Sorption and surface flow in graphitized carbon membranes - I. The steady state

1967 ◽  
Vol 299 (1459) ◽  
pp. 434-454 ◽  
Keyword(s):  
Gas Phase ◽  
Diffusion Coefficients ◽  
Surface Flow ◽  
Inert Gases ◽  
Sulphur Hexafluoride ◽  
Carbon Membranes ◽  
Carbon Particles ◽  
Influence Of Temperature On ◽  
Pass Through ◽  
The Individual

A study has been made of the flow of inert gases and of sulphur hexafluoride through, and of the adsorption of argon and sulphur hexafluoride on, two carbons chosen for the energetic homogeneity of the sorbing surfaces and non-porosity of the individual carbon particles. A wide temperature range has been covered, ‘surface’ and ‘gas phase’ flows of the sorbed gases have been measured using helium as non-sorbed calibrating gas, and the corresponding permeability and diffusion coefficients derived. The smooth, non-porous sorbents chosen were able to produce extra flows considerably greater than those on much larger but porous and broken surfaces of some other sorbents (e. g. active carbons and alumina-silica cracking catalyst). The concentration dependence of the surface diffusion coefficients, D ss , agrees with a treatment of this dependence according to which, in the regime when gas phase diffusion coefficients are independent of pressure, D ss varies inversely as the slope of the isotherm. When fluxes at each of a series of pressures are plotted against temperature, the fluxes pass through maxima as the temperature is lowered. This behaviour can be explained in terms of the simultaneous influence of temperature on D ss and on the concentration gradients.

Isothermal and thermo-osmotic transport of sorbable gases in microporous carbon membranes

1973 ◽  
Vol 275 (1249) ◽  
pp. 255-307 ◽  
Keyword(s):  
Steady State ◽  
Carbon Black ◽  
Gas Phase ◽  
Diffusion Coefficients ◽  
Linear Relation ◽  
Microporous Carbon ◽  
Adsorbed Molecules ◽  
Carbon Membranes ◽  
Adsorbed Films ◽  
Absolute Adsorption

With the use of helium and a series of gases adsorbed to give dilute films, measurements have been made of thermo-osmotic steady-state pressure ratios established across microporous carbon membranes through which linear temperature gradients were maintained. Two contrasting adsorbents were employed: Carbolac I, a carbon black having an energetically heterogeneous high area surface and Graphon, a graphitized carbon black of one-tenth the surface area of Carbolac but energetically homogeneous. Complementary studies of isothermal transport of the gases through the membranes and determination of equilibrium adsorption isotherms at all temperatures employed for the flow experiments were required in order to analyse the non-isothermal experimental results. Part I is concerned with the equilibrium properties of the adsorbed films. Henry’s law constants, k, energies of adsorption, A E'and isosteric heats of adsorption, for the Gibbs excess adsorption were derived from the experimental isotherms. Taking the thickness of the adsorbed layer as one molecular diameter, the corresponding energies, A E,and heats qBt for absolute adsorption have been calculated. For the very dilute films the ratios AE'jAE and q'BtlqBt can differ appreciably from unity. Also in the Henry law range, values of the thermodynamic equilibrium constants and standard energies, AE&, and entropies, A for absolute adsorption have been evaluated. A linear relation between AS& and AE&, was observed. — A was considerably larger on Carbolac than on Graphon surfaces. This has been interpreted in terms of greater mobility of the adsorbed molecules on the more homogeneous Graphon surface. Good correlations have been found between K or A Eand properties, such as polarizability, a, related to the condensability of the sorbates. Part II is concerned with isothermal transport of the gases through the membranes. For the majority of systems studied the permeability, K and time-lag, L, were independent of pressure. For helium in both membranes the ratio K/^T was independent of temperature and pressure, indicating transport only in the gas phase and the absence of a viscous flow component. For an adsorbed gas the extra flux generated by the mobile adsorbed films per unit area of surface, JJA, were considerably greater for the more homogeneous Graphon membrane. Diffusion coefficients associated with the extra fluxes also indicated greater mobility of adsorbed molecules on the more homogeneous surface. Good correlations between K{MT)^ and ke have been demonstrated and, at constant temperature, a linear relation was observed between KM$ and the product, aTb, of polarizability and boiling-point TB. Gas-phase structure factors obtained by the procedure of Barrer & Gabor (1959) were considerably less than unity, indicating a dominant influence in each membrane of tortuosity and bottlenecks. For each membrane a linear relation has been demonstrated between the products KL and kB from which parameters associated with blind pore character have been obtained. Part III is concerned with the thermo-osmotic transport of the gases in the membranes. The nonisothermal flow is formulated in terms of the thermodynamics of irreversible processes and relations derived between the straight phenomenological coefficients of this treatment and the permeabilities and diffusion coefficients of part II. Equations are also presented relating the overall heat of transport, Q0, at temperature T0 to component heats of transport for the gas-phase flow (Qg, Q*) and extra flow (QB, Q*). In none of the systems studied did Q0 = — %RT0, the ideal value expected for a gas transported by molecular streaming (Knudsen flow). For He, H 2 and Ne in the Carbolac membranes, — ifiRT0 where /?, for a particular gas, is a constant < 1. With increasing sorbability of the flowing gas the temperature dependence of Q0 was progressively modified until, in the presence of substantial extra flow, — Q0 decreased strongly with increasing T0. Calculations of Qs and Q* are presented for the two limiting cases Q e— and Qg = 0. It is shown that Qs must always be negative and positive. A procedure for calculating isobaric permeabilities, utilizing a combination of thermo-osmotic steady-state and isothermal steady-state measurements, has been developed. For various pairs of gases, the ratios of isobaric permeabilities differed greatly from the corresponding ratios of isothermal permeabilities. Enhanced separations of sorbable mixtures by isobaric flow appear to be possible especially for the Graphon membrane.

