this work, a biomass gasification-combustion plant was designed and built to provide the industrial steam with a rate of 30 t/h for a food industrial park. The agricultural and forestry waste biomass was gasified in a gasifier, and then the product gas combusted in a boiler to supply the steam. The characteristics of the product gas from the gasifier were studied. The corrosion and pollutants in the combustion process were investigated. In the gasification process, the main components of the product gas are CO, H2 and CH4. CO and H2 account for 29.55 vol%-30.56 vol% and 11.65 vol%-15.35 vol%, respectively. The calorific value of the product gas is 5.88–6.29 MJ/m3. The tar concentration is 110.58–155.07 g/Nm3. At the outlet of the boiler, the concentration of the filterable particulate matter is 300.25 mg/Nm3, and the particle size is concentrated at 1.00–2.50 μm. The concentration of the condensable particulate matter (CPM) is 157.14 mg/Nm3, and the proportion of water-soluble ions in CPM is 86.36 wt%. The concentration of Cl−, SO42-, NH4+ and Na+ in CPM is relatively high, with the values of 28.83 mg/Nm3, 10.29 mg/Nm3, 7.46 mg/Nm3, and 5.06 mg/Nm3, respectively. During the half-year running, the ash deposition and corrosion were detected in the boiler heating surface and the economizer. The ash deposit in the boiler is mainly composed of the sulfate and silicate, such as CaSO4, Zn2SO4, Na2SO4 and K3Na(SO4)2. The ash deposit in the economizer is primarily composed of the sulfate and a small amount of alkali metal chloride. The flue gas reaches the emission requirement after passing through the pollution control devices and can be discharged into the atmosphere.

Investigating the Influence of Flue Gas Induced by Coal Spontaneous Combustion on Methane Explosion Risk

During the process of coal spontaneous combustion (CSC), a plethora of combustible gases alongside inert gases, such as CO2, are copiously generated. However, prior investigations have regrettably overlooked the pivotal influence of inert gas production on the propensity for methane explosions during CSC. To investigate the impact of the flue gas environment generated by CSC, containing both combustible and inert gases, on the risk of methane explosion, a high-temperature programmed heating test system for CSC was employed to analyze the generation pattern of flue gas. It was found that CO, CO2, and CH4 were continuously generated in large quantities during the process of CSC, which are the main components of CSC flue gas. The effect of the concentration and component ratio (CCO2/CCO) of the flue gas on the methane explosion limit was tested. It was found that the CSC flue gas led to a decrease in the methane explosion limit, and that the explosion limit range was facilitated at 0 < CCO2/CCO < 0.543 and suppressed at CCO2/CCO > 0.543. As the temperature of CSC increases, the risk of methane explosion is initially suppressed. When the coal temperature exceeds 330~410 °C, the explosion risk rapidly expands.

Numerical investigation of stable combustion at ultra-low load for a 350 MW wall tangentially fired pulverized-coal boiler: Effect of burner adjustments and methane co-firing

In the context of deep peak regulation, utility boilers are often required to operate at ultra-low loads, significantly deviating from their designed conditions, which can lead to unstable combustion or even furnace flameout. However, their operating characteristics at 20 % or even lower loads remain unclear. This study focuses on a 350 MW wall tangentially fired pulverized-coal boiler, exploring its combustion characteristics and pollutant emission patterns at 20 % ultra-low load. Through numerical simulation analysis of 14 different combustion scenarios, this research investigates the impacts of burner arrangements, burner horizontal swing angles (ranging from 5° to 20°), and methane (CH4) co-firing ratios (ranging from 0 % to 20 %, calculated by heat value) on flue gas temperature and main flue gas components (O2, CO, NOx, etc.). The results indicate that as the boiler load decreases to 20 %, the average flue gas temperature inside the furnace drops by about 200 K, accompanied by widespread flame impingement on the water-cooled walls, leading to decreased combustion stability of the pulverized coal. Operating only the lower two layers of burners can achieve a higher average flue gas temperature (1540 K) and lower NO emissions (294 mg/m3). Furthermore, setting the horizontal swing angle of the burners to 15° can mitigate the impact of flames on the water-cooled walls and elevate the flame center, with the average flue gas temperature reaching 1559 K, making it the recommended burner swing angle setting. As the CH4 co-firing ratio increases from 0 % to 20 %, the average flue gas temperature rises by 50 K, and the emissions of NO and CO2 decrease by 15.3 % and 6.2 %, respectively, while H2O concentration increases by 21.3 %, potentially leading to low-temperature corrosion issues. The recommended CH4 co-firing ratio is 15 %.

