A NEW METHOD FOR THE MEASUREMENT OF CARBON DIOXIDE IN THE EXPIRED AIR

The assessment of gas diffusion in water-saturated rocks is essential for quantifying gas loss and determining the amount of gas that could trigger abiotic and biotic processes, potentially altering fluid and rock properties. Additionally, estimating diffusion coefficients is critical for evaluating the balance between hydrogen generation and dissipation in radioactive waste repositories. This investigation involved experimental determination of diffusion coefficients for various gases both in water and in water-saturated Bentheim, Oberkirchner, Grey Weser, and Red Weser sandstones. Experimental conditions included pressures ranging from 0.2 to 1.0 MPa, consistently maintained at a temperature of 35 °C. The diffusion coefficients of hydrogen, helium, and methane in water were determined to be 6.7·10–9, 9.6·10–9, and 2.8·10–9 m2/s, respectively, consistent with literature values obtained through gas concentration measurements without pressure gradients. However, the diffusivity of carbon dioxide and argon in water was measured at 10.9·10–9 and 44.6·10–9 m2/s, significantly exceeding their corresponding literature values by an order of magnitude. This discrepancy is attributed to the significant solubility of these gases in water, resulting in density-driven convection as the primary transport mechanism. Furthermore, the effective diffusion coefficients for hydrogen within the analyzed rock specimens varied from 0.8·10–9 to 2.9·10–9 m2/s, which are higher than those for methane and carbon dioxide, both ranging from 0.3·10–9 to 0.9·10–9 m2/s. This yielded diffusive tortuosity values ranging from 2.6 to 8.2. The observed effective diffusivity values were positively correlated with porosity, permeability, and mean pore size, while exhibiting a negative correlation with tortuosity. Given that the gas–liquid mass transfer coefficient is directly proportional to the effective gas diffusivity in water, the determined values for H2 are essential for studying the impact of pore characteristics on microbial activity.

A device is described for the continuous removal of dissolved gases in water by mixing pure helium and water on a continuous-flow basis. The stripper unit has been tested by using a helium ionisation chromatograph and found satisfactory for recoveries of hydrogen, oxygen, methane, carbon monoxide and carbon dioxide at the 0·1, 0·3, 0·15, 0·18 and 0·454 ml kg–1 levels, respectively, at 18° C. For a constant helium flow-rate of 1 ml minute–1 and water flow-rates in the range 1 to 5 ml minute–1, the coefficient of variation is about 4 per cent., except for carbon monoxide and carbon dioxide. The maximum flow-rates of helium and of water are 10 ml minute–1 for this design of stripper; when the flow-rates of gas and water are equal over this greater range, the coefficient of variation indicated by the result is 10 per cent. Units consisting of several strippers fixed in a cabinet have been in routine use on experimental water loops for the past 2 years. The strippers have been operated on a continuous basis at concentrations from 0·001 to 1 ml of gas per kg of water.

Carbon dioxide (CO2), which is one of the most abundant compounds on Earth, is present in rock, the oceans and the atmosphere. CO2 influences many biological and dynamic processes. Carbon dioxide is very soluble in water due to its high dipole moment. Solubility of a gas in water is dependent upon the temperature and pressure. This dependence affects the changing content of gases in the atmosphere, and the variable effect that certain gases have on the climate. Currently, many believe that the effect of CO2 on global warming exceeds 50% of the combined effect of all greenhouse gases. CO2 is present as a gas, or can be dissolved in water, or can be found in a solid state. CO2 can also exist in a solid state as a clathrate hydrate. Gas hydrates are known as metastable minerals, whose composition and properties are determined by the source components, temperature and pressure. Knowledge of the conditions of formation, stability and decomposition of CO2 hydrate with seawater and the mass ratios of gas and water during phase transition appears quite important. In this paper, we present the results of laboratory work concerning the kinetics and morphology of a CO2 -seawater system at pressures up to 50 MPa and temperatures of 268–295 K. Measurements of CO2 solubility in supercooled seawater before and after hydrate formation are discussed. The conditions of CO2 hydrate formation and stability in seawater that is under-saturated with gas are described. The research results reveal a number of details concerning hydrate formation and dissociation, including the limits of dissolved gas in water for stable conditions of gas hydrate crystals in the water volume. Also, the information can be used to interpret the role of gas hydrates in the global changes on our planet. The results of this work permit to determine the most effective technologies to control the content of CO2 in the atmosphere. We cannot include all of our results in this paper, due to the volumes of research data generated on this subject. However, many of our most important findings have been included and discussed. General Information About The CO2 And Seawater Used In This Work The following gas and liquids were used during the experiments. Gas: Carbon dioxide (99.9% CO2 + 0.04% CH4+ 0.06% N2) Liquids: Salt (sea) water - standard laboratory mixture containing 41.953 g/L sea-salt composition (meets American Materials Standard D-1141-52 Formula A) mixed with distilled water. Table 1 presents the composition of the sea salt used to mix the synthetic seawater. The density of the seawater that we mixed in the laboratory was 1.025 g/cm3 at 15 °C. Of course, the density of seawater will depend upon the temperature, pressure and salinity of the liquid. For atmospheric pressure, the density of seawater as a function of temperature and salinity is illustrated in Figure 1 (improved, from Sea Water: Its Composition, Properties and Behavior).