A comparative structural study of cracking catalyst, porous glass, and carbon plugs by surface and volume flow of gases

1959 ◽  
Vol 251 (1266) ◽  
pp. 353-368 ◽  
Keyword(s):  
Steady Flow ◽  
Gas Phase ◽  
Surface Diffusion ◽  
Porous Glass ◽  
Diffusion Coefficients ◽  
Transient Flow ◽  
Time Lag ◽  
Surface Flow ◽  
Microporous Media ◽  
Pore Properties

Transient and steady states of volume and surface flow of gases and vapours in microporous media require for their description four different diffusion coefficients, namely, a surface and a gas-phase coefficient for transient and a surface and gas-phase coefficient for steady flow. The distinction between steady and transient flow arises in part because of the role of blind pores. Similarly, two different porosities ∊ and ∊ 8 and two different surface areas A and A 8 govern transient and steady-state flow respectively. By comparing the two gas-phase and the two surface diffusion coefficients with gas-phase and surface diffusion coefficients in a smooth cylindrical capillary having ∊/ A equal to that for the porous medium, four structure factors can be defined, in terms of which the pore properties of microporous media can be discussed. Data are presented for sorption, transient flow (time lag) and steady flow of He, Ne, A and N 2 in compressed alumina-silica catalyst plugs. These, and previously obtained data for Vycor porous glass (Barrer & Barrie 1952) and Carbolac carbon plugs (Barrer & Strachan 1955) have been analyzed according to the above procedure, and pore properties compared. In this way it was possible to obtain information regarding pore structure which could not have been derived by other methods.

Sorption and surface flow in graphitized carbon membranes - II. Time-lag and blind pore character

1968 ◽  
Vol 304 (1479) ◽  
pp. 407-425 ◽  
Keyword(s):  
Diffusion Coefficient ◽  
Time Dependence ◽  
General Expression ◽  
Diffusion Coefficients ◽  
General Equation ◽  
Time Lag ◽  
Surface Flow ◽  
Time Lags ◽  
Carbon Membranes ◽  
Graphitized Carbon

A general expression has been obtained for the time-lag in transport through membranes, based only on the conservation of mass condition and independent of any assumed equation of flow. When considered in relation to Fick’s equation the time-lag expression covers all situations in which diffusion coefficients, D , are functions of concentration, distance or time, or combinations of these variables. When D is a function only of concentration, C , two new ways have been given for exact treatments of the time-lag. These avoid difficulties which arise in using the formula originally given by Frisch (1957) and previously used in time-lag studies. Differences can arise between time-lags where D is a function only of C and the time lag L given by the general equation. These differences serve for the study of non-Fickian diffusions in which D is a function also of distance or time. This treatment, applied to a number of microporous membranes, leads to the conclusion that in these membranes non-Fickian components sometimes arise which are mostly dominated by time-dependence in the overall diffusion coefficient. It is shown how this behaviour can result from the partial blind-pore character of the channels in the membranes. In this and other ways the time-lag has been shown to give information about micropore systems which is not readily found from other measurements.

