Increase In CO2 Content Research Articles

Electrode kinetics of the NiO porous electrode for oxygen production in the molten carbonate electrolysis cell (MCEC).

The performance of a molten carbonate electrolysis cell (MCEC) is to a great extent determined by the anode, i.e. the oxygen production reaction at the porous NiO electrode. In this study, stationary polarization curves for the NiO electrode were measured under varying gas compositions and temperatures. The exchange current densities were calculated numerically from the slopes at low overpotential. Positive dependency on the exchange current density was found for the partial pressure of oxygen. When the temperature was increased in the range 600-650 °C, the reaction order of oxygen decreased from 0.97 to 0.80. However, there are two different cases for the partial pressure dependency of carbon dioxide within this temperature range: positive values, 0.09-0.30, for the reaction order at lower CO2 concentration, and negative values, -0.26-0.01, with increasing CO2 content. A comparison of theoretically obtained data indicates that the oxygen-producing reaction in MCEC could be reasonably satisfied by the reverse of oxygen reduction by the oxygen mechanism I, an n = 4 electron reaction, assuming a low coverage of oxide ions at high CO2 content and an intermediate coverage for a low CO2 concentration.

Parameters affecting CO2 production in a planar anode supported SOFC based system

An attractive feature of solid oxide fuel cell (SOFC) -based systems is the opportunity to combine the co-generation of electrical and thermal energy with carbon dioxide capture. CO2 from SOFC based systems can be easily captured for underground disposal and used for several technological applications including the production of synthesis-gas. In this work, the concentration of CO2 at the outlet of a system consisting of a pre-reformer, SOFC stack and a water gas shift reactor was investigated with respect to the operating parameters.The results demonstrate that a combination of very high CO2 content in the dry anode off-gas (50–65%) with a high electrical efficiency generated by the stack (>50%) can be obtained in a SOFC system fueled with natural gas. The stack fuel utilization (FU) was observed to be one of the major parameters which affects the exhaust gas composition, increasing the FU results in an increase of CO2 content on the dried stream. On the other hand, the amount of CO2 produced is not significantly influenced by the stack operating temperature.

Effects of shielding gas composition on arc profile and molten pool dynamics in gas metal arc welding of steels

In gas metal arc welding, gases of different compositions are used to produce an arc plasma, which heats and melts the workpiece. They also protect the workpiece from the influence of the air during the welding process. This paper models gas metal arc welding (GMAW) processes using an in-house simulation code. It investigates the effects of the gas composition on the temperature distribution in the arc and on the molten pool dynamics in gas metal arc welding of steels. Pure argon, pure CO2 and different mixtures of argon and CO2 are considered in the study. The model is validated by comparing the calculated weld profiles with physical weld measurements. The numerical calculations reveal that gas composition greatly affects the arc temperature profile, heat transfer to the workpiece, and consequently the weld dimension. As the CO2 content in the shielding gas increases, a more constricted arc plasma with higher energy density is generated as a result of the increased current density in the arc centre and increased Lorentz force. The calculation also shows that the heat transferred from the arc to the workpiece increases with increasing CO2 content, resulting in a wider and deeper weld pool and decreased reinforcement height.

Effect of operating conditions on the performance of solid electrolyte membrane reactor for steam and CO2 electrolysis

Solid electrolyte membrane reactor (SEMR) based on the Ni–YSZ (yttria-stabilized zirconia) supported YSZ electrolyte membrane was developed and used in the high-temperature electrochemical reduction of steam, CO2 and a mixture of steam-CO2. Effect of different operating parameters such as temperature, feed gas composition, and operating voltage on the performance of SEMR in a high steam and/or CO2 environment was investigated. Experiments were performed in the temperature range of 750–850°C with 20% H2–80% oxidant as a feed to the Ni–YSZ electrode and air to the LSM electrode. The electrochemical performance was investigated using the current density–voltage (i–V) curves and electrochemical impedance spectra (EIS). A high area-specific resistance (ASR) was observed in a fuel cell mode as compared to the electrolysis mode because of very low fuel content and consequently, a higher concentration polarization. At 850°C and 1.5V, a very high current density of −1.9A/cm2, −1.5A/cm2 and −1.2A/cm2 is observed for steam, steam-CO2 (co-electrolysis) and CO2 electrolysis respectively. The decrease in electrochemical performance with increasing CO2 content was found to be related to the mass transport limitation of the fuel electrode. An equivalent circuit model was used to fit the impedance data and separate the various polarization losses in the cell. EIS results showed that different performance limiting step is involved depending on the operating conditions. At low operating temperature and/or cell voltage, the polarization losses at LSM oxygen electrode contributed significantly to total ASR of the cell, whereas at high operating temperature and cell voltage, the concentration polarization at fuel electrode led to a decrease in the cell performance.