Exploring NH3 combustion in environments with CO2 and H2O via reactive molecular dynamics

In existing power units such as internal combustion engines and gas turbines, the combustion of ammonia mixed with hydrocarbon fuels can effectively enhance the combustion intensity of ammonia. In the duel-fuel combustion scenario, the effect mechanism of the main components of combustion exhaust gas i.e., CO2 and H2O on ammonia combustion is still unclear and needs to be studied. Therefore, this paper uses reactive molecular dynamics simulations to study the combustion and emission processes of ammonia in environments with CO2 and H2O. The effects of the diverse gas environments (N2/O2, O2/CO2, and O2/CO2/H2O environments), high CO2 levels, varying H2O proportions, and O2 concentrations on ammonia combustion and emission were systematically explored. It was found that ammonia consumption was accelerated in the O2/CO2/H2O environments compared to N2/O2 environments, resulting in more NH2, H2, and H2O production. The effect of high CO2 concentration on ammonia oxidation was mainly related to temperature. The simulations found that the high CO2 concentration inhibited ammonia consumption at T < 2800K while enhancing it at T ⩾ 2800K. In addition, the high CO2 concentration could inhibit NO production under stoichiometric conditions but promote the conversion of nitrogen-containing intermediates to NO with the oxidizing capacity of CO2 enhanced significantly under extremely high temperature conditions. It was found that the increasing content of H2O molecules in the environment promoted NO production and inhibited CO production under stoichiometric conditions. In addition, the reaction paths for the conversion of HNO and HNO2 molecules into NO molecules were significantly enhanced with increasing H2O concentration. The increase in oxygen concentration can promote OH radical production and NO formation at high temperatures.

IoT-Based Propane and Butane Pressure Measurement

Liquefied Potreleum Gas is a hydrocarbon containing two main gas components, propane, and butane, produced from oil and gas refineries Liquefied Potreleum Gas is a hydrocarbon containing two main gas components, propane, and butane, produced from oil and gas refineries. In this study, researchers will do the same thing in the IoT field but not in health monitoring but refer to Butane and Propane Gas Pressure Monitoring in LPG. Errors often occur when using an analog manometer (needle panel) when taking pressure measurements due to inaccurate measurements. There is a clear necessity for using digital manometers to ensure precise gas methane pressure measurement. The sensor receives data then the Arduino processes the data for conversion, the final results will be sent to the cloud using the esp8266 module and then forwarded to the smartphone as a monitoring user to see and also check gas conditions.

ReaxFF Molecular Dynamics Study on the Microscopic Mechanism for Kerogen Pyrolysis.

