Adding Carbon Dioxide Research Articles

An experimental study of methane–oxygen–carbon dioxide premixed flame dynamics in non-adiabatic cylinderical meso-scale reactors with the backward facing step

In the present study, we experimentally evaluated the effects of geometrical parameters, Reynolds number, dilution percent, and equivalence ratio on methane–oxygen–carbon dioxide flame dynamics in non-adiabatic cylindrical meso-scale reactors with the backward facing step. Five flame regimes of blow-out, marginal, stationary (asymmetric and spinning), RERI, and flashback were observed during the tests. The results showed that adding carbon dioxide to methane–oxygen mixture could extend RERI flame regimes in the meso-scale reactors. Moreover, it was shown that the presence of RERI flame regime could lead to more uniform temperature distribution on the outer surface of the lengthy meso-scale reactors as compared to the stationary flame regimes. Also, it was demonstrated that increasing the average flow speed in the meso-scale reactors decreased the average frequency of RERI flame regimes.

Diffusion Flame Stability of Low Calorific Fuels

Mechanisms related to diffusion flame stabilization have been the subject of several studies within the last decades due the industrial and scientific interests. Information on flame stability is of fundamental importance in energy efficiency and safety regarding industrial applications. Thus, an experimental study was performed in order to examine the flame characteristics and regions of stability limits. In this study, a representative burner of industrial applications was employed, which allows the stabilization of several combustion regimes. The lift-off and blow-out flame regimes were investigated for different proportions of carbon dioxide in natural gas. In this way, an analysis of the calorific fuel influence on the flame stability was performed based on the measurements and a comparison with classical literature models was done. The fuel dilution by adding carbon dioxide was found to decrease the soot production, leading to lower flame heights and also, lower lift-off and blow-out limits. Results obtained from this study encourage future works which consider flames in large scale, in order to equate to industrial applications.

Enhancing the efficacy of electrolytic chlorination for ballast water treatment by adding carbon dioxide

We examined the synergistic effects of CO2 injection on electro-chlorination in disinfection of plankton and bacteria in simulated ballast water. Chlorination was performed at dosages of 4 and 6ppm with and without CO2 injection on electro-chlorination. Testing was performed in both seawater and brackish water quality as defined by IMO G8 guidelines. CO2 injection notably decreased from the control the number of Artemia franciscana, a brine shrimp, surviving during a 5-day post-treatment incubation (1.8 and 2.3 log10 reduction in seawater and brackish water, respectively at 6ppm TRO+CO2) compared with water electro-chlorinated only (1.2 and 1.3 log10 reduction in seawater and brackish water, respectively at 6ppm TRO). The phytoplankton Tetraselmis suecica, was completely disinfected with no live cell found at >4ppm TRO with and without CO2 addition. The effects of CO2 addition on heterotrophic bacterial growth was not different from electro-chlorination only. Total residual oxidant concentration (TRO) more rapidly declined in electro-chlorination of both marine and brackish waters compared to chlorine+CO2 treated waters, with significantly higher amount of TRO being left in waters treated with the CO2 addition. Total concentration of trihalomethanes (THMs) and haloacetic acids (HAAs) measured at day 0 in brackish water test were found to be 2- to 3-fold higher in 6ppm TRO+CO2-treated water than in 6ppm TRO treated water. The addition of CO2 to electro-chlorination may improve the efficiency of this sterilizing treatment of ballast water, yet the increased production of some disinfection byproducts needs further study.

Waiting with bated breath: opportunistic orientation to human odor in the malaria mosquito, Anopheles gambiae, is modulated by minute changes in carbon dioxide concentration.

Females of the malaria mosquito, Anopheles gambiae, predominantly obtain blood meals within human dwellings. Being highly anthropophilic, human skin odor offers a reliable, host-specific cue, but the challenge posed by pervasive human odor found indoors from used clothing, bedding etc. remains unclear. Anopheles gambiae spends much of its adult life indoors, constantly exposed to human odor even when dwellings are unoccupied. In landing assays, we found that female mosquitoes respond very weakly to human skin odor alone, suggesting that, alone, it is an ineffective landing cue. Landing, however, was dramatically increased by addition of carbon dioxide at a range of concentrations above ambient. Indeed, this effect was seen even when carbon dioxide was just 0.015% above ambient within the assay cage. The synergistic effect of added carbon dioxide quickly waned, thereby facilitating a highly adaptive "sit-and-wait" ambush strategy, wherein females ignore persistent human odor until a living human is present. Unexpectedly, landing rates in the presence of added carbon dioxide were almost as robust during daytime, when An. gambiae has previously been assumed inactive, possibly facilitating opportunistic feeding at times of day when human dwellings are occupied intermittently. We suggest earlier studies that showed strong upwind flight behavior toward human odor alone could, in fact, have been demonstrating orientation toward a human dwelling rather than toward a living human. This new interpretation of how human odors mediate upwind orientation and landing in An. gambiae is discussed.

