Increase In CO2 Content Research Articles

Glucose addition in natural forest soils has higher biological nitrogen fixation capacity than other types of soils

Land use changes soil microbial and chemical properties, but the mechanism of biological nitrogen fixation under different land use patterns is rarely reported, so we used four types of soil: Natural forest soil (NS), healthy banana soil (HS), diseased banana soil (DS) and paddy soil (PS). Treatments included the control (CK), addition of glucose (G), addition of glucose and ammonium nitrate (GN), addition of banana straw (BS), addition of banana straw and ammonium nitrate (BSN), addition of banana root (BR), and addition of banana root and ammonium nitrate (BRN). The study found that the change of soil utilization types, glucose addition increased carbon dioxide emissions (Compared with the control, increased by 963.11%, 508.39%, 794.77% and 511.34%, respectively) and enhanced the ability of soil microbial nitrogen fixation. Importantly, natural forest soil microorganisms have a higher biological nitrogen fixation capacity compared to other types of soils. Glucose addition caused the accumulation of ammonium nitrogen (Compared with the control, increased by 426.08%, 934.21%, 420% and 1065.95%, respectively), indicating that microorganisms had higher utilization efficiency of soluble carbon and enhanced the biological nitrogen fixation capacity, and nitrogen addition caused the accumulation of ammonium nitrogen, thereby weakening the biological nitrogen fixation capacity. At the same time, glucose significantly increased the Fimicutes phylum (83.73%, 66.38%, 67.18% and 70.36%) and lowered the level of other bacterial phylums, thereby reducing the bacterial network structure, and the stability of the soil environment has decreased. Forest analysis showed that CO2 was an important factor in predicting the bacterial community structure of different soil types, an increase in CO2 content can predict drastic changes in the bacterial community. Bacteria at the Fimicutes phylum level preferred glucose, which may also have a negative effect on bacteria at the level of other phylums.

Calculation of Porosity and CO2 Content in CO2-Bearing Gas Formations Based on Density and Neutron Logging Forward and Inverse Methods.

When the gas reservoir contains CO2, the logging response tends to be complex. When calculating porosity with neutron and density curves, the accuracy of porosity calculation is reduced due to the uncertainty of fluid parameters, which in turn affects the evaluation of CO2 content. It increases the uncertainty of reserve evaluation. In this paper, a forward modeling model of density logging is established based on the equivalent volume model, and the method of neutron logging is formed by putting forward the nonlinear formula of the reciprocal of the comprehensive deceleration length. The key parameters and their variation rules of neutron logging and density logging forward modeling under different temperature and pressure conditions are obtained by experimental means and Monte Carlo method, respectively. The variation law of the influence of different CO2 content on neutron logging and density logging curves is simulated. The research shows that with the increase of CO2 content, the neutron logging value of gas reservoir decreases, while the density logging value increases, and the greater the porosity of gas reservoir, the more obvious this change trend is. Compared with CH4, CO2 has a more significant impact on the excavation effect of neutron logging. On this basis, combined with the conductivity model of the study area, the porosity and CO2 content of CO2 bearing gas reservoir are solved by the least-square method. The practice shows that the relative error of porosity calculation is within ±4% and the error of CO2 content calculation is within ±10%, which proves the reliability of this method.

Flux-cored arc welding of 316L austenitic stainless steel: the effect of different shielding gas mixtures on microstructural features and weld performance

ABSTRACT Double-pass flux cored arc welding (FCAW) of 316 L austenitic stainless steel was performed using different shielding gas mixtures. Microstructural features and weld performance were evaluated. Based on the Creq/Nieq ratio of fusion zone and cooling rate, different morphologies of ferrite (skeletal, lathy, and dendritic) and austenite with various volume fractions were produced. An increase in Creq/Nieq ratio can increase the strength level because the presence of ferrite in the weld metal acts as a second-phase strengthening agent. On the other hand, ferrite is a suitable place for sigma phase precipitation. Highest joint efficiency resulted in the specimen welded via GTAW. The ductility of welds was ranked as CO2 +Ar shielded FCAW > GTAW > CO2 shielded FCAW > self-shielded FCAW. At room temperature, variation of delta-ferrite content (Creq/Nieq ratio) does not affect toughness. However, an increased amount of CO2 in shielding gas will result in decreased toughness values because of the enhanced formation of oxide inclusions. Increasing CO2 content of shielding gas from 0% to 18% and finally to 100% will result in decreasing toughness values from the highest value of 76J to 40 J and finally the lowest value of 38J.

