Adding Carbon Dioxide Research Articles

Model for estimating the effects of pressure and dilution on the flammability limits of fuels in constant-volume systems at subatmospheric pressure

The fire and explosion hazard of a fuel is closely related to its flammability limits. These limits are affected by pressure but are typically investigated at atmospheric pressure. However, fuel in aircraft tanks during flight is at subatmospheric pressure, and most industrial processes are often conducted at nonatmospheric pressure. Inert gases are often added to mixtures to mitigate the flammability risks associated with oxidation and fuel storage processes; however, predicting the behavior of such mixtures is challenging. Building on two prior models, this study established a comprehensive model based on reported heat capacities to estimate flammability limits in fuel–air–diluent mixtures at various initial pressures. The accuracy of the model was validated through comparison with measured flammability limits for propylene with added nitrogen or added carbon dioxide at subatmospheric pressures. The predictions closely aligned with the measurements, with the deviations of lower and upper flammability limits (ΔL and ΔU, respectively) being 0.01% – 0.29% and 0.09% – 0.30%, respectively, for nitrogen addition and 0.10% – 0.23% and 0.36% – 0.89%, respectively, for carbon dioxide addition; these results confirmed the model’s efficacy. In summary, the proposed model could be applied to reduce flammability risk in systems containing air and fuel at any pressure, regardless of the addition of inert gases.

Activation of carbon dioxide on zinc oxide surfaces doped with cerium

AbstractThe adsorption of carbon dioxide on the surfaces of zinc oxide doped with cerium was studied. For this, a theoretical study was carried out using computational simulations based on density functional theory to determine possible improvements in photocatalytic activity. for the capture and dissociation of carbon dioxide. Calculations were performed using density functional theory within the Perdew-Burke-Ernzerhof generalized gradient approximation, also the Hubbard correction together with ultrasmooth atomic pseudopotentials and a basic plane wave implemented in the Quantum-ESPRESSO package. The doping concentration level considered in this work was 6.25%, among the results, the semiconducting character of zinc oxide was evident from the density of states calculations, it was also found that by adding cerium impurities to zinc oxide, the values of the lengths and angles of the bonds vary a little, this may be due to the small difference in covalent radius that the zinc atom has with respect to the cerium atom, consequently, changes occurred in the electronic properties that consist in intermediate states in the energy bandgap located around the Fermi energy. This may suggest that the cerium-doped zinc oxide system can probably absorb visible light, which could lead to possible improvements in the photocatalytic properties of the material. Furthermore, we found that by adding carbon dioxide to the cerium-doped zinc oxide surface, the carbon dioxide is activated and this could suggest the dissociation or reduction of this contaminant.

Исследование параметров горения жидкого углеводородного топлива при его распылении перегретым водяным паром, углекислым газом и их смесью

Reducing the anthropogenic impact on the environment is one of the priority tasks of our time. One of the sources of pollution is the burial of a large amount of substandard combustible waste, including hydrocarbon waste, which is not currently in demand, as well as solid and toxic substances generated during combustion. The solution to the identified problems is possible through the Waste-to-Energy approach, aimed at involving combustible waste in the fuel balance, with the organization of low-temperature combustion by adding various diluent gases - carbon dioxide or water vapor. In this work, using diesel fuel as an example, the combustion characteristics of liquid hydrocarbons in the presence of a mixture of superheated steam and carbon dioxide in a spray burner were experimentally obtained and compared to identify the features and advantages of their use in Waste-to-Energy approaches. It is shown that for all studied modes a high completeness of fuel combustion is observed. Analysis of the composition of combustion pro¬ducts shows that when replacing superheated steam with carbon dioxide, the content of CO and NOx in combustion products increases by 25%. At the same time, all studied modes comply with the EN:267 standard. The results show that it is possible to implement approaches of adding carbon dioxide, water vapor and a mixture of both to convert waste into energy.