CO2 Enrichment at Night Affects the Growth and Yield of Common Beans

ABSTRACTMany experiments to determine the crop yield increase expected with rising atmospheric carbon dioxide concentration added carbon dioxide only during the daytime, without tests of whether elevation of carbon dioxide at night affected plant growth. In this experiment, two cultivars of common bean (Phaseolus vulgaris L.) were grown in the field for 4 yr in open‐top chambers in which CO2 was added during the day or the night, both day and night, or not at all. CO2 was added to increase the concentration by 180 μmol mol−1 above that of the ambient outside air, which averaged 392 μmol mol−1 during the daytime and 503 μmol mol−1 at night. In the two cultivars, the average increase in seed yield above the ambient CO2 treatment was 42% with daytime CO2 enrichment and 77% with continuous enrichment. In both cultivars, continuous CO2 enrichment increased the area of individual leaflets by about 40% compared with daytime enrichment. Leaflet size was the same with daytime CO2 enrichment and with no enrichment. In one of the cultivars, nighttime CO2 elevation alone increased leaflet size and seed yield. The results indicated that CO2 enrichment at night had important consequences for the growth and yield of these bean cultivars, and that daytime‐only CO2 enrichment greatly underestimated the yield increase likely to occur with rising atmospheric CO2 concentrations.

Numerical and experimental study of soot formation in laminar diffusion flames burning simulated biogas fuels at elevated pressures

The effects of pressure and composition on the sooting characteristics and flame structure of laminar diffusion flames were investigated. Flames with pure methane and two different methane-based, biogas-like fuels were examined using both experimental and numerical techniques over pressures ranging from 1 to 20atm. The two simulated biogases were mixtures of methane and carbon dioxide with either 20% or 40% carbon dioxide by volume. In all cases, the methane flow rate was held constant at 0.55mg/s to enable a fair comparison of sooting characteristics. Measurements for the soot volume fraction and temperature within the flame envelope were obtained using the spectral soot emission technique. Computations were performed by solving the unmodified and fully-coupled equations governing reactive, compressible flows, which included complex chemistry, detailed radiation heat transfer and soot formation/oxidation. Overall, the numerical simulations correctly predicted many of the observed trends with pressure and fuel composition. For all of the fuels, increasing pressure caused the flames to narrow and soot concentrations to increase while flame height remained unaltered. All fuels exhibited a similar power-law dependence of the maximum carbon conversion on pressure that weakened as pressure was increased. Adding carbon dioxide to the methane fuel stream did not significantly effect the shape of the flame at any pressure; although, dilution decreased the diameter slightly at 1atm. Dilution suppressed soot formation at all pressures considered, and this suppression effect varied linearly with CO2 concentration. The suppression effect was also larger at lower pressures. This observed linear relationship between soot suppression and the amount of CO2 dilution was largely attributed to the effects of dilution on chemical reaction rates, since the predicted maximum magnitudes of soot production and oxidation also varied linearly with dilution.

Controlled electrochemical carboxylation of graphene to create a versatile chemical platform for further functionalization.

An electrochemical approach is introduced for the versatile carboxylation of multi-layered graphene in 0.1 M Bu4NBF4/MeCN. First, the graphene substrate (i.e., graphene chemically vapor-deposited on Ni) is negatively charged at -1.9 V versus Ag/AgI in a degassed solution to allow for intercalation of Bu4N(+) and, thereby, separation of the individual graphene sheets. In the next step, the strongly activated and nucleophilic graphene is allowed to react with added carbon dioxide in an addition reaction, introducing carboxylate groups stabilized by Bu4N(+) already present. This procedure may be carried out repetitively to further enhance the carboxylation degree under controlled conditions. Encouragingly, the same degree of control is even attainable, if the intercalation and carboxylation is carried out simultaneously in a one-step procedure, consisting of simply electrolyzing in a CO2-saturated solution at the graphene electrode for a given time. The same functionalization degree is obtained for all multi-layered regions, independent of the number of graphene sheets, which is due to the fact that the entire graphene structure is opened in response to the intercalation of Bu4N(+). Hence, this electrochemical method offers a versatile procedure to make all graphene sheets in a multi-layered but expanded structure accessible for functionalization. On a more general level, this approach will provide a versatile way of forming new hybrid materials based on intimate bond coupling to graphene via carboxylate groups.