Atomic-Scale Insights into the Effects of the Foaming Degree on the Glass-Ceramic Matrix Derived from Waste Glass and Incineration Bottom Ash.

Precise management of the inverse correlation between the total porosity and compressive strength is crucial for the progress of foaming glass-ceramics (FGCs). To deeply understand this relationship, we investigated the atomic-level transformations of five CO2-foaming FGC samples using molecular dynamics simulation. The short-range and intermediate-range structures of the FGCs with varying total porosities (36.68%, 66.28%, 66.96%, 72.21%, and 79.88%) in the system were elucidated. Na cations were observed to exhibit a strong interaction with CO2, accumulating at the surface of the pore wall and influencing the oxygen species. Therefore, the change in the atomic structure of the matrix was accompanied by an increase in the total porosity with an increasing CO2 content. Specifically, as the total porosity increased, the bridging oxygen content within the FGCs rose accordingly. However, once the total porosity exceeded 66.96%, the bridging oxygen content began to decline. This observation was significant considering the role of the bridging oxygen content in forming a continuous cross-linked network of chemical bonds, which contributed to the enhanced mechanical strength. Consequently, the influence of the total porosity on the oxygen species resulted in a two-stage reduction in the compressive strength. This study offers valuable insights for the development of high-strength lightweight FGCs.

CO2 effect on the fatigue crack growth of X80 pipeline steel in hydrogen-enriched natural gas: Experiment vs DFT

Utilizing the existing natural gas grid presents a promising method for transporting hydrogen on a large scale. However, the effects of natural gas and its impurities on hydrogen-assisted cracking in pipeline steel have not been adequately studied. This study aims to investigate the fatigue performance of X80 pipeline steel in hydrogen-enriched natural gas (HENG) environments and in mixtures containing the impurity CO2. This is achieved through fatigue crack growth rate (FCGR) tests and density functional theory (DFT) calculations. The experimental results show that the FCGR in H2 is slightly faster than that in HENG, whereas it is slower than that in the N2/CO2/H2 mixtures. The enhanced FCGR by CO2 further increases with the increasing CO2 content. DFT computational results indicate that the adsorbed CO2 on the iron surface significantly accelerates the migration of H atoms from surface to subsurface. This promotes the entry of hydrogen into the steel.

Investigating arc and molten metal transport phenomena in gas metal arc welding with Ar–CO2 gas mixtures using a numerical method

This paper presents a numerical investigation of the transient transport phenomena of the arc and molten metal during gas metal arc welding (GMAW) using shielding gas mixtures ranging from 100% Ar + 0% CO2 to 80% Ar + 20% CO2. The thermophysical parameters of the Ar–CO2 mixtures, considering the presence of metal vapor, were calculated as a function for a temperature range of 1000–30 000 K. The influence of metal vapor content and CO2 proportion on the thermophysical properties of the mixed gas was discussed in detail. As the CO2 content increased from 0 to 20%, the shape of the arc changed from a bell to a cone due to the increase in mass density, specific heat, and thermal conductivity. The maximum arc temperature and velocity decreased with increasing CO2 content, resulting in larger droplets and a lower droplet transfer frequency. Although the change in electrical conductivity did not affect the arc shape, it did influence the arc temperature by altering the distribution of current density. Experiments of droplet transfer and arc behavior were carried out, and the results showed that the simulated droplet size, transfer frequency, and arc temperature distribution agreed well with the experimental values. These findings could serve as a theoretical tool for better understanding the underlying physical mechanisms of the GMAW process using different shielding gases, ultimately aiming to achieve high weld quality.