Three-dimensional numerical modeling on high pressure membrane reactors for high temperature water-gas shift reaction

This study presents a three-dimensional numerical model that simulates the H2 production from coal-derived syngas via a water-gas shift reaction in membrane reactors. The reactor was operated at a temperature of 900 °C, the typical syngas temperature at gasifier exit. The effects of membrane permeance, syngas composition, reactant residence time, sweep gas flow rate and steam-to-carbon (S/C) ratio on reactor performance were examined. Using CO conversion and H2 recovery to characterize the reactor performance, it was found that the reactor performance can be enhanced using higher sweep gas flow rate, membrane permeance and S/C ratio. However, CO conversion and H2 recovery limiting values were found when these parameters were further increased. The numerical results also indicated that the reactor performance degraded with increasing CO2 content in the syngas composition.

Carbon dioxide in silica-undersaturated melt. Part I: The effect of mixed alkalis (K and Na) on CO2 solubility and speciation

Silica undersaturated melts such as nephelinites are very peculiar magmatic materials. Their occurrence on Earth is often associated with carbonatite melts. These low-silica melts can dissolve a large quantity of CO2 and are rich in alkalis. However, the way CO2 dissolves into these melts and the effect of different alkali elements are poorly constrained.We present experimental results on the CO2 solubility and speciation in synthetic nephelinite in the NKCMAS system, equilibrated at high-pressure (50–300MPa), high-temperature (1250°C) with an excess C–O–H fluid phase. The nephelinitic glasses with 20mol.% total alkali oxides were synthesized with varying K2O/(K2O+Na2O) ratio (denoted as #K) in order to investigate the differential effect of those two alkali cations on CO2 solubility and speciation. All experiments were conducted under oxidizing conditions (>NNO+3) resulting in binary fluid phase compositions with CO2 and H2O species. The CO2 content and speciation were investigated using micro-Raman and Solid State NMR spectroscopies for 13C nucleus.We observe an increase in CO2 content as a function of pressure, consistent with previous studies but CO2 solubility is much higher than in alkali-poorer melts. The CO2 content is above 1wt.% at 50MPa and increases up to 4.5wt.% at 300MPa. The progressive replacement of Na by K (#K between 0 and 1) induces an increase in CO2 content. At 50MPa, the CO2 solubility is ∼1.75wt.% in the K-free glass (#K=0) and increases up to ∼3.0wt.% CO2 in Na-free glass (#K=1). The change in CO2 solubility as a function of #K is discussed in terms of carbonatite genesis.The 13C NMR spectra show that carbonate (CO32−) environments can be attributed to carbonate species associated to non-bridging oxygen in agreement with the depolymerized nature of the investigated compositions. Two singular additional carbonated species were also identified with 13C NMR signatures at 161 and 165ppm. Those species are assigned to isolated K+…CO32−…H+ and Na+…CO32−…H+ carbonate species. The presence of such isolated carbonate species is interpreted as possible precursors to carbonatitic melt genesis.

Utilization of produced gas of CO2 flooding to improve oil recovery

Large amounts of mixed gas containing CO2 and hydrocarbon would be produced during CO2 flooding. Injecting the produced gas back to reservoir can not only make full use of CO2, but also can reduce air contamination. Taking produced crude oil and gases with different CO2 concentration from Jilin oilfield as examples in this paper, the phase behavior and the physical properties of live oil-gas system were measured with a visible PVT apparatus. In terms of oil viscosity reduction and swelling, the gas with high CO2 concentration was found to be substantially effective. Furthermore, comparative slim tube tests of the oil recovery performance using the five kinds of gases under different operating pressure were conducted in one-dimensional model. Results indicate that displacement efficiency increases linearly with the increasing CO2 content in the recycle gas; displacement efficiency increases with operating pressure under immiscible conditions. Re-injecting produced gas with relative high CO2 concentration back to reservoir is a method both time-saving and cost-effective.