Pyrolysis of Methane to Higher Hydrocarbons: A Thermodynamic Study

1989 ◽  
Vol 42 (10) ◽  
pp. 1655 ◽  
Author(s):  
FP Larkins ◽  
AZ Khan
Keyword(s):  
Gas Phase ◽  
Pressure Range ◽  
Solid Carbon ◽  
Free Energies ◽  
Oxidation Of Methane ◽  
Conversion Of Methane ◽  
Equilibrium Conversion ◽  
Benzene Toluene ◽  
Higher Hydrocarbons ◽  
The Individual

Some basic thermodynamic parameters such as Gibbs free energies, enthalpies of reactions and equilibrium compositions of products from the pyrolysis and partial oxidation of methane to higher hydrocarbons in the gas phase have been determined within a consistent framework for the temperature range 800-1500 K and the pressure range 0.1-3 MPa , by using the CSIRO-SGTE THERMODATA system. It has been established that the pyrolysis of methane to higher hydrocarbons, e.g. acetylene, ethylene, ethane, prop-1-ene, propane, benzene, toluene, naphthalene, 1-methylnaphthalene and 2-methylnaphthalene, considered as separate reactions, is a highly endothermic reaction with the Gibbs free energies for the individual reactions being positive until 1300 K. The aromatics are thermodynamically most favoured with the equilibrium yields increasing with temperature. Addition of O2 lowers the heats of synthesis and the free energies for methane conversion but no enhancement in the equilibrium yields of hydrocarbons is observed. When solid carbon is allowed, it is the dominant product in all cases with the equilibrium yields for all hydrocarbons becoming negligible. Increasing the pressure at a particular temperature has more effect on the lowering of the equilibrium conversion of methane than on the suppression of solid carbon. Such data are valuable for understanding the conversion limits for methane into higher hydrocarbons.

Full Well Corrosion Insight – Case Studies in the Added Value of Electromagnetic Thickness Measurements During Well Interventions

2021 ◽  
Author(s):  
Andrew Imrie ◽  
Maciej Kozlowski ◽  
Omar Torky ◽  
Aditya Arie Wijaya
Keyword(s):  
Case Studies ◽  
Wall Thickness ◽  
Added Value ◽  
Metal Loss ◽  
Outer Diameter ◽  
Metal Thickness ◽  
True Condition ◽  
Pass Through ◽  
External Corrosion ◽  
The Individual

AbstractMonitoring pipe corrosion is one of the critical aspects in the well intervention. Such analysis is used to evaluate and justify any remedial actions, to prolong the longevity of the well. Typical corrosion evaluation methods of tubulars consist of multifinger caliper tools that provide high-resolution measurements of the internal condition of the pipe. Routinely, this data is then analyzed and interpreted with respect to the manufacture's nominal specification for each tubular. However, this requires assumptions on the outer diameter of the tubular may add uncertainty, and incorrectly calculate the true metal thicknesses. This paper will highlight cases where the integration of such tool and electromagnetic (EM) thickness data adds value in discovering the true condition of both the first tubular and outer casings.These case studies demonstrate the use of a multireceiver, multitransmitter electromagnetic (EM) metal thickness tool operating at multiple simultaneous frequencies. It is used to measure the individual wall thickness across multiple strings (up to five) and operates continuously, making measurements in the frequency domain. This tool was combined with a multifinger caliper to provide a complete and efficient single-trip diagnosis of the tubing and casing integrity. The combination of multifinger caliper and EM metal thickness tool results gives both internal and external corrosion as well as metal thickness of first and outer tubular strings.The paper highlights multiple case studies including; i) successfully detecting several areas of metal loss (up to greater than 32%) on the outer string, which correlated to areas of the mobile salt formation, ii) overlapping defects in two tubulars and, iii) cases where a multifinger caliper alone doesn't provide an accurate indication of the true wall thickness. The final case highlights the advantages of integrating multiple tubular integrity tools when determining the condition of the casing wall.Metal thickness tools operating on EM principles benefit from a slim outer diameter design that allows the tools to pass through restrictions which typically would prevent ultrasonic scanning thickness tools. Additionally, EM tools are unaffected by the type of fluid in the wellbore and not affected by any non-ferrous scale buildup that may present in the inside of the tubular wall. Combinability between complementary multifinger caliper technology and EM thickness results in two independent sensors to provide a complete assessment of the well architecture.

scholarly journals Development of the cardinality principle in Macedonian preschool children