Badanie skuteczności nowego inhibitora w różnych środowiskach o dużej aktywności chemicznej

"The corrosion protection effect of the new S-1 reagent in media with the pH values of 2.0, 4.0, 6.0, as well as carbon dioxide and hydrogen sulfide added separately and combined to the mentioned media, was first tested under laboratory conditions. The protective effect of reagent S-1 was weak in the corrosion medium without hydrogen sulfide and carbon dioxide. However, as the acidity of the medium and the concentration of the reagent increases, the corrosion protection efficiency of the inhibitor also increases. The highest effect is observed at pH = 2.0 and reagent concentration of 30 mg/l. The corrosion protection effect of the reagent reaches 97% under these conditions. In the media with pH = 4.0 and pH = 6.0 without carbon dioxide and hydrogen sulfide, the protective effect of the inhibitor at the optimal concentration of 30 mg/l is 66% and 64%, respectively. In the medium with added carbon dioxide, the protective effect of inhibitor S-1 decreases at pH = 2.0 and, on the contrary, increases at the values of pH = 4.0 and pH = 6.0. Also, as the pressure of carbon dioxide in the medium increases, the protective effect of inhibitor S-1 increases. When hydrogen sulfide is added to the medium, it causes an increase in the corrosion rate and the protection efficiency of inhibitor S-1. However, in the medium without inhibitor, the increase of hydrogen sulfide concentration only up to CH2S = 400 mg/l is accompanied by an increase in the corrosion rate at all values of pH. The addition of 1000 mg/l of hydrogen sulfide to the corrosion medium leads to the decrease in the corrosion rate in the medium without inhibitors and a slight decrease in the protective effect at the concentration of the inhibitor Cinh = 10 mg/l. As the concentration of inhibitor S-1 increases in the medium with the addition of carbon dioxide and hydrogen, its corrosion protection effect also increases. In the range of Cinh = 10–30 mg/l, when PCO2 = 0.5 atm and CH2S = 200 mg/l, the protective effect is estimated at 38–99%, and when CH2S = 1000 mg/l, it is estimated at 17–79%. At PCO2 = 1.0 atm, the value of protective effect is 22–95% and 14–76%, and finally at PCO2 = 2.0 atm, the value of the corrosion protection effect of inhibitor S-1 is estimated at 44–92% and 15–75%, respectively. The coexistence of carbon dioxide and hydrogen sulfide in an aggressive medium leads to an increase in the protective effect of inhibitor S-1 compared to the medium containing only carbon dioxide, and reduces it in comparison to the medium with hydrogen sulfide. An increase in carbon dioxide pressure in the presence of hydrogen sulfide causes a decrease in the protective effect of inhibitor S-1. The protective effect of inhibitor S-1 is lower in the medium with hydrogen sulfide concentration of 1000 mg/l compared to a concentration of 200 mg/l. This case is also observed in the carbon dioxide free medium."

How Environmental Regulation, Digital Development and Technological Innovation Affect China’s Green Economy Performance: Evidence from Dynamic Thresholds and System GMM Panel Data Approaches

Based on the background of China’s “carbon neutral” policy and the booming digitalization, how does environmental regulation affect green economy performance? The existing literature has studied the impact of energy consumption on green economic performance. However, the literature has ignored the impact of carbon dioxide emissions on China’s green economy performance. In this regard, this research uses the non-radial distance function (NDDF) to calculate the green economic performance of China’s prefecture-level cities, and uses the dynamic panel threshold model and the systematic GMM method to study the nonlinear impacts and mechanisms of environmental regulation, digital development, technological innovation, and industrial structure upgrade on green economic performance. The panel data set contains 228 Chinese cities from 2003 to 2019. The following findings are established: first, after adding carbon dioxide emissions to China’s green economy performance, the environmental performance was reduced, and the green economy performance was also reduced. Second, the impact of environmental regulations on green economic performance has a double-threshold effect, with threshold values of −0.267 and 3.602, and this double-threshold effect has temporal and regional heterogeneity. Third, environmental regulations of different intensities have a single-threshold effect between digital development, technological innovation, and industrial structure upgrade, with threshold values of 2.955, 3.957, and 2.249, respectively. Fourth, digital development, technological innovation, and industrial structure upgrade promote green economic performance. Fifth, environmental regulation acts on green economic performance through the transmission of digitalization, technological innovation, and industrial structure upgrade. Based on these empirical findings, this research suggests that Chinese local governments should appropriately increase the intensity of environmental regulations, strengthen the digital application and technological innovation, and promote the upgrading of industrial structure to achieve the improvement of urban green economic performance.