Part 2: aspects of the relation between photosynthesis and crop productivity

ABSTRACT Photosynthesis is amongst the basic physiological processes, affecting plants productivity. There can be different means to increase productivity, and most of them involve increase of photosynthetic activity. Photosynthesis can be influenced by many stressors, which exert different effects, but they have in common a negative impact on productivity. Moreover, the alleviation of stress by plants correspondingly decreases productivity. Thus, the summarised effects of stress were only generally mentioned in this article, and the process of photorespiration was underlined. Photorespiratory pathway relates photosynthesis and productivity, and can also protect plants from oxidative stress at the expense of carboxylation. In addition, alterations of the photorespiration can disrupt the balance between carbon and nitrogen in the biomass of plant. Being a common metabolic pathway between the photosynthesis and many assimilatory metabolic pathways, such as the biosynthesis of proteins and assimilaiton of nitrogen and sulphur, photorespiration binds the photosynthesis to productivity. One very important topic, especially under the global increase of CO2 content in the atmosphere is the relation between carbohydrates and protein biosynthesis. It affects differently the C3 and C4 species, thus photosynthetic specifics of these plants were reviewed as well. C4 are often considered more competitive and productive, as compared with other plants and therefore are preferred as innovative crops under the future climatic conditions.

Carbon dioxide capture using diaminoalkane-grafted MIL-101(Cr)s: Critical role of geometric configuration of loaded amines

Preventing the increase of CO2 content in the atmosphere is crucial to mitigating climate change. In this study, we investigated the adsorption of CO2 using isostructural Cr-based MOFs, MIL-101 and MIL-100, after grafting diaminoalkanes with various chain lengths to determine the effect of the geometric configuration of the amines and to develop a competitive adsorbent. The performance of CO2 adsorption (e.g., adsorption capacity, selectivity, and adsorption heat) over MIL-101 increased as the size of diaminoalkanes increased, topped with 1,4-butanediamine, and declined with longer diaminoalkanes. The favorable contribution of grafted 1,4-butanediamine in increasing the performances in CO2 adsorption could be explained by the adequate size of the amines for the optimized configuration in the pore window of the MIL-101. However, interestingly, none of the MIL-100s grafted with diaminoalkanes showed a similar positive effect probably because of the smaller pore window of MIL-100 than that of MIL-101. To the best of our knowledge, this is the first study to demonstrate the importance of geometric configuration (or, the chain length of amines) in amine-grafted MOFs for the CO2 adsorption that follows the general mechanism that requires interactions between two uncoordinated amines for the formation of ammonium carbamates. Moreover, one of the modified MIL-101 grafted with 1,4-butanediamine exhibited remarkable performance in CO2 adsorption with 4.0 times the adsorption capacity of CO2 at 15 kPa and 20.6 times CO2/N2 selectivity (based on ideal adsorbed solution theory, at 100 kPa) compared to the virgin MIL-101.

Application of ultrafine bubbles for enhanced carbonation of municipal solid waste incineration ash during direct aqueous carbonation

Municipal solid waste incineration fly ash was selected as the alkaline Ca-bearing solid waste, and a series of direct aqueous carbonation experiments using 10% CO2 gas were conducted to showcase the capability of ultrafine bubbles (UFBs) in enhancing carbonation efficiency. Results from the experiments, conducted using a one-pass water flow system, revealed that carbonation without UFBs increased the CO2 content of the ash from 59 to 200 mgCO2/g (an increase of 141 mgCO2/g), while the presence of UFBs elevated it to 237 mgCO2/g (an increase of 178 mgCO2/g). Consequently, the introduction of UFBs led to a 26% increase in CO2 content in ash [(178−141) / 141]. This improvement was primarily attributed to the enhanced carbonation efficiency for particles ≥ 46 µm. The positive impact of UFBs was more evident (62% increase in CO2 content in ash) in experiments using a water circulation system, where carbonation proceeded at a faster rate compared to the one-pass water flow system. In terms of the mechanism, X-ray diffraction and scanning electron microscopy analyses indicated that UFBs facilitated the removal of CaCO3 deposition, which inhibited Ca(OH)2 dissolution. To the best of our knowledge, this study is the first to demonstrate the favorable influence of UFBs on fly ash carbonation efficiency.