Kerogen is mainly composed of carbon, hydrogen, and oxygen, which are the main components of crude oil and gas. The pyrolysis of kerogen is an efficient method to generate clean energy. In the present work, the pyrolysis reaction process of three types of kerogen is simulated using ReaxFF molecular dynamics (MD) methods to study the microscopic mechanism and the distribution of products. The results indicated that the pyrolysis products of the three types of kerogen significantly depend on the molecular structures, temperature, and reaction time. As the temperature increases, the gaseous hydrocarbon and the light and heavy oil fractions decreased, where small molecular fragments polymerized to form new molecular fragments. For an isothermal temperature, with the reaction proceeding, some component polymerization of the pyrolyzed fragments occurred, resulting in the generation of new light oils and heavy oils. Moreover, quantum chemical analysis was employed to reveal the kerogen pyrolysis mechanism. First, the weak bonds such as C-O, C-N, and C-S structures were decomposed to generate large carbon and some heavy shale oil fragments. Second, the cycloalkanes and long-chain alkanes were decomposed to generate a large amount of light shale oil and gaseous hydrocarbons. Finally, the decomposition of C═C in the aromatic ring, the secondary decomposition of light and heavy shale oils, and the further decomposition of short-chain alkanes occurred. In addition, the production of hydrogen (H2) occurred at the late stage of the pyrolysis reaction. Hydrogen radicals were formed by the decomposition of C-H bonds and subsequently collided with each other, resulting in the formation of H2 molecules. The pyrolysis and chemical analysis of kerogen can clearly determine the type and content of hydrocarbon substances, providing scientific data for exploration, development, and utilization of shale gas and shale oil.

An ultrafast and highly sensitive fluorescent probe for the detection of HSO3− and its application in food samples and SO2 gas

SO2 is one of the main components of air pollution gas, its derivatives HSO3− and SO32− were considerable used as food additive because of their antiseptic and bacteriostatic effects. Excessive intake of HSO3− is harmful to human health, so it is extremely important to detect the content of HSO3− in food sample by effective method. In this work, a small molecular fluorescence probe TPE-O based on tetraphenylethene fluorophore was designed and synthesized. The probe showed ultrafast (< 3 s) and obvious colorimetric response to HSO3− with high selectivity and sensitivity (LOD = 210 nM). The possible Michael-type addition of HSO3− on the activated C = C bond blocked the π-conjugated system, thus lead to changes in fluorescence and absorption spectra. Probe TPE-O not only can detect the content of HSO3− in sugar and wine, but also can be loaded on agarose hydrogel to detect SO2 gas. Therefore, this work provided a powerful tool for the detection of HSO3− in food samples and SO2 gas.

An analysis of waste/biomass gasification producing hydrogen-rich syngas: A review

In the last few decades, the population growth level has increased exponentially so the waste disposal level has increased gradually. Wastes like biodegradable wastes, kitchen wastes, hotel wastes, and other agro wastes can be processed through bio methanation and composting technology but non-biodegradable materials like plastics, rubber, industrial sludge, and other wastes cannot be processed in simple ways or technologies. These wastes are critical to handle and need robust technology. Gasification and incinerators are a technology to utilize these waste materials and convert them into useful energy. However, the incinerator has a drawback of control over emissions generated by waste material combustion. Gasification is the best-suited technology which can convert the waste material into gaseous form and this gas provides heat to the prime movers to generate energy/power. Carbon monoxide, hydrogen, methane, carbon dioxide, oxygen, and nitrogen are the main components of synthetic gas (syngas), which has a low calorific value. Increased hydrogen and carbon monoxide concentrations improve this gas's calorific value. Different gasification methods like gasification using agent as steam, catalytic gasification, and gasification using different combination of fuels (waste-coal/biomass) are used to enrich the hydrogen content of the syngas. This paper reviewed the theory of waste-to-energy technologies, incineration technology, gasification technology, methods for increasing hydrogen in syngas, also different methods. This review discusses waste gasification disposal methods and hydrogen enrichment.