The Impact of Digitization on Green Innovation Performance: Evidence Based on Panel Data of 228 Prefectural‐Level Cities in China

At present, in the context of the era of energy and digital reform enabling the “dual carbon” goal, in order to improve the performance of urban green innovation, digitalization has become more and more important. Based on panel data, taking 228 prefecture‐level cities in China from 2003 to 2019 as an example, this study expounds three dimensions of promoting green innovation performance in the internal mechanism of digital development: direct transmission mechanism, indirect transmission mechanism, and regional heterogeneity transmission mechanism. This article uses mechanism analysis and adopts a dynamic spatial panel model and systematic GMM method to empirically test the growth effect of green innovation performance endowed by digitization. This article found that green innovation performance showed regional heterogeneity and urban heterogeneity after adding carbon dioxide emissions from energy consumption, and digital development significantly improved the level of innovation performance. Further research found that digitalization has a positive impact on technological innovation, and technological innovation also has a positive impact on green innovation performance. And technological innovation plays a mediating role between digitalization and green innovation performance. Different intensities of environmental regulation play a positive moderating role in the impact of digitalization on green innovation performance.

The Impact of Carbonated Water on Wettability: Combined Experimental and Molecular Simulation Approach

Summary Carbonated water injection has gained wide interest as an enhanced oil recovery technique. The efficiency of oil displacement during an ordinary waterflood is dictated and governed mainly by the viscous and capillary forces between oil and water. These forces are controlled by the interfacial tension (IFT) between the fluids and the contact angle (CA) with the rock surface. In this study, the pendant drop technique and molecular dynamics (MD) simulation were combined to investigate the effect of adding carbon dioxide on the water/oil/rock interfaces. CA measurement is rather a macroscopic assessment of the wettability while molecular simulation can provide further microscopic insights. The multiscale approach involves direct wettability assessment of asphaltene-containing oil against pure water or carbonated water, both exposed to two types of carbonate rock samples. Molecular characterization of asphaltenes was carried out by analytical means and different asphaltene structures were recreated on a computational platform for asphaltene-water and asphaltene-carbonated water molecular simulations. The experimental data revealed that the carbonated water caused the CA to change from weakly oil-wet to intermediate to water-wet wettability. Molecular simulation was invoked to shed more light into the underlying mechanisms behind the observed wettability alteration. In particular, molecular simulation of IFT and asphaltene swelling effect driven by the interactions with carbon dioxide were analyzed. The results were found consistent with the experiments. The findings presented in this paper highlight the viability of carbonated water for enhanced oil recovery and provide in-depth insights into the underlying mechanisms.

Formation and Cycloaddition Reactions of a Reactive Boraalkene Stabilized Internally by N‐Heterocyclic Carbene

AbstractThe synthesis of element−carbon double bonds is of great importance for the development and understanding of reactive π‐bonded systems in chemistry. The seven‐membered heterocyclic system 4 b is readily made by internal C−H activation at a pendent isopropyl methyl group of the respective [(IPr)C6F5BH]+ borenium ion. Subsequent deprotonation with the IMes carbene gives the neutral cyclic boraalkene system 5 b. The B=C double bond in compound 5 b adds carbon dioxide, CS2, sulfur dioxide, phenyl isocyanate, an acetylenic ester or two NO molecules to give the corresponding four‐membered ring annulated heterocycles. With sulfur or selenium 5 b gives the respective three‐membered ring systems. N2O reacts with 5 b to give a mixture of the related oxaborirane 18 and a unique [B]OH containing diazoalkane product 19.

Formation and Cycloaddition Reactions of a Reactive Boraalkene Stabilized Internally by N-Heterocyclic Carbene.

The synthesis of element-carbon double bonds is of great importance for the development and understanding of reactive π-bonded systems in chemistry. The seven-membered heterocyclic system 4 b is readily made by internal C-H activation at a pendent isopropyl methyl group of the respective [(IPr)C6 F5 BH]+ borenium ion. Subsequent deprotonation with the IMes carbene gives the neutral cyclic boraalkene system 5 b. The B=C double bond in compound 5 b adds carbon dioxide, CS2 , sulfur dioxide, phenyl isocyanate, an acetylenic ester or two NO molecules to give the corresponding four-membered ring annulated heterocycles. With sulfur or selenium 5 b gives the respective three-membered ring systems. N2 O reacts with 5 b to give a mixture of the related oxaborirane 18 and a unique [B]OH containing diazoalkane product 19.