Two Ln-MOFs containing abundant Lewis acid sites as the efficient and heterogeneous catalyst to activate epoxides for cycloaddition of CO2

The burning of a large number of fossil fuels leads to the increase of CO2 content in the air, causing environmental problems such as greenhouse effect and ocean acidification, which has attracted wide attention. It is of great significance to utilize microporous metal-organic frameworks (MOFs) for carbon dioxide conversion and utilization. Herein, two MOFs {[Ln(dppa)(H2O)2·2H2O]·dima·H2O·0.5O} (1: Sm-MOF; 2: Gd-MOF; H4dppa = 5-(3′ 4′-dicar- boxylphenoxy) isophthalic acid, dima = dimethylamine, which is decomposed by DMF hydrothermal reaction), and its structural characterization and CO2 catalytic conversion performance were studied. The BET test of MOFs 1–2 shows that it has good microporosity. At 273 K and 298 K, MOFs 1–2 showed lower adsorption capacity for CH4, but higher adsorption capacity for CO2. The adsorption enthalpy of CO2 was calculated by Virial equation, and the adsorption selectivity of CO2 at different separation ratios was discussed respectively. The heterogeneity of MOFs 1–2 was proved by thermal filtration experiments. The reproducibility test shows that the catalyst structure is still intact after five cycles, indicating that the catalyst still has good repeatability. In addition, the catalytic mechanism of cycloaddition reaction was discussed.

Estimation of Carbon Stocks of Birch Forests on Abandoned Arable Lands in the Cis-Ural Using Unmanned Aerial Vehicle-Mounted LiDAR Camera

Currently, studies investigating the carbon balance in forest ecosystems are particularly relevant due to the global increase in CO2 content in the atmosphere. Due to natural reforestation over the past 25–30 years, birch (Betula pendula Roth.) forests were extensively grown and established on abandoned agricultural lands in Bashkir Cis-Ural (Republic of Bashkortostan, Russia). The significant positive aspect of reforestation on fallow lands is the carbon sequestration that takes place in the tree phytomass, especially at the growth stage of stand formation. The aim of this article is to test the approach of using a UAV-mounted LiDAR camera to estimate the phytomass and carbon stocks in different-aged birch forests growing on abandoned arable lands in Bashkir Cis-Ural. The methodology was developed using 28 sample plots, where the LiDAR survey was performed using a DJI Matrice 300 RTK UAV. Simultaneously, the stand characteristics and phytomass of stem wood were also estimated, using traditional methods in the field of forest science. The regression equations of phytomass dependence on stand characteristics at different stages of reforestation were constructed using data obtained from LiDAR imagery. It was shown that the above-ground tree biomass could be precisely estimated using the index obtained by multiplying the number of trees and their average height. A comparison of the data obtained using traditional and LiDAR survey methods found that the accuracy of the latter increased in conjunction with stand density. The accuracy of estimation ranged from 0.2 to 6.8% in birch forests aged 20 years and over. To calculate carbon stocks of the above-ground tree stands, the use of regional conversion coefficients is suggested, which could also be applied for the estimation of carbon content in trunk wood and leaves. An equation for the calculation of above-ground biomass carbon stocks of birch forests on abandoned arable lands is proposed.

Investigating the Impact of an Exsolved H2O‐CO2 Phase on Magma Chamber Growth and Longevity: A Thermomechanical Model

AbstractMagmatic volatiles drive pressure, temperature, and compositional changes in upper crustal magma chambers and alter the physical properties of stored magmas. Previous studies suggest that magmatic H2O content influences the growth and longevity of silicic chambers through regulating the size and frequency of eruptions and impacting the crystallinity‐temperature curve. However, there has been comparatively little exploration of how CO2 impacts the evolution of magma chambers despite the strong influence of CO2 on H2O solubility and the high concentrations of CO2 often present in mafic systems. In this study, we integrate the thermodynamic effects of dissolved and exsolved H2O and CO2 with the mechanics of open‐system magma chambers that interact thermally and mechanically with the crust. We applied this model to investigate how intrinsic variations in magmatic H2O‐CO2 content influence the growth and longevity of silicic and mafic magma chambers. Our findings indicate that even with a tenfold increase in CO2 content (up to 10,000 ppm), CO2 plays a minimal role in long‐term chamber growth and longevity. While CO2 content affects the magma compressibility, the resulting changes in eruption mass are balanced out by a commensurate change in eruption frequency so that the time‐averaged eruptive flux and long‐term chamber behavior remain similar. In contrast, H2O content strongly influences chamber growth and longevity. In silicic systems, high H2O contents hinder magma chamber growth by increasing the total eruptive flux and steepening the slope of the crystallinity‐temperature curve. In mafic systems, high H2O contents promote magma chamber growth by flattening the slope of the crystallinity‐temperature curve.