Steam gasification of tire char supported by catalysts based on biomass ashes

The aim of this work is to assess the feasibility of steam gasification of tire char and the impact of various biomass ashes (sunflower husk, beet pulp, beech chips and corn cobs) in the process. Samples of tire-char and char-catalysts (in the amounts of 5, 10 and 15 wt%) were subjected to gasification in isothermal conditions (800–1000 °C) at a pressure of 1 MPa, using the thermovolumetric method based on an analysis of the composition of the resulting gas. Changes in the formation rates of the main gas components (CO, H2, CO2 and CH4), maximum carbon conversion, half times conversion, yields and composition of gas components and H2/CO ratio were determined. Kinetic parameters (activation energy and pre-exponential factor) of the gasification reaction were calculated using the grain and random pore models. The correlations between the content of individual elements in ashes and parameters describing tire char gasification were assessed. The addition of a catalyst and increasing its loading improved the reactivity of the tire-char at up to 850 °C and had a significant but temperature-dependent impact on gas component yields. Performing catalytic tire char gasification under appropriate selected conditions (800–850 °C and 10/15 wt% of sunflower husk and beech chips ash as catalysts) may be an attractive way to efficiently obtain a hydrogen-rich gas.

Bituminous Coal Sorption Characteristics and Its Modeling of the Main Coal Seam Gas Component in the Huaibei Coalfield, China

Knowledge of the gas sorption and permeability characteristics of a coal provides an essential basis for the evaluation of coalbed methane reserves and their recoverability. Thus, the gas excess sorption capacities of the main gas component of coal seam gas (CSG) in bituminous coal samples derived from the Xutuan Coal Mine in the Huaibei Coalfield, in the Anhui Province of China, were measured using a volumetric method. The results showed that under the same equilibrium pressure, the order of excess sorption capacity was CO2 &gt; CH4 &gt; N2. Furthermore, the sorption capacity ratios of coal from the Xutuan Mine for CO2, CH4, and N2 were approximately 6.0:2.3:1. It was also demonstrated that the sorption capacity during depressurization was always larger than that of the adsorption process, which is indicative of desorption hysteresis. The behaviors of three adsorption models, Langmuir, BET, and D-R, all of which include two parameters, are considered in this paper. The different gas sorption measurement data were fitted by the three models. For the bituminous coal samples, the fits of the D-R equation of all three different gases are higher than 0.99, the fits of the Langmuir equation are higher than 0.985, while the fits of the BET equation for CH4 and N2 absorption are higher than 0.95. However, the fits of the BET equation for CO2 absorption are only about 0.5. Coal sorption has an apparent influence on coal permeability; the permeability of the same coal sample to N2, CH4, and CO2 gases was tested and analyzed. The result shows that the permeability of CO2 was found to be lower than that of other coal seam gas constituents, CH4 and N2, due to their different adsorption abilities.

Investigation of the Solubility of Methane and Ethane in Hybrid Sweetening Solutions of 2-Aminoethanol and 1-Methylpyrrolidin-2-one/Water

Hydrocarbons of natural gas are captured by the solvent in the gas-sweetening absorption process and added to losses in production. Therefore, knowledge of hydrocarbon solubilities in solvents is required to assess and overcome these losses. In this study, the solubility of the main components of natural gas, methane and ethane, in n-methyl-2-pyrrolidone and monoethanolamine-based solvents was determined at the temperature of 313.15 K and pressures up to 2.366 MPa. Mass fractions of 0.10, 0.20, and 0.30 amine in the solutions were used in measurements that were performed using a static-synthetic method. The experimental data were modeled using the Soave–Redlich–Kwong Equation of State. Experimental results showed that the replacement of the aqueous part of conventional monoethanolamine solvents with n-methyl-2-pyrrolidone increased the solubility of desirable components of natural gas which is a negative side effect. The addition of monoethanolamine to n-methyl-2-pyrrolidone outperformed the Purisol solvent in terms of carbon dioxide absorption and decreased hydrocarbon solubility.

