Carbon Dioxide Vapor Research Articles

Oxidation of molten impurities in converters by means of combustion flames: Thermodynamic principles. 1. Thermodynamic analysis of processes in natural-gas combustion

In the production of steel, as the productivity rises and the resource and energy consumption declines, improvements in converter design are required to ensure preliminary scrap and batch heating and to intensify redox processes in the liquid bath and exhaust-gas combustion above the bath, without impairing the durability of the injection systems and the converter lining. The use of fuel–oxygen combustion flames in the converter resolves numerous technological problems. The hydrodynamics in the reaction zones and in the liquid bath may be greatly changed by fuel combustion in the converter’s working space with jet formation or by means of submersible combustion flames. In the present work, thermodynamic methods are used to analyze the dynamics of gaseous-fuel combustion and the oxidation of elements in the converter bath on interaction with high-temperature combustion products. The interaction of the combustion flame and chemical elements in the converter bath is calculated for equilibrium conditions. The use of the combustion flames is found to change the composition of the gas phase in the converter’s working space (above the bath), which contains H2 and H2O in addition to the traditional components associated with oxygen injection: O2, CO, CO2. The presence of H2 and H2O changes the thermal conditions and oxidative properties of the gas phase. In the combustion of gas–oxygen fuel, the optimal composition of the initial gas mixture (natural gas + oxygen) must correspond to the ratio 100% CH4 + 69% O2. The oxidation product is gaseous phase consisting of 40% CO2 + 60% H2O. The total enthalpy of combustion of the gas–oxygen fuel at converter temperatures, with an oxygen excess greater than 1.0 (up to 2.0), is about 200 kJ per mole of the initial reagents. In the oxidation of methane by carbon dioxide, the total enthalpy of combustion is between–7 and–14.5 kJ/mol of initial reagents at 1800 K. The process becomes endothermal at temperatures above 2000 K: ΔH 2200 = 7.7–15.4 kJ/mol. In the oxidation of natural gas by water vapor, ΔH 1800–2200 = 19.5–70 kJ/mol. Thus, flame temperatures above 1800 K may only be attained in the oxidation of methane by oxygen. The use of air, carbon dioxide, or water vapor as the oxidant does not yield the required thermal effect.

УМЕНЬШЕНИЕ МОЩНОСТИ ПРИВОДА КОМПРЕССОРА ДЛЯ СЖАТИЯ ДИОКСИДА УГЛЕРОДА ПРИ ПРОИЗВОДСТВЕ КАРБАМИДА

It is proposed to replace the adiabatic compression of carbon dioxide vapor to a high pressure, used at carbamide production, by isothermal or poliropic compression. This significantly reduces the compressor drive power, reduces the temperature at the end of the compression and improves the compressor working conditions. At transition to isothermal compression of CO2 the specific energy consumption decreases from 0,106 to 0,076 kWh/kg, and at politropic compression — to 0,087 kWh/kg. Such modernization of the plant with the capacity of 45 tons of CO2 per hour will reduce the compressor drive effective power from 4759 to 3431 kW at the first case and to 3894 kW at the second, which will result in savings of 11,63 and 7,58 GW.h of electrical energy per year correspondingly.

Modeling of electrochemical processes in solid oxide fuel cells

A mathematical model of electrochemical processes in a solid oxide fuel cell is presented. A procedure for the calculation of the current—voltage characteristic (CVC) taking into account the influence of the reagent concentration, pressure, and temperature is considered. The problem of calculation of the electromotive force (emf) and thermodynamic efficiency was studied in detail. The influence of the presence of carbon dioxide and water vapor in the anode gas on the emf and thermodynamic efficiency is analyzed. The method of measuring the CVC in an experiment at a constant fuel rate is briefly considered. The results of application of the calculation model are compared with the experimental data.