Underwater photosynthesis in flooded terrestrial plants: a matter of leaf plasticity.

1. A simple kinetic method was devised to show whether dissolved CO(2) or HCO(3)- ion is the substrate in enzyme-catalysed carboxylation reactions. 2. The time-course of the reductive carboxylation of 2-oxoglutarate by NADPH, catalysed by isocitrate dehydrogenase, was studied by a sensitive fluorimetric method at pH7.3 and pH6.4, with large concentrations of substrate and coenzyme and small carbon dioxide concentrations. 3. Reaction was initiated by the addition of carbon dioxide in one of three forms: (i) as the dissolved gas in equilibrium with bicarbonate; (ii) as unbuffered bicarbonate solution; (iii) as the gas or as an unbuffered solution of the gas in water. Different progress curves were obtained in the three cases. 4. The results show that dissolved CO(2) is the primary substrate of the enzyme, and that HCO(3)- ion is at best a very poor substrate. The progress curves are in quantitative agreement with this conclusion and with the known rates of the reversible hydration of CO(2) under the conditions of the experiments. The effects of carbonic anhydrase confirm the conclusions. 5. Similar experiments on the reductive carboxylation of pyruvate catalysed by the ;malic' enzyme show that dissolved CO(2) is the primary substrate of this enzyme also. 6. The results are discussed in relation to the mechanisms of these enzymes, and the effects of pH on the reactions. 7. The advantages of the method and its possible applications to other enzymes involved in carbon dioxide metabolism are discussed.

The increase in carbon dioxide in the atmosphere is one of the main causes of global warming. Remote sensing technology has become an important means of monitoring the distribution of carbon dioxide gas. By remotely monitoring the temporal and spatial distributions of atmospheric carbon dioxide, people can further deepen their understanding of the global carbon process. The GOSAT (Greenhouse Gases Observing SATellite) CO2 L4B concentration data from 2010 to 2015 were validated using local station atmospheric data. The spatial and temporal distributions of the carbon dioxide concentration and its variation characteristics were analyzed. Based on the total primary productivity data and human emissions of carbon dioxide data, the influencing factors of spatial variations in carbon dioxide were analyzed. The results show that: (1) The correlation coefficient between GOSATL4B data and ground-measured data is above 0.95, which indicates that the remotely acquired data have high precision and stability. (2) The spatial distribution characteristics of carbon dioxide at different atmospheric pressure heights are quite different. The variation in the long-term series mean of carbon dioxide concentration levels at 17 vertical heights was studied. The fluctuations in concentration changes at different height levels vary, and the closer to the surface, the greater the fluctuation is. The near-surface carbon dioxide concentration (975 hPa) has the largest fluctuation. When the atmospheric pressure is low (for example, 150 or 100 hPa), the high carbon dioxide concentration region is banded and concentrated near the equator. The trends in carbon dioxide concentration over land and sea surfaces are similar, and the common pattern is that the concentration of carbon dioxide has been increasing. (3) The near-surface carbon dioxide concentration (975 hPa) has clearly different spatial characteristics. There are four high-value centers across the globe: East Asia, western Europe, the US East Coast, and Central Africa. The concentration of carbon dioxide in the Northern Hemisphere near the ground is higher than that in the Southern Hemisphere. The fluctuation in the Southern Hemisphere is relatively small, and the trend is opposite that in the Northern Hemisphere. (4) The concentration of carbon dioxide showed a significant growth trend during the study period. By studying the change characteristics of the monthly global average at the 975 hPa level (approximately 300 m above sea level) from January 2010 to October 2015, it can be seen that the global CO2 concentration has been above 400 ppm for most of the year, and it is increasing each year. (5) Compared with the Southern Hemisphere, the cyclical changes in carbon dioxide concentration in the Northern Hemisphere are obvious and large, while the trend in the Southern Hemisphere is relatively stable, and the change is small. There are opposite trends in the cyclical changes in the carbon dioxide concentration in the Northern and Southern Hemispheres. When the carbon concentration in the Northern Hemisphere resides over the annual high-value area, the Southern Hemisphere has a low-value area of carbon dioxide concentration every year. In addition, the change in carbon dioxide concentration during the year is obvious with seasonal changes. This should be related to changes in vegetation phenology and different seasons in the Northern and Southern Hemispheres. (6) Four countries in East Asia (Korea, Mongolia, Japan and China) from 2010 to 2014 were selected to analyze the relationship between GPP (gross primary production) and near-surface carbon dioxide concentration. These two factors have a significant inverse correlation. When carbon dioxide is at a minimum, the GPP is at its peak, and when carbon dioxide reaches its peak, the GPP reaches a minimum. The above relationship fully indicates that terrestrial ecosystems play an important role as carbon sink contributors in the carbon cycle. (7) The relationship between atmospheric carbon dioxide and carbon dioxide data from human activities from the Global Atmospheric Research Emissions Database was analyzed. The former is significantly and positively correlated with carbon dioxide emissions caused by human activities, indicating that human activities are an important factor in the increase in carbon dioxide.