Outgassing Characteristics of Ceramic Shell Material and Microchannel Plates of Third-Generation Low-Light-Level Image Intensifiers

Vacuum failure is a major cause of shortening the lifetime (especially storage lifetime) of low-light-level image intensifiers. In order to deeply understand the vacuum failure mechanism of image intensifiers, the gas releasing rates and compositions of ceramic shell material (95 alumina ceramic) and microchannel plates (MCPs) of third-generation low-light-level image intensifiers were measured with the static pressure-rising method and residual gas analysis by a quadrupole mass spectrometer. The experimental results show that the outgassing rate of the 95 alumina ceramic at 150 °C is about one order of magnitude higher than that at 23 °C, while the outgassing rate of the MCPs at 150 °C is only about half an order of magnitude higher than that at 23 °C, which is caused by a large number of microchannels in the MCPs. During the static accumulation of gas releasing, the outgassing rate of the 95 alumina ceramic first increases and then tend to stabilize at 23 °C, and it remains basically unchanged at 150 °C, while for the MCPs both the outgassing rates at these two temperatures increase gradually, and the outgassing rate at the higher temperature increased relatively slowly. The main gas components released from the 95 alumina ceramic and MCPs at 23 °C include H2O, H2, N2/CO and CO2. After the vacuum baking at 150 °C, the releasing ratio of H2O gas from the 95 alumina ceramic decreased greatly, and that of H2 gas increased dramatically, while the releasing ratio of H2O gas from the MCPs decreased just slightly, which indicates that the vacuum baking degassing for the MCPs is relatively difficult.

Influence of pressure and sunflower husks ash as catalyst on tire-char steam gasification

Catalytic gasification of low-reactive waste fuels, like tire-char, with the use of a different type of waste as a cheap and efficient catalyst seems to be an up-and-coming solution; however, requiring selecting appropriate process conditions. Therefore, this study aimed to assess the effect of various amounts (0, 5, 10, 15 wt%) of waste-based catalyst (sunflower husks ash, SHA) and pressure on tire-char gasification with steam. Feedstock and catalyst were characterised, then physically mixed, and the prepared samples were subjected to steam gasification. The gasification measurements were performed at 800, 850, 900 and 1000 °C and the pressures of 0.5 and 1 MPa, using the thermovolumetric method based on an analysis of the composition of the resulting gas (this research focused on the main gas components, i.e. CO and H2). The obtained results showed that the selected tire-char was characterised by a high calorific value; however, it contained a high content of carbon and catalytically inert ash, which may affect its reactivity. In turn, sunflower husk ash selected as catalyst consisted mainly of catalytically active compounds of alkali and alkaline earth metals (in particular K2O), while at the same time a low content of acid components that inhibit the process. The gasification measurements proved that the character of curves of formation rates of CO and H2 differed, indicating different formation mechanisms. Moreover, pressure and catalyst addition affected the gasification process, especially at low temperatures (∼800–850 °C). In this temperature range, an increase in pressure, catalyst addition, and increasing its loading improved the conversion reaction rate and maximum carbon conversion, as well as hydrogen yields. In turn, an increase in pressure and the addition of catalyst positively affected the yield of carbon monoxide in almost the entire range of analysed temperatures, whereas the effect of catalyst was not significant. Finally, the analysis of kinetic parameters of carbon conversion reaction during steam gasification showed that the addition of catalyst reduced both activation energy and pre-exponential factor (the most significant reduction was observed when using 5 wt% of SHA), while the increase in pressure had an inverse effect on these parameters. Nevertheless, the obtained results show that steam gasification of tire-char at low temperatures, the pressure of 1 MPa and in the presence of 15 wt% of SHA may be an attractive way to efficiently obtain gas rich in hydrogen — one of the most promising future fuels.

Investigation of gauze and medical bottle co-pyrolysis on the product formation, reactivity, and reaction pathway of char, liquid oil, and gas.