Local treatment of chronic wounds

Lokaltherapie chronischer Wunden Phlebologie 2016; 45: 106–112 http://dx.doi.org/10.12687/phleb2297-2-2016 Received: November 29, 2015 Accepted: December 07 ,2016 A wide range of modern wound dressings are available in Germany today and it is difficult to keep track of them because new products are continuously appearing on the market. This article summarises the various options for the treatment of chronic wounds, based on problems of relevance to everyday practice. The use of modern dressings appropriate to the stage of the wound can really only be based on empirical observations, because comparative studies are lacking. This article therefore makes no claim to be an exhaustive review. Before deciding on the most suitable wound dressing, the cause of the wound must always be established first and appropriate causal treatment instituted (e.g. compression therapy for venous leg ulcers, revascularisation for arterial leg ulcers or immunosuppression in the case of pyoderma gangrenosum). When prescribing wound dressings, the sometimes considerable costs must generally be taken into account. In addition, they must be easy to apply and remove completely, must offer mechanical protection, absorb wound secretion in a reliable manner and be permeable to carbon dioxide, oxygen and water vapour. Further requirements on wound dressings include thermal insulation and the prevention of dehydration (principle of moist wound treatment). They should be made from hypoallergenic, non-toxic materials and be sterile-packed. (1) Dressing appropriate for phase of wound healing

On the significant enhancement of the continuum-collision induced absorption in H2O+CO2 mixtures

The IR spectra of water vapor–carbon dioxide mixtures as well as the spectra of pure gas samples have been recorded using a Fourier-transform infrared spectrometer at a resolution of 0.1cm−1 in order to explore the effect of colliding CO2 and H2O molecules on their continuum absorptions. The sample temperatures were 294, 311, 325 and 339K. Measurements have been conducted at several different water vapor partial pressures depending on the cell temperature. Carbon dioxide pressures were kept close to the three values of 103, 207 and 311kPa (1.02, 2.04 and 3.07atm). The path length used in the study was 100m. It was established that, in the region around 1100cm−1, the continuum absorption coefficient CH2O+CO2 is about 20 times stronger than the water–nitrogen continuum absorption coefficient CH2O+N2. On the other hand, in the far wing region (2500cm−1) of the ν3 CO2 fundamental band, the binary absorption coefficient CCO2+H2O appears to be about one order of magnitude stronger than the absorption coefficient CCO2+CO2 in pure carbon dioxide. The continuum interpretation and the main problem of molecular band shape formation are discussed in light of these experimental facts.

Thin-layer chromatography of benzoic acids with a controlled gas phase: A comparison of different stationary phases

A comparison of the chromatographic behavior of benzoic acids on normal (silica gel), reversed (RP-18), and polyamide-11 plates using thin-layer chromatography (TLC) with controlled gas phase inside the chamber has been performed. This variant of TLC is based on the use of a gas phase moving over the TLC plate for regulation of the stationary and mobile phases as well as the acid—base properties of analytes during the separation process. The feasibility of such an approach is illustrated by the separation of benzoic acid derivatives using carbon dioxide, ammonia, and acetic acid vapor. It was shown that a gradual change of mobile phase acidity makes it possible to enhance separation efficiency and selectivity, this effect being dependent on the type of the stationary phase. The most considerable change in the retention of benzoic acid derivatives was observed for normal-phase plates with silica gel or silica sol, or starch binders used as the stationary phase. An alteration of surface acidity for polyamid...

Electrical properties of gas sensors based on graphene and single-wall carbon nanotubes

Here, we present investigation of the influence of different gases (carbon dioxide, ammonia, and iodine vapor) on the sensory properties of graphene and single-wall carbon nanotube films. The gas molecules are adsorbed by carbon films (graphene or nanotubes) and change the film’s electrical resistance. In the course of this work, the setup for studying the electrophysical properties of carbon nanomaterials has been designed and constructed in the lab. With this home-made equipment, we have demonstrated a high efficiency of graphene and nanotubes as adsorbents of different gases and a possibility to use these materials as gas sensors. We have also performed a chemical modification of graphene and carbon nanotubes by attaching the nanoparticles of calcium carbonate (CaCO3) to improve the sensitivity and selectivity of sensors.