Study on combustion characteristics of fully premixed water-cooled biogas burner

Biogas is a renewable gas produced by the fermentation of biomass and is an environmentally friendly alternative to traditional fossil fuels. To overcome the problems of traditional biogas burner, such as unstable combustion, easy flameout and backfire, and low thermal intensity, a new water-cooled biogas burner based on fully premixed combustion technology was designed and developed. Then, numerical simulations and experimental investigations were conducted to explore the effects of CO2 content, excess air coefficient, heat load, and cooling water temperature on the combustion characteristics of the burner. The results revealed that the designed burner exhibited good adaptability to simulated biogas with methane concentrations ranging from 55 % to 80 %. Increasing CO2 content resulted in decreased combustion temperatures and reduced NOx and CO emissions concentration at the burner outlet. In addition, reducing the excess air coefficient enhanced the combustion heat intensity and reduced combustion heat loss. Nevertheless, excessively low excess air coefficients yielded elevated levels of NOx and CO in the flue gas. The results showed that the designed burner demonstrated stable operation at a minimum heat load of 35 %, exhibited a favorable load regulation ratio, and had low emissions. It is a promising solution for utilizing biogas as a clean and sustainable energy source.

A novel approach to optimize weld formation and regulate interfacial microstructure in TC4/304SS dissimilar arc welding by active hybrid shielding gas

CO2 shielding gas was innovatively employed for TC4/304SS dissimilar metal arc welding, overcoming the limitation of active gas application for Ti welding. The effect of CO2 addition on welding process was investigated. Our results show that the CO2+Ar hybrid shielding gas eliminated the problem of insufficient bonding at the backside of the steel plate, and was helpful to obtain a full weld joint. Moreover, the microstructure of the weld joint was modified due to the intense mass transfer inside the molten pool. The typical Ti/Cu interface was divided into two layers. No Ti–Fe compounds were found within the Ti/Cu interface for pure Ar shielding gas. However, the interface morphology was found to change due to induced CO2. Some TiFe2+Ti5Si3 dendrites were formed in layer Ⅱ. And the TEM results showed that the addition of CO2 did not contribute to the generation of a new phase, but the island-shaped Ti2Cu3 was transformed to a lath shape. In the weld seam center, Ti–Fe–Si ternary compounds was formed instead of Ti–Fe or Ti–Cu compounds. The hardness of the entire joint increased with increasing CO2 content. An average strength of 480 MPa was obtained for 3% CO2 content, which is an increase of 57.9% compared to that for pure Ar shielding condition. The fracture surface morphology showed small cleavage flatforms with some shallow dimples. Better weld formation and the optimization of the interface microstructure both contributed significantly to the improvement of the tensile strength of the Ti/steel joint.

Effect of polarities and shielding gases in CWW GMAW

ABSTRACTThe effect of polarity and shielding gases on the droplet transfer behavior and formation trend of cable-type welding wire gas metal arc welding was studied under the same welding parameters. An acquisition system was used to observe welding parameters, droplet transfer and arc behavior. The results showed that the arc shapes with different polarities under the same shielding gas were different. The arc length and width in direct current electrode positive (DCEP) mode were smaller than those in direct current electrode negative (DCEN) mode. For the same polarity and different shielding gases, with increasing CO2 gas content, the arc length and width gradually decreased. In DCEP mode, droplet transfer was characterized by globular and projected droplet transfer modes. The droplet transfer modes with different polarities differed under different shielding gases. The droplet transfer mode was basically the same for the same polarity. With increasing CO2 content, the weld bead formation gradually improved.

Comparison of СO<sub>2</sub> Content in the Atmosphere of St. Petersburg According to Numerical Modelling and Observations