Roadmap to sustainable carbon-neutral energy and environment: can we cross the barrier of biomass productivity?

The total number of inhabitants on the Earth is estimated to cross a record number of 9 × 103 million by 2050 that present a unique challenge to provide energy and clean environment to every individual. The growth in population results in a change of land use, and greenhouse gas emission due to increased industrialization and transportation. Energy consumption affects the quality of the environment by adding carbon dioxide and other pollutants to the atmosphere. This leads to oceanic acidification and other environmental fluctuations due to global climate change. Concurrently, speedy utilization of known conventional fuel reservoirs causes a challenge to a sustainable supply of energy. Therefore, an alternate energy resource is required that can maintain the sustainability of energy and environment. Among different alternatives, energy production from high carbon dioxide capturing photosynthetic aquatic microbes is an emerging technology to clean environment and produce carbon-neutral energy from their hydrocarbon-rich biomass. However, economical challenges due to low biomass production still prevent the commercialization of bioenergy. In this work, we review the impact of fossil fuels burning, which is predominantly used to fulfill global energy demand, on the quality of the environment. We also assess the status of biofuel production and utilization and discuss its potential to clean the environment. The complications associated with biofuel manufacturing using photosynthetic microorganisms are discussed and directed evolution for targeted phenotypes and targeted delivery of nutrients are proposed as potential strategies to increase the biomass production.

Влияние добавок водяного пара и диоксида углерода на характеристики процесса кислородной газификации пылеугольного топлива

The paper analyzes entrained-flow high-oxygen gasification of pulverized coal (a Shell type process)is considered. Water vapor is commonly added to increase the yield of combustible components. This research uses a mathematical model in a one-dimensional stationary approximation to see how adding carbon dioxide and a mixture of carbon dioxide and water vapor to the oxygen flow will affect the process. The paper presents estimates of thermochemical conversion rate (cold gas efficiency), combustible gas content, and completeness of fuel carbon conversion for all the tested configurations. Calculations show that adding carbon dioxide can reduce the specific oxygen consumption of the gasification process whilst ensuring more complete fuel conversion. Adjustments in the water vapor to carbon dioxide ratio help control the gas composition (albeit in a rather narrow range) and the temperature of the raw produced gas at the reaction zone outlet.

SNG Generation via Power to Gas Technology: Plant Design and Annual Performance Assessment

Power to gas (PtG) is an emerging technology that allows to overcome the issues due to the increasingly widespread use of intermittent renewable energy sources (IRES). Via water electrolysis, power surplus on the electric grid is converted into hydrogen or into synthetic natural gas (SNG) that can be directly injected in the natural gas network for long-term energy storage. The core units of the Power to synthetic natural gas (PtSNG) plant are the electrolyzer and the methanation reactors where the renewable electrolytic hydrogen is converted to synthetic natural gas by adding carbon dioxide. A technical issue of the PtSNG plant is the different dynamics of the electrolysis unit and the methanation unit. The use of a hydrogen storage system can help to decouple these two subsystems and to manage the methanation unit for assuring long operation time and reducing the number of shutdowns. The purpose of this paper is to evaluate the energy storage potential and the technical feasibility of the PtSNG concept to store intermittent renewable sources. Therefore, different plant sizes (1, 3, and 6 MW) have been defined and investigated by varying the ratio between the renewable electric energy sent to the plant and the total electric energy generated by the renewable energy source (RES) facility based on a 12 MW wind farm. The analysis has been carried out by developing a thermochemical and electrochemical model and a dynamic model. The first allows to predict the plant performance in steady state. The second allows to forecast the annual performance and the operation time of the plant by implementing the control strategy of the storage unit. The annual overall efficiencies are in the range of 42–44% low heating value (LHV basis). The plant load factor, i.e., the ratio between the annual chemical energy of the produced SNG and the plant capacity, results equal to 60.0%, 46.5%, and 35.4% for 1, 3, and 6 MW PtSNG sizes, respectively.

Colour and chemical stability of bismuth oxide in dental materials with solutions used in routine clinical practice.