Analytical Approach to Calculate the Heat Fluxes in the Atmosphere and to Quantify the Sensitivity of Earth Temperature due to CO2 and H2O

A mathematical model has been developed to understand the effect of carbon dioxide and water vapor on the mechanism of global warming. First, the increase of the CO2 concentration in the atmosphere could be based on the anthropogenic CO2 emissions according to the combustion of fossil fuels. Second, the heat fluxes in the atmosphere were described by known relations in thermal engineering. Here, the heat transfer due to radiation between the gas which contains water vapor and carbon dioxide, and the Earth's surface as well as the clouds is considered. The emissivity of the gases depends on temperature, and the gas concentration and the beam length of the atmospheric layer. The sensitivity of this model was quantified less, when e.g. the cloud height and the relative humidity of the atmosphere were varied. The known average temperature of the Earth was used to validate this model. The temperature of the Earth increases significantly with the CO2 concentration. When the concentration of CO2 is doubled, the temperature of the Earth increases by 0.43 K.

An Approach to Removing Large Quantities of Atmospheric Greenhouse Gases

A method for removing atmospheric carbon dioxide (СО2) and water vapor is proposed. The method sprays clouds with alkaline compounds to significantly increase the solubility of СО2 in the cloud water, providing for much higher than normal levels of СО2 to be absorbed by rain droplets. The CO2 is transported to the ground for sequestration in surface and/or ground water, and available for carbon fixation by plants and organisms. Presented calculations estimate that 38 gigatonnes of atmospheric CO2 could be removed per year by applying the process over 0.08% to 2.4 % of the Earth’s surface. Laboratory experiments that grew multiple edible plant species irrigated with the modified rainwater indicated yield benefits. A concept for removing atmospheric methane (CH4) is also presented. Powerful lasers would ionize the CH4 to form CO2 that could then be removed by the alkaline-enhanced rainfall method.

Influence of combustion-preheating vitiation on operability of a hypersonic inlet

Vitiation of the test flow with combustion products is inherent in combustion wind tunnels, and its effect on experimental results needs to be clarified. In this study, the influence of air vitiation on the startability and performance of a hypersonic inlet is investigated through two-dimensional (2D) numerical simulation. The study examines the vitiation effects introduced by carbon dioxide and water vapor, on the basis of maintaining the static pressure, static temperature and Mach number of the incoming flow. The starting Mach number limits of the inlet are estimated, and it is found that both of these vitiation components lower the starting limit of the inlet. This suggests that the experimental results acquired by tests in combustion wind tunnels overestimate the startability of an inlet and, therefore, combustion-preheated facilities may not be completely trusted in this respect. Deviations in the inlet performance caused by the vitiation are also detected. These are nevertheless minor as long as the flow is at the same started or unstarted condition. A further analysis reveals that it is mainly the increase in the heat capacity, and the resulting weaker shock/compression waves and shock-wave/boundary-layer interactions that account for the aforementioned effects.

The fluid regime of crystallization of water-saturated granitic and pegmatitic magmas: a physicochemical analysis

Miarolitic granite pegmatites are a unique natural object that makes it possible to study magmatic processes that lead to the formation of ore-forming media and systems. This paper summarizes modern views on phase transformations in aqueous silicate systems at parameters close to those of the transition from magmatic to hydrothermal crystallization. Comparison of phase diagrams and the results of study of pegmatite-forming media permits making conclusions about the crystallization of the water-saturated magmas of miarolitic granite pegmatites. The fluid regime of aqueous granite systems of simple composition, not enriched in fluxing components, is determined mainly by magma degassing or the supply of volatiles with flows of transmagmatic fluids. These processes cause the separation of essentially carbon dioxide or essentially hydrous fluid. During the evolution of such magmas, crystallization from silicate melt is separated in PT-space and, possibly, in time from the crystallization from aqueous or mixed carbon dioxide-aqueous super- and subcritical solutions. The evolution of chambers of water-saturated granitic and pegmatitic magma enriched in F, B, and alkali metals presupposes the formation of a heterogeneous mineral-forming medium in which crystallization occurs in the magmatic melt at high-temperature stages; as temperature decreases, crystallization can proceed in hydrous fluid, hydrosilicate, and/or hydrosaline liquids simultaneously. Hydrothermal crystallization can also take place in a heterogeneous medium consisting of aqueous solutions of different salinities and vapor or vapor-carbon dioxide gas mixture. The relationship between different fluid regimes during the evolution of volatile-saturated granitic and pegmatitic magmas determines the variety of postmagmatic rocks accompanying granite massifs.

Microclimate measuring and fluid‑dynamic simulation in an industrial broiler house: testing of an experimental ventilation system.