Effects of Carbonation on Probiotic Survivability, Physicochemical, and Sensory Properties of Milk‐Based Symbiotic Beverages

Drinkable yogurt is a popular beverage in the United States and there may be a niche for carbonated drinkable yogurt in the functional foods market. Pomegranate (P) and vanilla (V) yogurt beverages were formulated, containing inulin as a prebiotic, along with probiotic bacteria Lactobacillus acidophilus and Bifidobacterium, to produce symbiotic products. These beverages were stabilized with high-methoxyl pectin and whey protein concentrate and compared to samples with approximately 2 volumes of added carbon dioxide (CO2 ). Samples were stored in sealed glass bottles at 4 °C for 9 wk for evaluation of physicochemical and functional properties. Trials were carried out in triplicate and 3 replicates from each trial were analyzed. Physicochemical attributes were analyzed using standard AOAC methods. Survivability of the probiotics and changes in pH and viscosity were measured weekly. Chemical composition of the carbonated beverages was: protein: 1.58 ± 0.05%, 1.59 ± 0.06%, fat: 1.24 ± 0.2%, 1.18 ± 0.11%, total solids: 14.78 ± 0.11%, 14.93 ± 0.05%, ash: 0.49 ± 0.02%, 0.46 ± 0.03%, and carbohydrate (by difference): 11.47 ± 0.12%, 11.69 ± 0.14% for P and V, respectively. Both L. acidophilus and Bifidobacterium were stable and remained above 10(6) CFU/g for both flavors of beverage both with and without carbonation. The new manufacturing technology for these prototypes may have potential for commercialization of carbonated symbiotic milk-based beverages.

Sleeping position and responses to a carbon dioxide challenge in convalescent prematurely born infants studied post-term

ObjectivesTo test the hypothesis that the ventilatory response to a carbon dioxide (CO2) challenge would be lower in the prone compared to the supine position in prematurely born infants studied...

Effects of pressure and carbon dioxide, hydrogen and nitrogen concentration on laminar burning velocities and NO formation of methane-air mixtures

We studied the effects of increasing pressure and adding carbon dioxide, hydrogen and nitrogen to Methane-air mixture on premixed laminar burning velocity and NO formation in experimentally and numerically methods. Equivalence ratio was considered within 0.7 to 1.3 for initial pressure between 0.1 to 0.5 MPa and initial temperature was separately considered 298 K. Mole fractions of carbon dioxide, hydrogen and nitrogen were regarded in mixture from 0 to 0.2. Heat flux method was used for measurement of burning velocities of Methane-air mixtures diluted with CO2 and N2. Experimental results were compared to the calculations using a detailed chemical kinetic scheme (GRI-MECH 3.0). The results in atmosphere pressure for Methane-air mixture were calculated and compared with the results of literature. Results were in good agreement with published data in the literature. Then, by adding carbon dioxide and nitrogen to Methaneair mixture, we witnessed that laminar burning velocity was decreased, whereas by increasing hydrogen, the laminar burning velocity was increased. Finally, the results showed that by increasing the pressure, the premixed laminar burning velocity decreased for all mixtures, and NO formation indicates considerable increase, whereas the laminar flame thickness decreases.

Starch and ICUMSA color removal in sugarcane juice clarified by carbonatation

The manufacture of sugar with sulfur dioxide during the clarification process faces market difficulties and rejection by consumers who are more and more concerned on food safety. The alternative may be sugar clarification with carbon dioxide which consists in adding carbon dioxide and calcium hydroxide to sugar juice at constant pH. Under these conditions, a calcium carbonate complex is formed which adsorbs and precipitates impurities. Current assay analyzes the clarification of sugarcane juice in a laboratory carbonatation process. Assays were performed randomly with a two-level factorial design with three replications at the center point to evaluate the effect of pH and carbon dioxide flow in clarification. Process efficiency was assessed according to rates of starch removal, ICUMSA color and calcium left in the juice. Rates of starch removal at 89.19 and 85.75% and of ICUMSA color at 92.93 and 91.66% were obtained, respectively, in assays with carbon dioxide flow at 200 NL h -1 and pH at 8.0 and 9.0. Results show

Operational Strategies for Lab scale Horizontal Tubular Photobioreactor for Mitigation of CO2 Using an Indigenous Thermophilic Microalgal Strain Geitlerinema sulphureum