Effect of variable CO2on eclogite-derived andesite and lherzolite reaction at 3 GPa-Implications for mantle source characteristics of alkalic ocean island basalts

We have performed reaction experiments between 1, 4, and 5 wt % CO2-bearing MORB-eclogite (recycled oceanic crust)-derived low-degree andesitic partial melt and fertile peridotite at 1375°C, 3 GPa for infiltrating melt fractions of 25% and 33% by weight. We observe that the reacted melts are alkalic with degree of alkalinity or Si undersaturation increasing with increasing CO2 content in reacting melt. Consequently, an andesite evolves through basanite to nephelinite owing to greater drawdown of SiO2 from melt and enhanced precipitation of orthopyroxene in residue. We have developed an empirical model to predict reacted melt composition as a function of reacting andesite fraction and source CO2 concentration. Using our model, we have quantified the mutual proportions of equilibrated melt from andesite-peridotite (+ CO2) hybridization and subsequent peridotite (± CO2)-derived melt required to produce the major element composition of various ocean island basalts. Our model can thus be applied to characterize the source of ocean islands from primary alkalic lava composition. Accordingly, we determined that average HIMU source requires 24 wt % of MORB-eclogite-derived melt relative to peridotite containing 2 wt % CO2 and subsequent contribution of 45% of volatile-free peridotite partial melt. We demonstrate that mantle hybridization by eclogite melt-peridotite (± CO2) reaction in the system can produce high MgO (>15 wt %) basaltic melts at mantle potential temperature (TP) of 1350°C. Therefore, currently used thermometers to estimate TP using MgO content of primary alkalic melts need to be revised, with corrections for melt-rock reaction in a heterogeneous mantle as well as presence of CO2.

Effect of Carbon Dioxide on the Reactivity of the Oxidation of Boron Particles

AbstractCarbon dioxide produced in the primary combustion of propellants apparently affects the combustion of boron. In this study, the thermodynamic and kinetic properties of the combustion of boron particles in a CO2 environment (solely or as a mixture with other gases) were investigated using thermogravimetric analyses. For the combustion of boron in an atmosphere containing 10 % oxygen, in addition to a large initial weight gain, a second increase in weight was observed when the temperature reached 1150 °C. However, when the combustion was carried out in pure CO2 atmosphere, the sample lost weight at temperatures above 1300 °C. The above results indicated that the layer of boron oxide covering the boron particles had a significant effect on the combustion process. With a limiting concentration of O2 (10 %), the initial temperature and effective activation energy slightly decreased as the content of CO2 increased from 0 to 30 %. However, a further increase in the CO2 content (50 %) increased the effective activation energy, indicating the inhibitory effects of CO2 at higher concentrations. Furthermore, the weight and the rate of weight gain gradually increased with increasing CO2 content. This behavior was attributed to the improvement in the diffusion of the oxidant. This study conclusively revealed that the inclusion of an optimal level of CO2 in a reaction environment containing O2 facilitated the combustion of boron particles.

Soil Compaction and Changes in CO<sub>2</sub> Content in Forest Stand Soil Caused by Passage of Skidding Technology

The paper was aimed on reforming on damage to soil caused by passage of universal wheeled tractors and forest wheeled tractors. We focused mainly on determining the changes in CO2 content in soil after its compaction in comparison with unimpaired soil from the stand. We carried out the measurements in municipal forests of Stará Turá, in four stands, where a regeneration felling was done. We acquired data on the depth of ruts through the method of transversal profiles took samples of soil from the ruts and unimpaired stand to determine the bulk density and moisture content. We determined the content of CO2 in stand and ruts with a Vaisala MI70 device. We selected the stands so that they would be uniform in age, terrain incline, terrain, and soil type. All of the stands had a low bearing sub – soils – flysch sandstone. This affected the rut depth after both machines passage. Rut depth indicated severe damage to the stand soil. We also observed severe differences in CO2 content of the compacted soil. Measurements in all of the stands showed a significant increase in CO2 content after its compression. Unimpaired soil reaches volume of 0.3% and rut soil reaches 1.8%. The compressed soils contained 6x the CO2 of uncompressed soils. The results of statistical analysis show, that moisture content affects the CO2 content more than bulk density. Coeficients of correlation between CO2 and moisture content were r = 0.68 and 0.52 and between CO2 and balk density were r = 0.26 and 0.36. Increase in moisture content causes CO2 accumulation. Combined effects of these two characteristics are significant and show very strong correlation. There was for example r = 0.83 and independent characteristics influenced dependent on 69%.From the outcomes the measurements we can state, that the passage of mechanisms causes significant changes in the stand soil.