The environment in the broiler house is a combination of physical and biological factors generating a complex dynamic system of interactions between birds, husbandry system, light, temperature, and the aerial environment. Ventilation plays a key role in this scenario. It is pivotal to remove carbon dioxide and water vapor from the air of the hen house. Adequate ventilation rates provide the most effective method of controlling temperature within the hen house. They allow for controlling the relative humidity and can play a key role in alleviating the negative effects of high stocking density and of wet litter. In the present study the results of experimental tests performed in a breeding broiler farm are shown. In particular the efficiency of a semi transversal ventilation system was studied against the use of a pure transversal one. In order to verify the efficiency of the systems, fluid dynamic simulations were carried out using the software Comsol multiphysics. The results of this study show that a correct architectural and structural design of the building must be supported by a design of the ventilation system able to maintain the environmental parameters within the limits of the thermo‑neutral and welfare conditions and to achieve the highest levels of productivity.

Study on the Basic Characteristics of Low Oxygen Air Combustion with Natural Gas in Glass Tempering Furnace

The basic characteristics of natural gas with low oxygen air combustion is analyzed, and low oxygen content, excess air ratio, and the change of flue gas composition are studied, the results show that using the technology of low oxygen air combustion for glass tempering furnace in production has directive significance. The composition content of carbon dioxide and water vapor increases in the combustion products. The radiation heat transfer is decreased in glass tempering furnace. The furnace temperatures are maintained in the range of 650 to 800°C.

Experimental study of the effect of water injection on the cycle performance of an internal-combustion Rankine cycle engine

The internal-combustion Rankine cycle engine uses pure oxygen instead of air as the oxidant during the combustion process so as to preclude the creation of nitrogen oxide emissions. Carbon dioxide can be recovered from the water vapour–carbon dioxide exhaust gas mixture through condensation at a relatively low cost and, thus, an ultra-low-emission working cycle is achieved. In this paper the working process of the internal-combustion Rankine cycle was studied on the basis of bench tests on a prototype engine. An oxygen–carbon dioxide mixture was utilized to simulate exhaust gas recirculation in order to control the combustion process, and water was injected near top dead centre to determine the impact on the reaction rate and the cycle performance. The results demonstrated that water injected at a temperature of 120 °C can modulate the reaction rate and expand the area of the pressure–volume diagram through vaporization. Furthermore, combustion phasing is retarded without reducing the maximum cylinder pressure. The indicated work under the test conditions is increased by 7.8%. However, when the water-injection temperature is 20 °C, the cycle performance is reduced.

Dynamics of the Oxygen, Carbon Dioxide, and Water Interaction across the Insect Spiracle

This paper explores the dynamics of respiratory gases interactions which are accompanied by the loss of water through an insect’s spiracle. Here we investigate and analyze this interaction by deriving a system of ordinary differential equations for oxygen, carbon dioxide, and water vapor. The analysis is carried out in continuous time. The purpose of the research is to determine bounds for the gas volumes and to discuss the complexity and stability of the equilibria. Numerical simulations also demonstrate the dynamics of our model utilizing the new conditions for stability and instability.

Resistance of composite materials based on BaCeO3 against the corrosive effects of carbon dioxide and water vapour at intermediate fuel cell operating temperatures

The objective of this work is to analyse the chemical stability of BaCe0.85Y0.15O3−δ –Ce0.85Y0.15O2−δ (BCY15–YDC15) composite materials at 600 °C and to compare the aforementioned chemical stability with that of pure BCY15. The composite powders were obtained by mixing together powders of BCY15 and YDC15 in the following volume fractions: 90 % BCY15 + 10 % YDC15, 70 % BCY15 + 30 % YDC15, 30 % BCY15 + 70 % YDC15, 20 % BCY15 + 80 % YDC15 and 10 % BCY15 + 90 % YDC15. After that both powders and sintered samples of the BCY15 and the BCY15–YDC15 composites were saturated in two different atmospheres at 600 °C: CO2/H2O (3.1 mol% H2O) and N2/H2O (46.8 mol% H2O). The effects of the previously mentioned atmospheres on the physicochemical properties of the samples were investigated via differential thermal analysis (DTA) combined with thermogravimetric analysis (TG). Furthermore, mass spectrometry was used to analyse the chemical composition of the gases released from the samples during the DTA–TG heating process. The surface and cross-section morphology of the samples were examined by scanning electron microscopy. Moreover, the phase composition of each sample was studied via X-ray Diffraction. From the combined analysis, it can be concluded that the addition of YDC15 in the composite samples leads to an increase in resistance against the corrosive effects of CO2. Furthermore, it was determined that all samples maintain stability in the presence of H2O at 600 °C.