The small GOR commonly measured in SAGD projects has not previously been adequately explained, and various phenomena such as "microfingering" have been proposed to account for its presence. It is shown that the production of gases can be entirely explained by gases dissolved in the produced fluids at the temperature and pressure conditions of the SAGD steam chamber. Although methane is produced in part via bitumen, there is a significant contribution from methane dissolved in water as well. Other gases, such as carbon dioxide and hydrogen sulphide, are primarily produced by virtue of their solubility in water at the pertaining temperature and pressure. This result is a consequence of the asymptotic Henry's Law behaviour of gases in water as the critical point of water is approached. This asymptotic behaviour is shown to govern at temperatures well below the critical point, and within the temperature range of SAGD steam zones. The theoretical foundation of this work permits the estimation of gas-water equilibrium constsnts for the major produced gases of importance in SAGD, and thus an ultimate understanding of gas effects in the steam zone. Introduction The production of hydrogen sulphide and carbon dioxide together with other minor gases in thermal recovery projects such as Steam Assisted Gravity Drainage is a common observation. The process giving rise to these gases is a high temperature hydrolysis of aliphatic sulphur linkages in the bitumen, dubbed "aquathermolysis" by Hyne et. al.1,2,3 Typically, the amount of hydrogen sulphide produced per tonne of bitumen varies between 6 and 75 litres. Considerably more carbon dioxide is produced, usually in the range 900-10,000 litres per tonne. However, Hyne and coworkers have not dealt with the question of whether steam or steam condensate effects these reactions, and their experiments permit no conclusions in this regard. In some of our own experiments, the procedure of Hyne et. al. was changed in that a stainless steel reaction vessel was used. In order to avoid loss of hydrogen sulphide to the steel, it was necessary to suppress the hydrogen sulphide in the gas phase. The experiment was arranged such that the reaction vessel was completely filled to eliminate a headspace, and an overpressure of 50,000 kPa was applied by means of helium gas. Thus, while Hyne's experiments at 240 °C were conducted at the steam saturation pressure of approximately 3500 kPa, in our case a gas phase was effectively prevented from forming. Our results were within the range reported by Hyne, suggesting strongly that the steam condensate rather than steam itself is the reagent in the aquathermolysis. The question thus arises about the location within the steam zone where this reaction occurs. Elementary considerations of chemical kinetics would suggest that the steam front and the fluid drainage zone are the only regions of the SAGD steam chamber where the reaction is possible, these being the only regions where both steam condensate and bitumen are present in high saturations.