Electrochemical Hydrogen Pump with SPEEK/CrPSSA Semi-Interpenetrating Polymer Network Proton Exchange Membrane for H2/CO2 Separation

The possibility of using a nonfluorinated proton exchange membrane for H2/CO2 separation in an electrochemical hydrogen pump has been evaluated for the purpose of reducing cost. A sulfonated poly(ether ether ketone) (SPEEK)/cross-linked poly(styrene sulfonic acid) (CrPSSA) semi-interpenetrating polymer network membrane exhibits a much higher proton conductivity (0.09 S cm–1 at 80 °C) and humidity sensitivity as compared with the pristine SPEEK membrane. Performance of the hydrogen pump with the sIPN membrane is investigated in different CO2 contents. The limiting currents are around 0.5–0.6 A and decrease with an increase in CO2 content, which indicates the transition of the dominant resistance from ohmic resistance to mass transport resistance. Energy efficiency of the SPEEK/CrPSSA-based hydrogen pump is around 30%, which is only slightly lower than that of the Nafion-based hydrogen pump (around 40%) reported in the literature. The results presented here suggest that a nonfluorinated membrane-based hydro...

Effect of CO2 on the Methane Combustion over a Perovskyte Catalyst at High Pressure

The effect of the CO2 content (up to 30%) on the methane catalytic combustion over a perovskyte-based monolith has been investigated at high pressure (up to 8 bar). Catalytic tests have been performed by varying the preheating temperature and the operating pressure. The CO2 adsorption over the catalytic surface has been evaluated through temperature-programmed desorption tests coupled to a kinetic model. Results show that the presence of CO2 retards ignition, shifting the ignition pressure at higher values. However, once ignition has been attained, the catalytic surface temperature increases upon an increasing CO2 content. These results have been explained by a double role of CO2: on one hand, it affects the ignition through adsorption over the catalytic surface, and on the other hand, it decreases the gas thermal diffusivity, thus reducing the velocity of heat removal from the surface.

Physical extruder foaming of poly(lactic acid)—processing and foam properties

AbstractThe article describes extrusion foaming of poly(lactic acid) (PLA) using carbon dioxide in the supercritical state as foaming agent emphasizing the steps required to establish a stable extrusion process. Low melt strength of PLA plays a role in optimizing processing conditions. The tests included PLA grades of different viscosity in addition to a chain extender. Processing at low temperature is possible due to the plasticizing effect of the CO2 on the PLA melt and a sufficiently low melt temperature is also a prerequisite in production of stable foams due to improved melt strength. Foams were characterized by density, cell structure, crystallinity, and mechanical properties in compression. Low density, microcellular foams with density down to 20–30 kg/m3 were obtained for three different PLA grades. Varying die temperature and pressure drop rate we can explain observed abrupt drops in density with increasing CO2 content by the interplay between cell nucleation and gas diffusivity at given temperatures. An effect on melt strength similar to using a chain extender is achieved by lowering the melt temperature at the die. Observed variations in sample crystallinity do not correlate with foam density. The PLA foams have good energy absorption capability. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers

Measurement and correlation of compressibility factor of high CO2-content natural gas

The JEFRI-PVT apparatus made in Canada by the Schlumberger company has been used to obtain accurate compressibility factor measurements on high CO2-content natural gasses so as to study the effect of different CO2 content on gas compressibility factor (range covered: temperature, 263.15K to 313.15K; pressure, 3MPa to 15MPa; CO2 content, 9.84, 28.86 and 50.99mol%). The results showed that gas compressibility factors reduce with increasing CO2 content in natural gasses and increase with increasing temperature. In addition, a non-integral power polynomial correlation was proposed without an iterative procedure whose coefficients were determined by fitting experimental data. The mixing rules used include: Kay's mixing rule combined with Wichert-Aziz correlations (Kay) and Stewart-Burkhardt-Voo mixing rule with Wichert-Aziz (SBV). Comparison of the DAK-SBV, DAK-Kay, and proposed correlations showed that the presented model yielded the most accurate predictions with the lowest average absolute deviation (0.42%) among them.

Electrochemical Behavior of Tubular Steel Corrosion in Brine Containing High Contents of H<sub>2</sub>S and CO<sub>2</sub>

There were little works about electrochemical corrosion behaviors that appeared in high H2S and CO2 containing environment. In this work, the electrochemical behaviors of tubular steel API-P110 in buffered acidic NaCl solutions saturated with high H2S and CO2 containing gases, were investigated by potentiodynamic sweep technique. Analysis of the results shows corrosion density declines with increasing CO2 content in H2S/CO2. The corrosion potential of steel moves towards more negatively with the increase of CO2 content in H2S/CO2. In pH 2.9 solution, Passivity appears in high H2S and CO2, but no passivity shows in due to decreasing in high H2S. In pH 5.3 solution, cathodic liming density comes out and increases with the increasing CO2 content in H2S/CO2, however, no cathodic liming density comes out in H2S.