Anthropogenic activities leading to the industrial revolution have contributed substantially to climate change by adding carbon dioxide (CO2) into the atmosphere which has caused a gradual but significant increase in the atmospheric temperature through the years. Part of the efforts to mitigate CO2 involves the capture and sequestration using microalgae. Efforts were made in KET’s VG Vaze College to screen indigenously isolated thermophilic cyanobacteria for this purpose. High temperature adaptability (42oC), high CO2 tolerance (23.08%), reasonably high biomass production and easy harvesting made G. sulphureum a promising candidate for the CO2 sequestration in the tropical climatic conditions. The present communication deals with the optimisation of productivity of G. sulphureum in a lab scale tubular photobioreactor by altering paramters such as light regime, CO2 supplementation, and nitrate and carbon source optimisation. The baseline productivity was 0.035 g/Lday before optimisation. In case of the cumulatively optimised productivity, it increased to 0.094 g/Lday with the highest reported biomass concentration of 1.29 g/L.

FINAL CHLORINE DIOXIDE STAGE AT NEAR-NEUTRAL pH FOR BLEACHING EUCALYPTUS PULP

It is well known that pH is an important parameter for controlling the eucalyptus pulp bleaching when using the final chlorine dioxide stage, since it affects the effectiveness of the process. Recommendations found in the literature for operating are in the 3.5 to 4.0 range. However, in this paper it was shown that final chlorine dioxide has better performance, with significant brightness gain while also preserving pulp quality, when it is operated at near neutral pH. This result can be explained by the generation of sodium bicarbonate in situ upon adding carbon dioxide at this stage.

Solubility measurements of hydrogen in 1-butyl-3-methylimidazolium tetrafluoroborate and the effect of carbon dioxide and a selected catalyst on the hydrogen solubility in the ionic liquid

The high pressure phase behavior of a binary mixture containing hydrogen (H2) and 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]) is studied by measuring bubble-point pressures at different temperatures for three compositions with hydrogen mole fractions of 5, 7.5 and 10mol%. Since this work is part of a study to design a hydrogenation process, using [bmim][BF4] as the reaction medium, the effects of adding carbon dioxide (CO2) or the hydrogenation catalyst (−)-1,2-bis((2R,5R)-2,5-dimethylphospholano)benzene (cyclooctadiene)rhodium(I) tetrafluoroborate (Rh-MeDuPHOS) on H2 solubility in [bmim][BF4] was measured as well. All measurements were conducted in an autoclave set-up, allowing pressures up to 60MPa and temperatures ranging from 313.15 up to 368.15K.Results indicated that the presence of catalyst increased the H2 solubility in [bmim][BF4] compared to those of binary mixtures of H2+[bmim][BF4] throughout the whole temperature range studied. However, the addition of CO2 to the binary system of H2+[bmim][BF4] increases the H2 solubility at lower temperatures (<330K), and decreases it at higher temperatures (>340K).

PHYSICO-CHEMICAL, MICROBIOLOGICAL AND PHARMACOLOGICAL STABILITY OF THERAPEUTIC MINERAL WATERS

Introduction: For a natural mineral water to be bottled and then sold as table water, besides some physicochemical characteristics that define it, must come from a natural source (spring, well, borehole) with a high purity biological and microbiology. Most chemical compounds, expressed major elements, trace elements, gases, some undissociated compounds closely correlated with water temperature and pH they have a role in assessing qualitative characterization and classification of mineral waters. Variety composition of mineral water generated their many uses in both the therapeutic and the water table. Physico-chemical composition and microbiological indicators values for drinking must belong to a high degree of stability for certain periods of time. Degree of physical and chemical stability of mineral waters in general is closely related to chemical equilibrium achieved naturally when water does not undergo any transformation (being bottled just by adding carbon dioxide), or may undergo significant changes technological processes (deferizare, desulfurization, degassing, etc.). Use bottled mineral water is provided in the form of national and international rules that limit technological operations and treatments that could influence the initial natural features. For this purpose were admitted as necessary to ensure stability operations only bottled mineral water deferizarea and impregnation with carbon dioxide. Objectives: LIAMNT lab has pursued stability physicochemical, microbiological and pharmacodynamics over a period of 6 months or 1 year of several types of bottled mineral water (oligomineral water, carbonated water, sulfur water, etc).