Effective in-site treatment of medical waste has become a weak link in hospitals. Pyrolysis technology is a treatment method for medical waste that can enable rapid disposal in hospital settings and relieve environmental pressure, while also producing high-value products and reducing disposal costs. In this work, the effects of feedstock ratio and temperature on product yield and components of gauze (GA) and medical bottles (MB) co-pyrolysis have been investigated. The higher yield of solid products was obtained by co-pyrolysis of GA and MB at 400 ℃. With the addition of MB and an increase in temperature for the co-pyrolysis of GA and MB in a similar ratio, the pyrolysis oil and gas yields gradually increased. According to GC–MS analysis, co-feeding 75% MB to GA improved the alcohol content from 33.21% to a maximum yield of 59.8% at a pyrolysis temperature of 700 ℃. The content of aliphatic hydrocarbon reached 38.68% when the pyrolysis temperature and MB addition ratio were 700 °C and 75%, respectively. The GC data shows that the main gas components of co-pyrolysis of GA/MB were CH4 and H2, while the pyrolysis of pure GA or MB resulted in CO or CO2. Additionally, the solid carbon products obtained have an excellent pore structure. This strategy can benefit medical waste control and resource utilization for the low-cost disposal of medical waste and the acquisition of high-value resource products.

Simultaneous carbon dioxide sequestration and nitrate removal by Chlorella vulgaris and Pseudomonas sp. consortium

Carbon dioxide and nitrogen oxides are the main components of fossil flue gas causing the most serious environmental problems. Developing a sustainable and green method to treat carbon dioxide and nitrogen oxides of flue gas is still challenging. Here, a co-cultured microalgae/bacteria system, Chlorella vulgaris and Pseudomonas sp., was developed for simultaneous sequestration of CO2 and removal of nitrogen oxides from flue gas, as well as producing valuable microalgae biomass. The co-cultured Chlorella vulgaris and Pseudomonas sp. showed the highest CO2 fixation and NO3−-N removal rate of 0.482 g L−1d−1 and 129.6 mg L−1d−1, the total chlorophyll accumulation rate of 65.6 mg L−1 at the initial volume ratio of Chlorella vulgaris and Pseudomonas sp. as 1:10. The NO3−-N removal rate can be increased to 183.5 mg L−1d−1 by continuous addition of 0.6 g L−1d−1 of glucose, which was 37% higher than that of co-culture system without the addition of glucose. Photosynthetic activity and carbonic anhydrase activity of Chlorella vulgaris were significantly increased when co-cultured with Pseudomonas sp. Excitation–emission matrix (EEM) fluorescence spectroscopy indicated that the humic acid-like substances released from Pseudomonas sp. could increase the growth of microalgae. This work provides an attractive way to simultaneously treatment of CO2 and NOX from flue gas to produce valuable microalgal biomass.

Pressure broadening in Raman spectra of CH4–N2, CH4–CO2, and CH4–C2H6 gas mixtures

Different molecular environments change the spectrum of a given gas sample involved in a mixture compared to the spectrum of a pure gas. It is necessary to account for this effect to improve the accuracy of the analysis of the natural gas composition by Raman spectroscopy. First, the change in the main components of natural gas (methane, nitrogen, carbon dioxide, and ethane) must be considered. This work is devoted to the mutual influence of CH4–N2, CH4–CO2, and CH4–C2H6 on their characteristic Raman bands in the range of 300–2500 cm−1. The half-width and asymmetry of the Q branches of N2, CO2, and C2H6 as a function of methane concentration were obtained in the range of 1–50 bar. The averaged broadening coefficients of the rotational-vibrational lines of the ν2 band of CH4 perturbed by N2, CO2, and C2H6 are measured. A high-sensitivity spectrometer with a resolution of 0.5 cm−1 based on spontaneous Raman scattering was used to obtain reliable results. The algorithm and all the necessary parameters for simulating the effect of various molecular environments on the Raman bands of the main components of natural gas are presented.

Using an artificial neural network model for natural gas compositions forecasting

The paper presents the results of natural gas composition forecasting obtained using the MLP model of artificial neural network. The training of MLP model was performed on the basis of 8760 real data describing the percentage shares of the five main components of natural gas in a selected town on the territory of Poland. The model includes calendar factors (month, day of month, day of week, hour of day) and weather factors (ambient temperature), which indirectly affect the composition of natural gas in a given point of the gas network and were selected after a detailed statistical analysis of the variability of the natural gas composition in time. Based on the value of the correlation coefficient for the test set and the MAPE forecast errors calculated on the basis of the actual and the forecast data, the best quality MLP 18-65-5 network was experimentally selected. Natural gas composition forecasts were made using this model for input data characterizing the next calendar year and the average MAPE forecast error = 3.356% was calculated. Risk analysis, in turn, was used to estimate the probability of obtaining a forecast with a MAPE error greater than the mean error.