Due to the increase in CO2 content in the Earth’s atmosphere, which is highly dependent on anthropogenic emissions of CO2, quality of emission estimation should be improved. Advanced experiment-based methods of the CO2 anthropogenic emission estimation are built on solution of an inverse problem using highly-accurate measurements of CO2 content and numerical models of transport and chemistry in the atmosphere. The accuracy of such models greatly determines errors of the emission estimations. In a current study temporal variations of column-average CO2 content in an atmospheric layer from surface to the height of ~70–75 km (XCO2) in the Russian megapolis of St. Petersburg during Jan 2019–Mar 2020 simulated by WRF-Chem model and measured by IR Fourier-transform spectrometer Bruker EM27/SUN are compared. The research has demonstrated that the WRF-Chem model simulates well the observed temporal variation of XCO2 in the area of St. Petersburg (correlation coefficient of ~0.95). However, using CarbonTracker v2022-1 data as chemical boundary conditions, the model overestimates XCO2 relative to the observations significantly during almost the whole period of investigation – systematic difference and standard deviation of the difference are 4.2 and 1.9 ppm (1 and 0.5%). A correction of the chemical boundary conditions which is based on analysis of a relation between near-surface wind direction and XCO2 variation notably decreases the systematic difference between the modelled and observed data (almost by a factor of 2). The XCO2 variation by the observations and modelling with uncorrected chemical boundary conditions are in a better agreement during vegetation season. Probably this is related to the compensation of the systematic difference by inaccuracies in estimated biogenic contribution. Hence, the reason of the still existing mean difference between the modelled and observed data can be inaccuracies in setting chemical boundary conditions for upper troposphere and in estimating how biosphere influences CO2 content.

Effect of shock wave on nucleation and droplet growth of CO2 in flue gas in supersonic separators

To reduce carbon emissions caused by fossil fuel combustion, this work evaluates a potential carbon capture method. Based on heat transfer theory, aerodynamics and condensation dynamics, a mathematical model is proposed to depict the nonequilibrium condensation of CO2 in flue gas (N2–CO2). The interaction between shock wave and non-equilibrium condensation is clarified. The results show that when the shock wave enters nucleation area, the nucleation process is rapidly terminated and droplet growth process disappears. After the shock wave, the supersaturation decreases rapidly from 2.26 to 0.19, the gas changes from supersaturated state to unsaturated state, and the system returns to the thermodynamic equilibrium state. When the shock wave appears in the droplet growth area, there is a complete nucleation process. The gas molecules in front of the shock wave form stable droplets and release latent heat, leading to the fluctuation of temperature and pressure. After the shock wave, the droplet growth environment is destroyed, resulting in droplet radius and liquid content drop to 0. Increasing CO2 content can not only reduce the impact of shock wave on flows, but also strengthen the heat and mass transfer, and obtain larger droplet radius and higher liquid content.

ПРІОРИТЕТИ У ВИКОРИСТАННІ ВИКОПНИХ ВИДІВ ПАЛИВА ТА УТРИМАННІ ЖИТЛОВОГО ФОНДУ

The trends of global temperature increase in the world due to excessive burning of fossil hydrocarbons are given. Excessive extraction and burning of fossil fuels (hard coal, petroleum products, natural gas) have led to an increase in their cost and climate change. About 40% of CO2 emissions today come from burning coal, 33% from oil refining products, and 22% from natural gas. An increase in CO2 content in the atmosphere leads to a drop in the Earth's surface temperature. At the global level, the world community has adopted three main international agreements on climate change: the UN Framework Convention on Climate Change (1992); Kyoto Protocol (1997); Paris Agreement (2015). More than 190 countries have signed the Paris Agreement. Its main goals are to achieve carbon neutrality by 2050 and to keep the increase in the global average temperature below 2°C by 2100, preferably to 1.5°C.
 The construction industry is responsible for consumption of up to 40% of all energy. which are used in economies countries of the world In the summarized reports of experts at the 27th UN Conference on Climate Change (COP27), which took place in 2022 year in Egypt (Sharm el-Sheikh) it was stated that in 2022 1% more CO2 will be released into the atmosphere than in in 2021. The main volumes of greenhouse gas emissions come from the burning of fossil fuels. Brought comparative analysis of CO2 emissions when burning different types of fuel.
 The dynamics of the production of fossil fuels - hard coal, oil and natural gas - is studied, which indicates a significant decrease in their production and consumption. Modern approaches to the growth of RES volumes are considered, the dynamics of the growth of SPP capacities are given. On the basis of European experience, the prospects for the installation of balcony mini SPPs are shown.
 Individual heating systems and decentralization of engineering systems for providing housing help to increase their stability in adverse conditions. The organizational features of the transfer of the housing stock from a centralized heating system to individual electric and gas heating are revealed. Based on the analysis of the European experience of maintaining the housing stock, the main directions for reducing energy consumption and greenhouse gas emissions of the existing housing stock are given.