Using hydrogeology to identify the source of groundwater to Montezuma Well, a natural spring in Central Arizona, USA: part 1

Montezuma Well is a natural spring located within a “sinkhole” in the desert environment of the Verde Valley in Central Arizona. It is managed by the National Park Service as part of Montezuma Castle National Monument. Because of increasing development of groundwater in the area, this research was undertaken to better understand the sources of groundwater to Montezuma Well. The use of well logs and geophysics provides details on the geology in the area around Montezuma Well. This includes characterizing the extent and position of a basalt dike that intruded a deep fracture zone. This low permeability barrier forces groundwater to the surface at the Montezuma Well “pool” with sufficient velocity to entrain sand-sized particles from underlying bedrock. Permeable fractures along and above the basalt dike provide conduits that carry deep sourced carbon dioxide to the surface, which can dissolve carbonate minerals along the transport path in response to the added carbon dioxide. At the ground surface, CO2 degasses, depositing travertine. Geologic cross sections, rock geochemistry, and semi-quantitative groundwater flow modeling provide a hydrogeologic framework that indicates groundwater flow through a karstic limestone at depth (Redwall Limestone) as the most significant source of groundwater to Montezuma Well. Additional groundwater flow from the overlying formations (Verde Formation and Permian Sandstones) is a possibility, but significant flow from these units is not indicated.

The effects of carbon dioxide addition to cheese milk on the microbiological properties of Turkish White brined cheese

This study invest0igated the effect of CO2 added to achieve three pH levels: pH 6.1, pH 6.2 and pH 6.3 for treatments X, Y, Z, respectively, on some microbiological properties of Turkish White (TW) brined cheese. For each pH, four batches of cheese were produced from: raw milk with no added carbon dioxide (UR), raw milk with carbon dioxide (TR), pasteurised milk with no carbon dioxide addition (UP) and pasteurised milk with carbon dioxide addition (TP). The microbiological analysis of TW brined cheeses was carried out for 90 days of maturation period. Total aerobic mesophilic bacteria, mesophilic lactic acid bacteria, yeasts and moulds and coliform group were determined in control and CO2 treatment groups. Mesophilic bacteria count was determined as 5.14, 5.29, 5.67 log cfu/g for pH 6.1, 6.2 and 6.3, respectively, in CO2‐treated raw milk cheeses. Yeasts and moulds reduction increased significantly by applying CO2 (P &lt; 0.01). For TW cheese samples, the most significant microbial inactivation was detected at sample groups of pH 6.1.

“Inexhaustible” source of hydrogen may be unlocked by salt water

A grain of salt or two may be all that microbial electrolysis cells need to produce hydrogen from wastewater or organic by-products, without adding carbon dioxide to the atmosphere or using grid electricity, according to engineers in the USA at The Pennsylvania State University.

Effect of carbon dioxide and nitrogen on the diffusivity of methane confined in nano-porous carbon aerogel

The microscopic diffusivity of methane (CH 4) confined in nano-porous carbon aerogel was investigated as a function of added carbon dioxide (CO 2) and nitrogen (N 2) pressure using quasi-elastic neutron scattering (QENS). In the range of the external pressure of 1–2.5 MPa, the self-diffusivity of methane was found to increase with CO 2 pressure and remain practically unchanged in the N 2 environment. Increasing mobility of methane with CO 2 pressure suggests that the adsorbed CH 4 molecules become gradually replaced by CO 2 on the surface of carbon aerogel pores, whereas the presence of N 2 does not induce the replacement. The molecular mobility of the methane, with or without added carbon dioxide and nitrogen, is described by the unrestricted diffusion model, which is characteristic of methane compressed in small pores. On the other hand, both nitrogen and carbon dioxide molecules in carbon aerogel, when studied alone, with no methane present, follow a jump diffusion process, characteristic of the molecular mobility in the densified adsorbed layers on the surface of the aerogel pores.

Enhanced fluidity liquid chromatography for hydrophilic interaction separation of nucleosides

The application of enhanced fluidity liquid (EFL) mobile phases to improving isocratic chromatographic separation of nucleosides in hydrophilic interaction liquid chromatography (HILIC) mode is described. The EFL mobile phase was created by adding carbon dioxide to a methanol/buffer solution. Previous work has shown that EFL mobile phases typically increase the efficiency and the speed of the separation. Herein, an increase in resolution with the addition of carbon dioxide is also observed. This increase in resolution was achieved through increased selectivity and retention with minimal change in separation efficiency. The addition of CO 2 to the mobile phase effectively decreases its polarity, thereby promoting retention in HILIC. Conventional organic solvents of similar nonpolar nature cannot be used to achieve similar results because they are not miscible with methanol and water. The separation of nucleosides with methanol/aqueous buffer/CO 2 mobile phases was also compared to that using acetonitrile/buffer mobile phases. A marked decrease in the necessary separation time was noted for methanol/aqueous buffer/CO 2 mobile phases compared to acetonitrile/buffer mobile phases. There was also an unusual reversal in the elution order of uridine and adenosine when CO 2 was included in the mobile phase.