Gas shielding in fibre laser welding of high strength pipeline steel

Pipeline welding requires mechanised high productivity welding processes to achieve the industry’s production demands. Laser welding is a high productivity process in use though there is further scope for development namely by using the recent commercialised high power fibre lasers. Shielding gas is known to have a significant influence on plasma plume characteristics during laser welding and on weld bead profile. This paper presents an analysis of fibre laser weld bead characteristics obtained with different shielding gases. The results indicate that weld profiles are affected by the shielding gas for different welding regimes. Increasing CO2 content results in higher penetrations in medium or shallow keyhole conditions, while argon is beneficial in deep penetration.

Effect of carbon dioxide on corrosion of tubular steel in high hydrogen sulfide and carbon dioxide environments

PurposeThe present work primarily aims to study the corrosion characterization of tubular steel API‐P110 in high H2S containing solution with or without CO2.Design/methodology/approachCorrosion behaviors of steel in buffered solutions containing 50 percent H2S and various levels of CO2 concentration were investigated via weight‐loss method, SEM and EDS. The effects of CO2 on corrosion occurred on the metal were analyzed by electrochemical techniques.FindingsCorrosion rates of steel decreased as the CO2 content in H2S/CO2 solution increased. It was observed for the tubular steel to experience an increase in corrosion rate at concentrations 17 percent CO2 or 34 percent CO2 in 50 percent H2S while when further increasing concentration of CO2 to 50 percent the corrosion rate decreases. Increased CO2 content in H2S/CO2 led to fewer anions desorbing and fewer reactants adsorbing, e.g. H+, H2CO3. As a result, cathodic reaction rate decreased and the amount of hydrogen absorbed decreased.Originality/valueThe experimental results showed that corrosion alleviated when increasing CO2 content in high H2S and CO2 containing environment.

Fischer–Tropsch synthesis: Effect of CO2 containing syngas over Pt promoted Co/γ-Al2O3 and K-promoted Fe catalysts

Abstract The effect of CO2 was studied for cobalt and iron Fischer–Tropsch (FT) synthesis. CO2 behaves differently in the presence of CO over cobalt and iron catalysts in terms of hydrogenation. A systematic increase of the CO2 mole fraction of carbon in the feed gas mixture alters the product distribution dramatically for cobalt FT synthesis with CO2 behaving like an inert gas at higher partial pressure of CO. With cobalt, CO appears to compete with CO2 for adsorption. Using an iron FT catalyst, hydrogenation of CO2 was effected due to the presence of the reverse water–gas shift activity of the catalyst which converts CO2 to hydrocarbons through the formation of CO. Unlike the cobalt catalyst, the product distribution was only slightly altered with increasing CO2 content in the feed gas mixture to the iron catalyst. This difference in behavior of CO2 over cobalt and iron could be attributed to the absence of reverse water–gas shift activity on cobalt and hydrogenation of CO2 to hydrocarbons—other than methane—will be derived through the formation of CO.

Electrochemical Transient Behaviors of Tubular Steel in Buffered Acidic Solution Dissolved with Hydrogen Sulfide and Carbon Dioxide

In this work, the electrochemical transient behaviors of tubular steel API-P110 in buffered acidic NaCl solutions saturated with 50% H2S and different content of CO2 mixture gases, were investigated by single potential step chronoamperometry. Analysis of the results shows that fewer reactants take part in the reduction reaction when adding CO2 content from 17% to 50% in 50% H2S containing solution. Anions desorption process controls the reactant transferring process in metal-solution interface in the solution containing H2S and CO2. When at higher overpotential, anions desorption enhances and hydrogen absorption depresses with the increasing CO2 content in H2S/CO2.

Phase behaviour of tri-n-butylmethylammonium chloride hydrates in the presence of carbon dioxide

The phase behaviour of the system water–tri-n-butylmethylammonium chloride (TBMAC)–CO2 was investigated by pressure-controlled differential scanning calorimetry in the range 0–10 mol% TBMAC in water and at CO2 pressures ranging from 0 to 1.5 MPa. In the absence of CO2, an incongruent melting hydrate, which estimated composition corresponds to TBMAC·30H2O, crystallizes at temperatures below −13.6 °C and forms with ice a peritectic phase at approximately 3.9 mol% TBMAC. In the presence of CO2 at pressures as low as 0.5 MPa, curves evidenced the presence of an additional phase exhibiting congruent melting at temperatures that are strongly pressure dependent and significantly higher than those of hydrates obtained without CO2. This new phase, whose enthalpy of dissociation and CO2 content increase slightly with CO2 pressure, was identified as a mixed semi-clathrate hydrate of TBMAC and CO2 of general formula: (TBMAC + xCO2)·30H2O.