The small gas/oil ratio (GOR) commonly measured in SAGD projects has not previously been adequately explained, and various phenomena such as "microfingering" have been proposed to account for its presence. It is shown that the production of gases can be entirely explained by gases dissolved in the produced fluids at the temperature and pressure conditions of the SAGD steam chamber. Although methane is produced, in part, via bitumen, there is a significant contribution from methane dissolved in water as well. Other gases, such as carbon dioxide and hydrogen sulphide, are primarily produced by virtue of their solubility in water at the pertaining temperature and pressure. This result is a consequence of the asymptotic Henry's Law behaviour of gases in water as the critical point of water is approached. This asymptotic behaviour is shown to govern at temperatures well below the critical point, and within the temperature range of SAGD steam zones. The theoretical foundation of this work permits the estimation of gas-water equilibrium constants for the major produced gases of importance in SAGD, and thus an ultimate understanding of gas effects in the steam zone. Introduction The production of hydrogen sulphide and carbon dioxide, together with other minor gases in thermal recovery processes such as Steam Assisted Gravity Drainage (SAGD), is a common observation. The process that gives rise to these gases is a high temperature hydrolysis of aliphatic sulphur linkages in the bitumen, dubbed "aquathermolysis" by Hyne et al.(1–3) Typically, the amount of hydrogen sulphide produced per tonne of bitumen varies between six and 75 l. Considerably more carbon dioxide is produced, usually in the range 900 - 10,000 l per tonne. However, Hyne and co-workers have not dealt with the question of whether steam or steam condensate affects these reactions, and their experiments permit no conclusions in this regard. In some of our own experiments, the procedure of Hyne et al. was changed in that a stainless steel reaction vessel was used. In order to avoid loss of hydrogen sulphide to the steel, it was necessary to suppress the hydrogen sulphide in the gas phase. The experiment was arranged such that the reaction vessel was completely filled to eliminate a headspace, and an overpressure of 50,000 kPa was applied by means of helium gas. Thus, while Hyne's experiments at 240 °CDATA [C were conducted at the steam saturation saturation pressure of approximately 3,500 kPa, in our case, a gas phase was effectively prevented from forming. Our results were within the range reported by Hyne, suggesting strongly that the steam condensate, rather than the steam itself, is the reagent in the aquathermolysis. The question thus arises about the location within the steam zone where this reaction occurs. Elementary considerations of chemical kinetics would suggest that the steam front and the fluid drainage zone are the only regions of the SAGD steam chamber where the reaction is possible, these being the only regions where both steam condensate and bitumen are present in high saturations.

(1) In general, the changes in pH were similar to those observed in previous years. On six occasions the pH at the surface at Station L4 was lower than at the bottom. (2) The changes in carbon dioxide in the spring agree with the conclusion, formed in Part I from nutrient salt data, that the early start in plant production in mid-Channel was not maintained and that by the middle of April production had become much greater nearer the shore. (3) The partial pressure of CO2 during nine months out of twelve has been observed to be lower than that of the atmosphere and equal or slightly higher during the remaining three months. (4) It is suggested that the fall in (Total CO2+O2) during the course of the summer was due mostly to loss of oxygen to the atmosphere. After allowing for carbon dioxide possibly removed from the sea as calcium carbonate and for the loss of oxygen due solely to rising temperature of the water, a net loss of 110 litres of oxygen was found from a column 1 sq. metre in cross-section and 70 metres deep; or 9 cubic kilometres from the whole of the Channel. If this is regarded as a closed system, the oxygen must have been formed during photosynthesis from an equal volume of CO2 dissolved from the atmosphere. But the required transfer of CO2 across the surface of the sea is too great to be accounted for by existing data on the rate of invasion of CO2 into sea-water as calculated for a small bubble of gas in water. (5) Estimates of the phytoplankton crop have been made, based on the seasonal consumption of carbon dioxide, of phosphate and of nitrate and on the oxygen lost to the atmosphere. All four are of the order of 1,400 metric tons wet weight per sq. km. of surface, in close agreement with the figure calculated by Atkins. The crop production calculated from consumption of silicate is less than one-tenth of this. This is attributed not only to the presence of planktonic organisms requiring no silica but to the silicate being used several times over in the course of the season. (6) About 0·06% of the wet weight of phytoplankton produced is harvested as fish. (7) A small variation in excess base, equivalent to about 0-1% of the total calcium present, has been detected between the surface and bottom in summer. The result requires confirmation.

A review on the application of carbonated water injection for EOR purposes: Opportunities and challenges