Bismuth(III) oxide is included as a radio-opacifier in dental materials, including hydraulic silicate cements, the material of choice for several endodontic procedures. It has been implicated in tooth discoloration after contact with endodontic irrigants, in particular NaOCl solution, To date, there has been no work on the chemistry: all reports have been of clinical findings only. The purpose now was to report the reactions leading to colour change from Bi2O3 in contact with solutions used in routine endodontic practice. Ten-gram portions of Bi2O3 were immersed in either water, NaOH, NaCl, NaOCl or HCl solution, either in the dark or exposed to visible light, and samples retrieved at 1, 4, 12 and 24 weeks. After washing, these were exposed to either added CO2 or not, for 1 week while drying, and under the same dark or light conditions. Changes in appearance were monitored by photography and colour measurement, and chemically by X-ray diffraction and Fourier-transform infrared spectroscopy. 24-week material was studied using electron paramagnetic resonance and Raman spectroscopy; NaOCl-treated material was also examined by scanning electron microscopy. With water, NaCl and NaOH, bismuth subcarbonate was formed. With or without added carbon dioxide, discoloration occurred from pale yellow to light brown when exposed to light, and to a lesser extent in the dark, intensifying with time. In contrast, exposure to NaOCl rapidly formed a dark brown-black sodium bismuthate. With HCl, white BiOCl was formed. Bi2O3 is not at all inert in this context as is commonly believed, denying its principle of use. Previously unreported solution-mediated reaction occurs readily even in water and NaCl solution, forming new compounds that discolour. In contact with NaOCl sodium bismuthate is formed; severe darkening occurs rapidly. The reactivity is such that Bi2O3 is not indicated for dental materials and should be withdrawn from use.

Carbon dioxide improves ethanedinitrile efficacy for fumigating the stored product pests Rhyzopertha dominica and Lasioderma serricorne

The toxicity of ethanedinitrile (EDN), an alternative fumigant for stored products, is decreased due to the high sorption of the gas in treated commodities. This laboratory study examined adding carbon dioxide to EDN to increase activity against Rhyzopertha dominica and Lasioderma serricorne at 25 °C, 50–70% R.H and a photoperiod of 16 L:8D h for 24 h. CO2 at 30% with the estimated LC25 dose of EDN exhibited a significant effect on the mortality of adults of R. dominica and the larvae, pupae, and adults of L. serricorne. Adults emerged from the mixed life stage cultures of R. dominica exposed to a mixture of 75 ppm or 150 ppm of EDN and CO2 at 10, 20 and 30% averaged 26.8, 11.5 and 4.9, and 1.5, 0.6 and 0.9, respectively. Averages of 188.6 and 56.6 adults resulted from cultures of R. dominica fumigated with EDN at 75 and 150 ppm alone, respectively. The L. serricorne cultures exposed to EDN at 500 or 1000 ppm plus 10, 20, and 30% of CO2 yielded average numbers of emerged adults of 170.5, 110.9 and 114.6, and 68.3, 30.2 and 31.9, respectively, compared to 358.3 and 173.6 in cultures treated with 500 and 1000 ppm of EDN alone, respectively. Numbers of adults of both species emerged from cultures exposed to either EDN or CO2 alone in the presence of commodities were significantly higher than those exposed to the EDN + CO2 (30%) mixture. These results clearly indicated the positive effect of CO2 on toxicity of EDN that can overcome the decrease of EDN toxicity against the treated insects due to its sorption in commodities.

Anaerobic Metabolism Markers as a Guide of Resuscitation Effort and Mortality Benefit in Septic Shock Among Egyptian Population