Psihologija ◽  
2009 ◽  
Vol 42 (4) ◽  
pp. 459-475 ◽  
Author(s):  
Ana Nikoloska
Keyword(s):  
Preschool Children ◽  
Kindergarten Children ◽  
Pass Through ◽  
The Individual

Cardinality principle refers to the fact that the last number tag used in counting determines the cardinality of a set. Macedonian kindergarten children were tested with the give-a-number task for understanding of this principle. It was found that Macedonian children, unlike their western counterparts, pass through an additional stage, 5-knowers, before they master the cardinality principle. Also, the age at which they pass through the individual stages is somewhat higher than the age of children coming from western samples. Possible explanations are offered and discussed.

scholarly journals Seasonal changes of biological condition and reproductive cycle of hampback shrimp Pandalus hypsinotus (Caridea, Pandalidae) in the Tatar Strait

2021 ◽  
Vol 201 (3) ◽  
pp. 547-560
Author(s):  
D. N. Yuriev ◽  
G. V. Zhukovskaya
Keyword(s):  
Reproductive Cycle ◽  
Japan Sea ◽  
Biological Condition ◽  
Tatar Strait ◽  
Stage Of Development ◽  
Long Time ◽  
Pass Through ◽  
The Individual ◽  
Almost All ◽  
Trawl Catches

Research and commercial trawl catches of humpback shrimp Pandalus hypsinotus from the Tatar Strait (Japan Sea) in 2004–2020 were investigated, with bioanalysis of about 45 thousand specimens. Average timing of group molting, spawning, and eggs laying are determined, terms of gonads and eggs development are estimated. Prespawning and molting of the females occur between January-April, with the peaks in early February and middle February, respectively. All oviparous females have 30–40 days to lay eggs, and molt during 50–55 days; the peak of the eggs laying occurs in late June. The males molt in July-August, afterwards the largest individuals change gender and new intersexes are formed. The males have the second molting in October-December, with the peak in late November. In January, after finish of the males molting, a new annual reproduction cycle starts from the prespawning molting of females. Both vitellogenesis and embryogenesis are observed through the year, though females with developing gonads prevail from August to January (because of a long time span between winter and summer moltings while the egg carrying continued 15 months) but oviparous females — from February to July. The individual reproductive cycle of Pandalus hypsinotus in the Tatar Strait lasts 24 months, with 9 months of vitellogenesis (quick growth of gonads) and 15 months of embryogenesis. During the 2-year reproductive cycle, most of females pass through the following stages: i) gonads development (just after eggs laying) when almost all oviparous females (up to 95 % in May) have green gonads under carapace that corresponds to the stage of development «eggs laid — gonads weakly developed»; ii) summer molting from August when females lose hairs on pleopods and the gonads growth accelerates; iii) respawning in January-March (together with the firstly spawning intersexes, with slight delay of the latter); iv) initial developing of eggs during summer; v) stage of «eyed eggs» from December to March; and vi) eggs laying and molting from late March to late May; then the 2-year reproductive cycle repeats.

The Depressive Position in Normal Emotional Development

2016 ◽  
pp. 185-200
Author(s):  
Donald W. Winnicott
Keyword(s):  
Interpersonal Relationships ◽  
Emotional Development ◽  
Depressive Mood ◽  
Oedipus Complex ◽  
Depressive Position ◽  
Healthy Infants ◽  
Weaning Age ◽  
Inner World ◽  
Pass Through ◽  
The Individual

This paper is Winnicott’s account of the Depressive Position as a normal stage in the development of healthy infants, an achievement mostly belonging to the weaning age. It does not mean healthy infants pass through a stage of depression. Emotionally unhealthy, depersonalized babies lack the preconditions for this achievement. The mother holds the situation in time, so that the baby may experience ‘excited’ relationships and meet the consequences. Integration in the child’s mind of the split between the child-care environment and the exciting environment (the two aspects of mother) depends on good-enough mothering and the mother’s survival. The baby experiences this while the mother is holding the situation and the infant realizes that the ‘quiet’ mother was involved in the full tide of instinctual experience, and has survived. Instinctual experience brings anxiety and guilt but clinically children are sometimes without a sense of guilt, although they can go on to develop it. In the inner world of the individual who has achieved the depressive position there is on balance a reduced depressive mood and their reaction to loss is grief, or sadness. Where there is some degree of failure at the depressive position the result of loss is depression. The child who has reached the depressive position can get on with the problem of triangular interpersonal relationships: the classical Oedipus complex.

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