Water was bubbled with gases including nitrogen (N2 ), oxygen (O2 ), hydrogen (H2 ), carbon dioxide (CO2 ), and air for 10 min and phenolics from green tea leaves were extracted using the prepared gas-bubbled water. To retain the gases in water, the extraction conditions were maintained in an air-tight container at room temperature under magnetic stirring. Radical scavenging ability, total phenolic content, and phenolic profiles of the extracts were analyzed, and gas-bubbled water was examined to explain the differences in phenolic contents. Overall, green tea infusion prepared from H2 -bubbled water contained significantly high levels of total phenolic compounds and antioxidant activity compared to other gas-bubbled waters including N2 , O2 , CO2 , and air (P < 0.05).Control samples and those bubbled with CO2 showed the lowest antioxidant activities in green tea infusion. However, green tea extracts with O2 bubbling showed the lowest catechin content. Green tea leaves treated with hydrogen gas-bubbled water had much greater damage to their surface morphological properties compared to the other groups, which may explain the higher yield of phenolic compounds. Overall, hydrogen gas-bubbled water showed better extraction yield of phenolics from green tea leaves than other gas-bubbled water. PRACTICAL APPLICATION: Green tea or green tea infusion has diverse health beneficial functionality due to the presence of phenolic compounds. In this study, different gases including nitrogen, oxygen, hydrogen, and carbon dioxide were treated in water and these gas-bubbled water were used to extract phenolics from green tea leaves. Among them, hydrogen-bubbled water extracted the highest phenolic contents from tea leaves and showed the highest in vitro antioxidant ability in green tea infusion compared to other gas-bubbled water. This new knowledge could help to produce green teas with higher antioxidant activity in beverage industry.

The partial molal volumes of nitrogen, oxygen, and carbon dioxide in water at 0 °C have been determined by a new technique based on the use of a Gilfillan-Polanyi micro-pyknometer as a float. The value obtained for nitrogen is 37.0 ml and that for oxygen, 31 ml. The value for carbon dioxide is found to vary from 44 to 28 ml as the pressure at which the water is saturated with the carbon dioxide varies from 0 to 6 cm Hg. The changes in the density of water at 0 °C produced by saturation with nitrogen, oxygen, and air at 1 atm pressure are -9.3, + 1.8, and -4.7 p.p.m. respectively. The density of air-saturated water is considerably greater than would be expected from the sum of the effects due to nitrogen and oxygen separately.

Vacuum degasifier:: comprehensive modelling and simulation

95/00888 Influence of low-frequency electromagnetic fields on living organisms

In recent years, substantial progress has been made in the theoretical treatment of hydrocarbon dissolution in water, near the critical point of water (374 °C). At these temperatures, water becomes a solvent for gases including the lower hydrocarbons, and possibly, the higher hydrocarbons. The SAGD process is currently the only viable method for in situ recovery of Canada's Athabasca oil sands deposit, a deposit of high viscosity oil in unconsolidated sand. Recent studies have sought to understand modifications at lower steam pressures and gas injection. Most recently, the idea of solvent co-injection has been under discussion. In the present paper, the predictive capabilities that have been developed for gas production in the SAGD process are studied in conjunction with the chemical kinetics and mechanisms of solvolytic reactions. The reactions that produce hydrogen sulphide and carbon dioxide, generally referred to by the name "aquathermolysis, are thought to be solvolytic reactions by their nature. The results of this work suggest strongly that the production of the acid gases, hydrogen sulphide, and carbon dioxide will be suppressed in SAGD operations if a solvent is co-injected. The work has implications for the need for sulphur recovery plants in SAGD projects that are considered for solvent co-injection. Recently published thermodynamic data have made possible the prediction of individual solvent component production or retention in the steam zone. Introduction In 2001, Thimm(1) proposed that gas production in SAGD proceeds via a dissolution mechanism. Gases are dissolved in the produced liquids, and break out of solution in the wellbore and facilities. There has been no case reported so far where it is necessary to assume free gas production in SAGD in order to account for observed gas production or composition. The rationale is as follows. The distribution coefficient (K-value) of a solute gas in equilibrium with a solvent is given by: Equation (Available In Full Paper) In this form, the unit of the Henry's Law coefficient is that of pressure, as is evident from inspection. For the purpose of this work, all Henry's Law constants are given in units of MPa. The equation shows that the K-values are related to the Henry's Law constant. Determination of Henry's Law Constants Henry's Law coefficients for gases in water normally follow a power law known as the Valentiner Equation: Equation (Available In Full Paper) However, at elevated temperatures, this equation begins to fail at about 175 °C, and could only be used for the lowest steam pressure situations. Above this temperature, deviations become progressively larger, because an asymptotic behaviour of the Henry's Law constant near the critical point of water makes an increasingly important contribution. Above 175 °C, the specific volume of water begins to fall significantly from the normal 55.56 mole/L, and Harvey and Levelt Sengers(2) have shown a linear relationship between: Equation (Available In Full Paper) in the range 175 °C and the critical point of water at 374 °C. For small, non-polar molecules and noble gases, Harvey and Levelt Sengers(2) have shown that the use of the equation: Over the last 25 years there have been a number of reports in the literature of planned or executed field tests of the electric heating process, mostly based on the ohmic dissipation of electric energy in the formation. Electrothermic Co., for example, stimulated four wells of the Little Tom field in South Texas