Introduction: Venous-to-arterial carbon dioxide pressure and ratio of carbon dioxide gap divided by difference in arterial-venous oxygen content might be relevant in septic shock management. The aim of this study was to evaluate whether carbon dioxide gap and ratio of carbon dioxide gap divided by difference in oxygen content following septic shock resuscitation could predict mortality. Methods: Fifty septic shock patients were included in this study. Arterial and central venous blood gas samples were measured before and 6 hours following fluid resuscitation and vasopressors. Results: Our study population was 61.6 ± 7.4 years (31 males). Thirty-three patients survived. Paired comparisons in nonsurvivors showed worsening hemodynamics, carbon dioxide gap, ratio of carbon dioxide gap divided by difference in oxygen content, and lactate clearance. Mortality prediction cutoffs for lactate (40 mg/dl) with sensitivity (88.2%) and specificity (78.8%), carbon dioxide gap (6 mmHg) with sensitivity (94.1%) and specificity (63.6%) and ratio of carbon dioxide gap divided by difference in oxygen content (1.6) with sensitivity (88.2%) and specificity (60.6%). Combined lactate and the ratio of carbon dioxide gap divided by difference in oxygen content had sensitivity of 88.2% and specificity of 93.9%. Combined lactate and carbon dioxide gap had sensitivity of 82.4% and specificity of 90.9%. Discussion: Changes in carbon dioxide gap and ratio of carbon dioxide gap divided by difference in arterial-venous oxygen content during resuscitation of septic shock were related to in-hospital mortality. Adding carbon dioxide gap and the ratio of carbon dioxide gap divided by difference in arterial-venous oxygen content to lactate increased the accuracy of mortality prediction.

Beneficiation of coal using supercritical water and carbon dioxide extraction: sulfur removal

This work explores the use of carbon dioxide, water, and their mixtures as solvent for the precombustion beneficiation of raw coal without using any toxic mineral acids in the temperature range of 200–400 °C. The fluid polarity, ionic constant, and supercritical point can be adjusted by H2O/CO2 ratio and temperature. Adding carbon dioxide to hydrothermal fluid also increases the ionization by forming carbonic acid. Extractions with supercritical fluids have several benefits including enhanced mass transport, ease of separation and recycle, wide range of extractive capability and tunability, better inherent safety, and in the case of carbon dioxide and water–low cost. A semi-continuous extraction system was designed and built in which pressure, temperature and the relative flow rates of CO2 and H2O can be controlled. Coal powder is kept in a packed bed and the extraction is carried out at 143 bar pressure. Using sulfur as a model heteroatom, extractive efficiency is examined as a function of the temperature, fluid composition, fluid flow, and extraction time. The results indicate that carbon dioxide, water, and supercritical water-carbon dioxide (ScWC) all can effectively extract about 50% of total sulfur from bituminous coal in 1 h. Extraction above 350 °C decreased effectiveness, and extraction above the supercritical point of pure water caused hydrothermal carbonization. ScWC extraction may provide necessary control to prevent organic dissolution while removing sulfur.

THERMODYNAMIC LAWS OF CHROMIUM REDUCTION BY MIXTURES OF СН4 + Н2О AND СН4 + СО2

The development of a physico-chemical model of methane behavior in the processes of solid-phase reduction of chromium-containing raw materials will allow us to create the technological basis for the production of multicomponent sponge ligatures. The reduction of oxides with methane is accompanied by the deposition of soot carbon. The negative effect of carbon black, which is blocking the reaction surface, can be eliminated by adding carbon dioxide or water vapor to methane. A thermodynamic analysis of the reduction of chromium oxide with mixtures of CH4-CO2, CH4-H2O was carried out. The effect of the partial replacement of methane by carbon on the thermodynamic preferences of the process is analyzed. A physicochemical model of the behavior of the CH4 molecule in the recovery process is proposed. The thermodynamic features of reduction at various ratios of СН4 are considered: (Н2О, СО2, О2), as well as the composition of the mixture (Н2О+СО2+О2), which ensure the conditions of solid-phase reduction of oxides and the product of carbide destruction. The use of CH4 + H2O + O2 mixtures in the reduction of chromium oxide is thermodynamically less effective. The use of a mixture of СН4 + Н2О + СО2 has a very insignificant effect on the conversion of methane, and also reduces the thermodynamic preference for the reduction of Cr2O3 in comparison with СН4 + Н2О + О2 and СН4 + Н2О. However, it should be noted that in addition to CO and H2, carbon can be present in the reduction products, so the high reduction potential in this process variant (C+CO+H2) can be used to reduce oxides. The reduction of chromium oxide with mixtures of СН4 + Н2О + О2, СН4 + Н2О, and СН4 + Н2О + СО2 can be thermodynamically realized in the temperature range excluding the melting of the charge. As a result of this process, a carbide phase is formed, as well as a gas phase, which has a high reduction potential and can be used in further technological schemes. Meanwhile, it seems possible to control the carbon content in the sponge ligature by selecting the optimal composition of the source gas mixture.