Synthesis of ultrafine green-emitting BaCO3 nanowires with 18.5 nm-diameter by CO2 vapor-assisted electrospinning

The authors report the first preparation of high-density ultrafine green-emitting wool-like BaCO3 nanowires, having an average diameter of 18.5 nm, and an average crystallite size of 13.4 nm, by an electrospinning method with a subsequent two-step calcination approach. A possible vapor–solid interaction mechanism was proposed for the finest nanowires growth, where the reactive carbon dioxide vapors were generated during the static atmosphere ambient calcination and assisted oxidization nucleation at enhanced temperatures. Our work provides new insights into electrospun fiber diameter refinement via controlled calcination, and this simple post-electrospinning controlled strategy can be generally applied to other metal carbonate ultrafine NWs families.

Influence of the Hydrothermal Pre-treatments on the Adsorption Characteristics of Activated Carbons from Woods

The hydrothermal treatments were conducted prior to the carbonization of oak woods and the obtained charcoals were activated using carbon dioxide or water vapor. The hydrothermal treatments brought about the elutions of acid-soluble lignin fractions as well as hemicellulose fractions accompanied with the decomposition of lignin carbohydrate complexes in the cell walls, which lowered not only the carbon yield of charcoal but also the crystal parameters for the carbon crystallites. However, the activated carbons (AC) produced via the hydrothermal pre-treatment showed superior adsorption properties especially for the adsorptions of 2-methylisoborneol and geosmin as compared with the untreated commercial AC. The hydrothermal treatments prior to the carbonization have some potential to increase the fractions of meso-pores effective for the adsorption of globular shaped molecules.

Adsorption of gases on layered silicates at high pressures

Equilibrium adsorption of nitrogen, carbon dioxide, and argon was examined on the sodium and pyridinium forms of montmorillonite and on the hydrogen form of bentonite. The measurements were carried out at 303, 343, 373, and 400 K over pressure ranges of 0.1–90 MPa (Ar and N2) and 0.1–6 MPa (CO2). The amount of nitrogen vapor adsorbed was determined at 77 K and pressures from 0 to 0.1 MPa. The porous structure parameters of the studied samples were determined using adsorption isotherms of nitrogen, argon, and carbon dioxide vapors. At elevated temperatures and pressures >10 MPa, Ar and N2 adsorption processes on the Na-form of montmorillonite and Ar adsorption on bentonite are activated, since the amounts of the gases adsorbed and adsorption volumes increase with temperature. No activated adsorption is observed for carbon dioxide adsorption on these adsorbents. A comparison of the excess adsorption isotherms of gases on the Py-form of montmorillonite and H-form of bentonite shows that adsorption in micropores predominates for the Py-form of montmorillonite, whereas for the Na-form of bentonite and H-form of bentonite adsorption occurs mainly in meso- and macropores.

Combustion of toluene catalyzed by Pt/Co3O4/CeO2-ZrO2-SnO2/r-Al2O3

A 1wt%Pt/Co3O4/CeO2-ZrO2-SnO2/r-Al2O3 catalyst was prepared to realize complete combustion of toluene at the lowest temperature possible without excessive use of platinum particles. The addition of Co3O4 to Pt/ CeO2-ZrO2-SnO2/r-Al2O3 as a promoter was effective in decreasing the amount of platinum without significant reduction in the catalytic activity. The highest activity for the combustion of toluene was observed using the 1wt%Pt/11wt%Co3O4/16wt%Ce0.62Zr0.20Sn0.18O2.0/r-Al2O3 catalyst, and despite a smaller platinum loading in the present catalyst, toluene was completely oxidized to carbon dioxide and water vapor at a lower temperature of 160 oC compared to that using 5wt%Pt/r-Al2O3 at 170 oC.