Catalytic conversion of toluene by biochar modified with KMnO4

This study aims to investigate the effects of biomass species, modification treatment, experimental time and atmosphere on the catalytic conversion of toluene (tar model compound) by biochar from gasification of oak, wheat straw and Enteromorpha. The gas and liquid phase products are detected by GC and GC–MS, respectively. The physical and chemical characteristics of biochar samples are analyzed by SEM-EDS, BET, XRD and XPS. The results show that the catalytic activity of oak char modified by KMnO4 (Mn-OC) is higher than that of other biochar samples. The KMnO4 modification improves the pore structure, increases oxygen-containing groups and enhances the activity of oak char. The relatively high toluene conversion rate (53.96 %) and low carbon deposition rate (3.41 %) of Mn-OC indicates that KMnO4 is more suitable for the modification of oak char. H2 and aromatic hydrocarbons (especially biphenyl and their derivatives) are the main components of gas and liquid products, respectively. The proportion of H2 in the total volume of H2, CO, CH4 and CO2 of Mn-OC reaches 56.94 %. The addition of water vapor is helpful to the formation of oxygen-containing groups and the improvement of biochar surface structure. Thus, adding moderate water vapor is beneficial to promote the catalytic activity of biochar. The toluene conversion rate and the total volume fraction of four main gases decrease with the increase of experimental time. They reduce significantly when the experimental time is longer than 120 min, from 44.51 % (120 min) to 24.86 % (180 min), which might be due to the damage of pore structure and the consumption of oxygen-containing functional groups.

Efficient separation of methane, ethane and propane on mesoporous metal-organic frameworks

Adsorption and separation of light saturated hydrocarbons (methane, ethane and propane) as main components of natural gas on a series of isoreticular mesoporous metal–organic frameworks NIIC-20-G (G = ethyleneglycol, 1,2-propyleneglycol, 1,2-butyleneglycol, 1,2-pentylenglycol, glycerol) has been thoroughly investigated. An impact of the size and nature of the glycol moiety on fundamental parameters of the adsorption (gas uptakes, adsorption constants, enthalpy and entropy, adsorption selectivity factors) was revealed and rationalized. The highest gas uptakes at 1 bar and 298 K are 13.2 ml(STP)·g−1 for CH4, 55.0 ml(STP)·g−1 for C2H6 and 125.4 ml(STP)·g−1 for C3H8. The IAST adsorption selectivities at ambient conditions (298 K, 1:1 gas mixture) reach 24.2 for C2H6/CH4, 29.0 for C3H8/C2H6 and as high as 1110 for C3H8/CH4. A rare combination of high adsorption uptakes and superb adsorption selectivity values achieved for NIIC-20-G put those MOFs ahead of the most other materials for light saturated hydrocarbon adsorption and separation. Dynamic breakthrough gas separation experiments on NIIC-20-Pr fully confirm effective separation of lighter alkanes from the corresponding binary or ternary mixtures. The obtained methane productivities are 1182 ml(STP)·g−1 (52.8 mol·kg−1) for C2H6/CH4, and 4193 ml(STP)·g−1 (187.3 mol·kg−1) for C3H8/CH4 equimolar gas mixtures, which greatly surpass earlier published data. The ethane productivity for an equimolar C3H8/C2H6 gas mixture is 3009 ml(STP)·g−1 (134.4 mol·kg−1). The breakthrough separation experiments validate a remarkable performance of the studied MOFs in the practical separation of natural gas or other relevant mixtures of light alkanes to valuable individual components.