Laminar burning speeds and flame instabilities of isobutane carbon dioxide air mixtures at high pressures and temperatures

Liquefied petroleum gases (LPGs), such as isobutane and propane, find applications as working fluids in refrigeration and as fuels in internal combustion engines. Isobutane is typically used as a precursor molecule in the synthesis of isooctane, a component of gasoline. It can also be used as a natural low global warming potential (GWP) refrigerant, however, there are fire safety concerns. This work investigated the effects of adding carbon dioxide (CO2) to isobutane (iC4H10) to evaluate its effects on flammability and flame propagation. This paper also compared isobutane results with propane (the major LPG component) results, which were adapted from a previous study. The laminar burning speeds of blends of iC4H10/CO2/air were measured in a constant volume spherical chamber. The flame stability/instability was evaluated in a cylindrical chamber where the flame propagation was captured with a high-speed camera in a Z-shaped Schlieren system. A power law correlation was developed to determine laminar burning speeds for blends of iC4H10/CO2/air at CO2 mole fractions of 0–80%, equivalence ratios of 0.8–1.2, temperatures of 298–580 K, and pressures of 0.5–4.2 atm. Results were compared with experimental studies from the literature and numerical data obtained using 1–D premixed flame code from CANTERA. Both experiments and numerical predictions showed that the laminar burning speeds of iC4H10/CO2 mixtures decreased with increasing CO2 mole fraction, and that the maximum laminar burning speed shifted towards stoichiometric mixture. Carbon dioxide acted as an inhibitor of flame instability, as verified both experimentally by photography and theoretically by calculating the critical Peclet number.

Comprehensive Analytical Study of the Greenhouse Effect of the Atmosphere

Climate change is an important societal issue. Large effort in society is spent on addressing it. For adequate measures, it is important that the phenomenon of climate change is well understood, especially the effect of adding carbon dioxide to the atmosphere. In this work, a theoretical fully analytical study is presented of the so-called greenhouse effect of carbon dioxide. The effect of this gas in the atmosphere itself was already determined as being of little importance based on empirical analysis. In the current work, the effect is studied both phenomenologically and analytically. In a first attempt of energy transfer by radiation only, it is solved by ideal-gas-law equations and the atmosphere is divided into an infinite number of layers each absorbing and reemitting infrared radiation (surpassing the classical Beer-Lambert analysis of absorption). The result is that the exact structure of the atmosphere is irrelevant for the analysis; we might as well keep the two-box model for any analytical approach. However, the results are unsatisfactory in that they cannot explain the profile of the atmosphere. In a new approach, the atmosphere is solved by taking both radiative as well as thermodynamic processes into account. The model fully fits the empirical data and an analytical equation is given for the atmospheric behavior. Upper limits are found for the greenhouse effect ranging from zero to a couple of mK per ppm CO2. It is shown that it cannot explain the observed correlation of carbon dioxide and surface temperature. This correlation, however, is readily explained by Henry’s Law (outgassing of oceans), with other phenomena insignificant. Finally, while the greenhouse effect can thus, in a rudimentary way, explain the behavior of the atmosphere of Earth, it fails describing other atmospheres such as that of Mars. Moreover, looking at three cities in Spain, it is found that radiation balances only cannot explain the temperature of these cities. Finally, three data sets with different time scales (60 years, 600 thousand years, and 650 million years) show markedly different behavior, something that is inexplicable in the framework of the greenhouse theory.

Voltammetric study of one-step electrochemical methane production during water and CO2 co-electrolysis in molten CsH2PO4

Cyclic voltammetry was performed with a nickel electrode in molten CsH2PO4 at 350 °C and at approximately 25 bar of water pressure. The effect of adding carbon dioxide was examined. It is found that even small amounts of CO2 (partial pressure below 0.2 bar at 350 °C, corresponding to 0.5 bar at 22 °C of a 5:1 mixture of N2:CO2) have a pronounced effect on the cyclic voltammetry curves. Under these conditions the hydrogen formation is substituted by another process, methane formation. At the same time the cathodic current increased by a factor of 4–6, meaning that the ease of methanisation was much improved.