Exploration on laminar flame propagation of biogas and DME mixtures up to 10 atm: Insight into effects of DME co-firing, CO2 addition and pressure

Biogas (BG) is an important renewable fuel from biomass feedstock with methane and carbon dioxide (CO2) as the main components. Its low fuel reactivity and flame stability caused by the considerable CO2 content raises the research need for the enhancement of its combustion. In this work, the laminar flame propagation of BG and DME mixtures was investigated with special attentions on the effects of DME co-firing, CO2 addition and pressure. The laminar burning velocities of BG/DME/air mixtures were measured at 298 K, varying initial pressures (1–10 atm), DME contents in fuel mixtures (0–1), CO2 contents in BG (0–0.4), and equivalence ratios (0.7–1.4). It was concluded that the laminar burning velocity can be effectively improved with the increasing DME content, moderately reduced with the increasing CO2 content, and dramatically reduced at elevated pressures. Meanwhile, a kinetic model of BG/DME combustion was developed and validated against the experimental data in both this work and literature. The modeling analysis shows that the enhanced flame propagation with DME co-firing is associated with the increased concentrations of key radicals like H, O, and OH due to the increased adiabatic flame temperatures and the enhanced DME-related pathways. On the other hand, the inhibited flame propagation with CO2 addition is associated with the decreased concentrations of key radicals. The fictitious diluent gas method was used to separate the different effects of DME co-firing and CO2 addition. The thermal effects play a more important role than the chemical effects in the increased laminar burning velocity with the DME co-firing, while the contributions to the decreased laminar burning velocities with the CO2 addition obey the order of thermal effects > chemical effects > dilution effects. Moreover, the pressure effects in the laminar flame propagation of BG/DME mixtures reduce with the increasing DME content, but remain nearly unchanged with the increasing CO2 content. This is mainly because the DME co-firing can reduce the significance of the most important chain-termination pathway, i.e., CH4 (+M) = CH3 + H (+M), while the CO2 addition does not have adequate influence.

Environmental Monitoring—Important for Climate Protection Policy and Measures

During the past months, we have received more and more submissions on the topic of monitoring in the field of environment in the journal CLEAN – Soil, Air, Water. So far, monitoring articles have not been in scope for CLEAN. The increasing desire of scientists to publish articles with monitoring background in CLEAN has shown me as the Editor-in-Chief that environmental scientists very much see this kind of contribution in the journal. And I have to admit, they are right. With an increasing urgency regarding climate or climate change issues, we really need evidence of the changes in the parameters. If we cannot prove with data what the quality of air, water, and soils is, we lack the basis for taking action for clean air, pure water, and good soil quality—and thus also for the health of all of us. The discussion about climate change and its effects has long since reached the public. We not only read about it in scientific articles, but also learn in all the media available to us that we will not be able to reach the climate targets. Due to the hunger for energy, which is often satisfied by burning oil, gas or coal, the parameters for air quality, such as an increase in CO2 content, nitrogen oxides, methane, etc., have changed extremely in recent years. Another example would be the agricultural sector, where climate change is affecting soils, with droughts or heavy rainfall events. And there are so many more examples that could be mentioned here. As far as clean air is concerned, scientists worldwide have collected and published interesting results during lockdowns with restricted mobility in the COVID-19 pandemic. If mobility is restricted by government regulations, this has a massive effect on air quality—it improves considerably. But as soon as restrictions are lifted, we behave as usual. People are traveling by car and flight bookings are back to pre-pandemic levels. The values of water and soil pollution parameters are also alarming. More and more chemicals are found in soils and then later in water, or vice versa, first in water and then in soils—and later in the food on our plates. Microplastic particles can now be detected everywhere, in water, in soil, in food and in our bodies. Everything is connected to everything else. And so, monitoring of air, water, and soil quality parameters is more important than ever. I therefore welcome submissions on monitoring of water, air, and soil quality parameters in CLEAN. The following criteria apply to submissions that include monitoring data: Manuscripts containing only measured data are not sufficient for publication. The collected data should be compared and discussed with published works and the resulting findings should be placed in a scientific context. Let's add this new subject “Monitoring of Quality Parameters” to the journal. Stay healthy! Yours sincerely